The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform
Kim B Olsen - One of the best experts on this subject based on the ideXlab platform.
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accuracy of the explicit planar free surface boundary condition implemented in a fourth order staggered Grid velocity stress finite difference scheme
Bulletin of the Seismological Society of America, 2001Co-Authors: Ellen Gottschammer, Kim B OlsenAbstract:We compute the accuracy of two implementations of the explicit planar free-surface boundary condition for 3D fourth-order velocity-stress staggered-Grid finite differences, 1/2 Grid apart vertically, in a uniform half-space. Due to the stag- gered Grid, the closest distance between the free surface and some wave-field com- ponents for both implementations is 1/2-Grid spacing. Overall, the differences in accuracy of the two implementations are small. When compared to a reflectivity solution computed at the staggered positions closest to the surface, the total misfit for all three components of the wave field is generally found to be larger for the free surface colocated with the normal stresses, compared to that for the free surface colocated with the xz and yz stresses. However, this trend is reversed when compared to the reflectivity solution exactly at the free surface (the misfit encountered in staggered-Grid Modeling). When the wave field is averaged across the free surface, thereby centering thestaggered wave field exactly on the freesurface,thefree-surface condition colocated with the xz and yz stresses generates the smallest total misfit for increasing epicentral distance. For an epicentral distance/hypocentral depth of 10, the total misfit of this condition is about 15% smaller than that for the condition colocated with the normal stresses, mainly controlled by the misfit on the Rayleigh wave.
A Keyhani - One of the best experts on this subject based on the ideXlab platform.
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design of smart power Grid renewable energy systems
2011Co-Authors: A KeyhaniAbstract:FOREWORD. PREFACE. ACKNOWLEDGMENTS. 1 ENERGY AND CIVILIZATION. 1.1 Introduction. 1.2 Fossil Fuel. 1.3 Depletion of Energy Resources. 1.4 An Alternative Energy Source: Nuclear Energy. 1.5 Global Warming. 1.6 The Age of the Electric Power System. 1.7 Green and Renewable Energy Sources. 1.8 Energy Units and Conversions. 1.9 Estimating the Cost of Energy. 1.10 Conclusion. 2 POWER GridS. 2.1 Introduction. 2.2 Electric Power Grids. 2.3 The Basic Concepts of Power Grids. 2.4 Load Models. 2.5 Transformers in Electric Power Grids. 2.6 Modeling a MicroGrid System. 2.7 Modeling Three-Phase Transformers. 2.8 Tap Changing Transformers. 2.9 Modeling Transmission Lines. 3 Modeling CONVERTERS IN MICROGrid POWER SYSTEMS. 3.1 Introduction. 3.2 Single-Phase DC/AC Inverters with Two Switches. 3.3 Single-Phase DC/AC Inverters with a Four-Switch Bipolar Switching Method. 3.3.1 Pulse Width Modulation with Unipolar Voltage Switching for a Single-Phase Full-Bridge Inverter. 3.4 Three-Phase DC/AC Inverters. 3.5 Pulse Width Modulation Methods. 3.6 Analysis of DC/AC Three-Phase Inverters. 3.7 MicroGrid of Renewable Energy Systems. 3.8 The DC/DC Converters in Green Energy Systems. 3.9 Rectifiers. 3.10 Pulse Width Modulation Rectifiers. 3.11 A Three-Phase Voltage Source Rectifier Utilizing Sinusoidal PWM Switching. 3.12 The Sizing of an Inverter for MicroGrid Operation. 3.13 The Sizing of a Rectifi er for MicroGrid Operation. 3.14 The Sizing of DC/DC Converters for MicroGrid Operation. 4 SMART POWER Grid SYSTEMS. 4.1 Introduction. 4.2 Power Grid Operation. 4.3 The Vertically and Market-Structured Utility. 4.4 Power Grid Operations Control. 4.5 Load-Frequency Control. 4.6 Automatic Generation Control. 