A Cascaded Bidirectional DC-DC Converter with Intermediate Capacitor Resonance
Li Fu1, Deng Honglei1, Zhang Guoju2, Pei Wei2, Deng Wei2
1. School of Electric Power South China University of Technology Guangzhou 510640 China; 2. Institute of Electrical Engineering Chinese Academy of Sciences Beijing 100190 China
Abstract：In order to meet the requirements of high efficiency, high power density and wide voltage regulation range of DC-DC converters for the interconnection between battery banks and DC bus in the distributed energy storage system, a cascaded bidirectional DC-DC converter with intermediate capacitor resonance is proposed. The proposed converter adopts a modified resonant dual active bridge (DAB) on the low-voltage side. Different from the conventional DAB, it uses the leakage inductance of the high-frequency transformer to resonate with the intermediate DC bus capacitor. The modified DAB runs in open-loop mode to operate at the highest efficiency point. On the low-voltage side, a conventional bidirectional Buck-Boost topology is used to extend the voltage regulation range of the cascaded converter. This proposed cascaded converter has the advantages of small intermediate DC bus capacitance, wide voltage regulation range, low control complexity, high efficiency, and high-power density. Firstly, the topology, operating principle and control strategy of the converter are analyzed. Secondly, the key state variables and voltage-gain expression are derived. Thirdly, the loss model of the converter is established, and the resonant parameters are designed accordingly. Finally, a prototype with rated power of 7.5kW is built with the power density of 1.15W/cm3 and the full load efficiency of 95.9%, which verifies the characteristics of the converter with high efficiency, high power density and wide voltage regulation range.
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2022, Vol. 37 
