EPE Association: EPE 2009 - Subtopic 15-1 - LS: 'Power Electronics for Power Systems (I)'

EPE 2009 - Subtopic 15-1 - LS: 'Power Electronics for Power Systems (I)'
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2009 - Conference > EPE 2009 - Topic 15: 'Transmission and Distribution of Electrical Energy' > EPE 2009 - Subtopic 15-1 - LS: 'Power Electronics for Power Systems (I)'

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   Estimation of the Power and Energy Requirements for Trackside Energy Storage Systems
By Linards GRIGANS, Leonards LATKOVSKIS [View]
[Download]

Abstract: A trackside energy storage system installed at a DC tram-trolleybus substation is considered from the standpoint of its ability to capture the braking energy of electric vehicles. The dependence of energy savings on the power capability and energy capacity of such a system is studied. For this purpose a method of stochastic modeling is applied. It uses diagrams of experimentally recorded power of vehicles running within the feeding zone of the substation. The method is verified by applying probabilistic approach that uses the power probability density functions obtained from the same power diagrams. The modeling was performed for one substation feeding tram line in the Riga city. Results of this work allow finding the optimum between energy storage system parameters and recovered braking energy at given conditions. The proposed method can be applied for energy storage system sizing not only for current situation, but also for future taking into account growth of transport fleet and changes in transport organization.

   Wind Turbine-Energy Storage Control System for Delivering Constant Demand Power Shared by DFIGs through Droop Characteristics
By Meghdad FAZELI, Greg ASHER, Christian KLUMPNER, Serhiy BOZHKO, Liangzhong YAO, Masoud BAZARGAN [View]
[Download]

Abstract: This paper investigates embedding Energy Storage (ES) with multiple wind turbines in order to deliver to the grid a smooth and constant power as demanded by the system operator. The demand power is shared by DFIGs proportional to their ratings utilizing classical voltage and frequency droop characteristics. The paper addresses the system control methodologies for delivering constant power to the grid whilst also ensuring good system stability and good utilization of the inherent inertial energy storage capacity of the turbine. A wind farm consisting of DFIG generators feeding an HVDC link is chosen for illustration, but the methods can be applied to many technologies. The simulations, which are done by PSCAD/EMTDC, demonstrate that the total power delivered by the wind farm is constant and equal to the total demand power while each DFIG-ES delivers a constant power proportional to its rating determined by droop characteristics. The calculation of the size of ES (power and energy) for a deterministic wind statistics is beyond the scope of this paper and will be explained in a future paper.

   Design Considerations for SMES Systems Applied to HVDC Links
By Shinichi NOMURA, Norihiro TANAKA, Kenji TSUBOI, Hiroaki TSUTSUI, Shunji TSUJI-IIO, Ryuichi SHIMADA [View]
[Download]

Abstract: The objective of this work is to discuss the concept of HVDC link with superconducting magnetic energy storage (SMES). The SMES will be one of the candidates as a power storage system for load leveling and power stabilization. Using superconducting coils instead of DC reactors, the SMES can be incorporated into the HVDC link. However, in large-scale SMES, the superconducting coils require special considerations for induced electromagnetic forces to limit allowable tensile stresses. To overcome this problem, the authors developed the concept of the force-balanced coil (FBC) which is a helically wound coil, and can significantly reduce the required mass of the structure for the same magnetic energy compared with the conventional coil configurations. In order to demonstrate the feasibility of the FBC concept, the authors have developed a superconducting model coil using NbTi/Cu composite strands. The hand-made windings of the model coil were neither impregnated with epoxy resin nor reinforced with stainless steel wires. From the results of the excitation tests with liquid helium cooling, the model coil was successfully excited up to 6.1 T, corresponding to 86\% of the theoretical limit of the superconductivity. Based on achievement and status of large superconducting coils for high energy physics and nuclear fusion, a road map of large-scale SMES is developed. From the results, it is expected that the first 1 GWh class SMES system for daily load leveling will be installed in the period of 2030-40. However, in the case of HVDC links, the design condition of the SMES system involves many technical challenges from the view point of the superconducting engineering. For instance, the coil current is ordinary selected to at least over 10 kA due to the coil protection. On the other hand, the rated voltage of the HVDC will be over 100 kV, and the direct current is only about 1 kA. As a further step of this work, the power conversion system and the insulation method for SMES should be optimized.

