Load and mutual inductance estimation of wireless power transfer system for electric vehicles

Wireless power transfer (WPT) system has gathered attention for years with its safety, convenience and flexibility. Control of the whole system has always been a key issue for WPT technology. A lot of methods of parameter estimation have been presented in relevant literature, providing accordance for controlling. In this paper, an online parameter estimation method for WPT system is proposed based on the measurement of input voltage and current of the inverter. A DC input side model for the inverter was built, and the equivalent load of the inverter can be determined by the input voltage and current. Then, by studying the characteristics of the tangent of the reflected angle, a curve fitting method was proposed to estimate the system load. The mutual inductance of coils was also estimated to provide information of the system. The experiments results showed that the proposed method can reduce the estimating error of the load to 7%.