Voltage-regulatable Resonant Zero-voltage Zero-current Switching Converter with Auxiliary Transformer

To overcome the difficulty of voltage regulation of the LLC resonant converter in the high-power application scenarios of DC distribution network, such as renewable energy sources, energy storage, data center, power electronic transformer, this paper proposes a voltage-regulatable resonant zero-voltage zero-current switching (ZVZCS) converter with an auxiliary transformer. The auxiliary transformer and auxiliary half bridge are added in the proposed converter based on the traditional LLC resonant converter. The duration that the auxiliary transformer participates in the boost can be adjusted by changing the phase-shifting angle between the auxiliary half bridge and the primary-side full bridge. Thus, the voltage regulation function is realized on the premise of ensuring the soft switching of the main switch, and the auxiliary switches can realize zero-voltage turn-on. The circuit structure, working principle and parameter design process of the converter are described in detail. The principle of the proposed topology and the correctness of the parameter design are verified through a 100 kW converter simulation model. The simulation results show that the proposed converter has better efficiency in the high-power scenario than the traditional LLC resonant converter. Finally, a 2.5 kW experimental prototype is built to verify the effectiveness of the proposed topology. © 2022 Automation of Electric Power Systems Press.