The CLLC resonant converter has gained much attention in DC microgrid due to its bidirectional power transfer capability and high power density. When interlinking the DC-link bus and energy storage battery in DC microgrid, the CLLC converter needs to possess wide voltage regulation ability due to the wide battery voltage range in charging and discharging mode. To solve this issue, this paper presents a design methodology of bidirectional CLLC resonant converter based on the first harmonic approximation (FHA) model. Considering the voltage gain and zero-voltage-switching (ZVS) region, the design procedures are discussed in detail. Finally, a 10-kW SiC MOSFET based prototype converter was designed and built.  Experiment results verify the theoretical expectations and the maximum power conversion efficiency was 97.2%.

CLLC resonant converter; wide battery voltage range;design methodology;FHA model