Control Strategy and Modulation Scheme of Three-Phase Quasi-Single-Stage Isolated AC-DC Converter Based on Dual Active Bridge

This article proposes a three-phase quasi-single-stage isolated ac-dc converter, comprising a hybrid active third-harmonic injection buck-type rectifier (H3R) and a dual active bridge (DAB). Based on the input current analysis, globally optimal working modes of the DAB converter are derived through optimal triple-phase-shift (TPS) modulation, minimizing conduction losses while achieving wide-range zero-voltage switching (ZVS). A voltage-current closed-loop control strategy is proposed to regulate the output voltage and precisely control both the input current and third-harmonic injection current, achieving unity power factor (PF). This proposed approach eliminates the dc-link capacitor. By implementing the shared controller between the ac-dc and dc-dc stages, the quasi-single-stage topology simplifies control complexity while providing the PF correction and stable dc output voltage. Furthermore, the transformer and inductor parameters in the DAB converter are optimized through a genetic algorithm (GA) to minimize total loss, further improving the converter efficiency. Finally, a 1.6-kW experimental prototype with 200 V/50 Hz input line-to-line voltage and 200 V/250 V output voltage is built to validate the effectiveness and advantage of the proposed topology and control strategy.