Current Harmonics, Voltage Distortion, and Powers Associated with Electric Vehicle Battery Chargers Distributed on the Residential Power System

Abstract

The harmonic performance of the networks of several types of electric vehicle (EV) battery chargers is documented. Cumulative effects at the substation level for random distributions of each of five different charger types are reported. Chargers with and without current- smoothing inductors and with and without controlled rectifiers for maintenance of constant current are included. Results are reported as magnitudes of expected harmonic current; active power; apparent, reactive, and distortive volt amperes; and power factor hour by hour over typical daily recharge cycles for the network of chargers. Results regarding comparisons among chargers demonstrate the desirability of including a current-smoothing inductor in the charging circuit and indicate that constant-current type chargers using controlled rectifiers generate significantly more harmonic current than the simple noncontrolled taper-current chargers. Typical third harmonic current values of 15 A per charger on the 120-V side and 20 A per phase on the 12.8-kV side for a network of chargers (at ten percent penetration of chargers into the residential distribution network) indicate the possibility for harmful effects to customer and utility equipment and for interference into communications circuits. The results reported here should be useful in both predicting harmful effects at various densities of EV chargers on the residential network and in designing chargers to minimize those effects. supported in part by the New England Electric System.