Stability assessment of a multi-port power electronic interface for hybrid micro-grid applications

NASA Astrophysics Data System (ADS)

Shamsi, Pourya

Migration to an industrial society increases the demand for electrical energy. Meanwhile, social causes for preserving the environment and reducing pollutions seek cleaner forms of energy sources. Therefore, there has been a growth in distributed generation from renewable sources in the past decade. Existing regulations and power system coordination does not allow for massive integration of distributed generation throughout the grid. Moreover, the current infrastructures are not designed for interfacing distributed and deregulated generation. In order to remedy this problem, a hybrid micro-grid based on nano-grids is introduced. This system consists of a reliable micro-grid structure that provides a smooth transition from the current distribution networks to smart micro-grid systems. Multi-port power electronic interfaces are introduced to manage the local generation, storage, and consumption. Afterwards, a model for this micro-grid is derived. Using this model, the stability of the system under a variety of source and load induced disturbances is studied. Moreover, pole-zero study of the micro-grid is performed under various loading conditions. An experimental setup of this micro-grid is developed, and the validity of the model in emulating the dynamic behavior of the system is verified. This study provides a theory for a novel hybrid micro-grid as well as models for stability assessment of the proposed micro-grid.

Establishment of key grid-connected performance index system for integrated PV-ES system

NASA Astrophysics Data System (ADS)

Li, Q.; Yuan, X. D.; Qi, Q.; Liu, H. M.

2016-08-01

In order to further promote integrated optimization operation of distributed new energy/ energy storage/ active load, this paper studies the integrated photovoltaic-energy storage (PV-ES) system which is connected with the distribution network, and analyzes typical structure and configuration selection for integrated PV-ES generation system. By combining practical grid- connected characteristics requirements and technology standard specification of photovoltaic generation system, this paper takes full account of energy storage system, and then proposes several new grid-connected performance indexes such as paralleled current sharing characteristic, parallel response consistency, adjusting characteristic, virtual moment of inertia characteristic, on- grid/off-grid switch characteristic, and so on. A comprehensive and feasible grid-connected performance index system is then established to support grid-connected performance testing on integrated PV-ES system.

Unlocking the potential of the smart grid

NASA Astrophysics Data System (ADS)

Konopko, Joanna

2015-12-01

The smart grid refers to describe a next-generation electrical power system that is typified by the increased use of Information and Communication Technologies (ICT) in the whole delivery electrical energy process. The generation, delivery and consumption energy, all the steps for power transmission and distribution make the smart grid a complex system. The question is if the amount, diversity, and uses of such data put the smart grid in the category of Big Data applications, followed by the natural question of what is the true value of such data. In this paper an initial answer to this question is provided, the current state of data generation of the Polish grid is analyzed, and a future realistic scenario is illustrated. The analysis shows that the amount of data generated in smart grid is comparable to some of Big Data system examples.

An algebraic homotopy method for generating quasi-three-dimensional grids for high-speed configurations

NASA Technical Reports Server (NTRS)

Moitra, Anutosh

1989-01-01

A fast and versatile procedure for algebraically generating boundary conforming computational grids for use with finite-volume Euler flow solvers is presented. A semi-analytic homotopic procedure is used to generate the grids. Grids generated in two-dimensional planes are stacked to produce quasi-three-dimensional grid systems. The body surface and outer boundary are described in terms of surface parameters. An interpolation scheme is used to blend between the body surface and the outer boundary in order to determine the field points. The method, albeit developed for analytically generated body geometries is equally applicable to other classes of geometries. The method can be used for both internal and external flow configurations, the only constraint being that the body geometries be specified in two-dimensional cross-sections stationed along the longitudinal axis of the configuration. Techniques for controlling various grid parameters, e.g., clustering and orthogonality are described. Techniques for treating problems arising in algebraic grid generation for geometries with sharp corners are addressed. A set of representative grid systems generated by this method is included. Results of flow computations using these grids are presented for validation of the effectiveness of the method.

Automatic Overset Grid Generation with Heuristic Feedback Control

NASA Technical Reports Server (NTRS)

Robinson, Peter I.

2001-01-01

An advancing front grid generation system for structured Overset grids is presented which automatically modifies Overset structured surface grids and control lines until user-specified grid qualities are achieved. The system is demonstrated on two examples: the first refines a space shuttle fuselage control line until global truncation error is achieved; the second advances, from control lines, the space shuttle orbiter fuselage top and fuselage side surface grids until proper overlap is achieved. Surface grids are generated in minutes for complex geometries. The system is implemented as a heuristic feedback control (HFC) expert system which iteratively modifies the input specifications for Overset control line and surface grids. It is developed as an extension of modern control theory, production rules systems and subsumption architectures. The methodology provides benefits over the full knowledge lifecycle of an expert system for knowledge acquisition, knowledge representation, and knowledge execution. The vector/matrix framework of modern control theory systematically acquires and represents expert system knowledge. Missing matrix elements imply missing expert knowledge. The execution of the expert system knowledge is performed through symbolic execution of the matrix algebra equations of modern control theory. The dot product operation of matrix algebra is generalized for heuristic symbolic terms. Constant time execution is guaranteed.

The eGo grid model: An open-source and open-data based synthetic medium-voltage grid model for distribution power supply systems

NASA Astrophysics Data System (ADS)

Amme, J.; Pleßmann, G.; Bühler, J.; Hülk, L.; Kötter, E.; Schwaegerl, P.

2018-02-01

The increasing integration of renewable energy into the electricity supply system creates new challenges for distribution grids. The planning and operation of distribution systems requires appropriate grid models that consider the heterogeneity of existing grids. In this paper, we describe a novel method to generate synthetic medium-voltage (MV) grids, which we applied in our DIstribution Network GeneratOr (DINGO). DINGO is open-source software and uses freely available data. Medium-voltage grid topologies are synthesized based on location and electricity demand in defined demand areas. For this purpose, we use GIS data containing demand areas with high-resolution spatial data on physical properties, land use, energy, and demography. The grid topology is treated as a capacitated vehicle routing problem (CVRP) combined with a local search metaheuristics. We also consider the current planning principles for MV distribution networks, paying special attention to line congestion and voltage limit violations. In the modelling process, we included power flow calculations for validation. The resulting grid model datasets contain 3608 synthetic MV grids in high resolution, covering all of Germany and taking local characteristics into account. We compared the modelled networks with real network data. In terms of number of transformers and total cable length, we conclude that the method presented in this paper generates realistic grids that could be used to implement a cost-optimised electrical energy system.

Noniterative three-dimensional grid generation using parabolic partial differential equations

NASA Technical Reports Server (NTRS)

Edwards, T. A.

1985-01-01

A new algorithm for generating three-dimensional grids has been developed and implemented which numerically solves a parabolic partial differential equation (PDE). The solution procedure marches outward in two coordinate directions, and requires inversion of a scalar tridiagonal system in the third. Source terms have been introduced to control the spacing and angle of grid lines near the grid boundaries, and to control the outer boundary point distribution. The method has been found to generate grids about 100 times faster than comparable grids generated via solution of elliptic PDEs, and produces smooth grids for finite-difference flow calculations.

Towards a Comprehensive Computational Simulation System for Turbomachinery

NASA Technical Reports Server (NTRS)

Shih, Ming-Hsin

1994-01-01

The objective of this work is to develop algorithms associated with a comprehensive computational simulation system for turbomachinery flow fields. This development is accomplished in a modular fashion. These modules includes grid generation, visualization, network, simulation, toolbox, and flow modules. An interactive grid generation module is customized to facilitate the grid generation process associated with complicated turbomachinery configurations. With its user-friendly graphical user interface, the user may interactively manipulate the default settings to obtain a quality grid within a fraction of time that is usually required for building a grid about the same geometry with a general-purpose grid generation code. Non-Uniform Rational B-Spline formulations are utilized in the algorithm to maintain geometry fidelity while redistributing grid points on the solid surfaces. Bezier curve formulation is used to allow interactive construction of inner boundaries. It is also utilized to allow interactive point distribution. Cascade surfaces are transformed from three-dimensional surfaces of revolution into two-dimensional parametric planes for easy manipulation. Such a transformation allows these manipulated plane grids to be mapped to surfaces of revolution by any generatrix definition. A sophisticated visualization module is developed to al-low visualization for both grid and flow solution, steady or unsteady. A network module is built to allow data transferring in the heterogeneous environment. A flow module is integrated into this system, using an existing turbomachinery flow code. A simulation module is developed to combine the network, flow, and visualization module to achieve near real-time flow simulation about turbomachinery geometries. A toolbox module is developed to support the overall task. A batch version of the grid generation module is developed to allow portability and has been extended to allow dynamic grid generation for pitch changing turbomachinery configurations. Various applications with different characteristics are presented to demonstrate the success of this system.

Computer Aided Grid Interface: An Interactive CFD Pre-Processor

NASA Technical Reports Server (NTRS)

Soni, Bharat K.

1997-01-01

NASA maintains an applications oriented computational fluid dynamics (CFD) efforts complementary to and in support of the aerodynamic-propulsion design and test activities. This is especially true at NASA/MSFC where the goal is to advance and optimize present and future liquid-fueled rocket engines. Numerical grid generation plays a significant role in the fluid flow simulations utilizing CFD. An overall goal of the current project was to develop a geometry-grid generation tool that will help engineers, scientists and CFD practitioners to analyze design problems involving complex geometries in a timely fashion. This goal is accomplished by developing the CAGI: Computer Aided Grid Interface system. The CAGI system is developed by integrating CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) geometric system output and/or Initial Graphics Exchange Specification (IGES) files (including all the NASA-IGES entities), geometry manipulations and generations associated with grid constructions, and robust grid generation methodologies. This report describes the development process of the CAGI system.

Computer Aided Grid Interface: An Interactive CFD Pre-Processor

NASA Technical Reports Server (NTRS)

Soni, Bharat K.

1996-01-01

NASA maintains an applications oriented computational fluid dynamics (CFD) efforts complementary to and in support of the aerodynamic-propulsion design and test activities. This is especially true at NASA/MSFC where the goal is to advance and optimize present and future liquid-fueled rocket engines. Numerical grid generation plays a significant role in the fluid flow simulations utilizing CFD. An overall goal of the current project was to develop a geometry-grid generation tool that will help engineers, scientists and CFD practitioners to analyze design problems involving complex geometries in a timely fashion. This goal is accomplished by developing the Computer Aided Grid Interface system (CAGI). The CAGI system is developed by integrating CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) geometric system output and / or Initial Graphics Exchange Specification (IGES) files (including all the NASA-IGES entities), geometry manipulations and generations associated with grid constructions, and robust grid generation methodologies. This report describes the development process of the CAGI system.

GENIE(++): A Multi-Block Structured Grid System

NASA Technical Reports Server (NTRS)

Williams, Tonya; Nadenthiran, Naren; Thornburg, Hugh; Soni, Bharat K.

1996-01-01

The computer code GENIE++ is a continuously evolving grid system containing a multitude of proven geometry/grid techniques. The generation process in GENIE++ is based on an earlier version. The process uses several techniques either separately or in combination to quickly and economically generate sculptured geometry descriptions and grids for arbitrary geometries. The computational mesh is formed by using an appropriate algebraic method. Grid clustering is accomplished with either exponential or hyperbolic tangent routines which allow the user to specify a desired point distribution. Grid smoothing can be accomplished by using an elliptic solver with proper forcing functions. B-spline and Non-Uniform Rational B-splines (NURBS) algorithms are used for surface definition and redistribution. The built in sculptured geometry definition with desired distribution of points, automatic Bezier curve/surface generation for interior boundaries/surfaces, and surface redistribution is based on NURBS. Weighted Lagrance/Hermite transfinite interpolation methods, interactive geometry/grid manipulation modules, and on-line graphical visualization of the generation process are salient features of this system which result in a significant time savings for a given geometry/grid application.

Smart grid technologies in local electric grids

NASA Astrophysics Data System (ADS)

Lezhniuk, Petro D.; Pijarski, Paweł; Buslavets, Olga A.

2017-08-01

The research is devoted to the creation of favorable conditions for the integration of renewable sources of energy into electric grids, which were designed to be supplied from centralized generation at large electric power stations. Development of distributed generation in electric grids influences the conditions of their operation - conflict of interests arises. The possibility of optimal functioning of electric grids and renewable sources of energy, when complex criterion of the optimality is balance reliability of electric energy in local electric system and minimum losses of electric energy in it. Multilevel automated system for power flows control in electric grids by means of change of distributed generation of power is developed. Optimization of power flows is performed by local systems of automatic control of small hydropower stations and, if possible, solar power plants.

Evaluation of the Dornier Gmbh interactive grid generation system

NASA Technical Reports Server (NTRS)

Brown, Robert L.

1989-01-01

An interactive grid generation program, INGRID, is investigated and evaluated. A description of the task and work performed, a description and evaluation of INGRID, and a discussion of the possibilities for bringing INGRID into the NASA and Numerical Aerodynamic Simulator (NAS) computing environments is included. The interactive grid generation program was found to be a viable approach for grid generation and determined that it could be converted to work in the NAS environment but that INGRID does not solve the fundamentally hard problems associated with grid generation, specifically, domain decomposition.

GridTool: A surface modeling and grid generation tool

NASA Technical Reports Server (NTRS)

Samareh-Abolhassani, Jamshid

1995-01-01

GridTool is designed around the concept that the surface grids are generated on a set of bi-linear patches. This type of grid generation is quite easy to implement, and it avoids the problems associated with complex CAD surface representations and associated surface parameterizations. However, the resulting surface grids are close to but not on the original CAD surfaces. This problem can be alleviated by projecting the resulting surface grids onto the original CAD surfaces. GridTool is designed primary for unstructured grid generation systems. Currently, GridTool supports VGRID and FELISA systems, and it can be easily extended to support other unstructured grid generation systems. The data in GridTool is stored parametrically so that once the problem is set up, one can modify the surfaces and the entire set of points, curves and patches will be updated automatically. This is very useful in a multidisciplinary design and optimization process. GridTool is written entirely in ANSI 'C', the interface is based on the FORMS library, and the graphics is based on the GL library. The code has been tested successfully on IRIS workstations running IRIX4.0 and above. The memory is allocated dynamically, therefore, memory size will depend on the complexity of geometry/grid. GridTool data structure is based on a link-list structure which allows the required memory to expand and contract dynamically according to the user's data size and action. Data structure contains several types of objects such as points, curves, patches, sources and surfaces. At any given time, there is always an active object which is drawn in magenta, or in their highlighted colors as defined by the resource file which will be discussed later.

Designing Wind and Solar Power Purchase Agreements to Support Grid Integration

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Neill, Barbara; Chernyakhovskiy, Ilya

Power purchase agreements (PPAs) represent one of many institutional tools that power systems can use to improve grid services from variable renewable energy (VRE) generators. This fact sheet introduces the concept of PPAs for VRE generators and provides a brief summary of key PPA components that can facilitate VRE generators to enhance grid stability and serve as a source of power system flexibility.

Geometry definition and grid generation for a complete fighter aircraft

NASA Technical Reports Server (NTRS)

Edwards, T. A.

1986-01-01

Recent advances in computing power and numerical solution procedures have enabled computational fluid dynamicists to attempt increasingly difficult problems. In particular, efforts are focusing on computations of complex three-dimensional flow fields about realistic aerodynamic bodies. To perform such computations, a very accurate and detailed description of the surface geometry must be provided, and a three-dimensional grid must be generated in the space around the body. The geometry must be supplied in a format compatible with the grid generation requirements, and must be verified to be free of inconsistencies. This paper presents a procedure for performing the geometry definition of a fighter aircraft that makes use of a commercial computer-aided design/computer-aided manufacturing system. Furthermore, visual representations of the geometry are generated using a computer graphics system for verification of the body definition. Finally, the three-dimensional grids for fighter-like aircraft are generated by means of an efficient new parabolic grid generation method. This method exhibits good control of grid quality.

Geometry definition and grid generation for a complete fighter aircraft

NASA Technical Reports Server (NTRS)

Edwards, Thomas A.

1986-01-01

Recent advances in computing power and numerical solution procedures have enabled computational fluid dynamicists to attempt increasingly difficult problems. In particular, efforts are focusing on computations of complex three-dimensional flow fields about realistic aerodynamic bodies. To perform such computations, a very accurate and detailed description of the surface geometry must be provided, and a three-dimensional grid must be generated in the space around the body. The geometry must be supplied in a format compatible with the grid generation requirements, and must be verified to be free of inconsistencies. A procedure for performing the geometry definition of a fighter aircraft that makes use of a commercial computer-aided design/computer-aided manufacturing system is presented. Furthermore, visual representations of the geometry are generated using a computer graphics system for verification of the body definition. Finally, the three-dimensional grids for fighter-like aircraft are generated by means of an efficient new parabolic grid generation method. This method exhibits good control of grid quality.

Design of energy storage system to improve inertial response for large scale PV generation

DOE PAGES

Wang, Xiaoyu; Yue, Meng

2016-07-01

With high-penetration levels of renewable generating sources being integrated into the existing electric power grid, conventional generators are being replaced and grid inertial response is deteriorating. This technical challenge is more severe with photovoltaic (PV) generation than with wind generation because PV generation systems cannot provide inertial response unless special countermeasures are adopted. To enhance the inertial response, this paper proposes to use battery energy storage systems (BESS) as the remediation approach to accommodate the degrading inertial response when high penetrations of PV generation are integrated into the existing power grid. A sample power system was adopted and simulated usingmore » PSS/E software. Here, impacts of different penetration levels of PV generation on the system inertial response were investigated and then BESS was incorporated to improve the frequency dynamics.« less

New Boundary Constraints for Elliptic Systems used in Grid Generation Problems

NASA Technical Reports Server (NTRS)

Kaul, Upender K.; Clancy, Daniel (Technical Monitor)

2002-01-01

This paper discusses new boundary constraints for elliptic partial differential equations as used in grid generation problems in generalized curvilinear coordinate systems. These constraints, based on the principle of local conservation of thermal energy in the vicinity of the boundaries, are derived using the Green's Theorem. They uniquely determine the so called decay parameters in the source terms of these elliptic systems. These constraints' are designed for boundary clustered grids where large gradients in physical quantities need to be resolved adequately. It is observed that the present formulation also works satisfactorily for mild clustering. Therefore, a closure for the decay parameter specification for elliptic grid generation problems has been provided resulting in a fully automated elliptic grid generation technique. Thus, there is no need for a parametric study of these decay parameters since the new constraints fix them uniquely. It is also shown that for Neumann type boundary conditions, these boundary constraints uniquely determine the solution to the internal elliptic problem thus eliminating the non-uniqueness of the solution of an internal Neumann boundary value grid generation problem.

Matrix Converter Interface for a Wind Energy Conversion System: Issues and Limitations

NASA Astrophysics Data System (ADS)

Patki, Chetan; Agarwal, Vivek

2009-08-01

Variable speed grid connected wind energy systems sometimes involve AC-AC power electronic interface between the generator and the grid. Matrix converter is an attractive option for such applications. Variable speed of the wind generator demands variable voltage variable frequency at the generator terminal. Matrix converter is used in this work to generate such a supply. Also, matrix converter can be appropriately controlled to compensate the grid for non-linear, reactive loads. However, any change of power factor on the grid side reflects on the voltage magnitude on the wind generator side. It is highlighted that this may contradict the maximum power point tracking control requirements. All the results of this work are presented.

User Manual for Beta Version of TURBO-GRD: A Software System for Interactive Two-Dimensional Boundary/ Field Grid Generation, Modification, and Refinement

NASA Technical Reports Server (NTRS)

Choo, Yung K.; Slater, John W.; Henderson, Todd L.; Bidwell, Colin S.; Braun, Donald C.; Chung, Joongkee

1998-01-01

TURBO-GRD is a software system for interactive two-dimensional boundary/field grid generation. modification, and refinement. Its features allow users to explicitly control grid quality locally and globally. The grid control can be achieved interactively by using control points that the user picks and moves on the workstation monitor or by direct stretching and refining. The techniques used in the code are the control point form of algebraic grid generation, a damped cubic spline for edge meshing and parametric mapping between physical and computational domains. It also performs elliptic grid smoothing and free-form boundary control for boundary geometry manipulation. Internal block boundaries are constructed and shaped by using Bezier curve. Because TURBO-GRD is a highly interactive code, users can read in an initial solution, display its solution contour in the background of the grid and control net, and exercise grid modification using the solution contour as a guide. This process can be called an interactive solution-adaptive grid generation.

A chimera grid scheme. [multiple overset body-conforming mesh system for finite difference adaptation to complex aircraft configurations

NASA Technical Reports Server (NTRS)

Steger, J. L.; Dougherty, F. C.; Benek, J. A.

1983-01-01

A mesh system composed of multiple overset body-conforming grids is described for adapting finite-difference procedures to complex aircraft configurations. In this so-called 'chimera mesh,' a major grid is generated about a main component of the configuration and overset minor grids are used to resolve all other features. Methods for connecting overset multiple grids and modifications of flow-simulation algorithms are discussed. Computational tests in two dimensions indicate that the use of multiple overset grids can simplify the task of grid generation without an adverse effect on flow-field algorithms and computer code complexity.

Elliptic surface grid generation on minimal and parmetrized surfaces

NASA Technical Reports Server (NTRS)

Spekreijse, S. P.; Nijhuis, G. H.; Boerstoel, J. W.

1995-01-01

An elliptic grid generation method is presented which generates excellent boundary conforming grids in domains in 2D physical space. The method is based on the composition of an algebraic and elliptic transformation. The composite mapping obeys the familiar Poisson grid generation system with control functions specified by the algebraic transformation. New expressions are given for the control functions. Grid orthogonality at the boundary is achieved by modification of the algebraic transformation. It is shown that grid generation on a minimal surface in 3D physical space is in fact equivalent to grid generation in a domain in 2D physical space. A second elliptic grid generation method is presented which generates excellent boundary conforming grids on smooth surfaces. It is assumed that the surfaces are parametrized and that the grid only depends on the shape of the surface and is independent of the parametrization. Concerning surface modeling, it is shown that bicubic Hermite interpolation is an excellent method to generate a smooth surface which is passing through a given discrete set of control points. In contrast to bicubic spline interpolation, there is extra freedom to model the tangent and twist vectors such that spurious oscillations are prevented.

Concentrated solar power plants impact on PV penetration level and grid flexibility under Egyptian climate

NASA Astrophysics Data System (ADS)

Moukhtar, Ibrahim; Elbaset, Adel A.; El Dein, Adel Z.; Qudaih, Yaser; Mitani, Yasunori

2018-05-01

Photovoltaic (PV) system integration in the electric grid has been increasing over the past decades. However, the impact of PV penetration on the electric grid, especially during the periods of higher and lower generation for the solar system at the middle of the day and during cloudy weather or at night respectively, limit the high penetration of solar PV system. In this research, a Concentrated Solar Power (CSP) with Thermal Energy Storage (TES) has been aggregated with PV system in order to accommodate the required electrical power during the higher and lower solar energy at all timescales. This paper analyzes the impacts of CSP on the grid-connected PV considering high penetration of PV system, particularly when no energy storages in the form of batteries are used. Two cases have been studied, the first when only PV system is integrated into the electric grid and the second when two types of solar energy (PV and CSP) are integrated. The System Advisor Model (SAM) software is used to simulate the output power of renewable energy. Simulation results show that the performance of CSP has a great impact on the penetration level of PV system and on the flexibility of the electric grid. The overall grid flexibility increases due to the ability of CSP to store and dispatch the generated power. In addition, CSP/TES itself has inherent flexibility. Therefore, CSP reduces the minimum generation constraint of the conventional generators that allows more penetration of the PV system.

Review of Strategies and Technologies for Demand-Side Management on Isolated Mini-Grids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harper, Meg

This review provides an overview of strategies and currently available technologies used for demandside management (DSM) on mini-grids throughout the world. For the purposes of this review, mini-grids are defined as village-scale electricity distribution systems powered by small local generation sources and not connected to a main grid.1 Mini-grids range in size from less than 1 kW to several hundred kW of installed generation capacity and may utilize different generation technologies, such as micro-hydro, biomass gasification, solar, wind, diesel generators, or a hybrid combination of any of these. This review will primarily refer to AC mini-grids, though much of themore » discussion could apply to DC grids as well. Many mini-grids include energy storage, though some rely solely on real-time generation.« less

TIGER: A graphically interactive grid system for turbomachinery applications

NASA Technical Reports Server (NTRS)

Shih, Ming-Hsin; Soni, Bharat K.

1992-01-01

Numerical grid generation algorithm associated with the flow field about turbomachinery geometries is presented. Graphical user interface is developed with FORMS Library to create an interactive, user-friendly working environment. This customized algorithm reduces the man-hours required to generate a grid associated with turbomachinery geometry, as compared to the use of general-purpose grid generation softwares. Bezier curves are utilized both interactively and automatically to accomplish grid line smoothness and orthogonality. Graphical User Interactions are provided in the algorithm, allowing the user to design and manipulate the grid lines with a mouse.

Forecasting Wind and Solar Generation: Improving System Operations, Greening the Grid (Spanish Version)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Tian; Chernyakhovskiy, Ilya; Brancucci Martinez-Anido, Carlo

This document is the Spanish version of 'Greening the Grid- Forecasting Wind and Solar Generation Improving System Operations'. It discusses improving system operations with forecasting with and solar generation. By integrating variable renewable energy (VRE) forecasts into system operations, power system operators can anticipate up- and down-ramps in VRE generation in order to cost-effectively balance load and generation in intra-day and day-ahead scheduling. This leads to reduced fuel costs, improved system reliability, and maximum use of renewable resources.

Grid generation on trimmed Bezier and NURBS quilted surfaces

NASA Technical Reports Server (NTRS)

Woan, Chung-Jin; Clever, Willard C.; Tam, Clement K.

1995-01-01

This paper presents some recently added capabilities to RAGGS, Rockwell Automated Grid Generation System. Included are the trimmed surface handling and display capability and structures and unstructured grid generation on trimmed Bezier and NURBS (non-uniform rational B-spline surfaces) quilted surfaces. Samples are given to demonstrate the new capabilities.

Dynamic analysis of combined photovoltaic source and synchronous generator connected to power grid

NASA Astrophysics Data System (ADS)

Mahabal, Divya

In the world of expanding economy and technology, the energy demand is likely to increase even with the global efforts of saving and increasing energy efficiency. Higher oil prices, effects of greenhouse gases, and concerns over other environmental impacts gave way to Distributed Generation (DG). With adequate awareness and support, DG's can meet these rising energy demands at lower prices compared to conventional methods. Extensive research is taking place in different areas like fuel cells, photovoltaic cells, wind turbines, and gas turbines. DG's when connected to a grid increase the overall efficiency of the power grid. It is believed that three-fifth of the world's electricity would account for renewable energy by middle of 21st century. This thesis presents the dynamic analysis of a grid connected photovoltaic (PV) system and synchronous generator. A grid is considered as an infinite bus. The photovol-taic system and synchronous generator act as small scale distributed energy resources. The output of the photovoltaic system depends on the light intensity, temperature, and irradiance levels of sun. The maximum power point tracking and DC/AC converter are also modeled for the photovoltaic system. The PV system is connected to the grid through DC/AC system. Different combinations of PV and synchronous generator are modeled with the grid to study the dynamics of the proposed system. The dynamics of the test system is analyzed by subjecting the system to several disturbances under various conditions. All modules are individually modeled and con-nected using MATLAB/Simulink software package. Results from the study show that, as the penetration of renewable energy sources like PV increases into the power system, the dynamics of the system becomes faster. When considering cases such as load switching, PV cannot deliver more power as the performance of PV depends on environmental conditions. Synchronous generator in power system can produce the required amount of power. As the main aim of this research is to use renewable sources like PV in the system, it is advantageous to use a combination of both PV and synchronous generator in the system.

Adaptive EAGLE dynamic solution adaptation and grid quality enhancement

NASA Technical Reports Server (NTRS)

Luong, Phu Vinh; Thompson, J. F.; Gatlin, B.; Mastin, C. W.; Kim, H. J.

1992-01-01

In the effort described here, the elliptic grid generation procedure in the EAGLE grid code was separated from the main code into a subroutine, and a new subroutine which evaluates several grid quality measures at each grid point was added. The elliptic grid routine can now be called, either by a computational fluid dynamics (CFD) code to generate a new adaptive grid based on flow variables and quality measures through multiple adaptation, or by the EAGLE main code to generate a grid based on quality measure variables through static adaptation. Arrays of flow variables can be read into the EAGLE grid code for use in static adaptation as well. These major changes in the EAGLE adaptive grid system make it easier to convert any CFD code that operates on a block-structured grid (or single-block grid) into a multiple adaptive code.

Two-boundary grid generation for the solution of the three dimensional compressible Navier-Stokes equations. Ph.D. Thesis - Old Dominion Univ.

NASA Technical Reports Server (NTRS)

Smith, R. E.

1981-01-01

A grid generation technique called the two boundary technique is developed and applied for the solution of the three dimensional Navier-Stokes equations. The Navier-Stokes equations are transformed from a cartesian coordinate system to a computational coordinate system, and the grid generation technique provides the Jacobian matrix describing the transformation. The two boundary technique is based on algebraically defining two distinct boundaries of a flow domain and the distribution of the grid is achieved by applying functions to the uniform computational grid which redistribute the computational independent variables and consequently concentrate or disperse the grid points in the physical domain. The Navier-Stokes equations are solved using a MacCormack time-split technique. Grids and supersonic laminar flow solutions are obtained for a family of three dimensional corners and two spike-nosed bodies.

Structured grid technology to enable flow simulation in an integrated system environment

NASA Astrophysics Data System (ADS)

Remotigue, Michael Gerard

An application-driven Computational Fluid Dynamics (CFD) environment needs flexible and general tools to effectively solve complex problems in a timely manner. In addition, reusable, portable, and maintainable specialized libraries will aid in rapidly developing integrated systems or procedures. The presented structured grid technology enables the flow simulation for complex geometries by addressing grid generation, grid decomposition/solver setup, solution, and interpretation. Grid generation is accomplished with the graphical, arbitrarily-connected, multi-block structured grid generation software system (GUM-B) developed and presented here. GUM-B is an integrated system comprised of specialized libraries for the graphical user interface and graphical display coupled with a solid-modeling data structure that utilizes a structured grid generation library and a geometric library based on Non-Uniform Rational B-Splines (NURBS). A presented modification of the solid-modeling data structure provides the capability for arbitrarily-connected regions between the grid blocks. The presented grid generation library provides algorithms that are reliable and accurate. GUM-B has been utilized to generate numerous structured grids for complex geometries in hydrodynamics, propulsors, and aerodynamics. The versatility of the libraries that compose GUM-B is also displayed in a prototype to automatically regenerate a grid for a free-surface solution. Grid decomposition and solver setup is accomplished with the graphical grid manipulation and repartition software system (GUMBO) developed and presented here. GUMBO is an integrated system comprised of specialized libraries for the graphical user interface and graphical display coupled with a structured grid-tools library. The described functions within the grid-tools library reduce the possibility of human error during decomposition and setup for the numerical solver by accounting for boundary conditions and connectivity. GUMBO is linked with a flow solver interface, to the parallel UNCLE code, to provide load balancing tools and solver setup. Weeks of boundary condition and connectivity specification and validation has been reduced to hours. The UNCLE flow solver is utilized for the solution of the flow field. To accelerate convergence toward a quick engineering answer, a full multigrid (FMG) approach coupled with UNCLE, which is a full approximation scheme (FAS), is presented. The prolongation operators used in the FMG-FAS method are compared. The procedure is demonstrated on a marine propeller in incompressible flow. Interpretation of the solution is accomplished by vortex feature detection. Regions of "Intrinsic Swirl" are located by interrogating the velocity gradient tensor for complex eigenvalues. The "Intrinsic Swirl" parameter is visualized on a solution of a marine propeller to determine if any vortical features are captured. The libraries and the structured grid technology presented herein are flexible and general enough to tackle a variety of complex applications. This technology has significantly enabled the capability of the ERC personnel to effectively calculate solutions for complex geometries.

Transient Control of Synchronous Machine Active and Reactive Power in Micro-grid Power Systems

NASA Astrophysics Data System (ADS)

Weber, Luke G.

There are two main topics associated with this dissertation. The first is to investigate phase-to-neutral fault current magnitude occurring in generators with multiple zero-sequence current sources. The second is to design, model, and tune a linear control system for operating a micro-grid in the event of a separation from the electric power system. In the former case, detailed generator, AC8B excitation system, and four-wire electric power system models are constructed. Where available, manufacturers data is used to validate the generator and exciter models. A gain-delay with frequency droop control is used to model an internal combustion engine and governor. The four wire system is connected through a transformer impedance to an infinite bus. Phase-to-neutral faults are imposed on the system, and fault magnitudes analyzed against three-phase faults to gauge their severity. In the latter case, a balanced three-phase system is assumed. The model structure from the former case - but using data for a different generator - is incorporated with a model for an energy storage device and a net load model to form a micro-grid. The primary control model for the energy storage device has a high level of detail, as does the energy storage device plant model in describing the LC filter and transformer. A gain-delay battery and inverter model is used at the front end. The net load model is intended to be the difference between renewable energy sources and load within a micro-grid system that has separated from the grid. Given the variability of both renewable generation and load, frequency and voltage stability are not guaranteed. This work is an attempt to model components of a proposed micro-grid system at the University of Wisconsin Milwaukee, and design, model, and tune a linear control system for operation in the event of a separation from the electric power system. The control module is responsible for management of frequency and active power, and voltage and reactive power. The scope of this work is to • develop a mathematical model for a salient pole, 2 damper winding synchronous generator with d axis saturation suitable for transient analysis, • develop a mathematical model for a voltage regulator and excitation system using the IEEE AC8B voltage regulator and excitation system template, • develop mathematical models for an energy storage primary control system, LC filter and transformer suitable for transient analysis, • combine the generator and energy storage models in a micro-grid context, • develop mathematical models for electric system components in the stationary abc frame and rotating dq reference frame, • develop a secondary control network for dispatch of micro-grid assets, • establish micro-grid limits of stable operation for step changes in load and power commands based on simulations of model data assuming net load on the micro-grid, and • use generator and electric system models to assess the generator current magnitude during phase-to-ground faults.

Generating grids directly on CAD database surfaces using a parametric evaluator approach

NASA Technical Reports Server (NTRS)

Gatzhe, Timothy D.; Melson, Thomas G.

1995-01-01

A very important, but often overlooked step in grid generation is acquiring a suitable geometry definition of the vehicle to be analyzed. In the past, geometry was usually obtained by generating a number of cross-sections of each component. A number of recent efforts have focussed on non-uniform rational B-spline surfaces (NURBS) to provide as single type of analytic surface to deal with inside the grid generator. This approach has required the development of tools to read other types of surfaces and convert them, either exactly or by approximation, into a NURBS surface. This paper describes a more generic parametric evaluator approach, which does not rely on a particular surface type internal to the grid generation system and is less restrictive in the number of surface types that can be represented exactly. This approach has been implemented in the McDonnell Douglas grid generation system, MACGS, and offers direct access to all types of surfaces from a Unigraphics part file.

Maximum capacity model of grid-connected multi-wind farms considering static security constraints in electrical grids

NASA Astrophysics Data System (ADS)

Zhou, W.; Qiu, G. Y.; Oodo, S. O.; He, H.

2013-03-01

An increasing interest in wind energy and the advance of related technologies have increased the connection of wind power generation into electrical grids. This paper proposes an optimization model for determining the maximum capacity of wind farms in a power system. In this model, generator power output limits, voltage limits and thermal limits of branches in the grid system were considered in order to limit the steady-state security influence of wind generators on the power system. The optimization model was solved by a nonlinear primal-dual interior-point method. An IEEE-30 bus system with two wind farms was tested through simulation studies, plus an analysis conducted to verify the effectiveness of the proposed model. The results indicated that the model is efficient and reasonable.

The three-dimensional Multi-Block Advanced Grid Generation System (3DMAGGS)

NASA Technical Reports Server (NTRS)

Alter, Stephen J.; Weilmuenster, Kenneth J.

1993-01-01

As the size and complexity of three dimensional volume grids increases, there is a growing need for fast and efficient 3D volumetric elliptic grid solvers. Present day solvers are limited by computational speed and do not have all the capabilities such as interior volume grid clustering control, viscous grid clustering at the wall of a configuration, truncation error limiters, and convergence optimization residing in one code. A new volume grid generator, 3DMAGGS (Three-Dimensional Multi-Block Advanced Grid Generation System), which is based on the 3DGRAPE code, has evolved to meet these needs. This is a manual for the usage of 3DMAGGS and contains five sections, including the motivations and usage, a GRIDGEN interface, a grid quality analysis tool, a sample case for verifying correct operation of the code, and a comparison to both 3DGRAPE and GRIDGEN3D. Since it was derived from 3DGRAPE, this technical memorandum should be used in conjunction with the 3DGRAPE manual (NASA TM-102224).

A grid generation system for multi-disciplinary design optimization

NASA Technical Reports Server (NTRS)

Jones, William T.; Samareh-Abolhassani, Jamshid

1995-01-01

A general multi-block three-dimensional volume grid generator is presented which is suitable for Multi-Disciplinary Design Optimization. The code is timely, robust, highly automated, and written in ANSI 'C' for platform independence. Algebraic techniques are used to generate and/or modify block face and volume grids to reflect geometric changes resulting from design optimization. Volume grids are generated/modified in a batch environment and controlled via an ASCII user input deck. This allows the code to be incorporated directly into the design loop. Generated volume grids are presented for a High Speed Civil Transport (HSCT) Wing/Body geometry as well a complex HSCT configuration including horizontal and vertical tails, engine nacelles and pylons, and canard surfaces.

Three-dimensional hybrid grid generation using advancing front techniques

NASA Technical Reports Server (NTRS)

Steinbrenner, John P.; Noack, Ralph W.

1995-01-01

A new 3-dimensional hybrid grid generation technique has been developed, based on ideas of advancing fronts for both structured and unstructured grids. In this approach, structured grids are first generate independently around individual components of the geometry. Fronts are initialized on these structure grids, and advanced outward so that new cells are extracted directly from the structured grids. Employing typical advancing front techniques, cells are rejected if they intersect the existing front or fail other criteria When no more viable structured cells exist further cells are advanced in an unstructured manner to close off the overall domain, resulting in a grid of 'hybrid' form. There are two primary advantages to the hybrid formulation. First, generating blocks with limited regard to topology eliminates the bottleneck encountered when a multiple block system is used to fully encapsulate a domain. Individual blocks may be generated free of external constraints, which will significantly reduce the generation time. Secondly, grid points near the body (presumably with high aspect ratio) will still maintain a structured (non-triangular or tetrahedral) character, thereby maximizing grid quality and solution accuracy near the surface.

Data Grid Management Systems

NASA Technical Reports Server (NTRS)

Moore, Reagan W.; Jagatheesan, Arun; Rajasekar, Arcot; Wan, Michael; Schroeder, Wayne

2004-01-01

The "Grid" is an emerging infrastructure for coordinating access across autonomous organizations to distributed, heterogeneous computation and data resources. Data grids are being built around the world as the next generation data handling systems for sharing, publishing, and preserving data residing on storage systems located in multiple administrative domains. A data grid provides logical namespaces for users, digital entities and storage resources to create persistent identifiers for controlling access, enabling discovery, and managing wide area latencies. This paper introduces data grids and describes data grid use cases. The relevance of data grids to digital libraries and persistent archives is demonstrated, and research issues in data grids and grid dataflow management systems are discussed.

Investigation of Advanced Counterrotation Blade Configuration Concepts for High Speed Turboprop Systems. Task 3: Advanced Fan Section Grid Generator Final Report and Computer Program User's Manual

NASA Technical Reports Server (NTRS)

Crook, Andrew J.; Delaney, Robert A.

1991-01-01

A procedure is studied for generating three-dimensional grids for advanced turbofan engine fan section geometries. The procedure constructs a discrete mesh about engine sections containing the fan stage, an arbitrary number of axisymmetric radial flow splitters, a booster stage, and a bifurcated core/bypass flow duct with guide vanes. The mesh is an h-type grid system, the points being distributed with a transfinite interpolation scheme with axial and radial spacing being user specified. Elliptic smoothing of the grid in the meridional plane is a post-process option. The grid generation scheme is consistent with aerodynamic analyses utilizing the average-passage equation system developed by Dr. John Adamczyk of NASA Lewis. This flow solution scheme requires a series of blade specific grids each having a common axisymmetric mesh, but varying in the circumferential direction according to the geometry of the specific blade row.

Enhanced Product Generation at NASA Data Centers Through Grid Technology

NASA Technical Reports Server (NTRS)

Barkstrom, Bruce R.; Hinke, Thomas H.; Gavali, Shradha; Seufzer, William J.

2003-01-01

This paper describes how grid technology can support the ability of NASA data centers to provide customized data products. A combination of grid technology and commodity processors are proposed to provide the bandwidth necessary to perform customized processing of data, with customized data subsetting providing the initial example. This customized subsetting engine can be used to support a new type of subsetting, called phenomena-based subsetting, where data is subsetted based on its association with some phenomena, such as mesoscale convective systems or hurricanes. This concept is expanded to allow the phenomena to be detected in one type of data, with the subsetting requirements transmitted to the subsetting engine to subset a different type of data. The subsetting requirements are generated by a data mining system and transmitted to the subsetter in the form of an XML feature index that describes the spatial and temporal extent of the phenomena. For this work, a grid-based mining system called the Grid Miner is used to identify the phenomena and generate the feature index. This paper discusses the value of grid technology in facilitating the development of a high performance customized product processing and the coupling of a grid mining system to support phenomena-based subsetting.

TIGER: A user-friendly interactive grid generation system for complicated turbomachinery and axis-symmetric configurations

NASA Technical Reports Server (NTRS)

Shih, Ming H.; Soni, Bharat K.

1993-01-01

The issue of time efficiency in grid generation is addressed by developing a user friendly graphical interface for interactive/automatic construction of structured grids around complex turbomachinery/axis-symmetric configurations. The accuracy of geometry modeling and its fidelity is accomplished by adapting the nonuniform rational b-spline (NURBS) representation. A customized interactive grid generation code, TIGER, has been developed to facilitate the grid generation process for complicated internal, external, and internal-external turbomachinery fields simulations. The FORMS Library is utilized to build user-friendly graphical interface. The algorithm allows a user to redistribute grid points interactively on curves/surfaces using NURBS formulation with accurate geometric definition. TIGER's features include multiblock, multiduct/shroud, multiblade row, uneven blade count, and patched/overlapping block interfaces. It has been applied to generate grids for various complicated turbomachinery geometries, as well as rocket and missile configurations.

TIGER: Turbomachinery interactive grid generation

NASA Technical Reports Server (NTRS)

Soni, Bharat K.; Shih, Ming-Hsin; Janus, J. Mark

1992-01-01

A three dimensional, interactive grid generation code, TIGER, is being developed for analysis of flows around ducted or unducted propellers. TIGER is a customized grid generator that combines new technology with methods from general grid generation codes. The code generates multiple block, structured grids around multiple blade rows with a hub and shroud for either C grid or H grid topologies. The code is intended for use with a Euler/Navier-Stokes solver also being developed, but is general enough for use with other flow solvers. TIGER features a silicon graphics interactive graphics environment that displays a pop-up window, graphics window, and text window. The geometry is read as a discrete set of points with options for several industrial standard formats and NASA standard formats. Various splines are available for defining the surface geometries. Grid generation is done either interactively or through a batch mode operation using history files from a previously generated grid. The batch mode operation can be done either with a graphical display of the interactive session or with no graphics so that the code can be run on another computer system. Run time can be significantly reduced by running on a Cray-YMP.

Micro-grid platform based on NODE.JS architecture, implemented in electrical network instrumentation

NASA Astrophysics Data System (ADS)

Duque, M.; Cando, E.; Aguinaga, A.; Llulluna, F.; Jara, N.; Moreno, T.

2016-05-01

In this document, I propose a theory about the impact of systems based on microgrids in non-industrialized countries that have the goal to improve energy exploitation through alternatives methods of a clean and renewable energy generation and the creation of the app to manage the behavior of the micro-grids based on the NodeJS, Django and IOJS technologies. The micro-grids allow the optimal way to manage energy flow by electric injection directly in electric network small urban's cells in a low cost and available way. In difference from conventional systems, micro-grids can communicate between them to carry energy to places that have higher demand in accurate moments. This system does not require energy storage, so, costs are lower than conventional systems like fuel cells, solar panels or else; even though micro-grids are independent systems, they are not isolated. The impact that this analysis will generate, is the improvement of the electrical network without having greater control than an intelligent network (SMART-GRID); this leads to move to a 20% increase in energy use in a specified network; that suggest there are others sources of energy generation; but for today's needs, we need to standardize methods and remain in place to support all future technologies and the best option are the Smart Grids and Micro-Grids.

Global renewable energy-based electricity generation and smart grid system for energy security.

PubMed

Islam, M A; Hasanuzzaman, M; Rahim, N A; Nahar, A; Hosenuzzaman, M

2014-01-01

Energy is an indispensable factor for the economic growth and development of a country. Energy consumption is rapidly increasing worldwide. To fulfill this energy demand, alternative energy sources and efficient utilization are being explored. Various sources of renewable energy and their efficient utilization are comprehensively reviewed and presented in this paper. Also the trend in research and development for the technological advancement of energy utilization and smart grid system for future energy security is presented. Results show that renewable energy resources are becoming more prevalent as more electricity generation becomes necessary and could provide half of the total energy demands by 2050. To satisfy the future energy demand, the smart grid system can be used as an efficient system for energy security. The smart grid also delivers significant environmental benefits by conservation and renewable generation integration.

Global Renewable Energy-Based Electricity Generation and Smart Grid System for Energy Security

PubMed Central

Islam, M. A.; Hasanuzzaman, M.; Rahim, N. A.; Nahar, A.; Hosenuzzaman, M.

2014-01-01

Energy is an indispensable factor for the economic growth and development of a country. Energy consumption is rapidly increasing worldwide. To fulfill this energy demand, alternative energy sources and efficient utilization are being explored. Various sources of renewable energy and their efficient utilization are comprehensively reviewed and presented in this paper. Also the trend in research and development for the technological advancement of energy utilization and smart grid system for future energy security is presented. Results show that renewable energy resources are becoming more prevalent as more electricity generation becomes necessary and could provide half of the total energy demands by 2050. To satisfy the future energy demand, the smart grid system can be used as an efficient system for energy security. The smart grid also delivers significant environmental benefits by conservation and renewable generation integration. PMID:25243201

Active power control of solar PV generation for large interconnection frequency regulation and oscillation damping

DOE PAGES

Liu, Yong; Zhu, Lin; Zhan, Lingwei; ...

2015-06-23

Because of zero greenhouse gas emission and decreased manufacture cost, solar photovoltaic (PV) generation is expected to account for a significant portion of future power grid generation portfolio. Because it is indirectly connected to the power grid via power electronic devices, solar PV generation system is fully decoupled from the power grid, which will influence the interconnected power grid dynamic characteristics as a result. In this study, the impact of solar PV penetration on large interconnected power system frequency response and inter-area oscillation is evaluated, taking the United States Eastern Interconnection (EI) as an example. Furthermore, based on the constructedmore » solar PV electrical control model with additional active power control loops, the potential contributions of solar PV generation to power system frequency regulation and oscillation damping are examined. The advantages of solar PV frequency support over that of wind generator are also discussed. Finally, simulation results demonstrate that solar PV generations can effectively work as ‘actuators’ in alleviating the negative impacts they bring about.« less

Transformation of two and three-dimensional regions by elliptic systems

NASA Technical Reports Server (NTRS)

Mastin, C. Wayne

1994-01-01

Several reports are attached to this document which contain the results of our research at the end of this contract period. Three of the reports deal with our work on generating surface grids. One is a preprint of a paper which will appear in the journal Applied Mathematics and Computation. Another is the abstract from a dissertation which has been prepared by Ahmed Khamayseh, a graduate student who has been supported by this grant for the last two years. The last report on surface grids is the extended abstract of a paper to be presented at the 14th IMACS World Congress in July. This report contains results on conformal mappings of surfaces, which are closely related to elliptic methods for surface grid generation. A preliminary report is included on new methods for dealing with block interfaces in multiblock grid systems. The development work is complete and the methods will eventually be incorporated into the National Grid Project (NGP) grid generation code. Thus, the attached report contains only a simple grid system which was used to test the algorithms to prove that the concepts are sound. These developments will greatly aid grid control when using elliptic systems and prevent unwanted grid movement. The last report is a brief summary of some timings that were obtained when the multiblock grid generation code was run on the Intel IPSC/860 hypercube. Since most of the data in a grid code is local to a particular block, only a small fraction of the total data must be passed between processors. The data is also distributed among the processors so that the total size of the grid can be increase along with the number of processors. This work is only in a preliminary stage. However, one of the ERC graduate students has taken an interest in the project and is presently extending these results as a part of his master's thesis.

Models for the modern power grid

NASA Astrophysics Data System (ADS)

Nardelli, Pedro H. J.; Rubido, Nicolas; Wang, Chengwei; Baptista, Murilo S.; Pomalaza-Raez, Carlos; Cardieri, Paulo; Latva-aho, Matti

2014-10-01

This article reviews different kinds of models for the electric power grid that can be used to understand the modern power system, the smart grid. From the physical network to abstract energy markets, we identify in the literature different aspects that co-determine the spatio-temporal multilayer dynamics of power system. We start our review by showing how the generation, transmission and distribution characteristics of the traditional power grids are already subject to complex behaviour appearing as a result of the the interplay between dynamics of the nodes and topology, namely synchronisation and cascade effects. When dealing with smart grids, the system complexity increases even more: on top of the physical network of power lines and controllable sources of electricity, the modernisation brings information networks, renewable intermittent generation, market liberalisation, prosumers, among other aspects. In this case, we forecast a dynamical co-evolution of the smart grid and other kind of networked systems that cannot be understood isolated. This review compiles recent results that model electric power grids as complex systems, going beyond pure technological aspects. From this perspective, we then indicate possible ways to incorporate the diverse co-evolving systems into the smart grid model using, for example, network theory and multi-agent simulation.

Smart grid integration of small-scale trigeneration systems

NASA Astrophysics Data System (ADS)

Vacheva, Gergana; Kanchev, Hristiyan; Hinov, Nikolay

2017-12-01

This paper presents a study on the possibilities for implementation of local heating, air-conditioning and electricity generation (trigeneration) as distributed energy resource in the Smart Grid. By the means of microturbine-based generators and absorption chillers buildings are able to meet partially or entirely their electrical load curve or even supply power to the grid by following their heating and air-conditioning daily schedule. The principles of small-scale cooling, heating and power generation systems are presented at first, then the thermal calculations of an example building are performed: the heat losses due to thermal conductivity and the estimated daily heating and air-conditioning load curves. By considering daily power consumption curves and weather data for several winter and summer days, the heating/air-conditioning schedule is estimated and the available electrical energy from a microturbine-based cogeneration system is estimated. Simulation results confirm the potential of using cogeneration and trigeneration systems for local distributed electricity generation and grid support in the daily peaks of power consumption.

Energy Management and Optimization Methods for Grid Energy Storage Systems

DOE PAGES

Byrne, Raymond H.; Nguyen, Tu A.; Copp, David A.; ...

2017-08-24

Today, the stability of the electric power grid is maintained through real time balancing of generation and demand. Grid scale energy storage systems are increasingly being deployed to provide grid operators the flexibility needed to maintain this balance. Energy storage also imparts resiliency and robustness to the grid infrastructure. Over the last few years, there has been a significant increase in the deployment of large scale energy storage systems. This growth has been driven by improvements in the cost and performance of energy storage technologies and the need to accommodate distributed generation, as well as incentives and government mandates. Energymore » management systems (EMSs) and optimization methods are required to effectively and safely utilize energy storage as a flexible grid asset that can provide multiple grid services. The EMS needs to be able to accommodate a variety of use cases and regulatory environments. In this paper, we provide a brief history of grid-scale energy storage, an overview of EMS architectures, and a summary of the leading applications for storage. These serve as a foundation for a discussion of EMS optimization methods and design.« less

Energy Management and Optimization Methods for Grid Energy Storage Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byrne, Raymond H.; Nguyen, Tu A.; Copp, David A.

Today, the stability of the electric power grid is maintained through real time balancing of generation and demand. Grid scale energy storage systems are increasingly being deployed to provide grid operators the flexibility needed to maintain this balance. Energy storage also imparts resiliency and robustness to the grid infrastructure. Over the last few years, there has been a significant increase in the deployment of large scale energy storage systems. This growth has been driven by improvements in the cost and performance of energy storage technologies and the need to accommodate distributed generation, as well as incentives and government mandates. Energymore » management systems (EMSs) and optimization methods are required to effectively and safely utilize energy storage as a flexible grid asset that can provide multiple grid services. The EMS needs to be able to accommodate a variety of use cases and regulatory environments. In this paper, we provide a brief history of grid-scale energy storage, an overview of EMS architectures, and a summary of the leading applications for storage. These serve as a foundation for a discussion of EMS optimization methods and design.« less

Computing Aerodynamic Performance of a 2D Iced Airfoil: Blocking Topology and Grid Generation

NASA Technical Reports Server (NTRS)

Chi, X.; Zhu, B.; Shih, T. I.-P.; Slater, J. W.; Addy, H. E.; Choo, Yung K.; Lee, Chi-Ming (Technical Monitor)

2002-01-01

The ice accrued on airfoils can have enormously complicated shapes with multiple protruded horns and feathers. In this paper, several blocking topologies are proposed and evaluated on their ability to produce high-quality structured multi-block grid systems. A transition layer grid is introduced to ensure that jaggedness on the ice-surface geometry do not to propagate into the domain. This is important for grid-generation methods based on hyperbolic PDEs (Partial Differential Equations) and algebraic transfinite interpolation. A 'thick' wrap-around grid is introduced to ensure that grid lines clustered next to solid walls do not propagate as streaks of tightly packed grid lines into the interior of the domain along block boundaries. For ice shapes that are not too complicated, a method is presented for generating high-quality single-block grids. To demonstrate the usefulness of the methods developed, grids and CFD solutions were generated for two iced airfoils: the NLF0414 airfoil with and without the 623-ice shape and the B575/767 airfoil with and without the 145m-ice shape. To validate the computations, the computed lift coefficients as a function of angle of attack were compared with available experimental data. The ice shapes and the blocking topologies were prepared by NASA Glenn's SmaggIce software. The grid systems were generated by using a four-boundary method based on Hermite interpolation with controls on clustering, orthogonality next to walls, and C continuity across block boundaries. The flow was modeled by the ensemble-averaged compressible Navier-Stokes equations, closed by the shear-stress transport turbulence model in which the integration is to the wall. All solutions were generated by using the NPARC WIND code.

Transformation of two and three-dimensional regions by elliptic systems

NASA Technical Reports Server (NTRS)

Mastin, C. Wayne

1991-01-01

A reliable linear system is presented for grid generation in 2-D and 3-D. The method is robust in the sense that convergence is guaranteed but is not as reliable as other nonlinear elliptic methods in generating nonfolding grids. The construction of nonfolding grids depends on having reasonable approximations of cell aspect ratios and an appropriate distribution of grid points on the boundary of the region. Some guidelines are included on approximating the aspect ratios, but little help is offered on setting up the boundary grid other than to say that in 2-D the boundary correspondence should be close to that generated by a conformal mapping. It is assumed that the functions which control the grid distribution depend only on the computational variables and not on the physical variables. Whether this is actually the case depends on how the grid is constructed. In a dynamic adaptive procedure where the grid is constructed in the process of solving a fluid flow problem, the grid is usually updated at fixed iteration counts using the current value of the control function. Since the control function is not being updated during the iteration of the grid equations, the grid construction is a linear procedure. However, in the case of a static adaptive procedure where a trial solution is computed and used to construct an adaptive grid, the control functions may be recomputed at every step of the grid iteration.

An Analysis of Elliptic Grid Generation Techniques Using an Implicit Euler Solver.

DTIC Science & Technology

1986-06-09

automatic determination of the control fu.nction, . elements of covariant metric tensor in the elliptic grid generation system , from the Cm = 1,2,3...computational fluid d’nan1-cs code. Tne code Inclues a tnree-dimensional current research is aimed primaril: at algebraic generation system based on transfinite...start the iterative solution of the f. ow, nea, transfer, and combustion proble:s. elliptic generation system . Tn13 feature also .:ven-.ts :.t be made

Research on Experiment of Islanding Protection Device of Grid-connected Photovoltaic System Based on RTDS

NASA Astrophysics Data System (ADS)

Zhou, Ning; Yang, Jia; Cheng, Zheng; Chen, Bo; Su, Yong Chun; Shu, Zhan; Zou, Jin

2017-06-01

Solar photovoltaic power generation is the power generation using solar cell module converting sunlight into DC electric energy. In the paper an equivalent model of solar photovoltaic power generation system is built in RTDS. The main circuit structure of the two-stage PV grid-connected system consists of the DC-DC, DC-AC circuit. The MPPT (Maximum Power Point Tracking) control of the PV array is controlled by adjusting the duty ratio of the DC-DC circuit. The proposed control strategy of constant voltage/constant reactive power (V/Q) control is successfully implemented grid-connected control of the inverter when grid-connected operation. The closed-loop experiment of islanding protection device of photovoltaic power plant on RTDS, verifies the correctness of the simulation model, and the experimental verification can be applied to this type of device.

Power system observability and dynamic state estimation for stability monitoring using synchrophasor measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Kai; Qi, Junjian; Kang, Wei

2016-08-01

Growing penetration of intermittent resources such as renewable generations increases the risk of instability in a power grid. This paper introduces the concept of observability and its computational algorithms for a power grid monitored by the wide-area measurement system (WAMS) based on synchrophasors, e.g. phasor measurement units (PMUs). The goal is to estimate real-time states of generators, especially for potentially unstable trajectories, the information that is critical for the detection of rotor angle instability of the grid. The paper studies the number and siting of synchrophasors in a power grid so that the state of the system can be accuratelymore » estimated in the presence of instability. An unscented Kalman filter (UKF) is adopted as a tool to estimate the dynamic states that are not directly measured by synchrophasors. The theory and its computational algorithms are illustrated in detail by using a 9-bus 3-generator power system model and then tested on a 140-bus 48-generator Northeast Power Coordinating Council power grid model. Case studies on those two systems demonstrate the performance of the proposed approach using a limited number of synchrophasors for dynamic state estimation for stability assessment and its robustness against moderate inaccuracies in model parameters.« less

Models for the transient stability of conventional power generating stations connected to low inertia systems

NASA Astrophysics Data System (ADS)

Zarifakis, Marios; Coffey, William T.; Kalmykov, Yuri P.; Titov, Sergei V.

2017-06-01

An ever-increasing requirement to integrate greater amounts of electrical energy from renewable sources especially from wind turbines and solar photo-voltaic installations exists and recent experience in the island of Ireland demonstrates that this requirement influences the behaviour of conventional generating stations. One observation is the change in the electrical power output of synchronous generators following a transient disturbance especially their oscillatory behaviour accompanied by similar oscillatory behaviour of the grid frequency, both becoming more pronounced with reducing grid inertia. This behaviour cannot be reproduced with existing mathematical models indicating that an understanding of the behaviour of synchronous generators, subjected to various disturbances especially in a system with low inertia requires a new modelling technique. Thus two models of a generating station based on a double pendulum described by a system of coupled nonlinear differential equations and suitable for analysis of its stability corresponding to infinite or finite grid inertia are presented. Formal analytic solutions of the equations of motion are given and compared with numerical solutions. In particular the new finite grid model will allow one to identify limitations to the operational range of the synchronous generators used in conventional power generation and also to identify limits, such as the allowable Rate of Change of Frequency which is currently set to ± 0.5 Hz/s and is a major factor in describing the volatility of a grid as well as identifying requirements to the total inertia necessary, which is currently provided by conventional power generators only, thus allowing one to maximise the usage of grid connected non-synchronous generators, e.g., wind turbines and solar photo-voltaic installations.

Optimized design and control of an off grid solar PV/hydrogen fuel cell power system for green buildings

NASA Astrophysics Data System (ADS)

Ghenai, C.; Bettayeb, M.

2017-11-01

Modelling, simulation, optimization and control strategies are used in this study to design a stand-alone solar PV/Fuel Cell/Battery/Generator hybrid power system to serve the electrical load of a commercial building. The main objective is to design an off grid energy system to meet the desired electric load of the commercial building with high renewable fraction, low emissions and low cost of energy. The goal is to manage the energy consumption of the building, reduce the associate cost and to switch from grid-tied fossil fuel power system to an off grid renewable and cleaner power system. Energy audit was performed in this study to determine the energy consumption of the building. Hourly simulations, modelling and optimization were performed to determine the performance and cost of the hybrid power configurations using different control strategies. The results show that the hybrid off grid solar PV/Fuel Cell/Generator/Battery/Inverter power system offers the best performance for the tested system architectures. From the total energy generated from the off grid hybrid power system, 73% is produced from the solar PV, 24% from the fuel cell and 3% from the backup Diesel generator. The produced power is used to meet all the AC load of the building without power shortage (<0.1%). The hybrid power system produces 18.2% excess power that can be used to serve the thermal load of the building. The proposed hybrid power system is sustainable, economically viable and environmentally friendly: High renewable fraction (66.1%), low levelized cost of energy (92 /MWh), and low carbon dioxide emissions (24 kg CO2/MWh) are achieved.

Solar Energy Grid Integration Systems (SEGIS): adding functionality while maintaining reliability and economics

NASA Astrophysics Data System (ADS)

Bower, Ward

2011-09-01

An overview of the activities and progress made during the US DOE Solar Energy Grid Integration Systems (SEGIS) solicitation, while maintaining reliability and economics is provided. The SEGIS R&D opened pathways for interconnecting PV systems to intelligent utility grids and micro-grids of the future. In addition to new capabilities are "value added" features. The new hardware designs resulted in smaller, less material-intensive products that are being viewed by utilities as enabling dispatchable generation and not just unpredictable negative loads. The technical solutions enable "advanced integrated system" concepts and "smart grid" processes to move forward in a faster and focused manner. The advanced integrated inverters/controllers can now incorporate energy management functionality, intelligent electrical grid support features and a multiplicity of communication technologies. Portals for energy flow and two-way communications have been implemented. SEGIS hardware was developed for the utility grid of today, which was designed for one-way power flow, for intermediate grid scenarios, AND for the grid of tomorrow, which will seamlessly accommodate managed two-way power flows as required by large-scale deployment of solar and other distributed generation. The SEGIS hardware and control developed for today meets existing standards and codes AND provides for future connections to a "smart grid" mode that enables utility control and optimized performance.

Output Control Technologies for a Large-scale PV System Considering Impacts on a Power Grid

NASA Astrophysics Data System (ADS)

Kuwayama, Akira

The mega-solar demonstration project named “Verification of Grid Stabilization with Large-scale PV Power Generation systems” had been completed in March 2011 at Wakkanai, the northernmost city of Japan. The major objectives of this project were to evaluate adverse impacts of large-scale PV power generation systems connected to the power grid and develop output control technologies with integrated battery storage system. This paper describes the outline and results of this project. These results show the effectiveness of battery storage system and also proposed output control methods for a large-scale PV system to ensure stable operation of power grids. NEDO, New Energy and Industrial Technology Development Organization of Japan conducted this project and HEPCO, Hokkaido Electric Power Co., Inc managed the overall project.

Micro-Grids for Colonias (TX)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dean Schneider; Michael Martin; Renee Berry

2012-07-31

This report describes the results of the final implementation and testing of a hybrid micro-grid system designed for off-grid applications in underserved Colonias along the Texas/Mexico border. The project is a federally funded follow-on to a project funded by the Texas State Energy Conservation Office in 2007 that developed and demonstrated initial prototype hybrid generation systems consisting of a proprietary energy storage technology, high efficiency charging and inverting systems, photovoltaic cells, a wind turbine, and bio-diesel generators. This combination of technologies provided continuous power to dwellings that are not grid connected, with a significant savings in fuel by allowing powermore » generation at highly efficient operating conditions. The objective of this project was to complete development of the prototype systems and to finalize and engineering design; to install and operate the systems in the intended environment, and to evaluate the technical and economic effectiveness of the systems. The objectives of this project were met. This report documents the final design that was achieved and includes the engineering design documents for the system. The system operated as designed, with the system availability limited by maintenance requirements of the diesel gensets. Overall, the system achieved a 96% availability over the operation of the three deployed systems. Capital costs of the systems were dependent upon both the size of the generation system and the scope of the distribution grid, but, in this instance, the systems averaged $0.72/kWh delivered. This cost would decrease significantly as utilization of the system increased. The system with the highest utilization achieved a capitol cost amortized value of $0.34/kWh produced. The average amortized fuel and maintenance cost was $0.48/kWh which was dependent upon the amount of maintenance required by the diesel generator. Economically, the system is difficult to justify as an alternative to grid power. However, the operational costs are reasonable if grid power is unavailable, e.g. in a remote area or in a disaster recovery situation. In fact, avoided fuel costs for the smaller of the systems in use during this project would have a payback of the capital costs of that system in 2.3 years, far short of the effective system life.« less

CFD Script for Rapid TPS Damage Assessment

NASA Technical Reports Server (NTRS)

McCloud, Peter

2013-01-01

This grid generation script creates unstructured CFD grids for rapid thermal protection system (TPS) damage aeroheating assessments. The existing manual solution is cumbersome, open to errors, and slow. The invention takes a large-scale geometry grid and its large-scale CFD solution, and creates a unstructured patch grid that models the TPS damage. The flow field boundary condition for the patch grid is then interpolated from the large-scale CFD solution. It speeds up the generation of CFD grids and solutions in the modeling of TPS damages and their aeroheating assessment. This process was successfully utilized during STS-134.

