An Ultrafast and Wide-Safe-Range Start-Up Method of DAB Converters With Straightforward Frequency-Phase Closed-Loop Control

Fast and safe start-up is crucial for the dual-active-bridge (DAB) converters. Conventional closed-loop start-up controls fail to achieve theoretical maximum power output due to manually predefined phase-shift modes, limiting start-up speed and safe operational range. To address these issues, this letter proposes a novel variable frequency plus extended phase-shift (EPS) control. This approach enables ultrafast and wide-safe-range start-up of DAB converters by maximizing power-per-current-stress capability within safety limitations. In addition, sole EPS modulation is required in the proposed control, thus eliminating complex mode transitions and streamlining the start-up process. Experimental results indicate that the proposed control achieves a broader safe start-up range and improves start-up speed by up to 43% under voltage-match condition compared to the state-of-the-art methods.