As the proportion of electric vehicles increases, interest in Vehicle to Grid (V2G) service is increasing. Many studies are underway to use V2G for peak shaving and frequency regulation in power system. However, V2G can shorten battery cycle life for electric vehicle (EV) which is the most variable part in EV. Hence battery cycle life should be considered in V2G service. As well as the number of discharges, depth of discharge (DOD) also highly affects battery cycle life. High depth of discharge reduces the cycle life of the EV battery exponentially. However, conventional droop control, which has been used for frequency regulation, controls the active power linearly without regard to the DOD. This paper proposes an optimal frequency regulation V2G control which considers the DOD of EV. Proposed method uniformly distributes the discharge for V2G. Therefore battery cycle life is preserved and inconvenience of EV owner from discharge is reduced. The case study result demonstrates the advantages of the proposed method over the conventional droop method. Battery cycle life of entire EV is preserved and energy consumption under V2G is uniformly distributed.
Implementation of battery management module for the microgrid: A case study