Three-Phase Interleaved Bidirectional LLC Resonant Converter with Vertically Integrated Magnetics

Bidirectional LLC resonant converter is becoming widely applied in energy storage systems because of its high efficiency, high power density, and low EMI characteristics. To extend output power and reduce the output current ripple, the common approach is to parallel multiple-phase interleaved converter, which is proved to have higher efficiency and power density. This paper proposed a three-phase interleaved bidirectional LLC resonant converter with vertically integrated magnetics. Transformers and inductors are integrated by a shared magnetic plate to reduce the volume of magnetics. Flux cancellation in both forward and backward operation modes is achieved, resulting in smaller core loss and improved converter efficiency. The simplified reluctance model is presented, and the impact of zerosequence magnetic flux and current is analyzed. The optimal design of magnetics is presented, and a 500 kHz 400 V/ 52V 3.5 kW prototype is implemented, with peak efficiency of 98.44% and power density of 270 W/in(3).