The development of a control system for a small high speed steam microturbine generator system

NASA Astrophysics Data System (ADS)

Alford, A.; Nichol, P.; Saunders, M.; Frisby, B.

2015-08-01

Steam is a widely used energy source. In many situations steam is generated at high pressures and then reduced in pressure through control valves before reaching point of use. An opportunity was identified to convert some of the energy at the point of pressure reduction into electricity. To take advantage of a market identified for small scale systems, a microturbine generator was designed based on a small high speed turbo machine. This machine was packaged with the necessary control valves and systems to allow connection of the machine to the grid. Traditional machines vary the speed of the generator to match the grid frequency. This was not possible due to the high speed of this machine. The characteristics of the rotating unit had to be understood to allow a control that allowed export of energy at the right frequency to the grid under the widest possible range of steam conditions. A further goal of the control system was to maximise the efficiency of generation under all conditions. A further complication was to provide adequate protection for the rotating unit in the event of the loss of connection to the grid. The system to meet these challenges is outlined with the solutions employed and tested for this application.

Occupancy change detection system and method

DOEpatents

Bruemmer, David J [Idaho Falls, ID; Few, Douglas A [Idaho Falls, ID

2009-09-01

A robot platform includes perceptors, locomotors, and a system controller. The system controller executes instructions for producing an occupancy grid map of an environment around the robot, scanning the environment to generate a current obstacle map relative to a current robot position, and converting the current obstacle map to a current occupancy grid map. The instructions also include processing each grid cell in the occupancy grid map. Within the processing of each grid cell, the instructions include comparing each grid cell in the occupancy grid map to a corresponding grid cell in the current occupancy grid map. For grid cells with a difference, the instructions include defining a change vector for each changed grid cell, wherein the change vector includes a direction from the robot to the changed grid cell and a range from the robot to the changed grid cell.

Future evolution of distributed systems for smart grid - The challenges and opportunities to using decentralized energy system

NASA Astrophysics Data System (ADS)

Konopko, Joanna

2015-12-01

A decentralized energy system is a relatively new approach in the power industry. Decentralized energy systems provide promising opportunities for deploying renewable energy sources locally available as well as for expanding access to clean energy services to remote communities. The electricity system of the future must produce and distribute electricity that is reliable and affordable. To accomplish these goals, both the electricity grid and the existing regulatory system must be smarter. In this paper, the major issues and challenges in distributed systems for smart grid are discussed and future trends are presented. The smart grid technologies and distributed generation systems are explored. A general overview of the comparison of the traditional grid and smart grid is also included.

Intelligent and robust optimization frameworks for smart grids

NASA Astrophysics Data System (ADS)

Dhansri, Naren Reddy

A smart grid implies a cyberspace real-time distributed power control system to optimally deliver electricity based on varying consumer characteristics. Although smart grids solve many of the contemporary problems, they give rise to new control and optimization problems with the growing role of renewable energy sources such as wind or solar energy. Under highly dynamic nature of distributed power generation and the varying consumer demand and cost requirements, the total power output of the grid should be controlled such that the load demand is met by giving a higher priority to renewable energy sources. Hence, the power generated from renewable energy sources should be optimized while minimizing the generation from non renewable energy sources. This research develops a demand-based automatic generation control and optimization framework for real-time smart grid operations by integrating conventional and renewable energy sources under varying consumer demand and cost requirements. Focusing on the renewable energy sources, the intelligent and robust control frameworks optimize the power generation by tracking the consumer demand in a closed-loop control framework, yielding superior economic and ecological benefits and circumvent nonlinear model complexities and handles uncertainties for superior real-time operations. The proposed intelligent system framework optimizes the smart grid power generation for maximum economical and ecological benefits under an uncertain renewable wind energy source. The numerical results demonstrate that the proposed framework is a viable approach to integrate various energy sources for real-time smart grid implementations. The robust optimization framework results demonstrate the effectiveness of the robust controllers under bounded power plant model uncertainties and exogenous wind input excitation while maximizing economical and ecological performance objectives. Therefore, the proposed framework offers a new worst-case deterministic optimization algorithm for smart grid automatic generation control.

An unstructured-grid software system for solving complex aerodynamic problems

NASA Technical Reports Server (NTRS)

Frink, Neal T.; Pirzadeh, Shahyar; Parikh, Paresh

1995-01-01

A coordinated effort has been underway over the past four years to elevate unstructured-grid methodology to a mature level. The goal of this endeavor is to provide a validated capability to non-expert users for performing rapid aerodynamic analysis and design of complex configurations. The Euler component of the system is well developed, and is impacting a broad spectrum of engineering needs with capabilities such as rapid grid generation and inviscid flow analysis, inverse design, interactive boundary layers, and propulsion effects. Progress is also being made in the more tenuous Navier-Stokes component of the system. A robust grid generator is under development for constructing quality thin-layer tetrahedral grids, along with a companion Navier-Stokes flow solver. This paper presents an overview of this effort, along with a perspective on the present and future status of the methodology.

Optimal Wind Energy Integration in Large-Scale Electric Grids

NASA Astrophysics Data System (ADS)

Albaijat, Mohammad H.

The major concern in electric grid operation is operating under the most economical and reliable fashion to ensure affordability and continuity of electricity supply. This dissertation investigates the effects of such challenges, which affect electric grid reliability and economic operations. These challenges are: 1. Congestion of transmission lines, 2. Transmission lines expansion, 3. Large-scale wind energy integration, and 4. Phaser Measurement Units (PMUs) optimal placement for highest electric grid observability. Performing congestion analysis aids in evaluating the required increase of transmission line capacity in electric grids. However, it is necessary to evaluate expansion of transmission line capacity on methods to ensure optimal electric grid operation. Therefore, the expansion of transmission line capacity must enable grid operators to provide low-cost electricity while maintaining reliable operation of the electric grid. Because congestion affects the reliability of delivering power and increases its cost, the congestion analysis in electric grid networks is an important subject. Consequently, next-generation electric grids require novel methodologies for studying and managing congestion in electric grids. We suggest a novel method of long-term congestion management in large-scale electric grids. Owing to the complication and size of transmission line systems and the competitive nature of current grid operation, it is important for electric grid operators to determine how many transmission lines capacity to add. Traditional questions requiring answers are "Where" to add, "How much of transmission line capacity" to add, and "Which voltage level". Because of electric grid deregulation, transmission lines expansion is more complicated as it is now open to investors, whose main interest is to generate revenue, to build new transmission lines. Adding a new transmission capacity will help the system to relieve the transmission system congestion, create profit for investors for renting their transmission capacity, and cheaper electricity for end users. We propose a hybrid method based on a heuristic and deterministic method to attain new transmission lines additions and increase transmission capacity. Renewable energy resources (RES) have zero operating cost, which makes them very attractive for generation companies and market participants. In addition, RES have zero carbon emission, which helps relieve the concerns of environmental impacts of electric generation resources' carbon emission. RES are wind, solar, hydro, biomass, and geothermal. By 2030, the expectation is that more than 30% of electricity in the U.S. will come from RES. One major contributor of RES generation will be from wind energy resources (WES). Furthermore, WES will be an important component of the future generation portfolio. However, the nature of WES is that it experiences a high intermittency and volatility. Because of the great expectation of high WES penetration and the nature of such resources, researchers focus on studying the effects of such resources on the electric grid operation and its adequacy from different aspects. Additionally, current market operations of electric grids add another complication to consider while integrating RES (e.g., specifically WES). Mandates by market rules and long-term analysis of renewable penetration in large-scale electric grid are also the focus of researchers in recent years. We advocate a method for high-wind resources penetration study on large-scale electric grid operations. PMU is a geographical positioning system (GPS) based device, which provides immediate and precise measurements of voltage angle in a high-voltage transmission system. PMUs can update the status of a transmission line and related measurements (e.g., voltage magnitude and voltage phase angle) more frequently. Every second, a PMU can provide 30 samples of measurements compared to traditional systems (e.g., supervisory control and data acquisition [SCADA] system), which provides one sample of measurement every 2 to 5 seconds. Because PMUs provide more measurement data samples, PMU can improve electric grid reliability and observability. (Abstract shortened by UMI.)

A study using a Monte Carlo method of the optimal configuration of a distribution network in terms of power loss sensing.

PubMed

Moon, Hyun Ho; Lee, Jong Joo; Choi, Sang Yule; Cha, Jae Sang; Kang, Jang Mook; Kim, Jong Tae; Shin, Myong Chul

2011-01-01

Recently there have been many studies of power systems with a focus on "New and Renewable Energy" as part of "New Growth Engine Industry" promoted by the Korean government. "New And Renewable Energy"-especially focused on wind energy, solar energy and fuel cells that will replace conventional fossil fuels-is a part of the Power-IT Sector which is the basis of the SmartGrid. A SmartGrid is a form of highly-efficient intelligent electricity network that allows interactivity (two-way communications) between suppliers and consumers by utilizing information technology in electricity production, transmission, distribution and consumption. The New and Renewable Energy Program has been driven with a goal to develop and spread through intensive studies, by public or private institutions, new and renewable energy which, unlike conventional systems, have been operated through connections with various kinds of distributed power generation systems. Considerable research on smart grids has been pursued in the United States and Europe. In the United States, a variety of research activities on the smart power grid have been conducted within EPRI's IntelliGrid research program. The European Union (EU), which represents Europe's Smart Grid policy, has focused on an expansion of distributed generation (decentralized generation) and power trade between countries with improved environmental protection. Thus, there is current emphasis on a need for studies that assesses the economic efficiency of such distributed generation systems. In this paper, based on the cost of distributed power generation capacity, calculations of the best profits obtainable were made by a Monte Carlo simulation. Monte Carlo simulations that rely on repeated random sampling to compute their results take into account the cost of electricity production, daily loads and the cost of sales and generate a result faster than mathematical computations. In addition, we have suggested the optimal design, which considers the distribution loss associated with power distribution systems focus on sensing aspect and distributed power generation.

GRAPEVINE: Grids about anything by Poisson's equation in a visually interactive networking environment

NASA Technical Reports Server (NTRS)

Sorenson, Reese L.; Mccann, Karen

1992-01-01

A proven 3-D multiple-block elliptic grid generator, designed to run in 'batch mode' on a supercomputer, is improved by the creation of a modern graphical user interface (GUI) running on a workstation. The two parts are connected in real time by a network. The resultant system offers a significant speedup in the process of preparing and formatting input data and the ability to watch the grid solution converge by replotting the grid at each iteration step. The result is a reduction in user time and CPU time required to generate the grid and an enhanced understanding of the elliptic solution process. This software system, called GRAPEVINE, is described, and certain observations are made concerning the creation of such software.

48. VIEW LOOKING NORTHEAST AT EXCITER RESISTANCE GRIDS LOCATED UNDER ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

48. VIEW LOOKING NORTHEAST AT EXCITER RESISTANCE GRIDS LOCATED UNDER THE CONTROL ROOM ON SOUTH SIDE OF TURBINE HALL. THE GRIDS WERE AN ESSENTIAL PART OF THE CONTROL SYSTEM THAT MAINTAINED CONSTANT VOLTAGE ON THE RAILROAD POWER LINES. TIRRILL VOLTAGE REGULATORS (SEE CT-142A-100) SENSED VOLTAGE VARIATIONS AND INITIATED SWITCHING SEQUENCES TO REGULATE THE VOLTAGE AND MAINTAIN A SYSTEM STANDARD VOLTAGE. THE RESISTANCE GRIDS WERE SEQUENTIALLY ADDED TO OR REMOVED FROM THE GENERATOR FIELD COIL CIRCUITS. THIS RESISTANCE LOAD DISSIPATED EXCITIR GENERATOR POWER AS HEAT. THIS IN TURN WOULD VARY THE STRENGTH OF THE FIELD MAGNET AND CONSEQUENTLY RAISE OR LOWER THE OUTPUT VOLTAGE FROM THE MAIN GENERATOR ARMATURE. - New York, New Haven & Hartford Railroad, Cos Cob Power Plant, Sound Shore Drive, Greenwich, Fairfield County, CT

A package for 3-D unstructured grid generation, finite-element flow solution and flow field visualization

NASA Technical Reports Server (NTRS)

Parikh, Paresh; Pirzadeh, Shahyar; Loehner, Rainald

1990-01-01

A set of computer programs for 3-D unstructured grid generation, fluid flow calculations, and flow field visualization was developed. The grid generation program, called VGRID3D, generates grids over complex configurations using the advancing front method. In this method, the point and element generation is accomplished simultaneously, VPLOT3D is an interactive, menudriven pre- and post-processor graphics program for interpolation and display of unstructured grid data. The flow solver, VFLOW3D, is an Euler equation solver based on an explicit, two-step, Taylor-Galerkin algorithm which uses the Flux Corrected Transport (FCT) concept for a wriggle-free solution. Using these programs, increasingly complex 3-D configurations of interest to aerospace community were gridded including a complete Space Transportation System comprised of the space-shuttle orbitor, the solid-rocket boosters, and the external tank. Flow solutions were obtained on various configurations in subsonic, transonic, and supersonic flow regimes.

Intelligent Control of Micro Grid: A Big Data-Based Control Center

NASA Astrophysics Data System (ADS)

Liu, Lu; Wang, Yanping; Liu, Li; Wang, Zhiseng

2018-01-01

In this paper, a structure of micro grid system with big data-based control center is introduced. Energy data from distributed generation, storage and load are analized through the control center, and from the results new trends will be predicted and applied as a feedback to optimize the control. Therefore, each step proceeded in micro grid can be adjusted and orgnized in a form of comprehensive management. A framework of real-time data collection, data processing and data analysis will be proposed by employing big data technology. Consequently, a integrated distributed generation and a optimized energy storage and transmission process can be implemented in the micro grid system.

Sensitivity of power system operations to projected changes in water availability due to climate change: the Western U.S. case study

NASA Astrophysics Data System (ADS)

Voisin, N.; Macknick, J.; Fu, T.; O'Connell, M.; Zhou, T.; Brinkman, G.

2017-12-01

Water resources provide multiple critical services to the electrical grid through hydropower technologies, from generation to regulation of the electric grid (frequency, capacity reserve). Water resources can also represent vulnerabilities to the electric grid, as hydropower and thermo-electric facilities require water for operations. In the Western U.S., hydropower and thermo-electric plants that rely on fresh surface water represent 67% of the generating capacity. Prior studies have looked at the impact of change in water availability under future climate conditions on expected generating capacity in the Western U.S., but have not evaluated operational risks or changes resulting from climate. In this study, we systematically assess the impact of change in water availability and air temperatures on power operations, i.e. we take into account the different grid services that water resources can provide to the electric grid (generation, regulation) in the system-level context of inter-regional coordination through the electric transmission network. We leverage the Coupled Model Intercomparison Project Phase 5 (CMIP5) hydrology simulations under historical and future climate conditions, and force the large scale river routing- water management model MOSART-WM along with 2010-level sectoral water demands. Changes in monthly hydropower potential generation (including generation and reserves), as well as monthly generation capacity of thermo-electric plants are derived for each power plant in the Western U.S. electric grid. We then utilize the PLEXOS electricity production cost model to optimize power system dispatch and cost decisions for the 2010 infrastructure under 100 years of historical and future (2050 horizon) hydroclimate conditions. We use economic metrics as well as operational metrics such as generation portfolio, emissions, and reserve margins to assess the changes in power system operations between historical and future normal and extreme water availability conditions. We provide insight on how this information can be used to support resource adequacy and grid expansion studies over the Western U.S. in the context of inter-annual variability and climate change.

Hybrid PV/Wind Power Systems Incorporating Battery Storage and Considering the Stochastic Nature of Renewable Resources

NASA Astrophysics Data System (ADS)

Barnawi, Abdulwasa Bakr

Hybrid power generation system and distributed generation technology are attracting more investments due to the growing demand for energy nowadays and the increasing awareness regarding emissions and their environmental impacts such as global warming and pollution. The price fluctuation of crude oil is an additional reason for the leading oil producing countries to consider renewable resources as an alternative. Saudi Arabia as the top oil exporter country in the word announced the "Saudi Arabia Vision 2030" which is targeting to generate 9.5 GW of electricity from renewable resources. Two of the most promising renewable technologies are wind turbines (WT) and photovoltaic cells (PV). The integration or hybridization of photovoltaics and wind turbines with battery storage leads to higher adequacy and redundancy for both autonomous and grid connected systems. This study presents a method for optimal generation unit planning by installing a proper number of solar cells, wind turbines, and batteries in such a way that the net present value (NPV) is minimized while the overall system redundancy and adequacy is maximized. A new renewable fraction technique (RFT) is used to perform the generation unit planning. RFT was tested and validated with particle swarm optimization and HOMER Pro under the same conditions and environment. Renewable resources and load randomness and uncertainties are considered. Both autonomous and grid-connected system designs were adopted in the optimal generation units planning process. An uncertainty factor was designed and incorporated in both autonomous and grid connected system designs. In the autonomous hybrid system design model, the strategy including an additional amount of operation reserve as a percent of the hourly load was considered to deal with resource uncertainty since the battery storage system is the only backup. While in the grid-connected hybrid system design model, demand response was incorporated to overcome the impact of uncertainty and perform energy trading between the hybrid grid utility and main grid utility in addition to the designed uncertainty factor. After the generation unit planning was carried out and component sizing was determined, adequacy evaluation was conducted by calculating the loss of load expectation adequacy index for different contingency criteria considering probability of equipment failure. Finally, a microgrid planning was conducted by finding the proper size and location to install distributed generation units in a radial distribution network.

NCAR global model topography generation software for unstructured grids

NASA Astrophysics Data System (ADS)

Lauritzen, P. H.; Bacmeister, J. T.; Callaghan, P. F.; Taylor, M. A.

2015-06-01

It is the purpose of this paper to document the NCAR global model topography generation software for unstructured grids. Given a model grid, the software computes the fraction of the grid box covered by land, the gridbox mean elevation, and associated sub-grid scale variances commonly used for gravity wave and turbulent mountain stress parameterizations. The software supports regular latitude-longitude grids as well as unstructured grids; e.g. icosahedral, Voronoi, cubed-sphere and variable resolution grids. As an example application and in the spirit of documenting model development, exploratory simulations illustrating the impacts of topographic smoothing with the NCAR-DOE CESM (Community Earth System Model) CAM5.2-SE (Community Atmosphere Model version 5.2 - Spectral Elements dynamical core) are shown.

Development of an Advanced Grid-Connected PV-ECS System Considering Solar Energy Estimation

NASA Astrophysics Data System (ADS)

Rahman, Md. Habibur; Yamashiro, Susumu; Nakamura, Koichi

In this paper, the development and the performance of a viable distributed grid-connected power generation system of Photovoltaic-Energy Capacitor System (PV-ECS) considering solar energy estimation have been described. Instead of conventional battery Electric Double Layer Capacitors (EDLC) are used as storage device and Photovoltaic (PV) panel to generate power from solar energy. The system can generate power by PV, store energy when the demand of load is low and finally supply the stored energy to load during the period of peak demand. To realize the load leveling function properly the system will also buy power from grid line when load demand is high. Since, the power taken from grid line depends on the PV output power, a procedure has been suggested to estimate the PV output power by calculating solar radiation. In order to set the optimum value of the buy power, a simulation program has also been developed. Performance of the system has been studied for different load patterns in different weather conditions by using the estimated PV output power with the help of the simulation program.

Computational System For Rapid CFD Analysis In Engineering

NASA Technical Reports Server (NTRS)

Barson, Steven L.; Ascoli, Edward P.; Decroix, Michelle E.; Sindir, Munir M.

1995-01-01

Computational system comprising modular hardware and software sub-systems developed to accelerate and facilitate use of techniques of computational fluid dynamics (CFD) in engineering environment. Addresses integration of all aspects of CFD analysis process, including definition of hardware surfaces, generation of computational grids, CFD flow solution, and postprocessing. Incorporates interfaces for integration of all hardware and software tools needed to perform complete CFD analysis. Includes tools for efficient definition of flow geometry, generation of computational grids, computation of flows on grids, and postprocessing of flow data. System accepts geometric input from any of three basic sources: computer-aided design (CAD), computer-aided engineering (CAE), or definition by user.

Mini-biomass electric generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elliot, G.

1997-12-01

Awareness of the living standards achieved by others has resulted in a Russian population which is yearning for a higher standard of living. Such a situation demands access to affordable electricity in remote areas. Remote energy requirements creates the need to transport power or fossil fuels over long distances. Application of local renewable energy resources could eliminate the need for and costs of long distance power supply. Vast forest resources spread over most of Russia make biomass an ideal renewable energy candidate for many off-grid villages. The primary objective for this preliminary evaluation is to examine the economic feasibility ofmore » replacing distillate and gasoline fuels with local waste biomass as the primary fuel for village energy in outlying regions of Russia. Approximately 20 million people live in regions where Russia`s Unified Electric System grid does not penetrate. Most of these people are connected to smaller independent power grids, but approximately 8 million Russians live in off-grid villages and small towns served by stand-alone generation systems using either diesel fuel or gasoline. The off-grid villages depend on expensive distillate fuels and gasoline for combustion in small boilers and engines. These fuels are used for both electricity generation and district heating. Typically, diesel generator systems with a capacity of up to 1 MW serve a collective farm, settlement and their rural enterprises (there are an estimated 10,000 such systems in Russia). Smaller gasoline-fueled generator systems with capacities in the range of 0.5 - 5 kW serve smaller farms or rural enterprises (there are about 60,000 such systems in Russia).« less

Automated, Parametric Geometry Modeling and Grid Generation for Turbomachinery Applications

NASA Technical Reports Server (NTRS)

Harrand, Vincent J.; Uchitel, Vadim G.; Whitmire, John B.

2000-01-01

The objective of this Phase I project is to develop a highly automated software system for rapid geometry modeling and grid generation for turbomachinery applications. The proposed system features a graphical user interface for interactive control, a direct interface to commercial CAD/PDM systems, support for IGES geometry output, and a scripting capability for obtaining a high level of automation and end-user customization of the tool. The developed system is fully parametric and highly automated, and, therefore, significantly reduces the turnaround time for 3D geometry modeling, grid generation and model setup. This facilitates design environments in which a large number of cases need to be generated, such as for parametric analysis and design optimization of turbomachinery equipment. In Phase I we have successfully demonstrated the feasibility of the approach. The system has been tested on a wide variety of turbomachinery geometries, including several impellers and a multi stage rotor-stator combination. In Phase II, we plan to integrate the developed system with turbomachinery design software and with commercial CAD/PDM software.

A Theoretical Secure Enterprise Architecture for Multi Revenue Generating Smart Grid Sub Electric Infrastructure

ERIC Educational Resources Information Center

Chaudhry, Hina

2013-01-01

This study is a part of the smart grid initiative providing electric vehicle charging infrastructure. It is a refueling structure, an energy generating photovoltaic system and charge point electric vehicle charging station. The system will utilize advanced design and technology allowing electricity to flow from the site's normal electric service…

An electrical betweenness approach for vulnerability assessment of power grids considering the capacity of generators and load

NASA Astrophysics Data System (ADS)

Wang, Kai; Zhang, Bu-han; Zhang, Zhe; Yin, Xiang-gen; Wang, Bo

2011-11-01

Most existing research on the vulnerability of power grids based on complex networks ignores the electrical characteristics and the capacity of generators and load. In this paper, the electrical betweenness is defined by considering the maximal demand of load and the capacity of generators in power grids. The loss of load, which reflects the ability of power grids to provide sufficient power to customers, is introduced to measure the vulnerability together with the size of the largest cluster. The simulation results of the IEEE-118 bus system and the Central China Power Grid show that the cumulative distributions of node electrical betweenness follow a power-law and that the nodes with high electrical betweenness play critical roles in both topological structure and power transmission of power grids. The results prove that the model proposed in this paper is effective for analyzing the vulnerability of power grids.

Electrically heated particulate filter diagnostic systems and methods

DOEpatents

Gonze, Eugene V [Pinckney, MI

2009-09-29

A system that diagnoses regeneration of an electrically heated particulate filter is provided. The system generally includes a grid module that diagnoses a fault of the grid based on at least one of a current signal and a voltage signal. A diagnostic module at least one of sets a fault status and generates a warning signal based on the fault of the grid.

First Steps in the Smart Grid Framework: An Optimal and Feasible Pathway Toward Power System Reform in Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bracho, Riccardo; Linvill, Carl; Sedano, Richard

With the vision to transform the power sector, Mexico included in the new laws and regulations deployment of smart grid technologies and provided various attributes to the Ministry of Energy and the Energy Regulatory Commission to enact public policies and regulation. The use of smart grid technologies can have a significant impact on the integration of variable renewable energy resources while maintaining reliability and stability of the system, significantly reducing technical and non-technical electricity losses in the grid, improving cyber security, and allowing consumers to make distributed generation and demand response decisions. This report describes for Mexico's Ministry of Energymore » (SENER) an overall approach (Optimal Feasible Pathway) for moving forward with smart grid policy development in Mexico to enable increasing electric generation from renewable energy in a way that optimizes system stability and reliability in an efficient and cost-effective manner.« less

Feasibility analysis of a smart grid photovoltaics system for the subarctic rural region in Alaska

NASA Astrophysics Data System (ADS)

Yao, Lei

A smart grid photovoltaics system was developed to demonstrate that the system is feasible for a similar off-grid rural community in the subarctic region in Alaska. A system generation algorithm and a system business model were developed to determine feasibility. Based on forecasts by the PV F-Chart software, a 70° tilt angle in winter, and a 34° tilt angle in summer were determined to be the best angles for electrical output. The proposed system's electricity unit cost was calculated at 32.3 cents/kWh that is cheaper than current unsubsidized electricity price (46.8 cents/kWh) in off-grid rural communities. Given 46.8 cents/kWh as the electricity unit price, the system provider can break even when 17.3 percent of the total electrical revenue through power generated by the proposed system is charged. Given these results, the system can be economically feasible during the life-cycle period. With further incentives, the system may have a competitive advantage.

Sherry Stout | NREL

Science.gov Websites

works on international programs where she focuses on grid integration of distributed renewable works on resilience issues including distributed generation and microgrids for energy system resilience Communities Water, Energy, Food Nexus Planning and Analysis Grid Integration of Distributed Generation

Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions

NASA Technical Reports Server (NTRS)

Choo, Yung K. (Compiler)

1995-01-01

The NASA Steering Committee for Surface Modeling and Grid Generation (SMAGG) sponsored a workshop on surface modeling, grid generation, and related issues in Computational Fluid Dynamics (CFD) solutions at Lewis Research Center, Cleveland, Ohio, May 9-11, 1995. The workshop provided a forum to identify industry needs, strengths, and weaknesses of the five grid technologies (patched structured, overset structured, Cartesian, unstructured, and hybrid), and to exchange thoughts about where each technology will be in 2 to 5 years. The workshop also provided opportunities for engineers and scientists to present new methods, approaches, and applications in SMAGG for CFD. This Conference Publication (CP) consists of papers on industry overview, NASA overview, five grid technologies, new methods/ approaches/applications, and software systems.

Advanced Methodology for Simulation of Complex Flows Using Structured Grid Systems

NASA Technical Reports Server (NTRS)

Steinthorsson, Erlendur; Modiano, David

1995-01-01

Detailed simulations of viscous flows in complicated geometries pose a significant challenge to current capabilities of Computational Fluid Dynamics (CFD). To enable routine application of CFD to this class of problems, advanced methodologies are required that employ (a) automated grid generation, (b) adaptivity, (c) accurate discretizations and efficient solvers, and (d) advanced software techniques. Each of these ingredients contributes to increased accuracy, efficiency (in terms of human effort and computer time), and/or reliability of CFD software. In the long run, methodologies employing structured grid systems will remain a viable choice for routine simulation of flows in complex geometries only if genuinely automatic grid generation techniques for structured grids can be developed and if adaptivity is employed more routinely. More research in both these areas is urgently needed.

Co-optimizing Generation and Transmission Expansion with Wind Power in Large-Scale Power Grids Implementation in the US Eastern Interconnection

DOE PAGES

You, Shutang; Hadley, Stanton W.; Shankar, Mallikarjun; ...

2016-01-12

This paper studies the generation and transmission expansion co-optimization problem with a high wind power penetration rate in the US Eastern Interconnection (EI) power grid. In this paper, the generation and transmission expansion problem for the EI system is modeled as a mixed-integer programming (MIP) problem. Our paper also analyzed a time series generation method to capture the variation and correlation of both load and wind power across regions. The obtained series can be easily introduced into the expansion planning problem and then solved through existing MIP solvers. Simulation results show that the proposed planning model and series generation methodmore » can improve the expansion result significantly through modeling more detailed information of wind and load variation among regions in the US EI system. Moreover, the improved expansion plan that combines generation and transmission will aid system planners and policy makers to maximize the social welfare in large-scale power grids.« less

IGES transformer and NURBS in grid generation

NASA Technical Reports Server (NTRS)

Yu, Tzu-Yi; Soni, Bharat K.

1993-01-01

In the field of Grid Generation and the CAD/CAM, there are numerous geometry output formats which require the designer to spend a great deal of time manipulating geometrical entities in order to achieve a useful sculptured geometrical description for grid generation. Also in this process, there is a danger of losing fidelity of the geometry under consideration. This stresses the importance of a standard geometry definition for the communication link between varying CAD/CAM and grid system. The IGES (Initial Graphics Exchange Specification) file is a widely used communication between CAD/CAM and the analysis tools. The scientists at NASA Research Centers - including NASA Ames, NASA Langley, NASA Lewis, NASA Marshall - have recognized this importance and, therefore, in 1992 they formed the committee of the 'NASA-IGES' which is the subset of the standard IGES. This committee stresses the importance and encourages the CFD community to use the standard IGES file for the interface between the CAD/CAM and CFD analysis. Also, two of the IGES entities -- the NURBS Curve (Entity 126) and NURBS Surface (Entity 128) -- which have many useful geometric properties -- like the convex hull property, local control property and affine invariance, also widely utilized analytical geometries can be accurately represented using NURBS. This is important in today grid generation tools because of the emphasis of the interactive design. To satisfy the geometry transformation between the CAD/CAM system and Grid Generation field, the CAGI (Computer Aided Geometry Design) developed, which include the Geometry Transformation, Geometry Manipulation and Geometry Generation as well as the user interface. This paper will present the successful development IGES file transformer and application of NURBS definition in the grid generation.

Smart Grid Status and Metrics Report Appendices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balducci, Patrick J.; Antonopoulos, Chrissi A.; Clements, Samuel L.

A smart grid uses digital power control and communication technology to improve the reliability, security, flexibility, and efficiency of the electric system, from large generation through the delivery systems to electricity consumers and a growing number of distributed generation and storage resources. To convey progress made in achieving the vision of a smart grid, this report uses a set of six characteristics derived from the National Energy Technology Laboratory Modern Grid Strategy. The Smart Grid Status and Metrics Report defines and examines 21 metrics that collectively provide insight into the grid’s capacity to embody these characteristics. This appendix presents papersmore » covering each of the 21 metrics identified in Section 2.1 of the Smart Grid Status and Metrics Report. These metric papers were prepared in advance of the main body of the report and collectively form its informational backbone.« less

Homogeneity and EPR metrics for assessment of regular grids used in CW EPR powder simulations.

PubMed

Crăciun, Cora

2014-08-01

CW EPR powder spectra may be approximated numerically using a spherical grid and a Voronoi tessellation-based cubature. For a given spin system, the quality of simulated EPR spectra depends on the grid type, size, and orientation in the molecular frame. In previous work, the grids used in CW EPR powder simulations have been compared mainly from geometric perspective. However, some grids with similar homogeneity degree generate different quality simulated spectra. This paper evaluates the grids from EPR perspective, by defining two metrics depending on the spin system characteristics and the grid Voronoi tessellation. The first metric determines if the grid points are EPR-centred in their Voronoi cells, based on the resonance magnetic field variations inside these cells. The second metric verifies if the adjacent Voronoi cells of the tessellation are EPR-overlapping, by computing the common range of their resonance magnetic field intervals. Beside a series of well known regular grids, the paper investigates a modified ZCW grid and a Fibonacci spherical code, which are new in the context of EPR simulations. For the investigated grids, the EPR metrics bring more information than the homogeneity quantities and are better related to the grids' EPR behaviour, for different spin system symmetries. The metrics' efficiency and limits are finally verified for grids generated from the initial ones, by using the original or magnetic field-constraint variants of the Spherical Centroidal Voronoi Tessellation method. Copyright © 2014 Elsevier Inc. All rights reserved.

Experimental Verification and Integration of a Next Generation Smart Power Management System

NASA Astrophysics Data System (ADS)

Clemmer, Tavis B.

With the increase in energy demand by the residential community in this country and the diminishing fossil fuel resources being used for electric energy production there is a need for a system to efficiently manage power within a residence. The Smart Green Power Node (SGPN) is a next generation energy management system that automates on-site energy production, storage, consumption, and grid usage to yield the most savings for both the utility and the consumer. Such a system automatically manages on-site distributed generation sources such as a PhotoVoltaic (PV) input and battery storage to curtail grid energy usage when the price is high. The SGPN high level control features an advanced modular algorithm that incorporates weather data for projected PV generation, battery health monitoring algorithms, user preferences for load prioritization within the home in case of an outage, Time of Use (ToU) grid power pricing, and status of on-site resources to intelligently schedule and manage power flow between the grid, loads, and the on-site resources. The SGPN has a scalable, modular architecture such that it can be customized for user specific applications. This drove the topology for the SGPN which connects on-site resources at a low voltage DC microbus; a two stage bi-directional inverter/rectifier then couples the AC load and residential grid connect to on-site generation. The SGPN has been designed, built, and is undergoing testing. Hardware test results obtained are consistent with the design goals set and indicate that the SGPN is a viable system with recommended changes and future work.

Power grid operation risk management: V2G deployment for sustainable development

NASA Astrophysics Data System (ADS)

Haddadian, Ghazale J.

The production, transmission, and delivery of cost--efficient energy to supply ever-increasing peak loads along with a quest for developing a low-carbon economy require significant evolutions in the power grid operations. Lower prices of vast natural gas resources in the United States, Fukushima nuclear disaster, higher and more intense energy consumptions in China and India, issues related to energy security, and recent Middle East conflicts, have urged decisions makers throughout the world to look into other means of generating electricity locally. As the world look to combat climate changes, a shift from carbon-based fuels to non-carbon based fuels is inevitable. However, the variability of distributed generation assets in the electricity grid has introduced major reliability challenges for power grid operators. While spearheading sustainable and reliable power grid operations, this dissertation develops a multi-stakeholder approach to power grid operation design; aiming to address economic, security, and environmental challenges of the constrained electricity generation. It investigates the role of Electric Vehicle (EV) fleets integration, as distributed and mobile storage assets to support high penetrations of renewable energy sources, in the power grid. The vehicle-to-grid (V2G) concept is considered to demonstrate the bidirectional role of EV fleets both as a provider and consumer of energy in securing a sustainable power grid operation. The proposed optimization modeling is the application of Mixed-Integer Linear Programing (MILP) to large-scale systems to solve the hourly security-constrained unit commitment (SCUC) -- an optimal scheduling concept in the economic operation of electric power systems. The Monte Carlo scenario-based approach is utilized to evaluate different scenarios concerning the uncertainties in the operation of power grid system. Further, in order to expedite the real-time solution of the proposed approach for large-scale power systems, it considers a two-stage model using the Benders Decomposition (BD). The numerical simulation demonstrate that the utilization of smart EV fleets in power grid systems would ensure a sustainable grid operation with lower carbon footprints, smoother integration of renewable sources, higher security, and lower power grid operation costs. The results, additionally, illustrate the effectiveness of the proposed MILP approach and its potentials as an optimization tool for sustainable operation of large scale electric power systems.

Prospect of solar-PV/biogas/diesel generator hybrid energy system of an off-grid area in Bangladesh

NASA Astrophysics Data System (ADS)

Mandal, Soumya; Yasmin, Hosna; Sarker, M. R. I.; Beg, M. R. A.

2017-12-01

The study presents an analysis and suggests about how renewable sources of energy can be an alternative option to produce electricity in an off-grid area. A case study is done by surveying 235 households in an off-grid area. Techno-economic analysis of the hybrid energy system is employed by using Hybrid Optimization of Multiple Energy Resources (HOMER) software. Four solar-PV modules (each of 1kW), two biogas generators (each of 3kW), three diesel generators (each of 5kW), five batteries (each of 160 Ah) and 5kW converter is found to be the best configuration in terms of Cost of Energy (COE), environmental conditions and Renewable Fraction (RF). The Cost of Energy (COE), Net Present Cost (NPC), capital cost of this configuration is found BDT15.382, BDT10007224, and BDT2582433 respectively. The renewable fraction of this system is found 75% which indicates a lower emission compared with thegrid based system and stand-alone diesel system. Although the COE is higher than grid electricity, this system offers a cheaper option than using kerosene oil and solar home systems (SHSs).

Grid Work

NASA Technical Reports Server (NTRS)

1998-01-01

Pointwise Inc.'s, Gridgen Software is a system for the generation of 3D (three dimensional) multiple block, structured grids. Gridgen is a visually-oriented, graphics-based interactive code used to decompose a 3D domain into blocks, distribute grid points on curves, initialize and refine grid points on surfaces and initialize volume grid points. Gridgen is available to U.S. citizens and American-owned companies by license.

High-Efficiency Food Production in a Renewable Energy Based Micro-Grid Power System

NASA Technical Reports Server (NTRS)

Bubenheim, David; Meiners, Dennis

2016-01-01

Controlled Environment Agriculture (CEA) systems can be used to produce high-quality, desirable food year round, and the fresh produce can positively contribute to the health and well being of residents in communities with difficult supply logistics. While CEA has many positive outcomes for a remote community, the associated high electric demands have prohibited widespread implementation in what is typically already a fully subscribed power generation and distribution system. Recent advances in CEA technologies as well as renewable power generation, storage, and micro-grid management are increasing system efficiency and expanding the possibilities for enhancing community supporting infrastructure without increasing demands for outside supplied fuels. We will present examples of how new lighting, nutrient delivery, and energy management and control systems can enable significant increases in food production efficiency while maintaining high yields in CEA. Examples from Alaskan communities where initial incorporation of renewable power generation, energy storage and grid management techniques have already reduced diesel fuel consumption for electric generation by more than 40% and expanded grid capacity will be presented. We will discuss how renewable power generation, efficient grid management to extract maximum community service per kW, and novel energy storage approaches can expand the food production, water supply, waste treatment, sanitation and other community support services without traditional increases of consumable fuels supplied from outside the community. These capabilities offer communities with a range of choices to enhance their communities. The examples represent a synergy of technology advancement efforts to develop sustainable community support systems for future space-based human habitats and practical implementation of infrastructure components to increase efficiency and enhance health and well being in remote communities today and tomorrow.

Market-Based Indian Grid Integration Study Options: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoltenberg, B.; Clark, K.; Negi, S. K.

2012-03-01

The Indian state of Gujarat is forecasting solar and wind generation expansion from 16% to 32% of installed generation capacity by 2015. Some states in India are already experiencing heavy wind power curtailment. Understanding how to integrate variable generation (VG) into the grid is of great interest to local transmission companies and India's Ministry of New and Renewable Energy. This paper describes the nature of a market-based integration study and how this approach, while new to Indian grid operation and planning, is necessary to understand how to operate and expand the grid to best accommodate the expansion of VG. Second,more » it discusses options in defining a study's scope, such as data granularity, generation modeling, and geographic scope. The paper also explores how Gujarat's method of grid operation and current system reliability will affect how an integration study can be performed.« less

Application of advanced grid generation techniques for flow field computations about complex configurations

NASA Technical Reports Server (NTRS)

Kathong, Monchai; Tiwari, Surendra N.

1988-01-01

In the computation of flowfields about complex configurations, it is very difficult to construct a boundary-fitted coordinate system. An alternative approach is to use several grids at once, each of which is generated independently. This procedure is called the multiple grids or zonal grids approach; its applications are investigated. The method conservative providing conservation of fluxes at grid interfaces. The Euler equations are solved numerically on such grids for various configurations. The numerical scheme used is the finite-volume technique with a three-stage Runge-Kutta time integration. The code is vectorized and programmed to run on the CDC VPS-32 computer. Steady state solutions of the Euler equations are presented and discussed. The solutions include: low speed flow over a sphere, high speed flow over a slender body, supersonic flow through a duct, and supersonic internal/external flow interaction for an aircraft configuration at various angles of attack. The results demonstrate that the multiple grids approach along with the conservative interfacing is capable of computing the flows about the complex configurations where the use of a single grid system is not possible.

A Study Using a Monte Carlo Method of the Optimal Configuration of a Distribution Network in Terms of Power Loss Sensing

PubMed Central

Moon, Hyun Ho; Lee, Jong Joo; Choi, Sang Yule; Cha, Jae Sang; Kang, Jang Mook; Kim, Jong Tae; Shin, Myong Chul

2011-01-01

Recently there have been many studies of power systems with a focus on “New and Renewable Energy” as part of “New Growth Engine Industry” promoted by the Korean government. “New And Renewable Energy”—especially focused on wind energy, solar energy and fuel cells that will replace conventional fossil fuels—is a part of the Power-IT Sector which is the basis of the SmartGrid. A SmartGrid is a form of highly-efficient intelligent electricity network that allows interactivity (two-way communications) between suppliers and consumers by utilizing information technology in electricity production, transmission, distribution and consumption. The New and Renewable Energy Program has been driven with a goal to develop and spread through intensive studies, by public or private institutions, new and renewable energy which, unlike conventional systems, have been operated through connections with various kinds of distributed power generation systems. Considerable research on smart grids has been pursued in the United States and Europe. In the United States, a variety of research activities on the smart power grid have been conducted within EPRI’s IntelliGrid research program. The European Union (EU), which represents Europe’s Smart Grid policy, has focused on an expansion of distributed generation (decentralized generation) and power trade between countries with improved environmental protection. Thus, there is current emphasis on a need for studies that assesses the economic efficiency of such distributed generation systems. In this paper, based on the cost of distributed power generation capacity, calculations of the best profits obtainable were made by a Monte Carlo simulation. Monte Carlo simulations that rely on repeated random sampling to compute their results take into account the cost of electricity production, daily loads and the cost of sales and generate a result faster than mathematical computations. In addition, we have suggested the optimal design, which considers the distribution loss associated with power distribution systems focus on sensing aspect and distributed power generation. PMID:22164047

An Efficient Means of Adaptive Refinement Within Systems of Overset Grids

NASA Technical Reports Server (NTRS)

Meakin, Robert L.

1996-01-01

An efficient means of adaptive refinement within systems of overset grids is presented. Problem domains are segregated into near-body and off-body fields. Near-body fields are discretized via overlapping body-fitted grids that extend only a short distance from body surfaces. Off-body fields are discretized via systems of overlapping uniform Cartesian grids of varying levels of refinement. a novel off-body grid generation and management scheme provides the mechanism for carrying out adaptive refinement of off-body flow dynamics and solid body motion. The scheme allows for very efficient use of memory resources, and flow solvers and domain connectivity routines that can exploit the structure inherent to uniform Cartesian grids.

Modified Perfect Harmonics Cancellation Control of a Grid Interfaced SPV Power Generation

NASA Astrophysics Data System (ADS)

Singh, B.; Shahani, D. T.; Verma, A. K.

2015-03-01

This paper deals with a grid interfaced solar photo voltaic (SPV) power generating system with modified perfect harmonic cancellation (MPHC) control for power quality improvement in terms of mitigation of the current harmonics, power factor correction, control of point of common coupling (PCC) voltage with reactive power compensation and load balancing in a three phase distribution system. The proposed grid interfaced SPV system consists of a SPV array, a dc-dc boost converter and a voltage source converter (VSC) used for the compensation of other connected linear and nonlinear loads at PCC. The reference grid currents are estimated using MPHC method and control signals are derived by using pulse width modulation (PWM) current controller of VSC. The SPV power is fed to the common dc bus of VSC and dc-dc boost converter using maximum power point tracking (MPPT). The dc link voltage of VSC is regulated by using dc voltage proportional integral (PI) controller. The analysis of the proposed SPV power generating system is carried out under dc/ac short circuit and severe SPV-SX and SPV-TX intrusion.

Aerodynamic simulation on massively parallel systems

NASA Technical Reports Server (NTRS)

Haeuser, Jochem; Simon, Horst D.

1992-01-01

This paper briefly addresses the computational requirements for the analysis of complete configurations of aircraft and spacecraft currently under design to be used for advanced transportation in commercial applications as well as in space flight. The discussion clearly shows that massively parallel systems are the only alternative which is both cost effective and on the other hand can provide the necessary TeraFlops, needed to satisfy the narrow design margins of modern vehicles. It is assumed that the solution of the governing physical equations, i.e., the Navier-Stokes equations which may be complemented by chemistry and turbulence models, is done on multiblock grids. This technique is situated between the fully structured approach of classical boundary fitted grids and the fully unstructured tetrahedra grids. A fully structured grid best represents the flow physics, while the unstructured grid gives best geometrical flexibility. The multiblock grid employed is structured within a block, but completely unstructured on the block level. While a completely unstructured grid is not straightforward to parallelize, the above mentioned multiblock grid is inherently parallel, in particular for multiple instruction multiple datastream (MIMD) machines. In this paper guidelines are provided for setting up or modifying an existing sequential code so that a direct parallelization on a massively parallel system is possible. Results are presented for three parallel systems, namely the Intel hypercube, the Ncube hypercube, and the FPS 500 system. Some preliminary results for an 8K CM2 machine will also be mentioned. The code run is the two dimensional grid generation module of Grid, which is a general two dimensional and three dimensional grid generation code for complex geometries. A system of nonlinear Poisson equations is solved. This code is also a good testcase for complex fluid dynamics codes, since the same datastructures are used. All systems provided good speedups, but message passing MIMD systems seem to be best suited for large miltiblock applications.

Grid-Tied Photovoltaic Power System

NASA Technical Reports Server (NTRS)

Eichenberg, Dennis J.

2011-01-01

A grid-tied photovoltaic (PV) power system is connected directly to the utility distribution grid. Facility power can be obtained from the utility system as normal. The PV system is synchronized with the utility system to provide power for the facility, and excess power is provided to the utility. Operating costs of a PV power system are low compared to conventional power technologies. This method can displace the highest-cost electricity during times of peak demand in most climatic regions, and thus reduce grid loading. Net metering is often used, in which independent power producers such as PV power systems are connected to the utility grid via the customers main service panels and meters. When the PV power system is generating more power than required at that location, the excess power is provided to the utility grid. The customer pays the net of the power purchased when the on-site power demand is greater than the onsite power production, and the excess power is returned to the utility grid. Power generated by the PV system reduces utility demand, and the surplus power aids the community. Modern PV panels are readily available, reliable, efficient, and economical, with a life expectancy of at least 25 years. Modern electronics have been the enabling technology behind grid-tied power systems, making them safe, reliable, efficient, and economical with a life expectancy equal to the modern PV panels. The grid-tied PV power system was successfully designed and developed, and this served to validate the basic principles developed, and the theoretical work that was performed. Grid-tied PV power systems are reliable, maintenance- free, long-life power systems, and are of significant value to NASA and the community. Of particular value are the analytical tools and capabilities that have been successfully developed. Performance predictions can be made confidently for grid-tied PV systems of various scales. The work was done under the NASA Hybrid Power Management (HPM) Program, which is the integration of diverse power devices in an optimal configuration for space and terrestrial applications.

Controllable Grid Interface for Testing Ancillary Service Controls and Fault Performance of Utility-Scale Wind Power Generation: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gevorgian, Vahan; Koralewicz, Przemyslaw; Wallen, Robb

The rapid expansion of wind power has led many transmission system operators to demand modern wind power plants to comply with strict interconnection requirements. Such requirements involve various aspects of wind power plant operation, including fault ride-through and power quality performance as well as the provision of ancillary services to enhance grid reliability. During recent years, the National Renewable Energy Laboratory (NREL) of the U.S. Department of Energy has developed a new, groundbreaking testing apparatus and methodology to test and demonstrate many existing and future advanced controls for wind generation (and other renewable generation technologies) on the multimegawatt scale andmore » medium-voltage levels. This paper describes the capabilities and control features of NREL's 7-MVA power electronic grid simulator (also called a controllable grid interface, or CGI) that enables testing many active and reactive power control features of modern wind turbine generators -- including inertial response, primary and secondary frequency responses, and voltage regulation -- under a controlled, medium-voltage grid environment. In particular, this paper focuses on the specifics of testing the balanced and unbalanced fault ride-through characteristics of wind turbine generators under simulated strong and weak medium-voltage grid conditions. In addition, this paper provides insights on the power hardware-in-the-loop feature implemented in the CGI to emulate (in real time) the conditions that might exist in various types of electric power systems under normal operations and/or contingency scenarios. Using actual test examples and simulation results, this paper describes the value of CGI as an ultimate modeling validation tool for all types of 'grid-friendly' controls by wind generation.« less

Electric Sector Integration | Energy Analysis | NREL

Science.gov Websites

investigates the potential impacts of expanding renewable technology deployment on grid operations and Electric System Flexibility and Storage Impacts on Conventional Generators Transmission Infrastructure Generation Our grid integration studies use state-of-the-art modeling and analysis to evaluate the impacts of

A three-dimensional application with the numerical grid generation code: EAGLE (utilizing an externally generated surface)

NASA Technical Reports Server (NTRS)

Houston, Johnny L.

1990-01-01

Program EAGLE (Eglin Arbitrary Geometry Implicit Euler) is a multiblock grid generation and steady-state flow solver system. This system combines a boundary conforming surface generation, a composite block structure grid generation scheme, and a multiblock implicit Euler flow solver algorithm. The three codes are intended to be used sequentially from the definition of the configuration under study to the flow solution about the configuration. EAGLE was specifically designed to aid in the analysis of both freestream and interference flow field configurations. These configurations can be comprised of single or multiple bodies ranging from simple axisymmetric airframes to complex aircraft shapes with external weapons. Each body can be arbitrarily shaped with or without multiple lifting surfaces. Program EAGLE is written to compile and execute efficiently on any CRAY machine with or without Solid State Disk (SSD) devices. Also, the code uses namelist inputs which are supported by all CRAY machines using the FORTRAN Compiler CF177. The use of namelist inputs makes it easier for the user to understand the inputs and to operate Program EAGLE. Recently, the Code was modified to operate on other computers, especially the Sun Spare4 Workstation. Several two-dimensional grid configurations were completely and successfully developed using EAGLE. Currently, EAGLE is being used for three-dimension grid applications.

Integrating Variable Renewable Energy into the Grid: Key Issues, Greening the Grid (Spanish Version)

DOE Office of Scientific and Technical Information (OSTI.GOV)

This is the Spanish version of 'Greening the Grid - Integrating Variable Renewable Energy into the Grid: Key Issues'. To foster sustainable, low-emission development, many countries are establishing ambitious renewable energy targets for their electricity supply. Because solar and wind tend to be more variable and uncertain than conventional sources, meeting these targets will involve changes to power system planning and operations. Grid integration is the practice of developing efficient ways to deliver variable renewable energy (VRE) to the grid. Good integration methods maximize the cost-effectiveness of incorporating VRE into the power system while maintaining or increasing system stability andmore » reliability. When considering grid integration, policy makers, regulators, and system operators consider a variety of issues, which can be organized into four broad topics: New Renewable Energy Generation, New Transmission, Increased System Flexibility, and Planning for a High RE Future.« less

Surface grid generation for complex three-dimensional geometries

NASA Technical Reports Server (NTRS)

Luh, Raymond Ching-Chung

1988-01-01

An outline is presented for the creation of surface grids from primitive geometry data such as obtained from CAD/CAM systems. The general procedure is applicable to any geometry including full aircraft with wing, nacelle, and empennage. When developed in an interactive graphics environment, a code based on this procedure is expected to substantially improve the turn around time for generating surface grids on complex geometries. Results are shown for a general hypersonic airplane geometry.

Surface grid generation for complex three-dimensional geometries

NASA Technical Reports Server (NTRS)

Luh, Raymond Ching-Chung

1988-01-01

An outline is presented for the creation of surface grids from primitive geometry data such as obtained from CAD/CAM systems. The general procedure is applicable to any geometry including full aircraft with wing, nacelle, and empennage. When developed in an interactive graphics environment, a code base on this procedure is expected to substantially improve the turn around time for generating surface grids on complex geometries. Results are shown for a general hypersonic airplane geometry.

Parallel grid generation algorithm for distributed memory computers

NASA Technical Reports Server (NTRS)

Moitra, Stuti; Moitra, Anutosh

1994-01-01

A parallel grid-generation algorithm and its implementation on the Intel iPSC/860 computer are described. The grid-generation scheme is based on an algebraic formulation of homotopic relations. Methods for utilizing the inherent parallelism of the grid-generation scheme are described, and implementation of multiple levELs of parallelism on multiple instruction multiple data machines are indicated. The algorithm is capable of providing near orthogonality and spacing control at solid boundaries while requiring minimal interprocessor communications. Results obtained on the Intel hypercube for a blended wing-body configuration are used to demonstrate the effectiveness of the algorithm. Fortran implementations bAsed on the native programming model of the iPSC/860 computer and the Express system of software tools are reported. Computational gains in execution time speed-up ratios are given.

Grid Application Meta-Repository System: Repository Interconnectivity and Cross-domain Application Usage in Distributed Computing Environments

NASA Astrophysics Data System (ADS)

Tudose, Alexandru; Terstyansky, Gabor; Kacsuk, Peter; Winter, Stephen

Grid Application Repositories vary greatly in terms of access interface, security system, implementation technology, communication protocols and repository model. This diversity has become a significant limitation in terms of interoperability and inter-repository access. This paper presents the Grid Application Meta-Repository System (GAMRS) as a solution that offers better options for the management of Grid applications. GAMRS proposes a generic repository architecture, which allows any Grid Application Repository (GAR) to be connected to the system independent of their underlying technology. It also presents applications in a uniform manner and makes applications from all connected repositories visible to web search engines, OGSI/WSRF Grid Services and other OAI (Open Archive Initiative)-compliant repositories. GAMRS can also function as a repository in its own right and can store applications under a new repository model. With the help of this model, applications can be presented as embedded in virtual machines (VM) and therefore they can be run in their native environments and can easily be deployed on virtualized infrastructures allowing interoperability with new generation technologies such as cloud computing, application-on-demand, automatic service/application deployments and automatic VM generation.

High-Efficiency Food Production in a Renewable Energy Based Micro-Grid

NASA Technical Reports Server (NTRS)

Bubenheim, David L.

2017-01-01

Controlled Environment Agriculture (CEA) systems can be used to produce high-quality, desirable food year round, and the fresh produce can positively contribute to the health and well being of residents in communities with difficult supply logistics. While CEA has many positive outcomes for a remote community, the associated high electric demands have prohibited widespread implementation in what is typically already a fully subscribed power generation and distribution system. Recent advances in CEA technologies as well as renewable power generation, storage, and micro-grid management are increasing system efficiency and expanding the possibilities for enhancing community supporting infrastructure without increasing demands for outside supplied fuels. We will present examples of how new lighting, nutrient delivery, and energy management and control systems can enable significant increases in food production efficiency while maintaining high yields in CEA.Examples from Alaskan communities where initial incorporation of renewable power generation, energy storage and grid management techniques have already reduced diesel fuel consumption for electric generation by more than 40 and expanded grid capacity will be presented. We will discuss how renewable power generation, efficient grid management to extract maximum community service per kW, and novel energy storage approaches can expand the food production, water supply, waste treatment, sanitation and other community support services without traditional increases of consumable fuels supplied from outside the community. These capabilities offer communities with a range of choices to enhance their communities. The examples represent a synergy of technology advancement efforts to develop sustainable community support systems for future space-based human habitats and practical implementation of infrastructure components to increase efficiency and enhance health and well-being in remote communities today and tomorrow.

Connection technology of HPTO type WECs and DC nano grid in island

NASA Astrophysics Data System (ADS)

Wang, Kun-lin; Tian, Lian-fang; You, Ya-ge; Wang, Xiao-hong; Sheng, Song-wei; Zhang, Ya-qun; Ye, Yin

2016-07-01

Wave energy fluctuating a great deal endangers the security of power grid especially micro grid in island. A DC nano grid supported by batteries is proposed to smooth the output power of wave energy converters (WECs). Thus, renewable energy converters connected to DC grid is a new subject. The characteristics of WECs are very important to the connection technology of HPTO type WECs and DC nano grid. Hydraulic power take-off system (HPTO) is the core unit of the largest category of WECs, with the functions of supplying suitable damping for a WEC to absorb wave energy, and converting captured wave energy to electricity. The HPTO is divided into a hydraulic energy storage system (HESS) and a hydraulic power generation system (HPGS). A primary numerical model for the HPGS is established in this paper. Three important basic characteristics of the HPGS are deduced, which reveal how the generator load determines the HPGS rotation rate. Therefore, the connector of HPTO type WEC and DC nano grid would be an uncontrollable rectifier with high reliability, also would be a controllable power converter with high efficiency, such as interleaved boost converter-IBC. The research shows that it is very flexible to connect to DC nano grid for WECs, but bypass resistance loads are indispensable for the security of WECs.

Assessing the Impacts of Wind Integration in the Western Provinces

NASA Astrophysics Data System (ADS)

Sopinka, Amy

Increasing carbon dioxide levels and the fear of irreversible climate change has prompted policy makers to implement renewable portfolio standards. These renewable portfolio standards are meant to encourage the adoption of renewable energy technologies thereby reducing carbon emissions associated with fossil fuel-fired electricity generation. The ability to efficiently adopt and utilize high levels of renewable energy technology, such as wind power, depends upon the composition of the extant generation within the grid. Western Canadian electric grids are poised to integrate high levels of wind and although Alberta has sufficient and, at times, an excess supply of electricity, it does not have the inherent generator flexibility required to mirror the variability of its wind generation. British Columbia, with its large reservoir storage capacities and rapid ramping hydroelectric generation could easily provide the firming services required by Alberta; however, the two grids are connected only by a small, constrained intertie. We use a simulation model to assess the economic impacts of high wind penetrations in the Alberta grid under various balancing protocols. We find that adding wind capacity to the system impacts grid reliability, increasing the frequency of system imbalances and unscheduled intertie flow. In order for British Columbia to be viable firming resource, it must have sufficient generation capability to meet and exceed the province's electricity self-sufficiency requirements. We use a linear programming model to evaluate the province's ability to meet domestic load under various water and trade conditions. We then examine the effects of drought and wind penetration on the interconnected Alberta -- British Columbia system given differing interconnection sizes.

Wide-area, real-time monitoring and visualization system

DOEpatents

Budhraja, Vikram S.; Dyer, James D.; Martinez Morales, Carlos A.

2013-03-19

A real-time performance monitoring system for monitoring an electric power grid. The electric power grid has a plurality of grid portions, each grid portion corresponding to one of a plurality of control areas. The real-time performance monitoring system includes a monitor computer for monitoring at least one of reliability metrics, generation metrics, transmission metrics, suppliers metrics, grid infrastructure security metrics, and markets metrics for the electric power grid. The data for metrics being monitored by the monitor computer are stored in a data base, and a visualization of the metrics is displayed on at least one display computer having a monitor. The at least one display computer in one said control area enables an operator to monitor the grid portion corresponding to a different said control area.

Wide-area, real-time monitoring and visualization system

DOEpatents

Budhraja, Vikram S [Los Angeles, CA; Dyer, James D [La Mirada, CA; Martinez Morales, Carlos A [Upland, CA

2011-11-15

A real-time performance monitoring system for monitoring an electric power grid. The electric power grid has a plurality of grid portions, each grid portion corresponding to one of a plurality of control areas. The real-time performance monitoring system includes a monitor computer for monitoring at least one of reliability metrics, generation metrics, transmission metrics, suppliers metrics, grid infrastructure security metrics, and markets metrics for the electric power grid. The data for metrics being monitored by the monitor computer are stored in a data base, and a visualization of the metrics is displayed on at least one display computer having a monitor. The at least one display computer in one said control area enables an operator to monitor the grid portion corresponding to a different said control area.

Real-time performance monitoring and management system

DOEpatents

Budhraja, Vikram S [Los Angeles, CA; Dyer, James D [La Mirada, CA; Martinez Morales, Carlos A [Upland, CA

2007-06-19

A real-time performance monitoring system for monitoring an electric power grid. The electric power grid has a plurality of grid portions, each grid portion corresponding to one of a plurality of control areas. The real-time performance monitoring system includes a monitor computer for monitoring at least one of reliability metrics, generation metrics, transmission metrics, suppliers metrics, grid infrastructure security metrics, and markets metrics for the electric power grid. The data for metrics being monitored by the monitor computer are stored in a data base, and a visualization of the metrics is displayed on at least one display computer having a monitor. The at least one display computer in one said control area enables an operator to monitor the grid portion corresponding to a different said control area.

Development and Testing of a Prototype Grid-Tied Photovoltaic Power System

NASA Technical Reports Server (NTRS)

Eichenberg, Dennis J.

2009-01-01

The NASA Glenn Research Center (GRC) has developed and tested a prototype 2 kW DC grid-tied photovoltaic (PV) power system at the Center. The PV system has generated in excess of 6700 kWh since operation commenced in July 2006. The PV system is providing power to the GRC grid for use by all. Operation of the prototype PV system has been completely trouble free. A grid-tied PV power system is connected directly to the utility distribution grid. Facility power can be obtained from the utility system as normal. The PV system is synchronized with the utility system to provide power for the facility, and excess power is provided to the utility. The project transfers space technology to terrestrial use via nontraditional partners. GRC personnel glean valuable experience with PV power systems that are directly applicable to various space power systems, and provide valuable space program test data. PV power systems help to reduce harmful emissions and reduce the Nation s dependence on fossil fuels. Power generated by the PV system reduces the GRC utility demand, and the surplus power aids the community. Present global energy concerns reinforce the need for the development of alternative energy systems. Modern PV panels are readily available, reliable, efficient, and economical with a life expectancy of at least 25 years. Modern electronics has been the enabling technology behind grid-tied power systems, making them safe, reliable, efficient, and economical with a life expectancy of at least 25 years. Based upon the success of the prototype PV system, additional PV power system expansion at GRC is under consideration. The prototype grid-tied PV power system was successfully designed and developed which served to validate the basic principles described, and the theoretical work that was performed. The report concludes that grid-tied photovoltaic power systems are reliable, maintenance free, long life power systems, and are of significant value to NASA and the community.

Euler Technology Assessment for Preliminary Aircraft Design: Compressibility Predictions by Employing the Cartesian Unstructured Grid SPLITFLOW Code

NASA Technical Reports Server (NTRS)

Finley, Dennis B.; Karman, Steve L., Jr.

1996-01-01

The objective of the second phase of the Euler Technology Assessment program was to evaluate the ability of Euler computational fluid dynamics codes to predict compressible flow effects over a generic fighter wind tunnel model. This portion of the study was conducted by Lockheed Martin Tactical Aircraft Systems, using an in-house Cartesian-grid code called SPLITFLOW. The Cartesian grid technique offers several advantages, including ease of volume grid generation and reduced number of cells compared to other grid schemes. SPLITFLOW also includes grid adaption of the volume grid during the solution to resolve high-gradient regions. The SPLITFLOW code predictions of configuration forces and moments are shown to be adequate for preliminary design, including predictions of sideslip effects and the effects of geometry variations at low and high angles-of-attack. The transonic pressure prediction capabilities of SPLITFLOW are shown to be improved over subsonic comparisons. The time required to generate the results from initial surface data is on the order of several hours, including grid generation, which is compatible with the needs of the design environment.

