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 that widespread electric vehicle (EV) battery charging will have on power distribution system harmonic voltage levels. The method uses a statistical model for nonlinear load currents to generate the probabilities of specific harmonic voltage levels. The statistical model for the harmonic currents produced by a concentration of EVs accounts for partial harmonics cancellation introduced by uncertainty and variation in charger start-time and initial battery state-of-charge. A general solution technique is presented along with several examples using data from a commercially-available EV charger and an actual power distribution system. The results show that there is a definite threshold penetration below which EV charging has negligible impact on the number of buses whose voltage total harmonic distortion (THD_V) exceeds 5%. During the late evening of a summer day, the authors´ example distribution system can accommodate EV penetration levels as high as 20%. A similar analysis of the system in the spring or fail indicates that the system can accommodate a 15% EV penetration before THD_V exceeds 5% at an unacceptable number of buses