A Three-Port LLC Resonant DC/DC Converter

This paper proposes a new three-port LLC resonant converter which integrates input port, storage port, and load port in one converter. A pulse-frequency modulation and phaseshift combined control method are adopted for the proposed topology. It has four different operation modes with different gains and different power directions between input port, storage port, and load port, which are attractive for renewable energy with energy storage system applications. The proposed topology operates under resonant frequency, which is easy to implement with digital control, and it can achieve soft switching for almost all the switches and diodes similar to conventional LLC resonant converter. The performance of the proposed converter is validated by the experimental results from a 500-W prototype with 1.25-A maximum output current.