A novel ZVS and ZCS three-port LLC resonant converter for renewable energy systems

A novel three-port LLC resonant converter is proposed in this paper, which interfaces the clean energy resources like photovoltaic generation, wind power and fuel cell system with the energy storage system like battery. The switching frequency of the proposed topology is constant and equal to the resonant frequency, so zero voltage switching (ZVS) is achieved in the transformer primary side and zero current switching (ZCS) is achieved in the secondary side, which contributes to high conversion efficiency. The battery port of the converter is bidirectional operated to balance the load requirements and energy supplied by the source. The direction of charging/discharging current flowing through the battery in a switching cycle doesn´t change, so the current ripple of battery is relatively low, which helps to extend the lifetime of the battery.