ZVS Boundaries for NPC-Type Series Resonant Dual Active Bridge Converter Using Frequency Domain Analysis

In medium-voltage applications of DC-DC converters, the efficiency improvement relies on minimizing conduction and switching losses in their IGBTs. To achieve this, converters often operate under the zero voltage switching (ZVS) condition. However, precise determination of ZVS boundaries poses challenges for multi-level and resonant converters due to their complex operating conditions and the involvement of transcendental equations in current expression. This paper introduces a calculation method for the NPC-type series resonant dual active bridge (NPC-SRDAB) topology, utilizing a high-frequency link mathematical model. The proposed method enables accurate calculations in the frequency domain, encompassing all modulation conditions.