Design and experiment of a zero-voltage-switching module for bidirectional DC solid-state transformer

This paper presents design and experiment of a 20kW power conversion module applied in bidirectional DC solid-state transformer (SST). This module consists of a front-end full-bridge circuit with auxiliary soft-switching branch, and a LLC resonant converter serving as an isolated dc transformer. With the discussed modulation scheme, all power devices of the module feature zero-voltage-switching (ZVS) over full load range. Experiments are performed on the built setup, and the results show that for forward or backward power flow, this two stage SST module can achieve 98% efficiency at rated power.