Western Wind and Solar Integration Study Phase 3A: Low Levels of Synchronous Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Nicholas W.; Leonardi, Bruno; D'Aquila, Robert

The stability of the North American electric power grids under conditions of high penetrations of wind and solar is a significant concern and possible impediment to reaching renewable energy goals. The 33% wind and solar annual energy penetration considered in this study results in substantial changes to the characteristics of the bulk power system. This includes different power flow patterns, different commitment and dispatch of existing synchronous generation, and different dynamic behavior from wind and solar generation. The Western Wind and Solar Integration Study (WWSIS), sponsored by the U.S. Department of Energy, is one of the largest regional solar andmore » wind integration studies to date. In multiple phases, it has explored different aspects of the question: Can we integrate large amounts of wind and solar energy into the electric power system of the West? The work reported here focused on the impact of low levels of synchronous generation on the transient stability performance in one part of the region in which wind generation has displaced synchronous thermal generation under highly stressed, weak system conditions. It is essentially an extension of WWSIS-3. Transient stability, the ability of the power system to maintain synchronism among all elements following disturbances, is a major constraint on operations in many grids, including the western U.S. and Texas systems. These constraints primarily concern the performance of the large-scale bulk power system. But grid-wide stability concerns with high penetrations of wind and solar are still not thoroughly understood. This work focuses on 'traditional' fundamental frequency stability issues, such as maintaining synchronism, frequency, and voltage. The objectives of this study are to better understand the implications of low levels of synchronous generation and a weak grid on overall system performance by: 1) Investigating the Western Interconnection under conditions of both high renewable generation (e.g., wind and solar) and low synchronous generation (e.g., significant coal power plant decommitment or retirement); and 2) Analyzing both the large-scale stability of the Western Interconnection and regional stability issues driven by more geographically dispersed renewable generation interacting with a transmission grid that evolved with large, central station plants at key nodes. As noted above, the work reported here is an extension of the research performed in WWSIS-3.« less

The effect of seasonal variation on the performances of grid connected photovoltaic system in southern of Algeria

NASA Astrophysics Data System (ADS)

Zaghba, L.; Khennane, M.; Terki, N.; Borni, A.; Bouchakour, A.; Fezzani, A.; Mahamed, I. Hadj; Oudjana, S. H.

2017-02-01

This paper presents modeling, simulation, and analysis evaluation of the grid-connected PV generation system performance under MATLAB/Simulink. The objective is to study the effect of seasonal variation on the performances of grid connected photovoltaic system in southern of Algeria. This system works with a power converter. This converter allows the connection to the network and extracts maximum power from photovoltaic panels with the MPPT algorithm based on robust neuro-fuzzy sliding approach. The photovoltaic energy produced by the PV generator will be completely injected on the network. Simulation results show that the system controlled by the neuro-fuzzy sliding adapts to changing external disturbances and show their effectiveness not only for continued maximum power point but also for response time and stability.

Mitigation of Power Quality Problems in Grid-Interactive Distributed Generation System

NASA Astrophysics Data System (ADS)

Bhende, C. N.; Kalam, A.; Malla, S. G.

2016-04-01

Having an inter-tie between low/medium voltage grid and distributed generation (DG), both exposes to power quality (PQ) problems created by each other. This paper addresses various PQ problems arise due to integration of DG with grid. The major PQ problems are due to unbalanced and non-linear load connected at DG, unbalanced voltage variations on transmission line and unbalanced grid voltages which severely affect the performance of the system. To mitigate the above mentioned PQ problems, a novel integrated control of distribution static shunt compensator (DSTATCOM) is presented in this paper. DSTATCOM control helps in reducing the unbalance factor of PCC voltage. It also eliminates harmonics from line currents and makes them balanced. Moreover, DSTATCOM supplies the reactive power required by the load locally and hence, grid need not to supply the reactive power. To show the efficacy of the proposed controller, several operating conditions are considered and verified through simulation using MATLAB/SIMULINK.

Development of a large scale Chimera grid system for the Space Shuttle Launch Vehicle

NASA Technical Reports Server (NTRS)

Pearce, Daniel G.; Stanley, Scott A.; Martin, Fred W., Jr.; Gomez, Ray J.; Le Beau, Gerald J.; Buning, Pieter G.; Chan, William M.; Chiu, Ing-Tsau; Wulf, Armin; Akdag, Vedat

1993-01-01

The application of CFD techniques to large problems has dictated the need for large team efforts. This paper offers an opportunity to examine the motivations, goals, needs, problems, as well as the methods, tools, and constraints that defined NASA's development of a 111 grid/16 million point grid system model for the Space Shuttle Launch Vehicle. The Chimera approach used for domain decomposition encouraged separation of the complex geometry into several major components each of which was modeled by an autonomous team. ICEM-CFD, a CAD based grid generation package, simplified the geometry and grid topology definition by provoding mature CAD tools and patch independent meshing. The resulting grid system has, on average, a four inch resolution along the surface.

Research on grid connection control technology of double fed wind generator

NASA Astrophysics Data System (ADS)

Ling, Li

2017-01-01

The composition and working principle of variable speed constant frequency doubly fed wind power generation system is discussed in this thesis. On the basis of theoretical analysis and control on the modeling, the doubly fed wind power generation simulation control system is designed based on a TMS320F2407 digital signal processor (DSP), and has done a large amount of experimental research, which mainly include, variable speed constant frequency, constant pressure, Grid connected control experiment. The running results show that the design of simulation control system is reasonable and can meet the need of experimental research.

Design of Grid Portal System Based on RIA

NASA Astrophysics Data System (ADS)

Cao, Caifeng; Luo, Jianguo; Qiu, Zhixin

Grid portal is an important branch of grid research. In order to solve the weak expressive force, the poor interaction, the low operating efficiency and other insufficiencies of the first and second generation of grid portal system, RIA technology was introduced to it. A new portal architecture was designed based on RIA and Web service. The concrete realizing scheme of portal system was presented by using Adobe Flex/Flash technology, which formed a new design pattern. In system architecture, the design pattern has B/S and C/S superiorities, balances server and its client side, optimizes the system performance, realizes platform irrelevance. In system function, the design pattern realizes grid service call, provides client interface with rich user experience, integrates local resources by using FABridge, LCDS, Flash player and some other components.

A simple grid implementation with Berkeley Open Infrastructure for Network Computing using BLAST as a model

PubMed Central

Pinthong, Watthanai; Muangruen, Panya

2016-01-01

Development of high-throughput technologies, such as Next-generation sequencing, allows thousands of experiments to be performed simultaneously while reducing resource requirement. Consequently, a massive amount of experiment data is now rapidly generated. Nevertheless, the data are not readily usable or meaningful until they are further analysed and interpreted. Due to the size of the data, a high performance computer (HPC) is required for the analysis and interpretation. However, the HPC is expensive and difficult to access. Other means were developed to allow researchers to acquire the power of HPC without a need to purchase and maintain one such as cloud computing services and grid computing system. In this study, we implemented grid computing in a computer training center environment using Berkeley Open Infrastructure for Network Computing (BOINC) as a job distributor and data manager combining all desktop computers to virtualize the HPC. Fifty desktop computers were used for setting up a grid system during the off-hours. In order to test the performance of the grid system, we adapted the Basic Local Alignment Search Tools (BLAST) to the BOINC system. Sequencing results from Illumina platform were aligned to the human genome database by BLAST on the grid system. The result and processing time were compared to those from a single desktop computer and HPC. The estimated durations of BLAST analysis for 4 million sequence reads on a desktop PC, HPC and the grid system were 568, 24 and 5 days, respectively. Thus, the grid implementation of BLAST by BOINC is an efficient alternative to the HPC for sequence alignment. The grid implementation by BOINC also helped tap unused computing resources during the off-hours and could be easily modified for other available bioinformatics software. PMID:27547555

Recent enhancements to the GRIDGEN structured grid generation system

NASA Technical Reports Server (NTRS)

Steinbrenner, John P.; Chawner, John R.

1992-01-01

Significant enhancements are being implemented into the GRIDGEN3D, multiple block, structured grid generation software. Automatic, point-to-point, interblock connectivity will be possible through the addition of the domain entity to GRIDBLOCK's block construction process. Also, the unification of GRIDGEN2D and GRIDBLOCK has begun with the addition of edge grid point distribution capability to GRIDBLOCK. The geometric accuracy of surface grids and the ease with which databases may be obtained is being improved by adding support for standard computer-aided design formats (e.g., PATRAN Neutral and IGES files). Finally, volume grid quality was improved through addition of new SOR algorithm features and the new hybrid control function type to GRIDGEN3D.

Emissions impacts and benefits of plug-in hybrid electric vehicles and vehicle-to-grid services

DOE PAGES

Sioshansi, Ramteen; Denholm, Paul

2009-01-22

Plug-in hybrid electric vehicles (PHEVs) have been promoted as a potential technology to reduce emissions of greenhouse gases and other pollutants by using electricity instead of petroleum, and by improving electric system efficiency by providing vehicle-to-grid (V2G) services. We use an electric power system model to explicitly evaluate the change in generator dispatches resulting from PHEV deployment in the Texas grid, and apply fixed and non-parametric estimates of generator emissions rates, to estimate the resulting changes in generation emissions. Here, we find that by using the flexibility of when vehicles may be charged, generator efficiency can be increased substantially. Bymore » changing generator dispatch, a PHEV fleet of up to 15% of light-duty vehicles can actually decrease net generator NO x emissions during the ozone season, despite the additional charging load. By adding V2G services, such as spinning reserves and energy storage, CO 2, SO 2, and NO x emissions can be reduced even further.« less

Emissions impacts and benefits of plug-in hybrid electric vehicles and vehicle-to-grid services.

PubMed

Sioshansi, Ramteen; Denholm, Paul

2009-02-15

Plug-in hybrid electric vehicles (PHEVs) have been promoted as a potential technology to reduce emissions of greenhouse gases and other pollutants by using electricity instead of petroleum, and byimproving electric system efficiency by providing vehicle-to-grid (V2G) services. We use an electric power system model to explicitly evaluate the change in generator dispatches resulting from PHEV deployment in the Texas grid, and apply fixed and non-parametric estimates of generator emissions rates, to estimate the resulting changes in generation emissions. We find that by using the flexibility of when vehicles may be charged, generator efficiency can be increased substantially. By changing generator dispatch, a PHEVfleet of up to 15% of light-duty vehicles can actually decrease net generator NOx emissions during the ozone season, despite the additional charging load. By adding V2G services, such as spinning reserves and energy storage, CO2, SO2, and NOx emissions can be reduced even further.

Design of a nonlinear backstepping control strategy of grid interconnected wind power system based PMSG

NASA Astrophysics Data System (ADS)

Errami, Y.; Obbadi, A.; Sahnoun, S.; Benhmida, M.; Ouassaid, M.; Maaroufi, M.

2016-07-01

This paper presents nonlinear backstepping control for Wind Power Generation System (WPGS) based Permanent Magnet Synchronous Generator (PMSG) and connected to utility grid. The block diagram of the WPGS with PMSG and the grid side back-to-back converter is established with the dq frame of axes. This control scheme emphasises the regulation of the dc-link voltage and the control of the power factor at changing wind speed. Besides, in the proposed control strategy of WPGS, Maximum Power Point Tracking (MPPT) technique and pitch control are provided. The stability of the regulators is assured by employing Lyapunov analysis. The proposed control strategy for the system has been validated by MATLAB simulations under varying wind velocity and the grid fault condition. In addition, a comparison of simulation results based on the proposed Backstepping strategy and conventional Vector Control is provided.

Power control and management of the grid containing largescale wind power systems

NASA Astrophysics Data System (ADS)

Aula, Fadhil Toufick

The ever increasing demand for electricity has driven many countries toward the installation of new generation facilities. However, concerns such as environmental pollution and global warming issues, clean energy sources, high costs associated with installation of new conventional power plants, and fossil fuels depletion have created many interests in finding alternatives to conventional fossil fuels for generating electricity. Wind energy is one of the most rapidly growing renewable power sources and wind power generations have been increasingly demanded as an alternative to the conventional fossil fuels. However, wind power fluctuates due to variation of wind speed. Therefore, large-scale integration of wind energy conversion systems is a threat to the stability and reliability of utility grids containing these systems. They disturb the balance between power generation and consumption, affect the quality of the electricity, and complicate load sharing and load distribution managing and planning. Overall, wind power systems do not help in providing any services such as operating and regulating reserves to the power grid. In order to resolve these issues, research has been conducted in utilizing weather forecasting data to improve the performance of the wind power system, reduce the influence of the fluctuations, and plan power management of the grid containing large-scale wind power systems which consist of doubly-fed induction generator based energy conversion system. The aims of this research, my dissertation, are to provide new methods for: smoothing the output power of the wind power systems and reducing the influence of their fluctuations, power managing and planning of a grid containing these systems and other conventional power plants, and providing a new structure of implementing of latest microprocessor technology for controlling and managing the operation of the wind power system. In this research, in order to reduce and smooth the fluctuations, two methods are presented. The first method is based on a de-loaded technique while the other method is based on utilizing multiple storage facilities. The de-loaded technique is based on characteristics of the power of a wind turbine and estimation of the generated power according to weather forecasting data. The technique provides a reference power by which the wind power system will operate and generate a smooth power. In contrast, utilizing storage facilities will allow the wind power system to operate at its maximum tracking power points' strategy. Two types of energy storages are considered in this research, battery energy storage system (BESS) and pumped-hydropower storage system (PHSS), to suppress the output fluctuations and to support the wind power system to follow the system load demands. Furthermore, this method provides the ability to store energy when there is a surplus of the generated power and to reuse it when there is a shortage of power generation from wind power systems. Both methods are new in terms of utilizing of the techniques and wind speed data. A microprocessor embedded system using an IntelRTM Atom(TM) processor is presented for controlling the wind power system and for providing the remote communication for enhancing the operation of the individual wind power system in a wind farm. The embedded system helps the wind power system to respond and to follow the commands of the central control of the power system. Moreover, it enhances the performance of the wind power system through self-managing, self-functioning, and self-correcting. Finally, a method of system power management and planning is modeled and studied for a grid containing large-scale wind power systems. The method is based on a new technique through constructing a new load demand curve (NLDC) from merging the estimation of generated power from wind power systems and forecasting of the load. To summarize, the methods and their results presented in this dissertation, enhance the operation of the large-scale wind power systems and reduce their drawbacks on the operation of the power grid.

Two and three dimensional grid generation by an algebraic homotopy procedure

NASA Technical Reports Server (NTRS)

Moitra, Anutosh

1990-01-01

An algebraic method for generating two- and three-dimensional grid systems for aerospace vehicles is presented. The method is based on algebraic procedures derived from homotopic relations for blending between inner and outer boundaries of any given configuration. Stable properties of homotopic maps have been exploited to provide near-orthogonality and specified constant spacing at the inner boundary. The method has been successfully applied to analytically generated blended wing-body configurations as well as discretely defined geometries such as the High-Speed Civil Transport Aircraft. Grid examples representative of the capabilities of the method are presented.

CFD analysis of turbopump volutes

NASA Technical Reports Server (NTRS)

Ascoli, Edward P.; Chan, Daniel C.; Darian, Armen; Hsu, Wayne W.; Tran, Ken

1993-01-01

An effort is underway to develop a procedure for the regular use of CFD analysis in the design of turbopump volutes. Airflow data to be taken at NASA Marshall will be used to validate the CFD code and overall procedure. Initial focus has been on preprocessing (geometry creation, translation, and grid generation). Volute geometries have been acquired electronically and imported into the CATIA CAD system and RAGGS (Rockwell Automated Grid Generation System) via the IGES standard. An initial grid topology has been identified and grids have been constructed for turbine inlet and discharge volutes. For CFD analysis of volutes to be used regularly, a procedure must be defined to meet engineering design needs in a timely manner. Thus, a compromise must be established between making geometric approximations, the selection of grid topologies, and possible CFD code enhancements. While the initial grid developed approximated the volute tongue with a zero thickness, final computations should more accurately account for the geometry in this region. Additionally, grid topologies will be explored to minimize skewness and high aspect ratio cells that can affect solution accuracy and slow code convergence. Finally, as appropriate, code modifications will be made to allow for new grid topologies in an effort to expedite the overall CFD analysis process.

Generation Algorithm of Discrete Line in Multi-Dimensional Grids

NASA Astrophysics Data System (ADS)

Du, L.; Ben, J.; Li, Y.; Wang, R.

2017-09-01

Discrete Global Grids System (DGGS) is a kind of digital multi-resolution earth reference model, in terms of structure, it is conducive to the geographical spatial big data integration and mining. Vector is one of the important types of spatial data, only by discretization, can it be applied in grids system to make process and analysis. Based on the some constraint conditions, this paper put forward a strict definition of discrete lines, building a mathematic model of the discrete lines by base vectors combination method. Transforming mesh discrete lines issue in n-dimensional grids into the issue of optimal deviated path in n-minus-one dimension using hyperplane, which, therefore realizing dimension reduction process in the expression of mesh discrete lines. On this basis, we designed a simple and efficient algorithm for dimension reduction and generation of the discrete lines. The experimental results show that our algorithm not only can be applied in the two-dimensional rectangular grid, also can be applied in the two-dimensional hexagonal grid and the three-dimensional cubic grid. Meanwhile, when our algorithm is applied in two-dimensional rectangular grid, it can get a discrete line which is more similar to the line in the Euclidean space.

The Emerging Interdependence of the Electric Power Grid & Information and Communication Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taft, Jeffrey D.; Becker-Dippmann, Angela S.

2015-08-01

This paper examines the implications of emerging interdependencies between the electric power grid and Information and Communication Technology (ICT). Over the past two decades, electricity and ICT infrastructure have become increasingly interdependent, driven by a combination of factors including advances in sensor, network and software technologies and progress in their deployment, the need to provide increasing levels of wide-area situational awareness regarding grid conditions, and the promise of enhanced operational efficiencies. Grid operators’ ability to utilize new and closer-to-real-time data generated by sensors throughout the system is providing early returns, particularly with respect to management of the transmission system formore » purposes of reliability, coordination, congestion management, and integration of variable electricity resources such as wind generation.« less

Triangle Geometry Processing for Surface Modeling and Cartesian Grid Generation

NASA Technical Reports Server (NTRS)

Aftosmis, Michael J. (Inventor); Melton, John E. (Inventor); Berger, Marsha J. (Inventor)

2002-01-01

Cartesian mesh generation is accomplished for component based geometries, by intersecting components subject to mesh generation to extract wetted surfaces with a geometry engine using adaptive precision arithmetic in a system which automatically breaks ties with respect to geometric degeneracies. During volume mesh generation, intersected surface triangulations are received to enable mesh generation with cell division of an initially coarse grid. The hexagonal cells are resolved, preserving the ability to directionally divide cells which are locally well aligned.

Triangle geometry processing for surface modeling and cartesian grid generation

DOEpatents

Aftosmis, Michael J [San Mateo, CA; Melton, John E [Hollister, CA; Berger, Marsha J [New York, NY

2002-09-03

Cartesian mesh generation is accomplished for component based geometries, by intersecting components subject to mesh generation to extract wetted surfaces with a geometry engine using adaptive precision arithmetic in a system which automatically breaks ties with respect to geometric degeneracies. During volume mesh generation, intersected surface triangulations are received to enable mesh generation with cell division of an initially coarse grid. The hexagonal cells are resolved, preserving the ability to directionally divide cells which are locally well aligned.

Modeling flow at the nozzle of a solid rocket motor

NASA Technical Reports Server (NTRS)

Chow, Alan S.; Jin, Kang-Ren

1991-01-01

The mechanical behavior of a rocket motor internal flow field results in a system of nonlinear partial differential equations which can be solved numerically. The accuracy and the convergence of the solution of the system of equations depends largely on how precisely the sharp gradients can be resolved. An adaptive grid generation scheme is incorporated into the computer algorithm to enhance the capability of numerical modeling. With this scheme, the grid is refined as the solution evolves. This scheme significantly improves the methodology of solving flow problems in rocket nozzle by putting the refinement part of grid generation into the computer algorithm.

Review of Comprehensive Evaluation Methods for Power Quality and Its Trend in New Generation Energy System

NASA Astrophysics Data System (ADS)

Liu, Ruihua; Wang, Rong; Liu, Qunying; Yang, Li; Xi, Chuan; Wang, Wei; Li, Lingzhou; Zhao, Zhoufang; Zhou, Ying

2018-02-01

With China’s new energy generation grid connected capacity being in the forefront of the world and the uncertainty of new energy sources, such as wind energy and solar energy, it is be of great significance to study scientific and comprehensive assessment of power quality. On the foundation of analysizing the current power quality index systematically and objectively, the new energy grid power quality analysis method and comprehensive evaluation method, this paper tentatively explored the trend of the new generation of energy system power quality comprehensive evaluation.

Grid-based precision aim system and method for disrupting suspect objects

DOEpatents

Gladwell, Thomas Scott; Garretson, Justin; Hobart, Clinton G.; Monda, Mark J.

2014-06-10

A system and method for disrupting at least one component of a suspect object is provided. The system has a source for passing radiation through the suspect object, a grid board positionable adjacent the suspect object (the grid board having a plurality of grid areas, the radiation from the source passing through the grid board), a screen for receiving the radiation passing through the suspect object and generating at least one image, a weapon for deploying a discharge, and a targeting unit for displaying the image of the suspect object and aiming the weapon according to a disruption point on the displayed image and deploying the discharge into the suspect object to disable the suspect object.

Improved control strategy for PI-R current of DFIG considering voltage and current harmonics compensation

NASA Astrophysics Data System (ADS)

Song, S. Y.; Liu, Q. H.; Zhao, Y. N.; Liu, S. Y.

2016-08-01

With the rapid development of wind power generation, the related research of wind power control and integration issues has attracted much attention, and the focus of the research are shifting away from the ideal power grid environment to the actual power grid environment. As the main stream wind turbine generator, a doubly-fed induction generator (DFIG) is connected to the power grid directly by its stator, so it is particularly sensitive to the power grid. This paper studies the improvement of DFIG control technology in the power grid harmonic environment. Based on the DFIG dynamic model considering the power grid harmonic environment, this paper introduces the shortcomings of the common control strategy of DFIG, and puts forward the enhanced method. The decoupling control of the system is realized by compensating the coupling between the rotor harmonic voltage and harmonic current, improving the control performance. In addition, the simulation experiments on PSCAD/EMTDC are carried out to verify the correctness and effectiveness of the improved scheme.

Numerical Solution of the Three-Dimensional Navier-Stokes Equation.

DTIC Science & Technology

1982-03-01

compressible, viscous fluid in an arbitrary geometry. We wish to use a grid generating scheme so we assume that the geometry of the physical problem given in...bian J of the mapping are provided. (For work on grid generating schemes see [4], [5] or [6).) Hence we must solve the following system of equations...these limitations the data structure used in the ILLIAC code is to partition the grid into 8 x 8 x 8 blocks. A row of these blocks in a given

Reliability analysis for the smart grid : from cyber control and communication to physical manifestations of failure.

DOT National Transportation Integrated Search

2010-01-01

The Smart Grid is a cyber-physical system comprised of physical components, such as transmission lines and generators, and a : network of embedded systems deployed for their cyber control. Our objective is to qualitatively and quantitatively analyze ...

Reducing Stator Current Harmonics for a Doubly-Fed Induction Generator Connected to a Distorted Grid

DTIC Science & Technology

2013-09-01

electric grid voltage harmonics, which is a potential obstacle for implementing stable wind -energy systems. Two existing rotor voltage controllers...electric grid voltage harmonics, which is a potential obstacle for implementing stable wind -energy systems. Two existing rotor voltage controllers...speed of the DFIG can be adjusted to optimize turbine efficiency for given wind conditions. A common method for controlling the operating speed is

Analyzing Effect of System Inertia on Grid Frequency Forecasting Usnig Two Stage Neuro-Fuzzy System

NASA Astrophysics Data System (ADS)

Chourey, Divyansh R.; Gupta, Himanshu; Kumar, Amit; Kumar, Jitesh; Kumar, Anand; Mishra, Anup

2018-04-01

Frequency forecasting is an important aspect of power system operation. The system frequency varies with load-generation imbalance. Frequency variation depends upon various parameters including system inertia. System inertia determines the rate of fall of frequency after the disturbance in the grid. Though, inertia of the system is not considered while forecasting the frequency of power system during planning and operation. This leads to significant errors in forecasting. In this paper, the effect of inertia on frequency forecasting is analysed for a particular grid system. In this paper, a parameter equivalent to system inertia is introduced. This parameter is used to forecast the frequency of a typical power grid for any instant of time. The system gives appreciable result with reduced error.

Distributed Optimization of Sustainable Power Dispatch and Flexible Consumer Loads for Resilient Power Grid Operations

NASA Astrophysics Data System (ADS)

Srikantha, Pirathayini

Today's electric grid is rapidly evolving to provision for heterogeneous system components (e.g. intermittent generation, electric vehicles, storage devices, etc.) while catering to diverse consumer power demand patterns. In order to accommodate this changing landscape, the widespread integration of cyber communication with physical components can be witnessed in all tenets of the modern power grid. This ubiquitous connectivity provides an elevated level of awareness and decision-making ability to system operators. Moreover, devices that were typically passive in the traditional grid are now `smarter' as these can respond to remote signals, learn about local conditions and even make their own actuation decisions if necessary. These advantages can be leveraged to reap unprecedented long-term benefits that include sustainable, efficient and economical power grid operations. Furthermore, challenges introduced by emerging trends in the grid such as high penetration of distributed energy sources, rising power demands, deregulations and cyber-security concerns due to vulnerabilities in standard communication protocols can be overcome by tapping onto the active nature of modern power grid components. In this thesis, distributed constructs in optimization and game theory are utilized to design the seamless real-time integration of a large number of heterogeneous power components such as distributed energy sources with highly fluctuating generation capacities and flexible power consumers with varying demand patterns to achieve optimal operations across multiple levels of hierarchy in the power grid. Specifically, advanced data acquisition, cloud analytics (such as prediction), control and storage systems are leveraged to promote sustainable and economical grid operations while ensuring that physical network, generation and consumer comfort requirements are met. Moreover, privacy and security considerations are incorporated into the core of the proposed designs and these serve to improve the resiliency of the future smart grid. It is demonstrated both theoretically and practically that the techniques proposed in this thesis are highly scalable and robust with superior convergence characteristics. These distributed and decentralized algorithms allow individual actuating nodes to execute self-healing and adaptive actions when exposed to changes in the grid so that the optimal operating state in the grid is maintained consistently.

High-resolution integration of water, energy, and climate models to assess electricity grid vulnerabilities to climate change

NASA Astrophysics Data System (ADS)

Meng, M.; Macknick, J.; Tidwell, V. C.; Zagona, E. A.; Magee, T. M.; Bennett, K.; Middleton, R. S.

2017-12-01

The U.S. electricity sector depends on large amounts of water for hydropower generation and cooling thermoelectric power plants. Variability in water quantity and temperature due to climate change could reduce the performance and reliability of individual power plants and of the electric grid as a system. While studies have modeled water usage in power systems planning, few have linked grid operations with physical water constraints or with climate-induced changes in water resources to capture the role of the energy-water nexus in power systems flexibility and adequacy. In addition, many hydrologic and hydropower models have a limited representation of power sector water demands and grid interaction opportunities of demand response and ancillary services. A multi-model framework was developed to integrate and harmonize electricity, water, and climate models, allowing for high-resolution simulation of the spatial, temporal, and physical dynamics of these interacting systems. The San Juan River basin in the Southwestern U.S., which contains thermoelectric power plants, hydropower facilities, and multiple non-energy water demands, was chosen as a case study. Downscaled data from three global climate models and predicted regional water demand changes were implemented in the simulations. The Variable Infiltration Capacity hydrologic model was used to project inflows, ambient air temperature, and humidity in the San Juan River Basin. Resulting river operations, water deliveries, water shortage sharing agreements, new water demands, and hydroelectricity generation at the basin-scale were estimated with RiverWare. The impacts of water availability and temperature on electric grid dispatch, curtailment, cooling water usage, and electricity generation cost were modeled in PLEXOS. Lack of water availability resulting from climate, new water demands, and shortage sharing agreements will require thermoelectric generators to drastically decrease power production, as much as 50% during intensifying drought scenarios, which can have broader electricity sector system implications. Results relevant to stakeholder and power provider interests highlight the vulnerabilities in grid operations driven by water shortage agreements and changes in the climate.

Evaluation of grid generation technologies from an applied perspective

NASA Technical Reports Server (NTRS)

Hufford, Gary S.; Harrand, Vincent J.; Patel, Bhavin C.; Mitchell, Curtis R.

1995-01-01

An analysis of the grid generation process from the point of view of an applied CFD engineer is given. Issues addressed include geometric modeling, structured grid generation, unstructured grid generation, hybrid grid generation and use of virtual parts libraries in large parametric analysis projects. The analysis is geared towards comparing the effective turn around time for specific grid generation and CFD projects. The conclusion was made that a single grid generation methodology is not universally suited for all CFD applications due to both limitations in grid generation and flow solver technology. A new geometric modeling and grid generation tool, CFD-GEOM, is introduced to effectively integrate the geometric modeling process to the various grid generation methodologies including structured, unstructured, and hybrid procedures. The full integration of the geometric modeling and grid generation allows implementation of extremely efficient updating procedures, a necessary requirement for large parametric analysis projects. The concept of using virtual parts libraries in conjunction with hybrid grids for large parametric analysis projects is also introduced to improve the efficiency of the applied CFD engineer.

Towards Integrating Distributed Energy Resources and Storage Devices in Smart Grid.

PubMed

Xu, Guobin; Yu, Wei; Griffith, David; Golmie, Nada; Moulema, Paul

2017-02-01

Internet of Things (IoT) provides a generic infrastructure for different applications to integrate information communication techniques with physical components to achieve automatic data collection, transmission, exchange, and computation. The smart grid, as one of typical applications supported by IoT, denoted as a re-engineering and a modernization of the traditional power grid, aims to provide reliable, secure, and efficient energy transmission and distribution to consumers. How to effectively integrate distributed (renewable) energy resources and storage devices to satisfy the energy service requirements of users, while minimizing the power generation and transmission cost, remains a highly pressing challenge in the smart grid. To address this challenge and assess the effectiveness of integrating distributed energy resources and storage devices, in this paper we develop a theoretical framework to model and analyze three types of power grid systems: the power grid with only bulk energy generators, the power grid with distributed energy resources, and the power grid with both distributed energy resources and storage devices. Based on the metrics of the power cumulative cost and the service reliability to users, we formally model and analyze the impact of integrating distributed energy resources and storage devices in the power grid. We also use the concept of network calculus, which has been traditionally used for carrying out traffic engineering in computer networks, to derive the bounds of both power supply and user demand to achieve a high service reliability to users. Through an extensive performance evaluation, our data shows that integrating distributed energy resources conjointly with energy storage devices can reduce generation costs, smooth the curve of bulk power generation over time, reduce bulk power generation and power distribution losses, and provide a sustainable service reliability to users in the power grid.

Towards Integrating Distributed Energy Resources and Storage Devices in Smart Grid

PubMed Central

Xu, Guobin; Yu, Wei; Griffith, David; Golmie, Nada; Moulema, Paul

2017-01-01

Internet of Things (IoT) provides a generic infrastructure for different applications to integrate information communication techniques with physical components to achieve automatic data collection, transmission, exchange, and computation. The smart grid, as one of typical applications supported by IoT, denoted as a re-engineering and a modernization of the traditional power grid, aims to provide reliable, secure, and efficient energy transmission and distribution to consumers. How to effectively integrate distributed (renewable) energy resources and storage devices to satisfy the energy service requirements of users, while minimizing the power generation and transmission cost, remains a highly pressing challenge in the smart grid. To address this challenge and assess the effectiveness of integrating distributed energy resources and storage devices, in this paper we develop a theoretical framework to model and analyze three types of power grid systems: the power grid with only bulk energy generators, the power grid with distributed energy resources, and the power grid with both distributed energy resources and storage devices. Based on the metrics of the power cumulative cost and the service reliability to users, we formally model and analyze the impact of integrating distributed energy resources and storage devices in the power grid. We also use the concept of network calculus, which has been traditionally used for carrying out traffic engineering in computer networks, to derive the bounds of both power supply and user demand to achieve a high service reliability to users. Through an extensive performance evaluation, our data shows that integrating distributed energy resources conjointly with energy storage devices can reduce generation costs, smooth the curve of bulk power generation over time, reduce bulk power generation and power distribution losses, and provide a sustainable service reliability to users in the power grid1. PMID:29354654

Twelve Principles for Green Energy Storage in Grid Applications.

PubMed

Arbabzadeh, Maryam; Johnson, Jeremiah X; Keoleian, Gregory A; Rasmussen, Paul G; Thompson, Levi T

2016-01-19

The introduction of energy storage technologies to the grid could enable greater integration of renewables, improve system resilience and reliability, and offer cost effective alternatives to transmission and distribution upgrades. The integration of energy storage systems into the electrical grid can lead to different environmental outcomes based on the grid application, the existing generation mix, and the demand. Given this complexity, a framework is needed to systematically inform design and technology selection about the environmental impacts that emerge when considering energy storage options to improve sustainability performance of the grid. To achieve this, 12 fundamental principles specific to the design and grid application of energy storage systems are developed to inform policy makers, designers, and operators. The principles are grouped into three categories: (1) system integration for grid applications, (2) the maintenance and operation of energy storage, and (3) the design of energy storage systems. We illustrate the application of each principle through examples published in the academic literature, illustrative calculations, and a case study with an off-grid application of vanadium redox flow batteries (VRFBs). In addition, trade-offs that can emerge between principles are highlighted.

Optimal Operation Method of Smart House by Controllable Loads based on Smart Grid Topology

NASA Astrophysics Data System (ADS)

Yoza, Akihiro; Uchida, Kosuke; Yona, Atsushi; Senju, Tomonobu

2013-08-01

From the perspective of global warming suppression and depletion of energy resources, renewable energy such as wind generation (WG) and photovoltaic generation (PV) are getting attention in distribution systems. Additionally, all electrification apartment house or residence such as DC smart house have increased in recent years. However, due to fluctuating power from renewable energy sources and loads, supply-demand balancing fluctuations of power system become problematic. Therefore, "smart grid" has become very popular in the worldwide. This article presents a methodology for optimal operation of a smart grid to minimize the interconnection point power flow fluctuations. To achieve the proposed optimal operation, we use distributed controllable loads such as battery and heat pump. By minimizing the interconnection point power flow fluctuations, it is possible to reduce the maximum electric power consumption and the electric cost. This system consists of photovoltaics generator, heat pump, battery, solar collector, and load. In order to verify the effectiveness of the proposed system, MATLAB is used in simulations.

Dispersed solar thermal generation employing parabolic dish-electric transport with field modulated generator systems

NASA Technical Reports Server (NTRS)

Ramakumar, R.; Bahrami, K.

1981-01-01

This paper discusses the application of field modulated generator systems (FMGS) to dispersed solar-thermal-electric generation from a parabolic dish field with electric transport. Each solar generation unit is rated at 15 kWe and the power generated by an array of such units is electrically collected for insertion into an existing utility grid. Such an approach appears to be most suitable when the heat engine rotational speeds are high (greater than 6000 r/min) and, in particular, if they are operated in the variable speed mode and if utility-grade a.c. is required for direct insertion into the grid without an intermediate electric energy storage and reconversion system. Predictions of overall efficiencies based on conservative efficiency figures for the FMGS are in the range of 25 per cent and should be encouraging to those involved in the development of cost-effective dispersed solar thermal power systems.

Energy Systems Integration News - September 2016 | Energy Systems

Science.gov Websites

, Smarter Grid Solutions demonstrated a new distributed energy resources (DER) software control platform utility interconnections require distributed generation (DG) devices to disconnect from the grid during OpenFMB distributed applications on the microgrid test site to locally optimize renewable energy resources

Grid Modeling Tools | Grid Modernization | NREL

Science.gov Websites

integrates primary frequency response (turbine governor control) with secondary frequency response (automatic generation control). It simulates the power system dynamic response in full time spectrum with variable time control model places special emphasis on electric power systems with high penetrations of renewable

OVERGRID: A Unified Overset Grid Generation Graphical Interface

NASA Technical Reports Server (NTRS)

Chan, William M.; Akien, Edwin W. (Technical Monitor)

1999-01-01

This paper presents a unified graphical interface and gridding strategy for performing overset grid generation. The interface called OVERGRID has been specifically designed to follow an efficient overset gridding strategy, and contains general grid manipulation capabilities as well as modules that are specifically suited for overset grids. General grid utilities include functions for grid redistribution, smoothing, concatenation, extraction, extrapolation, projection, and many others. Modules specially tailored for overset grids include a seam curve extractor, hyperbolic and algebraic surface grid generators, a hyperbolic volume grid generator, and a Cartesian box grid generator, Grid visualization is achieved using OpenGL while widgets are constructed with Tcl/Tk. The software is portable between various platforms from UNIX workstations to personal computers.

DC Linked Hybrid Generation System with an Energy Storage Device including a Photo-Voltaic Generation and a Gas Engine Cogeneration for Residential Houses

NASA Astrophysics Data System (ADS)

Lung, Chienru; Miyake, Shota; Kakigano, Hiroaki; Miura, Yushi; Ise, Toshifumi; Momose, Toshinari; Hayakawa, Hideki

For the past few years, a hybrid generation system including solar panel and gas cogeneration is being used for residential houses. Solar panels can generate electronic power at daytime; meanwhile, it cannot generate electronic power at night time. But the power consumption of residential houses usually peaks in the evening. The gas engine cogeneration system can generate electronic power without such a restriction, and it also can generate heat power to warm up house or to produce hot water. In this paper, we propose the solar panel and gas engine co-generation hybrid system with an energy storage device that is combined by dc bus. If a black out occurs, the system still can supply electronic power for special house loads. We propose the control scheme for the system which are related with the charging level of the energy storage device, the voltage of the utility grid which can be applied both grid connected and stand alone operation. Finally, we carried out some experiments to demonstrate the system operation and calculation for loss estimation.

VOLTTRON - An Intelligent Agent Platform for the Smart Grid

ScienceCinema

None

2018-05-16

The distributed nature of the Smart Grid, such as responsive loads, solar and wind generation, and automation in the distribution system present a complex environment not easily controlled in a centralized manner.

A Study on Grid-Square Statistics Based Estimation of Regional Electricity Demand and Regional Potential Capacity of Distributed Generators

NASA Astrophysics Data System (ADS)

Kato, Takeyoshi; Sugimoto, Hiroyuki; Suzuoki, Yasuo

We established a procedure for estimating regional electricity demand and regional potential capacity of distributed generators (DGs) by using a grid square statistics data set. A photovoltaic power system (PV system) for residential use and a co-generation system (CGS) for both residential and commercial use were taken into account. As an example, the result regarding Aichi prefecture was presented in this paper. The statistical data of the number of households by family-type and the number of employees by business category for about 4000 grid-square with 1km × 1km area was used to estimate the floor space or the electricity demand distribution. The rooftop area available for installing PV systems was also estimated with the grid-square statistics data set. Considering the relation between a capacity of existing CGS and a scale-index of building where CGS is installed, the potential capacity of CGS was estimated for three business categories, i.e. hotel, hospital, store. In some regions, the potential capacity of PV systems was estimated to be about 10,000kW/km2, which corresponds to the density of the existing area with intensive installation of PV systems. Finally, we discussed the ratio of regional potential capacity of DGs to regional maximum electricity demand for deducing the appropriate capacity of DGs in the model of future electricity distribution system.

Impact of Considering 110 kV Grid Structures on the Congestion Management in the German Transmission Grid

NASA Astrophysics Data System (ADS)

Hoffrichter, André; Barrios, Hans; Massmann, Janek; Venkataramanachar, Bhavasagar; Schnettler, Armin

2018-02-01

The structural changes in the European energy system lead to an increase of renewable energy sources that are primarily connected to the distribution grid. Hence the stationary analysis of the transmission grid and the regionalization of generation capacities are strongly influenced by subordinate grid structures. To quantify the impact on the congestion management in the German transmission grid, a 110 kV grid model is derived using publicly available data delivered by Open Street Map and integrated into an existing model of the European transmission grid. Power flow and redispatch simulations are performed for three different regionalization methods and grid configurations. The results show a significant impact of the 110 kV system and prove an overestimation of power flows in the transmission grid when neglecting subordinate grids. Thus, the redispatch volume in Germany to dissolve bottlenecks in case of N-1 contingencies decreases by 38 % when considering the 110 kV grid.

Electrically heated particulate filter enhanced ignition strategy

DOEpatents

Gonze, Eugene V; Paratore, Jr., Michael J

2012-10-23

An exhaust system that processes exhaust generated by an engine is provided. The system generally includes a particulate filter (PF) that filters particulates from the exhaust wherein an upstream end of the PF receives exhaust from the engine. A grid of electrically resistive material is applied to an exterior upstream surface of the PF and selectively heats exhaust passing through the grid to initiate combustion of particulates within the PF. A catalyst coating applied to at least one of the PF and the grid. A control module estimates a temperature of the grid and controls the engine to produce a desired exhaust product to increase the temperature of the grid.

A Geometry Based Infra-Structure for Computational Analysis and Design

NASA Technical Reports Server (NTRS)

Haimes, Robert

1998-01-01

The computational steps traditionally taken for most engineering analysis suites (computational fluid dynamics (CFD), structural analysis, heat transfer and etc.) are: (1) Surface Generation -- usually by employing a Computer Assisted Design (CAD) system; (2) Grid Generation -- preparing the volume for the simulation; (3) Flow Solver -- producing the results at the specified operational point; (4) Post-processing Visualization -- interactively attempting to understand the results. For structural analysis, integrated systems can be obtained from a number of commercial vendors. These vendors couple directly to a number of CAD systems and are executed from within the CAD Graphical User Interface (GUI). It should be noted that the structural analysis problem is more tractable than CFD; there are fewer mesh topologies used and the grids are not as fine (this problem space does not have the length scaling issues of fluids). For CFD, these steps have worked well in the past for simple steady-state simulations at the expense of much user interaction. The data was transmitted between phases via files. In most cases, the output from a CAD system could go to Initial Graphics Exchange Specification (IGES) or Standard Exchange Program (STEP) files. The output from Grid Generators and Solvers do not really have standards though there are a couple of file formats that can be used for a subset of the gridding (i.e. PLOT3D data formats). The user would have to patch up the data or translate from one format to another to move to the next step. Sometimes this could take days. Specifically the problems with this procedure are:(1) File based -- Information flows from one step to the next via data files with formats specified for that procedure. File standards, when they exist, are wholly inadequate. For example, geometry from CAD systems (transmitted via IGES files) is defined as disjoint surfaces and curves (as well as masses of other information of no interest for the Grid Generator). This is particularly onerous for modern CAD systems based on solid modeling. The part was a proper solid and in the translation to IGES has lost this important characteristic. STEP is another standard for CAD data that exists and supports the concept of a solid. The problem with STEP is that a solid modeling geometry kernel is required to query and manipulate the data within this type of file. (2) 'Good' Geometry. A bottleneck in getting results from a solver is the construction of proper geometry to be fed to the grid generator. With 'good' geometry a grid can be constructed in tens of minutes (even with a complex configuration) using unstructured techniques. Adroit multi-block methods are not far behind. This means that a million node steady-state solution can be computed on the order of hours (using current high performance computers) starting from this 'good' geometry. Unfortunately, the geometry usually transmitted from the CAD system is not 'good' in the grid generator sense. The grid generator needs smooth closed solid geometry. It can take a week (or more) of interaction with the CAD output (sometimes by hand) before the process can begin. One way Communication. (3) One-way Communication -- All information travels on from one phase to the next. This makes procedures like node adaptation difficult when attempting to add or move nodes that sit on bounding surfaces (when the actual surface data has been lost after the grid generation phase). Until this process can be automated, more complex problems such as multi-disciplinary analysis or using the above procedure for design becomes prohibitive. There is also no way to easily deal with this system in a modular manner. One can only replace the grid generator, for example, if the software reads and writes the same files. Instead of the serial approach to analysis as described above, CAPRI takes a geometry centric approach. This makes the actual geometry (not a discretized version) accessible to all phases of the analysis. The connection to the geometry is made through an Application Programming Interface (API) and NOT a file system. This API isolates the top-level applications (grid generators, solvers and visualization components) from the geometry engine. Also this allows the replacement of one geometry kernel with another, without effecting these top-level applications. For example, if UniGraphics is used as the CAD package then Parasolid (UG's own geometry engine) can be used for all geometric queries so that no solid geometry information is lost in a translation. This is much better than STEP because when the data is queried, the same software is executed as used in the CAD system. Therefore, one analyzes the exact part that is in the CAD system. CAPRI uses the same idea as the commercial structural analysis codes but does not specify control. Software components of the CAD system are used, but the analysis suite, not the CAD operator, specifies the control of the software session. This also means that the license issues (may be) minimized and individuals need not have to know how to operate a CAD system in order to run the suite.

Distributed Energy Systems Integration and Demand Optimization for Autonomous Operations and Electric Grid Transactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghatikar, Girish; Mashayekh, Salman; Stadler, Michael

Distributed power systems in the U.S. and globally are evolving to provide reliable and clean energy to consumers. In California, existing regulations require significant increases in renewable generation, as well as identification of customer-side distributed energy resources (DER) controls, communication technologies, and standards for interconnection with the electric grid systems. As DER deployment expands, customer-side DER control and optimization will be critical for system flexibility and demand response (DR) participation, which improves the economic viability of DER systems. Current DER systems integration and communication challenges include leveraging the existing DER and DR technology and systems infrastructure, and enabling optimized cost,more » energy and carbon choices for customers to deploy interoperable grid transactions and renewable energy systems at scale. Our paper presents a cost-effective solution to these challenges by exploring communication technologies and information models for DER system integration and interoperability. This system uses open standards and optimization models for resource planning based on dynamic-pricing notifications and autonomous operations within various domains of the smart grid energy system. It identifies architectures and customer engagement strategies in dynamic DR pricing transactions to generate feedback information models for load flexibility, load profiles, and participation schedules. The models are tested at a real site in California—Fort Hunter Liggett (FHL). Furthermore, our results for FHL show that the model fits within the existing and new DR business models and networked systems for transactive energy concepts. Integrated energy systems, communication networks, and modeling tools that coordinate supply-side networks and DER will enable electric grid system operators to use DER for grid transactions in an integrated system.« less

Smart Grid Development Issues for Terrestrial and Space Applications

NASA Technical Reports Server (NTRS)

Soeder, James F.

2011-01-01

The development of the so called Smart Grid has as many definitions as individuals working in the area. Based on the technology or technologies that are of interest, be it high speed communication, renewable generation, smart meters, energy storage, advanced sensors, etc. they can become the individual defining characteristic of the Smart Grid. In reality the smart grid encompasses all of these items and quite at bit more. This discussion attempts to look at what the needs are for the grid of the future, such as the issues of increased power flow capability, use of renewable energy, increased security and efficiency and common power and data standards. It also shows how many of these issues are common with the needs of NASA for future exploration programs. A common theme to address both terrestrial and space exploration issues is to develop micro-grids that advertise the ability to enable the load leveling of large power generation facilities. However, for microgrids to realize their promise there needs to a holistic systems approach to their development and integration. The overall system integration issues are presented along with potential solution methodologies.

Smart Grid Development Issues for Terrestrial and Space Applications

NASA Technical Reports Server (NTRS)

Soeder, James F.

2014-01-01

The development of the so called Smart Grid has as many definitions as individuals working in the area. Based on the technology or technologies that are of interest, be it high speed communication, renewable generation, smart meters, energy storage, advanced sensors, etc. they can become the individual defining characteristic of the Smart Grid. In reality the smart grid encompasses all of these items and quite at bit more. This discussion attempts to look at what the needs are for the grid of the future, such as the issues of increased power flow capability, use of renewable energy, increased security and efficiency and common power and data standards. It also shows how many of these issues are common with the needs of NASA for future exploration programs. A common theme to address both terrestrial and space exploration issues is to develop micro-grids that advertise the ability to enable the load leveling of large power generation facilities. However, for microgrids to realize their promise there needs to a holistic systems approach to their development and integration. The overall system integration issues are presented along with potential solution methodologies.

How to Integrate Variable Power Source into a Power Grid

NASA Astrophysics Data System (ADS)

Asano, Hiroshi

This paper discusses how to integrate variable power source such as wind power and photovoltaic generation into a power grid. The intermittent renewable generation is expected to penetrate for less carbon intensive power supply system, but it causes voltage control problem in the distribution system, and supply-demand imbalance problem in a whole power system. Cooperative control of customers' energy storage equipment such as water heater with storage tank for reducing inverse power flow from the roof-top PV system, the operation technique using a battery system and the solar radiation forecast for stabilizing output of variable generation, smart charging of plug-in hybrid electric vehicles for load frequency control (LFC), and other methods to integrate variable power source with improving social benefits are surveyed.

Enhanced power quality based single phase photovoltaic distributed generation system

NASA Astrophysics Data System (ADS)

Panda, Aurobinda; Pathak, M. K.; Srivastava, S. P.

2016-08-01

This article presents a novel control strategy for a 1-ϕ 2-level grid-tie photovoltaic (PV) inverter to enhance the power quality (PQ) of a PV distributed generation (PVDG) system. The objective is to obtain the maximum benefits from the grid-tie PV inverter by introducing current harmonics as well as reactive power compensation schemes in its control strategy, thereby controlling the PV inverter to achieve multiple functions in the PVDG system such as: (1) active power flow control between the PV inverter and the grid, (2) reactive power compensation, and (3) grid current harmonics compensation. A PQ enhancement controller (PQEC) has been designed to achieve the aforementioned objectives. The issue of underutilisation of the PV inverter in nighttime has also been addressed in this article and for the optimal use of the system; the PV inverter is used as a shunt active power filter in nighttime. A prototype model of the proposed system is developed in the laboratory, to validate the effectiveness of the control scheme, and is tested with the help of the dSPACE DS1104 platform.

Harmonic analysis and suppression in hybrid wind & PV solar system

NASA Astrophysics Data System (ADS)

Gupta, Tripti; Namekar, Swapnil

2018-04-01

The growing demand of electricity has led to produce power through non-conventional source of energy such as solar energy, wind energy, hydro power, energy through biogas and biomass etc. Hybrid system is taken to complement the shortcoming of either sources of energy. The proposed system is grid connected hybrid wind and solar system. A 2.1 MW Doubly fed Induction Generator (DFIG) has been taken for analysis of wind farm whose rotor part is connected to two back-to-back converters. A 250 KW Photovoltaic (PV) array taken to analyze solar farm where inverter is required to convert power from DC to AC since electricity generated through solar PV is in the form of DC. Stability and reliability of the system is very important when the system is grid connected. Harmonics is the major Power quality issue which degrades the quality of power at load side. Harmonics in hybrid system arise through the use of power conversion unit. The other causes of harmonics are fluctuation in wind speed and solar irradiance. The power delivered to grid must be free from harmonics and within the limits specified by Indian grid codes. In proposed work, harmonic analysis of the hybrid system is performed in Electrical Transient Analysis program (ETAP) and single tuned harmonic filter is designed to maintain the utility grid harmonics within limits.

Enhancements to the GRIDGEN structured grid generation system for internal and external flow applications

NASA Technical Reports Server (NTRS)

Steinbrenner, John P.; Chawner, John R.

1992-01-01

GRIDGEN is a government domain software package for interactive generation of multiple block grids around general configurations. Though it has been freely available since 1989, it has not been widely embraced by the internal flow community due to a misconception that it was designed for external flow use only. In reality GRIDGEN has always worked for internal flow applications, and GRIDGEN ongoing enhancements are increasing the quality of and efficiency with which grids for external and internal flow problems may be constructed. The software consists of four codes used to perform the four steps of the grid generation process. GRIDBLOCK is first used to decompose the flow domain into a collection of component blocks and then to establish interblock connections and flow solver boundary conditions. GRIDGEN2D is then used to generate surface grids on the outer shell of each component block. GRIDGEN3D generates grid points on the interior of each block, and finally GRIDVUE3D is used to inspect the resulting multiple block grid. Three of these codes (GRIDBLOCK, GRIDGEN2D, and GRIDVUE3D) are highly interactive and graphical in nature, and currently run on Silicon Graphics, Inc., and IBM RS/6000 workstations. The lone batch code (GRIDGEN3D) may be run on any of several Unix based platforms. Surface grid generation in GRIDGEN2D is being improved with the addition of higher order surface definitions (NURBS and parametric surfaces input in IGES format and bicubic surfaces input in PATRAN Neutral File format) and double precision mathematics. In addition, two types of automation have been added to GRIDGEN2D that reduce the learning curve slope for new users and eliminate work for experienced users. Volume grid generation using GRIDGEN3D has been improved via the addition of an advanced hybrid control function formulation that provides both orthogonality and clustering control at the block faces and clustering control on the block interior.

Impedance-Based Stability Analysis in Grid Interconnection Impact Study Owing to the Increased Adoption of Converter-Interfaced Generators

DOE PAGES

Cho, Youngho; Hur, Kyeon; Kang, Yong; ...

2017-09-08

This study investigates the emerging harmonic stability concerns to be addressed by grid planners in generation interconnection studies, owing to the increased adoption of renewable energy resources connected to the grid via power electronic converters. The wideband and high-frequency electromagnetic transient (EMT) characteristics of these converter-interfaced generators (CIGs) and their interaction with the grid impedance are not accurately captured in the typical dynamic studies conducted by grid planners. This paper thus identifies the desired components to be studied and subsequently develops a practical process for integrating a new CIG into a grid with the existing CIGs. The steps of thismore » process are as follows: the impedance equation of a CIG using its control dynamics and an interface filter to the grid, for example, an LCL filter (inductor-capacitor-inductor type), is developed; an equivalent impedance model including the existing CIGs nearby and the grid observed from the point of common coupling are derived; the system stability for credible operating scenarios is assessed. Detailed EMT simulations validate the accuracy of the impedance models and stability assessment for various connection scenarios. Here, by complementing the conventional EMT simulation studies, the proposed analytical approach enables grid planners to identify critical design parameters for seamlessly integrating a new CIG and ensuring the reliability of the grid.« less

Mechanics of Flapping Flight: Analytical Formulations of Unsteady Aerodynamics, Kinematic Optimization, Flight Dynamics, and Control

NASA Astrophysics Data System (ADS)

Taneja, Jayant Kumar

Electricity is an indispensable commodity to modern society, yet it is delivered via a grid architecture that remains largely unchanged over the past century. A host of factors are conspiring to topple this dated yet venerated design: developments in renewable electricity generation technology, policies to reduce greenhouse gas emissions, and advances in information technology for managing energy systems. Modern electric grids are emerging as complex distributed systems in which a portfolio of power generation resources, often incorporating fluctuating renewable resources such as wind and solar, must be managed dynamically to meet uncontrolled, time-varying demand. Uncertainty in both supply and demand makes control of modern electric grids fundamentally more challenging, and growing portfolios of renewables exacerbate the challenge. We study three electricity grids: the state of California, the province of Ontario, and the country of Germany. To understand the effects of increasing renewables, we develop a methodology to scale renewables penetration. Analyzing these grids yields key insights about rigid limits to renewables penetration and their implications in meeting long-term emissions targets. We argue that to achieve deep penetration of renewables, the operational model of the grid must be inverted, changing the paradigm from load-following supplies to supply-following loads. To alleviate the challenge of supply-demand matching on deeply renewable grids, we first examine well-known techniques, including altering management of existing supply resources, employing utility-scale energy storage, targeting energy efficiency improvements, and exercising basic demand-side management. Then, we create several instantiations of supply-following loads -- including refrigerators, heating and cooling systems, and laptop computers -- by employing a combination of sensor networks, advanced control techniques, and enhanced energy storage. We examine the capacity of each load for supply-following and study the behaviors of populations of these loads, assessing their potential at various levels of deployment throughout the California electricity grid. Using combinations of supply-following strategies, we can reduce peak natural gas generation by 19% on a model of the California grid with 60% renewables. We then assess remaining variability on this deeply renewable grid incorporating supply-following loads, characterizing additional capabilities needed to ensure supply-demand matching in future sustainable electricity grids.

CPV hybrid system in ISFOC building, first results

NASA Astrophysics Data System (ADS)

Trujillo, Pablo; Alamillo, César; Gil, Eduardo; de la Rubia, Óscar; Martínez, María; Rubio, Francisca; Cadavid, Andros; Navarro, José; Hillenbrand, Sascha; Ballesteros-Sánchez, Isabel; Castillo-Cagigal, Manuel; Masa-Bote, Daniel; Matallanas, Eduardo; Caamaño-Martín, Estefanía; Gutiérrez, Álvaro

2012-10-01

PV Off-Grid systems have demonstrated to be a good solution for the electrification of remote areas [1]. A hybrid system is one kind of these systems. The principal characteristic is that it uses PV as the main generator and has a backup power supply, like a diesel generator, for instance, that is used when the CPV generation is not enough to meet demand. To study the use of CPV in these systems, ISFOC has installed a demonstration hybrid system at its headquarters. This hybrid system uses CPV technology as main generator and the utility grid as the backup generator. A group of batteries have been mounted as well to store the remaining energy from the CPV generator when nedeed. The energy flows are managed by a SMA system based on Sunny Island inverters and a Multicluster-Box (figure 1). The Load is the air-conditioning system of the building, as it has a consumption profile higher than the CPV generator and can be controlled by software [2]. The first results of this system, as well as the first chances of improvement, as the need of a bigger CPV generator and a better management of the energy stored in the batteries, are presented in this paper.

Method of grid generation

DOEpatents

Barnette, Daniel W.

2002-01-01

The present invention provides a method of grid generation that uses the geometry of the problem space and the governing relations to generate a grid. The method can generate a grid with minimized discretization errors, and with minimal user interaction. The method of the present invention comprises assigning grid cell locations so that, when the governing relations are discretized using the grid, at least some of the discretization errors are substantially zero. Conventional grid generation is driven by the problem space geometry; grid generation according to the present invention is driven by problem space geometry and by governing relations. The present invention accordingly can provide two significant benefits: more efficient and accurate modeling since discretization errors are minimized, and reduced cost grid generation since less human interaction is required.

Integrated assessment of water-power grid systems under changing climate

NASA Astrophysics Data System (ADS)

Yan, E.; Zhou, Z.; Betrie, G.

2017-12-01

Energy and water systems are intrinsically interconnected. Due to an increase in climate variability and extreme weather events, interdependency between these two systems has been recently intensified resulting significant impacts on both systems and energy output. To address this challenge, an Integrated Water-Energy Systems Assessment Framework (IWESAF) is being developed to integrate multiple existing or developed models from various sectors. In this presentation, we are focusing on recent improvement in model development of thermoelectric power plant water use simulator, power grid operation and cost optimization model, and model integration that facilitate interaction among water and electricity generation under extreme climate events. A process based thermoelectric power water use simulator includes heat-balance, climate, and cooling system modules that account for power plant characteristics, fuel types, and cooling technology. The model is validated with more than 800 power plants of fossil-fired, nuclear and gas-turbine power plants with different cooling systems. The power grid operation and cost optimization model was implemented for a selected regional in the Midwest. The case study will be demonstrated to evaluate the sensitivity and resilience of thermoelectricity generation and power grid under various climate and hydrologic extremes and potential economic consequences.

Automatic structured grid generation using Gridgen (some restrictions apply)

NASA Technical Reports Server (NTRS)

Chawner, John R.; Steinbrenner, John P.

1995-01-01

The authors have noticed in the recent grid generation literature an emphasis on the automation of structured grid generation. The motivation behind such work is clear; grid generation is easily the most despised task in the grid-analyze-visualize triad of computational analysis (CA). However, because grid generation is closely coupled to both the design and analysis software and because quantitative measures of grid quality are lacking, 'push button' grid generation usually results in a compromise between speed, control, and quality. Overt emphasis on automation obscures the substantive issues of providing users with flexible tools for generating and modifying high quality grids in a design environment. In support of this paper's tongue-in-cheek title, many features of the Gridgen software are described. Gridgen is by no stretch of the imagination an automatic grid generator. Despite this fact, the code does utilize many automation techniques that permit interesting regenerative features.

Comparative analysis of existing models for power-grid synchronization

NASA Astrophysics Data System (ADS)

Nishikawa, Takashi; Motter, Adilson E.

2015-01-01

The dynamics of power-grid networks is becoming an increasingly active area of research within the physics and network science communities. The results from such studies are typically insightful and illustrative, but are often based on simplifying assumptions that can be either difficult to assess or not fully justified for realistic applications. Here we perform a comprehensive comparative analysis of three leading models recently used to study synchronization dynamics in power-grid networks—a fundamental problem of practical significance given that frequency synchronization of all power generators in the same interconnection is a necessary condition for a power grid to operate. We show that each of these models can be derived from first principles within a common framework based on the classical model of a generator, thereby clarifying all assumptions involved. This framework allows us to view power grids as complex networks of coupled second-order phase oscillators with both forcing and damping terms. Using simple illustrative examples, test systems, and real power-grid datasets, we study the inherent frequencies of the oscillators as well as their coupling structure, comparing across the different models. We demonstrate, in particular, that if the network structure is not homogeneous, generators with identical parameters need to be modeled as non-identical oscillators in general. We also discuss an approach to estimate the required (dynamical) system parameters that are unavailable in typical power-grid datasets, their use for computing the constants of each of the three models, and an open-source MATLAB toolbox that we provide for these computations.

Coordinated Control of Wind Turbine and Energy Storage System for Reducing Wind Power Fluctuation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muljadi, Eduard; Kim, Chunghun; Chung, Chung Choo

This paper proposes a coordinated control of wind turbine and energy storage system (ESS). Because wind power (WP) is highly dependent on variable wind speed and could induce a severe stability problem to power system especially when the WP has high penetration level. To solve this problem, many power generation corporations or grid operators recently use the ESS. It has very quick response and good performance for reducing the impact of WP fluctuation but has high cost for its installation. Therefore, it is very important to design the control algorithm considering both ESS capacity and grid reliability. Thus, we proposemore » the control algorithm to mitigate the WP fluctuation by using the coordinated control between wind turbine and ESS considering ESS state of charge (SoC) and the WP fluctuation. From deloaded control according to WP fluctuation and ESS SoC management, we can expect the ESS lifespan expansion and improved grid reliability. The effectiveness of the proposed method is validated in MATLAB/Simulink considering power system including both wind turbine generator and conventional generators which react to system frequency deviation.« less

National Assessment of Energy Storage for Grid Balancing and Arbitrage: Phase 1, WECC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kintner-Meyer, Michael CW; Balducci, Patrick J.; Colella, Whitney G.

2012-06-01

To examine the role that energy storage could play in mitigating the impacts of the stochastic variability of wind generation on regional grid operation, the Pacific Northwest National Laboratory (PNNL) examined a hypothetical 2020 grid scenario in which additional wind generation capacity is built to meet renewable portfolio standard targets in the Western Interconnection. PNNL developed a stochastic model for estimating the balancing requirements using historical wind statistics and forecasting error, a detailed engineering model to analyze the dispatch of energy storage and fast-ramping generation devices for estimating size requirements of energy storage and generation systems for meeting new balancingmore » requirements, and financial models for estimating the life-cycle cost of storage and generation systems in addressing the future balancing requirements for sub-regions in the Western Interconnection. Evaluated technologies include combustion turbines, sodium sulfur (Na-S) batteries, lithium ion batteries, pumped-hydro energy storage, compressed air energy storage, flywheels, redox flow batteries, and demand response. Distinct power and energy capacity requirements were estimated for each technology option, and battery size was optimized to minimize costs. Modeling results indicate that in a future power grid with high-penetration of renewables, the most cost competitive technologies for meeting balancing requirements include Na-S batteries and flywheels.« less

On- and off-grid operation of hybrid renewable power plants: When are the economics favorable?

NASA Astrophysics Data System (ADS)

Petrakopoulou, F.; Santana, D.

2016-12-01

Hybrid renewable energy conversion systems offer a good alternative to conventional systems in locations where the extension of the electrical grid is difficult or not economical or where the cost of electricity is high. However, stand-alone operation implies net energy output restrictions (limited to exclusively serve the energy demand of a region), capacity oversizing and large storage facilities. In interconnected areas, on the other hand, the operational restrictions of the power stations change significantly and the efficiencies and costs of renewable technologies become more favorable. In this paper, the operation of three main renewable technologies (CSP, PV and wind) is studied assuming both hybrid and individual operation for both autonomous and inter-connected operation. The case study used is a Mediterranean island of ca. 3,000 inhabitants. Each system is optimized to fully cover the energy demand of the community. In addition, in the on-grid operation cases, it is required that the annual energy generated from the renewable sources is net positive (i.e., the island generates at least as much energy as it uses). It is found that when connected to the grid, hybridization of more than one technology is not required to satisfy the energy demand, as expected. Each of the renewable technologies investigated can satisfy the annual energy demand individually, without significant complications. In addition, the cost of electricity generated with the three studied technologies drops significantly for on-grid applications, when compared to off-grid operation. However, when compared to business-as-usual scenarios in both the on- and off-grid cases, both investigated hybrid and single-technology renewable scenarios are found to be economically viable. A sensitivity analysis reveals the limits of the acceptable costs that make the technologies favorable when compared to conventional alternatives.

Energy Management Challenges and Opportunities with Increased Intermittent Renewable Generation on the California Electrical Grid

NASA Astrophysics Data System (ADS)

Eichman, Joshua David

Renewable resources including wind, solar, geothermal, biomass, hydroelectric, wave and tidal, represent an opportunity for environmentally preferred generation of electricity that also increases energy security and independence. California is very proactive in encouraging the implementation of renewable energy in part through legislation like Assembly Bill 32 and the development and execution of Renewable Portfolio Standards (RPS); however renewable technologies are not without challenges. All renewable resources have some resource limitations, be that from location, capacity, cost or availability. Technologies like wind and solar are intermittent in nature but represent one of the most abundant resources for generating renewable electricity. If RPS goals are to be achieved high levels of intermittent renewables must be considered. This work explores the effects of high penetration of renewables on a grid system, with respect to resource availability and identifies the key challenges from the perspective of the grid to introducing these resources. The HiGRID tool was developed for this analysis because no other tool could explore grid operation, while maintaining system reliability, with a diverse set of renewable resources and a wide array of complementary technologies including: energy efficiency, demand response, energy storage technologies and electric transportation. This tool resolves the hourly operation of conventional generation resources (nuclear, coal, geothermal, natural gas and hydro). The resulting behavior from introducing additional renewable resources and the lifetime costs for each technology is analyzed.

