Impact of Level 2 EV Charging on Phase Unbalance in Distribution Networks

The rapid growth of single-phase EV charging can lead to significant time-varying phase unbalance in distribution grids. In this study, a distribution grid analysis is carried out on a planned Level 2 charger parking lot, located in the Simon Fraser University campus. Historical charging data from existing chargers at the university is used in order to estimate the phase unbalance produced by the new chargers over a 24-hour period. Two types of Level 2 chargers are considered for the new parking lot: a standard level 2 (L2) and a higher voltage level 2 charger with auto transformer (L2T). Both charger scenarios are seen to produce significant unbalanced currents which propagate to the substation and exceed recommended limits regularly throughout the day. This unbalance is seen to be significantly reduced and at times even eradicated by placing a power redistribution converter in the parking lot.