An isolated bidirectional resonant converter for battery charging system with low double line frequency ripple in charging stage is implemented. An adaptive frequency modulation method with the input voltage ripple feed-forward (RFF) control is proposed for a full-bridge CLLC converter with SiC. By the voltage gain curves derived, then appropriate frequency variation for output voltage regulation is designed. The laboratory prototype with rated power 1.5 kW is built to verify the proposed method. The maximum efficiencies in the charging and discharging stage are 96.7% and 95.6%, respectively. Also, the double line frequency ripple voltage can be reduced by 70%.
