A Charging Strategy for Electric Vehicle Fast Charging Station to Mitigate Distribution Transformer Aging and Reduce Operation Cost

The uncoordinated charging of electric vehicles (EVs) leads to either distribution transformer overload and accelerated aging or requires asset upgrade to a larger transformer to accommodate the peak charging demand. The situation can be further exacerbated under very fast EV charging due to higher peak-to-average load ratio. This paper proposes a new charging management strategy for EV fast-charging stations to mitigate the transformer aging and reduce the operating cost. The proposed strategy uses EVs in the parking lot that do not need to be charged or slowly charged as energy storage (ES) to smooth out the fluctuating charging power from fast-charging EVs. Comparative case studies with and without the proposed strategy are performed on a PV-ES fast-charging station to verify the effectiveness of the proposed charging management method for operating cost reduction, transformer peak loading reduction, and transformer loss of life mitigation. With the proposed strategy, the peak transformer loading reduction and the operation cost saving can be as large as 47.4% and 35.2%.