4.7 Operating Reserve Calculation. 4.8 The Basic Concepts of a Smart Power Grid. 4.9 The Load Factor. 4.10 A Cyber-Controlled Smart Grid. 4.11 Smart Grid Development. 4.12 Smart MicroGrid Renewable Green Energy Systems. 4.13 A Power Grid Steam Generator. 4.14 Power Grid Modeling. 5 MICROGrid SOLAR ENERGY SYSTEMS. 5.1 Introduction. 5.2 The Solar Energy Conversion Process: Thermal Power Plants. 5.3 Photovoltaic Power Conversion. 5.4 Photovoltaic Materials. 5.5 Photovoltaic Characteristics. 5.6 Photovoltaic Effi ciency. 5.7 The Design of Photovoltaic Systems. 5.8 The Modeling of a Photovoltaic Module. 5.9 The Measurement of Photovoltaic Performance. 5.10 The Maximum Power Point of a Photovoltaic Array. 5.11 A Battery Storage System. 5.12 A Storage System Based on a Single-Cell Battery. 5.13 The Energy Yield of a Photovoltaic Module and the Angle of Incidence. 5.14 The State of Photovoltaic Generation Technology. 5.15 The Estimation of Photovoltaic Module Model Parameters. 6 MICROGrid WIND ENERGY SYSTEMS. 6.1 Introduction. 6.2 Wind Power. 6.3 Wind Turbine Generators. 6.4 The Modeling of Induction Machines. 6.5 Power Flow Analysis of an Induction Machine. 6.6 The Operation of an Induction Generator. 6.7 Dynamic Performance. 6.8 The Doubly-Fed Induction Generator. 6.9 Brushless Doubly-Fed Induction Generator Systems. 6.10 Variable-Speed Permanent Magnet Generators. 6.11 A Variable-Speed Synchronous Generator. 6.12 A Variable-Speed Generator with a Converter Isolated from the Grid. 7 LOAD FLOW ANALYSIS OF POWER GridS AND MICROGridS. 7.1 Introduction. 7.2 Voltage Calculation in Power Grid Analysis. 7.3 The Power Flow Problem. 7.4 Load Flow Study as a Power System Engineering Tool. 7.5 Bus Types. 7.6 General Formulation of the Power Flow Problem. 7.7 The Bus Admittance Model. 7.8 The Bus Impedance Matrix Model. 7.9 Formulation of the Load Flow Problem. 7.10 The Gauss Seidel YBus Algorithm. 7.11 The Gauss Seidel ZBus Algorithm. 7.12 Comparison of the YBus and ZBus Power Flow Solution Methods. 7.13 The Synchronous and Asynchronous Operation of MicroGrids. 7.14 An Advanced Power Flow Solution Method: The Newton Raphson Algorithm. 7.15 The Fast Decoupled Load Flow Algorithm. 7.16 Analysis of a Power Flow Problem. 8 POWER Grid AND MICROGrid FAULT STUDIES. 8.1 Introduction. 8.2 Power Grid Fault Current Calculation. 8.3 Symmetrical Components. 8.4 Sequence Networks for Power Generators. 8.5 The Modeling of a Photovoltaic Generating Station. 8.6 Sequence Networks for Balanced Three-Phase Transmission Lines. 8.7 Ground Current Flow in Balanced Three-Phase Transformers. 8.8 Zero Sequence Network. 8.9 Fault Studies. APPENDIX A COMPLEX NUMBERS. APPENDIX B TRANSMISSION LINE AND DISTRIBUTION TYPICAL DATA. APPENDIX C ENERGY YIELD OF A PHOTOVOLTAIC MODULE AND ITS ANGLE OF INCIDENCE. APPENDIX D WIND POWER. INDEX.
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design of smart power Grid renewable energy systems
2011Co-Authors: A KeyhaniAbstract:FOREWORD. PREFACE. ACKNOWLEDGMENTS. 1 ENERGY AND CIVILIZATION. 1.1 Introduction. 1.2 Fossil Fuel. 1.3 Depletion of Energy Resources. 1.4 An Alternative Energy Source: Nuclear Energy. 1.5 Global Warming. 1.6 The Age of the Electric Power System. 1.7 Green and Renewable Energy Sources. 1.8 Energy Units and Conversions. 1.9 Estimating the Cost of Energy. 1.10 Conclusion. 2 POWER GridS. 2.1 Introduction. 2.2 Electric Power Grids. 2.3 The Basic Concepts of Power Grids. 2.4 Load Models. 2.5 Transformers in Electric Power Grids. 2.6 Modeling a MicroGrid System. 2.7 Modeling Three-Phase Transformers. 2.8 Tap Changing Transformers. 2.9 Modeling Transmission Lines. 3 Modeling CONVERTERS IN MICROGrid POWER SYSTEMS. 3.1 Introduction. 3.2 Single-Phase DC/AC Inverters with Two Switches. 3.3 Single-Phase DC/AC Inverters with a Four-Switch Bipolar Switching Method. 