Design of New SVPWM Mechanism for Three-Level NPC ZSI via Line-Voltage Coordinate System

In this article, a novel space-vector pulsewidth modulation (SVPWM) mechanism is proposed for a three-level neutral-point clamped (NPC) Z-source inverter (ZSI) via the line-voltage coordinate system. In order to solve the problems of the adjustment of the complicated operational region and the complex computation of lookup tables in conventional methods, the newly designed SVPWM mechanism is developed from the basis of the vector synthesis. With this mechanism, switching vectors required to synthesize the reference vector can be easily identified, and the corresponding duty ratios can be directly obtained. According to the volt-second balanced principle and three operational modes of the three-level NPC ZSI, the up shoot-through status is inserted into the left side of the intersection point of the maximum phase modulation signal and the carrier wave signal. On the other hand, the down shoot-through status is inserted into the right side of the intersection point of the minimum phase modulation signal and the carrier wave signal. The effectiveness of the proposed SVPWM mechanism is verified by numerical simulations and experimental results. The salient features of the proposed SVPWM method are easiness in digital implementation, less computation time, and better power quality in comparison with traditional SVPWM schemes.