A STATISTICAL-ANALYSIS OF THE EFFECT OF ELECTRIC VEHICLE-BATTERY CHARGING ON DISTRIBUTION-SYSTEM HARMONIC VOLTAGES

This paper presents a statistical method for predicting the effect tha t widespread electric vehicle (EV) battery charging will have on pou e r distribution system harmonic voltage levels. The method uses a stati stical model for nonlinear load currents to generate the probabilities of specific harmonic voltage levels. The statistical model for the ha rmonic currents produced by a concentration of EVs accounts for partia l harmonics cancellation introduced by uncertainty and variation in ch arger start-time and initial battery state-of-charge, A general soluti on technique: is presented along with several examples using data from a commercially-available EV charger and an actual power distribution system. Our results show that there is a definite threshold penetratio n below which EV charging has negligible impact on the number of buses whose voltage total harmonic distortion (THDv) exceeds 5%. During the late evening of a summer day, our example distribution system can acc ommodate EV penetration levels as high as 20%. A similar analysis of t he system in the spring or fall indicates that the system can accommod ate a 15% EV penetration before THDv exceeds 5% at an unacceptable num ber of buses.