A Novel SVPWM for Three-Level NPC Inverter Based on m-Mode Controllability

A novel space vector pulse width modulation (SVPWM) strategy for three-phase four-wire neutral-point-clamped (NPC) inverter is proposed in this paper. The m-mode controllability of a three-phase four-wire NPC inverter, which is modeled as a switched linear system, is investigated. Then, on the basis of analysis of the m-mode controllability, taking the three-level property and the continuity of switching sequence into account, the controllable sets with the three-level property can be a new solution for the NPC inverter. With the sets of less operating modes, new modulation strategies named 18-mode SVPWM strategy, including 18-mode SVPWM(I), 18-mode SVPWM(II), and 18-mode SVPWM(III), are put forward. Compared with the conventional SVPWM strategy, the switching frequencies of the proposed 18-mode SVPWMs modulation strategy are significantly reduced by one-third. Therefore, the overall losses of the system can be reduced and the performance of the inverter can be improved. Finally, the simulation and the experiment results verify the correctness of the proposed approach.