An improved virtual space vector method for three-level NPC inverters

The neutral-point clamped (NPC) three-level inverters has been widely researched and adopted in industry. In order to solve the problem that virtual space vector pulse width modulation(VSVPWM) has weak balance ability of neutral point voltage(NPV) in high modulation index. The paper proposes a novel virtual strategy that enables the formation of a redundant state with the basic medium vector, thereby achieving complete controllability of the neutral point current generated by the basic medium vector, The controlled neutral point current is then used to balance the NPV. Simulated results validate the effectiveness of the proposed method.