Power quality problems at electric vehicle's charging station

An area of electric vehicle (EV) racing which will require substantial study is the racetrack battery charging facility. During the 1993 third Annual APS Solar and Electric 500 race at Phoenix International Raceway (PIR) the generated current harmonics were monitored for various groups and types of battery chargers operating at the time. Measurements were taken on the low voltage side of the single phase supply transformer which supplied the charging station. Input current waveforms were recorded for 26 different chargers. The purpose of this paper is to show measurement results and statistically predict what the impact on the racetrack power system when large numbers of battery chargers are operated simultaneously. A statistical simulation was performed by adding randomly selected combinations of the digitized current waveforms which had been recorded at the racetrack charging facility. The THD was calculated for each iteration of the simulation. Measurements show that individual battery chargers generate distorted currents with THD in a range from 10% to 100%. Experimental measurement and simulations show that the total current generated by the simultaneous operation of several chargers is less distorted than individual charger currents. As the number of chargers increased there was a continual decrease in the THD of the combined currents.