A Comparison of Practical Electric Vehicle Charging Policies to Improve the Performance of Power Distribution Systems

Electric vehicles (EVs) lend a new paradigm to the transportation sector while introducing different challenges to the power distribution grid. The EV load presents an unbalanced, dynamic load, depending upon the number of charging EVs at any instant connected to the different phases, the type(s) of the EV(s) connected, the starting time(s) of the EV charging and the charging duration(s), all of which are random functions of time. Hence, it becomes difficult to analyze the impact of EV charging on the distribution networks. In this paper, the domestic EV charging effect of about 3000 EVs pertaining to more than 800 U. S. residents on a 240-bus real distribution grid situated in the Midwest U.S.A is investigated using well-known travel survey data from the National Household Travel Survey (NHTS). Multiple case studies are carried out on the 240-bus network vis-à-vis profiles of the network demand, bus voltages and system losses without and with EV charging. The distortion in the network daily load profile, the bus voltage profile and the network losses can be reduced by implementing practical SOC based EV charging policies. Three SOC based EV charging policies are suggested. The results validate the proposed EV charging guidelines.