Multi-mode control of three-phase LLC resonant converter based on planar integrated magnetic core

With the rapid development of electric vehicles, there is an increasing demand for charging station improvements in terms of charging speed, compatibility with various vehicle models, and cost-effectiveness. The three-phase LLC resonant converter has become a widely used topology in charging stations due to its high-power capacity, high efficiency, low input/output current ripple, and automatic current-sharing characteristics. However, the large number and bulky size of the magnetic components in this converter limit further improvements in system power density. With the rapid advancement of wide-bandgap semiconductor devices, the application of high switching frequencies has created new opportunities for magnetic integration technology based on planar PCB windings. This paper proposes a magnetic integration design method for the three-phase LLC resonant converter, which integrates three resonant inductors and three transformers into a planar magnetic core, which significantly improves the power density of the system. In addition, to meet the demand for a wide output voltage range in charging stations, a multi-mode control strategy is proposed. This strategy enables the converter to flexibly switch between the three-phase mode, the full-bridge mode, the phase-shift mode, and the half-bridge mode, achieving wide-range output regulation without modifying the topology. Finally, a SiC-based prototype device with a rated output power of 3 kW, an output voltage range of 90–240 V, and an operating frequency of 300 kHz was designed and developed. Experimental results show that the designed three-phase magnetic integrated transformer reduces the loss by about 45.57% compared with traditional discrete components. In addition, the converter realizes soft switching of the switching devices in the full load range, where the highest efficiency is 96.3%.