Research on efficiency of high power resonant electric vehicle contactless power transfer charger

Compared with traditional charging method, CPT (contactless power transfer) is more convenient and safe while having higher power lose. Therefore, the efficiency of CPT needs to be optimized. In this paper, PSSS (primary side series compensation and secondary side series compensation) model is used to study the efficiency optimization of a high-power CPT. The factors such as coil structure, resonant frequency, and load matching on high-power CPT charging equipment are studied by simulation and experiment. The results show that system efficiency is proportional to mutual inductance values; coil structure mainly affects the mutual inductance values; the mutual inductance of the coils is mainly affected by the diameter of the coils, the distance between the coils, the shape of coil, the number of turns, and so forth. As for the CPT charging system based on full-bridge inverter circuit, the efficiency of the system increases as the frequency increases in the range of 0-50 kHz, while decreases as the frequency is higher than 50 kHz. Load matching also affects the efficiency of high-power CPT charging equipment, and the load matching formula based on an equivalent circuit model is given.