Single-Stage Isolated Three-Phase SWISS AC–DC Converter Based on Dual Active Bridge Converters

This article proposes a single-stage three-phase ac–dc converter composed of a SWISS converter and two dual active bridge (DAB) converters connected in parallel at the output. The input current relationship between the SWISS and DAB converters is analyzed, and the optimal triple-phase-shift (TPS) control of the DAB converter is introduced to achieve the unity power factor for the entire load power. Under optimal TPS control, zero voltage switching and minimal current stress can be achieved. Based on the optimal working modes of TPS control, the analytical expression is derived to describe the relationship between the phase-shift angle and the input current of the DAB converter. A dual-loop control strategy is proposed to achieve good power quality and output regulation. The ranges of working modes and the control variables under different load power conditions are analyzed, demonstrating the adaptability of this strategy to a wide range of load powers. The design of the series inductor and the calculation of losses are discussed, and the loss distribution under different power conditions is presented. Finally, the proposed control strategy is applied to a 1.6 kW three-phase single-stage DAB-based SWISS converter with 200 V/50 Hz input line voltage and 200 V output voltage. The experimental results validate the feasibility and effectiveness of the control strategy.