Accurate harmonic analysis of dual-frequency inverter considering dead-time effect

Wireless power transfer (WPT) systems or simultaneous wireless information and power transfer (SWIPT) systems support multiple charging frequency standards and usually transmit two or more frequencies simultaneously. Multi-frequency sinusoidal pulse width modulation (MF-SPWM) technology can output multiple sine wave frequencies at the same time with only one inverter, which effectively reduces the system size and improves compatibility. However, MF-SPWM and dead-time make the MF-inverter highly nonlinearized, with significant effects on the desired frequencies and the total harmonic distortion (THD) of the multi-frequency output. In this paper, a double Fourier series-based method of harmonic analysis for the dual-frequency inverter (DF-inverter) is proposed, which can accurately calculate the magnitude of each of the harmonics in the output of the DF-inverter taking into account the influence of dead-time. The calculation methods of the minimum pulse width and voltage THD of the DF-inverter are provided. An analysis shows that when the dead-time is less than the minimum pulse width, its influence is negligible. Meanwhile, when the dead-time is slightly larger than the minimum pulse width, there is a trade-off between the desired frequency component and the THD. Experimental results are given and they are consistent with the analytical results of the proposed method, and the error is within 2