Research on control method of multilevel inverter based on chaotic modulation

Carrier phase-shift (CPS) modulation is a common modulation method for cascade H-bridge (CHB) multilevel inverters, while the traditional CPS modulation method uses a fixed phase shift angle. The disadvantage is that the output harmonic content is high, and the volume and weight of the filter are large. In order to further reduce harmonics and filter volume, a chaotic control strategy combining switching carrier phase angle method and carrier phase shift sinusoidal pulse width modulation (CPS-SPWM) is proposed. In this scheme, the carrier wave is jitter irregularly and the total number of switching times is unchanged, and the frequency spectrum concentrated on the fundamental wave is dispersed to the high frequency part which is easy to filter out, so the harmonic content is reduced and the power output quality is improved. A 7-level parallel CHB simulation model and experimental prototype were built for verification. The total harmonic distortion degree (THD) was reduced by 47.5% compared with the traditional method, which verified the effectiveness of the scheme.