Hardware-in-the-loop grid simulator system and method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fox, John Curtiss; Collins, Edward Randolph; Rigas, Nikolaos

A hardware-in-the-loop (HIL) electrical grid simulation system and method that combines a reactive divider with a variable frequency converter to better mimic and control expected and unexpected parameters in an electrical grid. The invention provides grid simulation in a manner to allow improved testing of variable power generators, such as wind turbines, and their operation once interconnected with an electrical grid in multiple countries. The system further comprises an improved variable fault reactance (reactive divider) capable of providing a variable fault reactance power output to control a voltage profile, therein creating an arbitrary recovery voltage. The system further comprises anmore » improved isolation transformer designed to isolate zero-sequence current from either a primary or secondary winding in a transformer or pass the zero-sequence current from a primary to a secondary winding.« less

Unstructured grid research and use at NASA Lewis Research Center

NASA Technical Reports Server (NTRS)

Potapczuk, Mark G.

1993-01-01

Computational fluid dynamics applications of grid research at LRC include inlets, nozzles, and ducts; turbomachinery; propellers - ducted and unducted; and aircraft icing. Some issues related to internal flow grid generation are resolution requirements on several boundaries, shock resolution vs. grid periodicity, grid spacing at blade/shroud gap, grid generation in turbine blade passages, and grid generation for inlet/nozzle geometries. Aircraft icing grid generation issues include (1) small structures relative to airfoil chord must be resolved; (2) excessive number of grid points in far-field using structured grid; and (3) grid must be recreated as ice shape grows.

Connecting Electric Vehicles to the Grid for Greater Infrastructure

Science.gov Websites

with the grid at the Energy Systems Integration Facility. Photo by Dennis Schroeder, NREL As the market serves as a test bed for assessing various EV charging scenarios. Photo by Dennis Schroeder, NREL back to the grid and essentially serve as a mobile power generator. Photo by Dennis Schroeder, NREL

Fuzzy logic, PSO based fuzzy logic algorithm and current controls comparative for grid-connected hybrid system

NASA Astrophysics Data System (ADS)

Borni, A.; Abdelkrim, T.; Zaghba, L.; Bouchakour, A.; Lakhdari, A.; Zarour, L.

2017-02-01

In this paper the model of a grid connected hybrid system is presented. The hybrid system includes a variable speed wind turbine controlled by aFuzzy MPPT control, and a photovoltaic generator controlled with PSO Fuzzy MPPT control to compensate the power fluctuations caused by the wind in a short and long term, the inverter currents injected to the grid is controlled by a decoupled PI current control. In the first phase, we start by modeling of the conversion system components; the wind system is consisted of a turbine coupled to a gearless permanent magnet generator (PMG), the AC/DC and DC-DC (Boost) converter are responsible to feed the electric energy produced by the PMG to the DC-link. The solar system consists of a photovoltaic generator (GPV) connected to a DC/DC boost converter controlled by a PSO fuzzy MPPT control to extract at any moment the maximum available power at the GPV terminals, the system is based on maximum utilization of both of sources because of their complementary. At the end. The active power reached to the DC-link is injected to the grid through a DC/AC inverter, this function is achieved by controlling the DC bus voltage to keep it constant and close to its reference value, The simulation studies have been performed using Matlab/Simulink. It can be concluded that a good control system performance can be achieved.

Integrating Variable Renewable Energy - Russia

DOE Office of Scientific and Technical Information (OSTI.GOV)

To foster sustainable, low-emission development, many countries are establishing ambitious renewable energy targets for their electricity supply. Because solar and wind tend to be more variable and uncertain than conventional sources, meeting these targets will involve changes to power system planning and operations. Grid integration is the practice of developing efficient ways to deliver variable renewable energy (VRE) to the grid. Good integration methods maximize the cost-effectiveness of incorporating VRE into the power system while maintaining or increasing system stability and reliability. When considering grid integration, policy makers, regulators, and system operators consider a variety of issues, which can bemore » organized into four broad topics: New Renewable Energy Generation, New Transmission, Increased System Flexibility, Planning for a High RE Future. This is a Russian-language translation of Integrating Variable Renewable Energy into the Grid: Key Issues, Greening the Grid, originally published in English in May 2015.« less

Tuned grid generation with ICEM CFD

NASA Technical Reports Server (NTRS)

Wulf, Armin; Akdag, Vedat

1995-01-01

ICEM CFD is a CAD based grid generation package that supports multiblock structured, unstructured tetrahedral and unstructured hexahedral grids. Major development efforts have been spent to extend ICEM CFD's multiblock structured and hexahedral unstructured grid generation capabilities. The modules added are: a parametric grid generation module and a semi-automatic hexahedral grid generation module. A fully automatic version of the hexahedral grid generation module for around a set of predefined objects in rectilinear enclosures has been developed. These modules will be presented and the procedures used will be described, and examples will be discussed.

Modeling Framework and Validation of a Smart Grid and Demand Response System for Wind Power Integration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Broeer, Torsten; Fuller, Jason C.; Tuffner, Francis K.

2014-01-31

Electricity generation from wind power and other renewable energy sources is increasing, and their variability introduces new challenges to the power system. The emergence of smart grid technologies in recent years has seen a paradigm shift in redefining the electrical system of the future, in which controlled response of the demand side is used to balance fluctuations and intermittencies from the generation side. This paper presents a modeling framework for an integrated electricity system where loads become an additional resource. The agent-based model represents a smart grid power system integrating generators, transmission, distribution, loads and market. The model incorporates generatormore » and load controllers, allowing suppliers and demanders to bid into a Real-Time Pricing (RTP) electricity market. The modeling framework is applied to represent a physical demonstration project conducted on the Olympic Peninsula, Washington, USA, and validation simulations are performed using actual dynamic data. Wind power is then introduced into the power generation mix illustrating the potential of demand response to mitigate the impact of wind power variability, primarily through thermostatically controlled loads. The results also indicate that effective implementation of Demand Response (DR) to assist integration of variable renewable energy resources requires a diversity of loads to ensure functionality of the overall system.« less

Research on LLCL Filtering Grid - Connected inverter under the Control of PFI

NASA Astrophysics Data System (ADS)

Li, Ren-qing; Zong, Ke-yong; Wang, Yan-ping; Li, Yang; Zhang, Jing

2018-03-01

This passage puts forward a kind of LLCL inverter which is based on the proportional feedback integral(PFI) control so as so satisfy the request of the grid-current outputed by the renewable energy generation system. The passage builds the topological graph of grid-connected inverter and makes an analysis of principle of linear superposition aims to reveal the essence of the problem of steady-state error that exists in proportional integral control. We use LLCL filter and the method of passive damping to solve the problem of resonant peak. We make simulation of the grid system with the software named MATLAB/Simulink. The result shows that the grid current enters steady state quickly and in the same time, which has the identical phase and frequency of grid-voltage. The harmonic content in grid current satisfies the request of grid standard.

Power management and frequency regulation for microgrid and smart grid: A real-time demand response approach

NASA Astrophysics Data System (ADS)

Pourmousavi Kani, Seyyed Ali

Future power systems (known as smart grid) will experience a high penetration level of variable distributed energy resources to bring abundant, affordable, clean, efficient, and reliable electric power to all consumers. However, it might suffer from the uncertain and variable nature of these generations in terms of reliability and especially providing required balancing reserves. In the current power system structure, balancing reserves (provided by spinning and non-spinning power generation units) usually are provided by conventional fossil-fueled power plants. However, such power plants are not the favorite option for the smart grid because of their low efficiency, high amount of emissions, and expensive capital investments on transmission and distribution facilities, to name a few. Providing regulation services in the presence of variable distributed energy resources would be even more difficult for islanded microgrids. The impact and effectiveness of demand response are still not clear at the distribution and transmission levels. In other words, there is no solid research reported in the literature on the evaluation of the impact of DR on power system dynamic performance. In order to address these issues, a real-time demand response approach along with real-time power management (specifically for microgrids) is proposed in this research. The real-time demand response solution is utilized at the transmission (through load-frequency control model) and distribution level (both in the islanded and grid-tied modes) to provide effective and fast regulation services for the stable operation of the power system. Then, multiple real-time power management algorithms for grid-tied and islanded microgrids are proposed to economically and effectively operate microgrids. Extensive dynamic modeling of generation, storage, and load as well as different controller design are considered and developed throughout this research to provide appropriate models and simulation environment to evaluate the effectiveness of the proposed methodologies. Simulation results revealed the effectiveness of the proposed methods in providing balancing reserves and microgrids' economic and stable operation. The proposed tools and approaches can significantly enhance the application of microgrids and demand response in the smart grid era. They will also help to increase the penetration level of variable distributed generation resources in the smart grid.

Hyperbolic Prismatic Grid Generation and Solution of Euler Equations on Prismatic Grids

NASA Technical Reports Server (NTRS)

Pandya, S. A.; Chattot, JJ; Hafez, M. M.; Kutler, Paul (Technical Monitor)

1994-01-01

A hyperbolic grid generation method is used to generate prismatic grids and an approach using prismatic grids to solve the Euler equations is presented. The theory of the stability and feasibility of the hyperbolic grid generation method is presented. The hyperbolic grid generation method of Steger et al for structured grids is applied to a three dimensional triangularized surface definition to generate a grid that is unstructured on each successive layer. The grid, however, retains structure in the body-normal direction and has a computational cell shaped like a triangular prism. In order to take advantage of the structure in the normal direction, a finite-volume scheme that treats the unknowns along the normal direction implicitly is introduced and the flow over a sphere is simulated.

Adapting a commercial power system simulator for smart grid based system study and vulnerability assessment

NASA Astrophysics Data System (ADS)

Navaratne, Uditha Sudheera

The smart grid is the future of the power grid. Smart meters and the associated network play a major role in the distributed system of the smart grid. Advance Metering Infrastructure (AMI) can enhance the reliability of the grid, generate efficient energy management opportunities and many innovations around the future smart grid. These innovations involve intense research not only on the AMI network itself but as also on the influence an AMI network can have upon the rest of the power grid. This research describes a smart meter testbed with hardware in loop that can facilitate future research in an AMI network. The smart meters in the testbed were developed such that their functionality can be customized to simulate any given scenario such as integrating new hardware components into a smart meter or developing new encryption algorithms in firmware. These smart meters were integrated into the power system simulator to simulate the power flow variation in the power grid on different AMI activities. Each smart meter in the network also provides a communication interface to the home area network. This research delivers a testbed for emulating the AMI activities and monitoring their effect on the smart grid.

Two methods for damping torsional vibrations in DFIG-based wind generators using power converters

NASA Astrophysics Data System (ADS)

Zhao, Zuyi; Lu, Yupu; Xie, Da; Yu, Songtao; Wu, Wangping

2017-01-01

This paper proposes novel damping control algorithms by using static synchronous compensator (STATCOM) and energy storage system (ESS) to damp torsional vibrations in doubly fed induction generator (DFIG) based wind turbine systems. It first analyses the operating characteristics of STATCOM and ESS for regulating power variations to increase grid voltage stability. Then, new control strategies for STATCOM and ESS are introduced to damp the vibrations. It is followed by illustration of their effectiveness to damp the drive train torsional vibrations of wind turbines, which can be caused by grid disturbances, such as voltage sags and frequency fluctuations. Results suggest that STATCOM is a promising technology to mitigate the torsional vibrations caused by grid voltage sags. By contrast, the ESS connected to the point of common coupling (PCC) of wind turbine systems shows even obvious advantages because of its capability of absorbing/releasing both active and reactive power. It can thus be concluded that STATCOM is useful for stabilizing power system voltage fluctuations, and ESS is more effective both in regulating PCC voltage fluctuations and damping torsional vibrations caused by grid voltage frequency fluctuations.

Coordinated control of wind generation and energy storage for power system frequency regulation

NASA Astrophysics Data System (ADS)

Baone, Chaitanya Ashok

Large-scale centralized synchronous generators have long been the primary actors in exercising active power and frequency control, and much of the existing grid control framework is predicated upon their dynamic terminal characteristics. Important among these characteristics is the inertia of such generators. These play key roles in determining the electromechanical stability of the electric power grid. Modern wind generator systems are partially or fully connected to the grid through power electronic interfaces, and hence do not present the same level of inertial coupling. The absence of inertial frequency response from modern wind generator systems is a topic of growing concern in power engineering practice, as the penetration of wind generation is expected to grow dramatically in the next few years. Solutions proposed in the literature have sought to address this problem by seeking to mimic the inherent inertial response characteristics of traditional synchronous generators via control loops added to wind generators. Recent literature has raised concerns regarding this approach, and the work here will further examine its shortcomings, motivating approaches that seek to optimally design for the characteristics of the equipment exercising the control, rather than forcing new technologies to mimic the characteristics of synchronous machines. In particular, this work will develop a new approach to power system frequency regulation, with features suited to distributed energy storage devices such as grid-scale batteries and wind turbine speed and blade pitch control. The dynamic characteristics of these new technologies are treated along with existing mechanisms, such as synchronous machine governor control, to develop a comprehensive multi-input control design approach. To make the method practically feasible for geographically distributed power systems, an observer-based distributed control design utilizing phasor measurement unit (PMU) signals along with local measurements is developed. In addition to the system-wide objective of frequency regulation, a local objective of reducing the wind turbine drivetrain stress is considered. Also, an algorithm is proposed to characterize the modal degrees of controllability and observability on a subspace of critical modes of the system, so that the most effective sensor and actuator locations to be used in the control design can be found.

Compounded effects of heat waves and droughts over the Western Electricity Grid: spatio-temporal scales of impacts and predictability toward mitigation and adaptation.

NASA Astrophysics Data System (ADS)

Voisin, N.; Kintner-Meyer, M.; Skaggs, R.; Xie, Y.; Wu, D.; Nguyen, T. B.; Fu, T.; Zhou, T.

2016-12-01

Heat waves and droughts are projected to be more frequent and intense. We have seen in the past the effects of each of those extreme climate events on electricity demand and constrained electricity generation, challenging power system operations. Our aim here is to understand the compounding effects under historical conditions. We present a benchmark of Western US grid performance under 55 years of historical climate, and including droughts, using 2010-level of water demand and water management infrastructure, and 2010-level of electricity grid infrastructure and operations. We leverage CMIP5 historical hydrology simulations and force a large scale river routing- reservoir model with 2010-level sectoral water demands. The regulated flow at each water-dependent generating plants is processed to adjust water-dependent electricity generation parameterization in a production cost model, that represents 2010-level power system operations with hourly energy demand of 2010. The resulting benchmark includes a risk distribution of several grid performance metrics (unserved energy, production cost, carbon emission) as a function of inter-annual variability in regional water availability and predictability using large scale climate oscillations. In the second part of the presentation, we describe an approach to map historical heat waves onto this benchmark grid performance using a building energy demand model. The impact of the heat waves, combined with the impact of droughts, is explored at multiple scales to understand the compounding effects. Vulnerabilities of the power generation and transmission systems are highlighted to guide future adaptation.

Valuation of Electric Power System Services and Technologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kintner-Meyer, Michael C. W.; Homer, Juliet S.; Balducci, Patrick J.

Accurate valuation of existing and new technologies and grid services has been recognized to be important to stimulate investment in grid modernization. Clear, transparent, and accepted methods for estimating the total value (i.e., total benefits minus cost) of grid technologies and services are necessary for decision makers to make informed decisions. This applies to home owners interested in distributed energy technologies, as well as to service providers offering new demand response services, and utility executives evaluating best investment strategies to meet their service obligation. However, current valuation methods lack consistency, methodological rigor, and often the capabilities to identify and quantifymore » multiple benefits of grid assets or new and innovative services. Distributed grid assets often have multiple benefits that are difficult to quantify because of the locational context in which they operate. The value is temporally, operationally, and spatially specific. It varies widely by distribution systems, transmission network topology, and the composition of the generation mix. The Electric Power Research Institute (EPRI) recently established a benefit-cost framework that proposes a process for estimating multiple benefits of distributed energy resources (DERs) and the associated cost. This document proposes an extension of this endeavor that offers a generalizable framework for valuation that quantifies the broad set of values for a wide range of technologies (including energy efficiency options, distributed resources, transmission, and generation) as well as policy options that affect all aspects of the entire generation and delivery system of the electricity infrastructure. The extension includes a comprehensive valuation framework of monetizable and non-monetizable benefits of new technologies and services beyond the traditional reliability objectives. The benefits are characterized into the following categories: sustainability, affordability, and security, flexibility, and resilience. This document defines the elements of a generic valuation framework and process as well as system properties and metrics by which value streams can be derived. The valuation process can be applied to determine the value on the margin of incremental system changes. This process is typically performed when estimating the value of a particular project (e.g., value of a merchant generator, or a distributed photovoltaic (PV) rooftop installation). Alternatively, the framework can be used when a widespread change in the grid operation, generation mix, or transmission topology is to be valued. In this case a comprehensive system analysis is required.« less

A New Control Method to Mitigate Power Fluctuations for Grid Integrated PV/Wind Hybrid Power System Using Ultracapacitors

NASA Astrophysics Data System (ADS)

Jayalakshmi, N. S.; Gaonkar, D. N.

2016-08-01

The output power obtained from solar-wind hybrid system fluctuates with changes in weather conditions. These power fluctuations cause adverse effects on the voltage, frequency and transient stability of the utility grid. In this paper, a control method is presented for power smoothing of grid integrated PV/wind hybrid system using ultracapacitors in a DC coupled structure. The power fluctuations of hybrid system are mitigated and smoothed power is supplied to the utility grid. In this work both photovoltaic (PV) panels and the wind generator are controlled to operate at their maximum power point. The grid side inverter control strategy presented in this paper maintains DC link voltage constant while injecting power to the grid at unity power factor considering different operating conditions. Actual solar irradiation and wind speed data are used in this study to evaluate the performance of the developed system using MATLAB/Simulink software. The simulation results show that output power fluctuations of solar-wind hybrid system can be significantly mitigated using the ultracapacitor based storage system.

A Systematic Multi-Time Scale Solution for Regional Power Grid Operation

NASA Astrophysics Data System (ADS)

Zhu, W. J.; Liu, Z. G.; Cheng, T.; Hu, B. Q.; Liu, X. Z.; Zhou, Y. F.

2017-10-01

Many aspects need to be taken into consideration in a regional grid while making schedule plans. In this paper, a systematic multi-time scale solution for regional power grid operation considering large scale renewable energy integration and Ultra High Voltage (UHV) power transmission is proposed. In the time scale aspect, we discuss the problem from month, week, day-ahead, within-day to day-behind, and the system also contains multiple generator types including thermal units, hydro-plants, wind turbines and pumped storage stations. The 9 subsystems of the scheduling system are described, and their functions and relationships are elaborated. The proposed system has been constructed in a provincial power grid in Central China, and the operation results further verified the effectiveness of the system.

Designing for Wide-Area Situation Awareness in Future Power Grid Operations

NASA Astrophysics Data System (ADS)

Tran, Fiona F.

Power grid operation uncertainty and complexity continue to increase with the rise of electricity market deregulation, renewable generation, and interconnectedness between multiple jurisdictions. Human operators need appropriate wide-area visualizations to help them monitor system status to ensure reliable operation of the interconnected power grid. We observed transmission operations at a control centre, conducted critical incident interviews, and led focus group sessions with operators. The results informed a Work Domain Analysis of power grid operations, which in turn informed an Ecological Interface Design concept for wide-area monitoring. I validated design concepts through tabletop discussions and a usability evaluation with operators, earning a mean System Usability Scale score of 77 out of 90. The design concepts aim to support an operator's complete and accurate understanding of the power grid state, which operators increasingly require due to the critical nature of power grid infrastructure and growing sources of system uncertainty.

Geometry modeling and multi-block grid generation for turbomachinery configurations

NASA Technical Reports Server (NTRS)

Shih, Ming H.; Soni, Bharat K.

1992-01-01

An interactive 3D grid generation code, Turbomachinery Interactive Grid genERation (TIGER), was developed for general turbomachinery configurations. TIGER features the automatic generation of multi-block structured grids around multiple blade rows for either internal, external, or internal-external turbomachinery flow fields. Utilization of the Bezier's curves achieves a smooth grid and better orthogonality. TIGER generates the algebraic grid automatically based on geometric information provided by its built-in pseudo-AI algorithm. However, due to the large variation of turbomachinery configurations, this initial grid may not always be as good as desired. TIGER therefore provides graphical user interactions during the process which allow the user to design, modify, as well as manipulate the grid, including the capability of elliptic surface grid generation.

A procedure for automating CFD simulations of an inlet-bleed problem

NASA Technical Reports Server (NTRS)

Chyu, Wei J.; Rimlinger, Mark J.; Shih, Tom I.-P.

1995-01-01

A procedure was developed to improve the turn-around time for computational fluid dynamics (CFD) simulations of an inlet-bleed problem involving oblique shock-wave/boundary-layer interactions on a flat plate with bleed into a plenum through one or more circular holes. This procedure is embodied in a preprocessor called AUTOMAT. With AUTOMAT, once data for the geometry and flow conditions have been specified (either interactively or via a namelist), it will automatically generate all input files needed to perform a three-dimensional Navier-Stokes simulation of the prescribed inlet-bleed problem by using the PEGASUS and OVERFLOW codes. The input files automatically generated by AUTOMAT include those for the grid system and those for the initial and boundary conditions. The grid systems automatically generated by AUTOMAT are multi-block structured grids of the overlapping type. Results obtained by using AUTOMAT are presented to illustrate its capability.

Direct torque control method applied to the WECS based on the PMSG and controlled with backstepping approach

NASA Astrophysics Data System (ADS)

Errami, Youssef; Obbadi, Abdellatif; Sahnoun, Smail; Ouassaid, Mohammed; Maaroufi, Mohamed

2018-05-01

This paper proposes a Direct Torque Control (DTC) method for Wind Power System (WPS) based Permanent Magnet Synchronous Generator (PMSG) and Backstepping approach. In this work, generator side and grid-side converter with filter are used as the interface between the wind turbine and grid. Backstepping approach demonstrates great performance in complicated nonlinear systems control such as WPS. So, the control method combines the DTC to achieve Maximum Power Point Tracking (MPPT) and Backstepping approach to sustain the DC-bus voltage and to regulate the grid-side power factor. In addition, control strategy is developed in the sense of Lyapunov stability theorem for the WPS. Simulation results using MATLAB/Simulink validate the effectiveness of the proposed controllers.

Using adaptive grid in modeling rocket nozzle flow

NASA Technical Reports Server (NTRS)

Chow, Alan S.; Jin, Kang-Ren

1992-01-01

The mechanical behavior of a rocket motor internal flow field results in a system of nonlinear partial differential equations which cannot be solved analytically. However, this system of equations called the Navier-Stokes equations can be solved numerically. The accuracy and the convergence of the solution of the system of equations will depend largely on how precisely the sharp gradients in the domain of interest can be resolved. With the advances in computer technology, more sophisticated algorithms are available to improve the accuracy and convergence of the solutions. An adaptive grid generation is one of the schemes which can be incorporated into the algorithm to enhance the capability of numerical modeling. It is equivalent to putting intelligence into the algorithm to optimize the use of computer memory. With this scheme, the finite difference domain of the flow field called the grid does neither have to be very fine nor strategically placed at the location of sharp gradients. The grid is self adapting as the solution evolves. This scheme significantly improves the methodology of solving flow problems in rocket nozzles by taking the refinement part of grid generation out of the hands of computational fluid dynamics (CFD) specialists and place it into the computer algorithm itself.

Design and implementation of grid multi-scroll fractional-order chaotic attractors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Liping, E-mail: lip-chenhut@126.com; Pan, Wei; Wu, Ranchao

2016-08-15

This paper proposes a novel approach for generating multi-scroll chaotic attractors in multi-directions for fractional-order (FO) systems. The stair nonlinear function series and the saturated nonlinear function are combined to extend equilibrium points with index 2 in a new FO linear system. With the help of stability theory of FO systems, stability of its equilibrium points is analyzed, and the chaotic behaviors are validated through phase portraits, Lyapunov exponents, and Poincaré section. Choosing the order 0.96 as an example, a circuit for generating 2-D grid multiscroll chaotic attractors is designed, and 2-D 9 × 9 grid FO attractors are observed at most.more » Numerical simulations and circuit experimental results show that the method is feasible and the designed circuit is correct.« less

Modeling complex aquifer systems: a case study in Baton Rouge, Louisiana (USA)

NASA Astrophysics Data System (ADS)

Pham, Hai V.; Tsai, Frank T.-C.

2017-05-01

This study targets two challenges in groundwater model development: grid generation and model calibration for aquifer systems that are fluvial in origin. Realistic hydrostratigraphy can be developed using a large quantity of well log data to capture the complexity of an aquifer system. However, generating valid groundwater model grids to be consistent with the complex hydrostratigraphy is non-trivial. Model calibration can also become intractable for groundwater models that intend to match the complex hydrostratigraphy. This study uses the Baton Rouge aquifer system, Louisiana (USA), to illustrate a technical need to cope with grid generation and model calibration issues. A grid generation technique is introduced based on indicator kriging to interpolate 583 wireline well logs in the Baton Rouge area to derive a hydrostratigraphic architecture with fine vertical discretization. Then, an upscaling procedure is developed to determine a groundwater model structure with 162 layers that captures facies geometry in the hydrostratigraphic architecture. To handle model calibration for such a large model, this study utilizes a derivative-free optimization method in parallel computing to complete parameter estimation in a few months. The constructed hydrostratigraphy indicates the Baton Rouge aquifer system is fluvial in origin. The calibration result indicates hydraulic conductivity for Miocene sands is higher than that for Pliocene to Holocene sands and indicates the Baton Rouge fault and the Denham Springs-Scotlandville fault to be low-permeability leaky aquifers. The modeling result shows significantly low groundwater level in the "2,000-foot" sand due to heavy pumping, indicating potential groundwater upward flow from the "2,400-foot" sand.

Impacts of P-f & Q-V Droop Control on MicroGrids Transient Stability

NASA Astrophysics Data System (ADS)

Zhao-xia, Xiao; Hong-wei, Fang

Impacts of P-f & Q-V droop control on MicroGrid transient stability was investigated with a wind unit of asynchronous generator in the MicroGrid. The system frequency stability was explored when the motor load starts and its load power changes, and faults of different types and different locations occurs. The simulations were done by PSCAD/EMTDC.

Reactive Power Compensation Using an Energy Management System

DTIC Science & Technology

2014-09-01

bulk power grid or independent of the grid in islanded mode using various DG sources ( photovoltaic panels, fuel cells, gas generators, batteries...developed in order to forecast the system’s response to both capacitive and inductive power demands on the grid. The process was then confirmed in a...NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited REACTIVE POWER

Boosting CSP Production with Thermal Energy Storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denholm, P.; Mehos, M.

2012-06-01

Combining concentrating solar power (CSP) with thermal energy storage shows promise for increasing grid flexibility by providing firm system capacity with a high ramp rate and acceptable part-load operation. When backed by energy storage capability, CSP can supplement photovoltaics by adding generation from solar resources during periods of low solar insolation. The falling cost of solar photovoltaic (PV) - generated electricity has led to a rapid increase in the deployment of PV and projections that PV could play a significant role in the future U.S. electric sector. The solar resource itself is virtually unlimited; however, the actual contribution of PVmore » electricity is limited by several factors related to the current grid. The first is the limited coincidence between the solar resource and normal electricity demand patterns. The second is the limited flexibility of conventional generators to accommodate this highly variable generation resource. At high penetration of solar generation, increased grid flexibility will be needed to fully utilize the variable and uncertain output from PV generation and to shift energy production to periods of high demand or reduced solar output. Energy storage is one way to increase grid flexibility, and many storage options are available or under development. In this article, however, we consider a technology already beginning to be used at scale - thermal energy storage (TES) deployed with concentrating solar power (CSP). PV and CSP are both deployable in areas of high direct normal irradiance such as the U.S. Southwest. The role of these two technologies is dependent on their costs and relative value, including how their value to the grid changes as a function of what percentage of total generation they contribute to the grid, and how they may actually work together to increase overall usefulness of the solar resource. Both PV and CSP use solar energy to generate electricity. A key difference is the ability of CSP to utilize high-efficiency TES, which turns CSP into a partially dispatchable resource. The addition of TES produces additional value by shifting the delivery of solar energy to periods of peak demand, providing firm capacity and ancillary services, and reducing integration challenges. Given the dispatchability of CSP enabled by TES, it is possible that PV and CSP are at least partially complementary. The dispatchability of CSP with TES can enable higher overall penetration of the grid by solar energy by providing solar-generated electricity during periods of cloudy weather or at night, when PV-generated power is unavailable. Such systems also have the potential to improve grid flexibility, thereby enabling greater penetration of PV energy (and other variable generation sources such as wind) than if PV were deployed without CSP.« less

Energy solutions in rural Africa: mapping electrification costs of distributed solar and diesel generation versus grid extension

NASA Astrophysics Data System (ADS)

Szabó, S.; Bódis, K.; Huld, T.; Moner-Girona, M.

2011-07-01

Three rural electrification options are analysed showing the cost optimal conditions for a sustainable energy development applying renewable energy sources in Africa. A spatial electricity cost model has been designed to point out whether diesel generators, photovoltaic systems or extension of the grid are the least-cost option in off-grid areas. The resulting mapping application offers support to decide in which regions the communities could be electrified either within the grid or in an isolated mini-grid. Donor programs and National Rural Electrification Agencies (or equivalent governmental departments) could use this type of delineation for their program boundaries and then could use the local optimization tools adapted to the prevailing parameters. The views expressed in this paper are those of the authors and do not necessarily represent European Commission and UNEP policy.

Adaptive control paradigm for photovoltaic and solid oxide fuel cell in a grid-integrated hybrid renewable energy system.

PubMed

Mumtaz, Sidra; Khan, Laiq

2017-01-01

The hybrid power system (HPS) is an emerging power generation scheme due to the plentiful availability of renewable energy sources. Renewable energy sources are characterized as highly intermittent in nature due to meteorological conditions, while the domestic load also behaves in a quite uncertain manner. In this scenario, to maintain the balance between generation and load, the development of an intelligent and adaptive control algorithm has preoccupied power engineers and researchers. This paper proposes a Hermite wavelet embedded NeuroFuzzy indirect adaptive MPPT (maximum power point tracking) control of photovoltaic (PV) systems to extract maximum power and a Hermite wavelet incorporated NeuroFuzzy indirect adaptive control of Solid Oxide Fuel Cells (SOFC) to obtain a swift response in a grid-connected hybrid power system. A comprehensive simulation testbed for a grid-connected hybrid power system (wind turbine, PV cells, SOFC, electrolyzer, battery storage system, supercapacitor (SC), micro-turbine (MT) and domestic load) is developed in Matlab/Simulink. The robustness and superiority of the proposed indirect adaptive control paradigm are evaluated through simulation results in a grid-connected hybrid power system testbed by comparison with a conventional PI (proportional and integral) control system. The simulation results verify the effectiveness of the proposed control paradigm.

Adaptive control paradigm for photovoltaic and solid oxide fuel cell in a grid-integrated hybrid renewable energy system

PubMed Central

Khan, Laiq

2017-01-01

The hybrid power system (HPS) is an emerging power generation scheme due to the plentiful availability of renewable energy sources. Renewable energy sources are characterized as highly intermittent in nature due to meteorological conditions, while the domestic load also behaves in a quite uncertain manner. In this scenario, to maintain the balance between generation and load, the development of an intelligent and adaptive control algorithm has preoccupied power engineers and researchers. This paper proposes a Hermite wavelet embedded NeuroFuzzy indirect adaptive MPPT (maximum power point tracking) control of photovoltaic (PV) systems to extract maximum power and a Hermite wavelet incorporated NeuroFuzzy indirect adaptive control of Solid Oxide Fuel Cells (SOFC) to obtain a swift response in a grid-connected hybrid power system. A comprehensive simulation testbed for a grid-connected hybrid power system (wind turbine, PV cells, SOFC, electrolyzer, battery storage system, supercapacitor (SC), micro-turbine (MT) and domestic load) is developed in Matlab/Simulink. The robustness and superiority of the proposed indirect adaptive control paradigm are evaluated through simulation results in a grid-connected hybrid power system testbed by comparison with a conventional PI (proportional and integral) control system. The simulation results verify the effectiveness of the proposed control paradigm. PMID:28329015

Climate and Water Vulnerability of the US Electricity Grid Under High Penetrations of Renewable Energy

NASA Astrophysics Data System (ADS)

Macknick, J.; Miara, A.; O'Connell, M.; Vorosmarty, C. J.; Newmark, R. L.

2017-12-01

The US power sector is highly dependent upon water resources for reliable operations, primarily for thermoelectric cooling and hydropower technologies. Changes in the availability and temperature of water resources can limit electricity generation and cause outages at power plants, which substantially affect grid-level operational decisions. While the effects of water variability and climate changes on individual power plants are well documented, prior studies have not identified the significance of these impacts at the regional systems-level at which the grid operates, including whether there are risks for large-scale blackouts, brownouts, or increases in production costs. Adequately assessing electric grid system-level impacts requires detailed power sector modeling tools that can incorporate electric transmission infrastructure, capacity reserves, and other grid characteristics. Here, we present for the first time, a study of how climate and water variability affect operations of the power sector, considering different electricity sector configurations (low vs. high renewable) and environmental regulations. We use a case study of the US Eastern Interconnection, building off the Eastern Renewable Generation Integration Study (ERGIS) that explored operational challenges of high penetrations of renewable energy on the grid. We evaluate climate-water constraints on individual power plants, using the Thermoelectric Power and Thermal Pollution (TP2M) model coupled with the PLEXOS electricity production cost model, in the context of broader electricity grid operations. Using a five minute time step for future years, we analyze scenarios of 10% to 30% renewable energy penetration along with considerations of river temperature regulations to compare the cost, performance, and reliability tradeoffs of water-dependent thermoelectric generation and variable renewable energy technologies under climate stresses. This work provides novel insights into the resilience and reliability of different configurations of the US electric grid subject to changing climate conditions.

Interconnection, Integration, and Interactive Impact Analysis of Microgrids and Distribution Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Ning; Wang, Jianhui; Singh, Ravindra

2017-01-01

Distribution management systems (DMSs) are increasingly used by distribution system operators (DSOs) to manage the distribution grid and to monitor the status of both power imported from the transmission grid and power generated locally by a distributed energy resource (DER), to ensure that power flows and voltages along the feeders are maintained within designed limits and that appropriate measures are taken to guarantee service continuity and energy security. When microgrids are deployed and interconnected to the distribution grids, they will have an impact on the operation of the distribution grid. The challenge is to design this interconnection in such amore » way that it enhances the reliability and security of the distribution grid and the loads embedded in the microgrid, while providing economic benefits to all stakeholders, including the microgrid owner and operator and the distribution system operator.« less

Chimera Grid Tools

NASA Technical Reports Server (NTRS)

Chan, William M.; Rogers, Stuart E.; Nash, Steven M.; Buning, Pieter G.; Meakin, Robert

2005-01-01

Chimera Grid Tools (CGT) is a software package for performing computational fluid dynamics (CFD) analysis utilizing the Chimera-overset-grid method. For modeling flows with viscosity about geometrically complex bodies in relative motion, the Chimera-overset-grid method is among the most computationally cost-effective methods for obtaining accurate aerodynamic results. CGT contains a large collection of tools for generating overset grids, preparing inputs for computer programs that solve equations of flow on the grids, and post-processing of flow-solution data. The tools in CGT include grid editing tools, surface-grid-generation tools, volume-grid-generation tools, utility scripts, configuration scripts, and tools for post-processing (including generation of animated images of flows and calculating forces and moments exerted on affected bodies). One of the tools, denoted OVERGRID, is a graphical user interface (GUI) that serves to visualize the grids and flow solutions and provides central access to many other tools. The GUI facilitates the generation of grids for a new flow-field configuration. Scripts that follow the grid generation process can then be constructed to mostly automate grid generation for similar configurations. CGT is designed for use in conjunction with a computer-aided-design program that provides the geometry description of the bodies, and a flow-solver program.

Development and Testing of the Glenn Research Center Visitor's Center Grid-Tied Photovoltaic Power System

NASA Technical Reports Server (NTRS)

Eichenberg, Dennis J.

2009-01-01

The NASA Glenn Research Center (GRC) has developed, installed, and tested a 12 kW DC grid-tied photovoltaic (PV) power system at the GRC Visitor s Center. This system utilizes a unique ballast type roof mount for installing the photovoltaic panels on the roof of the Visitor s Center with no alterations or penetrations to the roof. The PV system has generated in excess of 15000 kWh since operation commenced in August 2008. The PV system is providing power to the GRC grid for use by all. Operation of the GRC Visitor s Center PV system has been completely trouble free. A grid-tied PV power system is connected directly to the utility distribution grid. Facility power can be obtained from the utility system as normal. The PV system is synchronized with the utility system to provide power for the facility, and excess power is provided to the utility. The project transfers space technology to terrestrial use via nontraditional partners. GRC personnel glean valuable experience with PV power systems that are directly applicable to various space power systems, and provides valuable space program test data. PV power systems help to reduce harmful emissions and reduce the Nation s dependence on fossil fuels. Power generated by the PV system reduces the GRC utility demand, and the surplus power aids the community. Present global energy concerns reinforce the need for the development of alternative energy systems. Modern PV panels are readily available, reliable, efficient, and economical with a life expectancy of at least 25 years. Modern electronics has been the enabling technology behind grid-tied power systems, making them safe, reliable, efficient, and economical with a life expectancy of at least 25 years. Based upon the success of the GRC Visitor s Center PV system, additional PV power system expansion at GRC is under consideration. The GRC Visitor s Center grid-tied PV power system was successfully designed and developed which served to validate the basic principles described, and the theoretical work that was performed. The report concludes that grid-tied photovoltaic power systems are reliable, maintenance free, long life power systems, and are of significant value to NASA and the community.

An overview of controls research on the NASA Langley Research Center grid

NASA Technical Reports Server (NTRS)

Montgomery, Raymond C.

1987-01-01

The NASA Langley Research Center has assembled a flexible grid on which control systems research can be accomplished on a two-dimensional structure that has many physically distributed sensors and actuators. The grid is a rectangular planar structure that is suspended by two cables attached to one edge so that out of plane vibrations are normal to gravity. There are six torque wheel actuators mounted to it so that torque is produced in the grid plane. Also, there are six rate gyros mounted to sense angular motion in the grid plane and eight accelerometers that measure linear acceleration normal to the grid plane. All components can be relocated to meet specific control system test requirements. Digital, analog, and hybrid control systems capability is provided in the apparatus. To date, research on this grid has been conducted in the areas of system and parameter identification, model estimation, distributed modal control, hierarchical adaptive control, and advanced redundancy management algorithms. The presentation overviews each technique and presents the most significant results generated for each area.

Fault Analysis in a Grid Integrated DFIG Based Wind Energy System with NA CB_P Circuit for Ridethrough Capability and Power Quality Improvement

NASA Astrophysics Data System (ADS)

Swain, Snehaprava; Ray, Pravat Kumar

2016-12-01

In this paper a three phase fault analysis is done on a DFIG based grid integrated wind energy system. A Novel Active Crowbar Protection (NACB_P) system is proposed to enhance the Fault-ride through (FRT) capability of DFIG both for symmetrical as well as unsymmetrical grid faults. Hence improves the power quality of the system. The protection scheme proposed here is designed with a capacitor in series with the resistor unlike the conventional Crowbar (CB) having only resistors. The major function of the capacitor in the protection circuit is to eliminate the ripples generated in the rotor current and to protect the converter as well as the DC-link capacitor. It also compensates reactive power required by the DFIG during fault. Due to these advantages the proposed scheme enhances the FRT capability of the DFIG and also improves the power quality of the whole system. Experimentally the fault analysis is done on a 3hp slip ring induction generator and simulation results are carried out on a 1.7 MVA DFIG based WECS under different types of grid faults in MATLAB/Simulation and functionality of the proposed scheme is verified.

Near-Body Grid Adaption for Overset Grids

NASA Technical Reports Server (NTRS)

Buning, Pieter G.; Pulliam, Thomas H.

2016-01-01

A solution adaption capability for curvilinear near-body grids has been implemented in the OVERFLOW overset grid computational fluid dynamics code. The approach follows closely that used for the Cartesian off-body grids, but inserts refined grids in the computational space of original near-body grids. Refined curvilinear grids are generated using parametric cubic interpolation, with one-sided biasing based on curvature and stretching ratio of the original grid. Sensor functions, grid marking, and solution interpolation tasks are implemented in the same fashion as for off-body grids. A goal-oriented procedure, based on largest error first, is included for controlling growth rate and maximum size of the adapted grid system. The adaption process is almost entirely parallelized using MPI, resulting in a capability suitable for viscous, moving body simulations. Two- and three-dimensional examples are presented.

Transformation of two and three-dimensional regions by elliptic systems

NASA Technical Reports Server (NTRS)

Mastin, C. Wayne

1993-01-01

During this contract period, our work has focused on improvements to elliptic grid generation methods. There are two principle objectives in this project. One objective is to make the elliptic methods more reliable and efficient, and the other is to construct a modular code that can be incorporated into the National Grid Project (NGP), or any other grid generation code. Progress has been made in meeting both of these objectives. The two objectives are actually complementary. As the code development for the NGP progresses, we see many areas where improvements in algorithms can be made.

Description of the F-16XL Geometry and Computational Grids Used in CAWAPI

NASA Technical Reports Server (NTRS)

Boelens, O. J.; Badcock, K. J.; Gortz, S.; Morton, S.; Fritz, W.; Karman, S. L., Jr.; Michal, T.; Lamar, J. E.

2009-01-01

The objective of the Cranked-Arrow Wing Aerodynamics Project International (CAWAPI) was to allow a comprehensive validation of Computational Fluid Dynamics methods against the CAWAP flight database. A major part of this work involved the generation of high-quality computational grids. Prior to the grid generation an IGES file containing the air-tight geometry of the F-16XL aircraft was generated by a cooperation of the CAWAPI partners. Based on this geometry description both structured and unstructured grids have been generated. The baseline structured (multi-block) grid (and a family of derived grids) has been generated by the National Aerospace Laboratory NLR. Although the algorithms used by NLR had become available just before CAWAPI and thus only a limited experience with their application to such a complex configuration had been gained, a grid of good quality was generated well within four weeks. This time compared favourably with that required to produce the unstructured grids in CAWAPI. The baseline all-tetrahedral and hybrid unstructured grids has been generated at NASA Langley Research Center and the USAFA, respectively. To provide more geometrical resolution, trimmed unstructured grids have been generated at EADS-MAS, the UTSimCenter, Boeing Phantom Works and KTH/FOI. All grids generated within the framework of CAWAPI will be discussed in the article. Both results obtained on the structured grids and the unstructured grids showed a significant improvement in agreement with flight test data in comparison with those obtained on the structured multi-block grid used during CAWAP.

The impact of model detail on power grid resilience measures

NASA Astrophysics Data System (ADS)

Auer, S.; Kleis, K.; Schultz, P.; Kurths, J.; Hellmann, F.

2016-05-01

Extreme events are a challenge to natural as well as man-made systems. For critical infrastructure like power grids, we need to understand their resilience against large disturbances. Recently, new measures of the resilience of dynamical systems have been developed in the complex system literature. Basin stability and survivability respectively assess the asymptotic and transient behavior of a system when subjected to arbitrary, localized but large perturbations in frequency and phase. To employ these methods that assess power grid resilience, we need to choose a certain model detail of the power grid. For the grid topology we considered the Scandinavian grid and an ensemble of power grids generated with a random growth model. So far the most popular model that has been studied is the classical swing equation model for the frequency response of generators and motors. In this paper we study a more sophisticated model of synchronous machines that also takes voltage dynamics into account, and compare it to the previously studied model. This model has been found to give an accurate picture of the long term evolution of synchronous machines in the engineering literature for post fault studies. We find evidence that some stable fix points of the swing equation become unstable when we add voltage dynamics. If this occurs the asymptotic behavior of the system can be dramatically altered, and basin stability estimates obtained with the swing equation can be dramatically wrong. We also find that the survivability does not change significantly when taking the voltage dynamics into account. Further, the limit cycle type asymptotic behaviour is strongly correlated with transient voltages that violate typical operational voltage bounds. Thus, transient voltage bounds are dominated by transient frequency bounds and play no large role for realistic parameters.

Fuzzy comprehensive evaluation for grid-connected performance of integrated distributed PV-ES systems

NASA Astrophysics Data System (ADS)

Lv, Z. H.; Li, Q.; Huang, R. W.; Liu, H. M.; Liu, D.

2016-08-01

Based on the discussion about topology structure of integrated distributed photovoltaic (PV) power generation system and energy storage (ES) in single or mixed type, this paper focuses on analyzing grid-connected performance of integrated distributed photovoltaic and energy storage (PV-ES) systems, and proposes a comprehensive evaluation index system. Then a multi-level fuzzy comprehensive evaluation method based on grey correlation degree is proposed, and the calculations for weight matrix and fuzzy matrix are presented step by step. Finally, a distributed integrated PV-ES power generation system connected to a 380 V low voltage distribution network is taken as the example, and some suggestions are made based on the evaluation results.

Contribution of concentrator photovoltaic installations to grid stability and power quality

NASA Astrophysics Data System (ADS)

del Toro García, Xavier; Roncero-Sánchez, Pedro; Torres, Alfonso Parreño; Vázquez, Javier

2012-10-01

Large-scale integration of Photovoltaic (PV) generation systems, including Concentrator Photovoltaic (CPV) technologies, will require the contribution and support of these technologies to the management and stability of the grid. New regulations and grid codes for PV installations in countries such as Spain have recently included dynamic voltage control support during faults. The PV installation must stay connected to the grid during voltage dips and inject reactive power in order to enhance the stability of the system. The existing PV inverter technologies based on the Voltage-Source Converter (VSC) are in general well suited to provide advanced grid-support characteristics. Nevertheless, new advanced control schemes and monitoring techniques will be necessary to meet the most demanding requirements.

Wind Farm Stabilization by using DFIG with Current Controlled Voltage Source Converters Taking Grid Codes into Consideration

NASA Astrophysics Data System (ADS)

Okedu, Kenneth Eloghene; Muyeen, S. M.; Takahashi, Rion; Tamura, Junji

Recent wind farm grid codes require wind generators to ride through voltage sags, which means that normal power production should be re-initiated once the nominal grid voltage is recovered. However, fixed speed wind turbine generator system using induction generator (IG) has the stability problem similar to the step-out phenomenon of a synchronous generator. On the other hand, doubly fed induction generator (DFIG) can control its real and reactive powers independently while being operated in variable speed mode. This paper proposes a new control strategy using DFIGs for stabilizing a wind farm composed of DFIGs and IGs, without incorporating additional FACTS devices. A new current controlled voltage source converter (CC-VSC) scheme is proposed to control the converters of DFIG and the performance is verified by comparing the results with those of voltage controlled voltage source converter (VC-VSC) scheme. Another salient feature of this study is to reduce the number of proportionate integral (PI) controllers used in the rotor side converter without degrading dynamic and transient performances. Moreover, DC-link protection scheme during grid fault can be omitted in the proposed scheme which reduces overall cost of the system. Extensive simulation analyses by using PSCAD/EMTDC are carried out to clarify the effectiveness of the proposed CC-VSC based control scheme of DFIGs.

User's manual for the HYPGEN hyperbolic grid generator and the HGUI graphical user interface

NASA Technical Reports Server (NTRS)

Chan, William M.; Chiu, Ing-Tsau; Buning, Pieter G.

1993-01-01

The HYPGEN program is used to generate a 3-D volume grid over a user-supplied single-block surface grid. This is accomplished by solving the 3-D hyperbolic grid generation equations consisting of two orthogonality relations and one cell volume constraint. In this user manual, the required input files and parameters and output files are described. Guidelines on how to select the input parameters are given. Illustrated examples are provided showing a variety of topologies and geometries that can be treated. HYPGEN can be used in stand-alone mode as a batch program or it can be called from within a graphical user interface HGUI that runs on Silicon Graphics workstations. This user manual provides a description of the menus, buttons, sliders, and typein fields in HGUI for users to enter the parameters needed to run HYPGEN. Instructions are given on how to configure the interface to allow HYPGEN to run either locally or on a faster remote machine through the use of shell scripts on UNIX operating systems. The volume grid generated is copied back to the local machine for visualization using a built-in hook to PLOT3D.

Simulation for Grid Connected Wind Turbines with Fluctuating

NASA Astrophysics Data System (ADS)

Ye, Ying; Fu, Yang; Wei, Shurong

This paper establishes the whole dynamic model of wind turbine generator system which contains the wind speed model and DFIG wind turbines model .A simulation sample based on the mathematical models is built by using MATLAB in this paper. Research are did on the performance characteristics of doubly-fed wind generators (DFIG) which connected to power grid with three-phase ground fault and the disturbance by gust and mixed wind. The capacity of the wind farm is 9MW which consists of doubly-fed wind generators (DFIG). Simulation results demonstrate that the three-phase ground fault occurs on grid side runs less affected on the stability of doubly-fed wind generators. However, as a power source, fluctuations of the wind speed will run a large impact on stability of double-fed wind generators. The results also show that if the two disturbances occur in the meantime, the situation will be very serious.

Fully Automated Single-Zone Elliptic Grid Generation for Mars Science Laboratory (MSL) Aeroshell and Canopy Geometries

NASA Technical Reports Server (NTRS)

kaul, Upender K.

2008-01-01

A procedure for generating smooth uniformly clustered single-zone grids using enhanced elliptic grid generation has been demonstrated here for the Mars Science Laboratory (MSL) geometries such as aeroshell and canopy. The procedure obviates the need for generating multizone grids for such geometries, as reported in the literature. This has been possible because the enhanced elliptic grid generator automatically generates clustered grids without manual prescription of decay parameters needed with the conventional approach. In fact, these decay parameters are calculated as decay functions as part of the solution, and they are not constant over a given boundary. Since these decay functions vary over a given boundary, orthogonal grids near any arbitrary boundary can be clustered automatically without having to break up the boundaries and the corresponding interior domains into various zones for grid generation.

Distributed Energy Systems: Security Implications of the Grid of the Future

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stamber, Kevin L.; Kelic, Andjelka; Taylor, Robert A.

2017-01-01

Distributed Energy Resources (DER) are being added to the nation's electric grid, and as penetration of these resources increases, they have the potential to displace or offset large-scale, capital-intensive, centralized generation. Integration of DER into operation of the traditional electric grid requires automated operational control and communication of DER elements, from system measurement to control hardware and software, in conjunction with a utility's existing automated and human-directed control of other portions of the system. Implementation of DER technologies suggests a number of gaps from both a security and a policy perspective. This page intentionally left blank.

The Design of Connection Solid Oxide Fuel Cell (SOFC) Integrated Grid with Three-Phase Inverter

NASA Astrophysics Data System (ADS)

Darjat; Sulistyo; Triwiyatno, Aris; Thalib, Humaid

2018-03-01

Fuel cell technology is a relatively new energy-saving technology that has the potential to replace conventional energy technologies. Among the different types of generation technologies, fuel cells is the generation technologies considered as a potential source of power generation because it is flexible and can be placed anywhere based distribution system. Modeling of SOFC is done by using Nernst equation. The output power of the fuel cell can be controlled by controlling the flow rate of the fuels used in the process. Three-phase PWM inverter is used to get the form of three-phase voltage which same with the grid. In this paper, the planning and design of the SOFC are connected to the grid.

PSO-Based Smart Grid Application for Sizing and Optimization of Hybrid Renewable Energy Systems

PubMed Central

Mohamed, Mohamed A.; Eltamaly, Ali M.; Alolah, Abdulrahman I.

2016-01-01

This paper introduces an optimal sizing algorithm for a hybrid renewable energy system using smart grid load management application based on the available generation. This algorithm aims to maximize the system energy production and meet the load demand with minimum cost and highest reliability. This system is formed by photovoltaic array, wind turbines, storage batteries, and diesel generator as a backup source of energy. Demand profile shaping as one of the smart grid applications is introduced in this paper using load shifting-based load priority. Particle swarm optimization is used in this algorithm to determine the optimum size of the system components. The results obtained from this algorithm are compared with those from the iterative optimization technique to assess the adequacy of the proposed algorithm. The study in this paper is performed in some of the remote areas in Saudi Arabia and can be expanded to any similar regions around the world. Numerous valuable results are extracted from this study that could help researchers and decision makers. PMID:27513000

PSO-Based Smart Grid Application for Sizing and Optimization of Hybrid Renewable Energy Systems.

PubMed

Mohamed, Mohamed A; Eltamaly, Ali M; Alolah, Abdulrahman I

2016-01-01

This paper introduces an optimal sizing algorithm for a hybrid renewable energy system using smart grid load management application based on the available generation. This algorithm aims to maximize the system energy production and meet the load demand with minimum cost and highest reliability. This system is formed by photovoltaic array, wind turbines, storage batteries, and diesel generator as a backup source of energy. Demand profile shaping as one of the smart grid applications is introduced in this paper using load shifting-based load priority. Particle swarm optimization is used in this algorithm to determine the optimum size of the system components. The results obtained from this algorithm are compared with those from the iterative optimization technique to assess the adequacy of the proposed algorithm. The study in this paper is performed in some of the remote areas in Saudi Arabia and can be expanded to any similar regions around the world. Numerous valuable results are extracted from this study that could help researchers and decision makers.

Demonstration of Active Power Controls by Utility-Scale PV Power Plant in an Island Grid: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gevorgian, Vahan; O'Neill, Barbara

The National Renewable Energy Laboratory (NREL), AES, and the Puerto Rico Electric Power Authority conducted a demonstration project on a utility-scale photovoltaic (PV) plant to test the viability of providing important ancillary services from this facility. As solar generation increases globally, there is a need for innovation and increased operational flexibility. A typical PV power plant consists of multiple power electronic inverters and can contribute to grid stability and reliability through sophisticated 'grid-friendly' controls. In this way, it may mitigate the impact of its variability on the grid and contribute to important system requirements more like traditional generators. In 2015,more » testing was completed on a 20-MW AES plant in Puerto Rico, and a large amount of test data was produced and analyzed that demonstrates the ability of PV power plants to provide various types of new grid-friendly controls. This data showed how active power controls can leverage PV's value from being simply an intermittent energy resource to providing additional ancillary services for an isolated island grid. Specifically, the tests conducted included PV plant participation in automatic generation control, provision of droop response, and fast frequency response.« less

Smart EV Energy Management System to Support Grid Services

NASA Astrophysics Data System (ADS)

Wang, Bin

Under smart grid scenarios, the advanced sensing and metering technologies have been applied to the legacy power grid to improve the system observability and the real-time situational awareness. Meanwhile, there is increasing amount of distributed energy resources (DERs), such as renewable generations, electric vehicles (EVs) and battery energy storage system (BESS), etc., being integrated into the power system. However, the integration of EVs, which can be modeled as controllable mobile energy devices, brings both challenges and opportunities to the grid planning and energy management, due to the intermittency of renewable generation, uncertainties of EV driver behaviors, etc. This dissertation aims to solve the real-time EV energy management problem in order to improve the overall grid efficiency, reliability and economics, using online and predictive optimization strategies. Most of the previous research on EV energy management strategies and algorithms are based on simplified models with unrealistic assumptions that the EV charging behaviors are perfectly known or following known distributions, such as the arriving time, leaving time and energy consumption values, etc. These approaches fail to obtain the optimal solutions in real-time because of the system uncertainties. Moreover, there is lack of data-driven strategy that performs online and predictive scheduling for EV charging behaviors under microgrid scenarios. Therefore, we develop an online predictive EV scheduling framework, considering uncertainties of renewable generation, building load and EV driver behaviors, etc., based on real-world data. A kernel-based estimator is developed to predict the charging session parameters in real-time with improved estimation accuracy. The efficacy of various optimization strategies that are supported by this framework, including valley-filling, cost reduction, event-based control, etc., has been demonstrated. In addition, the existing simulation-based approaches do not consider a variety of practical concerns of implementing such a smart EV energy management system, including the driver preferences, communication protocols, data models, and customized integration of existing standards to provide grid services. Therefore, this dissertation also solves these issues by designing and implementing a scalable system architecture to capture the user preferences, enable multi-layer communication and control, and finally improve the system reliability and interoperability.

Plug-in hybrid electric vehicles as a source of distributed frequency regulation

NASA Astrophysics Data System (ADS)

Mullen, Sara Kathryn

The movement to transform the North American power grid into a smart grid may be accomplished by expanding integrated sensing, communications, and control technologies to include every part of the grid to the point of end-use. Plug-in hybrid electric vehicles (PHEV) provide an opportunity for small-scale distributed storage while they are plugged-in. With large numbers of PHEV and the communications and sensing associated with the smart grid, PHEV could provide ancillary services for the grid. Frequency regulation is an ideal service for PHEV because the duration of supply is short (order of minutes) and it is the highest priced ancillary service on the market offering greater financial returns for vehicle owners. Using Simulink a power system simulator modeling the IEEE 14 Bus System was combined with a model of PHEV charging and the controllers which facilitate vehicle-to-grid (V2G) regulation supply. The system includes a V2G controller for each vehicle which makes regulation supply decisions based on battery state, user preferences, and the recommended level of supply. A PHEV coordinator controller located higher in the system has access to reliable frequency measurements and can determine a suitable local automatic generation control (AGC) raise/lower signal for participating vehicles. A first step implementation of the V2G supply system where battery charging is modulated to provide regulation was developed. The system was simulated following a step change in loading using three scenarios: (1) Central generating units provide frequency regulation, (2) PHEV contribute to primary regulation analogous to generator speed governor control, and (3) PHEV contribute to primary and secondary regulation using an additional integral term in the PHEV control signal. In both cases the additional regulation provided by PHEV reduced the area control error (ACE) compared to the base case. Unique contributions resulting from this work include: (1) Studied PHEV energy systems and limitations on battery charging/discharging, (2) Reviewed standards for interconnection of distributed resources and electric vehicle charging [1], [2], (3) Explored strategies for distributed control of PHEV charging, (4) Developed controllers to accommodate PHEV regulation, and (5) Developed a simulator combining a power system model and PHEV/V2G components.

Electrostatic dust detector

DOEpatents

Skinner, Charles H [Lawrenceville, NJ

2006-05-02

An apparatus for detecting dust in a variety of environments which can include radioactive and other hostile environments both in a vacuum and in a pressurized system. The apparatus consists of a grid coupled to a selected bias voltage. The signal generated when dust impacts and shorts out the grid is electrically filtered, and then analyzed by a signal analyzer which is then sent to a counter. For fine grids a correlation can be developed to relate the number of counts observed to the amount of dust which impacts the grid.

Wind Generators

NASA Technical Reports Server (NTRS)

1989-01-01

When Enerpro, Inc. president, Frank J. Bourbeau, attempted to file a patent on a system for synchronizing a wind generator to the electric utility grid, he discovered Marshall Space Flight Center's Frank Nola's power factor controller. Bourbeau advanced the technology and received a NASA license and a patent for his Auto Synchronous Controller (ASC). The ASC reduces generator "inrush current," which occurs when large generators are abruptly brought on line. It controls voltage so the generator is smoothly connected to the utility grid when it reaches its synchronous speed, protecting the components from inrush current damage. Generator efficiency is also increased in light winds by applying lower than rated voltage. Wind energy is utilized to drive turbines to generate electricity for utility companies.

A Petri Net model for distributed energy system

NASA Astrophysics Data System (ADS)

Konopko, Joanna

2015-12-01

Electrical networks need to evolve to become more intelligent, more flexible and less costly. The smart grid is the next generation power energy, uses two-way flows of electricity and information to create a distributed automated energy delivery network. Building a comprehensive smart grid is a challenge for system protection, optimization and energy efficient. Proper modeling and analysis is needed to build an extensive distributed energy system and intelligent electricity infrastructure. In this paper, the whole model of smart grid have been proposed using Generalized Stochastic Petri Nets (GSPN). The simulation of created model is also explored. The simulation of the model has allowed the analysis of how close the behavior of the model is to the usage of the real smart grid.

Enabling Resiliency Operations across Multiple Microgrids with Grid Friendly Appliance Controllers

DOE PAGES

Schneider, Kevin P.; Tuffner, Frank K.; Elizondo, Marcelo A.; ...

2017-02-16

Changes in economic, technological, and environmental policies are resulting in a re-evaluation of the dependence on large central generation facilities and their associated transmission networks. Emerging concepts of smart communities/cities are examining the potential to leverage cleaner sources of generation, as well as integrating electricity generation with other municipal functions. When grid connected, these generation assets can supplement the existing interconnections with the bulk transmission system, and in the event of an extreme event, they can provide power via a collection of microgrids. To achieve the highest level of resiliency, it may be necessary to conduct switching operations to interconnectmore » individual microgrids. While the interconnection of multiple microgrids can increase the resiliency of the system, the associated switching operations can cause large transients in low inertia microgrids. The combination of low system inertia and IEEE 1547 and 1547a-compliant inverters can prevent multiple microgrids from being interconnected during extreme weather events. This study will present a method of using end-use loads equipped with Grid Friendly™ Appliance controllers to facilitate the switching operations between multiple microgrids; operations that are necessary for optimal operations when islanded for resiliency.« less

Enabling Resiliency Operations across Multiple Microgrids with Grid Friendly Appliance Controllers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, Kevin P.; Tuffner, Frank K.; Elizondo, Marcelo A.

Changes in economic, technological, and environmental policies are resulting in a re-evaluation of the dependence on large central generation facilities and their associated transmission networks. Emerging concepts of smart communities/cities are examining the potential to leverage cleaner sources of generation, as well as integrating electricity generation with other municipal functions. When grid connected, these generation assets can supplement the existing interconnections with the bulk transmission system, and in the event of an extreme event, they can provide power via a collection of microgrids. To achieve the highest level of resiliency, it may be necessary to conduct switching operations to interconnectmore » individual microgrids. While the interconnection of multiple microgrids can increase the resiliency of the system, the associated switching operations can cause large transients in low inertia microgrids. The combination of low system inertia and IEEE 1547 and 1547a-compliant inverters can prevent multiple microgrids from being interconnected during extreme weather events. This study will present a method of using end-use loads equipped with Grid Friendly™ Appliance controllers to facilitate the switching operations between multiple microgrids; operations that are necessary for optimal operations when islanded for resiliency.« less

Analysis and Inverse Design of the HSR Arrow Wing Configuration with Fuselage, Wing, and Flow Through Nacelles

NASA Technical Reports Server (NTRS)

Krist, Steven E.; Bauer, Steven X. S.

1999-01-01

The design process for developing the natural flow wing design on the HSR arrow wing configuration utilized several design tools and analysis methods. Initial fuselage/wing designs were generated with inviscid analysis and optimization methods in conjunction with the natural flow wing design philosophy. A number of designs were generated, satisfying different system constraints. Of the three natural flow wing designs developed, the NFWAc2 configuration is the design which satisfies the constraints utilized by McDonnell Douglas Aerospace (MDA) in developing a series of optimized configurations; a wind tunnel model of the MDA designed OPT5 configuration was constructed and tested. The present paper is concerned with the viscous analysis and inverse design of the arrow wing configurations, including the effects of the installed diverters/nacelles. Analyses were conducted with OVERFLOW, a Navier-Stokes flow solver for overset grids. Inverse designs were conducted with OVERDISC, which couples OVERFLOW with the CDISC inverse design method. An initial system of overset grids was generated for the OPT5 configuration with installed diverters/nacelles. An automated regridding process was then developed to use the OPT5 component grids to create grids for the natural flow wing designs. The inverse design process was initiated using the NFWAc2 configuration as a starting point, eventually culminating in the NFWAc4 design-for which a wind tunnel model was constructed. Due to the time constraints on the design effort, initial analyses and designs were conducted with a fairly coarse grid; subsequent analyses have been conducted on a refined system of grids. Comparisons of the computational results to experiment are provided at the end of this paper.

Research and application of thermal power unit’s load dynamic adjustment based on extraction steam

NASA Astrophysics Data System (ADS)

Li, Jun; Li, Huicong; Li, Weiwei

2018-02-01

The rapid development of heat and power generation in large power plant has caused tremendous constraints on the load adjustment of power grids and power plants. By introducing the thermodynamic system of thermal power unit, the relationship between thermal power extraction steam and unit’s load has analyzed and calculated. The practical application results show that power capability of the unit affected by extraction and it is not conducive to adjust the grid frequency. By monitoring the load adjustment capacity of thermal power units, especially the combined heat and power generating units, the upper and lower limits of the unit load can be dynamically adjusted by the operator on the grid side. The grid regulation and control departments can effectively control the load adjustable intervals of the operating units and provide reliable for the cooperative action of the power grid and power plants, to ensure the safety and stability of the power grid.

