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%.

无线功率传输（WPT）系统或同时无线信息和功率传输（SWIPT）系统支持多种充电频率标准，并且通常同时传输两个或多个频率。多频正弦脉宽调制（MF-SPWM）技术只需一台逆变器即可同时输出多个正弦波频率，有效减小系统体积，提高兼容性。然而，MF-SPWM 和死区时间使 MF 逆变器高度非线性化，对所需频率和多频输出的总谐波失真 (THD) 产生显着影响。本文提出了一种基于双傅里叶级数的双频逆变器（DF逆变器）谐波分析方法，该方法可以准确计算DF逆变器输出中各谐波的幅值，同时考虑到死区时间的影响。给出了DF逆变器最小脉宽和电压THD的计算方法。分析表明，当死区时间小于最小脉冲宽度时，其影响可以忽略不计。同时，当死区时间略大于最小脉冲宽度时，需要在所需频率分量和THD之间进行权衡。给出了实验结果，与该方法的分析结果一致，误差在2%以内。