Coupled Inductor-Based DC-DC Converter With Bipolar Self-Balancing Voltage and Full Load Range of ZVS

A bipolar dc distribution system is a promising solution for efficient and stable utilization of renewable energy, but it also faces the challenges of soft switching, bipolar voltage imbalance, etc. This article proposes a bipolar symmetric output topology based on a dual active bridge (DAB) converter. Unlike conventional DAB converters, this topology enables the self-balancing of the bipolar output voltage without additional components. Additionally, the number of magnetic components is reduced by integrating the leakage inductance, the magnetic inductance, and the transformer into one coupled inductor. Moreover, the control strategy based on extended phase shift is used to not only realize zero voltage switching (ZVS) over the full load range of the primary side switches but also achieve a low root-mean-square current of the leakage inductance. In addition, the parameter design for realizing ZVS under unbalanced load conditions is investigated to ensure that all switches are capable of ZVS operation over the full voltage and full load range. Finally, an experimental prototype is built to verify the operational performance of the proposed converter.