Electric vehicle charging station microgrid providing unified power quality conditioner support to local power distribution networks

Abstract

Power grids will benefit when electric vehicle (EV) charging stations provide more services in addition to charging. This paper presents a new configuration of the unified power quality conditioner (UPQC) that uses a microgrid in an EV charging station. A double-layer direct current structure is used in the microgrid to connect EVs in parallel and restrain direct current voltage variations in the UPQC. Control of the UPQC is modified to address the charging of EVs by using power from the grid directly while compensating for power quality issues. Recommended control parameters for the UPQC are derived from small signal analysis. An equal time ratio discharging control for EVs is proposed when a charging station UPQC acts as an emergency power supply to compensate for power interruptions. The performance of the proposed system was analyzed through simulations. Results show that the proposed system can compensate for harmonics, voltage sag and swell, voltage unbalance, and voltage interruption while ensuring EV charging.