Active Power Control Of Grid-Integrated Electric Vehicles In A Power System With Wind Penetration

Integrated wind turbine generators into grid have brought challenges to the power grid operation, at the same time, integrated electric vehicles were both the random loads and the moving energy storage element, whose charging and discharging behaviors also will make a great impact on the grid operation. If the electric vehicles energy storage system and wind power could be scheduled collaboratively and the energy storages’charging and discharging were controlled reasonably, not only the adverse effects of both electric vehicles and wind power could be eliminated, but also the energy storage could participate into the grid frequency regulation. This paper focuses on the studies of electric vehicle’s charging and discharging modeling and the calculations of its reference charge-discharge power in order to stabilize the fluctuation of wind power and participate in the grid active power/frequency regulation.Firstly, the grid frequency dynamic characteristics were analyzed, when wind turbines and synchronous machines were respectively integrated into grid. The effects on the grid frequency were studied based on an actual grid and with the planned wind farms integrated, in the case that the wind farms suffer the disturbances of gust wind, ramp wind and noise wind and that there were line faults for the integrated wind farms. Subsequently, the models of electric vehicle’s charging and discharging were established, applying constant current constant voltage mode for charging and constant current mode for discharging. At the charging phase, a novel charging control strategy which uses current loop control in the current constant stage and switches automatically to voltage and current closed loop controls in the voltage constant stage was introduced. Electric vehicles require the harmoniously control in order to produce large-scale affects, hence, an electric vehicles equivalent method was adopted, which uses a single equivalent parameters vehicles to replace several cars integrated into the grid simultaneously. The charging and discharging power calculation for the sake of participating in the grid active power/frequency regulation was studied.The automatically switch of charging and discharging was controlled by the required charging and discharging power of electric vehicles. The grid equivalent system included electric vehicles and wind power was established in Matlab/Simulink and the effectiveness that electric vehicles participate in power system frequency control was analyzed. The simulation results demonstrate that electric vehicles energy storage system can reduce the system frequency deviation.