3.3.1 Pulse Width Modulation with Unipolar Voltage Switching for a Single-Phase Full-Bridge Inverter. 3.4 Three-Phase DC/AC Inverters. 3.5 Pulse Width Modulation Methods. 3.6 Analysis of DC/AC Three-Phase Inverters. 3.7 MicroGrid of Renewable Energy Systems. 3.8 The DC/DC Converters in Green Energy Systems. 3.9 Rectifiers. 3.10 Pulse Width Modulation Rectifiers. 3.11 A Three-Phase Voltage Source Rectifier Utilizing Sinusoidal PWM Switching. 3.12 The Sizing of an Inverter for MicroGrid Operation. 3.13 The Sizing of a Rectifi er for MicroGrid Operation. 3.14 The Sizing of DC/DC Converters for MicroGrid Operation. 4 SMART POWER Grid SYSTEMS. 4.1 Introduction. 4.2 Power Grid Operation. 4.3 The Vertically and Market-Structured Utility. 4.4 Power Grid Operations Control. 4.5 Load-Frequency Control. 4.6 Automatic Generation Control. 4.7 Operating Reserve Calculation. 4.8 The Basic Concepts of a Smart Power Grid. 4.9 The Load Factor. 4.10 A Cyber-Controlled Smart Grid. 4.11 Smart Grid Development. 4.12 Smart MicroGrid Renewable Green Energy Systems. 4.13 A Power Grid Steam Generator. 4.14 Power Grid Modeling. 5 MICROGrid SOLAR ENERGY SYSTEMS. 5.1 Introduction. 5.2 The Solar Energy Conversion Process: Thermal Power Plants. 5.3 Photovoltaic Power Conversion. 5.4 Photovoltaic Materials. 5.5 Photovoltaic Characteristics. 5.6 Photovoltaic Effi ciency. 5.7 The Design of Photovoltaic Systems. 5.8 The Modeling of a Photovoltaic Module. 5.9 The Measurement of Photovoltaic Performance. 5.10 The Maximum Power Point of a Photovoltaic Array. 5.11 A Battery Storage System. 5.12 A Storage System Based on a Single-Cell Battery. 5.13 The Energy Yield of a Photovoltaic Module and the Angle of Incidence. 5.14 The State of Photovoltaic Generation Technology. 5.15 The Estimation of Photovoltaic Module Model Parameters. 6 MICROGrid WIND ENERGY SYSTEMS. 6.1 Introduction. 6.2 Wind Power. 6.3 Wind Turbine Generators. 6.4 The Modeling of Induction Machines. 6.5 Power Flow Analysis of an Induction Machine. 6.6 The Operation of an Induction Generator. 6.7 Dynamic Performance. 6.8 The Doubly-Fed Induction Generator. 6.9 Brushless Doubly-Fed Induction Generator Systems. 6.10 Variable-Speed Permanent Magnet Generators. 6.11 A Variable-Speed Synchronous Generator. 6.12 A Variable-Speed Generator with a Converter Isolated from the Grid. 7 LOAD FLOW ANALYSIS OF POWER GridS AND MICROGridS. 7.1 Introduction. 7.2 Voltage Calculation in Power Grid Analysis. 7.3 The Power Flow Problem. 7.4 Load Flow Study as a Power System Engineering Tool. 7.5 Bus Types. 7.6 General Formulation of the Power Flow Problem. 7.7 The Bus Admittance Model. 7.8 The Bus Impedance Matrix Model. 7.9 Formulation of the Load Flow Problem. 7.10 The Gauss Seidel YBus Algorithm. 7.11 The Gauss Seidel ZBus Algorithm. 7.12 Comparison of the YBus and ZBus Power Flow Solution Methods. 7.13 The Synchronous and Asynchronous Operation of MicroGrids. 7.14 An Advanced Power Flow Solution Method: The Newton Raphson Algorithm. 7.15 The Fast Decoupled Load Flow Algorithm. 7.16 Analysis of a Power Flow Problem. 8 POWER Grid AND MICROGrid FAULT STUDIES. 8.1 Introduction. 8.2 Power Grid Fault Current Calculation. 8.3 Symmetrical Components. 8.4 Sequence Networks for Power Generators. 8.5 The Modeling of a Photovoltaic Generating Station. 8.6 Sequence Networks for Balanced Three-Phase Transmission Lines. 8.7 Ground Current Flow in Balanced Three-Phase Transformers. 8.8 Zero Sequence Network. 8.9 Fault Studies. APPENDIX A COMPLEX NUMBERS. APPENDIX B TRANSMISSION LINE AND DISTRIBUTION TYPICAL DATA. APPENDIX C ENERGY YIELD OF A PHOTOVOLTAIC MODULE AND ITS ANGLE OF INCIDENCE. APPENDIX D WIND POWER. INDEX.
Ellen Gottschammer - One of the best experts on this subject based on the ideXlab platform.
