Autonomous Frequency Regulation Using Battery Energy Storage Systems of EV Charging Station

Increasing penetration of replenished renewable energy sources (RES) to the power grid is inevitable and brings stability challenges to traditional electric power systems (EPS). One of them is the frequency fluctuation due to the high participation of RES in the EPS. To reduce the grid frequency deviation, in this paper, an autonomous frequency regulation (FR) controller is proposed using the power of battery energy storage systems (BESS) in electric vehicle charging stations (EVCS) while providing the charging service. A proportional-integral (PI) controller scheme with a contribution factor is used in the proposed FR controller. The contribution factor determines the maximum power from BESS used for the proposed FR. The required power for the FR is then used to generate the setpoint for the inner-loop current controller of the grid-connected inverter (GCI). An impedance-based stability analysis considering the PI current controller and PLL gains for the LCL-filtered GCI is conducted. For the performance evaluation, the proposed FR controller is demonstrated in the IEEE 14-bus power system in PSCAD simulation.