Optimization of LCL resonant inverter in inductive power transfer systems based on high-order harmonics analysis

In this paper, a novel design method based on high-order harmonics analysis is proposed to help realize an efficient LCL resonant inverter in IPT systems. The newly derived method takes high-order harmonics into consideration to give accurate description for switching transient, which facilitates the implementation of both ZVS and optimal power factor. In the analysis, the optimal switching current is proposed to evaluate the inverter efficiency. A simplified circuit model is used to enable unifying the analysis of each harmonics component. The closed-form expressions of current at switching instant, as well as its relative error are given. According to preceding analysis, the optimal design method is implemented to achieve high efficiency for LCL resonant inverter. Experimental results show good agreement with analysis. The inverter efficiency is no less than 97% within full load range.