A Modulation Method of Series-Resonant Dual-Active Half-Bridge Converter for ZVS and Minimum RMS current

For a given voltage conversion ratio and reference output power, minimizing conduction and switching losses are essential to achieve high efficiency. This paper proposes a modulation method to minimize RMS current and achieve complete ZVS operation for all operation ranges of the series-resonant dual-active half-bridge converter. The proposed modulation scheme utilizes four control degrees of freedom (primary-duty, secondary-duty, phase shift, and switching frequency) to achieve high efficiency. The proposed modulation method is based on time-domain analysis, which provides accurate analysis results even when harmonic currents are induced by the deviation of switching frequency from the resonant frequency. Analysis of the proposed modulation method is given for step-up/down mode and bidirectional operation. And it shows that the proposed modulation method is advantageous in the operation of a high step-up or high step-down conversion ratio. The effectiveness of the proposed modulation method is verified through an experimental prototype of a series-resonant dual-active-half-bridge converter operating at over 150 kHz switching frequency.