A Hybrid Control Method for Neutral-Point Voltage Balancing in Three-Level Inverters

Neutral-point (NP) voltage fluctuation is an inherent problem in three-level inverters. Without any control measures, the NP voltage will deviate, and the dc bias and ac oscillation can be observed, which may lead to the failure of power devices and capacitors, so as to damage the system security. In this letter, a hybrid control method is proposed, which it combines zero-sequence voltage regulation with the decomposition of modulation waveform organically. This carrier-based method is simple with lower switching loss due to the unchanged switching events per switching cycle. Experiments are carried out in a 10-kVA three-level platform, which demonstrate the validity of proposed method.