A Full-Power-Range Optimization Scheme Under Double-Side Asymmetrical Phase-Shift Modulation in DAB-Based Distributed Energy Storage System

For distributed energy storage systems, dual-active-bridge (DAB) is often employed as an interface among photovoltaic (PV) port, storage system, and load. Efficient DAB operation will be beneficial to energy conversion efficiency. Nevertheless, for conventional DAB modulation, many problems exist including that a wider soft-switching range is always accompanied by a high peak current. In order to overcome these problems, a double-side asymmetrical phase-shift modulation (DAPM) is proposed, which combines phase-shift modulation on the primary side and variable-duty modulation on the secondary side. Based on DAPM, a full-power-range optimization scheme is employed to reduce current stress and widen zero-voltage-switching (ZVS) range. Consequently, most DAPM modes can realize all semiconductors ZVS. ZVS ranges are widened dramatically with lower peak current and lower root-mean-square (rms) current. Within the entire power range, compared with conventional DAB modulations, DAPM modes can achieve the lowest rms current, lowest peak current, and widest ZVS ranges. Finally, a DAB-based prototype is established to verify the effectiveness of the proposed DAPM.