Improved random PWM modulation method based on preset carrier switching frequency

To solve the problem of harmonic distortion generated by the output AC of inverters without considering the relationship between carrier switching frequency and carrier frequency, by analyzing the influence of carrier switching frequency on random carrier signal, it was concluded that the phase mismatch between the front and back carriers was the fundamental reason for the distortion of the output voltage of inverters when the preset carrier was switched randomly. And the switching frequency was randomized by switching the preset carrier, i.e., an improved kind of random carrier frequency modulation (RCFM). The simulation and experimental results showed that the proposed random PWM method could not only suppress the high-order harmonics of the output voltage more effectively, but also have better sinusoidal waveform than the conventional random PWM method.