Neutral-point voltage balancing method for three-phase four-leg three-level ANPC inverter based on modulation waveform splitting

Abstract A neutral-point (NP) voltage balancing method based on modulation wave splitting is proposed for a three-phase four-leg (3P4L) three-level (3L) active NP clamped (ANPC) inverter. According to the principle of changing the NP current by adjusting the o-state duty cycle, the NP current injected by each carrier period is made zero by splitting the modulation waveforms of the mid-phase and N-phase. This approach eliminates low-frequency fluctuation in NP voltage under various load conditions. On this basis, according to the inverter operating state and limiting conditions, the output o-state duty cycle of the modulation wave for the intermediate phase and N-phase is adjusted to suppress the NP voltage deviation caused by various non-ideal factors. Finally, the effectiveness of the method is verified through simulation.