Efficiency improvement of three-phase LLC resonant converter using phase shedding

One main advantage of three-phase LLC converters for high power applications is their full-load efficiency. However, issues with light load operation (i.e. low efficiency) requires investigation. In this paper, a new modulation strategy is proposed to improve the light load efficiency of three-phase LLC converters to achieve a better efficiency curve. The proposed strategy uses two different modulation techniques for the three-phase LLC converter: three phase and two phase modulations. Through these two operating modes, phase shedding for the three-phase LLC resonant converter is achieved. In order to validate the theoretical analysis, experimental results of a 3kW three-phase LLC resonant converter are provided. The results show light-load efficiency improvements of up to 2%.