The power grid AGC frequency bias coefficient online identification method based on wide area information

NASA Astrophysics Data System (ADS)

Wang, Zian; Li, Shiguang; Yu, Ting

2015-12-01

This paper propose online identification method of regional frequency deviation coefficient based on the analysis of interconnected grid AGC adjustment response mechanism of regional frequency deviation coefficient and the generator online real-time operation state by measured data through PMU, analyze the optimization method of regional frequency deviation coefficient in case of the actual operation state of the power system and achieve a more accurate and efficient automatic generation control in power system. Verify the validity of the online identification method of regional frequency deviation coefficient by establishing the long-term frequency control simulation model of two-regional interconnected power system.

Generation of three-dimensional body-fitted grids by solving hyperbolic partial differential equations

NASA Technical Reports Server (NTRS)

Steger, Joseph L.

1989-01-01

Hyperbolic grid generation procedures are described which have been used in external flow simulations about complex configurations. For many practical applications a single well-ordered (i.e., structured) grid can be used to mesh an entire configuration, in other problems, composite or unstructured grid procedures are needed. Although the hyperbolic partial differential equation grid generation procedure has mainly been utilized to generate structured grids, an extension of the procedure to semiunstructured grids is briefly described. Extensions of the methodology are also described using two-dimensional equations.

Generation of three-dimensional body-fitted grids by solving hyperbolic and parabolic partial differential equations

NASA Technical Reports Server (NTRS)

Steger, Joseph L.

1989-01-01

Hyperbolic grid generation procedures are described which have been used in external flow simulations about complex configurations. For many practical applications a single well-ordered (i.e., structured) grid can be used to mesh an entire configuration, in other problems, composite or unstructured grid procedures are needed. Although the hyperbolic partial differential equation grid generation procedure has mainly been utilized to generate structured grids, extension of the procedure to semiunstructured grids is briefly described. Extensions of the methodology are also described using two-dimensional equations.

Artificial Intelligence In Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Vogel, Alison Andrews

1991-01-01

Paper compares four first-generation artificial-intelligence (Al) software systems for computational fluid dynamics. Includes: Expert Cooling Fan Design System (EXFAN), PAN AIR Knowledge System (PAKS), grid-adaptation program MITOSIS, and Expert Zonal Grid Generation (EZGrid). Focuses on knowledge-based ("expert") software systems. Analyzes intended tasks, kinds of knowledge possessed, magnitude of effort required to codify knowledge, how quickly constructed, performances, and return on investment. On basis of comparison, concludes Al most successful when applied to well-formulated problems solved by classifying or selecting preenumerated solutions. In contrast, application of Al to poorly understood or poorly formulated problems generally results in long development time and large investment of effort, with no guarantee of success.

Evaluation of load flow and grid expansion in a unit-commitment and expansion optimization model SciGRID International Conference on Power Grid Modelling

NASA Astrophysics Data System (ADS)

Senkpiel, Charlotte; Biener, Wolfgang; Shammugam, Shivenes; Längle, Sven

2018-02-01

Energy system models serve as a basis for long term system planning. Joint optimization of electricity generating technologies, storage systems and the electricity grid leads to lower total system cost compared to an approach in which the grid expansion follows a given technology portfolio and their distribution. Modelers often face the problem of finding a good tradeoff between computational time and the level of detail that can be modeled. This paper analyses the differences between a transport model and a DC load flow model to evaluate the validity of using a simple but faster transport model within the system optimization model in terms of system reliability. The main findings in this paper are that a higher regional resolution of a system leads to better results compared to an approach in which regions are clustered as more overloads can be detected. An aggregation of lines between two model regions compared to a line sharp representation has little influence on grid expansion within a system optimizer. In a DC load flow model overloads can be detected in a line sharp case, which is therefore preferred. Overall the regions that need to reinforce the grid are identified within the system optimizer. Finally the paper recommends the usage of a load-flow model to test the validity of the model results.

Novel Control Strategy for Multiple Run-of-the-River Hydro Power Plants to Provide Grid Ancillary Services

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohanpurkar, Manish; Luo, Yusheng; Hovsapian, Rob

Hydropower plant (HPP) generation comprises a considerable portion of bulk electricity generation and is delivered with a low-carbon footprint. In fact, HPP electricity generation provides the largest share from renewable energy resources, which include wind and solar. Increasing penetration levels of wind and solar lead to a lower inertia on the electric grid, which poses stability challenges. In recent years, breakthroughs in energy storage technologies have demonstrated the economic and technical feasibility of extensive deployments of renewable energy resources on electric grids. If integrated with scalable, multi-time-step energy storage so that the total output can be controlled, multiple run-of-the-river (ROR)more » HPPs can be deployed. Although the size of a single energy storage system is much smaller than that of a typical reservoir, the ratings of storages and multiple ROR HPPs approximately equal the rating of a large, conventional HPP. This paper proposes cohesively managing multiple sets of energy storage systems distributed in different locations. This paper also describes the challenges associated with ROR HPP system architecture and operation.« less

Hydroacoustic propagation grids for the CTBT knowledge databaes BBN technical memorandum W1303

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. Angell

1998-05-01

The Hydroacoustic Coverage Assessment Model (HydroCAM) has been used to develop components of the hydroacoustic knowledge database required by operational monitoring systems, particularly the US National Data Center (NDC). The database, which consists of travel time, amplitude correction and travel time standard deviation grids, is planned to support source location, discrimination and estimation functions of the monitoring network. The grids will also be used under the current BBN subcontract to support an analysis of the performance of the International Monitoring System (IMS) and national sensor systems. This report describes the format and contents of the hydroacoustic knowledgebase grids, and themore » procedures and model parameters used to generate these grids. Comparisons between the knowledge grids, measured data and other modeled results are presented to illustrate the strengths and weaknesses of the current approach. A recommended approach for augmenting the knowledge database with a database of expected spectral/waveform characteristics is provided in the final section of the report.« less

Grid-Connected Distributed Generation: Compensation Mechanism Basics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aznar, Alexandra Y; Zinaman, Owen R

2017-10-02

This short report defines compensation mechanisms for grid-connected, behind-the-meter distributed generation (DG) systems as instruments that comprise three core elements: (1) metering and billing arrangements, (2) sell rate design, and (3) retail rate design. This report describes metering and billing arrangements, with some limited discussion of sell rate design. We detail the three possible arrangements for metering and billing of DG: net energy metering (NEM); buy all, sell all; and net billing.

Grid cell spatial tuning reduced following systemic muscarinic receptor blockade

PubMed Central

Newman, Ehren L.; Climer, Jason R.; Hasselmo, Michael E.

2014-01-01

Grid cells of the medial entorhinal cortex exhibit a periodic and stable pattern of spatial tuning that may reflect the output of a path integration system. This grid pattern has been hypothesized to serve as a spatial coordinate system for navigation and memory function. The mechanisms underlying the generation of this characteristic tuning pattern remain poorly understood. Systemic administration of the muscarinic antagonist scopolamine flattens the typically positive correlation between running speed and entorhinal theta frequency in rats. The loss of this neural correlate of velocity, an important signal for the calculation of path integration, raises the question of what influence scopolamine has on the grid cell tuning as a read out of the path integration system. To test this, the spatial tuning properties of grid cells were compared before and after systemic administration of scopolamine as rats completed laps on a circle track for food rewards. The results show that the spatial tuning of the grid cells was reduced following scopolamine administration. The tuning of head direction cells, in contrast, was not reduced by scopolamine. This is the first report to demonstrate a link between cholinergic function and grid cell tuning. This work suggests that the loss of tuning in the grid cell network may underlie the navigational disorientation observed in Alzheimer's patients and elderly individuals with reduced cholinergic tone. PMID:24493379

Torsional vibration characteristic study of the grid-connected DFIG wind turbine

NASA Astrophysics Data System (ADS)

Yu, Songtao; Xie, Da; Wu, Wangping; Gu, Chenghong; Li, Furong

2017-01-01

This paper studies the torsional vibration characteristics of the grid-connected doubly-fed induction generator (DFIG) wind turbine by small signal analysis method. Firstly a detailed small-signal stability union model of the grid-connected DFIG wind turbine is developed, including the mechanical system and electrical system. To study the dynamic characteristic of the blade, gearbox, low speed and high speed shafts, a three mass shaft model for the mechanical system is adopted. At the same time, small signal models of DFIG, the voltage source converter (VSC) and the transmission line of the electrical system are developed respectively. Then, through calculating the eigenvalues of the state matrix A and the corresponding participation factors, the modal analysis is conducted in the shaft torsional vibration issues. And the impact of the system parameters including the series compensation capacitor, the flat-wave reactor, the PI parameters, especially the speed controller of generator rotor on shaft torsional vibration are discussed. The results show that the speed controller strengthens association between the mechanical system and the electrical system, and also produces a low-frequency oscillation mode.

A Taxonomy on Accountability and Privacy Issues in Smart Grids

NASA Astrophysics Data System (ADS)

Naik, Ameya; Shahnasser, Hamid

2017-07-01

Cyber-Physical Systems (CPS) are combinations of computation, networking, and physical processes. Embedded computers and networks monitor control the physical processes, which affect computations and vice versa. Two applications of cyber physical systems include health-care and smart grid. In this paper, we have considered privacy aspects of cyber-physical system applicable to smart grid. Smart grid in collaboration with different stockholders can help in the improvement of power generation, communication, circulation and consumption. The proper management with monitoring feature by customers and utility of energy usage can be done through proper transmission and electricity flow; however cyber vulnerability could be increased due to an increased assimilation and linkage. This paper discusses various frameworks and architectures proposed for achieving accountability in smart grids by addressing privacy issues in Advance Metering Infrastructure (AMI). This paper also highlights additional work needed for accountability in more precise specifications such as uncertainty or ambiguity, indistinct, unmanageability, and undetectably.

Unlocking the potential of smart grid technologies with behavioral science

PubMed Central

Sintov, Nicole D.; Schultz, P. Wesley

2015-01-01

Smart grid systems aim to provide a more stable and adaptable electricity infrastructure, and to maximize energy efficiency. Grid-linked technologies vary widely in form and function, but generally share common potentials: to reduce energy consumption via efficiency and/or curtailment, to shift use to off-peak times of day, and to enable distributed storage and generation options. Although end users are central players in these systems, they are sometimes not central considerations in technology or program design, and in some cases, their motivations for participating in such systems are not fully appreciated. Behavioral science can be instrumental in engaging end-users and maximizing the impact of smart grid technologies. In this paper, we present emerging technologies made possible by a smart grid infrastructure, and for each we highlight ways in which behavioral science can be applied to enhance their impact on energy savings. PMID:25914666

Security and Stability Analysis of Wind Farms Integration into Distribution Network

NASA Astrophysics Data System (ADS)

Guan-yang, Li; Hongzhao, Wang; Guanglei, Li; Yamei, Cheng; Hong-zheng, Liu; Yi, Sun

2017-05-01

With the increasing share of the wind power in the power system, wind power fluctuations will cause obvious negative impacts on weak local grid. This paper firstly establish electromechanical transient simulation model for doubly fed induction wind turbine, then use Matlab/Simulink to achieve power flow calculation and transient simulation of power system including wind farms, the local synchronous generator, load, etc, finally analyze wind power on the impact of the local power grid under typical circumstances. The actual calculated results indicate that wind mutation causes little effect on the power grid, but when the three-phase short circuit fault happens, active power of wind power decreases sharply and the voltage of location of wind power into the grid also drop sharply, finally wind farm split from power system. This situation is not conducive to security and stability of the local power grid. It is necessary to develop security and stability measures in the future.

Unlocking the potential of smart grid technologies with behavioral science.

PubMed

Sintov, Nicole D; Schultz, P Wesley

2015-01-01

Smart grid systems aim to provide a more stable and adaptable electricity infrastructure, and to maximize energy efficiency. Grid-linked technologies vary widely in form and function, but generally share common potentials: to reduce energy consumption via efficiency and/or curtailment, to shift use to off-peak times of day, and to enable distributed storage and generation options. Although end users are central players in these systems, they are sometimes not central considerations in technology or program design, and in some cases, their motivations for participating in such systems are not fully appreciated. Behavioral science can be instrumental in engaging end-users and maximizing the impact of smart grid technologies. In this paper, we present emerging technologies made possible by a smart grid infrastructure, and for each we highlight ways in which behavioral science can be applied to enhance their impact on energy savings.

Unlocking the potential of smart grid technologies with behavioral science

DOE PAGES

Sintov, Nicole D.; Schultz, P. Wesley

2015-04-09

Smart grid systems aim to provide a more stable and adaptable electricity infrastructure, and to maximize energy efficiency. Grid-linked technologies vary widely in form and function, but generally share common potentials: to reduce energy consumption via efficiency and/or curtailment, to shift use to off-peak times of day, and to enable distributed storage and generation options. Although end users are central players in these systems, they are sometimes not central considerations in technology or program design, and in some cases, their motivations for participating in such systems are not fully appreciated. Behavioral science can be instrumental in engaging end-users and maximizingmore » the impact of smart grid technologies. In this study, we present emerging technologies made possible by a smart grid infrastructure, and for each we highlight ways in which behavioral science can be applied to enhance their impact on energy savings.« less

Unlocking the potential of smart grid technologies with behavioral science

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sintov, Nicole D.; Schultz, P. Wesley

Smart grid systems aim to provide a more stable and adaptable electricity infrastructure, and to maximize energy efficiency. Grid-linked technologies vary widely in form and function, but generally share common potentials: to reduce energy consumption via efficiency and/or curtailment, to shift use to off-peak times of day, and to enable distributed storage and generation options. Although end users are central players in these systems, they are sometimes not central considerations in technology or program design, and in some cases, their motivations for participating in such systems are not fully appreciated. Behavioral science can be instrumental in engaging end-users and maximizingmore » the impact of smart grid technologies. In this study, we present emerging technologies made possible by a smart grid infrastructure, and for each we highlight ways in which behavioral science can be applied to enhance their impact on energy savings.« less

Geographic Visualization of Power-Grid Dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sukumar, Sreenivas R.

2015-06-18

The visualization enables the simulation analyst to see changes in the frequency through time and space. With this technology, the analyst has a bird's eye view of the frequency at loads and generators as the simulated power system responds to the loss of a generator, spikes in load, and other contingencies. The significance of a contingency to the operation of an electrical power system depends critically on how the resulting tansients evolve in time and space. Consequently, these dynamic events can only be understood when seen in their proper geographic context. this understanding is indispensable to engineers working on themore » next generation of distributed sensing and control systems for the smart grid. By making possible a natural and intuitive presentation of dynamic behavior, our new visualization technology is a situational-awareness tool for power-system engineers.« less

Modeling, control, and simulation of grid connected intelligent hybrid battery/photovoltaic system using new hybrid fuzzy-neural method.

PubMed

Rezvani, Alireza; Khalili, Abbas; Mazareie, Alireza; Gandomkar, Majid

2016-07-01

Nowadays, photovoltaic (PV) generation is growing increasingly fast as a renewable energy source. Nevertheless, the drawback of the PV system is its dependence on weather conditions. Therefore, battery energy storage (BES) can be considered to assist for a stable and reliable output from PV generation system for loads and improve the dynamic performance of the whole generation system in grid connected mode. In this paper, a novel topology of intelligent hybrid generation systems with PV and BES in a DC-coupled structure is presented. Each photovoltaic cell has a specific point named maximum power point on its operational curve (i.e. current-voltage or power-voltage curve) in which it can generate maximum power. Irradiance and temperature changes affect these operational curves. Therefore, the nonlinear characteristic of maximum power point to environment has caused to development of different maximum power point tracking techniques. In order to capture the maximum power point (MPP), a hybrid fuzzy-neural maximum power point tracking (MPPT) method is applied in the PV system. Obtained results represent the effectiveness and superiority of the proposed method, and the average tracking efficiency of the hybrid fuzzy-neural is incremented by approximately two percentage points in comparison to the conventional methods. It has the advantages of robustness, fast response and good performance. A detailed mathematical model and a control approach of a three-phase grid-connected intelligent hybrid system have been proposed using Matlab/Simulink. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Modal Analysis for Grid Operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

MANGO software is to provide a solution for improving small signal stability of power systems through adjusting operator-controllable variables using PMU measurement. System oscillation problems are one of the major threats to the grid stability and reliability in California and the Western Interconnection. These problems result in power fluctuations, lower grid operation efficiency, and may even lead to large-scale grid breakup and outages. This MANGO software aims to solve this problem by automatically generating recommended operation procedures termed Modal Analysis for Grid Operation (MANGO) to improve damping of inter-area oscillation modes. The MANGO procedure includes three steps: recognizing small signalmore » stability problems, implementing operating point adjustment using modal sensitivity, and evaluating the effectiveness of the adjustment. The MANGO software package is designed to help implement the MANGO procedure.« less

Emission & Generation Resource Integrated Database (eGRID)

EPA Pesticide Factsheets

The Emissions & Generation Resource Integrated Database (eGRID) is an integrated source of data on environmental characteristics of electric power generation. Twelve federal databases are represented by eGRID, which provides air emission and resource mix information for thousands of power plants and generating companies. eGRID allows direct comparison of the environmental attributes of electricity from different plants, companies, States, or regions of the power grid.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaunak, S.K.; Soni, B.K.

With research interests shifting away from primarily military or industrial applications to more environmental applications, the area of ocean modelling has become an increasingly popular and exciting area of research. This paper presents a CIPS (Computation Field Simulation) system customized for the solution of oceanographic problems. This system deals primarily with the generation of simple, yet efficient grids for coastal areas. The two primary grid approaches are both structured in methodology. The first approach is a standard approach which is used in such popular grid generation softwares as GE-NIE++, EAGLEVIEW, and TIGER, where the user defines boundaries via points, lines,more » or curves, varies the distribution of points along these boundaries and then creates the interior grid. The second approach is to allow the user to interactively select points on the screen to form the boundary curves and then create the interior grid from these spline curves. The program has been designed with the needs of the ocean modeller in mind so that the modeller can obtain results in a timely yet elegant manner. The modeller performs four basic steps in using the program. First, he selects a region of interest from a popular database. Then, he creates a grid for that region. Next, he sets up boundary and input conditions and runs a circulation model. Finally, the modeller visualizes the output.« less

OVERSMART Reporting Tool for Flow Computations Over Large Grid Systems

NASA Technical Reports Server (NTRS)

Kao, David L.; Chan, William M.

2012-01-01

Structured grid solvers such as NASA's OVERFLOW compressible Navier-Stokes flow solver can generate large data files that contain convergence histories for flow equation residuals, turbulence model equation residuals, component forces and moments, and component relative motion dynamics variables. Most of today's large-scale problems can extend to hundreds of grids, and over 100 million grid points. However, due to the lack of efficient tools, only a small fraction of information contained in these files is analyzed. OVERSMART (OVERFLOW Solution Monitoring And Reporting Tool) provides a comprehensive report of solution convergence of flow computations over large, complex grid systems. It produces a one-page executive summary of the behavior of flow equation residuals, turbulence model equation residuals, and component forces and moments. Under the automatic option, a matrix of commonly viewed plots such as residual histograms, composite residuals, sub-iteration bar graphs, and component forces and moments is automatically generated. Specific plots required by the user can also be prescribed via a command file or a graphical user interface. Output is directed to the user s computer screen and/or to an html file for archival purposes. The current implementation has been targeted for the OVERFLOW flow solver, which is used to obtain a flow solution on structured overset grids. The OVERSMART framework allows easy extension to other flow solvers.

Progress and challenges in the application of artificial intelligence to computational fluid dynamics

NASA Technical Reports Server (NTRS)

Andrews, Alison E.

1987-01-01

An approach to analyzing CFD knowledge-based systems is proposed which is based, in part, on the concept of knowledge-level analysis. Consideration is given to the expert cooling fan design system, the PAN AIR knowledge system, grid adaptation, and expert zonal grid generation. These AI/CFD systems demonstrate that current AI technology can be successfully applied to well-formulated problems that are solved by means of classification or selection of preenumerated solutions.

U.S. Laws and Regulations for Renewable Energy Grid Interconnections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chernyakhovskiy, Ilya; Tian, Tian; McLaren, Joyce

Rapidly declining costs of wind and solar energy technologies, increasing concerns about the environmental and climate change impacts of fossil fuels, and sustained investment in renewable energy projects all point to a not-so-distant future in which renewable energy plays a pivotal role in the electric power system of the 21st century. In light of public pressures and market factors that hasten the transition towards a low-carbon system, power system planners and regulators are preparing to integrate higher levels of variable renewable generation into the grid. Updating the regulations that govern generator interconnections and operations is crucial to ensure system reliabilitymore » while creating an enabling environment for renewable energy development. This report presents a chronological review of energy laws and regulations concerning grid interconnection procedures in the United States, highlighting the consequences of policies for renewable energy interconnections. Where appropriate, this report places interconnection policies and their impacts on renewable energy within the broader context of power market reform.« less

Direct Replacement of Arbitrary Grid-Overlapping by Non-Structured Grid

NASA Technical Reports Server (NTRS)

Kao, Kai-Hsiung; Liou, Meng-Sing

1994-01-01

A new approach that uses nonstructured mesh to replace the arbitrarily overlapped structured regions of embedded grids is presented. The present methodology uses the Chimera composite overlapping mesh system so that the physical domain of the flowfield is subdivided into regions which can accommodate easily-generated grid for complex configuration. In addition, a Delaunay triangulation technique generates nonstructured triangular mesh which wraps over the interconnecting region of embedded grids. It is designed that the present approach, termed DRAGON grid, has three important advantages: eliminating some difficulties of the Chimera scheme, such as the orphan points and/or bad quality of interpolation stencils; making grid communication in a fully conservative way; and implementation into three dimensions is straightforward. A computer code based on a time accurate, finite volume, high resolution scheme for solving the compressible Navier-Stokes equations has been further developed to include both the Chimera overset grid and the nonstructured mesh schemes. For steady state problems, the local time stepping accelerates convergence based on a Courant - Friedrichs - Leury (CFL) number near the local stability limit. Numerical tests on representative steady and unsteady supersonic inviscid flows with strong shock waves are demonstrated.

The effectiveness of small scale Photovoltaic (PV) systems design and cost analysis simulation on Saudi Arabian Economy

NASA Astrophysics Data System (ADS)

Almansour, Faris Abdullah

The advantages of Renewable Energy Sources (RES) are much more than the disadvantages, RES such as solar, wind energy, biomass, and geothermal, which can be used for generating distributed power but cannot directly replace the existing electric energy grid technologies. The latter are far too well established to abandon, while the new RES technologies are not sufficiently developed to meet the total energy demand. Therefore, it is sensible to gradually infuse RES into existing grids and transform the system over time Saudi Arabia (SA) is a semi-developed nation with a population of over twenty nine million people. It is the largest country in western Asia with an area of 2.225MKm2. SA's largest export is oil, owning 1/5 of the world's supply, and producing twelve million barrels a day. However, SA is far behind in developing a smart grid and RES. A lot of this is to do with lack of participation by both the government and the private business sector. Currently SA spends over $13B a year on generating electricity from oil. SA is the largest consumer of petroleum in the Middle East, due to the high demand for transportation and electricity generation. According to the Saudi electrical company, the total amount of generated power in 2011 was 190.280GW. In addition, SA's electricity consumption is currently growing 8% a year. SA aims to generate 55GW of renewable energy by 2020, in order to free up fossil fuels for export. 41GW of the 55GW will be generated from solar energy. Smart grid technologies are also under consideration in SA; this will allow an efficient and reliable way to control the energy in the future. In addition, the potential for wind and geothermal energy is very high. In this thesis, there is a full exploration of RES components which are critical to manage carbon emission and the limitations of the current grid to the new RES technologies, which face barriers to full-scale deployment. A study in Dhahran, SA has been simulated on a installing a Dual-Tariff PV system using HOMER. The result of the simulation has been discussed, analyzed, and plotted. We also give evidence in the thesis how useful the small PV systems can be as oppose to the larger scale system that must deal with location issues.

Greening the Grid: Pathways to Integrate 175 Gigawatts of Renewable Energy into India’s Electric Grid, Vol. I. National Study. Executive Summary

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palchak, David; Cochran, Jaquelin; Deshmukh, Ranjit

The use of renewable energy (RE) sources, primarily wind and solar generation, is poised to grow significantly within the Indian power system. The Government of India has established an installed capacity target of 175 gigawatts (GW) RE by 2022 that includes 60 GW of wind and 100 GW of solar, up from current capacities of 29 GW wind and 9 GW solar. India’s contribution to global efforts on climate mitigation extends this ambition to 40% non-fossil-based generation capacity by 2030. Global experience demonstrates that power systems can integrate wind and solar at this scale; however, evidence-based planning is important tomore » achieve wind and solar integration at least cost. The purpose of this analysis is to evaluate the operation of India’s power grid with 175 GW of RE in order to identify potential cost and operational concerns and actions needed to efficiently integrate this level of wind and solar generation.« less

Some advanced parametric methods for assessing waveform distortion in a smart grid with renewable generation

NASA Astrophysics Data System (ADS)

Alfieri, Luisa

2015-12-01

Power quality (PQ) disturbances are becoming an important issue in smart grids (SGs) due to the significant economic consequences that they can generate on sensible loads. However, SGs include several distributed energy resources (DERs) that can be interconnected to the grid with static converters, which lead to a reduction of the PQ levels. Among DERs, wind turbines and photovoltaic systems are expected to be used extensively due to the forecasted reduction in investment costs and other economic incentives. These systems can introduce significant time-varying voltage and current waveform distortions that require advanced spectral analysis methods to be used. This paper provides an application of advanced parametric methods for assessing waveform distortions in SGs with dispersed generation. In particular, the Standard International Electrotechnical Committee (IEC) method, some parametric methods (such as Prony and Estimation of Signal Parameters by Rotational Invariance Technique (ESPRIT)), and some hybrid methods are critically compared on the basis of their accuracy and the computational effort required.

On the use of Schwarz-Christoffel conformal mappings to the grid generation for global ocean models

NASA Astrophysics Data System (ADS)

Xu, S.; Wang, B.; Liu, J.

2015-10-01

In this article we propose two grid generation methods for global ocean general circulation models. Contrary to conventional dipolar or tripolar grids, the proposed methods are based on Schwarz-Christoffel conformal mappings that map areas with user-prescribed, irregular boundaries to those with regular boundaries (i.e., disks, slits, etc.). The first method aims at improving existing dipolar grids. Compared with existing grids, the sample grid achieves a better trade-off between the enlargement of the latitudinal-longitudinal portion and the overall smooth grid cell size transition. The second method addresses more modern and advanced grid design requirements arising from high-resolution and multi-scale ocean modeling. The generated grids could potentially achieve the alignment of grid lines to the large-scale coastlines, enhanced spatial resolution in coastal regions, and easier computational load balance. Since the grids are orthogonal curvilinear, they can be easily utilized by the majority of ocean general circulation models that are based on finite difference and require grid orthogonality. The proposed grid generation algorithms can also be applied to the grid generation for regional ocean modeling where complex land-sea distribution is present.

Mixing in 3D Sparse Multi-Scale Grid Generated Turbulence

NASA Astrophysics Data System (ADS)

Usama, Syed; Kopec, Jacek; Tellez, Jackson; Kwiatkowski, Kamil; Redondo, Jose; Malik, Nadeem

2017-04-01

Flat 2D fractal grids are known to alter turbulence characteristics downstream of the grid as compared to the regular grids with the same blockage ratio and the same mass inflow rates [1]. This has excited interest in the turbulence community for possible exploitation for enhanced mixing and related applications. Recently, a new 3D multi-scale grid design has been proposed [2] such that each generation of length scale of turbulence grid elements is held in its own frame, the overall effect is a 3D co-planar arrangement of grid elements. This produces a 'sparse' grid system whereby each generation of grid elements produces a turbulent wake pattern that interacts with the other wake patterns downstream. A critical motivation here is that the effective blockage ratio in the 3D Sparse Grid Turbulence (3DSGT) design is significantly lower than in the flat 2D counterpart - typically the blockage ratio could be reduced from say 20% in 2D down to 4% in the 3DSGT. If this idea can be realized in practice, it could potentially greatly enhance the efficiency of turbulent mixing and transfer processes clearly having many possible applications. Work has begun on the 3DSGT experimentally using Surface Flow Image Velocimetry (SFIV) [3] at the European facility in the Max Planck Institute for Dynamics and Self-Organization located in Gottingen, Germany and also at the Technical University of Catalonia (UPC) in Spain, and numerically using Direct Numerical Simulation (DNS) at King Fahd University of Petroleum & Minerals (KFUPM) in Saudi Arabia and in University of Warsaw in Poland. DNS is the most useful method to compare the experimental results with, and we are studying different types of codes such as Imcompact3d, and OpenFoam. Many variables will eventually be investigated for optimal mixing conditions. For example, the number of scale generations, the spacing between frames, the size ratio of grid elements, inflow conditions, etc. We will report upon the first set of findings from the 3DSGT by the time of the conference. {Acknowledgements}: This work has been supported partly by the EuHIT grant, 'Turbulence Generated by Sparse 3D Multi-Scale Grid (M3SG)', 2017. {References} [1] S. Laizet, J. C. Vassilicos. DNS of Fractal-Generated Turbulence. Flow Turbulence Combust 87:673705, (2011). [2] N. A. Malik. Sparse 3D Multi-Scale Grid Turbulence Generator. USPTO Application no. 14/710,531, Patent Pending, (2015). [3] J. Tellez, M. Gomez, B. Russo, J.M. Redondo. Surface Flow Image Velocimetry (SFIV) for hydraulics applications. 18th Int. Symposium on the Application of Laser Imaging Techniques in Fluid Mechanics, Lisbon, Portugal (2016).

Seasonal energy storage system based on hydrogen for self sufficient living

NASA Astrophysics Data System (ADS)

Bielmann, M.; Vogt, U. F.; Zimmermann, M.; Züttel, A.

SELF is a resource independent living and working environment. By on-board renewable electricity generation and storage, it accounts for all aspects of living, such as space heating and cooking as well as providing a purified rainwater supply and wastewater treatment, excluding food supply. Uninterrupted, on-demand energy and water supply are the key challenges. Off-grid renewable power supply fluctuations on daily and seasonal time scales impose production gaps that have to be served by local storage, a function normally fulfilled by the grid. While daily variations only obligate a small storage capacity, requirements for seasonal storage are substantial. The energy supply for SELF is reviewed based on real meteorological data and demand patterns for Zurich, Switzerland. A battery system with propane for cooking serves as a reference for battery-only and hybrid battery/hydrogen systems. In the latter, hydrogen is used for cooking and electricity generation. The analysis shows that hydrogen is ideal for long term bulk energy storage on a seasonal timescale, while batteries are best suited for short term energy storage. Although the efficiency penalty from hydrogen generation is substantial, in off-grid systems, this parameter is tolerable since the harvesting ratio of photovoltaic energy is limited by storage capacity.

GridWise Standards Mapping Overview

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bosquet, Mia L.

''GridWise'' is a concept of how advanced communications, information and controls technology can transform the nation's energy system--across the spectrum of large scale, central generation to common consumer appliances and equipment--into a collaborative network, rich in the exchange of decision making information and an abundance of market-based opportunities (Widergren and Bosquet 2003) accompanying the electric transmission and distribution system fully into the information and telecommunication age. This report summarizes a broad review of standards efforts which are related to GridWise--those which could ultimately contribute significantly to advancements toward the GridWise vision, or those which represent today's current technological basis uponmore » which this vision must build.« less

Algebraic grid generation using tensor product B-splines. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Saunders, B. V.

1985-01-01

Finite difference methods are more successful if the accompanying grid has lines which are smooth and nearly orthogonal. The development of an algorithm which produces such a grid when given the boundary description. Topological considerations in structuring the grid generation mapping are discussed. The concept of the degree of a mapping and how it can be used to determine what requirements are necessary if a mapping is to produce a suitable grid is examined. The grid generation algorithm uses a mapping composed of bicubic B-splines. Boundary coefficients are chosen so that the splines produce Schoenberg's variation diminishing spline approximation to the boundary. Interior coefficients are initially chosen to give a variation diminishing approximation to the transfinite bilinear interpolant of the function mapping the boundary of the unit square onto the boundary grid. The practicality of optimizing the grid by minimizing a functional involving the Jacobian of the grid generation mapping at each interior grid point and the dot product of vectors tangent to the grid lines is investigated. Grids generated by using the algorithm are presented.

Three-dimensional self-adaptive grid method for complex flows

NASA Technical Reports Server (NTRS)

Djomehri, M. Jahed; Deiwert, George S.

1988-01-01

A self-adaptive grid procedure for efficient computation of three-dimensional complex flow fields is described. The method is based on variational principles to minimize the energy of a spring system analogy which redistributes the grid points. Grid control parameters are determined by specifying maximum and minimum grid spacing. Multidirectional adaptation is achieved by splitting the procedure into a sequence of successive applications of a unidirectional adaptation. One-sided, two-directional constraints for orthogonality and smoothness are used to enhance the efficiency of the method. Feasibility of the scheme is demonstrated by application to a multinozzle, afterbody, plume flow field. Application of the algorithm for initial grid generation is illustrated by constructing a three-dimensional grid about a bump-like geometry.

EAGLEView: A surface and grid generation program and its data management

NASA Technical Reports Server (NTRS)

Remotigue, M. G.; Hart, E. T.; Stokes, M. L.

1992-01-01

An old and proven grid generation code, the EAGLE grid generation package, is given an added dimension of a graphical interface and a real time data base manager. The Numerical Aerodynamic Simulation (NAS) Panel Library is used for the graphical user interface. Through the panels, EAGLEView constructs the EAGLE script command and sends it to EAGLE to be processed. After the object is created, the script is saved in a mini-buffer which can be edited and/or saved and reinterpreted. The graphical objects are set-up in a linked-list and can be selected or queried by pointing and clicking the mouse. The added graphical enhancement to the EAGLE system emphasizes the unique capability to construct field points around complex geometry and visualize the construction every step of the way.

On the Path to SunShot - Emerging Issues and Challenges in Integrating High Levels of Solar into the Electrical Generation and Transmission System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denholm, Paul; Clark, Kara; O'Connell, Matt

Increasing the use of grid-flexibility options (improved grid management, demand response, and energy storage) could enable 25% or higher penetration of PV at low costs (see Denholm et al. 2016). Considering the large-scale integration of solar into electric-power systems complicates the calculation of the value of solar. In fact a comprehensive examination reveals that the value of solar technologies—or any other power-system technology or operating strategy—can only be understood in the context of the generation system as a whole. This is well illustrated by analysis of curtailment at high PV penetrations within the bulk power and transmission systems. As themore » deployment of PV increases, it is possible that during some sunny midday periods due to limited flexibility of conventional generators, system operators would need to reduce (curtail) PV output in order to maintain the crucial balance between electric supply and demand. As a result, PV’s value and cost competitiveness would degrade. For example, for utility-scale PV with a baseline SunShot LCOE of 6¢/kWh, increasing the annual energy demand met by solar energy from 10% to 20% would increase the marginal LCOE of PV from 6¢/kWh to almost 11¢/kWh in a California grid system with limited flexibility. However, this loss of value could be stemmed by increasing system flexibility via enhanced control of variable-generation resources, added energy storage, and the ability to motivate more electricity consumers to shift consumption to lower-demand periods. The combination of these measures would minimize solar curtailment and keep PV cost-competitive at penetrations at least as high as 25%. Efficient deployment of the grid-flexibility options needed to maintain solar’s value will require various innovations, from the development of communication, control, and energy storage technologies to the implementation of new market rules and operating procedures.« less

A Petri Net model for distributed energy system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Konopko, Joanna

2015-12-31

Electrical networks need to evolve to become more intelligent, more flexible and less costly. The smart grid is the next generation power energy, uses two-way flows of electricity and information to create a distributed automated energy delivery network. Building a comprehensive smart grid is a challenge for system protection, optimization and energy efficient. Proper modeling and analysis is needed to build an extensive distributed energy system and intelligent electricity infrastructure. In this paper, the whole model of smart grid have been proposed using Generalized Stochastic Petri Nets (GSPN). The simulation of created model is also explored. The simulation of themore » model has allowed the analysis of how close the behavior of the model is to the usage of the real smart grid.« less

Locating PHEV exchange stations in V2G

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Feng; Bent, Russell; Berscheid, Alan

2010-01-01

Plug-in hybrid electric vehicle (PREV) is an environment friendly modem transportation method and has been rapidly penetrate the transportation system. Renewable energy is another contributor to clean power but the associated intermittence increases the uncertainty in power generation. As a foreseen benefit of a vchicle-to-grid (V2G) system, PREV supporting infrastructures like battery exchange stations can provide battery service to PREV customers as well as being plugged into a power grid as energy sources and stabilizer. The locations of exchange stations are important for these two objectives under constraints from both ,transportation system and power grid. To model this location problemmore » and to understand and analyze the benefit of a V2G system, we develop a two-stage stochastic program to optimally locate the stations prior to the realizations of battery demands, loads, and generation capacity of renewable power sources. Based on this model, we use two data sets to construct the V2G systems and test the benefit and the performance of these systems.« less

A Preliminary Study of Building a Transmission Overlay for Regional US Power Grid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lei, Yin; Li, Yalong; Liu, Yilu

2015-01-01

Many European countries have taken steps toward a Supergrid in order to transmit large amount of intermittent and remote renewable energy over long distance to load centers. In the US, as the expected increase in renewable generation and electricity demand, similar problem arises. A potential solution is to upgrade the transmission system at a higher voltage by constructing a new overlay grid. This paper will first address basic requirements for such an overlay grid. Potential transmission technologies will also be discussed. A multi-terminal VSC HVDC model is developed in DSATools to implement the overlay grid and a test case onmore » a regional NPCC system will be simulated. Another test system of entire US power grid, with three different interconnections tied together using back-to-back HVDC, is also introduced in this paper. Building an overlay system on top of this test case is ongoing, and will be discussed in future work.« less

The Emissions Impacts of Varied Energy Storage Operational Objectives Across Regions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barrett, Emily L.; Thayer, Brandon L.; Studarus, Karen E.

The emissions consequences of smart grid technologies can be significant but are not always intuitive. This is particularly true in the implementation of energy storage (ES) systems that are being increasingly adopted to integrate more intermittent renewable generation, to reduce peak demand, and to participate in energy markets. Both the location of the ES system within the grid and the way it is operated will dictate its resulting impacts. The Grid Project Impact Quantification tool can provide insight into some of the emissions implications of hypothetical ES systems for a variety of operational objectives in diverse locations within the Unitedmore » States.« less

Three-dimensional elliptic grid generation for an F-16

NASA Technical Reports Server (NTRS)

Sorenson, Reese L.

1988-01-01

A case history depicting the effort to generate a computational grid for the simulation of transonic flow about an F-16 aircraft at realistic flight conditions is presented. The flow solver for which this grid is designed is a zonal one, using the Reynolds averaged Navier-Stokes equations near the surface of the aircraft, and the Euler equations in regions removed from the aircraft. A body conforming global grid, suitable for the Euler equation, is first generated using 3-D Poisson equations having inhomogeneous terms modeled after the 2-D GRAPE code. Regions of the global grid are then designated for zonal refinement as appropriate to accurately model the flow physics. Grid spacing suitable for solution of the Navier-Stokes equations is generated in the refinement zones by simple subdivision of the given coarse grid intervals. That grid generation project is described, with particular emphasis on the global coarse grid.

Schwarz-Christoffel Conformal Mapping based Grid Generation for Global Oceanic Circulation Models

NASA Astrophysics Data System (ADS)

Xu, Shiming

2015-04-01

We propose new grid generation algorithms for global ocean general circulation models (OGCMs). Contrary to conventional, analytical forms based dipolar or tripolar grids, the new algorithm are based on Schwarz-Christoffel (SC) conformal mapping with prescribed boundary information. While dealing with the conventional grid design problem of pole relocation, it also addresses more advanced issues of computational efficiency and the new requirements on OGCM grids arisen from the recent trend of high-resolution and multi-scale modeling. The proposed grid generation algorithm could potentially achieve the alignment of grid lines to coastlines, enhanced spatial resolution in coastal regions, and easier computational load balance. Since the generated grids are still orthogonal curvilinear, they can be readily 10 utilized in existing Bryan-Cox-Semtner type ocean models. The proposed methodology can also be applied to the grid generation task for regional ocean modeling when complex land-ocean distribution is present.

Unstructured viscous grid generation by advancing-front method

NASA Technical Reports Server (NTRS)

Pirzadeh, Shahyar

1993-01-01

A new method of generating unstructured triangular/tetrahedral grids with high-aspect-ratio cells is proposed. The method is based on new grid-marching strategy referred to as 'advancing-layers' for construction of highly stretched cells in the boundary layer and the conventional advancing-front technique for generation of regular, equilateral cells in the inviscid-flow region. Unlike the existing semi-structured viscous grid generation techniques, the new procedure relies on a totally unstructured advancing-front grid strategy resulting in a substantially enhanced grid flexibility and efficiency. The method is conceptually simple but powerful, capable of producing high quality viscous grids for complex configurations with ease. A number of two-dimensional, triangular grids are presented to demonstrate the methodology. The basic elements of the method, however, have been primarily designed with three-dimensional problems in mind, making it extendible for tetrahedral, viscous grid generation.

Demonstration of Essential Reliability Services by a 300-MW Solar Photovoltaic Power Plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loutan, Clyde; Klauer, Peter; Chowdhury, Sirajul

The California Independent System Operator (CAISO), First Solar, and the National Renewable Energy Laboratory (NREL) conducted a demonstration project on a large utility-scale photovoltaic (PV) power plant in California to test its ability to provide essential ancillary services to the electric grid. With increasing shares of solar- and wind-generated energy on the electric grid, traditional generation resources equipped with automatic governor control (AGC) and automatic voltage regulation controls -- specifically, fossil thermal -- are being displaced. The deployment of utility-scale, grid-friendly PV power plants that incorporate advanced capabilities to support grid stability and reliability is essential for the large-scale integrationmore » of PV generation into the electric power grid, among other technical requirements. A typical PV power plant consists of multiple power electronic inverters and can contribute to grid stability and reliability through sophisticated 'grid-friendly' controls. In this way, PV power plants can be used to mitigate the impact of variability on the grid, a role typically reserved for conventional generators. In August 2016, testing was completed on First Solar's 300-MW PV power plant, and a large amount of test data was produced and analyzed that demonstrates the ability of PV power plants to use grid-friendly controls to provide essential reliability services. These data showed how the development of advanced power controls can enable PV to become a provider of a wide range of grid services, including spinning reserves, load following, voltage support, ramping, frequency response, variability smoothing, and frequency regulation to power quality. Specifically, the tests conducted included various forms of active power control such as AGC and frequency regulation; droop response; and reactive power, voltage, and power factor controls. This project demonstrated that advanced power electronics and solar generation can be controlled to contribute to system-wide reliability. It was shown that the First Solar plant can provide essential reliability services related to different forms of active and reactive power controls, including plant participation in AGC, primary frequency control, ramp rate control, and voltage regulation. For AGC participation in particular, by comparing the PV plant testing results to the typical performance of individual conventional technologies, we showed that regulation accuracy by the PV plant is 24-30 points better than fast gas turbine technologies. The plant's ability to provide volt-ampere reactive control during periods of extremely low power generation was demonstrated as well. The project team developed a pioneering demonstration concept and test plan to show how various types of active and reactive power controls can leverage PV generation's value from being a simple variable energy resource to a resource that provides a wide range of ancillary services. With this project's approach to a holistic demonstration on an actual, large, utility-scale, operational PV power plant and dissemination of the obtained results, the team sought to close some gaps in perspectives that exist among various stakeholders in California and nationwide by providing real test data.« less

Forecasting of Hourly Photovoltaic Energy in Canarian Electrical System

NASA Astrophysics Data System (ADS)

Henriquez, D.; Castaño, C.; Nebot, R.; Piernavieja, G.; Rodriguez, A.

2010-09-01

The Canarian Archipelago face similar problems as most insular region lacking of endogenous conventional energy resources and not connected to continental electrical grids. A consequence of the "insular fact" is the existence of isolated electrical systems that are very difficult to interconnect due to the considerable sea depths between the islands. Currently, the Canary Islands have six isolated electrical systems, only one utility generating most of the electricity (burning fuel), a recently arrived TSO (REE) and still a low implementation of Renewable Energy Resources (RES). The low level of RES deployment is a consequence of two main facts: the weakness of the stand-alone grids (from 12 MW in El Hierro up to only 1 GW in Gran Canaria) and the lack of space to install RES systems (more than 50% of the land protected due to environmental reasons). To increase the penetration of renewable energy generation, like solar or wind energy, is necessary to develop tools to manage them. The penetration of non manageable sources into weak grids like the Canarian ones causes a big problem to the grid operator. There are currently 104 MW of PV connected to the islands grids (Dec. 2009) and additional 150 MW under licensing. This power presents a serious challenge for the operation and stability of the electrical system. ITC, together with the local TSO (Red Eléctrica de España, REE) started in 2008 and R&D project to develop a PV energy prediction tool for the six Canarian Insular electrical systems. The objective is to supply reliable information for hourly forecast of the generation dispatch programme and to predict daily solar radiation patterns, in order to help program spinning reserves. ITC has approached the task of weather forecasting using different numerical model (MM5 and WRF) in combination with MSG (Meteosat Second Generation) images. From the online data recorded at several monitored PV plants and meteorological stations, PV nominal power and energy produced by every plant in Canary Islands are estimated using a series of theoretical and statistical energy models.

Grid Transmission Expansion Planning Model Based on Grid Vulnerability

NASA Astrophysics Data System (ADS)

Tang, Quan; Wang, Xi; Li, Ting; Zhang, Quanming; Zhang, Hongli; Li, Huaqiang

2018-03-01

Based on grid vulnerability and uniformity theory, proposed global network structure and state vulnerability factor model used to measure different grid models. established a multi-objective power grid planning model which considering the global power network vulnerability, economy and grid security constraint. Using improved chaos crossover and mutation genetic algorithm to optimize the optimal plan. For the problem of multi-objective optimization, dimension is not uniform, the weight is not easy given. Using principal component analysis (PCA) method to comprehensive assessment of the population every generation, make the results more objective and credible assessment. the feasibility and effectiveness of the proposed model are validated by simulation results of Garver-6 bus system and Garver-18 bus.

Zone heated inlet ignited diesel particulate filter regeneration

DOEpatents

Gonze, Eugene V [Pinckney, MI; Ament, Frank [Troy, MI

2012-06-26

An exhaust system that processes exhaust generated by an engine is provided. The system includes: a particulate filter (PF) that is disposed downstream of the engine and that filters particulates from the exhaust; and a grid that includes electrically resistive material that is segmented by non-conductive material into a plurality of zones and wherein the grid is applied to an exterior upstream surface of the PF.

Potential application of artificial concepts to aerodynamic simulation

NASA Technical Reports Server (NTRS)

Kutler, P.; Mehta, U. B.; Andrews, A.

1984-01-01

The concept of artificial intelligence as it applies to computational fluid dynamics simulation is investigated. How expert systems can be adapted to speed the numerical aerodynamic simulation process is also examined. A proposed expert grid generation system is briefly described which, given flow parameters, configuration geometry, and simulation constraints, uses knowledge about the discretization process to determine grid point coordinates, computational surface information, and zonal interface parameters.

A Unified Overset Grid Generation Graphical Interface and New Concepts on Automatic Gridding Around Surface Discontinuities

NASA Technical Reports Server (NTRS)

Chan, William M.; Akien, Edwin (Technical Monitor)

2002-01-01

For many years, generation of overset grids for complex configurations has required the use of a number of different independently developed software utilities. Results created by each step were then visualized using a separate visualization tool before moving on to the next. A new software tool called OVERGRID was developed which allows the user to perform all the grid generation steps and visualization under one environment. OVERGRID provides grid diagnostic functions such as surface tangent and normal checks as well as grid manipulation functions such as extraction, extrapolation, concatenation, redistribution, smoothing, and projection. Moreover, it also contains hyperbolic surface and volume grid generation modules that are specifically suited for overset grid generation. It is the first time that such a unified interface existed for the creation of overset grids for complex geometries. New concepts on automatic overset surface grid generation around surface discontinuities will also be briefly presented. Special control curves on the surface such as intersection curves, sharp edges, open boundaries, are called seam curves. The seam curves are first automatically extracted from a multiple panel network description of the surface. Points where three or more seam curves meet are automatically identified and are called seam corners. Seam corner surface grids are automatically generated using a singular axis topology. Hyperbolic surface grids are then grown from the seam curves that are automatically trimmed away from the seam corners.

Limits and Economic Effects of Distributed PV Generation in North and South Carolina

NASA Astrophysics Data System (ADS)

Holt, Kyra Moore

The variability of renewable sources, such as wind and solar, when integrated into the electrical system must be compensated by traditional generation sources in-order to maintain the constant balance of supply and demand required for grid stability. The goal of this study is to analyze the effects of increasing large levels of solar Photovoltaic (PV) penetration (in terms of a percentage of annual energy production) on a test grid with similar characteristics to the Duke Energy Carolinas (DEC) and Progress Energy Carolinas (PEC) regions of North and South Carolina. PV production is modeled entering the system at the distribution level and regional PV capacity is based on household density. A gridded hourly global horizontal irradiance (GHI) dataset is used to capture the variable nature of PV generation. A unit commitment model (UCM) is then used determine the hourly dispatch of generators based on generator parameters and costs to supply generation to meet demand. Annual modeled results for six different scenarios are evaluated to determine technical, environmental and economic effects of varying levels of distributed PV penetration on the system. This study finds that the main limiting factor for PV integration in the DEC and PEC balancing authority regions is defined by the large generating capacity of base-load nuclear plants within the system. This threshold starts to affect system stability at integration levels of 5.7%. System errors, defined by imbalances caused by over or under generation with respect to demand, are identified in the model however the validity of these errors in real world context needs further examination due to the lack of high frequency irradiance data and modeling limitations. Operational system costs decreased as expected with PV integration although further research is needed to explore the impacts of the capital costs required to achieve the penetration levels found in this study. PV system generation was found to mainly displace coal generation creating a loss of revenue for generator owners. In all scenarios, CO 2 emissions were reduced with PV integration. This reduction could be used to meet impending EPA state-specific CO2 emissions targets.

Cascading failures in ac electricity grids.

PubMed

Rohden, Martin; Jung, Daniel; Tamrakar, Samyak; Kettemann, Stefan

2016-09-01

Sudden failure of a single transmission element in a power grid can induce a domino effect of cascading failures, which can lead to the isolation of a large number of consumers or even to the failure of the entire grid. Here we present results of the simulation of cascading failures in power grids, using an alternating current (AC) model. We first apply this model to a regular square grid topology. For a random placement of consumers and generators on the grid, the probability to find more than a certain number of unsupplied consumers decays as a power law and obeys a scaling law with respect to system size. Varying the transmitted power threshold above which a transmission line fails does not seem to change the power-law exponent q≈1.6. Furthermore, we study the influence of the placement of generators and consumers on the number of affected consumers and demonstrate that large clusters of generators and consumers are especially vulnerable to cascading failures. As a real-world topology, we consider the German high-voltage transmission grid. Applying the dynamic AC model and considering a random placement of consumers, we find that the probability to disconnect more than a certain number of consumers depends strongly on the threshold. For large thresholds the decay is clearly exponential, while for small ones the decay is slow, indicating a power-law decay.

Communication Security for Control Systems in Smart Grid

NASA Astrophysics Data System (ADS)

Robles, Rosslin John; Kim, Tai-Hoon

As an example of Control System, Supervisory Control and Data Acquisition systems can be relatively simple, such as one that monitors environmental conditions of a small office building, or incredibly complex, such as a system that monitors all the activity in a nuclear power plant or the activity of a municipal water system. SCADA systems are basically Process Control Systems, designed to automate systems such as traffic control, power grid management, waste processing etc. Connecting SCADA to the Internet can provide a lot of advantages in terms of control, data viewing and generation. SCADA infrastructures like electricity can also be a part of a Smart Grid. Connecting SCADA to a public network can bring a lot of security issues. To answer the security issues, a SCADA communication security solution is proposed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, Youngho; Hur, Kyeon; Kang, Yong

This study investigates the emerging harmonic stability concerns to be addressed by grid planners in generation interconnection studies, owing to the increased adoption of renewable energy resources connected to the grid via power electronic converters. The wideband and high-frequency electromagnetic transient (EMT) characteristics of these converter-interfaced generators (CIGs) and their interaction with the grid impedance are not accurately captured in the typical dynamic studies conducted by grid planners. This paper thus identifies the desired components to be studied and subsequently develops a practical process for integrating a new CIG into a grid with the existing CIGs. The steps of thismore » process are as follows: the impedance equation of a CIG using its control dynamics and an interface filter to the grid, for example, an LCL filter (inductor-capacitor-inductor type), is developed; an equivalent impedance model including the existing CIGs nearby and the grid observed from the point of common coupling are derived; the system stability for credible operating scenarios is assessed. Detailed EMT simulations validate the accuracy of the impedance models and stability assessment for various connection scenarios. Here, by complementing the conventional EMT simulation studies, the proposed analytical approach enables grid planners to identify critical design parameters for seamlessly integrating a new CIG and ensuring the reliability of the grid.« less

Microgrid and Plug in Electric Vehicle (PEV) with Vehicle to Grid (V2G) Power Services Capability (Briefing Charts)

DTIC Science & Technology

2015-09-01

unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 AGENDA 1. Non-Tactical Vehicle-to-Grid (V2G) Projects • Smart Power...Vehicle Technology Expo and the Battery Show Conference Novi, MI, 15-17 Sep 2015 2 For the Nation • Help stabilize smart grid and can generate revenue...demonstration of a smart , aggregated, ad-hoc capable, vehicle to grid (V2G) and Vehicle to Vehicle (V2V) capable fleet power system to support

Development of an Automatic Grid Generator for Multi-Element High-Lift Wings

NASA Technical Reports Server (NTRS)

Eberhardt, Scott; Wibowo, Pratomo; Tu, Eugene

1996-01-01

The procedure to generate the grid around a complex wing configuration is presented in this report. The automatic grid generation utilizes the Modified Advancing Front Method as a predictor and an elliptic scheme as a corrector. The scheme will advance the surface grid one cell outward and the newly obtained grid is corrected using the Laplace equation. The predictor-corrector step ensures that the grid produced will be smooth for every configuration. The predictor-corrector scheme is extended for a complex wing configuration. A new technique is developed to deal with the grid generation in the wing-gaps and on the flaps. It will create the grids that fill the gap on the wing surface and the gap created by the flaps. The scheme recognizes these configurations automatically so that minimal user input is required. By utilizing an appropriate sequence in advancing the grid points on a wing surface, the automatic grid generation for complex wing configurations is achieved.

TBGG- INTERACTIVE ALGEBRAIC GRID GENERATION

NASA Technical Reports Server (NTRS)

Smith, R. E.

1994-01-01

TBGG, Two-Boundary Grid Generation, applies an interactive algebraic grid generation technique in two dimensions. The program incorporates mathematical equations that relate the computational domain to the physical domain. TBGG has application to a variety of problems using finite difference techniques, such as computational fluid dynamics. Examples include the creation of a C-type grid about an airfoil and a nozzle configuration in which no left or right boundaries are specified. The underlying two-boundary technique of grid generation is based on Hermite cubic interpolation between two fixed, nonintersecting boundaries. The boundaries are defined by two ordered sets of points, referred to as the top and bottom. Left and right side boundaries may also be specified, and call upon linear blending functions to conform interior interpolation to the side boundaries. Spacing between physical grid coordinates is determined as a function of boundary data and uniformly spaced computational coordinates. Control functions relating computational coordinates to parametric intermediate variables that affect the distance between grid points are embedded in the interpolation formulas. A versatile control function technique with smooth cubic spline functions is also presented. The TBGG program is written in FORTRAN 77. It works best in an interactive graphics environment where computational displays and user responses are quickly exchanged. The program has been implemented on a CDC Cyber 170 series computer using NOS 2.4 operating system, with a central memory requirement of 151,700 (octal) 60 bit words. TBGG requires a Tektronix 4015 terminal and the DI-3000 Graphics Library of Precision Visuals, Inc. TBGG was developed in 1986.

The 3D Euler solutions using automated Cartesian grid generation

NASA Technical Reports Server (NTRS)

Melton, John E.; Enomoto, Francis Y.; Berger, Marsha J.

1993-01-01

Viewgraphs on 3-dimensional Euler solutions using automated Cartesian grid generation are presented. Topics covered include: computational fluid dynamics (CFD) and the design cycle; Cartesian grid strategy; structured body fit; grid generation; prolate spheroid; and ONERA M6 wing.

Examples of grid generation with implicitly specified surfaces using GridPro (TM)/az3000. 1: Filleted multi-tube configurations

NASA Technical Reports Server (NTRS)

Cheng, Zheming; Eiseman, Peter R.

1995-01-01

With examples, we illustrate how implicitly specified surfaces can be used for grid generation with GridPro/az3000. The particular examples address two questions: (1) How do you model intersecting tubes with fillets? and (2) How do you generate grids inside the intersected tubes? The implication is much more general. With the results in a forthcoming paper which develops an easy-to-follow procedure for implicit surface modeling, we provide a powerful means for rapid prototyping in grid generation.

Development of stable Grid service at the next generation system of KEKCC

NASA Astrophysics Data System (ADS)

Nakamura, T.; Iwai, G.; Matsunaga, H.; Murakami, K.; Sasaki, T.; Suzuki, S.; Takase, W.

2017-10-01

A lot of experiments in the field of accelerator based science are actively running at High Energy Accelerator Research Organization (KEK) by using SuperKEKB and J-PARC accelerator in Japan. In these days at KEK, the computing demand from the various experiments for the data processing, analysis, and MC simulation is monotonically increasing. It is not only for the case with high-energy experiments, the computing requirement from the hadron and neutrino experiments and some projects of astro-particle physics is also rapidly increasing due to the very high precision measurement. Under this situation, several projects, Belle II, T2K, ILC and KAGRA experiments supported by KEK are going to utilize Grid computing infrastructure as the main computing resource. The Grid system and services in KEK, which is already in production, are upgraded for the further stable operation at the same time of whole scale hardware replacement of KEK Central Computer System (KEKCC). The next generation system of KEKCC starts the operation from the beginning of September 2016. The basic Grid services e.g. BDII, VOMS, LFC, CREAM computing element and StoRM storage element are made by the more robust hardware configuration. Since the raw data transfer is one of the most important tasks for the KEKCC, two redundant GridFTP servers are adapted to the StoRM service instances with 40 Gbps network bandwidth on the LHCONE routing. These are dedicated to the Belle II raw data transfer to the other sites apart from the servers for the data transfer usage of the other VOs. Additionally, we prepare the redundant configuration for the database oriented services like LFC and AMGA by using LifeKeeper. The LFC servers are made by two read/write servers and two read-only servers for the Belle II experiment, and all of them have an individual database for the purpose of load balancing. The FTS3 service is newly deployed as a service for the Belle II data distribution. The service of CVMFS stratum-0 is started for the Belle II software repository, and stratum-1 service is prepared for the other VOs. In this way, there are a lot of upgrade for the real production service of Grid infrastructure at KEK Computing Research Center. In this paper, we would like to introduce the detailed configuration of the hardware for Grid instance, and several mechanisms to construct the robust Grid system in the next generation system of KEKCC.

A grid spacing control technique for algebraic grid generation methods

NASA Technical Reports Server (NTRS)

Smith, R. E.; Kudlinski, R. A.; Everton, E. L.

1982-01-01

A technique which controls the spacing of grid points in algebraically defined coordinate transformations is described. The technique is based on the generation of control functions which map a uniformly distributed computational grid onto parametric variables defining the physical grid. The control functions are smoothed cubic splines. Sets of control points are input for each coordinate directions to outline the control functions. Smoothed cubic spline functions are then generated to approximate the input data. The technique works best in an interactive graphics environment where control inputs and grid displays are nearly instantaneous. The technique is illustrated with the two-boundary grid generation algorithm.

Emissions & Generation Resource Integrated Database (eGRID), eGRID2012

EPA Pesticide Factsheets

The Emissions & Generation Resource Integrated Database (eGRID) is a comprehensive source of data on the environmental characteristics of almost all electric power generated in the United States. These environmental characteristics include air emissions for nitrogen oxides, sulfur dioxide, carbon dioxide, methane, and nitrous oxide; emissions rates; net generation; resource mix; and many other attributes. eGRID2012 Version 1.0 is the eighth edition of eGRID, which contains the complete release of year 2009 data, as well as year 2007, 2005, and 2004 data. For year 2009 data, all the data are contained in a single Microsoft Excel workbook, which contains boiler, generator, plant, state, power control area, eGRID subregion, NERC region, U.S. total and grid gross loss factor tabs. Full documentation, summary data, eGRID subregion and NERC region representational maps, and GHG emission factors are also released in this edition. The fourth edition of eGRID, eGRID2002 Version 2.01, containing year 1996 through 2000 data is located on the eGRID Archive page (http://www.epa.gov/cleanenergy/energy-resources/egrid/archive.html). The current edition of eGRID and the archived edition of eGRID contain the following years of data: 1996 - 2000, 2004, 2005, and 2007. eGRID has no other years of data.

Petroleum system modeling of the western Canada sedimentary basin - isopach grid files

USGS Publications Warehouse

Higley, Debra K.; Henry, Mitchell E.; Roberts, Laura N.R.

2005-01-01

This publication contains zmap-format grid files of isopach intervals that represent strata associated with Devonian to Holocene petroleum systems of the Western Canada Sedimentary Basin (WCSB) of Alberta, British Columbia, and Saskatchewan, Canada. Also included is one grid file that represents elevations relative to sea level of the top of the Lower Cretaceous Mannville Group. Vertical and lateral scales are in meters. The age range represented by the stratigraphic intervals comprising the grid files is 373 million years ago (Ma) to present day. File names, age ranges, formation intervals, and primary petroleum system elements are listed in table 1. Metadata associated with this publication includes information on the study area and the zmap-format files. The digital files listed in table 1 were compiled as part of the Petroleum Processes Research Project being conducted by the Central Energy Resources Team of the U.S. Geological Survey, which focuses on modeling petroleum generation, 3 migration, and accumulation through time for petroleum systems of the WCSB. Primary purposes of the WCSB study are to Construct the 1-D/2-D/3-D petroleum system models of the WCSB. Actual boundaries of the study area are documented within the metadata; excluded are northern Alberta and eastern Saskatchewan, but fringing areas of the United States are included.Publish results of the research and the grid files generated for use in the 3-D model of the WCSB.Evaluate the use of petroleum system modeling in assessing undiscovered oil and gas resources for geologic provinces across the World.

A comparison of Stirling engines for use with a 25 kW dish-electric conversion system

NASA Technical Reports Server (NTRS)

Shaltens, Richard K.

1987-01-01

Two designs for an advanced Stirling conversion system (ASCS) are described. The objective of the ASCS is to generate about 25 kW of electric power to an electric utility grid at an engine/alternator target cost of $300.00/kW at the manufacturing rate of 10,000 unit/yr. Both designs contain a free-piston Stirling engine (FPSE), a heat transport system, solar receiver, a means to generate electric power, the necessary auxiliaries, and a control system. The major differences between the two concepts are: one uses a 25 kWe single-piston FPSE which incorporates a linear alternator to directly convert the energy to electricity on the utility grid; and in the second design, electrical power is generated indirectly using a hydraulic output to a ground based hydraulic motor coupled to a rotating alternator. Diagrams of the two designs are presented.

Using Conventional Hydropower to Help Alleviate Variable Resource Grid Integration Challenges in the Western U.S

NASA Astrophysics Data System (ADS)

Veselka, T. D.; Poch, L.

2011-12-01

Integrating high penetration levels of wind and solar energy resources into the power grid is a formidable challenge in virtually all interconnected systems due to the fact that supply and demand must remain in balance at all times. Since large scale electricity storage is currently not economically viable, generation must exactly match electricity demand plus energy losses in the system as time unfolds. Therefore, as generation from variable resources such as wind and solar fluctuate, production from generating resources that are easier to control and dispatch need to compensate for these fluctuations while at the same time respond to both instantaneous change in load and follow daily load profiles. The grid in the Western U.S. is not exempt to grid integration challenges associated with variable resources. However, one advantage that the power system in the Western U.S. has over many other regional power systems is that its footprint contains an abundance of hydropower resources. Hydropower plants, especially those that have reservoir water storage, can physically change electricity production levels very quickly both via a dispatcher and through automatic generation control. Since hydropower response time is typically much faster than other dispatchable resources such as steam or gas turbines, it is well suited to alleviate variable resource grid integration issues. However, despite an abundance of hydropower resources and the current low penetration of variable resources in the Western U.S., problems have already surfaced. This spring in the Pacific Northwest, wetter than normal hydropower conditions in combination with transmission constraints resulted in controversial wind resource shedding. This action was taken since water spilling would have increased dissolved oxygen levels downstream of dams thereby significantly degrading fish habitats. The extent to which hydropower resources will be able to contribute toward a stable and reliable Western grid is currently being studied. Typically these studies consider the inherent flexibility of hydropower technologies, but tend to fall short on details regarding grid operations, institutional arrangements, and hydropower environmental regulations. This presentation will focus on an analysis that Argonne National Laboratory is conducting in collaboration with the Western Area Power Administration (Western). The analysis evaluates the extent to which Western's hydropower resources may help with grid integration challenges via a proposed Energy Imbalance Market. This market encompasses most of the Western Electricity Coordinating Council footprint. It changes grid operations such that the real-time dispatch would be, in part, based on a 5-minute electricity market. The analysis includes many factors such as site-specific environmental considerations at each of its hydropower facilities, long-term firm purchase agreements, and hydropower operating objectives and goals. Results of the analysis indicate that site-specific details significantly affect the ability of hydropower plant to respond to grid needs in a future which will have a high penetration of variable resources.