EPE 2009 - Subtopic 15-1 - LS: 'Power Electronics for Power Systems (I)'
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2009 - Conference > EPE 2009 - Topic 15: 'Transmission and Distribution of Electrical Energy' > EPE 2009 - Subtopic 15-1 - LS: 'Power Electronics for Power Systems (I)'
	[return to parent folder]

	Estimation of the Power and Energy Requirements for Trackside Energy Storage Systems By Linards GRIGANS, Leonards LATKOVSKIS	[View] [Download]
Abstract: A trackside energy storage system installed at a DC tram-trolleybus substation is considered from the standpoint of its ability to capture the braking energy of electric vehicles. The dependence of energy savings on the power capability and energy capacity of such a system is studied. For this purpose a method of stochastic modeling is applied. It uses diagrams of experimentally recorded power of vehicles running within the feeding zone of the substation. The method is verified by applying probabilistic approach that uses the power probability density functions obtained from the same power diagrams. The modeling was performed for one substation feeding tram line in the Riga city. Results of this work allow finding the optimum between energy storage system parameters and recovered braking energy at given conditions. The proposed method can be applied for energy storage system sizing not only for current situation, but also for future taking into account growth of transport fleet and changes in transport organization.

	Wind Turbine-Energy Storage Control System for Delivering Constant Demand Power Shared by DFIGs through Droop Characteristics By Meghdad FAZELI, Greg ASHER, Christian KLUMPNER, Serhiy BOZHKO, Liangzhong YAO, Masoud BAZARGAN	[View] [Download]
Abstract: This paper investigates embedding Energy Storage (ES) with multiple wind turbines in order to deliver to the grid a smooth and constant power as demanded by the system operator. The demand power is shared by DFIGs proportional to their ratings utilizing classical voltage and frequency droop characteristics. The paper addresses the system control methodologies for delivering constant power to the grid whilst also ensuring good system stability and good utilization of the inherent inertial energy storage capacity of the turbine. A wind farm consisting of DFIG generators feeding an HVDC link is chosen for illustration, but the methods can be applied to many technologies. The simulations, which are done by PSCAD/EMTDC, demonstrate that the total power delivered by the wind farm is constant and equal to the total demand power while each DFIG-ES delivers a constant power proportional to its rating determined by droop characteristics. The calculation of the size of ES (power and energy) for a deterministic wind statistics is beyond the scope of this paper and will be explained in a future paper.

	Design Considerations for SMES Systems Applied to HVDC Links By Shinichi NOMURA, Norihiro TANAKA, Kenji TSUBOI, Hiroaki TSUTSUI, Shunji TSUJI-IIO, Ryuichi SHIMADA	[View] [Download]
Abstract: The objective of this work is to discuss the concept of HVDC link with superconducting magnetic energy storage (SMES). The SMES will be one of the candidates as a power storage system for load leveling and power stabilization. Using superconducting coils instead of DC reactors, the SMES can be incorporated into the HVDC link. However, in large-scale SMES, the superconducting coils require special considerations for induced electromagnetic forces to limit allowable tensile stresses. To overcome this problem, the authors developed the concept of the force-balanced coil (FBC) which is a helically wound coil, and can significantly reduce the required mass of the structure for the same magnetic energy compared with the conventional coil configurations. In order to demonstrate the feasibility of the FBC concept, the authors have developed a superconducting model coil using NbTi/Cu composite strands. The hand-made windings of the model coil were neither impregnated with epoxy resin nor reinforced with stainless steel wires. From the results of the excitation tests with liquid helium cooling, the model coil was successfully excited up to 6.1 T, corresponding to 86\% of the theoretical limit of the superconductivity. Based on achievement and status of large superconducting coils for high energy physics and nuclear fusion, a road map of large-scale SMES is developed. From the results, it is expected that the first 1 GWh class SMES system for daily load leveling will be installed in the period of 2030-40. However, in the case of HVDC links, the design condition of the SMES system involves many technical challenges from the view point of the superconducting engineering. For instance, the coil current is ordinary selected to at least over 10 kA due to the coil protection. On the other hand, the rated voltage of the HVDC will be over 100 kV, and the direct current is only about 1 kA. As a further step of this work, the power conversion system and the insulation method for SMES should be optimized.