New Single-Stage Soft-Switching Solid-State Transformer with Reduced Conduction Loss and Minimal Auxiliary Switch

This paper presents two new topologies of single-stage soft-switching solid-state transformer. The proposed converters achieve better trade-off than existing solutions between complexity and benefits from auxiliary circuits, which are used for soft switching and to address transformer leakage induced issues. Compared to the state-of-the-art, the proposed converters reduce conduction loss by approximately 20% via eliminating or moving the auxiliary diodes from the main power path. Moreover, the proposed converters achieve minimal auxiliary components by using only one auxiliary switch, i.e. >50% auxiliary counts reduction. In fact, the provision eliminates MV auxiliary switches, diodes, and a bulky MV resonant inductor due to impedance scaling law across transformers - significant improvement for MV-to-LV SST application. In addition, the proposed converters inherit the advantages of the soft-switching solid-state transformer, i.e. full load range ZVS capability and low EMI. As such, the proposed low-switch-count converters feature high efficiency, high power density, and low EMI noise. The topologies, design, and operating principles are presented and verified with experimental results at 600 V and 2 kV from two different prototypes.