Dual-frequency modulation based mutual inductance and load identification method for inductively coupled power transfer systems

In inductively coupled power transfer (ICPT) systems, the mutual inductance and load are the key parameters to realize high performance control, which is difficult to measure directly in rail transit. Thus, a method realizing mutual inductance and load identification using only the output voltage and current of a high-frequency inverter is proposed in this paper. Dual-frequency modulation, where one is the resonant frequency and the other is the non-resonant frequency, is used in the high-frequency inverter. Then the amplitudes and phases of the output voltage and current of the high-frequency inverter at the resonant frequency and the non-resonant frequency can be obtained based on the fast Fourier transform (FFT) method. The circuit is decomposed according to different frequencies. Then a mathematical model of the ICPT system is established. Therefore, the mutual inductance and load can be identified. Finally, the effectiveness of the proposed method is verified based on an ICPT prototype. Experimental results show that the identification errors of mutual inductance and load are less than 5%.