A Review of Distributed Control Techniques for Power Quality Improvement in Micro-grids

NASA Astrophysics Data System (ADS)

Zeeshan, Hafiz Muhammad Ali; Nisar, Fatima; Hassan, Ahmad

2017-05-01

Micro-grid is typically visualized as a small scale local power supply network dependent on distributed energy resources (DERs) that can operate simultaneously with grid as well as in standalone manner. The distributed generator of a micro-grid system is usually a converter-inverter type topology acting as a non-linear load, and injecting harmonics into the distribution feeder. Hence, the negative effects on power quality by the usage of distributed generation sources and components are clearly witnessed. In this paper, a review of distributed control approaches for power quality improvement is presented which encompasses harmonic compensation, loss mitigation and optimum power sharing in multi-source-load distributed power network. The decentralized subsystems for harmonic compensation and active-reactive power sharing accuracy have been analysed in detail. Results have been validated to be consistent with IEEE standards.

An Approach for Dynamic Grids

NASA Technical Reports Server (NTRS)

Slater, John W.; Liou, Meng-Sing; Hindman, Richard G.

1994-01-01

An approach is presented for the generation of two-dimensional, structured, dynamic grids. The grid motion may be due to the motion of the boundaries of the computational domain or to the adaptation of the grid to the transient, physical solution. A time-dependent grid is computed through the time integration of the grid speeds which are computed from a system of grid speed equations. The grid speed equations are derived from the time-differentiation of the grid equations so as to ensure that the dynamic grid maintains the desired qualities of the static grid. The grid equations are the Euler-Lagrange equations derived from a variational statement for the grid. The dynamic grid method is demonstrated for a model problem involving boundary motion, an inviscid flow in a converging-diverging nozzle during startup, and a viscous flow over a flat plate with an impinging shock wave. It is shown that the approach is more accurate for transient flows than an approach in which the grid speeds are computed using a finite difference with respect to time of the grid. However, the approach requires significantly more computational effort.

Graph Partitioning for Parallel Applications in Heterogeneous Grid Environments

NASA Technical Reports Server (NTRS)

Bisws, Rupak; Kumar, Shailendra; Das, Sajal K.; Biegel, Bryan (Technical Monitor)

2002-01-01

The problem of partitioning irregular graphs and meshes for parallel computations on homogeneous systems has been extensively studied. However, these partitioning schemes fail when the target system architecture exhibits heterogeneity in resource characteristics. With the emergence of technologies such as the Grid, it is imperative to study the partitioning problem taking into consideration the differing capabilities of such distributed heterogeneous systems. In our model, the heterogeneous system consists of processors with varying processing power and an underlying non-uniform communication network. We present in this paper a novel multilevel partitioning scheme for irregular graphs and meshes, that takes into account issues pertinent to Grid computing environments. Our partitioning algorithm, called MiniMax, generates and maps partitions onto a heterogeneous system with the objective of minimizing the maximum execution time of the parallel distributed application. For experimental performance study, we have considered both a realistic mesh problem from NASA as well as synthetic workloads. Simulation results demonstrate that MiniMax generates high quality partitions for various classes of applications targeted for parallel execution in a distributed heterogeneous environment.

Grid Generation for Multidisciplinary Design and Optimization of an Aerospace Vehicle: Issues and Challenges

NASA Technical Reports Server (NTRS)

Samareh, Jamshid A.

2000-01-01

The purpose of this paper is to discuss grid generation issues and to challenge the grid generation community to develop tools suitable for automated multidisciplinary analysis and design optimization of aerospace vehicles. Special attention is given to the grid generation issues of computational fluid dynamics and computational structural mechanics disciplines.

Distribution System Reliability Analysis for Smart Grid Applications

NASA Astrophysics Data System (ADS)

Aljohani, Tawfiq Masad

Reliability of power systems is a key aspect in modern power system planning, design, and operation. The ascendance of the smart grid concept has provided high hopes of developing an intelligent network that is capable of being a self-healing grid, offering the ability to overcome the interruption problems that face the utility and cost it tens of millions in repair and loss. To address its reliability concerns, the power utilities and interested parties have spent extensive amount of time and effort to analyze and study the reliability of the generation and transmission sectors of the power grid. Only recently has attention shifted to be focused on improving the reliability of the distribution network, the connection joint between the power providers and the consumers where most of the electricity problems occur. In this work, we will examine the effect of the smart grid applications in improving the reliability of the power distribution networks. The test system used in conducting this thesis is the IEEE 34 node test feeder, released in 2003 by the Distribution System Analysis Subcommittee of the IEEE Power Engineering Society. The objective is to analyze the feeder for the optimal placement of the automatic switching devices and quantify their proper installation based on the performance of the distribution system. The measures will be the changes in the reliability system indices including SAIDI, SAIFI, and EUE. The goal is to design and simulate the effect of the installation of the Distributed Generators (DGs) on the utility's distribution system and measure the potential improvement of its reliability. The software used in this work is DISREL, which is intelligent power distribution software that is developed by General Reliability Co.

Electric motorcycle charging station powered by solar energy

NASA Astrophysics Data System (ADS)

Siriwattanapong, Akarawat; Chantharasenawong, Chawin

2018-01-01

This research proposes a design and verification of an off-grid photovoltaic system (PVS) for electric motorcycle charging station to be located in King’s Mongkut’s University of Technology Thonburi, Bangkok, Thailand. The system is designed to work independently (off-grid) and it must be able to fully charge the batteries of a typical passenger electric motorcycle every evening. A 1,000W Toyotron electric motorcycle is chosen for this study. It carries five units of 12.8V 20Ah batteries in series; hence its maximum energy requirement per day is 1,200Wh. An assessment of solar irradiation data and the Generation Factor in Bangkok, Thailand suggests that the charging system consists of one 500W PV panel, an MPPT charge controller, 48V 150Ah battery, a 1,000W DC to AC inverter and other safety devices such as fuses and breakers. An experiment is conducted to verify the viability of the off-grid PVS charging station by collecting the total daily energy generation data in the raining season and winter. The data suggests that the designed off-grid solar power charging station for electric motorcycle is able to supply sufficient energy for daily charging requirements.

Best Practices In Overset Grid Generation

NASA Technical Reports Server (NTRS)

Chan, William M.; Gomez, Reynaldo J., III; Rogers, Stuart E.; Buning, Pieter G.; Kwak, Dochan (Technical Monitor)

2002-01-01

Grid generation for overset grids on complex geometry can be divided into four main steps: geometry processing, surface grid generation, volume grid generation and domain connectivity. For each of these steps, the procedures currently practiced by experienced users are described. Typical problems encountered are also highlighted and discussed. Most of the guidelines are derived from experience on a variety of problems including space launch and return vehicles, subsonic transports with propulsion and high lift devices, supersonic vehicles, rotorcraft vehicles, and turbomachinery.

Compensation for Harmonic Currents and Reactive Power in Wind Power Generation System using PWM Inverter

NASA Astrophysics Data System (ADS)

Shinohara, Katsuji; Shinhatsubo, Kurato; Iimori, Kenichi; Yamamoto, Kichiro; Saruban, Takamichi; Yamaemori, Takahiro

In recent year, consciousness of environmental problems is enhancing, and the price of the electric power purchased by an electric power company is established expensive for the power plant utilizing the natural energy. So, the introduction of the wind power generation is promoted in Japan. Generally, squirrel-cage induction machines are widely used as a generator in wind power generation system because of its small size, lightweight and low-cost. However, the induction machines do not have a source of excitation. Thus, it causes the inrush currents and the instantaneous voltage drop when the generator is directly connected to a power grid. To reduce the inrush currents, an AC power regulator is used. Wind power generations are frequently connected to and disconnected from the power grid. However, when the inrush currents are reduced, harmonic currents are caused by phase control of the AC power regulator. And the phase control of AC power regulator cannot control the power factor. Therefore, we propose the use of the AC power regulator to compensate for the harmonic currents and reactive power in the wind power generation system, and demonstrate the validity of its system by simulated and experimental results.

Numerical grid generation in computational field simulations. Volume 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soni, B.K.; Thompson, J.F.; Haeuser, J.

1996-12-31

To enhance the CFS technology to its next level of applicability (i.e., to create acceptance of CFS in an integrated product and process development involving multidisciplinary optimization) the basic requirements are: rapid turn-around time, reliable and accurate simulation, affordability and appropriate linkage to other engineering disciplines. In response to this demand, there has been a considerable growth in the grid generation related research activities involving automization, parallel processing, linkage with the CAD-CAM systems, CFS with dynamic motion and moving boundaries, strategies and algorithms associated with multi-block structured, unstructured, hybrid, hexahedral, and Cartesian grids, along with its applicability to various disciplinesmore » including biomedical, semiconductor, geophysical, ocean modeling, and multidisciplinary optimization.« less

About the Need of Combining Power Market and Power Grid Model Results for Future Energy System Scenarios

NASA Astrophysics Data System (ADS)

Mende, Denis; Böttger, Diana; Löwer, Lothar; Becker, Holger; Akbulut, Alev; Stock, Sebastian

2018-02-01

The European power grid infrastructure faces various challenges due to the expansion of renewable energy sources (RES). To conduct investigations on interactions between power generation and the power grid, models for the power market as well as for the power grid are necessary. This paper describes the basic functionalities and working principles of both types of models as well as steps to couple power market results and the power grid model. The combination of these models is beneficial in terms of gaining realistic power flow scenarios in the grid model and of being able to pass back results of the power flow and restrictions to the market model. Focus is laid on the power grid model and possible application examples like algorithms in grid analysis, operation and dynamic equipment modelling.

The Overgrid Interface for Computational Simulations on Overset Grids

NASA Technical Reports Server (NTRS)

Chan, William M.; Kwak, Dochan (Technical Monitor)

2002-01-01

Computational simulations using overset grids typically involve multiple steps and a variety of software modules. A graphical interface called OVERGRID has been specially designed for such purposes. Data required and created by the different steps include geometry, grids, domain connectivity information and flow solver input parameters. The interface provides a unified environment for the visualization, processing, generation and diagnosis of such data. General modules are available for the manipulation of structured grids and unstructured surface triangulations. Modules more specific for the overset approach include surface curve generators, hyperbolic and algebraic surface grid generators, a hyperbolic volume grid generator, Cartesian box grid generators, and domain connectivity: pre-processing tools. An interface provides automatic selection and viewing of flow solver boundary conditions, and various other flow solver inputs. For problems involving multiple components in relative motion, a module is available to build the component/grid relationships and to prescribe and animate the dynamics of the different components.

Development and Evaluation of Control System for Microgrid Supplying Heat and Electricity

NASA Astrophysics Data System (ADS)

Kojima, Yasuhiro; Koshio, Masanobu; Nakamura, Shizuka

Photovoltaic (PV) and Wind Turbine (WT) generation systems are expected to offer solutions to reduce green house gases and become more widely used in the future. However, the chief technical drawback of using these kinds of weather-dependent generators is the difficulty of forecasting their output, which can have negative impacts on commercial grids if a large number of them are introduced. Thus, this problem may hinder the wider application of PV and WT generation systems. The Regional Power Grid with Renewable Energy Resources Project was launched to seek a solution to this problem. The scope of the project is to develop, operate, and evaluate a Dispersed Renewable Energy Supply System with the ability to adapt the total energy output in response to changes in weather and demand. Such a system would reduce the impact that PV and WT generation systems have on commercial grids and allow the interconnection of more Dispersed Energy Resources (DER). In other words, the main objective of this project is to demonstrate an integrated energy management system, or a type of microgrid [1], as a new way of introducing DERs. The system has been in operation since October 2005 and will continue operation until March 2008. Through the project period, the data on power quality, system efficiency, operation cost, and environmental burden will be gathered and a cost-benefit analysis of the system will be undertaken. In this paper, firstly we introduce the concept of microgrid for reducing negative impact of natural energy, and secondly illustrate the structure of electric and thermal supply control system for Microgrid, especially for the Hachinohe demonstration project. The control system consists of four stages; weekly operation planning, economic dispatching control, tie-line control and local frequency control. And finally demonstration results and evaluation results are shown.

A single-cell spiking model for the origin of grid-cell patterns

PubMed Central

Kempter, Richard

2017-01-01

Spatial cognition in mammals is thought to rely on the activity of grid cells in the entorhinal cortex, yet the fundamental principles underlying the origin of grid-cell firing are still debated. Grid-like patterns could emerge via Hebbian learning and neuronal adaptation, but current computational models remained too abstract to allow direct confrontation with experimental data. Here, we propose a single-cell spiking model that generates grid firing fields via spike-rate adaptation and spike-timing dependent plasticity. Through rigorous mathematical analysis applicable in the linear limit, we quantitatively predict the requirements for grid-pattern formation, and we establish a direct link to classical pattern-forming systems of the Turing type. Our study lays the groundwork for biophysically-realistic models of grid-cell activity. PMID:28968386

Application of a lower-upper implicit scheme and an interactive grid generation for turbomachinery flow field simulations

NASA Technical Reports Server (NTRS)

Choo, Yung K.; Soh, Woo-Yung; Yoon, Seokkwan

1989-01-01

A finite-volume lower-upper (LU) implicit scheme is used to simulate an inviscid flow in a tubine cascade. This approximate factorization scheme requires only the inversion of sparse lower and upper triangular matrices, which can be done efficiently without extensive storage. As an implicit scheme it allows a large time step to reach the steady state. An interactive grid generation program (TURBO), which is being developed, is used to generate grids. This program uses the control point form of algebraic grid generation which uses a sparse collection of control points from which the shape and position of coordinate curves can be adjusted. A distinct advantage of TURBO compared with other grid generation programs is that it allows the easy change of local mesh structure without affecting the grid outside the domain of independence. Sample grids are generated by TURBO for a compressor rotor blade and a turbine cascade. The turbine cascade flow is simulated by using the LU implicit scheme on the grid generated by TURBO.

Architecture, Voltage, and Components for a Turboelectric Distributed Propulsion Electric Grid (AVC-TeDP)

NASA Technical Reports Server (NTRS)

Gemin, Paul; Kupiszewski, Tom; Radun, Arthur; Pan, Yan; Lai, Rixin; Zhang, Di; Wang, Ruxi; Wu, Xinhui; Jiang, Yan; Galioto, Steve;

Greening the Grid: Pathways to Integrate 175 Gigawatts of Renewable Energy into India's Electric Grid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cochran, Jaquelin

This fact sheet overviews the Greening the Grid India grid integration study. The use of renewable energy (RE) sources, primarily wind and solar generation, is poised to grow significantly within the Indian power system. The Government of India has established a target of 175 gigawatts (GW) of installed RE capacity by 2022, including 60 GW of wind and 100 GW of solar, up from 29 GW wind and 9 GW solar at the beginning of 2017. Thanks to advanced weather and power system modeling made for this project, the study team is able to explore operational impacts of meeting India'smore » RE targets and identify actions that may be favorable for integration.« less

A decision support system using combined-classifier for high-speed data stream in smart grid

NASA Astrophysics Data System (ADS)

Yang, Hang; Li, Peng; He, Zhian; Guo, Xiaobin; Fong, Simon; Chen, Huajun

2016-11-01

Large volume of high-speed streaming data is generated by big power grids continuously. In order to detect and avoid power grid failure, decision support systems (DSSs) are commonly adopted in power grid enterprises. Among all the decision-making algorithms, incremental decision tree is the most widely used one. In this paper, we propose a combined classifier that is a composite of a cache-based classifier (CBC) and a main tree classifier (MTC). We integrate this classifier into a stream processing engine on top of the DSS such that high-speed steaming data can be transformed into operational intelligence efficiently. Experimental results show that our proposed classifier can return more accurate answers than other existing ones.

Differential Evolution Based IDWNN Controller for Fault Ride-Through of Grid-Connected Doubly Fed Induction Wind Generators

PubMed Central

Manonmani, N.; Subbiah, V.; Sivakumar, L.

2015-01-01

The key objective of wind turbine development is to ensure that output power is continuously increased. It is authenticated that wind turbines (WTs) supply the necessary reactive power to the grid at the time of fault and after fault to aid the flowing grid voltage. At this juncture, this paper introduces a novel heuristic based controller module employing differential evolution and neural network architecture to improve the low-voltage ride-through rate of grid-connected wind turbines, which are connected along with doubly fed induction generators (DFIGs). The traditional crowbar-based systems were basically applied to secure the rotor-side converter during the occurrence of grid faults. This traditional controller is found not to satisfy the desired requirement, since DFIG during the connection of crowbar acts like a squirrel cage module and absorbs the reactive power from the grid. This limitation is taken care of in this paper by introducing heuristic controllers that remove the usage of crowbar and ensure that wind turbines supply necessary reactive power to the grid during faults. The controller is designed in this paper to enhance the DFIG converter during the grid fault and this controller takes care of the ride-through fault without employing any other hardware modules. The paper introduces a double wavelet neural network controller which is appropriately tuned employing differential evolution. To validate the proposed controller module, a case study of wind farm with 1.5 MW wind turbines connected to a 25 kV distribution system exporting power to a 120 kV grid through a 30 km 25 kV feeder is carried out by simulation. PMID:26516636

Differential Evolution Based IDWNN Controller for Fault Ride-Through of Grid-Connected Doubly Fed Induction Wind Generators.

PubMed

Manonmani, N; Subbiah, V; Sivakumar, L

2015-01-01

The key objective of wind turbine development is to ensure that output power is continuously increased. It is authenticated that wind turbines (WTs) supply the necessary reactive power to the grid at the time of fault and after fault to aid the flowing grid voltage. At this juncture, this paper introduces a novel heuristic based controller module employing differential evolution and neural network architecture to improve the low-voltage ride-through rate of grid-connected wind turbines, which are connected along with doubly fed induction generators (DFIGs). The traditional crowbar-based systems were basically applied to secure the rotor-side converter during the occurrence of grid faults. This traditional controller is found not to satisfy the desired requirement, since DFIG during the connection of crowbar acts like a squirrel cage module and absorbs the reactive power from the grid. This limitation is taken care of in this paper by introducing heuristic controllers that remove the usage of crowbar and ensure that wind turbines supply necessary reactive power to the grid during faults. The controller is designed in this paper to enhance the DFIG converter during the grid fault and this controller takes care of the ride-through fault without employing any other hardware modules. The paper introduces a double wavelet neural network controller which is appropriately tuned employing differential evolution. To validate the proposed controller module, a case study of wind farm with 1.5 MW wind turbines connected to a 25 kV distribution system exporting power to a 120 kV grid through a 30 km 25 kV feeder is carried out by simulation.

Domain decomposition by the advancing-partition method for parallel unstructured grid generation

NASA Technical Reports Server (NTRS)

Banihashemi, legal representative, Soheila (Inventor); Pirzadeh, Shahyar Z. (Inventor)

2012-01-01

In a method for domain decomposition for generating unstructured grids, a surface mesh is generated for a spatial domain. A location of a partition plane dividing the domain into two sections is determined. Triangular faces on the surface mesh that intersect the partition plane are identified. A partition grid of tetrahedral cells, dividing the domain into two sub-domains, is generated using a marching process in which a front comprises only faces of new cells which intersect the partition plane. The partition grid is generated until no active faces remain on the front. Triangular faces on each side of the partition plane are collected into two separate subsets. Each subset of triangular faces is renumbered locally and a local/global mapping is created for each sub-domain. A volume grid is generated for each sub-domain. The partition grid and volume grids are then merged using the local-global mapping.

On the use of Schwarz-Christoffel conformal mappings to the grid generation for global ocean models

NASA Astrophysics Data System (ADS)

Xu, S.; Wang, B.; Liu, J.

2015-02-01

In this article we propose two conformal mapping based grid generation algorithms for global ocean general circulation models (OGCMs). Contrary to conventional, analytical forms based dipolar or tripolar grids, the new algorithms are based on Schwarz-Christoffel (SC) conformal mapping with prescribed boundary information. While dealing with the basic grid design problem of pole relocation, these new algorithms also address more advanced issues such as smoothed scaling factor, or the new requirements on OGCM grids arisen from the recent trend of high-resolution and multi-scale modeling. The proposed grid generation algorithm could potentially achieve the alignment of grid lines to coastlines, enhanced spatial resolution in coastal regions, and easier computational load balance. Since the generated grids are still orthogonal curvilinear, they can be readily utilized in existing Bryan-Cox-Semtner type ocean models. The proposed methodology can also be applied to the grid generation task for regional ocean modeling where complex land-ocean distribution is present.

Inviscid and viscous flow modelling of complex aircraft configurations using the CFD simulation system sauna

NASA Astrophysics Data System (ADS)

Peace, Andrew J.; May, Nicholas E.; Pocock, Mark F.; Shaw, Jonathon A.

1994-04-01

This paper is concerned with the flow modelling capabilities of an advanced CFD simulation system known by the acronym SAUNA. This system is aimed primarily at complex aircraft configurations and possesses a unique grid generation strategy in its use of block-structured, unstructured or hybrid grids, depending on the geometric complexity of the addressed configuration. The main focus of the paper is in demonstrating the recently developed multi-grid, block-structured grid, viscous flow capability of SAUNA, through its evaluation on a number of configurations. Inviscid predictions are also presented, both as a means of interpreting the viscous results and with a view to showing more completely the capabilities of SAUNA. It is shown that accuracy and flexibility are combined in an efficient manner, thus demonstrating the value of SAUNA in aerodynamic design.

Modeling and Economic Analysis of Power Grid Operations in a Water Constrained System

NASA Astrophysics Data System (ADS)

Zhou, Z.; Xia, Y.; Veselka, T.; Yan, E.; Betrie, G.; Qiu, F.

2016-12-01

The power sector is the largest water user in the United States. Depending on the cooling technology employed at a facility, steam-electric power stations withdrawal and consume large amounts of water for each megawatt hour of electricity generated. The amounts are dependent on many factors, including ambient air and water temperatures, cooling technology, etc. Water demands from most economic sectors are typically highest during summertime. For most systems, this coincides with peak electricity demand and consequently a high demand for thermal power plant cooling water. Supplies however are sometimes limited due to seasonal precipitation fluctuations including sporadic droughts that lead to water scarcity. When this occurs there is an impact on both unit commitments and the real-time dispatch. In this work, we model the cooling efficiency of several different types of thermal power generation technologies as a function of power output level and daily temperature profiles. Unit specific relationships are then integrated in a power grid operational model that minimizes total grid production cost while reliably meeting hourly loads. Grid operation is subject to power plant physical constraints, transmission limitations, water availability and environmental constraints such as power plant water exit temperature limits. The model is applied to a standard IEEE-118 bus system under various water availability scenarios. Results show that water availability has a significant impact on power grid economics.

Emissions & Generation Resource Integrated Database (eGRID), eGRID2002 (with years 1996 - 2000 data)

EPA Pesticide Factsheets

The Emissions & Generation Resource Integrated Database (eGRID) is a comprehensive source of data on the environmental characteristics of almost all electric power generated in the United States. These environmental characteristics include air emissions for nitrogen oxides, sulfur dioxide, carbon dioxide, methane, nitrous oxide, and mercury; emissions rates; net generation; resource mix; and many other attributes. eGRID2002 (years 1996 through 2000 data) contains 16 Excel spreadsheets and the Technical Support Document, as well as the eGRID Data Browser, User's Manual, and Readme file. Archived eGRID data can be viewed as spreadsheets or by using the eGRID Data Browser. The eGRID spreadsheets can be manipulated by data users and enables users to view all the data underlying eGRID. The eGRID Data Browser enables users to view key data using powerful search features. Note that the eGRID Data Browser will not run on a Mac-based machine without Windows emulation.

Issues regarding the usage of MPPT techniques in micro grid systems

NASA Astrophysics Data System (ADS)

Szeidert, I.; Filip, I.; Dragan, F.; Gal, A.

2018-01-01

The main objective of the control strategies applied at hybrid micro grid systems (wind/hydro/solar), that function based on maximum power point tracking (MPPT) techniques is to improve the conversion system’s efficiency and to preserve the quality of the generated electrical energy (voltage and power factor). One of the main goals of maximum power point tracking strategy is to achieve the harvesting of the maximal possible energy within a certain time period. In order to implement the control strategies for micro grid, there are typically required specific transducers (sensor for wind speed, optical rotational transducers, etc.). In the technical literature, several variants of the MPPT techniques are presented and particularized at some applications (wind energy conversion systems, solar systems, hydro plants, micro grid hybrid systems). The maximum power point tracking implementations are mainly based on two-level architecture. The lower level controls the main variable and the superior level represents the MPPT control structure. The paper presents micro grid structures developed at Politehnica University Timisoara (PUT) within the frame of a research grant. The paper is focused on the application of MPPT strategies on hybrid micro grid systems. There are presented several structures and control strategies and are highlighted their advantages and disadvantages, together with practical implementation guidelines.

Load Balancing Strategies for Multi-Block Overset Grid Applications

NASA Technical Reports Server (NTRS)

Djomehri, M. Jahed; Biswas, Rupak; Lopez-Benitez, Noe; Biegel, Bryan (Technical Monitor)

2002-01-01

The multi-block overset grid method is a powerful technique for high-fidelity computational fluid dynamics (CFD) simulations about complex aerospace configurations. The solution process uses a grid system that discretizes the problem domain by using separately generated but overlapping structured grids that periodically update and exchange boundary information through interpolation. For efficient high performance computations of large-scale realistic applications using this methodology, the individual grids must be properly partitioned among the parallel processors. Overall performance, therefore, largely depends on the quality of load balancing. In this paper, we present three different load balancing strategies far overset grids and analyze their effects on the parallel efficiency of a Navier-Stokes CFD application running on an SGI Origin2000 machine.

Impact of wind generator infed on dynamic performance of a power system

NASA Astrophysics Data System (ADS)

Alam, Md. Ahsanul

Wind energy is one of the most prominent sources of electrical energy in the years to come. A tendency to increase the amount of electricity generation from wind turbine can be observed in many countries. One of the major concerns related to the high penetration level of the wind energy into the existing power grid is its influence on power system dynamic performance. In this thesis, the impact of wind generation system on power system dynamic performance is investigated through detailed dynamic modeling of the entire wind generator system considering all the relevant components. Nonlinear and linear models of a single machine as well as multimachine wind-AC system have been derived. For the dynamic model of integrated wind-AC system, a general transformation matrix is determined for the transformation of machine and network quantities to a common reference frame. Both time-domain and frequency domain analyses on single machine and multimachine systems have been carried out. The considered multimachine systems are---A 4 machine 12 bus system, and 10 machine 39 bus New England system. Through eigenvalue analysis, impact of asynchronous wind system on overall network damping has been quantified and modes responsible for the instability have been identified. Over with a number of simulation studies it is observed that for a induction generator based wind generation system, the fixed capacitor located at the generator terminal cannot normally cater for the reactive power demand during the transient disturbances like wind gust and fault on the system. For weak network connection, system instability may be initiated because of induction generator terminal voltage collapse under certain disturbance conditions. Incorporation of dynamic reactive power compensation scheme through either variable susceptance control or static compensator (STATCOM) is found to improve the dynamic performance significantly. Further improvement in transient profile has been brought in by supporting STATCOM with bulk energy storage devices. Two types of energy storage system (ESS) have been considered---battery energy storage system, and supercapacitor based energy storage system. A decoupled P -- Q control strategy has been implemented on STATCOM/ESS. It is observed that wind generators when supported by STATCOM/ESS can achieve significant withstand capability in the presence of grid fault of reasonable duration. It experiences almost negligible rotor speed variation, maintains constant terminal voltage, and resumes delivery of smoothed (almost transient free) power to the grid immediately after the fault is cleared. Keywords: Wind energy, induction generator, dynamic performance of wind generators, energy storage system, decoupled P -- Q control, multimachine system.

Analysis of the design and economics of molten carbonate fuel cell tri-generation systems providing heat and power for commercial buildings and H2 for FC vehicles

NASA Astrophysics Data System (ADS)

Li, Xuping; Ogden, Joan; Yang, Christopher

2013-11-01

This study models the operation of molten carbonate fuel cell (MCFC) tri-generation systems for “big box” store businesses that combine grocery and retail business, and sometimes gasoline retail. Efficiency accounting methods and parameters for MCFC tri-generation systems have been developed. Interdisciplinary analysis and an engineering/economic model were applied for evaluating the technical, economic, and environmental performance of distributed MCFC tri-generation systems, and for exploring the optimal system design. Model results show that tri-generation is economically competitive with the conventional system, in which the stores purchase grid electricity and NG for heat, and sell gasoline fuel. The results are robust based on sensitivity analysis considering the uncertainty in energy prices and capital cost. Varying system sizes with base case engineering inputs, energy prices, and cost assumptions, it is found that there is a clear tradeoff between the portion of electricity demand covered and the capital cost increase of bigger system size. MCFC Tri-generation technology provides lower emission electricity, heat, and H2 fuel. With NG as feedstock the CO2 emission can be reduced by 10%-43.6%, depending on how the grid electricity is generated. With renewable methane as feedstock CO2 emission can be further reduced to near zero.

Modular Multi-Sensor Display System Design Study. Volume 2. Detail Design and Application Analysis

DTIC Science & Technology

1974-08-01

control grid . 2. Horizontal AFC/Deflection Module - Generates horizontal sweep signals from input syncs to provide 525 to 1023 line television raster...separation, and gener- ate composite blanking for the CRT control grid . Signal Number of Lines Signal Type Characteristics Input Interface Composite...SEPERATOR DC RESTORA- TION l_i BLANKING VERT DRIVE ■♦ Bl" CRT " CATHODE * _fc> BRIGHTNESS ^ (FRONT PANEL) .CRT GRID ■♦• COMP SYNC Figure

Electrolyzers Enhancing Flexibility in Electric Grids

DOE PAGES

Mohanpurkar, Manish; Luo, Yusheng; Terlip, Danny; ...

2017-11-10

This paper presents a real-time simulation with a hardware-in-the-loop (HIL)-based approach for verifying the performance of electrolyzer systems in providing grid support. Hydrogen refueling stations may use electrolyzer systems to generate hydrogen and are proposed to have the potential of becoming smarter loads that can proactively provide grid services. On the basis of experimental findings, electrolyzer systems with balance of plant are observed to have a high level of controllability and hence can add flexibility to the grid from the demand side. A generic front end controller (FEC) is proposed, which enables an optimal operation of the load on themore » basis of market and grid conditions. This controller has been simulated and tested in a real-time environment with electrolyzer hardware for a performance assessment. It can optimize the operation of electrolyzer systems on the basis of the information collected by a communication module. Real-time simulation tests are performed to verify the performance of the FEC-driven electrolyzers to provide grid support that enables flexibility, greater economic revenue, and grid support for hydrogen producers under dynamic conditions. In conclusion, the FEC proposed in this paper is tested with electrolyzers, however, it is proposed as a generic control topology that is applicable to any load.« less

Grid Integration and the Carrying Capacity of the U.S. Grid to Incorporate Variable Renewable Energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cochran, Jaquelin; Denholm, Paul; Speer, Bethany

2015-04-23

In the United States and elsewhere, renewable energy (RE) generation supplies an increasingly large percentage of annual demand, including nine U.S. states where wind comprised over 10% of in-state generation in 2013. This white paper summarizes the challenges to integrating increasing amounts of variable RE, identifies emerging practices in power system planning and operation that can facilitate grid integration, and proposes a unifying concept—economic carrying capacity—that can provide a framework for evaluating actions to accommodate higher penetrations of RE. There is growing recognition that while technical challenges to variable RE integration are real, they can generally be addressed via amore » variety of solutions that vary in implementation cost. As a result, limits to RE penetration are primarily economic, driven by factors that include transmission and the flexibility of the power grid to balance supply and demand. This limit can be expressed as economic carrying capacity, or the point at which variable RE is no longer economically competitive or desirable to the system or society.« less

A novel control strategy for enhancing the LVRT and voltage support capabilities of DFIG

NASA Astrophysics Data System (ADS)

Shen, Yangwu; Zhang, Bin; Liang, Liqing; Cui, Ting

2018-02-01

A novel integrated control strategy is proposed in this paper to enhance the low voltage ride through capacity for the double-fed induction generator by equipping an energy storage system. The energy storage system is installed into the DC-link capacitor of the DFIG and used to control the DC-link voltage during normal or transient operations. The energy storage device will absorb or compensate the power difference between the captured wind power and the power injected to the grid during the normal and transient period, and the grid side converter can be free from maintaining the voltage stability of the DC-link capacitor. Thus, the grid-side converter is changed to reactive power support while the rotor-side converter is used to control the maximum power production during normal operation. The grid-side converter and rotor-side converter will act as reactive power sources to further enhance the voltage support capability of double-fed induction generator during the transient period. Numerical Simulation are performed to validate the effectiveness of the proposed control designs.

Energy Theft in the Advanced Metering Infrastructure

NASA Astrophysics Data System (ADS)

McLaughlin, Stephen; Podkuiko, Dmitry; McDaniel, Patrick

Global energy generation and delivery systems are transitioning to a new computerized "smart grid". One of the principle components of the smart grid is an advanced metering infrastructure (AMI). AMI replaces the analog meters with computerized systems that report usage over digital communication interfaces, e.g., phone lines. However, with this infrastructure comes new risk. In this paper, we consider adversary means of defrauding the electrical grid by manipulating AMI systems. We document the methods adversaries will use to attempt to manipulate energy usage data, and validate the viability of these attacks by performing penetration testing on commodity devices. Through these activities, we demonstrate that not only is theft still possible in AMI systems, but that current AMI devices introduce a myriad of new vectors for achieving it.

Grid Integration of Single Stage Solar PV System using Three-level Voltage Source Converter

NASA Astrophysics Data System (ADS)

Hussain, Ikhlaq; Kandpal, Maulik; Singh, Bhim

2016-08-01

This paper presents a single stage solar PV (photovoltaic) grid integrated power generating system using a three level voltage source converter (VSC) operating at low switching frequency of 900 Hz with robust synchronizing phase locked loop (RS-PLL) based control algorithm. To track the maximum power from solar PV array, an incremental conductance algorithm is used and this maximum power is fed to the grid via three-level VSC. The use of single stage system with three level VSC offers the advantage of low switching losses and the operation at high voltages and high power which results in enhancement of power quality in the proposed system. Simulated results validate the design and control algorithm under steady state and dynamic conditions.

Smart-DS: Synthetic Models for Advanced, Realistic Testing: Distribution Systems and Scenarios

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishnan, Venkat K; Palmintier, Bryan S; Hodge, Brian S

The National Renewable Energy Laboratory (NREL) in collaboration with Massachusetts Institute of Technology (MIT), Universidad Pontificia Comillas (Comillas-IIT, Spain) and GE Grid Solutions, is working on an ARPA-E GRID DATA project, titled Smart-DS, to create: 1) High-quality, realistic, synthetic distribution network models, and 2) Advanced tools for automated scenario generation based on high-resolution weather data and generation growth projections. Through these advancements, the Smart-DS project is envisioned to accelerate the development, testing, and adoption of advanced algorithms, approaches, and technologies for sustainable and resilient electric power systems, especially in the realm of U.S. distribution systems. This talk will present themore » goals and overall approach of the Smart-DS project, including the process of creating the synthetic distribution datasets using reference network model (RNM) and the comprehensive validation process to ensure network realism, feasibility, and applicability to advanced use cases. The talk will provide demonstrations of early versions of synthetic models, along with the lessons learnt from expert engagements to enhance future iterations. Finally, the scenario generation framework, its development plans, and co-ordination with GRID DATA repository teams to house these datasets for public access will also be discussed.« less

Vehicle-to-Grid Automatic Load Sharing with Driver Preference in Micro-Grids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yubo; Nazaripouya, Hamidreza; Chu, Chi-Cheng

Integration of Electrical Vehicles (EVs) with power grid not only brings new challenges for load management, but also opportunities for distributed storage and generation. This paper comprehensively models and analyzes distributed Vehicle-to-Grid (V2G) for automatic load sharing with driver preference. In a micro-grid with limited communications, V2G EVs need to decide load sharing based on their own power and voltage profile. A droop based controller taking into account driver preference is proposed in this paper to address the distributed control of EVs. Simulations are designed for three fundamental V2G automatic load sharing scenarios that include all system dynamics of suchmore » applications. Simulation results demonstrate that active power sharing is achieved proportionally among V2G EVs with consideration of driver preference. In additional, the results also verify the system stability and reactive power sharing analysis in system modelling, which sheds light on large scale V2G automatic load sharing in more complicated cases.« less

Parametric Geometry, Structured Grid Generation, and Initial Design Study for REST-Class Hypersonic Inlets

NASA Technical Reports Server (NTRS)

Ferlemann, Paul G.; Gollan, Rowan J.

2010-01-01

Computational design and analysis of three-dimensional hypersonic inlets with shape transition has been a significant challenge due to the complex geometry and grid required for three-dimensional viscous flow calculations. Currently, the design process utilizes an inviscid design tool to produce initial inlet shapes by streamline tracing through an axisymmetric compression field. However, the shape is defined by a large number of points rather than a continuous surface and lacks important features such as blunt leading edges. Therefore, a design system has been developed to parametrically construct true CAD geometry and link the topology of a structured grid to the geometry. The Adaptive Modeling Language (AML) constitutes the underlying framework that is used to build the geometry and grid topology. Parameterization of the CAD geometry allows the inlet shapes produced by the inviscid design tool to be generated, but also allows a great deal of flexibility to modify the shape to account for three-dimensional viscous effects. By linking the grid topology to the parametric geometry, the GridPro grid generation software can be used efficiently to produce a smooth hexahedral multiblock grid. To demonstrate the new capability, a matrix of inlets were designed by varying four geometry parameters in the inviscid design tool. The goals of the initial design study were to explore inviscid design tool geometry variations with a three-dimensional analysis approach, demonstrate a solution rate which would enable the use of high-fidelity viscous three-dimensional CFD in future design efforts, process the results for important performance parameters, and perform a sample optimization.

Tehachapi Wind Energy Storage Project - Technology Performance Report #3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pinsky, Naum; O'Neill, Lori

The TSP is located at SCE’s Monolith Substation in Tehachapi, California. The 8 MW, 4 hours (32 MWh) BESS is housed in a 6,300 square foot facility and 2 x 4 MW/4.5 MVA smart inverters are on a concrete pad adjacent to the BESS facility. The project will evaluate the capabilities of the BESS to improve grid performance and assist in the integration of large-scale intermittent generation, e.g., wind. Project performance was measured by 13 specific operational uses: providing voltage support and grid stabilization, decreasing transmission losses, diminishing congestion, increasing system reliability, deferring transmission investment, optimizing renewable-related transmission, providing systemmore » capacity and resources adequacy, integrating renewable energy (smoothing), shifting wind generation output, frequency regulation, spin/non-spin replacement reserves, ramp management, and energy price arbitrage. Most of the operations either shift other generation resources to meet peak load and other electricity system needs with stored electricity, or resolve grid stability and capacity concerns that result from the interconnection of intermittent generation. SCE also demonstrated the ability of lithium ion battery storage to provide nearly instantaneous maximum capacity for supply-side ramp rate control to minimize the need for fossil fuel-powered back-up generation. The project began in October, 2010 and will continue through December, 2016.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Jay Tillay

For three years, Sandia National Laboratories, Georgia Institute of Technology, and University of Illinois at Urbana-Champaign investigated a smart grid vision in which renewable-centric Virtual Power Plants (VPPs) provided ancillary services with interoperable distributed energy resources (DER). This team researched, designed, built, and evaluated real-time VPP designs incorporating DER forecasting, stochastic optimization, controls, and cyber security to construct a system capable of delivering reliable ancillary services, which have been traditionally provided by large power plants or other dedicated equipment. VPPs have become possible through an evolving landscape of state and national interconnection standards, which now require DER to include grid-supportmore » functionality and communications capabilities. This makes it possible for third party aggregators to provide a range of critical grid services such as voltage regulation, frequency regulation, and contingency reserves to grid operators. This paradigm (a) enables renewable energy, demand response, and energy storage to participate in grid operations and provide grid services, (b) improves grid reliability by providing additional operating reserves for utilities, independent system operators (ISOs), and regional transmission organization (RTOs), and (c) removes renewable energy high-penetration barriers by providing services with photovoltaics and wind resources that traditionally were the jobs of thermal generators. Therefore, it is believed VPP deployment will have far-reaching positive consequences for grid operations and may provide a robust pathway to high penetrations of renewables on US power systems. In this report, we design VPPs to provide a range of grid-support services and demonstrate one VPP which simultaneously provides bulk-system energy and ancillary reserves.« less

Amelioration de la qualite d'energie d'un systeme de conversion d'energie eolienne a base de machine asynchrone a double alimentation et connecte au reseau electrique =

NASA Astrophysics Data System (ADS)

Abderrahim, Iheb

Wind power generation has grown strongly in the last decade. This results in the development of Wind Energy Conversion System WECS at the levels of modeling and electrical control. Modern WECS operate at varying wind speeds and are equipped with synchronous and asynchronous generators. Among these generators, the Doubly-Fed Induction Generator (DFIG) offers several advantages and capabilities of active and reactive power in four quadrants. WECS based DFIG also causes less conversion costs and minimum energy losses compared with a WECS based on a synchronous generator powered entirely by full scale of power converters. The connection of such a system to the electrical distribution network involves bidirectional operation of networks. This is clearly established in sub and super synchronous operating modes of DFIG. The grid provides the active power to the rotor of DFIG in sub synchronous operating mode and receives the active power of the rotor in super synchronous operating mode of DFIG. Energy quality is thus of major importance during the integration of wind power to the grid. Poor wave quality can affect network stability and could even cause major problems and consequences. This is even more critical where non-linear loads such as the switching power supplies and variable speed drives, are connected to the grid. The idea of this research work is how to mitigate the problems associated with the wave quality while ensuring better implementation of DFIG so that the whole of WECS remains insensitive to external disturbances and parametric variations. The Grid Side Converter (GSC) must be able to compensate harmonics, current unbalance and reactive power injected by a nonlinear three-phase unbalanced load connected to the grid. In addition to these innovative features to improve the conditions of operation of the grid, it provides also the power flow during different modes of operation of the DFIG. It is considered a simple, efficient and cost competitive solution by saving the use of other power equipment. At the same time, the energy efficiency of wind power conversion chain should be improved by extracting the MPPT. Searching allows us to select vector control and control in synchronous reference to achieve these objectives. WECS based DFIG is simulated in MATLAB SIMULINK in the presence of a non-linear balanced and unbalanced three-phase load.

Smart nanogrid systems for disaster mitigation employing deployable renewable energy harvesting devices

NASA Astrophysics Data System (ADS)

Ghasemi-Nejhad, Mehrdad N.; Menendez, Michael; Minei, Brenden; Wong, Kyle; Gabrick, Caton; Thornton, Matsu; Ghorbani, Reza

2016-04-01

This paper explains the development of smart nanogrid systems for disaster mitigation employing deployable renewable energy harvesting, or Deployable Disaster Devices (D3), where wind turbines and solar panels are developed in modular forms, which can be tied together depending on the needed power. The D3 packages/units can be used: (1) as a standalone unit in case of a disaster where no source of power is available, (2) for a remote location such as a farm, camp site, or desert (3) for a community that converts energy usage from fossil fuels to Renewable Energy (RE) sources, or (4) in a community system as a source of renewable energy for grid-tie or off-grid operation. In Smart D3 system, the power is generated (1) for consumer energy needs, (2) charge storage devices (such as batteries, capacitors, etc.), (3) to deliver power to the network when the smart D3 nano-grid is tied to the network and when the power generation is larger than consumption and storage recharge needs, or (4) to draw power from the network when the smart D3 nano-grid is tied to the network and when the power generation is less than consumption and storage recharge needs. The power generated by the Smart D3 systems are routed through high efficiency inverters for proper DC to DC or DC to AC for final use or grid-tie operations. The power delivery from the D3 is 220v AC, 110v AC and 12v DC provide proper power for most electrical and electronic devices worldwide. The power supply is scalable, using a modular system that connects multiple units together. This are facilitated through devices such as external Input-Output or I/O ports. The size of the system can be scaled depending on how many accessory units are connected to the I/O ports on the primary unit. The primary unit is the brain of the system allowing for smart switching and load balancing of power input and smart regulation of power output. The Smart D3 systems are protected by ruggedized weather proof casings allowing for operation in a variety of extreme environments and can be parachuted into the needed locations. The Smart Nanogrid Systems will have sensors that will sense the environmental conditions for the wind turbines and solar panels for maximum energy harvesting as well as identifying the appliances in use. These signal will be sent to a control system to send signal to the energy harvester actuators to maximize the power generation as well as regulating the power, i.e., either send the power to the appliances and consumer devices or send the power to the batteries and capacitors for energy storage, if the power is being generated but there are no consumer appliances in use, making it a "smart nanogrid deployable renewable energy harvesting system."

Decentralized Energy Management System for Networked Microgrids in Grid-connected and Islanded Modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhaoyu; Chen, Bokan; Wang, Jianhui

This paper proposes a decentralized energy management system (EMS) for the coordinated operation of networked Microgirds (MGs) in a distribution system. In the grid-connected mode, the distribution network operator (DNO) and each MG are considered as distinct entities with individual objectives to minimize their own operation costs. It is assumed that both dispatchable and renewable energy source (RES)-based distributed generators (DGs) exist in the distribution network and the networked MGs. In order to coordinate the operation of all entities, we apply a decentralized bi-level algorithm to solve the problem with the first level to conduct negotiations among all entities andmore » the second level to update the non-converging penalties. In the islanded mode, the objective of each MG is to maintain a reliable power supply to its customers. In order to take into account the uncertainties of DG outputs and load consumption, we formulate the problems as two-stage stochastic programs. The first stage is to determine base generation setpoints based on the forecasts and the second stage is to adjust the generation outputs based on the realized scenarios. Case studies of a distribution system with networked MGs demonstrate the effectiveness of the proposed methodology in both grid-connected and islanded modes.« less

The Optimization dispatching of Micro Grid Considering Load Control

NASA Astrophysics Data System (ADS)

Zhang, Pengfei; Xie, Jiqiang; Yang, Xiu; He, Hongli

2018-01-01

This paper proposes an optimization control of micro-grid system economy operation model. It coordinates the new energy and storage operation with diesel generator output, so as to achieve the economic operation purpose of micro-grid. In this paper, the micro-grid network economic operation model is transformed into mixed integer programming problem, which is solved by the mature commercial software, and the new model is proved to be economical, and the load control strategy can reduce the charge and discharge times of energy storage devices, and extend the service life of the energy storage device to a certain extent.

Domain Decomposition By the Advancing-Partition Method for Parallel Unstructured Grid Generation

NASA Technical Reports Server (NTRS)

Pirzadeh, Shahyar Z.; Zagaris, George

2009-01-01

A new method of domain decomposition has been developed for generating unstructured grids in subdomains either sequentially or using multiple computers in parallel. Domain decomposition is a crucial and challenging step for parallel grid generation. Prior methods are generally based on auxiliary, complex, and computationally intensive operations for defining partition interfaces and usually produce grids of lower quality than those generated in single domains. The new technique, referred to as "Advancing Partition," is based on the Advancing-Front method, which partitions a domain as part of the volume mesh generation in a consistent and "natural" way. The benefits of this approach are: 1) the process of domain decomposition is highly automated, 2) partitioning of domain does not compromise the quality of the generated grids, and 3) the computational overhead for domain decomposition is minimal. The new method has been implemented in NASA's unstructured grid generation code VGRID.

Control of Grid Connected Photovoltaic System Using Three-Level T-Type Inverter

NASA Astrophysics Data System (ADS)

Zorig, Abdelmalik; Belkeiri, Mohammed; Barkat, Said; Rabhi, Abdelhamid

2016-08-01

Three-level T-Type inverter (3LT2I) topology has numerous advantageous compared to three-level neutral-point-clamped (NPC) inverter. The main benefits of 3LT2I inverter are the efficiency, inverter cost, switching losses, and the quality of output voltage waveforms. In this paper, a photovoltaic distributed generation system based on dual-stage topology of DC-DC boost converter and 3LT2I is introduced. To that end, a decoupling control strategy of 3LT2I is proposed to control the current injected into the grid, reactive power compensation, and DC-link voltage. The resulting system is able to extract the maximum power from photovoltaic generator, to achieve sinusoidal grid currents, and to ensure reactive power compensation. The voltage-balancing control of two split DC capacitors of the 3LT2I is achieved using three-level space vector modulation with balancing strategy based on the effective use of the redundant switching states of the inverter voltage vectors. The proposed system performance is investigated at different operating conditions.

Interactive grid generation for turbomachinery flow field simulations

NASA Technical Reports Server (NTRS)

Choo, Yung K.; Eiseman, Peter R.; Reno, Charles

1988-01-01

The control point form of algebraic grid generation presented provides the means that are needed to generate well structured grids for turbomachinery flow simulations. It uses a sparse collection of control points distributed over the flow domain. The shape and position of coordinate curves can be adjusted from these control points while the grid conforms precisely to all boundaries. An interactive program called TURBO, which uses the control point form, is being developed. Basic features of the code are discussed and sample grids are presented. A finite volume LU implicit scheme is used to simulate flow in a turbine cascade on the grid generated by the program.

Interactive grid generation for turbomachinery flow field simulations

NASA Technical Reports Server (NTRS)

Choo, Yung K.; Reno, Charles; Eiseman, Peter R.

1988-01-01

The control point form of algebraic grid generation presented provides the means that are needed to generate well structured grids of turbomachinery flow simulations. It uses a sparse collection of control points distributed over the flow domain. The shape and position of coordinate curves can be adjusted from these control points while the grid conforms precisely to all boundaries. An interactive program called TURBO, which uses the control point form, is being developed. Basic features of the code are discussed and sample grids are presented. A finite volume LU implicit scheme is used to simulate flow in a turbine cascade on the grid generated by the program.

Sensitivities and Tipping Points of Power System Operations to Fluctuations Caused by Water Availability and Fuel Prices

NASA Astrophysics Data System (ADS)

O'Connell, M.; Macknick, J.; Voisin, N.; Fu, T.

2017-12-01

The western US electric grid is highly dependent upon water resources for reliable operation. Hydropower and water-cooled thermoelectric technologies represent 67% of generating capacity in the western region of the US. While water resources provide a significant amount of generation and reliability for the grid, these same resources can represent vulnerabilities during times of drought or low flow conditions. A lack of water affects water-dependent technologies and can result in more expensive generators needing to run in order to meet electric grid demand, resulting in higher electricity prices and a higher cost to operate the grid. A companion study assesses the impact of changes in water availability and air temperatures on power operations by directly derating hydro and thermo-electric generators. In this study we assess the sensitivities and tipping points of water availability compared with higher fuel prices in electricity sector operations. We evaluate the impacts of varying electricity prices by modifying fuel prices for coal and natural gas. We then analyze the difference in simulation results between changes in fuel prices in combination with water availability and air temperature variability. We simulate three fuel price scenarios for a 2010 baseline scenario along with 100 historical and future hydro-climate conditions. We use the PLEXOS electricity production cost model to optimize power system dispatch and cost decisions under each combination of fuel price and water constraint. Some of the metrics evaluated are total production cost, generation type mix, emissions, transmission congestion, and reserve procurement. These metrics give insight to how strained the system is, how much flexibility it still has, and to what extent water resource availability or fuel prices drive changes in the electricity sector operations. This work will provide insights into current electricity operations as well as future cases of increased penetration of variable renewable generation technologies such as wind and solar.

Maximum power extraction under different vector-control schemes and grid-synchronization strategy of a wind-driven Brushless Doubly-Fed Reluctance Generator.

PubMed

Mousa, Mohamed G; Allam, S M; Rashad, Essam M

2018-01-01

This paper proposes an advanced strategy to synchronize the wind-driven Brushless Doubly-Fed Reluctance Generator (BDFRG) to the grid-side terminals. The proposed strategy depends mainly upon determining the electrical angle of the grid voltage, θ v and using the same transformation matrix of both the power winding and grid sides to ensure that the generated power-winding voltage has the same phase-sequence of the grid-side voltage. On the other hand, the paper proposes a vector-control (power-winding flux orientation) technique for maximum wind-power extraction under two schemes summarized as; unity power-factor operation and minimum converter-current. Moreover, a soft-starting method is suggested to avoid the employed converter over-current. The first control scheme is achieved by adjusting the command power-winding reactive power at zero for a unity power-factor operation. However, the second scheme depends on setting the command d-axis control-winding current at zero to maximize the ratio of the generator electromagnetic-torque per the converter current. This enables the system to get a certain command torque under minimum converter current. A sample of the obtained simulation and experimental results is presented to check the effectiveness of the proposed control strategies. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Inverter for Interchangeable Use as Current Source Inverter and Voltage Source Inverter for Interconnecting to Grid

NASA Astrophysics Data System (ADS)

Teruya, Daisuke; Masukawa, Shigeo; Iida, Shoji

We propose a novel inverter that can be operated either as a Current Source Inverter (CSI) or as a Voltage Source Inverter (VSI) by changing only the control signals. It is proper to apply it to the interconnecting system with renewal energy, such as photovoltaic cells or wind generation systems, to a grid. This inverter is usually operated as the CSI connected to the grid. Even if the energy source has a lower voltage than the grid, the energy can be supplied to the grid through the proposed inverter. The power factor can be briefly maintained at almost unity. When power supply from the grid is interrupted, the proposed circuit should be operated as the VSI in the stand-alone operation mode. In this way, the circuit can maintain a constant output voltage to the loads. In this paper, the proposed circuit configuration and the control schemes for both the CSI and the VSI are described. Further, the circuit characteristics for both are discussed experimentally.

DIRAC3 - the new generation of the LHCb grid software

NASA Astrophysics Data System (ADS)

Tsaregorodtsev, A.; Brook, N.; Casajus Ramo, A.; Charpentier, Ph; Closier, J.; Cowan, G.; Graciani Diaz, R.; Lanciotti, E.; Mathe, Z.; Nandakumar, R.; Paterson, S.; Romanovsky, V.; Santinelli, R.; Sapunov, M.; Smith, A. C.; Seco Miguelez, M.; Zhelezov, A.

2010-04-01

DIRAC, the LHCb community Grid solution, was considerably reengineered in order to meet all the requirements for processing the data coming from the LHCb experiment. It is covering all the tasks starting with raw data transportation from the experiment area to the grid storage, data processing up to the final user analysis. The reengineered DIRAC3 version of the system includes a fully grid security compliant framework for building service oriented distributed systems; complete Pilot Job framework for creating efficient workload management systems; several subsystems to manage high level operations like data production and distribution management. The user interfaces of the DIRAC3 system providing rich command line and scripting tools are complemented by a full-featured Web portal providing users with a secure access to all the details of the system status and ongoing activities. We will present an overview of the DIRAC3 architecture, new innovative features and the achieved performance. Extending DIRAC3 to manage computing resources beyond the WLCG grid will be discussed. Experience with using DIRAC3 by other user communities than LHCb and in other application domains than High Energy Physics will be shown to demonstrate the general-purpose nature of the system.

Grid generation for the solution of partial differential equations

NASA Technical Reports Server (NTRS)

Eiseman, Peter R.; Erlebacher, Gordon

1989-01-01

A general survey of grid generators is presented with a concern for understanding why grids are necessary, how they are applied, and how they are generated. After an examination of the need for meshes, the overall applications setting is established with a categorization of the various connectivity patterns. This is split between structured grids and unstructured meshes. Altogether, the categorization establishes the foundation upon which grid generation techniques are developed. The two primary categories are algebraic techniques and partial differential equation techniques. These are each split into basic parts, and accordingly are individually examined in some detail. In the process, the interrelations between the various parts are accented. From the established background in the primary techniques, consideration is shifted to the topic of interactive grid generation and then to adaptive meshes. The setting for adaptivity is established with a suitable means to monitor severe solution behavior. Adaptive grids are considered first and are followed by adaptive triangular meshes. Then the consideration shifts to the temporal coupling between grid generators and PDE-solvers. To conclude, a reflection upon the discussion, herein, is given.

Grid generation for the solution of partial differential equations

NASA Technical Reports Server (NTRS)

Eiseman, Peter R.; Erlebacher, Gordon

1987-01-01

A general survey of grid generators is presented with a concern for understanding why grids are necessary, how they are applied, and how they are generated. After an examination of the need for meshes, the overall applications setting is established with a categorization of the various connectivity patterns. This is split between structured grids and unstructured meshes. Altogether, the categorization establishes the foundation upon which grid generation techniques are developed. The two primary categories are algebraic techniques and partial differential equation techniques. These are each split into basic parts, and accordingly are individually examined in some detail. In the process, the interrelations between the various parts are accented. From the established background in the primary techniques, consideration is shifted to the topic of interactive grid generation and then to adaptive meshes. The setting for adaptivity is established with a suitable means to monitor severe solution behavior. Adaptive grids are considered first and are followed by adaptive triangular meshes. Then the consideration shifts to the temporal coupling between grid generators and PDE-solvers. To conclude, a reflection upon the discussion, herein, is given.

Diesel particulate filter regeneration via resistive surface heating

DOEpatents

Gonze, Eugene V; Ament, Frank

2013-10-08

An exhaust system that processes exhaust generated by an engine is provided. The system includes: a particulate filter (PF) that filters particulates from the exhaust wherein an upstream end of the PF receives exhaust from the engine; and a grid of electrically resistive material that is applied to an exterior upstream surface of the PF and that selectively heats exhaust passing through the grid to initiate combustion of particulates within the PF.

Autonomous Energy Grids: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kroposki, Benjamin D; Dall-Anese, Emiliano; Bernstein, Andrey

With much higher levels of distributed energy resources - variable generation, energy storage, and controllable loads just to mention a few - being deployed into power systems, the data deluge from pervasive metering of energy grids, and the shaping of multi-level ancillary-service markets, current frameworks to monitoring, controlling, and optimizing large-scale energy systems are becoming increasingly inadequate. This position paper outlines the concept of 'Autonomous Energy Grids' (AEGs) - systems that are supported by a scalable, reconfigurable, and self-organizing information and control infrastructure, can be extremely secure and resilient (self-healing), and self-optimize themselves in real-time for economic and reliable performancemore » while systematically integrating energy in all forms. AEGs rely on scalable, self-configuring cellular building blocks that ensure that each 'cell' can self-optimize when isolated from a larger grid as well as partaking in the optimal operation of a larger grid when interconnected. To realize this vision, this paper describes the concepts and key research directions in the broad domains of optimization theory, control theory, big-data analytics, and complex system modeling that will be necessary to realize the AEG vision.« less

Computing an operating parameter of a unified power flow controller

DOEpatents

Wilson, David G.; Robinett, III, Rush D.

2017-12-26

A Unified Power Flow Controller described herein comprises a sensor that outputs at least one sensed condition, a processor that receives the at least one sensed condition, a memory that comprises control logic that is executable by the processor; and power electronics that comprise power storage, wherein the processor causes the power electronics to selectively cause the power storage to act as one of a power generator or a load based at least in part upon the at least one sensed condition output by the sensor and the control logic, and wherein at least one operating parameter of the power electronics is designed to facilitate maximal transmittal of electrical power generated at a variable power generation system to a grid system while meeting power constraints set forth by the electrical power grid.

Computing an operating parameter of a unified power flow controller

DOEpatents

Wilson, David G; Robinett, III, Rush D

2015-01-06

A Unified Power Flow Controller described herein comprises a sensor that outputs at least one sensed condition, a processor that receives the at least one sensed condition, a memory that comprises control logic that is executable by the processor; and power electronics that comprise power storage, wherein the processor causes the power electronics to selectively cause the power storage to act as one of a power generator or a load based at least in part upon the at least one sensed condition output by the sensor and the control logic, and wherein at least one operating parameter of the power electronics is designed to facilitate maximal transmittal of electrical power generated at a variable power generation system to a grid system while meeting power constraints set forth by the electrical power grid.

Enabling a flexible exchange of energy of a photovoltaic plant with the grid by means of a controlled storage system

NASA Astrophysics Data System (ADS)

Lazzari, R.; Parma, C.; De Marco, A.; Bittanti, S.

2015-07-01

In this paper, we describe a control strategy for a photovoltaic (PV) power plant equipped with an energy storage system (ESS), based on lithium-ion battery. The plant consists of the following units: the PV generator, the energy storage system, the DC-bus and the inverter. The control, organised in a hierarchical manner, maximises the self-consumption of the local load unit. In particular, the ESS action performs power balance in case of low solar radiation or surplus of PV generation, thus managing the power exchange variability at the plant with the grid. The implemented control strategy is under testing in RSE pilot test facility in Milan, Italy.

Optimal management of stationary lithium-ion battery system in electricity distribution grids

NASA Astrophysics Data System (ADS)

Purvins, Arturs; Sumner, Mark

2013-11-01

The present article proposes an optimal battery system management model in distribution grids for stationary applications. The main purpose of the management model is to maximise the utilisation of distributed renewable energy resources in distribution grids, preventing situations of reverse power flow in the distribution transformer. Secondly, battery management ensures efficient battery utilisation: charging at off-peak prices and discharging at peak prices when possible. This gives the battery system a shorter payback time. Management of the system requires predictions of residual distribution grid demand (i.e. demand minus renewable energy generation) and electricity price curves (e.g. for 24 h in advance). Results of a hypothetical study in Great Britain in 2020 show that the battery can contribute significantly to storing renewable energy surplus in distribution grids while being highly utilised. In a distribution grid with 25 households and an installed 8.9 kW wind turbine, a battery system with rated power of 8.9 kW and battery capacity of 100 kWh can store 7 MWh of 8 MWh wind energy surplus annually. Annual battery utilisation reaches 235 cycles in per unit values, where one unit is a full charge-depleting cycle depth of a new battery (80% of 100 kWh).

Multi-agent coordination algorithms for control of distributed energy resources in smart grids

NASA Astrophysics Data System (ADS)

Cortes, Andres

Sustainable energy is a top-priority for researchers these days, since electricity and transportation are pillars of modern society. Integration of clean energy technologies such as wind, solar, and plug-in electric vehicles (PEVs), is a major engineering challenge in operation and management of power systems. This is due to the uncertain nature of renewable energy technologies and the large amount of extra load that PEVs would add to the power grid. Given the networked structure of a power system, multi-agent control and optimization strategies are natural approaches to address the various problems of interest for the safe and reliable operation of the power grid. The distributed computation in multi-agent algorithms addresses three problems at the same time: i) it allows for the handling of problems with millions of variables that a single processor cannot compute, ii) it allows certain independence and privacy to electricity customers by not requiring any usage information, and iii) it is robust to localized failures in the communication network, being able to solve problems by simply neglecting the failing section of the system. We propose various algorithms to coordinate storage, generation, and demand resources in a power grid using multi-agent computation and decentralized decision making. First, we introduce a hierarchical vehicle-one-grid (V1G) algorithm for coordination of PEVs under usage constraints, where energy only flows from the grid in to the batteries of PEVs. We then present a hierarchical vehicle-to-grid (V2G) algorithm for PEV coordination that takes into consideration line capacity constraints in the distribution grid, and where energy flows both ways, from the grid in to the batteries, and from the batteries to the grid. Next, we develop a greedy-like hierarchical algorithm for management of demand response events with on/off loads. Finally, we introduce distributed algorithms for the optimal control of distributed energy resources, i.e., generation and storage in a microgrid. The algorithms we present are provably correct and tested in simulation. Each algorithm is assumed to work on a particular network topology, and simulation studies are carried out in order to demonstrate their convergence properties to a desired solution.

Testbeds for Assessing Critical Scenarios in Power Control Systems

NASA Astrophysics Data System (ADS)

Dondossola, Giovanna; Deconinck, Geert; Garrone, Fabrizio; Beitollahi, Hakem

The paper presents a set of control system scenarios implemented in two testbeds developed in the context of the European Project CRUTIAL - CRitical UTility InfrastructurAL Resilience. The selected scenarios refer to power control systems encompassing information and communication security of SCADA systems for grid teleoperation, impact of attacks on inter-operator communications in power emergency conditions, impact of intentional faults on the secondary and tertiary control in power grids with distributed generators. Two testbeds have been developed for assessing the effect of the attacks and prototyping resilient architectures.

