Service Life of EV Batteries Used in Power Grid Frequency Regulation

EVs (electric vehicles) can be used as controllable loads and distributed storage devices. On the basis of power batteries, EVs can response to the power grid signals rapidly and accurately. They can provide ancillary services, such as peak shaving, frequency regulation services, etc. In this paper, the cycle life model of EV batteries is established based on four factors: ambient temperature, cycle-index, current and depth of charge/discharge. Besides, in consideration of battery safety, frequency control loop of EVs is obtained. According to simulation results, the stability of power grid can be improved a lot when EVs provide frequency regulation services with traditional generating units. Depending on load category and economical efficiency, frequency regulation is classified into primary, secondary and tertiary. Based on stability of power grid, capacity fade and electrical energy consumption of EV batteries, different strategies are investigated.