Hybrid Duty Ratio Phase-Shift Modulation for a Si plus SiC Neutral-Point-Clamped Dual-Active-Bridge Converter

The neutral-point-clamped (NPC) dual-active-bridge (DAB) converter with hybrid semiconductors (Si and SiC devices) is a promising topology for high-power energy storage systems. The triple-phase-shift (TPS) modulation can achieve high efficiency with zero-voltage switching (ZVS) by adjusting three phase shift angles. However, when applied to hybrid DAB topologies, switching and conduction losses are too high. In this paper, a hybrid modulation method using duty ratio and phase-shift is proposed to improve the efficiency of the hybrid NPC DAB converter. The Si and SiC devices on the primary NPC bridges work under different duty ratios with staggered switching instants so that the Si devices do not suffer from the high turn-off current, and the SiC devices benefit from less conduction time. The neutral current path is used to take over the negative current which flows through SiC body diodes under TPS. Switching and conduction losses under the proposed hybrid TPS modulation are compared. A 2-kW hardware prototype is built to verify the proposed hybrid modulation.