An Improved Varied Virtual-space-vector Modulation for Neutral-point-clamped Three-level Inverter

Abstract

The problem of neutral-point potential balance is always an inherent problem of three-level inverters. In this paper, an improved varied virtual-space-vector modulation method is proposed to improve the neutral point potential balance capability of three-level inverters. Firstly, the virtual medium vector is redefined, and the distribution coefficient k is introduced to control the amount of charge flowing out of the neutral point. Secondly, based on the principle of compensating the maximum charge in a switching period, the appropriate composite voltage vector is selected to improve the dynamic response of neutral point balance control. The simulation results show that the method can accurately control the neutral point potential balance in the full power factor range, and the dynamic and static performance of this method is excellent.