Unified strategy for electric vehicles participate in voltage and frequency regulation with active power in city grid

Voltage and frequency are both significant index of city grid. Electric vehicles (EVs) have the potential to provide ancillary services for power grid since they are in stop state at most time during a day. This paper proposes a novel unified EV charging and discharging strategy by controlling active power to provide voltage and frequency regulation in city power grid. The objective of the strategy is to solve the voltage drop/rise and frequency fluctuation in city power grid with minimum influence on EV owners travelling demand. The available V2G regulation power is obtained according to the EV owners' transportation demand, initial and real-time battery SOC and departure time. In case of voltage and frequency deviation out of the limitation, the EVs can participate in correspondence regulation by fast adjustment of charging or discharging power within the limitation. Simulations on an urban distribution network and an urban power grid are presented for voltage regulation and frequency regulation, respectively. The results have demonstrated the effectiveness of the proposed strategy. It can be concluded from the results that EV can be scheduled to solve the city grid voltage drop/rise and frequency fluctuation with the proposed strategy.