Medium-Voltage Single-Stage Solid-State Transformer Based Fast Charger for Electric Vehicles

This paper presents a medium-voltage single-stage solid-state transformer (SST) based fast charger architecture for electric vehicles. The proposed topology employs cascaded full-bridge converters on the medium-voltage side and paralleled full-bridge converters on the low-voltage side to establish a DC bus. Galvanic isolation and voltage transformation are achieved through a high-frequency transformer that decouples the high-voltage and low-voltage domains. An LC filter comprising a series-connected inductor and capacitor is incorporated to attenuate low-frequency harmonic components generated by the medium-voltage-side full-bridge converters. This configuration enables single-stage power conversion from medium voltage to low voltage, significantly reducing the power semiconductor device count compared to conventional multi-stage approaches. The control strategy is distributed across both sides: the medium-voltage-side cascaded full-bridge converters handle power factor correction for grid-side compliance, while the low-voltage-side full-bridge converters manage output voltage regulation and sub-module capacitor voltage balancing. Comprehensive simulation studies validate the operational effectiveness and performance characteristics of the proposed topology.