Electric Vehicle Charging and the California Power Sector: Evaluating the Effect of Location and Time on Greenhouse Gas Emissions

NASA Astrophysics Data System (ADS)

Sohnen, Julia Meagher

This thesis explores the implications of the increased adoption of plug-in electric vehicles in California through its effect on the operation of the state's electric grid. The well-to-wheels emissions associated with driving an electric vehicle depend on the resource mix of the electricity grid used to charge the battery. We present a new least-cost dispatch model, EDGE-NET, for the California electricity grid consisting of interconnected sub-regions that encompass the six largest state utilities that can be used to evaluate the impact of growing electric vehicle demand on existing power grid infrastructure system and energy resources. This model considers spatiality and temporal dynamics of energy demand and supply when determining the regional impacts of additional charging profiles on the current electricity network. Model simulation runs for one year show generation and transmission congestion to be reasonable similar to historical data. Model simulation results show that average emissions and system costs associated with electricity generation vary significantly by time of day, season, and location. Marginal cost and emissions also exhibit seasonal and diurnal differences, but show less spatial variation. Sensitivity of demand analysis shows that the relative changes to average emissions and system costs respond asymmetrically to increases and decreases in electricity demand. These results depend on grid mix at the time and the marginal power plant type. In minimizing total system cost, the model will choose to dispatch the lowest-cost resource to meet additional vehicle demand, regardless of location, as long as transmission capacity is available. Location of electric vehicle charging has a small effect on the marginal greenhouse gas emissions associated with additional generation, due to electricity losses in the transmission grid. We use a geographically explicit, charging assessment model for California to develop and compare the effects of two charging profiles. Comparison of these two basic scenarios points to savings in greenhouse gas emissions savings and operational costs from delayed charging of electric vehicles. Vehicle charging simulations confirm that plug-in electric vehicles alone are unlikely to require additional generation or transmission infrastructure. EDGE-NET was successfully benchmarked against historical data for the present grid but additional work is required to expand the model for future scenario evaluation. We discuss how the model might be adapted for high penetrations of variable renewable energy resources, and the use of grid storage. Renewable resources such as wind and solar vary in California vary significantly by time-of-day, season, and location. However, combination of multiple resources from different geographic regions through transmission grid interconnection is expected to help mitigate the impacts of variability. EDGE-NET can evaluate interaction of supply and demand through the existing transmission infrastructure and can identify any critical network bottlenecks or areas for expansion. For this reason, EDGE-NET will be an important tool to evaluate energy policy scenarios.

Investigation of advancing front method for generating unstructured grid

NASA Technical Reports Server (NTRS)

Thomas, A. M.; Tiwari, S. N.

1992-01-01

The advancing front technique is used to generate an unstructured grid about simple aerodynamic geometries. Unstructured grids are generated using VGRID2D and VGRID3D software. Specific problems considered are a NACA 0012 airfoil, a bi-plane consisting of two NACA 0012 airfoil, a four element airfoil in its landing configuration, and an ONERA M6 wing. Inviscid time dependent solutions are computed on these geometries using USM3D and the results are compared with standard test results obtained by other investigators. A grid convergence study is conducted for the NACA 0012 airfoil and compared with a structured grid. A structured grid is generated using GRIDGEN software and inviscid solutions computed using CFL3D flow solver. The results obtained by unstructured grid for NACA 0012 airfoil showed an asymmetric distribution of flow quantities, and a fine distribution of grid was required to remove this asymmetry. On the other hand, the structured grid predicted a very symmetric distribution, but when the total number of points were compared to obtain the same results it was seen that structured grid required more grid points.

GRID3O- FAST GENERATION OF MULTILEVEL, THREE-DIMENSIONAL BOUNDARY-CONFORMING O-TYPE COMPUTATIONAL GRIDS

NASA Technical Reports Server (NTRS)

Dulikravich, D. S.

1994-01-01

A fast algorithm has been developed for accurately generating boundary-conforming, three-dimensional consecutively refined computational grids applicable to arbitrary wing-body and axial turbomachinery geometries. This algorithm has been incorporated into the GRID3O computer program. The method employed in GRID3O is based on using an analytic function to generate two-dimensional grids on a number of coaxial axisymmetric surfaces positioned between the centerbody and the outer radial boundary. These grids are of the O-type and are characterized by quasi-orthogonality, geometric periodicity, and an adequate resolution throughout the flow field. Because the built-in nonorthogonal coordinate stretching and shearing cause the grid lines leaving the blade or wing trailing-edge to end at downstream infinity, use of the generated grid simplifies the numerical treatment of three-dimensional trailing vortex sheets. The GRID3O program is written in FORTRAN IV for batch execution and has been implemented on an IBM 370 series computer with a central memory requirement of approximately 450K of 8 bit bytes. The GRID3O program was developed in 1981.

Irvine Smart Grid Demonstration, a Regional Smart Grid Demonstration Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yinger, Robert; Irwin, Mark

ISGD was a comprehensive demonstration that spanned the electricity delivery system and extended into customer homes. The project used phasor measurement technology to enable substation-level situational awareness, and demonstrated SCE’s next-generation substation automation system. It extended beyond the substation to evaluate the latest generation of distribution automation technologies, including looped 12-kV distribution circuit topology using URCIs. The project team used DVVC capabilities to demonstrate CVR. In customer homes, the project evaluated HAN devices such as smart appliances, programmable communicating thermostats, and home energy management components. The homes were also equipped with energy storage, solar PV systems, and a number ofmore » energy efficiency measures (EEMs). The team used one block of homes to evaluate strategies and technologies for achieving ZNE. A home achieves ZNE when it produces at least as much renewable energy as the amount of energy it consumes annually. The project also assessed the impact of device-specific demand response (DR), as well as load management capabilities involving energy storage devices and plug-in electric vehicle charging equipment. In addition, the ISGD project sought to better understand the impact of ZNE homes on the electric grid. ISGD’s SENet enabled end-to-end interoperability between multiple vendors’ systems and devices, while also providing a level of cybersecurity that is essential to smart grid development and adoption across the nation. The ISGD project includes a series of sub-projects grouped into four logical technology domains: Smart Energy Customer Solutions, Next-Generation Distribution System, Interoperability and Cybersecurity, and Workforce of the Future. Section 2.3 provides a more detailed overview of these domains.« less

Workshop on Grid Generation and Related Areas

NASA Technical Reports Server (NTRS)

1992-01-01

A collection of papers given at the Workshop on Grid Generation and Related Areas is presented. The purpose of this workshop was to assemble engineers and scientists who are currently working on grid generation for computational fluid dynamics (CFD), surface modeling, and related areas. The objectives were to provide an informal forum on grid generation and related topics, to assess user experience, to identify needs, and to help promote synergy among engineers and scientists working in this area. The workshop consisted of four sessions representative of grid generation and surface modeling research and application within NASA LeRC. Each session contained presentations and an open discussion period.

Comparative hybrid and digital simulation studies of the behaviour of a wind generator equipped with a static frequency converter

NASA Astrophysics Data System (ADS)

Dube, B.; Lefebvre, S.; Perocheau, A.; Nakra, H. L.

1988-01-01

This paper describes the comparative results obtained from digital and hybrid simulation studies on a variable speed wind generator interconnected to the utility grid. The wind generator is a vertical-axis Darrieus type coupled to a synchronous machine by a gear-box; the synchronous machine is connected to the AC utility grid through a static frequency converter. Digital simulation results have been obtained using CSMP software; these results are compared with those obtained from a real-time hybrid simulator that in turn uses a part of the IREQ HVDC simulator. The agreement between hybrid and digital simulation results is generally good. The results demonstrate that the digital simulation reproduces the dynamic behavior of the system in a satisfactory manner and thus constitutes a valid tool for the design of the control systems of the wind generator.

Power in the loop real time simulation platform for renewable energy generation

NASA Astrophysics Data System (ADS)

Li, Yang; Shi, Wenhui; Zhang, Xing; He, Guoqing

2018-02-01

Nowadays, a large scale of renewable energy sources has been connecting to power system and the real time simulation platform is widely used to carry out research on integration control algorithm, power system stability etc. Compared to traditional pure digital simulation and hardware in the loop simulation, power in the loop simulation has higher accuracy and degree of reliability. In this paper, a power in the loop analog digital hybrid simulation platform has been built and it can be used not only for the single generation unit connecting to grid, but also for multiple new energy generation units connecting to grid. A wind generator inertia control experiment was carried out on the platform. The structure of the inertia control platform was researched and the results verify that the platform is up to need for renewable power in the loop real time simulation.

Systems and methods that generate height map models for efficient three dimensional reconstruction from depth information

DOEpatents

Frahm, Jan-Michael; Pollefeys, Marc Andre Leon; Gallup, David Robert

2015-12-08

Methods of generating a three dimensional representation of an object in a reference plane from a depth map including distances from a reference point to pixels in an image of the object taken from a reference point. Weights are assigned to respective voxels in a three dimensional grid along rays extending from the reference point through the pixels in the image based on the distances in the depth map from the reference point to the respective pixels, and a height map including an array of height values in the reference plane is formed based on the assigned weights. An n-layer height map may be constructed by generating a probabilistic occupancy grid for the voxels and forming an n-dimensional height map comprising an array of layer height values in the reference plane based on the probabilistic occupancy grid.

Grid-connected integrated community energy system. Phase II, Stage 2, final report. Preliminary design pyrolysis facility. [Andco-Torrax system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

The University of Minnesota is studying and planning a grid connected integrated community energy system to include disposal of wastes from health centers and utilizing the heat generated. The University of Minnesota has purchased the so called Southeast Generating Station from the Northern States Power Company. This plant contains two coal-fired boilers that will be retrofitted to burn low-sulfur Montana coal. Building modifications and additions will be made to support the components of the Andco-Torrax system and integrate the system with the rest of the plant. The Andco-Torrax system is a new high-temperature refuse-conversion process known technically as slagging pyrolysis.more » Although the pyrolysis of solid waste is a relatively new innovation, pyrolysis processes have been used for years by industry. This report covers the preliminary design and operation of the system. (MCW)« less

Future Roles of Milli-, Micro-, and Nano- Grids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marnay, Chris; Nordman, Bruce; Lai, Judy

Although it has slowed considerably, consumption of electricity continues to grow in developed economies. Further, there are some unknowns which might accelerate this growth, such as electrification of vehicle fleets and geothermal heat pump space and water heating. Most analysts anticipate that distributed energy resources (DER) will provide a large share of the expanded generation capacity required to meet this seemingly inexorably increasing electricity demand. Further, given the urgency of tackling the climate change problem, most of the added assets must be carbonfree renewables or nuclear, end-use efficiency improvements, or highly efficient fossil-fired technologies. In developed economies worldwide, the currentmore » power delivery paradigm has been in place for more than a century, i.e. since the emergence of polyphase AC systems around the turn of the last century. A key feature of this structure is that, in principle, universal service is delivered at a consistent level of power quality and reliability (PQR) throughout large regions. This paper describes a future possible structure for the electricity generation and delivery system that leaves the existing high voltage meshed grid paradigm in place, but involves radical reorganization of parts of the distribution network and customer sites. Managing a much more diverse dispersed system poses major challenges to the current centralized grid paradigm, particularly since many of these assets are small to tiny by macrogrid standards and they may ultimately number in the millions. They are also not ones that centralized control can rely upon to function in traditionally dependable ways, e.g. renewable generation can be highly variable and changes in output of generators are not independent. Although most involved in the industry agree that a paradigm shift is both necessary and desirable to manage the new system, the nature of the future system remains quite unclear. In the possible structure described here, the traditional grid, or macrogrid, remains similar at the high voltage meshed level. Three new entities are added more locally: community grids or milligrids that operate a segment of the existing distribution system, microgrids which are akin to current customer sites but which have automonous control, and nanogrids, such as telecom or Ethernet networks that currently distribute power to many low-power devices. The latter exist currently in the local electrical systems but are not typically considered a part of the traditional electricity supply system. Because all these new entities exhibit some localized control, providing appropriate local heterogeneous PQR becomes a possibility. These new grid concepts enable a more"bottom-up" approach to electricity distribution, in contrast to the historic 'top-down' model. The future will almost certainly include a mix of the two, but the balance among them and the interface (if any) between them is unclear.« less

Modeling and Grid Generation of Iced Airfoils

NASA Technical Reports Server (NTRS)

Vickerman, Mary B.; Baez, Marivell; Braun, Donald C.; Hackenberg, Anthony W.; Pennline, James A.; Schilling, Herbert W.

2007-01-01

SmaggIce Version 2.0 is a software toolkit for geometric modeling and grid generation for two-dimensional, singleand multi-element, clean and iced airfoils. A previous version of SmaggIce was described in Preparing and Analyzing Iced Airfoils, NASA Tech Briefs, Vol. 28, No. 8 (August 2004), page 32. To recapitulate: Ice shapes make it difficult to generate quality grids around airfoils, yet these grids are essential for predicting ice-induced complex flow. This software efficiently creates high-quality structured grids with tools that are uniquely tailored for various ice shapes. SmaggIce Version 2.0 significantly enhances the previous version primarily by adding the capability to generate grids for multi-element airfoils. This version of the software is an important step in streamlining the aeronautical analysis of ice airfoils using computational fluid dynamics (CFD) tools. The user may prepare the ice shape, define the flow domain, decompose it into blocks, generate grids, modify/divide/merge blocks, and control grid density and smoothness. All these steps may be performed efficiently even for the difficult glaze and rime ice shapes. Providing the means to generate highly controlled grids near rough ice, the software includes the creation of a wrap-around block (called the "viscous sublayer block"), which is a thin, C-type block around the wake line and iced airfoil. For multi-element airfoils, the software makes use of grids that wrap around and fill in the areas between the viscous sub-layer blocks for all elements that make up the airfoil. A scripting feature records the history of interactive steps, which can be edited and replayed later to produce other grids. Using this version of SmaggIce, ice shape handling and grid generation can become a practical engineering process, rather than a laborious research effort.

Information-theoretic characterization of dynamic energy systems

NASA Astrophysics Data System (ADS)

Bevis, Troy Lawson

The latter half of the 20th century saw tremendous growth in nearly every aspect of civilization. From the internet to transportation, the various infrastructures relied upon by society has become exponentially more complex. Energy systems are no exception, and today the power grid is one of the largest infrastructures in the history of the world. The growing infrastructure has led to an increase in not only the amount of energy produced, but also an increase in the expectations of the energy systems themselves. The need for a power grid that is reliable, secure, and efficient is apparent, and there have been several initiatives to provide such a system. These increases in expectations have led to a growth in the renewable energy sources that are being integrated into the grid, a change that increases efficiency and disperses the generation throughout the system. Although this change in the grid infrastructure is beneficial, it leads to grand challenges in system level control and operation. As the number of sources increases and becomes geographically distributed, the control systems are no longer local to the system. This means that communication networks must be enhanced to support multiple devices that must communicate reliably. A common solution to these new systems is to use wide area networks for the communication network, as opposed to point-to-point communication. Although the wide area network will support a large number of devices, it generally comes with a compromise in the form of latency in the communication system. Now the device controller has latency injected into the feedback loop of the system. Also, renewable energy sources are largely non-dispatchable generation. That is, they are never guaranteed to be online and supplying the demanded energy. As renewable generation is typically modeled as stochastic process, it would useful to include this behavior in the control system algorithms. The combination of communication latency and stochastic sources are compounded by the dynamics of the grid itself. Loads are constantly changing, as well as the sources; this can sometimes lead to a quick change in system states. There is a need for a metric to be able to take into consideration all of the factors detailed above; it needs to be able to take into consideration the amount of information that is available in the system and the rate that the information is losing its value. In a dynamic system, the information is only valid for a length of time, and the controller must be able to take into account the decay of currently held information. This thesis will present the information theory metrics in a way that is useful for application to dynamic energy systems. A test case involving synchronization of several generators is presented for analysis and application of the theory. The objective is to synchronize all the generators and connect them to a common bus. As the phase shift of each generator is a random process, the effects of latency and information decay can be directly observed. The results of the experiments clearly show that the expected outcomes are observed and that entropy and information theory is a valid metric for timing requirement extraction.

MSTB 2 x 6-Inch Low Speed Tunnel Turbulence Generator Grid/Honeycomb PIV Measurements and Analysis

NASA Technical Reports Server (NTRS)

Blackshire, James L.

1997-01-01

An assessment of the turbulence levels present in the Measurement Science and Technology (MSTB) branch's 2 x 6-inch low speed wind tunnel was made using Particle Image Velocimetry (PIV), and a turbulence generator consisting of a grid/honeycomb structure. Approximately 3000 digital PIV images were captured and analyzed covering an approximate 2 x 6-inch area along the centerline of the tunnel just beyond the turbulence generator system. Custom software for analysis and acquisition was developed for semi-automated digital PIV image acquisition and analysis. Comparisons between previously obtained LTA and LV turbulence measurements taken in the tunnel are presented.

Impact of grid size on uniform scanning and IMPT plans in XiO treatment planning system for brain cancer

PubMed Central

Zheng, Yuanshui

2015-01-01

The main purposes of this study are to: 1) evaluate the accuracy of XiO treatment planning system (TPS) for different dose calculation grid size based on head phantom measurements in uniform scanning proton therapy (USPT); and 2) compare the dosimetric results for various dose calculation grid sizes based on real computed tomography (CT) dataset of pediatric brain cancer treatment plans generated by USPT and intensity‐modulated proton therapy (IMPT) techniques. For phantom study, we have utilized the anthropomorphic head proton phantom provided by Imaging and Radiation Oncology Core (IROC). The imaging, treatment planning, and beam delivery were carried out following the guidelines provided by the IROC. The USPT proton plan was generated in the XiO TPS, and dose calculations were performed for grid size ranged from 1 to 3 mm. The phantom containing thermoluminescent dosimeter (TLDs) and films was irradiated using uniform scanning proton beam. The irradiated TLDs were read by the IROC. The calculated doses from the XiO for different grid sizes were compared to the measured TLD doses provided by the IROC. Gamma evaluation was done by comparing calculated planar dose distribution of 3 mm grid size with measured planar dose distribution. Additionally, IMPT plan was generated based on the same CT dataset of the IROC phantom, and IMPT dose calculations were performed for grid size ranged from 1 to 3 mm. For comparative purpose, additional gamma analysis was done by comparing the planar dose distributions of standard grid size (3 mm) with that of other grid sizes (1, 1.5, 2, and 2.5 mm) for both the USPT and IMPT plans. For patient study, USPT plans of three pediatric brain cancer cases were selected. IMPT plans were generated for each of three pediatric cases. All patient treatment plans (USPT and IMPT) were generated in the XiO TPS for a total dose of 54 Gy (relative biological effectiveness [RBE]). Treatment plans (USPT and IMPT) of each case was recalculated for grid sizes of 1, 1.5, 2, and 2.5 mm; these dosimetric results were then compared with that of 3 mm grid size. Phantom study results: There was no distinct trend exhibiting the dependence of grid size on dose calculation accuracy when calculated point dose of different grid sizes were compared to the measured point (TLD) doses. On average, the calculated point dose was higher than the measured dose by 1.49% and 2.63% for the right and left TLDs, respectively. The gamma analysis showed very minimal differences among planar dose distributions of various grid sizes, with percentage of points meeting gamma index criteria 1% and 1 mm to be from 97.92% to 99.97%. The gamma evaluation using 2% and 2 mm criteria showed both the IMPT and USPT plans have 100% points meeting the criteria. Patient study results: In USPT, there was no very distinct relationship between the absolute difference in mean planning target volume (PTV) dose and grid size, whereas in IMPT, it was found that the decrease in grid size slightly increased the PTV maximum dose and decreased the PTV mean dose and PTV D50%. For the PTV doses, the average differences were up to 0.35 Gy (RBE) and 1.47 Gy (RBE) in the USPT and IMPT plans, respectively. Dependency on grid size was not very clear for the organs at risk (OARs), with average difference ranged from −0.61 Gy (RBE) to 0.53 Gy (RBE) in the USPT plans and from −0.83 Gy (RBE) to 1.39 Gy (RBE) in the IMPT plans. In conclusion, the difference in the calculated point dose between the smallest grid size (1 mm) and the largest grid size (3 mm) in phantom for USPT was typically less than 0.1%. Patient study results showed that the decrease in grid size slightly increased the PTV maximum dose in both the USPT and IMPT plans. However, no distinct trend was obtained between the absolute difference in dosimetric parameter and dose calculation grid size for the OARs. Grid size has a large effect on dose calculation efficiency, and use of 2 mm or less grid size can increase the dose calculation time significantly. It is recommended to use grid size either 2.5 or 3 mm for dose calculations of pediatric brain cancer plans generated by USPT and IMPT techniques in XiO TPS. PACS numbers: 87.55.D‐, 87.55.ne, 87.55.dk PMID:26699310

Can developing countries leapfrog the centralized electrification paradigm?

DOE PAGES

Levin, Todd; Thomas, Valerie M.

2016-02-04

Due to the rapidly decreasing costs of small renewable electricity generation systems, centralized power systems are no longer a necessary condition of universal access to modern energy services. Developing countries, where centralized electricity infrastructures are less developed, may be able to adopt these new technologies more quickly. We first review the costs of grid extension and distributed solar home systems (SHSs) as reported by a number of different studies. We then present a general analytic framework for analyzing the choice between extending the grid and implementing distributed solar home systems. Drawing upon reported grid expansion cost data for three specificmore » regions, we demonstrate this framework by determining the electricity consumption levels at which the costs of provision through centralized and decentralized approaches are equivalent in these regions. We then calculate SHS capital costs that are necessary for these technologies provide each of five tiers of energy access, as defined by the United Nations Sustainable Energy for All initiative. Our results suggest that solar home systems can play an important role in achieving universal access to basic energy services. The extent of this role depends on three primary factors: SHS costs, grid expansion costs, and centralized generation costs. Given current technology costs, centralized systems will still be required to enable higher levels of consumption; however, cost reduction trends have the potential to disrupt this paradigm. Furthermore, by looking ahead rather than replicating older infrastructure styles, developing countries can leapfrog to a more distributed electricity service model.« less

Renewable Electricity Futures. Operational Analysis of the Western Interconnection at Very High Renewable Penetrations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brinkman, Gregory

2015-09-01

The Renewable Electricity Futures Study (RE Futures)--an analysis of the costs and grid impacts of integrating large amounts of renewable electricity generation into the U.S. power system--examined renewable energy resources, technical issues regarding the integration of these resources into the grid, and the costs associated with high renewable penetration scenarios. These scenarios included up to 90% of annual generation from renewable sources, although most of the analysis was focused on 80% penetration scenarios. Hourly production cost modeling was performed to understand the operational impacts of high penetrations. One of the conclusions of RE Futures was that further work was necessarymore » to understand whether the operation of the system was possible at sub-hourly time scales and during transient events. This study aimed to address part of this by modeling the operation of the power system at sub-hourly time scales using newer methodologies and updated data sets for transmission and generation infrastructure. The goal of this work was to perform a detailed, sub-hourly analysis of very high penetration scenarios for a single interconnection (the Western Interconnection). It focused on operational impacts, and it helps verify that the operational results from the capacity expansion models are useful. The primary conclusion of this study is that sub-hourly operation of the grid is possible with renewable generation levels between 80% and 90%.« less

High efficiency H6 single-phase transformerless grid-tied PV inverter with proposed modulation for reactive power generation

NASA Astrophysics Data System (ADS)

Almasoudi, Fahad M.; Alatawi, Khaled S.; Matin, Mohammad

2017-08-01

Implementation of transformerless inverters in PV grid-tied system offer great benefits such as high efficiency, light weight, low cost, etc. Most of the proposed transformerless inverters in literature are verified for only real power application. Currently, international standards such as VDE-AR-N 4105 has demanded that PV grid-tied inverters should have the ability of controlling a specific amount of reactive power. Generation of reactive power cannot be accomplished in single phase transformerless inverter topologies because the existing modulation techniques are not adopted for a freewheeling path in the negative power region. This paper enhances a previous high efficiency proposed H6 trnasformerless inverter with SiC MOSFETs and demonstrates new operating modes for the generation of reactive power. A proposed pulse width modulation (PWM) technique is applied to achieve bidirectional current flow through freewheeling state. A comparison of the proposed H6 transformerless inverter using SiC MOSFETs and Si MOSFTEs is presented in terms of power losses and efficiency. The results show that reactive power control is attained without adding any additional active devices or modification to the inverter structure. Also, the proposed modulation maintains a constant common mode voltage (CM) during every operating mode and has low leakage current. The performance of the proposed system verifies its effectiveness in the next generation PV system.

Control Strategies for Smoothing of Output Power of Wind Energy Conversion Systems

NASA Astrophysics Data System (ADS)

Pratap, Alok; Urasaki, Naomitsu; Senju, Tomonobu

2013-10-01

This article presents a control method for output power smoothing of a wind energy conversion system (WECS) with a permanent magnet synchronous generator (PMSG) using the inertia of wind turbine and the pitch control. The WECS used in this article adopts an AC-DC-AC converter system. The generator-side converter controls the torque of the PMSG, while the grid-side inverter controls the DC-link and grid voltages. For the generator-side converter, the torque command is determined by using the fuzzy logic. The inputs of the fuzzy logic are the operating point of the rotational speed of the PMSG and the difference between the wind turbine torque and the generator torque. By means of the proposed method, the generator torque is smoothed, and the kinetic energy stored by the inertia of the wind turbine can be utilized to smooth the output power fluctuations of the PMSG. In addition, the wind turbines shaft stress is mitigated compared to a conventional maximum power point tracking control. Effectiveness of the proposed method is verified by the numerical simulations.

Intelligent automated surface grid generation

NASA Technical Reports Server (NTRS)

Yao, Ke-Thia; Gelsey, Andrew

1995-01-01

The goal of our research is to produce a flexible, general grid generator for automated use by other programs, such as numerical optimizers. The current trend in the gridding field is toward interactive gridding. Interactive gridding more readily taps into the spatial reasoning abilities of the human user through the use of a graphical interface with a mouse. However, a sometimes fruitful approach to generating new designs is to apply an optimizer with shape modification operators to improve an initial design. In order for this approach to be useful, the optimizer must be able to automatically grid and evaluate the candidate designs. This paper describes and intelligent gridder that is capable of analyzing the topology of the spatial domain and predicting approximate physical behaviors based on the geometry of the spatial domain to automatically generate grids for computational fluid dynamics simulators. Typically gridding programs are given a partitioning of the spatial domain to assist the gridder. Our gridder is capable of performing this partitioning. This enables the gridder to automatically grid spatial domains of wide range of configurations.

Unstructured Grids for Sonic Boom Analysis and Design

NASA Technical Reports Server (NTRS)

Campbell, Richard L.; Nayani, Sudheer N.

2015-01-01

An evaluation of two methods for improving the process for generating unstructured CFD grids for sonic boom analysis and design has been conducted. The process involves two steps: the generation of an inner core grid using a conventional unstructured grid generator such as VGRID, followed by the extrusion of a sheared and stretched collar grid through the outer boundary of the core grid. The first method evaluated, known as COB, automatically creates a cylindrical outer boundary definition for use in VGRID that makes the extrusion process more robust. The second method, BG, generates the collar grid by extrusion in a very efficient manner. Parametric studies have been carried out and new options evaluated for each of these codes with the goal of establishing guidelines for best practices for maintaining boom signature accuracy with as small a grid as possible. In addition, a preliminary investigation examining the use of the CDISC design method for reducing sonic boom utilizing these grids was conducted, with initial results confirming the feasibility of a new remote design approach.

State reference design and saturated control of doubly-fed induction generators under voltage dips

NASA Astrophysics Data System (ADS)

Tilli, Andrea; Conficoni, Christian; Hashemi, Ahmad

2017-04-01

In this paper, the stator/rotor currents control problem of doubly-fed induction generator under faulty line voltage is carried out. Common grid faults cause a steep decline in the line voltage profile, commonly denoted as voltage dip. This point is critical for such kind of machines, having their stator windings directly connected to the grid. In this respect, solid methodological nonlinear control theory arguments are exploited and applied to design a novel controller, whose main goal is to improve the system behaviour during voltage dips, endowing it with low voltage ride through capability, a fundamental feature required by modern Grid Codes. The proposed solution exploits both feedforward and feedback actions. The feedforward part relies on suitable reference trajectories for the system internal dynamics, which are designed to prevent large oscillations in the rotor currents and command voltages, excited by line perturbations. The feedback part uses state measurements and is designed according to Linear Matrix Inequalities (LMI) based saturated control techniques to further reduce oscillations, while explicitly accounting for the system constraints. Numerical simulations verify the benefits of the internal dynamics trajectory planning, and the saturated state feedback action, in crucially improving the Doubly-Fed Induction Machine response under severe grid faults.

Deep Learning-Based Data Forgery Detection in Automatic Generation Control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fengli; Li, Qinghua

Automatic Generation Control (AGC) is a key control system in the power grid. It is used to calculate the Area Control Error (ACE) based on frequency and tie-line power flow between balancing areas, and then adjust power generation to maintain the power system frequency in an acceptable range. However, attackers might inject malicious frequency or tie-line power flow measurements to mislead AGC to do false generation correction which will harm the power grid operation. Such attacks are hard to be detected since they do not violate physical power system models. In this work, we propose algorithms based on Neural Networkmore » and Fourier Transform to detect data forgery attacks in AGC. Different from the few previous work that rely on accurate load prediction to detect data forgery, our solution only uses the ACE data already available in existing AGC systems. In particular, our solution learns the normal patterns of ACE time series and detects abnormal patterns caused by artificial attacks. Evaluations on the real ACE dataset show that our methods have high detection accuracy.« less

The value of residential photovoltaic systems: A comprehensive assessment

NASA Technical Reports Server (NTRS)

Borden, C. S.

1983-01-01

Utility-interactive photovoltaic (PV) arrays on residential rooftops appear to be a potentially attractive, large-scale application of PV technology. Results of a comprehensive assessment of the value (i.e., break-even cost) of utility-grid connected residential photovoltaic power systems under a variety of technological and economic assumptions are presented. A wide range of allowable PV system costs are calculated for small (4.34 kW (p) sub ac) residential PV systems in various locales across the United States. Primary factor in this variation are differences in local weather conditions, utility-specific electric generation capacity, fuel types, and customer-load profiles that effect purchase and sell-back rates, and non-uniform state tax considerations. Additional results from this analysis are: locations having the highest insolation values are not necessary the most economically attractive sites; residential PV systems connected in parallel to the utility demonstrate high percentages of energy sold back to the grid, and owner financial and tax assumptions cause large variations in break-even costs. Significant cost reduction and aggressive resolution of potential institutional impediments (e.g., liability, standards, metering, and technical integration) are required for a residential PV marker to become a major electric-grid-connected energy-generation source.

The value of residential photovoltaic systems: A comprehensive assessment

NASA Astrophysics Data System (ADS)

Borden, C. S.

1983-09-01

Utility-interactive photovoltaic (PV) arrays on residential rooftops appear to be a potentially attractive, large-scale application of PV technology. Results of a comprehensive assessment of the value (i.e., break-even cost) of utility-grid connected residential photovoltaic power systems under a variety of technological and economic assumptions are presented. A wide range of allowable PV system costs are calculated for small (4.34 kW (p) sub ac) residential PV systems in various locales across the United States. Primary factor in this variation are differences in local weather conditions, utility-specific electric generation capacity, fuel types, and customer-load profiles that effect purchase and sell-back rates, and non-uniform state tax considerations. Additional results from this analysis are: locations having the highest insolation values are not necessary the most economically attractive sites; residential PV systems connected in parallel to the utility demonstrate high percentages of energy sold back to the grid, and owner financial and tax assumptions cause large variations in break-even costs. Significant cost reduction and aggressive resolution of potential institutional impediments (e.g., liability, standards, metering, and technical integration) are required for a residential PV marker to become a major electric-grid-connected energy-generation source.

The data storage grid: the next generation of fault-tolerant storage for backup and disaster recovery of clinical images

NASA Astrophysics Data System (ADS)

King, Nelson E.; Liu, Brent; Zhou, Zheng; Documet, Jorge; Huang, H. K.

2005-04-01

Grid Computing represents the latest and most exciting technology to evolve from the familiar realm of parallel, peer-to-peer and client-server models that can address the problem of fault-tolerant storage for backup and recovery of clinical images. We have researched and developed a novel Data Grid testbed involving several federated PAC systems based on grid architecture. By integrating a grid computing architecture to the DICOM environment, a failed PACS archive can recover its image data from others in the federation in a timely and seamless fashion. The design reflects the five-layer architecture of grid computing: Fabric, Resource, Connectivity, Collective, and Application Layers. The testbed Data Grid architecture representing three federated PAC systems, the Fault-Tolerant PACS archive server at the Image Processing and Informatics Laboratory, Marina del Rey, the clinical PACS at Saint John's Health Center, Santa Monica, and the clinical PACS at the Healthcare Consultation Center II, USC Health Science Campus, will be presented. The successful demonstration of the Data Grid in the testbed will provide an understanding of the Data Grid concept in clinical image data backup as well as establishment of benchmarks for performance from future grid technology improvements and serve as a road map for expanded research into large enterprise and federation level data grids to guarantee 99.999 % up time.

PVUSA: The value of photovoltaics in the distribution system. The Kerman Grid-Support Project

NASA Astrophysics Data System (ADS)

Wenger, Howard J.; Hoff, Thomas E.

1995-05-01

As part of the Photovoltaics for Utility Scale Applications Applications (PVUSA) Project Pacific Gas Electric Company (PG&E) built the Kerman 500-kW photovoltaic power plant. Located near the end of a distribution feeder in a rural section of Fresno County, the plant was not built so much to demonstrate PV technology, but to evaluate its interaction with the local distribution grid and quantify available nontraditional grid-support benefits (those other than energy and capacity). As demand for new generation began to languish in the 1980s, and siting and permitting of power plants and transmission lines became more involved, utilities began considering smaller, distributed power sources. Potential benefits include shorter construction lead time, less capital outlay, and better utilization of existing assets. The results of a PG&E study in 1990/1991 of the benefits from a PV system to the distribution grid prompted the PVUSA Project to construct a plant at Kerman. Completed in 1993, the plant is believed to be the first one specifically built to evaluate the multiple benefits to the grid of a strategically sited plant. Each of nine discrete benefits were evaluated in detail by first establishing the technical impact, then translating the results into present economic value. Benefits span the entire system from distribution feeder to the generation fleet. This work breaks new ground in evaluation of distributed resources, and suggests that resource planning practices be expanded to account for these non-traditional benefits.

Novel Control Strategy for Multiple Run-of-the-River Hydro Power Plants to Provide Grid Ancillary Services

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohanpurkar, Manish; Luo, Yusheng; Hovsapian, Rob

Electricity generated by Hydropower Plants (HPPs) contributes a considerable portion of bulk electricity generation and delivers it with a low carbon footprint. In fact, HPP electricity generation provides the largest share from renewable energy resources, which includes solar and wind energy. The increasing penetration of wind and solar penetration leads to a lowered inertia in the grid and hence poses stability challenges. In recent years, breakthrough in energy storage technologies have demonstrated the economic and technical feasibility of extensive deployments in power grids. Multiple ROR HPPs if integrated with scalable, multi time-step energy storage so that the total output canmore » be controlled. Although, the size of a single energy storage is far smaller than that of a typical reservoir, cohesively managing multiple sets of energy storage distributed in different locations is proposed. The ratings of storages and multiple ROR HPPs approximately equals the rating of a large, conventional HPP. The challenges associated with the system architecture and operation are described. Energy storage technologies such as supercapacitors, flywheels, batteries etc. can function as a dispatchable synthetic reservoir with a scalable size of energy storage will be integrated. Supercapacitors, flywheels, and battery are chosen to provide fast, medium, and slow responses to support grid requirements. Various dynamic and transient power grid conditions are simulated and performances of integrated ROR HPPs with energy storage is provided. The end goal of this research is to investigate the inertial equivalence of a large, conventional HPP with a unique set of multiple ROR HPPs and optimally rated energy storage systems.« less

Inertial Response of an Offshore Wind Power Plant with HVDC-VSC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Preciado, V.; Gevorgian, Vahan; Muljadi, Eduard

This paper analyzes the inertial response of an offshore wind power plant (WPP) to provide ancillary services to the power system grid. The WPP is connected to a high-voltage direct-current voltage source converter HVDC-VSC to deliver the power to the onshore substation. The wind turbine generator (WTG) used is a doubly-fed induction generator (Type 3 WTG). In this paper we analyze a control method for the WTGs in an offshore WPP to support the grid and contribute ancillary services to the power system network. Detailed time domain simulations will be conducted to show the transient behavior of the inertial responsemore » of an offshore WPP.« less

Renewable Electricity Futures Study Executive Summary

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mai, Trieu; Sandor, Debra; Wiser, Ryan

2012-12-01

The Renewable Electricity Futures Study (RE Futures) provides an analysis of the grid integration opportunities, challenges, and implications of high levels of renewable electricity generation for the U.S. electric system. The study is not a market or policy assessment. Rather, RE Futures examines renewable energy resources and many technical issues related to the operability of the U.S. electricity grid, and provides initial answers to important questions about the integration of high penetrations of renewable electricity technologies from a national perspective. RE Futures results indicate that a future U.S. electricity system that is largely powered by renewable sources is possible andmore » that further work is warranted to investigate this clean generation pathway.« less

Isolated Operation at Hachinohe Micro-Grid Project

NASA Astrophysics Data System (ADS)

Takano, Tomihiro; Kojima, Yasuhiro; Temma, Koji; Simomura, Masaru

To meet the global warming, renewable energy sources like wind, solar and biomass generations are dramatically increasing. Cogeneration systems are also ever-growing to save consumers' energy costs among factories, buildings and homes where lots of thermal loads are expected. According to these dispersed generators growth, their negative impacts to commercial power systems quality become non-negligible, because their unstable output causes network voltage and frequency fluctuation. Micro-grid technology comes to the front to solve the problem and many demonstrative field tests are now going all over the world. This paper presents the control paradigm and its application to Hachinohe micro-gird project, especially focusing on the power quality at isolated operation on which strict condition is imposed.

Research on unit commitment with large-scale wind power connected power system

NASA Astrophysics Data System (ADS)

Jiao, Ran; Zhang, Baoqun; Chi, Zhongjun; Gong, Cheng; Ma, Longfei; Yang, Bing

2017-01-01

Large-scale integration of wind power generators into power grid brings severe challenges to power system economic dispatch due to its stochastic volatility. Unit commitment including wind farm is analyzed from the two parts of modeling and solving methods. The structures and characteristics can be summarized after classification has been done according to different objective function and constraints. Finally, the issues to be solved and possible directions of research and development in the future are discussed, which can adapt to the requirements of the electricity market, energy-saving power generation dispatching and smart grid, even providing reference for research and practice of researchers and workers in this field.

Grid point extraction and coding for structured light system

NASA Astrophysics Data System (ADS)

Song, Zhan; Chung, Ronald

2011-09-01

A structured light system simplifies three-dimensional reconstruction by illuminating a specially designed pattern to the target object, thereby generating a distinct texture on it for imaging and further processing. Success of the system hinges upon what features are to be coded in the projected pattern, extracted in the captured image, and matched between the projector's display panel and the camera's image plane. The codes have to be such that they are largely preserved in the image data upon illumination from the projector, reflection from the target object, and projective distortion in the imaging process. The features also need to be reliably extracted in the image domain. In this article, a two-dimensional pseudorandom pattern consisting of rhombic color elements is proposed, and the grid points between the pattern elements are chosen as the feature points. We describe how a type classification of the grid points plus the pseudorandomness of the projected pattern can equip each grid point with a unique label that is preserved in the captured image. We also present a grid point detector that extracts the grid points without the need of segmenting the pattern elements, and that localizes the grid points in subpixel accuracy. Extensive experiments are presented to illustrate that, with the proposed pattern feature definition and feature detector, more features points in higher accuracy can be reconstructed in comparison with the existing pseudorandomly encoded structured light systems.

A two-dimensional composite grid numerical model based on the reduced system for oceanography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Y.F.; Browning, G.L.; Chesshire, G.

The proper mathematical limit of a hyperbolic system with multiple time scales, the reduced system, is a system that contains no high-frequency motions and is well posed if suitable boundary conditions are chosen for the initial-boundary value problem. The composite grid method, a robust and efficient grid-generation technique that smoothly and accurately treats general irregular boundaries, is used to approximate the two-dimensional version of the reduced system for oceanography on irregular ocean basins. A change-of-variable technique that substantially increases the accuracy of the model and a method for efficiently solving the elliptic equation for the geopotential are discussed. Numerical resultsmore » are presented for circular and kidney-shaped basins by using a set of analytic solutions constructed in this paper.« less

Space-time modeling using environmental constraints in a mobile robot system

NASA Technical Reports Server (NTRS)

Slack, Marc G.

1990-01-01

Grid-based models of a robot's local environment have been used by many researchers building mobile robot control systems. The attraction of grid-based models is their clear parallel between the internal model and the external world. However, the discrete nature of such representations does not match well with the continuous nature of actions and usually serves to limit the abilities of the robot. This work describes a spatial modeling system that extracts information from a grid-based representation to form a symbolic representation of the robot's local environment. The approach makes a separation between the representation provided by the sensing system and the representation used by the action system. Separation allows asynchronous operation between sensing and action in a mobile robot, as well as the generation of a more continuous representation upon which to base actions.

Emissions & Generation Resource Integrated Database (eGRID), eGRID2010

EPA Pesticide Factsheets

The Emissions & Generation Resource Integrated Database (eGRID) is a comprehensive source of data on the environmental characteristics of almost all electric power generated in the United States. These environmental characteristics include air emissions for nitrogen oxides, sulfur dioxide, carbon dioxide, methane, and nitrous oxide; emissions rates; net generation; resource mix; and many other attributes.eGRID2010 contains the complete release of year 2007 data, as well as years 2005 and 2004 data. Excel spreadsheets, full documentation, summary data, eGRID subregion and NERC region representational maps, and GHG emission factors are included in this data set. The Archived data in eGRID2002 contain years 1996 through 2000 data.For year 2007 data, the first Microsoft Excel workbook, Plant, contains boiler, generator, and plant spreadsheets. The second Microsoft Excel workbook, Aggregation, contains aggregated data by state, electric generating company, parent company, power control area, eGRID subregion, NERC region, and U.S. total levels. The third Microsoft Excel workbook, ImportExport, contains state import-export data, as well as U.S. generation and consumption data for years 2007, 2005, and 2004. For eGRID data for years 2005 and 2004, a user friendly web application, eGRIDweb, is available to select, view, print, and export specified data.

Generation of three-dimensional body-fitted coordinates using hyperbolic partial differential equations

NASA Technical Reports Server (NTRS)

Steger, J. L.; Rizk, Y. M.

1985-01-01

An efficient numerical mesh generation scheme capable of creating orthogonal or nearly orthogonal grids about moderately complex three dimensional configurations is described. The mesh is obtained by marching outward from a user specified grid on the body surface. Using spherical grid topology, grids have been generated about full span rectangular wings and a simplified space shuttle orbiter.

Interaction of side-by-side fluidic harvesters in fractal grid-generated turbulence

NASA Astrophysics Data System (ADS)

Ferko, Kevin; Lachendro, David; Chiappazzi, Nick; Danesh-Yazdi, Amir H.

2018-03-01

While the vast majority of the literature in energy harvesting is dedicated to resonant harvesters, non-resonant harvesters, especially those that use turbulence-induced vibration to generate energy, have not been studied in as much detail. This is especially true for grid-generated turbulence. In this paper, the interaction of two side-by-side fluidic harvesters from a passive fractal grid-generated turbulent flow is considered. The fractal grid has been shown to significantly increase the turbulence generated in the flow which is the source of the vibration of the piezoelectric beams. In this experimental study, the influence of four parameters has been investigated: Beam lengths and configurations, mean flow velocity, distance from the grid and gap between the two beams. Experimental results show that the piezoelectric harvesters in fractal grid turbulence are capable of producing at least the same amount of power as those placed in passive rectangular grids with a larger pressure loss, allowing for a potentially significant increase in the efficiency of the energy conversion process, even though more experiments are required to study the behavior of the beams in homogeneous, fractal grid-generated turbulence.

Investigation of Advanced Counterrotation Blade Configuration Concepts for High Speed Turboprop Systems. Task 2: Unsteady Ducted Propfan Analysis

NASA Technical Reports Server (NTRS)

Hall, Edward J.; Delaney, Robert A.; Bettner, James L.

1991-01-01

The primary objective was the development of a time dependent 3-D Euler/Navier-Stokes aerodynamic analysis to predict unsteady compressible transonic flows about ducted and unducted propfan propulsion systems at angle of attack. The resulting computer codes are referred to as Advanced Ducted Propfan Analysis Codes (ADPAC). A computer program user's manual is presented for the ADPAC. Aerodynamic calculations were based on a four stage Runge-Kutta time marching finite volume solution technique with added numerical dissipation. A time accurate implicit residual smoothing operator was used for unsteady flow predictions. For unducted propfans, a single H-type grid was used to discretize each blade passage of the complete propeller. For ducted propfans, a coupled system of five grid blocks utilizing an embedded C grid about the cowl leading edge was used to discretize each blade passage. Grid systems were generated by a combined algebraic/elliptic algorithm developed specifically for ducted propfans. Numerical calculations were compared with experimental data for both ducted and unducted flows.

DOE Office of Scientific and Technical Information (OSTI.GOV)

TESP combines existing domain simulators in the electric power grid, with new transactive agents, growth models and evaluation scripts. The existing domain simulators include GridLAB-D for the distribution grid and single-family residential buildings, MATPOWER for transmission and bulk generation, and EnergyPlus for large buildings. More are planned for subsequent versions of TESP. The new elements are: TEAgents - simulate market participants and transactive systems for market clearing. Some of this functionality was extracted from GridLAB-D and implemented in Python for customization by PNNL and others; Growth Model - a means for simulating system changes over a multiyear period, including bothmore » normal load growth and specific investment decisions. Customizable in Python code; and Evaluation Script - a means of evaluating different transactive systems through customizable post-processing in Python code. TESP provides a method for other researchers and vendors to design transactive systems, and test them in a virtual environment. It allows customization of the key components by modifying Python code.« less

Design of A Grid Integrated PV System with MPPT Control and Voltage Oriented Controller using MATLAB/PLECES

NASA Astrophysics Data System (ADS)

Soreng, Bineeta; Behera, Pradyumna; Pradhan, Raseswari

2017-08-01

This paper presents model of a grid-integrated photovoltaic array with Maximum Power Point Tracker (MPPT) and voltage oriented controller. The MPPT of the PV array is usually an essential part of PV system as MPPT helps the operating point of the solar array to align its maximum power point. In this model, the MPPT along with a DC-DC converter lets a PV generator to produce continuous power, despite of the measurement conditions. The neutral-point-clamped converter (NPC) with a boost converter raises the voltage from the panels to the DC-link. An LCL-filter smoothens the current ripple caused by the PWM modulation of the grid-side inverter. In addition to the MPPT, the system has two more two controllers, such as voltage controller and a current controller. The voltage control has a PI controller to regulate the PV voltage to optimal level by controlling the amount of current injected into the boost stage. Here, the grid-side converter transfers the power from the DC-link into the grid and maintains the DC-link voltage. Three-phase PV inverters are used for off-grid or designed to create utility frequency AC. The PV system can be connected in series or parallel to get the desired output power. To justify the working of this model, the grid-integrated PV system has been designed in MATLAB/PLECS. The simulation shows the P-V curve of implemented PV Array consisting 4 X 20 modules, reactive, real power, grid voltage and current.

Interfacing a small thermophotovoltaic generator to the grid

NASA Astrophysics Data System (ADS)

Durisch, W.; Grob, B.; Mayor, J.-C.; Panitz, J.-C.; Rosselet, A.

1999-03-01

A prototype thermophotovoltaic generator and grid-interfacing device have been developed to demonstrate the feasibility of grid-connected operation. For this purpose a conventional butane burner (rated power 1.35 kWth) was equipped with a ceramic composite emitter made of rare earth oxides. A water layer between emitter and photocells was used to protect the photocells against overheating. It absorbs the nonconvertible emitter radiation and is heated up thereby. The hot water so produced in larger units of this type could be used in a primary recirculation loop to transfer heat to a secondary domestic hot water system. For the photovoltaic generator, commercial grade silicon solar cells with 16% efficiency (under standard test conditions) were used. With the radiation of the emitter, a current of 4.6 A at a maximum power point voltage of 3.3 V was produced, corresponding to a DC output of 15 W and a thermal to DC power conversion efficiency of 1.1%. A specially developed high efficiency DC/DC converter and a modified, commercially available inverter were used to feed the generated power to the local grid. Under the experimental conditions in question the DC/DC-converter and the grid-inverter had efficiencies of 98 and 91%, respectively resulting in an overall interface efficiency of 89%. From modeling of the measured electrical characteristics of the photo cell generator under solar and emitter radiation, it is concluded that the photo current was about three times higher under the filtered emitter radiation. Under these conditions the electrical losses of the photocells were significantly higher than under sunlight.

Opportunities for Joint Water–Energy Management: Sensitivity of the 2010 Western U.S. Electricity Grid Operations to Climate Oscillations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voisin, N.; Kintner-Meyer, M.; Wu, D.

The 2016 SECURE Water Act report’s natural water availability benchmark, combined with the 2010 level of water demand from an integrated assessment model, is used as input to drive a large-scale water management model. The regulated flow at hydropower plants and thermoelectric plants in the Western U.S. electricity grid (WECC) is translated into potential hydropower generation and generation capacity constraints. The impact on reliability (unserved energy, reserve margin) and cost (production cost, carbon emissions) of water constraints on 2010-level WECC power system operations is assessed using an electricity production cost model (PCM). Use of the PCM reveals the changes inmore » generation dispatch that reflect the inter-regional interdependencies in water-constrained generation and the ability to use other generation resources to meet all electricity loads in the WECC. August grid operational benchmarks show a range of sensitivity in production cost (-8 to +11%) and carbon emissions (-7 to 11%). The reference reserve margin threshold of 15% above peak load is maintained in the scenarios analyzed, but in 5 out of 55 years unserved energy is observed when normal operations are maintained. There is 1 chance in 10 that a year will demonstrate unserved energy in August, which defines the system’s historical performance threshold to support impact, vulnerability, and adaptation analysis. For seasonal and longer term planning, i.e., multi-year drought, we demonstrate how the Water Scarcity Grid Impact Factor and climate oscillations (ENSO, PDO) can be used to plan for joint water-electricity management to maintain grid reliability.« less

Design and Implementation of Real-Time Off-Grid Detection Tool Based on FNET/GridEye

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Jiahui; Zhang, Ye; Liu, Yilu

2014-01-01

Real-time situational awareness tools are of critical importance to power system operators, especially during emergencies. The availability of electric power has become a linchpin of most post disaster response efforts as it is the primary dependency for public and private sector services, as well as individuals. Knowledge of the scope and extent of facilities impacted, as well as the duration of their dependence on backup power, enables emergency response officials to plan for contingencies and provide better overall response. Based on real-time data acquired by Frequency Disturbance Recorders (FDRs) deployed in the North American power grid, a real-time detection methodmore » is proposed. This method monitors critical electrical loads and detects the transition of these loads from an on-grid state, where the loads are fed by the power grid to an off-grid state, where the loads are fed by an Uninterrupted Power Supply (UPS) or a backup generation system. The details of the proposed detection algorithm are presented, and some case studies and off-grid detection scenarios are also provided to verify the effectiveness and robustness. Meanwhile, the algorithm has already been implemented based on the Grid Solutions Framework (GSF) and has effectively detected several off-grid situations.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lawrence, Thomas M.; Boudreau, Marie-Claude; Helsen, Lieve

Recent advances in information and communications technology (ICT) have initiated development of a smart electrical grid and smart buildings. Buildings consume a large portion of the total electricity production worldwide, and to fully develop a smart grid they must be integrated with that grid. Buildings can now be 'prosumers' on the grid (both producers and consumers), and the continued growth of distributed renewable energy generation is raising new challenges in terms of grid stability over various time scales. Buildings can contribute to grid stability by managing their overall electrical demand in response to current conditions. Facility managers must balance demandmore » response requests by grid operators with energy needed to maintain smooth building operations. For example, maintaining thermal comfort within an occupied building requires energy and, thus an optimized solution balancing energy use with indoor environmental quality (adequate thermal comfort, lighting, etc.) is needed. Successful integration of buildings and their systems with the grid also requires interoperable data exchange. However, the adoption and integration of newer control and communication technologies into buildings can be problematic with older legacy HVAC and building control systems. Public policy and economic structures have not kept up with the technical developments that have given rise to the budding smart grid, and further developments are needed in both technical and non-technical areas.« less

Elliptic generation of composite three-dimensional grids about realistic aircraft

NASA Technical Reports Server (NTRS)

Sorenson, R. L.

1986-01-01

An elliptic method for generating composite grids about realistic aircraft is presented. A body-conforming grid is first generated about the entire aircraft by the solution of Poisson's differential equation. This grid has relatively coarse spacing, and it covers the entire physical domain. At boundary surfaces, cell size is controlled and cell skewness is nearly eliminated by inhomogeneous terms, which are found automatically by the program. Certain regions of the grid in which high gradients are expected, and which map into rectangular solids in the computational domain, are then designated for zonal refinement. Spacing in the zonal grids is reduced by adding points with a simple, algebraic scheme. Details of the grid generation method are presented along with results of the present application, a wing-body configuration based on the F-16 fighter aircraft.

Adaptively-refined overlapping grids for the numerical solution of systems of hyperbolic conservation laws

NASA Technical Reports Server (NTRS)

Brislawn, Kristi D.; Brown, David L.; Chesshire, Geoffrey S.; Saltzman, Jeffrey S.

1995-01-01

Adaptive mesh refinement (AMR) in conjunction with higher-order upwind finite-difference methods have been used effectively on a variety of problems in two and three dimensions. In this paper we introduce an approach for resolving problems that involve complex geometries in which resolution of boundary geometry is important. The complex geometry is represented by using the method of overlapping grids, while local resolution is obtained by refining each component grid with the AMR algorithm, appropriately generalized for this situation. The CMPGRD algorithm introduced by Chesshire and Henshaw is used to automatically generate the overlapping grid structure for the underlying mesh.

RETHINKING THE FUTURE GRID: INTEGRATED NUCLEAR-RENEWABLE ENERGY SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

S.M. Bragg-Sitton; R. Boardman

2014-12-01

The 2013 electricity generation mix in the United States consisted of ~13% renewables (hydropower, wind, solar, geothermal), 19% nuclear, 27% natural gas, and 39% coal. In the 2011 State of the Union Address, President Obama set a clean energy goal for the nation: “By 2035, 80 percent of America’s electricity will come from clean energy sources. Some folks want wind and solar. Others want nuclear, clean coal and natural gas. To meet this goal we will need them all.” The U.S. Department of Energy (DOE) Offices of Nuclear Energy (NE) and Energy Efficiency and Renewable Energy (EERE) recognize that “allmore » of the above” means that we are called to best utilize all available clean energy sources. To meet the stated environmental goals for electricity generation and for the broader energy sector, there is a need to transform the energy infrastructure of the U.S. and elsewhere. New energy systems must be capable of significantly reducing environmental impacts in an efficient and economically viable manner while utilizing both hydrocarbon resources and clean energy generation sources. The U.S. DOE is supporting research and development that could lead to more efficient utilization of clean energy generation sources, including renewable and nuclear options, to meet both grid demand and thermal energy needs in the industrial sector. A concept being advanced by the DOE-NE and DOE-EERE is tighter coupling of nuclear and renewable energy sources in a manner that better optimizes energy use for the combined electricity, industrial manufacturing, and the transportation sectors. This integration concept has been referred to as a “hybrid system” that is capable of apportioning thermal and electrical energy to first meet the grid demand (with appropriate power conversion systems), then utilizing excess thermal and, in some cases, electrical energy to drive a process that results in an additional product. For the purposes of the present work, the hybrid system would integrate two or more energy resources to generate two or more products, one of which must be an energy commodity, such as electricity or transportation fuel. Subsystems would be integrated ‘‘behind’’ the electrical transmission bus and would be comprised of two or more energy conversion subsystems that have traditionally been separate or isolated. Energy flows would be dynamically apportioned as necessary to meet grid demand via a single, highly responsive connection to the grid that provides dispatchable electricity while capital-intensive generation assets operate at full capacity. Candidate region-specific hybrid energy systems selected for further study and figures of merit that will be used to assess system performance will be presented.« less

Greening the Grid: Advances in Production Cost Modeling for India Renewable Energy Grid Integration Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cochran, Jaquelin; Palchak, David

The Greening the Grid: Pathways to Integrate 175 Gigawatts of Renewable Energy into India's Electric Grid study uses advanced weather and power system modeling to explore the operational impacts of meeting India's 2022 renewable energy targets and identify actions that may be favorable for integrating high levels of renewable energy into the Indian grid. The study relies primarily on a production cost model that simulates optimal scheduling and dispatch of available generation in a future year (2022) by minimizing total production costs subject to physical, operational, and market constraints. This fact sheet provides a detailed look at each of thesemore » models, including their common assumptions and the insights provided by each.« less

System-of-Systems Approach for Integrated Energy Systems Modeling and Simulation: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mittal, Saurabh; Ruth, Mark; Pratt, Annabelle

Today’s electricity grid is the most complex system ever built—and the future grid is likely to be even more complex because it will incorporate distributed energy resources (DERs) such as wind, solar, and various other sources of generation and energy storage. The complexity is further augmented by the possible evolution to new retail market structures that provide incentives to owners of DERs to support the grid. To understand and test new retail market structures and technologies such as DERs, demand-response equipment, and energy management systems while providing reliable electricity to all customers, an Integrated Energy System Model (IESM) is beingmore » developed at NREL. The IESM is composed of a power flow simulator (GridLAB-D), home energy management systems implemented using GAMS/Pyomo, a market layer, and hardware-in-the-loop simulation (testing appliances such as HVAC, dishwasher, etc.). The IESM is a system-of-systems (SoS) simulator wherein the constituent systems are brought together in a virtual testbed. We will describe an SoS approach for developing a distributed simulation environment. We will elaborate on the methodology and the control mechanisms used in the co-simulation illustrated by a case study.« less

Analytical Assessment of the Relationship between 100MWp Large-scale Grid-connected Photovoltaic Plant Performance and Meteorological Parameters

NASA Astrophysics Data System (ADS)

Sheng, Jie; Zhu, Qiaoming; Cao, Shijie; You, Yang

2017-05-01

This paper helps in study of the relationship between the photovoltaic power generation of large scale “fishing and PV complementary” grid-tied photovoltaic system and meteorological parameters, with multi-time scale power data from the photovoltaic power station and meteorological data over the same period of a whole year. The result indicates that, the PV power generation has the most significant correlation with global solar irradiation, followed by diurnal temperature range, sunshine hours, daily maximum temperature and daily average temperature. In different months, the maximum monthly average power generation appears in August, which related to the more global solar irradiation and longer sunshine hours in this month. However, the maximum daily average power generation appears in October, this is due to the drop in temperature brings about the improvement of the efficiency of PV panels. Through the contrast of monthly average performance ratio (PR) and monthly average temperature, it is shown that, the larger values of monthly average PR appears in April and October, while it is smaller in summer with higher temperature. The results concluded that temperature has a great influence on the performance ratio of large scale grid-tied PV power system, and it is important to adopt effective measures to decrease the temperature of PV plant properly.

Life Prediction Model for Grid-Connected Li-ion Battery Energy Storage System: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Kandler A; Saxon, Aron R; Keyser, Matthew A

Life Prediction Model for Grid-Connected Li-ion Battery Energy Storage System: Preprint Lithium-ion (Li-ion) batteries are being deployed on the electrical grid for a variety of purposes, such as to smooth fluctuations in solar renewable power generation. The lifetime of these batteries will vary depending on their thermal environment and how they are charged and discharged. To optimal utilization of a battery over its lifetime requires characterization of its performance degradation under different storage and cycling conditions. Aging tests were conducted on commercial graphite/nickel-manganese-cobalt (NMC) Li-ion cells. A general lifetime prognostic model framework is applied to model changes in capacity andmore » resistance as the battery degrades. Across 9 aging test conditions from 0oC to 55oC, the model predicts capacity fade with 1.4 percent RMS error and resistance growth with 15 percent RMS error. The model, recast in state variable form with 8 states representing separate fade mechanisms, is used to extrapolate lifetime for example applications of the energy storage system integrated with renewable photovoltaic (PV) power generation.« less

Improved direct torque control of an induction generator used in a wind conversion system connected to the grid.

PubMed

Abdelli, Radia; Rekioua, Djamila; Rekioua, Toufik; Tounzi, Abdelmounaïm

2013-07-01

This paper presents a modulated hysteresis direct torque control (MHDTC) applied to an induction generator (IG) used in wind energy conversion systems (WECs) connected to the electrical grid through a back-to-back converter. The principle of this strategy consists in superposing to the torque reference a triangular signal, as in the PWM strategy, with the desired switching frequency. This new modulated reference is compared to the estimated torque by using a hysteresis controller as in the classical direct torque control (DTC). The aim of this new approach is to lead to a constant frequency and low THD in grid current with a unit power factor and a minimum voltage variation despite the wind variation. To highlight the effectiveness of the proposed method, a comparison was made with classical DTC and field oriented control method (FOC). The obtained simulation results, with a variable wind profile, show an adequate dynamic of the conversion system using the proposed method compared to the classical approaches. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

NREL Manages Program to Transform Mexico's Power Sector | Integrated Energy

Science.gov Websites

. Through 21CPP, NREL is helping Mexico with: Long-range planning of the power system for transmission , generation, and integration of renewable energy How best to operate the electric grid as Mexico increases the deep energy efficiency and smart grid solutions. Impact Mexico is on the brink of a major energy reform

Grid Integrated Type 3 Wind Systems - Modeling, and Line Protection Performance Analysis using the RTDS

NASA Astrophysics Data System (ADS)

Jain, Rishabh

In this thesis, the line protection elements and their supervisory elements are analyzed in context of Type 3 (Doubly Fed Induction Generator based) grid integrated wind turbine systems. The underlying converter and controller design algorithms and topologies are discussed. A detailed controller for the Type 3 wind turbine system is designed and integrated to the grid using the RTDS. An alternative to the conventional PLL for tracking of rotor frequency is designed and implemented. A comparative analysis of the performance of an averaged model and the corresponding switching model is presented. After completing the WT model design, the averaged model is used to model an aggregate 10-generator equivalent model tied to a 230kV grid via a 22kV collector. This model is a great asset to understand dynamics, and the unfaulted and faulted behavior of aggregated and single-turbine Type 3 WT systems. The model is then utilized to analyze the response of conventional protection schemes (Line current Differential and Mho Distance elements) and their respective supervisory elements of modern commercial protection relays in real time by hardware-in-the-loop simulation using the RTDS. Differences in the behavior of these elements compared to conventional power systems is noted. Fault are analyzed from the relay's perspective and the reasons for the observed behavior are presented. Challenges associated with sequence components and relay sensitivity are discussed and alternate practices to circumvent these issues are recommended.

High flexible Hydropower Generation concepts for future grids

NASA Astrophysics Data System (ADS)

Hell, Johann

2017-04-01

The ongoing changes in electric power generation are resulting in new requirements for the classical generating units. In consequence a paradigm change in operation of power systems is necessary and a new approach in finding solutions is needed. The presented paper is dealing with the new requirements on current and future energy systems with the focus on hydro power generation. A power generation landscape for some European regions is shown and generation and operational flexibility is explained. Based on the requirements from the Transmission System Operator in UK, the transient performance of a Pumped Storage installation is discussed.

Non-Pilot Protection of the HVDC Grid

NASA Astrophysics Data System (ADS)

Badrkhani Ajaei, Firouz

This thesis develops a non-pilot protection system for the next generation power transmission system, the High-Voltage Direct Current (HVDC) grid. The HVDC grid protection system is required to be (i) adequately fast to prevent damages and/or converter blocking and (ii) reliable to minimize the impacts of faults. This study is mainly focused on the Modular Multilevel Converter (MMC) -based HVDC grid since the MMC is considered as the building block of the future HVDC systems. The studies reported in this thesis include (i) developing an enhanced equivalent model of the MMC to enable accurate representation of its DC-side fault response, (ii) developing a realistic HVDC-AC test system that includes a five-terminal MMC-based HVDC grid embedded in a large interconnected AC network, (iii) investigating the transient response of the developed test system to AC-side and DC-side disturbances in order to determine the HVDC grid protection requirements, (iv) investigating the fault surge propagation in the HVDC grid to determine the impacts of the DC-side fault location on the measured signals at each relay location, (v) designing a protection algorithm that detects and locates DC-side faults reliably and sufficiently fast to prevent relay malfunction and unnecessary blocking of the converters, and (vi) performing hardware-in-the-loop tests on the designed relay to verify its potential to be implemented in hardware. The results of the off-line time domain transients studies in the PSCAD software platform and the real-time hardware-in-the-loop tests using an enhanced version of the RTDS platform indicate that the developed HVDC grid relay meets all technical requirements including speed, dependability, security, selectivity, and robustness. Moreover, the developed protection algorithm does not impose considerable computational burden on the hardware.

Emissions & Generation Resource Integrated Database (eGRID) Questions and Answers

EPA Pesticide Factsheets

eGRID is a comprehensive source of data on the environmental characteristics of almost all electric power generated in the United States. eGRID is based on available plant-specific data for all U.S. electricity generating plants that report data.

Advanced Unstructured Grid Generation for Complex Aerodynamic Applications

NASA Technical Reports Server (NTRS)

Pirzadeh, Shahyar Z.

