Bidirectional Hybrid DC–DC Resonant Converter With Wide Voltage Gain Range

A bidirectional hybrid dc–dc resonant converter with a wide voltage gain range and three operating modes for both forward and backward operations is proposed. The converter features a symmetrical structure on both sides and can be configured as three variable structures: a full-bridge converter, a dual-phase half-bridge CLLC converter, and a single-phase half-bridge CLLC converter, to enhance efficiency under low-voltage and light-load conditions. No extra device is required, and the operating mode of the proposed converter can be switched through various modulation strategies. Additionally, integrating the resonant inductance into the transformer reduces the number of components, thereby increasing power density. During three distinct operational modes, zero-voltage switching can be achieved for all active switches, significantly reducing switching losses and enhancing the overall system efficiency. A 3.3-kW experimental prototype has been constructed. In forward operation, the primary side dc bus voltage is maintained at 400V, while the secondary side battery voltage can be adjusted within a range of 250–450 V, achieving wide-range voltage output regulation. In backward operation, the voltage across the battery terminals ranges from 250 to 450 V, enabling wide-range voltage input regulation. Based on the battery voltage level, the converter employs a traditional dual-active-bridge mode for lower voltages and a bidirectional CLLC resonant mode for higher voltages.