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POWER TAKE-OFF AND GRID SUPPORT IN HYBRID VEHICLES USING WOUND FIELD SYNCHRONOUS MACHINES
Title
POWER TAKE-OFF AND GRID SUPPORT IN HYBRID VEHICLES USING WOUND FIELD SYNCHRONOUS MACHINES
Creator
Dong, Weizhen
Date
2016, 2016-07
Description
Energy sectors are undergoing revolutionary changes. Due to environmental concerns and customer desires, a considerable increase of Electric...
Show moreEnergy sectors are undergoing revolutionary changes. Due to environmental concerns and customer desires, a considerable increase of Electric Vehicles (EVs) and Plug-in Hybrid Electric Vehicles (PHEVs) is expected. A technology of Vehicle to Grid (V2G) is emerging in the electric power industry. This technology provides connections between PHEVs and microgrids, and utilize PHEVs as distributed generators for grid support or as backup power sources. With the development of Electric Vehicles, wound field synchronous machines (WFSM) have been used and studied in EV traction motors and generators. For the application of EV technology, WFSMs have several advantages over permanent magnet synchronous machines (IPMSM) and induction machines (IM) including the complete control of the field excitation from the rotor side, higher system and machine efficiencies, and reduced cost due to the absence of rare earth permanent magnets. At the same time, WFSMs can work as generators to realize power take-off and microgrid support for EV tractions. Due to the several advantages of WFSMs in EVs application, this research focuses on the control of the WFSM in PHEVs for power take-off and grid support as a generator. PHEVs internal combustion (IC) engine is considered as a prime mover and would couple to the shaft which is connected to the WFSM. Such PHEVs applications would be used as power supplies for nearby loads and microgrids. This system is able to reduce cost of power electronics converters and directly provides desired AC voltage. This work aims to study the power take-off from hybrid electric vehicles using wound field synchronous machines and operation in microgrids. The feasible HEVs configurations to realize this purpose is studied. The modeling of IC engine, wound field synchronous machine, brushless exciter and distributed generators (DGs) in microgrid is demonstrated. One disadvantage of this application is the time delay during the combustion progress in the IC engine. This delay could affect the stability and dynamic response of the system. At the same time, the IC engine based generators have slower dynamic response compared with power electronic based sources. A state variable voltage regulator and a rotor speed controller are designed to improve the performance of the system. These controllers enable wound field synchronous machines provide desired voltage frequency and voltage magnitude. A real power - frequency droop controller and a reactive power – voltage droop controller are also studied. The droop controllers would keep the stability and better power quality of the system for islanded mode operation and grid-connected mode operation. The droop controllers enable EVs system share loads in a desire portion of power with other DGs in the grid and this reactive power – voltage droop controller would eliminate the circulating reactive power in the whole grid system. The EV’s isolated power take-off operation, islanded mode operation in microgrid with other DGs, and grid connected mode operation in microgrid are discussed. Stabilities, disturbance responses, and load sharing abilities are shown in simulation studies. The results are presented and discussed.
M.S. in Electrical Engineering, July 2016
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