In-depth study of the application of solid-state transformer in design of high-power electric vehicle charging stations

Abstract

Solid-state transformers (SST) will play an important role in future electric power distribution. The SST usually used for traction and transportation systems. However, it can be employed for other applications. For example, electric vehicles (EVs) are confronting the increased demand now, and the service provider must expand the infrastructures such as the high-power EV charging stations in urban areas. One solution for designing a high-power charging station is the SST-based charging stations, which can be connected to the distribution network. This study proposes an SST-based EV charging station, which is connected to the 20 kV catenary without any low-frequency transformer and provides the necessary power for connected EVs without affecting the grid power quality. The proposed EV charging station has high flexibility such that it can be integrated with distributed generation. It also provides vehicle-to-grid, grid-to-vehicle and sun-to-vehicle features. Besides, it can inject reactive power to the grid based on its free capacity. This study also proposes an advance virtual flux predictive power controller to improve the immunity of this structure against voltage harmonics. Exact simulations have been done for a three-phase 20 kV/ 600 V/360 kVA station with different scenarios. Results verify the performance of this infrastructure.