Optimization and Modulation for Dual-Side Zero Backflow Power, Minimum Tank Current, and Wide-Range ZVS in a Wide-Voltage Gain Five-Level NPC-DAB Resonant Converter

The neutral-point-clamped (NPC) structures are useful for high-voltage and high-power applications. However, with conventional and unoptimized modulation schemes, NPC-based converters often suffer from high backflow power and low efficiency at wide voltage gains and light load levels. This paper proposes an optimized asymmetric-phase-shift modulation strategy, which can achieve complete elimination of the backflow power in transformer’s both sides, wide-range zero-voltage-switching (ZVS) for all switches, and near minimum effective current, in a five-level NPC dual-active-bridge resonant converter (5L-NPC-DABRC), thereby simultaneously reducing the switching and conduction power losses. Eventually, the proposed topology and its optimized modulation scheme are verified experimentally in a 600 W laboratory prototype, demonstrating excellent performance throughout the entire power range. By comparing with existing modulation strategies, the proposed method is able to achieve higher efficiencies at different power levels.