A Solid State Transformer based Fast Charging Station for all Categories of Electric Vehicles

This paper proposes a power electronic architecture for DC level 3 fast charging station (FCS) that can charge three classes of EV batteries with different voltage and power levels. The proposed architecture based on a solid state transformer (SST) can be directly connected to a medium voltage grid hence eliminating the bulky line frequency transformer. Further, at the output side, several dual active bridges are paralleled to take care of the heavy charging current required for fast charging of the EV. In addition, battery storage and solar PV are integrated at each FC port to relieve the stress on the utility grid. The dynamic equations of the converters are derived and the controller architecture of the FCS is presented. Since the power in the three phases of the converter are different, a balancing scheme using zero sequence currents to equalize the power among the phases is described.

Index Terms—Solid state transformer, cascaded H bridge converter, dual active bridge converter, level 3 fast charging.