Optimized Modulation for Single-Stage Dual-Active-Bridge AC–DC Converter Under Wide Voltage Range

For the single-stage dual-active-bridge (DAB) ac−dc converter under wide voltage range, a multimode extended phase shift modulation strategy that considers voltage gain is proposed to address the limited soft-switching range and high peak leakage inductance current. In this article, first, the problem of large peak leakage inductance current under wide voltage range of secondary-side extended phase-shift modulation is analyzed, and then a multimode modulation considering voltage gain is proposed. Second, on this basis, the conditions for soft switching and power factor correction in each mode are analyzed, the mathematical expressions of phase shift ratio are derived, and then the seamless mode switching mechanism is explored. This modulation strategy can achieve full-range zero-voltage-switching (ZVS) and reduce the peak leakage inductance current to a certain extent. Finally, the effectiveness of the proposed modulation strategy is proved through simulation and experimental verification.