Triangle Carrier-Based DPWM for Three-Level NPC Inverters

This paper proposes a triangle carrier-based discontinuous pulsewidth modulation (TCB-DPWM) implement method for three-level neutral-point-clamped (3L-NPC) inverters. The function equivalent relationship of the proposed TCB-DPWM and space vector-based DPWM (SVB-DPWM) is mathematically analyzed in this paper. The proposed TCB-DPWM method effectively simplified the implementation of the SVB-DPWM by injecting twice common mode voltages (CMVs) to original modulation signals, where different DPWM methods can be easily obtained in a unified scheme by setting different values of the proportional allocation factor for small vectors in different sectors. In addition, a TCB-DPWM-based neutral-point voltage balancing method is investigated to demonstrate its application. The polarity of the CMV injection is regulated according to the polarity of the proportional allocation factor to realize the neutral-point voltage balancing. Finally, the proposed TCB-DPWM and the neutral-point voltage balancing method are both verified by simulation and experimental results. The results show that the proposed TCB-DPWM can effectively simplify the implementation of modulation and improve system efficiency.