2008-01-01

A new approach for distribution of grid points on the surface and in the volume has been developed and implemented in the NASA unstructured grid generation code VGRID. In addition to the point and line sources of prior work, the new approach utilizes surface and volume sources for automatic curvature-based grid sizing and convenient point distribution in the volume. A new exponential growth function produces smoother and more efficient grids and provides superior control over distribution of grid points in the field. All types of sources support anisotropic grid stretching which not only improves the grid economy but also provides more accurate solutions for certain aerodynamic applications. The new approach does not require a three-dimensional background grid as in the previous methods. Instead, it makes use of an efficient bounding-box auxiliary medium for storing grid parameters defined by surface sources. The new approach is less memory-intensive and more efficient computationally. The grids generated with the new method either eliminate the need for adaptive grid refinement for certain class of problems or provide high quality initial grids that would enhance the performance of many adaptation methods.

Application of the FUN3D Unstructured-Grid Navier-Stokes Solver to the 4th AIAA Drag Prediction Workshop Cases

NASA Technical Reports Server (NTRS)

Lee-Rausch, Elizabeth M.; Hammond, Dana P.; Nielsen, Eric J.; Pirzadeh, S. Z.; Rumsey, Christopher L.

2010-01-01

FUN3D Navier-Stokes solutions were computed for the 4th AIAA Drag Prediction Workshop grid convergence study, downwash study, and Reynolds number study on a set of node-based mixed-element grids. All of the baseline tetrahedral grids were generated with the VGRID (developmental) advancing-layer and advancing-front grid generation software package following the gridding guidelines developed for the workshop. With maximum grid sizes exceeding 100 million nodes, the grid convergence study was particularly challenging for the node-based unstructured grid generators and flow solvers. At the time of the workshop, the super-fine grid with 105 million nodes and 600 million elements was the largest grid known to have been generated using VGRID. FUN3D Version 11.0 has a completely new pre- and post-processing paradigm that has been incorporated directly into the solver and functions entirely in a parallel, distributed memory environment. This feature allowed for practical pre-processing and solution times on the largest unstructured-grid size requested for the workshop. For the constant-lift grid convergence case, the convergence of total drag is approximately second-order on the finest three grids. The variation in total drag between the finest two grids is only 2 counts. At the finest grid levels, only small variations in wing and tail pressure distributions are seen with grid refinement. Similarly, a small wing side-of-body separation also shows little variation at the finest grid levels. Overall, the FUN3D results compare well with the structured-grid code CFL3D. The FUN3D downwash study and Reynolds number study results compare well with the range of results shown in the workshop presentations.

The development and performance of smud grid-connected photovoltaic projects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osborn, D.E.; Collier, D.E.

1995-11-01

The utility grid-connected market has been identified as a key market to be developed to accelerate the commercialization of photovoltaics. The Sacramento Municipal Utility District (SMUD) has completed the first two years of a continuing commercialization effort based on two years of a continuing commercialization effort based on the sustained, orderly development of the grid-connected, utility PV market. This program is aimed at developing the experience needed to successfully integrate PV as distributed generation into the utility system and to stimulate the collaborative processes needed to accelerate the cost reductions necessary for PV to be cost-effective in these applications bymore » the year 2000. In the first two years, SMUD has installed over 240 residential and commercial building, grid-connected, rooftop, {open_quotes}PV Pioneer{close_quotes} systems totaling over 1MW of capacity and four substation sited, grid-support PV systems totaling 600 kW bringing the SMUD distributed PV power systems to over 3.7 MW. The 1995 SMUD PV Program will add another approximately 800 kW of PV systems to the District`s distributed PV power system. SMUD also established a partnership with its customers through the PV Pioneer {open_quotes}green pricing{close_quotes} program to advance PV commercialization.« less

A novel grid multiwing chaotic system with only non-hyperbolic equilibria

NASA Astrophysics Data System (ADS)

Zhang, Sen; Zeng, Yicheng; Li, Zhijun; Wang, Mengjiao; Xiong, Le

2018-05-01

The structure of the chaotic attractor of a system is mainly determined by the nonlinear functions in system equations. By using a new saw-tooth wave function and a new stair function, a novel complex grid multiwing chaotic system which belongs to non-Shil'nikov chaotic system with non-hyperbolic equilibrium points is proposed in this paper. It is particularly interesting that the complex grid multiwing attractors are generated by increasing the number of non-hyperbolic equilibrium points, which are different from the traditional methods of realising multiwing attractors by adding the index-2 saddle-focus equilibrium points in double-wing chaotic systems. The basic dynamical properties of the new system, such as dissipativity, phase portraits, the stability of the equilibria, the time-domain waveform, power spectrum, bifurcation diagram, Lyapunov exponents, and so on, are investigated by theoretical analysis and numerical simulations. Furthermore, the corresponding electronic circuit is designed and simulated on the Multisim platform. The Multisim simulation results and the hardware experimental results are in good agreement with the numerical simulations of the same system on Matlab platform, which verify the feasibility of this new grid multiwing chaotic system.

Estimating the Impacts of Direct Load Control Programs Using GridPIQ, a Web-Based Screening Tool

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pal, Seemita; Thayer, Brandon L.; Barrett, Emily L.

In direct load control (DLC) programs, utilities can curtail the demand of participating loads to contractually agreed-upon levels during periods of critical peak load, thereby reducing stress on the system, generation cost, and required transmission and generation capacity. Participating customers receive financial incentives. The impacts of implementing DLC programs extend well beyond peak shaving. There may be a shift of load proportional to the interrupted load to the times before or after a DLC event, and different load shifts have different consequences. Tools that can quantify the impacts of such programs on load curves, peak demand, emissions, and fossil fuelmore » costs are currently lacking. The Grid Project Impact Quantification (GridPIQ) screening tool includes a Direct Load Control module, which takes into account project-specific inputs as well as the larger system context in order to quantify the impacts of a given DLC program. This allows users (utilities, researchers, etc.) to test and compare different program specifications and their impacts.« less

Multi-Resolution Unstructured Grid-Generation for Geophysical Applications on the Sphere

NASA Technical Reports Server (NTRS)

Engwirda, Darren

2015-01-01

An algorithm for the generation of non-uniform unstructured grids on ellipsoidal geometries is described. This technique is designed to generate high quality triangular and polygonal meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric and ocean simulation, and numerical weather predication. Using a recently developed Frontal-Delaunay-refinement technique, a method for the construction of high-quality unstructured ellipsoidal Delaunay triangulations is introduced. A dual polygonal grid, derived from the associated Voronoi diagram, is also optionally generated as a by-product. Compared to existing techniques, it is shown that the Frontal-Delaunay approach typically produces grids with near-optimal element quality and smooth grading characteristics, while imposing relatively low computational expense. Initial results are presented for a selection of uniform and non-uniform ellipsoidal grids appropriate for large-scale geophysical applications. The use of user-defined mesh-sizing functions to generate smoothly graded, non-uniform grids is discussed.

Electrically heated particulate filter embedded heater design

DOEpatents

Gonze, Eugene V.; Chapman, Mark R.

2014-07-01

An exhaust system that processes exhaust generated by an engine is provided. The system generally includes a particulate filter (PF) that filters particulates from the exhaust wherein an upstream end of the PF receives exhaust from the engine and wherein an upstream surface of the particulate filter includes machined grooves. A grid of electrically resistive material is inserted into the machined grooves of the exterior upstream surface of the PF and selectively heats exhaust passing through the grid to initiate combustion of particulates within the PF.

Characterization of Slosh Damping for Ortho-Grid and Iso-Grid Internal Tank Structures

NASA Technical Reports Server (NTRS)

Westra, Douglas G.; Sansone, Marco D.; Eberhart, Chad J.; West, Jeffrey S.

2016-01-01

Grid stiffened tank structures such as Ortho-Grid and Iso-Grid are widely used in cryogenic tanks for providing stiffening to the tank while reducing mass, compared to tank walls of constant cross-section. If the structure is internal to the tank, it will positively affect the fluid dynamic behavior of the liquid propellant, in regard to fluid slosh damping. As NASA and commercial companies endeavor to explore the solar system, vehicles will by necessity become more mass efficient, and design margin will be reduced where possible. Therefore, if the damping characteristics of the Ortho-Grid and Iso-Grid structure is understood, their positive damping effect can be taken into account in the systems design process. Historically, damping by internal structures has been characterized by rules of thumb and for Ortho-Grid, empirical design tools intended for slosh baffles of much larger cross-section have been used. There is little or no information available to characterize the slosh behavior of Iso-Grid internal structure. Therefore, to take advantage of these structures for their positive damping effects, there is much need for obtaining additional data and tools to characterize them. Recently, the NASA Marshall Space Flight Center conducted both sub-scale testing and computational fluid dynamics (CFD) simulations of slosh damping for Ortho-Grid and Iso-Grid tanks for cylindrical tanks containing water. Enhanced grid meshing techniques were applied to the geometrically detailed and complex Ortho-Grid and Iso-Grid structures. The Loci-STREAM CFD program with the Volume of Fluid Method module for tracking and locating the water-air fluid interface was used to conduct the simulations. The CFD simulations were validated with the test data and new empirical models for predicting damping and frequency of Ortho-Grid and Iso-Grid structures were generated.

Progress in Grid Generation: From Chimera to DRAGON Grids

NASA Technical Reports Server (NTRS)

Liou, Meng-Sing; Kao, Kai-Hsiung

1994-01-01

Hybrid grids, composed of structured and unstructured grids, combines the best features of both. The chimera method is a major stepstone toward a hybrid grid from which the present approach is evolved. The chimera grid composes a set of overlapped structured grids which are independently generated and body-fitted, yielding a high quality grid readily accessible for efficient solution schemes. The chimera method has been shown to be efficient to generate a grid about complex geometries and has been demonstrated to deliver accurate aerodynamic prediction of complex flows. While its geometrical flexibility is attractive, interpolation of data in the overlapped regions - which in today's practice in 3D is done in a nonconservative fashion, is not. In the present paper we propose a hybrid grid scheme that maximizes the advantages of the chimera scheme and adapts the strengths of the unstructured grid while at the same time keeps its weaknesses minimal. Like the chimera method, we first divide up the physical domain by a set of structured body-fitted grids which are separately generated and overlaid throughout a complex configuration. To eliminate any pure data manipulation which does not necessarily follow governing equations, we use non-structured grids only to directly replace the region of the arbitrarily overlapped grids. This new adaptation to the chimera thinking is coined the DRAGON grid. The nonstructured grid region sandwiched between the structured grids is limited in size, resulting in only a small increase in memory and computational effort. The DRAGON method has three important advantages: (1) preserving strengths of the chimera grid; (2) eliminating difficulties sometimes encountered in the chimera scheme, such as the orphan points and bad quality of interpolation stencils; and (3) making grid communication in a fully conservative and consistent manner insofar as the governing equations are concerned. To demonstrate its use, the governing equations are discretized using the newly proposed flux scheme, AUSM+, which will be briefly described herein. Numerical tests on representative 2D inviscid flows are given for demonstration. Finally, extension to 3D is underway, only paced by the availability of the 3D unstructured grid generator.

Elliptic Curve Cryptography-Based Authentication with Identity Protection for Smart Grids

PubMed Central

Zhang, Liping; Tang, Shanyu; Luo, He

2016-01-01

In a smart grid, the power service provider enables the expected power generation amount to be measured according to current power consumption, thus stabilizing the power system. However, the data transmitted over smart grids are not protected, and then suffer from several types of security threats and attacks. Thus, a robust and efficient authentication protocol should be provided to strength the security of smart grid networks. As the Supervisory Control and Data Acquisition system provides the security protection between the control center and substations in most smart grid environments, we focus on how to secure the communications between the substations and smart appliances. Existing security approaches fail to address the performance-security balance. In this study, we suggest a mitigation authentication protocol based on Elliptic Curve Cryptography with privacy protection by using a tamper-resistant device at the smart appliance side to achieve a delicate balance between performance and security of smart grids. The proposed protocol provides some attractive features such as identity protection, mutual authentication and key agreement. Finally, we demonstrate the completeness of the proposed protocol using the Gong-Needham- Yahalom logic. PMID:27007951

Elliptic Curve Cryptography-Based Authentication with Identity Protection for Smart Grids.

PubMed

Zhang, Liping; Tang, Shanyu; Luo, He

2016-01-01

In a smart grid, the power service provider enables the expected power generation amount to be measured according to current power consumption, thus stabilizing the power system. However, the data transmitted over smart grids are not protected, and then suffer from several types of security threats and attacks. Thus, a robust and efficient authentication protocol should be provided to strength the security of smart grid networks. As the Supervisory Control and Data Acquisition system provides the security protection between the control center and substations in most smart grid environments, we focus on how to secure the communications between the substations and smart appliances. Existing security approaches fail to address the performance-security balance. In this study, we suggest a mitigation authentication protocol based on Elliptic Curve Cryptography with privacy protection by using a tamper-resistant device at the smart appliance side to achieve a delicate balance between performance and security of smart grids. The proposed protocol provides some attractive features such as identity protection, mutual authentication and key agreement. Finally, we demonstrate the completeness of the proposed protocol using the Gong-Needham-Yahalom logic.

Effects of Scandinavian hydro power on storage needs in a fully renewable European power system for various transmission capacity scenarios

NASA Astrophysics Data System (ADS)

Kies, Alexander; Nag, Kabitri; von Bremen, Lueder; Lorenz, Elke; Heinemann, Detlev

2015-04-01

The penetration of renewable energies in the European power system has increased in the last decades (23.5% share of renewables in the gross electricity consumption of the EU-28 in 2012) and is expected to increase further up to very high shares close to 100%. Planning and organizing this European energy transition towards sustainable power sources will be one of the major challenges of the 21st century. It is very likely that in a fully renewable European power system wind and photovoltaics (pv) will contribute the largest shares to the generation mix followed by hydro power. However, feed-in from wind and pv is due to the weather dependant nature of their resources fluctuating and non-controllable. To match generation and consumption several solutions and their combinations were proposed like very high backup-capacities of conventional power generation (e.g. fossile or nuclear), storages or the extension of the transmission grid. Apart from those options hydro power can be used to counterbalance fluctuating wind and pv generation to some extent. In this work we investigate the effects of hydro power from Norway and Sweden on residual storage needs in Europe depending on the overlaying grid scenario. High temporally and spatially resolved weather data with a spatial resolution of 7 x 7 km and a temporal resolution of 1 hour was used to model the feed-in from wind and pv for 34 investigated European countries for the years 2003-2012. Inflow into hydro storages and generation by run-of-river power plants were computed from ERA-Interim reanalysis runoff data at a spatial resolution of 0.75° x 0.75° and a daily temporal resolution. Power flows in a simplified transmission grid connecting the 34 European countries were modelled minimizing dissipation using a DC-flow approximation. Previous work has shown that hydro power, namely in Norway and Sweden, can reduce storage needs in a renewable European power system by a large extent. A 15% share of hydro power in Europe can reduce storage needs by up to 50% with respect to stored energy. This requires however large transmission capacities between the major hydro power producers in Scandinavia and the largest consumers of electrical energy in Western Europe. We show how Scandinavian hydro power can reduce storage needs in dependency of the transmission grid for two fully renewable scenarios: The first one has its wind and pv generation capacities distributed according to an empirically derived approach. The second scenario has an optimal spatial distribution to minimize storage needs distribution of wind and pv generation capacities across Europe. We show that in both cases hydro power together with a well developed transmission grid has the potential to contribute a large share to the solution of the generation-consumption mismatch problem. The work is part of the RESTORE 2050 project (BMBF) that investigates the requirements for cross-country grid extensions, usage of storage technologies and capacities and the development of new balancing technologies.

Smart signal processing for an evolving electric grid

NASA Astrophysics Data System (ADS)

Silva, Leandro Rodrigues Manso; Duque, Calos Augusto; Ribeiro, Paulo F.

2015-12-01

Electric grids are interconnected complex systems consisting of generation, transmission, distribution, and active loads, recently called prosumers as they produce and consume electric energy. Additionally, these encompass a vast array of equipment such as machines, power transformers, capacitor banks, power electronic devices, motors, etc. that are continuously evolving in their demand characteristics. Given these conditions, signal processing is becoming an essential assessment tool to enable the engineer and researcher to understand, plan, design, and operate the complex and smart electronic grid of the future. This paper focuses on recent developments associated with signal processing applied to power system analysis in terms of characterization and diagnostics. The following techniques are reviewed and their characteristics and applications discussed: active power system monitoring, sparse representation of power system signal, real-time resampling, and time-frequency (i.e., wavelets) applied to power fluctuations.

Simulation of demand-response power management in smart city

NASA Astrophysics Data System (ADS)

Kadam, Kshitija

Smart Grids manage energy efficiently through intelligent monitoring and control of all the components connected to the electrical grid. Advanced digital technology, combined with sensors and power electronics, can greatly improve transmission line efficiency. This thesis proposed a model of a deregulated grid which supplied power to diverse set of consumers and allowed them to participate in decision making process through two-way communication. The deregulated market encourages competition at the generation and distribution levels through communication with the central system operator. A software platform was developed and executed to manage the communication, as well for energy management of the overall system. It also demonstrated self-healing property of the system in case a fault occurs, resulting in an outage. The system not only recovered from the fault but managed to do so in a short time with no/minimum human involvement.

Specialized CFD Grid Generation Methods for Near-Field Sonic Boom Prediction

NASA Technical Reports Server (NTRS)

Park, Michael A.; Campbell, Richard L.; Elmiligui, Alaa; Cliff, Susan E.; Nayani, Sudheer N.

2014-01-01

Ongoing interest in analysis and design of low sonic boom supersonic transports re- quires accurate and ecient Computational Fluid Dynamics (CFD) tools. Specialized grid generation techniques are employed to predict near- eld acoustic signatures of these con- gurations. A fundamental examination of grid properties is performed including grid alignment with ow characteristics and element type. The issues a ecting the robustness of cylindrical surface extrusion are illustrated. This study will compare three methods in the extrusion family of grid generation methods that produce grids aligned with the freestream Mach angle. These methods are applied to con gurations from the First AIAA Sonic Boom Prediction Workshop.

DRAGON Grid: A Three-Dimensional Hybrid Grid Generation Code Developed

NASA Technical Reports Server (NTRS)

Liou, Meng-Sing

2000-01-01

Because grid generation can consume 70 percent of the total analysis time for a typical three-dimensional viscous flow simulation for a practical engineering device, payoffs from research and development could reduce costs and increase throughputs considerably. In this study, researchers at the NASA Glenn Research Center at Lewis Field developed a new hybrid grid approach with the advantages of flexibility, high-quality grids suitable for an accurate resolution of viscous regions, and a low memory requirement. These advantages will, in turn, reduce analysis time and increase accuracy. They result from an innovative combination of structured and unstructured grids to represent the geometry and the computation domain. The present approach makes use of the respective strengths of both the structured and unstructured grid methods, while minimizing their weaknesses. First, the Chimera grid generates high-quality, mostly orthogonal meshes around individual components. This process is flexible and can be done easily. Normally, these individual grids are required overlap each other so that the solution on one grid can communicate with another. However, when this communication is carried out via a nonconservative interpolation procedure, a spurious solution can result. Current research is aimed at entirely eliminating this undesired interpolation by directly replacing arbitrary grid overlapping with a nonstructured grid called a DRAGON grid, which uses the same set of conservation laws over the entire region, thus ensuring conservation everywhere. The DRAGON grid is shown for a typical film-cooled turbine vane with 33 holes and 3 plenum compartments. There are structured grids around each geometrical entity and unstructured grids connecting them. In fiscal year 1999, Glenn researchers developed and tested the three-dimensional DRAGON grid-generation tools. A flow solver suitable for the DRAGON grid has been developed, and a series of validation tests are underway.

Feasibility of a simple method of hybrid collimation for megavoltage grid therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Almendral, Pedro; Mancha, Pedro J.; Roberto, Daniel

2013-05-15

Purpose: Megavoltage grid therapy is currently delivered with step-and-shoot multisegment techniques or using a high attenuation block with divergent holes. However, the commercial availability of grid blocks is limited, their construction is difficult, and step-and-shoot techniques require longer treatment times and are not practical with some multileaf collimators. This work studies the feasibility of a hybrid collimation system for grid therapy that does not require multiple segments and can be easily implemented with widely available technical means. Methods: The authors have developed a system to generate a grid of beamlets by the simultaneous use of two perpendicular sets of equallymore » spaced leaves that project stripe patterns in orthogonal directions. One of them is generated with the multileaf collimator integrated in the accelerator and the other with an in-house made collimator constructed with a low melting point alloy commonly available at radiation oncology departments. The characteristics of the grid fields for 6 and 18 MV have been studied with a shielded diode, an unshielded diode, and radiochromic film. Results: The grid obtained with the hybrid collimation is similar to some of the grids used clinically with respect to the beamlet size (about 1 cm) and the percentage of open beam (1/4 of the total field). The grid fields are less penetrating than the open fields of the same energy. Depending on the depth and the direction of the profiles (diagonal or along the principal axes), the measured valley-to-peak dose ratios range from 5% to 16% for 6 MV and from 9% to 20% for 18 MV. All the detectors yield similar results in the measurement of profiles and percent depth dose, but the shielded diode seems to overestimate the output factors. Conclusions: The combination of two stripe pattern collimators in orthogonal directions is a feasible method to obtain two-dimensional arrays of beamlets and has potential usefulness as an efficient way to deliver grid therapy. The implementation of this method is technically simpler than the construction of a conventional grid block.« less

Feasibility of a simple method of hybrid collimation for megavoltage grid therapy.

PubMed

Almendral, Pedro; Mancha, Pedro J; Roberto, Daniel

2013-05-01

Megavoltage grid therapy is currently delivered with step-and-shoot multisegment techniques or using a high attenuation block with divergent holes. However, the commercial availability of grid blocks is limited, their construction is difficult, and step-and-shoot techniques require longer treatment times and are not practical with some multileaf collimators. This work studies the feasibility of a hybrid collimation system for grid therapy that does not require multiple segments and can be easily implemented with widely available technical means. The authors have developed a system to generate a grid of beamlets by the simultaneous use of two perpendicular sets of equally spaced leaves that project stripe patterns in orthogonal directions. One of them is generated with the multileaf collimator integrated in the accelerator and the other with an in-house made collimator constructed with a low melting point alloy commonly available at radiation oncology departments. The characteristics of the grid fields for 6 and 18 MV have been studied with a shielded diode, an unshielded diode, and radiochromic film. The grid obtained with the hybrid collimation is similar to some of the grids used clinically with respect to the beamlet size (about 1 cm) and the percentage of open beam (1/4 of the total field). The grid fields are less penetrating than the open fields of the same energy. Depending on the depth and the direction of the profiles (diagonal or along the principal axes), the measured valley-to-peak dose ratios range from 5% to 16% for 6 MV and from 9% to 20% for 18 MV. All the detectors yield similar results in the measurement of profiles and percent depth dose, but the shielded diode seems to overestimate the output factors. The combination of two stripe pattern collimators in orthogonal directions is a feasible method to obtain two-dimensional arrays of beamlets and has potential usefulness as an efficient way to deliver grid therapy. The implementation of this method is technically simpler than the construction of a conventional grid block.

A Geometry Based Infra-structure for Computational Analysis and Design

NASA Technical Reports Server (NTRS)

Haimes, Robert

1997-01-01

The computational steps traditionally taken for most engineering analysis (CFD, structural analysis, and etc.) are: Surface Generation - usually by employing a CAD system; Grid Generation - preparing the volume for the simulation; Flow Solver - producing the results at the specified operational point; and Post-processing Visualization - interactively attempting to understand the results For structural analysis, integrated systems can be obtained from a number of commercial vendors. For CFD, these steps have worked well in the past for simple steady-state simulations at the expense of much user interaction. The data was transmitted between phases via files. Specifically the problems with this procedure are: (1) File based. Information flows from one step to the next via data files with formats specified for that procedure. (2) 'Good' Geometry. A bottleneck in getting results from a solver is the construction of proper geometry to be fed to the grid generator. With 'good' geometry a grid can be constructed in tens of minutes (even with a complex configuration) using unstructured techniques. (3) One-Way communication. All information travels on from one phase to the next. Until this process can be automated, more complex problems such as multi-disciplinary analysis or using the above procedure for design becomes prohibitive.

Rotor Current Control of DFIG for Improving Fault Ride - Through Using a Novel Sliding Mode Control Approach

NASA Astrophysics Data System (ADS)

Cai, Guowei; Liu, Cheng; Yang, Deyou

2013-11-01

The doubly fed induction generators (DFIG) have been recognized as the dominant technology used in wind power generation systems with the rapid development of wind power. However, continuous operation of DFIG may cause a serious wind turbine generators tripping accident, due to destructive over-current in the rotor winding which is caused by the power system fault or inefficient fault ride-through (FRT) strategy. A new rotor current control scheme in the rotor-side converter (RSC) ispresented to enhance FRT capacities of grid-connected DFIG. Due to the strongly nonlinear nature of DFIG and insensitive to DFIG parameter's variations, a novel sliding mode controller was designed. The controller combines extended state observer (ESO) with sliding model variable structure control theory. The simulation is carried out to verify the effectiveness of the proposed control approach under various types of grid disturbances. It is shown that the proposed controller provides enhanced transient features than the classic proportional-integral control. The proposed control method can effectively reduce over-current in the RSC, and the transient pulse value of electromagnetic torque is too large under power grid fault.

Determination and representation of electric charge distributions associated with adverse weather conditions

NASA Technical Reports Server (NTRS)

Rompala, John T.

1992-01-01

Algorithms are presented for determining the size and location of electric charges which model storm systems and lightning strikes. The analysis utilizes readings from a grid of ground level field mills and geometric constraints on parameters to arrive at a representative set of charges. This set is used to generate three dimensional graphical depictions of the set as well as contour maps of the ground level electrical environment over the grid. The composite, analytic and graphic package is demonstrated and evaluated using controlled input data and archived data from a storm system. The results demonstrate the packages utility as: an operational tool in appraising adverse weather conditions; a research tool in studies of topics such as storm structure, storm dynamics, and lightning; and a tool in designing and evaluating grid systems.

The vulnerabilities of the power-grid system: renewable microgrids as an alternative source of energy.

PubMed

Meyer, Victor; Myres, Charles; Bakshi, Nitin

2010-03-01

The objective of this paper is to analyse the vulnerabilities of current power-grid systems and to propose alternatives to using fossil fuel power generation and infrastructure solutions in the form of microgrids, particularly those from renewable energy sources. One of the key potential benefits of microgrids, apart from their inherent sustainability and ecological advantages, is increased resilience. The analysis is targeted towards the context of business process outsourcing in India. However, much of the research on vulnerabilities has been derived from the USA and as such many of the examples cite vulnerabilities in the USA and other developed economies. Nevertheless, the vulnerabilities noted are to a degree common to all grid systems, and so the analysis may be more broadly applicable.

Application of numerical grid generation for improved CFD analysis of multiphase screw machines

NASA Astrophysics Data System (ADS)

Rane, S.; Kovačević, A.

2017-08-01

Algebraic grid generation is widely used for discretization of the working domain of twin screw machines. Algebraic grid generation is fast and has good control over the placement of grid nodes. However, the desired qualities of grid which should be able to handle multiphase flows such as oil injection, may be difficult to achieve at times. In order to obtain fast solution of multiphase screw machines, it is important to further improve the quality and robustness of the computational grid. In this paper, a deforming grid of a twin screw machine is generated using algebraic transfinite interpolation to produce initial mesh upon which an elliptic partial differential equations (PDE) of the Poisson’s form is solved numerically to produce smooth final computational mesh. The quality of numerical cells and their distribution obtained by the differential method is greatly improved. In addition, a similar procedure was introduced to fully smoothen the transition of the partitioning rack curve between the rotors thus improving continuous movement of grid nodes and in turn improve robustness and speed of the Computational Fluid Dynamic (CFD) solver. Analysis of an oil injected twin screw compressor is presented to compare the improvements in grid quality factors in the regions of importance such as interlobe space, radial tip and the core of the rotor. The proposed method that combines algebraic and differential grid generation offer significant improvement in grid quality and robustness of numerical solution.

Opportunity to Plug Your Car Into the Electric Grid is Arriving

DOE Office of Scientific and Technical Information (OSTI.GOV)

Griego, G.

2010-06-01

Plug-in hybrid electric vehicles are hitting the U.S. market for the first time this year. Similar to hybrid electric vehicles, they feature a larger battery and plug-in charger that allows consumers to replace a portion of their fossil fuel by simply plugging their cars into standard 110-volt outlets at home or wherever outlets are available. If these vehicles become widely accepted, consumers and the environment will benefit, according to a computer modeling study by Xcel Energy and the Department of Energy's National Renewable Energy Laboratory. Researchers found that each PHEV would cut carbon dioxide emissions in half and save ownersmore » up to $450 in annual fuel costs and up to 240 gallons of gasoline. The study also looked at the impact of PHEVs on the electric grid in Colorado if used on a large scale. Integrating large numbers of these vehicles will depend on the adoption of smart-grid technology - adding digital elements to the electric power system to improve efficiency and enable more dynamic communication between consumers and producers of electricity. Using an intelligent monitoring system that keeps track of all electricity flowing in the system, a smart grid could enable optimal PHEV battery-charging much the same way it would enable users to manage their energy use in household appliances and factory processes to reduce energy costs. When a smart grid is implemented, consumers will have many low-cost opportunities to charge PHEVs at different times of the day. Plug-in vehicles could contribute electricity at peak times, such as summer evenings, while taking electricity from the grid at low-use times such as the middle of the night. Electricity rates could offer incentives for drivers to 'give back' electricity when it is most needed and to 'take' it when it is plentiful. The integration of PHEVs, solar arrays and wind turbines into the grid at larger scales will require a more modern electricity system. Technology already exists to allow customers to feed excess power from their own renewable energy systems back to the grid. As more homes and businesses find opportunities to plan power flows to and from the grid for economic gain using their renewable energy systems and PHEVs, more sophisticated systems will be needed. A smart grid will improve the efficiency of energy consumption, manage real-time power flows and provide two-way metering needed to compensate small power producers. Many states are working toward the smart-grid concept, particularly to incorporate renewable sources into their utility grids. According to the Department of Energy, 30 states have developed and adopted renewable portfolio standards, which require up to 20 percent of a state's energy portfolio to come exclusively from renewable sources by this year, and up to 30 percent in the future. NREL has been laying the foundation for both PHEVs and the smart grid for many years with work including modifying hybrid electric cars with plug-in technology; studying fuel economy, batteries and power electronics; exploring options for recharging batteries with solar and wind technologies; and measuring reductions in greenhouse gas emissions. The laboratory participated in development of smart-grid implementation standards with industry, utilities, government and others to guide the integration of renewable and other small electricity generation and storage sources. Dick DeBlasio, principal program manager for electricity programs, is now leading the Institute of Electrical and Electronics Engineers Standards efforts to connect the dots regarding power generation, communication and information technologies.« less

Real time hardware implementation of power converters for grid integration of distributed generation and STATCOM systems

NASA Astrophysics Data System (ADS)

Jaithwa, Ishan

Deployment of smart grid technologies is accelerating. Smart grid enables bidirectional flows of energy and energy-related communications. The future electricity grid will look very different from today's power system. Large variable renewable energy sources will provide a greater portion of electricity, small DERs and energy storage systems will become more common, and utilities will operate many different kinds of energy efficiency. All of these changes will add complexity to the grid and require operators to be able to respond to fast dynamic changes to maintain system stability and security. This thesis investigates advanced control technology for grid integration of renewable energy sources and STATCOM systems by verifying them on real time hardware experiments using two different systems: d SPACE and OPAL RT. Three controls: conventional, direct vector control and the intelligent Neural network control were first simulated using Matlab to check the stability and safety of the system and were then implemented on real time hardware using the d SPACE and OPAL RT systems. The thesis then shows how dynamic-programming (DP) methods employed to train the neural networks are better than any other controllers where, an optimal control strategy is developed to ensure effective power delivery and to improve system stability. Through real time hardware implementation it is proved that the neural vector control approach produces the fastest response time, low overshoot, and, the best performance compared to the conventional standard vector control method and DCC vector control technique. Finally the entrepreneurial approach taken to drive the technologies from the lab to market via ORANGE ELECTRIC is discussed in brief.

Study on DFIG wind turbines control strategy for improving frequency response characteristics

NASA Astrophysics Data System (ADS)

Zhao, Dongmei; Wu, Di; Liu, Yanhua; Zhou, Zhiyu

2012-01-01

The active and reactive power decoupling control for the double-fed induction generator wind turbines(DFIG) does not play a positive role to the frequency response ability of power grid because it performs as the hidden inertia for the power grid. If we want to improve the transient frequency stability of the wind turbine when it is integrated with the system, we must ameliorate its frequency response characteristics. The inability of frequency control due to DFIG decoupling control could be overcome through releasing (or absorbing) a part of the kinetic energy stored in the rotor, so as to increase (or decrease) active power injected to the power system when the deviation of power system frequency appears. This paper discusses the mathematical model of the variable speed DFIG, including the aerodynamic model, pitch control system model, shaft model, generator model and inverter control model, and other key components, focusing on the mathematical model of the converters in rotor side and grid side. Based on the existing model of wind generator, the paper attaches the frequency control model on the platform of the simulation software DIgSILENT/PowerFactory. The simulation results show that the proposed control strategy can response quickly to transient frequency deviation and prove that wind farms can participate in the system frequency regulation to a certain extent. Finally, the result verifies the accuracy and plausibility of the inverter control model which attaches the frequency control module.

Study on DFIG wind turbines control strategy for improving frequency response characteristics

NASA Astrophysics Data System (ADS)

Zhao, Dongmei; Wu, Di; Liu, Yanhua; Zhou, Zhiyu

2011-12-01

The active and reactive power decoupling control for the double-fed induction generator wind turbines(DFIG) does not play a positive role to the frequency response ability of power grid because it performs as the hidden inertia for the power grid. If we want to improve the transient frequency stability of the wind turbine when it is integrated with the system, we must ameliorate its frequency response characteristics. The inability of frequency control due to DFIG decoupling control could be overcome through releasing (or absorbing) a part of the kinetic energy stored in the rotor, so as to increase (or decrease) active power injected to the power system when the deviation of power system frequency appears. This paper discusses the mathematical model of the variable speed DFIG, including the aerodynamic model, pitch control system model, shaft model, generator model and inverter control model, and other key components, focusing on the mathematical model of the converters in rotor side and grid side. Based on the existing model of wind generator, the paper attaches the frequency control model on the platform of the simulation software DIgSILENT/PowerFactory. The simulation results show that the proposed control strategy can response quickly to transient frequency deviation and prove that wind farms can participate in the system frequency regulation to a certain extent. Finally, the result verifies the accuracy and plausibility of the inverter control model which attaches the frequency control module.

Can developing countries leapfrog the centralized electrification paradigm?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levin, Todd; Thomas, Valerie M.

Due to the rapidly decreasing costs of small renewable electricity generation 'systems, centralized power systems are no longer a necessary condition of universal access to modern energy services. Developing countries, where centralized electricity infrastructures are less developed, may be able to adopt these new technologies more quickly. We first review the costs of grid extension and distributed solar home systems (SHSs) as reported by a number of different studies. We then present a general analytic framework for analyzing the choice between extending the grid and implementing distributed solar home systems. Drawing upon reported grid expansion cost data for three specificmore » regions, we demonstrate this framework by determining the electricity consumption levels at which the costs of provision through centralized and decentralized approaches are equivalent in these regions. We then calculate SHS capital costs that are necessary for these technologies provide each of five tiers of energy access, as defined by the United Nations Sustainable Energy for All initiative. Our results suggest that solar home systems can play an important role in achieving universal access to basic energy services. The extent of this role depends on three primary factors: SHS costs, grid expansion costs, and centralized generation costs. Given current technology costs, centralized systems will still be required to enable higher levels of consumption; however, cost reduction trends have the potential to disrupt this paradigm. By looking ahead rather than replicating older infrastructure styles, developing countries can leapfrog to a more distributed electricity service model. (C) 2016 International Energy Initiative. Published by Elsevier Inc. All rights reserved.« less

Automatic blocking for complex three-dimensional configurations

NASA Technical Reports Server (NTRS)

Dannenhoffer, John F., III

1995-01-01

A new blocking technique for complex three-dimensional configurations is described. This new technique is based upon the concept of an abstraction, or squared-up representation, of the configuration and the associated grid. By allowing the user to describe blocking requirements in natural terms (such as 'wrap a grid around this leading edge' or 'make all grid lines emanating from this wall orthogonal to it'), users can quickly generate complex grids around complex configurations, while still maintaining a high level of control where desired. An added advantage of the abstraction concept is that once a blocking is defined for a class of configurations, it can be automatically applied to other configurations of the same class, making the new technique particularly well suited for the parametric variations which typically occur during design processes. Grids have been generated for a variety of real-world, two- and three-dimensional configurations. In all cases, the time required to generate the grid, given just an electronic form of the configuration, was at most a few days. Hence with this new technique, the generation of a block-structured grid is only slightly more expensive than the generation of an unstructured grid for the same configuration.

Renewable Energy Power Generation Estimation Using Consensus Algorithm

NASA Astrophysics Data System (ADS)

Ahmad, Jehanzeb; Najm-ul-Islam, M.; Ahmed, Salman

2017-08-01

At the small consumer level, Photo Voltaic (PV) panel based grid tied systems are the most common form of Distributed Energy Resources (DER). Unlike wind which is suitable for only selected locations, PV panels can generate electricity almost anywhere. Pakistan is currently one of the most energy deficient countries in the world. In order to mitigate this shortage the Government has recently announced a policy of net-metering for residential consumers. After wide spread adoption of DERs, one of the issues that will be faced by load management centers would be accurate estimate of the amount of electricity being injected in the grid at any given time through these DERs. This becomes a critical issue once the penetration of DER increases beyond a certain limit. Grid stability and management of harmonics becomes an important consideration where electricity is being injected at the distribution level and through solid state controllers instead of rotating machinery. This paper presents a solution using graph theoretic methods for the estimation of total electricity being injected in the grid in a wide spread geographical area. An agent based consensus approach for distributed computation is being used to provide an estimate under varying generation conditions.

Upgrades of Two Computer Codes for Analysis of Turbomachinery

NASA Technical Reports Server (NTRS)

Chima, Rodrick V.; Liou, Meng-Sing

2005-01-01

Major upgrades have been made in two of the programs reported in "ive Computer Codes for Analysis of Turbomachinery". The affected programs are: Swift -- a code for three-dimensional (3D) multiblock analysis; and TCGRID, which generates a 3D grid used with Swift. Originally utilizing only a central-differencing scheme for numerical solution, Swift was augmented by addition of two upwind schemes that give greater accuracy but take more computing time. Other improvements in Swift include addition of a shear-stress-transport turbulence model for better prediction of adverse pressure gradients, addition of an H-grid capability for flexibility in modeling flows in pumps and ducts, and modification to enable simultaneous modeling of hub and tip clearances. Improvements in TCGRID include modifications to enable generation of grids for more complicated flow paths and addition of an option to generate grids compatible with the ADPAC code used at NASA and in industry. For both codes, new test cases were developed and documentation was updated. Both codes were converted to Fortran 90, with dynamic memory allocation. Both codes were also modified for ease of use in both UNIX and Windows operating systems.

Grid flexibility: The quiet revolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsieh, Eric; Anderson, Robert

The concept of flexibility describes the capability of the power system to maintain balance between generation and load under uncertainty. While the grid has historically incorporated flexibility-specific resources such as pumped hydro to complement nuclear generators, modern trends and the increased deployment of variable energy resources (VERs) are increasing the need for a transparent market value of flexibility. A review of analyses, docket filings, tariffs, and business practice manuals from the past several years finds substantial flexibility-related activity. These activities are categorized as market and financial structures; incorporation of new operations or technology; and legal or procedural reforms. The cumulativemore » outcome of these incremental changes will be a major transformation to power systems that can rapidly adapt to new needs, technologies, and conditions.« less

Grid flexibility: The quiet revolution

DOE PAGES

Hsieh, Eric; Anderson, Robert

2017-02-16

The concept of flexibility describes the capability of the power system to maintain balance between generation and load under uncertainty. While the grid has historically incorporated flexibility-specific resources such as pumped hydro to complement nuclear generators, modern trends and the increased deployment of variable energy resources (VERs) are increasing the need for a transparent market value of flexibility. A review of analyses, docket filings, tariffs, and business practice manuals from the past several years finds substantial flexibility-related activity. These activities are categorized as market and financial structures; incorporation of new operations or technology; and legal or procedural reforms. The cumulativemore » outcome of these incremental changes will be a major transformation to power systems that can rapidly adapt to new needs, technologies, and conditions.« less

How a future energy world could look?

NASA Astrophysics Data System (ADS)

Ewert, M.

2012-10-01

The future energy system will change significantly within the next years as a result of the following Mega Trends: de-carbonization, urbanization, fast technology development, individualization, glocalization (globalization and localization) and changing demographics. Increasing fluctuating renewable production will change the role of non-renewable generation. Distributed energy from renewables and micro generation will change the direction of the energy flow in the electricity grids. Production will not follow demand but demand has to follow production. This future system is enabled by the fast technical development of information and communication technologies which will be present in the entire system. In this paper the results of a comprehensive analysis with different scenarios is summarized. Tools were used like the analysis of policy trends in the European countries, modelling of the European power grid, modelling of the European power markets and the analysis of technology developments with cost reduction potentials. With these tools the interaction of the main actors in the energy markets like conventional generation and renewable generation, grid transport, electricity storage including new storage options from E-Mobility, Power to Gas, Compressed Air Energy storage and demand side management were considered. The potential application of technologies and investments in new energy technologies were analyzed within existing frameworks and markets as well as new business models in new markets with different frameworks. In the paper the over all trend of this analysis is presented by describing a potential future energy world. This world represents only one of numerous options with comparable characteristics.

Dynamic Modeling and Grid Interaction of a Tidal and River Generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muljadi, Eduard; Gevorgian, Vahan; Donegan, James

This presentation provides a high-level overview of the deployment of a river generator installed in a small system. The turbine dynamics of a river generator, electrical generator, and power converter are modeled in detail. Various simulations can be exercised, and the impact of different control algorithms, failures of power switches, and corresponding impacts can be examined.

Enhancement of Voltage Stability of DC Smart Grid During Islanded Mode by Load Shedding Scheme

NASA Astrophysics Data System (ADS)

Nassor, Thabit Salim; Senjyu, Tomonobu; Yona, Atsushi

2015-10-01

This paper presents the voltage stability of a DC smart grid based on renewable energy resources during grid connected and isolated modes. During the islanded mode the load shedding, based on the state of charge of the battery and distribution line voltage, was proposed for voltage stability and reservation of critical load power. The analyzed power system comprises a wind turbine, a photovoltaic generator, storage battery as controllable load, DC loads, and power converters. A fuzzy logic control strategy was applied for power consumption control of controllable loads and the grid-connected dual active bridge series resonant converters. The proposed DC Smart Grid operation has been verified by simulation using MATLAB® and PLECS® Blockset. The obtained results show the effectiveness of the proposed method.

Dynamic Braking System of a Tidal Generator: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muljadi, Eduard; Wright, Alan; Gevorgian, Vahan

Renewable energy generation has experienced significant cost reductions during the past decades, and it has become more accepted by the global population. In the beginning, wind generation dominated the development and deployment of renewable energy; however, during recent decades, photovoltaic (PV) generation has grown at a very significant pace due to the tremendous decrease in the cost of PV modules. The focus on renewable energy generation has now expanded to include new types with promising future applications, such as river and tidal generation. The input water flow to these types of resources is more predictable than wind or solar generation.more » The data used in this paper is representative of a typical river or tidal generator. The analysis is based on a generator with a power rating of 40 kW. The tidal generator under consideration is driven by two sets of helical turbines connected to each side of the generator located in between the turbines. The generator is operated in variable speed, and it is controlled to maximize the energy harvested as well as the operation of the turbine generator. The electrical system consists of a three-phase permanent magnet generator connected to a three-phase passive rectifier. The output of the rectifier is connected to a DC-DC converter to match the rectifier output to the DC bus voltage of the DC-AC inverter. The three-phase inverter is connected to the grid, and it is controlled to provide a good interface with the grid. One important aspect of river and tidal generation is the braking mechanism. In a tidal generator, the braking mechanism is important to avoid a runaway condition in case the connection to the grid is lost when there is a fault in the lines. A runaway condition may lead to an overspeed condition and cause extreme stresses on the turbine blade structure and eventual disintegration of the mechanical structure. In this paper, the concept of the dynamic braking system is developed and investigated for normal and abnormal operations. The main objective is to optimize the performance under emergency braking while designing the system to be as simple as possible to avoid overdesigning the power electronics or exceeding the target budget.« less

Structural analysis and design for the development of floating photovoltaic energy generation system

NASA Astrophysics Data System (ADS)

Yoon, S. J.; Joo, H. J.; Kim, S. H.

2018-06-01

In this paper, we discussed the structural analysis and design for the development of floating photovoltaic energy generation system. Series of research conducted to develop the system from the analysis and design of the structural system to the installation of the system discussed. In the structural system supporting solar panels PFRP materials and SMC FRP materials used. A unit module structure is fabricated and then the unit module structures are connected each other to assemble whole PV energy generation complex. This system connected directly to the power grid system. In addition, extensive monitoring for the efficiency of electricity generation and the soundness of the structural system is in progress for the further system enhancement.

Design and Implementation of a C++ Multithreaded Operational Tool for the Generation of Detection Time Grids in 2D for P- and S-waves taking into Consideration Seismic Network Topology and Data Latency

NASA Astrophysics Data System (ADS)

Sardina, V.

2017-12-01

The Pacific Tsunami Warning Center's round the clock operations rely on the rapid determination of the source parameters of earthquakes occurring around the world. To rapidly estimate source parameters such as earthquake location and magnitude the PTWC analyzes data streams ingested in near-real time from a global network of more than 700 seismic stations. Both the density of this network and the data latency of its member stations at any given time have a direct impact on the speed at which the PTWC scientists on duty can locate an earthquake and estimate its magnitude. In this context, it turns operationally advantageous to have the ability of assessing how quickly the PTWC operational system can reasonably detect and locate and earthquake, estimate its magnitude, and send the corresponding tsunami message whenever appropriate. For this purpose, we designed and implemented a multithreaded C++ software package to generate detection time grids for both P- and S-waves after taking into consideration the seismic network topology and the data latency of its member stations. We first encapsulate all the parameters of interest at a given geographic point, such as geographic coordinates, P- and S-waves detection time in at least a minimum number of stations, and maximum allowed azimuth gap into a DetectionTimePoint class. Then we apply composition and inheritance to define a DetectionTimeLine class that handles a vector of DetectionTimePoint objects along a given latitude. A DetectionTimesGrid class in turn handles the dynamic allocation of new TravelTimeLine objects and assigning the calculation of the corresponding P- and S-waves' detection times to new threads. Finally, we added a GUI that allows the user to interactively set all initial calculation parameters and output options. Initial testing in an eight core system shows that generation of a global 2D grid at 1 degree resolution setting detection on at least 5 stations and no azimuth gap restriction takes under 25 seconds. Under the same initial conditions, generation of a 2D grid at 0.1 degree resolution (2.6 million grid points) takes no more than 22 minutes. This preliminary results show a significant gain in grid generation speed when compared to other implementation via either scripts, or previous versions of the C++ code that did not implement multithreading.

Full 3D Analysis of the GE90 Turbofan Primary Flowpath

NASA Technical Reports Server (NTRS)

Turner, Mark G.

2000-01-01

The multistage simulations of the GE90 turbofan primary flowpath components have been performed. The multistage CFD code, APNASA, has been used to analyze the fan, fan OGV and booster, the 10-stage high-pressure compressor and the entire turbine system of the GE90 turbofan engine. The code has two levels of parallel, and for the 18 blade row full turbine simulation has 87.3 percent parallel efficiency with 121 processors on an SGI ORIGIN. Grid generation is accomplished with the multistage Average Passage Grid Generator, APG. Results for each component are shown which compare favorably with test data.

PEGASUS 5: An Automated Pre-Processor for Overset-Grid CFD

NASA Technical Reports Server (NTRS)

Rogers, Stuart E.; Suhs, Norman; Dietz, William; Rogers, Stuart; Nash, Steve; Chan, William; Tramel, Robert; Onufer, Jeff

2006-01-01

This viewgraph presentation reviews the use and requirements of Pegasus 5. PEGASUS 5 is a code which performs a pre-processing step for the Overset CFD method. The code prepares the overset volume grids for the flow solver by computing the domain connectivity database, and blanking out grid points which are contained inside a solid body. PEGASUS 5 successfully automates most of the overset process. It leads to dramatic reduction in user input over previous generations of overset software. It also can lead to an order of magnitude reduction in both turn-around time and user expertise requirements. It is also however not a "black-box" procedure; care must be taken to examine the resulting grid system.

A Grid Infrastructure for Supporting Space-based Science Operations

NASA Technical Reports Server (NTRS)

Bradford, Robert N.; Redman, Sandra H.; McNair, Ann R. (Technical Monitor)

2002-01-01

Emerging technologies for computational grid infrastructures have the potential for revolutionizing the way computers are used in all aspects of our lives. Computational grids are currently being implemented to provide a large-scale, dynamic, and secure research and engineering environments based on standards and next-generation reusable software, enabling greater science and engineering productivity through shared resources and distributed computing for less cost than traditional architectures. Combined with the emerging technologies of high-performance networks, grids provide researchers, scientists and engineers the first real opportunity for an effective distributed collaborative environment with access to resources such as computational and storage systems, instruments, and software tools and services for the most computationally challenging applications.

Distributed Monte Carlo production for DZero

NASA Astrophysics Data System (ADS)

Snow, Joel; DØ Collaboration

2010-04-01

The DZero collaboration uses a variety of resources on four continents to pursue a strategy of flexibility and automation in the generation of simulation data. This strategy provides a resilient and opportunistic system which ensures an adequate and timely supply of simulation data to support DZero's physics analyses. A mixture of facilities, dedicated and opportunistic, specialized and generic, large and small, grid job enabled and not, are used to provide a production system that has adapted to newly developing technologies. This strategy has increased the event production rate by a factor of seven and the data production rate by a factor of ten in the last three years despite diminishing manpower. Common to all production facilities is the SAM (Sequential Access to Metadata) data-grid. Job submission to the grid uses SAMGrid middleware which may forward jobs to the OSG, the WLCG, or native SAMGrid sites. The distributed computing and data handling system used by DZero will be described and the results of MC production since the deployment of grid technologies will be presented.

Evaluation of a 3D point cloud tetrahedral tomographic reconstruction method

PubMed Central

Pereira, N F; Sitek, A

2011-01-01

Tomographic reconstruction on an irregular grid may be superior to reconstruction on a regular grid. This is achieved through an appropriate choice of the image space model, the selection of an optimal set of points and the use of any available prior information during the reconstruction process. Accordingly, a number of reconstruction-related parameters must be optimized for best performance. In this work, a 3D point cloud tetrahedral mesh reconstruction method is evaluated for quantitative tasks. A linear image model is employed to obtain the reconstruction system matrix and five point generation strategies are studied. The evaluation is performed using the recovery coefficient, as well as voxel- and template-based estimates of bias and variance measures, computed over specific regions in the reconstructed image. A similar analysis is performed for regular grid reconstructions that use voxel basis functions. The maximum likelihood expectation maximization reconstruction algorithm is used. For the tetrahedral reconstructions, of the five point generation methods that are evaluated, three use image priors. For evaluation purposes, an object consisting of overlapping spheres with varying activity is simulated. The exact parallel projection data of this object are obtained analytically using a parallel projector, and multiple Poisson noise realizations of these exact data are generated and reconstructed using the different point generation strategies. The unconstrained nature of point placement in some of the irregular mesh-based reconstruction strategies has superior activity recovery for small, low-contrast image regions. The results show that, with an appropriately generated set of mesh points, the irregular grid reconstruction methods can out-perform reconstructions on a regular grid for mathematical phantoms, in terms of the performance measures evaluated. PMID:20736496

Evaluation of a 3D point cloud tetrahedral tomographic reconstruction method

NASA Astrophysics Data System (ADS)

Pereira, N. F.; Sitek, A.

2010-09-01

Tomographic reconstruction on an irregular grid may be superior to reconstruction on a regular grid. This is achieved through an appropriate choice of the image space model, the selection of an optimal set of points and the use of any available prior information during the reconstruction process. Accordingly, a number of reconstruction-related parameters must be optimized for best performance. In this work, a 3D point cloud tetrahedral mesh reconstruction method is evaluated for quantitative tasks. A linear image model is employed to obtain the reconstruction system matrix and five point generation strategies are studied. The evaluation is performed using the recovery coefficient, as well as voxel- and template-based estimates of bias and variance measures, computed over specific regions in the reconstructed image. A similar analysis is performed for regular grid reconstructions that use voxel basis functions. The maximum likelihood expectation maximization reconstruction algorithm is used. For the tetrahedral reconstructions, of the five point generation methods that are evaluated, three use image priors. For evaluation purposes, an object consisting of overlapping spheres with varying activity is simulated. The exact parallel projection data of this object are obtained analytically using a parallel projector, and multiple Poisson noise realizations of these exact data are generated and reconstructed using the different point generation strategies. The unconstrained nature of point placement in some of the irregular mesh-based reconstruction strategies has superior activity recovery for small, low-contrast image regions. The results show that, with an appropriately generated set of mesh points, the irregular grid reconstruction methods can out-perform reconstructions on a regular grid for mathematical phantoms, in terms of the performance measures evaluated.

Development of Three-Dimensional DRAGON Grid Technology

NASA Technical Reports Server (NTRS)

Zheng, Yao; Kiou, Meng-Sing; Civinskas, Kestutis C.

1999-01-01

For a typical three dimensional flow in a practical engineering device, the time spent in grid generation can take 70 percent of the total analysis effort, resulting in a serious bottleneck in the design/analysis cycle. The present research attempts to develop a procedure that can considerably reduce the grid generation effort. The DRAGON grid, as a hybrid grid, is created by means of a Direct Replacement of Arbitrary Grid Overlapping by Nonstructured grid. The DRAGON grid scheme is an adaptation to the Chimera thinking. The Chimera grid is a composite structured grid, composing a set of overlapped structured grids, which are independently generated and body-fitted. The grid is of high quality and amenable for efficient solution schemes. However, the interpolation used in the overlapped region between grids introduces error, especially when a sharp-gradient region is encountered. The DRAGON grid scheme is capable of completely eliminating the interpolation and preserving the conservation property. It maximizes the advantages of the Chimera scheme and adapts the strengths of the unstructured and while at the same time keeping its weaknesses minimal. In the present paper, we describe the progress towards extending the DRAGON grid technology into three dimensions. Essential and programming aspects of the extension, and new challenges for the three-dimensional cases, are addressed.

Fast Reliability Assessing Method for Distribution Network with Distributed Renewable Energy Generation

NASA Astrophysics Data System (ADS)

Chen, Fan; Huang, Shaoxiong; Ding, Jinjin; Ding, Jinjin; Gao, Bo; Xie, Yuguang; Wang, Xiaoming

2018-01-01

This paper proposes a fast reliability assessing method for distribution grid with distributed renewable energy generation. First, the Weibull distribution and the Beta distribution are used to describe the probability distribution characteristics of wind speed and solar irradiance respectively, and the models of wind farm, solar park and local load are built for reliability assessment. Then based on power system production cost simulation probability discretization and linearization power flow, a optimal power flow objected with minimum cost of conventional power generation is to be resolved. Thus a reliability assessment for distribution grid is implemented fast and accurately. The Loss Of Load Probability (LOLP) and Expected Energy Not Supplied (EENS) are selected as the reliability index, a simulation for IEEE RBTS BUS6 system in MATLAB indicates that the fast reliability assessing method calculates the reliability index much faster with the accuracy ensured when compared with Monte Carlo method.

Experimental grid connected PV system power analysis

NASA Astrophysics Data System (ADS)

Semaoui, Smail; Abdeladim, Kamel; Arab, Amar Hadj; Boulahchich, Saliha; Amrouche, Said Ould; Yassaa, Noureddine

2018-05-01

Almost 80 % of Algerian territory is appropriate for the exploitation of solar energy. The Algerian energetic strategy provides a substantial injection of PV electricity to the national grid. Currently, about 344 MWp of PV arrays which corresponds approximately to 2,34 km2 of module surfaces, are connected on electricity grid over the national territory. The Algerian Northern regions are characterized by strong pollution and high humidity. These phenomena affect the energetic productivity of PV generator. The objective of our study is to analyze experimental grid connected PV system power in coastal locations. Hence, experiments have been conducted on three identical PV systems to determine the electrical performances. Transformer-less inverters are the most attractive for the ground-based photovoltaic (PV) system due to their efficiencies, reduced cost and weight. Besides, the absence of the galvanic isolation generates problems of capacitive leakage current on the AC side and the degradation of the insulation resistance on the DC side of the inverter. In this work, experimental study of the behavior of single-phase inverters without transformers is presented. The main objective of this work is to study the degradation of the insulation resistance at the input of the inverter, and the capacitive leakage current at the output of the inverter. This study was achieved at the CDER on a rainy day of 15/03/2017, on the first PV plant connected to the low voltage network in Algeria. This investigation can help forecasting the PV array energetic production by taking into account natural conditions.

Domain Decomposition By the Advancing-Partition Method

NASA Technical Reports Server (NTRS)

Pirzadeh, Shahyar Z.

2008-01-01

A new method of domain decomposition has been developed for generating unstructured grids in subdomains either sequentially or using multiple computers in parallel. Domain decomposition is a crucial and challenging step for parallel grid generation. Prior methods are generally based on auxiliary, complex, and computationally intensive operations for defining partition interfaces and usually produce grids of lower quality than those generated in single domains. The new technique, referred to as "Advancing Partition," is based on the Advancing-Front method, which partitions a domain as part of the volume mesh generation in a consistent and "natural" way. The benefits of this approach are: 1) the process of domain decomposition is highly automated, 2) partitioning of domain does not compromise the quality of the generated grids, and 3) the computational overhead for domain decomposition is minimal. The new method has been implemented in NASA's unstructured grid generation code VGRID.

Power Quality Improvement Utilizing Photovoltaic Generation Connected to a Weak Grid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muljadi, Eduard; Tumbelaka, Hanny H.; Gao, Wenzhong

Microgrid research and development in the past decades have been one of the most popular topics. Similarly, the photovoltaic generation has been surging among renewable generation in the past few years, thanks to the availability, affordability, technology maturity of the PV panels and the PV inverter in the general market. Unfortunately, quite often, the PV installations are connected to weak grids and may have been considered as the culprit of poor power quality affecting other loads in particular sensitive loads connected to the same point of common coupling (PCC). This paper is intended to demystify the renewable generation, and turnsmore » the negative perception into positive revelation of the superiority of PV generation to the power quality improvement in a microgrid system. The main objective of this work is to develop a control method for the PV inverter so that the power quality at the PCC will be improved under various disturbances. The method is to control the reactive current based on utilizing the grid current to counteract the negative impact of the disturbances. The proposed control method is verified in PSIM platform. Promising results have been obtained.« less

Deconvolution methods and systems for the mapping of acoustic sources from phased microphone arrays

NASA Technical Reports Server (NTRS)

Brooks, Thomas F. (Inventor); Humphreys, Jr., William M. (Inventor)

2010-01-01

A method and system for mapping acoustic sources determined from a phased microphone array. A plurality of microphones are arranged in an optimized grid pattern including a plurality of grid locations thereof. A linear configuration of N equations and N unknowns can be formed by accounting for a reciprocal influence of one or more beamforming characteristics thereof at varying grid locations among the plurality of grid locations. A full-rank equation derived from the linear configuration of N equations and N unknowns can then be iteratively determined. A full-rank can be attained by the solution requirement of the positivity constraint equivalent to the physical assumption of statically independent noise sources at each N location. An optimized noise source distribution is then generated over an identified aeroacoustic source region associated with the phased microphone array in order to compile an output presentation thereof, thereby removing the beamforming characteristics from the resulting output presentation.

Improved inertial control for permanent magnet synchronous generator wind turbine generators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Ziping; Gao, Wenzhong; Wang, Xiao

With increasing integrations of large-scale systems based on permanent magnet synchronous generator wind turbine generators (PMSG-WTGs), the overall inertial response of a power system will tend to deteriorate as a result of the decoupling of rotor speed and grid frequency through the power converter as well as the scheduled retirement of conventional synchronous generators. Thus, PMSG-WTGs can provide value to an electric grid by contributing to the system's inertial response through the inherent kinetic energy stored in their rotating masses and fast power converter control. In this study, an improved inertial control method based on the maximum power point trackingmore » operation curve is introduced to enhance the overall frequency support capability of PMSG-WTGs in the case of large supply-demand imbalances. Moreover, this method is implemented in the CART2-PMSG integrated model in MATLAB/Simulink to investigate its impact on the wind turbine's structural loads during the inertial response process. Simulation results indicate that the proposed method can effectively reduce the frequency nadir, arrest the rate of change of frequency, and alleviate the secondary frequency dip while imposing no negative impact on the major mechanical components of the wind turbine.« less

Chimera grids in the simulation of three-dimensional flowfields in turbine-blade-coolant passages

NASA Technical Reports Server (NTRS)

Stephens, M. A.; Rimlinger, M. J.; Shih, T. I.-P.; Civinskas, K. C.

1993-01-01

When computing flows inside geometrically complex turbine-blade coolant passages, the structure of the grid system used can affect significantly the overall time and cost required to obtain solutions. This paper addresses this issue while evaluating and developing computational tools for the design and analysis of coolant-passages, and is divided into two parts. In the first part, the various types of structured and unstructured grids are compared in relation to their ability to provide solutions in a timely and cost-effective manner. This comparison shows that the overlapping structured grids, known as Chimera grids, can rival and in some instances exceed the cost-effectiveness of unstructured grids in terms of both the man hours needed to generate grids and the amount of computer memory and CPU time needed to obtain solutions. In the second part, a computational tool utilizing Chimera grids was used to compute the flow and heat transfer in two different turbine-blade coolant passages that contain baffles and numerous pin fins. These computations showed the versatility and flexibility offered by Chimera grids.

The eGo grid model: An open source approach towards a model of German high and extra-high voltage power grids

NASA Astrophysics Data System (ADS)

Mueller, Ulf Philipp; Wienholt, Lukas; Kleinhans, David; Cussmann, Ilka; Bunke, Wolf-Dieter; Pleßmann, Guido; Wendiggensen, Jochen

2018-02-01

There are several power grid modelling approaches suitable for simulations in the field of power grid planning. The restrictive policies of grid operators, regulators and research institutes concerning their original data and models lead to an increased interest in open source approaches of grid models based on open data. By including all voltage levels between 60 kV (high voltage) and 380kV (extra high voltage), we dissolve the common distinction between transmission and distribution grid in energy system models and utilize a single, integrated model instead. An open data set for primarily Germany, which can be used for non-linear, linear and linear-optimal power flow methods, was developed. This data set consists of an electrically parameterised grid topology as well as allocated generation and demand characteristics for present and future scenarios at high spatial and temporal resolution. The usability of the grid model was demonstrated by the performance of exemplary power flow optimizations. Based on a marginal cost driven power plant dispatch, being subject to grid restrictions, congested power lines were identified. Continuous validation of the model is nescessary in order to reliably model storage and grid expansion in progressing research.

Methods for prismatic/tetrahedral grid generation and adaptation

NASA Technical Reports Server (NTRS)

Kallinderis, Y.

1995-01-01

The present work involves generation of hybrid prismatic/tetrahedral grids for complex 3-D geometries including multi-body domains. The prisms cover the region close to each body's surface, while tetrahedra are created elsewhere. Two developments are presented for hybrid grid generation around complex 3-D geometries. The first is a new octree/advancing front type of method for generation of the tetrahedra of the hybrid mesh. The main feature of the present advancing front tetrahedra generator that is different from previous such methods is that it does not require the creation of a background mesh by the user for the determination of the grid-spacing and stretching parameters. These are determined via an automatically generated octree. The second development is a method for treating the narrow gaps in between different bodies in a multiply-connected domain. This method is applied to a two-element wing case. A High Speed Civil Transport (HSCT) type of aircraft geometry is considered. The generated hybrid grid required only 170 K tetrahedra instead of an estimated two million had a tetrahedral mesh been used in the prisms region as well. A solution adaptive scheme for viscous computations on hybrid grids is also presented. A hybrid grid adaptation scheme that employs both h-refinement and redistribution strategies is developed to provide optimum meshes for viscous flow computations. Grid refinement is a dual adaptation scheme that couples 3-D, isotropic division of tetrahedra and 2-D, directional division of prisms.

Advanced Grid Control Technologies Workshop Series | Energy Systems

Science.gov Websites

on advanced distribution management systems (ADMS) and microgrid controls. The workshops were held at . July 7, 2015: Advanced Distribution Management Systems (ADMS) Welcome and NREL Overview Dr. Murali Keynote: Next-Generation Distribution Management Systems and Distributed Resource Energy Management