Research On Influence And Control Method Of EV Energy Storage To The Power System

With the widely application of vehicles, the demand for power energy is increasing. Now the problem of energy and environment has been a serious restriction to development of vehicles. The industry of electric vehicles (EVs) are flourishing because of the advantages of energy-saving and environmental protection. For the energy storage system of EVs, a topological device of charging and discharging is proposed, which is based on the three-phase PWM converter and bi-directional DC/DC converter. The model of lithium-ion batteries is setted up by PSCAD. Then strategies of charging and discharging are discussed. Next it is discussed that the influence of the batteries of EVs to power system and related control technologies while charging(the active rectifier) and discharging(V2G technology) to the influence of the power system and related control technologies. For the control strategy of the active rectifier while charging, the harm of general chargers to grid while charging is analyzed. In order to reduce harm to the electric power system in the process of charging, the control strategy of double closed loop is put forward. For the outer ring of voltage, the combination of repetitive control and PI control strategy is used, which can improve steady-state control accuracy. For the inner ring of power, the improved direct power control strategy is proposed. Then the basic principle and control characteristic of traditional six interval divisions is analyzed, based on which a control method with twelve interval divisions is proposed to improve the control cha racte ristics. The simulation model is built by PSCAD. For discharging (V2G technology), the control strategy is proposed which is based on a power and harmonic decoupling control method, the EVs can be as the energy storage unitswhen they are idle, achieving the functions of reactive power compensation and harmonic management, finally, the simulation and experiment are done to prove the conclusions by PSCAD and FPGA+DSP digital control system.