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accuracy of the explicit planar free surface boundary condition implemented in a fourth order staggered Grid velocity stress finite difference scheme
Bulletin of the Seismological Society of America, 2001Co-Authors: Ellen Gottschammer, Kim B OlsenAbstract:We compute the accuracy of two implementations of the explicit planar free-surface boundary condition for 3D fourth-order velocity-stress staggered-Grid finite differences, 1/2 Grid apart vertically, in a uniform half-space. Due to the stag- gered Grid, the closest distance between the free surface and some wave-field com- ponents for both implementations is 1/2-Grid spacing. Overall, the differences in accuracy of the two implementations are small. When compared to a reflectivity solution computed at the staggered positions closest to the surface, the total misfit for all three components of the wave field is generally found to be larger for the free surface colocated with the normal stresses, compared to that for the free surface colocated with the xz and yz stresses. However, this trend is reversed when compared to the reflectivity solution exactly at the free surface (the misfit encountered in staggered-Grid Modeling). When the wave field is averaged across the free surface, thereby centering thestaggered wave field exactly on the freesurface,thefree-surface condition colocated with the xz and yz stresses generates the smallest total misfit for increasing epicentral distance. For an epicentral distance/hypocentral depth of 10, the total misfit of this condition is about 15% smaller than that for the condition colocated with the normal stresses, mainly controlled by the misfit on the Rayleigh wave.
Cheon Bo Shim - One of the best experts on this subject based on the ideXlab platform.
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practical numerical reactor employing direct whole core neutron transport and subchannel thermal hydraulic solvers
Annals of Nuclear Energy, 2013Co-Authors: Yeon Sang Jung, Cheon Bo Shim, Chang Hyun Lim, Han Gyu JooAbstract:Abstract The development and verification of a practical numerical reactor formed by integrating a subchannel thermal/hydraulic solver into the nTRACER direct whole core transport code developed at Seoul National University are presented. In order to accomplish high-fidelity and practicality needed for the applications to routine design analyses of power reactors, the accuracy and the parallel computing efficiency of the direct whole core transport methods, which are characterized by the planar MOC solution based three-dimensional calculation method, the subgroup method for resonance treatment under non-uniform conditions and the Krylov subspace based depletion method, are improved and realistic Modeling features such as axial spacer Grid Modeling and burnup-dependent gap conductance are implemented. The accuracy of the nTRACER neutronics calculations is first verified by comparing its solution with the reference Monte Carlo solutions for a group of benchmark problems. Then the core follow calculation results of the practical numerical reactor for two pressurized water reactors are compared with the measured data such as the critical boron concentration and radial power distributions. From these performance examinations, it is demonstrated that accurate and detailed direct simulations of power reactors is practically realizable without any prior calculations or adjustments before the core calculation.
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practical numerical reactor employing direct whole core neutron transport and subchannel thermal hydraulic solvers
Annals of Nuclear Energy, 2013Co-Authors: Yeon Sang Jung, Cheon Bo ShimAbstract:Abstract The development and verification of a practical numerical reactor formed by integrating a subchannel thermal/hydraulic solver into the nTRACER direct whole core transport code developed at Seoul National University are presented. In order to accomplish high-fidelity and practicality needed for the applications to routine design analyses of power reactors, the accuracy and the parallel computing efficiency of the direct whole core transport methods, which are characterized by the planar MOC solution based three-dimensional calculation method, the subgroup method for resonance treatment under non-uniform conditions and the Krylov subspace based depletion method, are improved and realistic Modeling features such as axial spacer Grid Modeling and burnup-dependent gap conductance are implemented. The accuracy of the nTRACER neutronics calculations is first verified by comparing its solution with the reference Monte Carlo solutions for a group of benchmark problems. Then the core follow calculation results of the practical numerical reactor for two pressurized water reactors are compared with the measured data such as the critical boron concentration and radial power distributions. From these performance examinations, it is demonstrated that accurate and detailed direct simulations of power reactors is practically realizable without any prior calculations or adjustments before the core calculation.
Wenye Wang - One of the best experts on this subject based on the ideXlab platform.
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Wireless mesh network in smart Grid: Modeling and analysis for time critical communications
IEEE Transactions on Wireless Communications, 2013Co-Authors: Yi Xu, Wenye WangAbstract:Communication networks are an indispensable component in the smart Grid power systems by providing the essential information exchange functions among the electrical devices that are located distributively in the Grid. In particular, wireless networks will be deployed widely in the smart Grid for data collection and remote control purposes. In this paper, we model the smart Grid wireless networks and present the communication delay analysis in typical wireless network deployment scenarios in the Grid. As the time critical communications are coupled with the power system protections in the smart Grid, it is important to understand the delay performance of the smart Grid wireless networks. Our results provide the delay bounds that can help design satisfactory wireless networks to meet the demanding communication requirements in the smart Grid.
