A single-stage bidirectional dual-active-bridge AC-DC converter based on enhancement mode GaN power transistor

This paper presents a high step-down ratio single-stage AC-DC converter based on GaN HEMT and dual-active-bridge (DAB) topology. The dual-phase-shift (DPS) modulation and variable-frequency (VF) modulation control strategy are adopted to realize zero voltage switching (ZVS) over wide input voltage range and load conditions. Compared with conventional two-stage AC-DC converter, the elimination of DC link capacitor, protective relay and single power conversion stage enables a high efficiency and higher power density solution for energy storage applications. In addition, ZVS range of both buck and boost mode is fully analyzed in this paper. A 240 V
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AC-48V DC, 80-250 kHz prototype was developed to verify the novel converter.