Power Quality Analysis at a Renewable Energy-Based Charging Station

This paper reports detailed in-situ measurements of electric vehicles charging at a renewable energy-based charging station. The electric vehicle is charged using alternating current level two electric vehicle supply equipment. The vehicle used in this study is model 2020 BMW i3 powered by lithium ion traction batteries. Measurements are carried out with a SEL-735 power quality meter, which records power quality index values. The main objective of this work is to expand the understanding the impact that electric vehicles have on these issues. Measurement results indicate that the power factor and total harmonic distortion exhibit time-dependent changes as the chargers progressed through the charging cycle. In fact, the %THD current increases from 2.06% to 8.47% as the EV charging rate decreases, whilst the voltage THD varies from 2.09% to 2.47% during the course of the charging process. Further, important oscillations in low-order harmonics such as the 3rd, 5th, 7th and 9th during the last part of the charging cycle related to the constant voltage mode have been observed. Regarding unbalance factors, the voltage imbalance varies from 0.33% to 0.65% and, therefore, it is well below the limit of 2% recommended in the IEEE Std. 1159-1995. The RMS voltage ramp changes observed during the combined operation of the EV charging station and the photovoltaic generator are below the 5% limit suggested in IEEE Std 1547 for interconnection of distributed energy resources.