A Hybrid modulation scheme for AC-AC Dual Active Bridge-based Solid-State Transformer

A hybrid modulation scheme for a Dual Active Bridge (DAB) based Solid-State Transformer (SST) is proposed in this paper. The topology consists of an input folding bridge, a DAB DC-DC converter with a half-bridge structure on the primary side, a full-bridge on the secondary side, and an output unfolding bridge. The conventional Phase-Shift Modulation (PSM) control technique exceeds the soft-switching boundary conditions under light load conditions and suffers from high current stress, which lowers the overall efficiency of the DAB-based SST converter. This article employs a hybrid modulation-based control strategy to overcome these limitations. Within this control strategy, an optimal control path for full power range is proposed, which extends the soft-switching range under light load conditions and lowers the current stress. Simulation results are provided to validate the effectiveness of the proposed control strategy.