Hybrid modulation strategy for minimizing backflow power under dual phase shift modulation

The dual active bridge (DAB) converter is essential for direct current (DC) microgrids, providing galvanic isolation, high power density, and bidirectional power transfer. However, under voltage-mismatch conditions, single-phase-shift (SPS) modulation induces significant backflow power, reducing the converter’s efficiency. While optimization based on Karush–Kuhn–Tucker (KKT) conditions provides quick analytical solutions and effectively reduces backflow power, applying it directly to dual-phase-shift (DPS) modulation creates a power-vacancy region, which hinders global optimization across the entire power range. This paper proposes a novel hybrid modulation strategy for DAB converters, achieving full-range backflow power minimization. This method integrates KKT condition analysis with optimal path planning via a two-dimensional power-transfer plot under DPS modulation, thus identifying optimal paths in the power-vacancy region to achieve minimal backflow power. In the low-power range, the proposed minimum-backflow-power control reduces backflow power by 96.03%, 94.79%, and 95.68% compared to SPS, traditional DPS (TDPS), and derivative-based DPS (DDPS) modulation methods, respectively. Experimental results confirm the method’s effectiveness in minimizing backflow power across the entire power range. • Minimum backflow power is maintained throughout the entire operating range. • Proposed modulation eliminates the power-vacancy region. • Rigorous comparison using mathematical formulation. • rototype demonstrates improved performance metrics.