Efficiency-Oriented DPS Implementation in Morphed Three-Phase Three-Level DAB for Light-Load EV Charging

This work presents an efficiency-oriented modulation and morphing strategy for a three-phase three-level dual active bridge converter operating across both 800 V and 400 V electric vehicle battery systems. By reconfiguring the converter into a single-phase dual active bridge or a hybrid half-bridge/full-bridge structure at light-load, the proposed approach reduces current-invariant losses. A unified dual phase-shift framework is formulated to analytically model power flow and peak-current minimization across all three-level modulation variants, inner phase shift, duty-cycle control, and T-type zero-level modulation, demonstrating that all combinations produce equivalent voltage and current waveforms. Simulation efficiency maps are generated for all valid primary/secondary modulation pairs and indicate that inner and duty-cycle modulation achieve the highest efficiency across the full operating window. Hardware-in-the-loop experiments confirm stable three-phase-to-single-phase morphing and accurate power tracking between reference and measured power profiles for both voltage levels. The results validate that the proposed morphing strategy enables wide-range, auxiliary-free light-load operation suitable for next-generation EV charging architectures.