Bidirectional Resonant Converter With Interleaved Three <i>CLLC</i> Energy Transmission Rails for EV Charger

ABSTRACT This paper proposes a bidirectional resonant converter with three CLLC resonant tanks for energy transmission in electric vehicle (EV) charger applications. The converter inherits the advantages of higher power density and lower current ripple from conventional three‐phase interleaved structure. By analyzing the phase‐disabling modes of the conventional three‐phase CLLC converter and reconstructing the circuit, two improved operational modes are introduced to enhance converter performance: (1) a single‐phase half‐bridge mode to expand the voltage gain range and (2) a two‐phase full‐bridge mode to improve light‐load efficiency. Smooth transitions between adjacent operating modes can be achieved. A 3.3‐kW prototype was built to verify the converter's applicability, with the bus voltage fixed at 400 V during operation. In forward operation, the output voltage range was 140–500 V, achieving a maximum efficiency of 98%. In reverse operation, the input voltage range was 300–500 V, with a maximum efficiency of 98.1%.