A novel approach for evaluating the impact of electric vehicles on the power distribution system

This paper presents a useful and practical approach for assessing the impact of electric vehicles on the electric power distribution system while keeping to a manageable volume of detailed circuit and equipment studies. This paper addresses electric vehicles as an electric load only and does not consider the potential of the vehicle being a generation source. It also only addresses the substation, primary and distribution transformer impacts. It does not consider impacts on the secondary system. The method uses a statistical clustering algorithm to identify a set of representative feeders for the electric utility system, each representing a certain subset of the utility feeder system. This set of representative feeders is analyzed over a series of electric vehicle market penetration scenarios from 0 to 100%, in order to determine the expected impacts on loading, losses, voltage and reliability performance and power quality that each feeder will see. Then, distribution system capacity upgrades that are required to serve uncontrolled EV loads in each area, as well as the benefits that could if EV loads were limited or re-scheduled via demand response are assessed for each. Results from these representative feeder scenario studies are then used to estimate the impacts, control and mitigation needed, and performance expected across the entire utility feeder set. This method has been used to plan for increasing amounts of electric vehicle loads on several utility systems in the USA. Results from one case study are discussed.