Neutral-point potential balancing control strategy of three-level active NPC inverter based on SHEPWM

This study proposes a novel control strategy for a three-level active neutral-point clamped (3L-ANPC) inverter using selective harmonic elimination pulse width modulation (SHEPWM). The proposed control strategy can effectively control the neutral-point potential (NP) balancing and eliminate the selective harmonics simultaneously. The three-phase SHEPWM line-to-line voltages of the inverter are considered as switching-states. Among these switching states, the six pairs of redundant switching-states generate the same line-to-line voltages and thus the same harmonic spectrums with each pair having opposite effects on NP balancing. As a result, the pair of switching-states can be swapped to control the NP while still maintaining the same inverter output. The decision to make such swap will take into account directions of output currents, polarities of NP offsets and exclusion of directly switching between P and N states. The simulation and experimental results on a Matlab/Simulink model and prototype of a three-phase 3L-ANPC inverter are used to verify the effectiveness of the proposed control strategy