A Single-Stage DAB Backflow Power Optimization Strategy for Micro-Inverters

To address the issue of soft-switching loss commonly observed under conventional single-mode modulation schemes, this paper proposes a backflow power optimization control method for single-stage Dual Active Bridge (DAB) converters in photovoltaic (PV) micro-inverter systems. Based on the Extended Phase-Shift (EPS) modulation technique, the proposed method optimizes the internal phase-shift angle D1 and adjusts the phase- shift ratio k, thereby enabling soft-switching performance across the full grid phase range. The converter’s backflow power trajectory is optimized over the entire power range, and the magnitude of backflow power within each grid cycle is reanalyzed and recalculated for different power levels. A 600 W prototype was developed, and experimental results verify the effectiveness of the proposed optimization control method.