Reducing the Impact of Plug-in Electric Vehicles on Distribution Transformers

There is a growing interest in electric transportation and the number of plug-in electric vehicles (EV) is increasing. This will have adverse impact on the power network assets including the distribution transformers which are not primarily designed for excessive loading levels. In this paper, a simple reactive power compensation method to reduce the impact of EV charging on distribution transformers is proposed and analyzed. The method is based on providing a component of residential reactive power demand by operating EV chargers at non-unity power factors thus reducing overall transformer currents. Three scenarios for reactive power compensation are discussed. The feasibility of the proposed method is demonstrated in a 53-node radial distribution system. The transformer overloading regions are divided into different severity zones. With the proposed method, the complete elimination of the most severe zone is achieved in almost all cases along with a significant reduction in other zones.