Analysis and Design of LCCL Resonant Converter Based on Time-Domain Model for Bidirectional Onboard Charger Applications

A novel bidirectional LCCL resonant dc-dc converter is proposed in this article. By substituting the magnetizing inductance of CLLC with a parallel resonant capacitor, the LCCL resonant converter obtains enhanced voltage gain regulation capability compared to CLLC while maintaining zero-voltage switching (ZVS) for the inverting side and zero-current switching for the rectifier side during bidirectional power flow. The state of the isolated bidirectional dc-dc converters is thoroughly reviewed in this article. The operating principle and gain characteristic of LCCL under bidirectional power flow are explored in detail adopting time-domain model, which effectively overcomes the drawback of the lower accuracy of the first harmonic approximation in wide voltage range applications and guarantees the achievement of ZVS in time-domain accuracy. A parameters optimization method of LCCL is provided to address the wide voltage range of battery applications, which is capable of achieving the required bidirectional voltage gain and ZVS operation over the designed frequency range under the desired load conditions while minimizing reactive power. Finally, a laboratory prototype rated at 1 kW is developed to convert between 400 and 250-450 V bidirectional. The experimental results confirm the feasibility of the proposed LCCL topology and the validity of the corresponding parameters optimization method.