Multimode Three-Phase <i>CLLLC</i> Bidirectional Resonant Converter With Wide Output Voltage Range and Improved Light-Load Efficiency

This article propose a modified three-phase <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CLLLC</i> bidirectional resonant dc-dc converter with wide voltage range and improved light-load efficiency. The converter inherits the advantages of higher power density, lower current ripple, and bidirectional power flow from conventional three-phase <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CLLLC</i> structure. In addition, by employing the newly designed phase-shedding strategy, the converter adds three modes to support pre-charging and float-charging stages. These features enable the converter to cover all charging stages of the battery. A smooth transition between adjacent operating modes of the converter can be attained. To verify the effectiveness and applicability of the newly designed phase-shielding strategy, a 3.3 kW experimental prototype is built. In charging stage, the primary side dc bus voltage is maintained at 400 V, and the output voltage range is 150–480 V, with a maximum efficiency of up to 98%. Besides, the efficiency increases by about 1% at 30% load, 3% at 20% load, and 14% at 10% load compared to the three-phase interleaved mode. In discharging stage, the input voltage range is 300–480 V, with a maximum efficiency of up to 98.1%.