A Virtual Space Vector Pulse Width Modulation Based on Multi-Vector Synthesis for Neutral Point Clamped Three-Level Inverter

The neutral-point clamped (NPC) three-level inverters has been widely researched and adopted in industry, for the advantages of better output waveform quality and lower voltage stress. Using the conventional virtual space vector pulse width modulation (VSVPWM) method, the neutral point (NP) could be kept stabilized and balanced over the full range of power factors or modulation indices. However, the traditional VSVPWM method requires complicated sector identification and computation. In this paper, we propose a novel virtual vector modulation based on multi-vector synthesis. Through a novel division of the space vector diagram, this method effectively reduces the number of space vector sectors. With the reasonable vector sequence, this method not only maintains the neutral current at zero but also ensures the smoothness of the output voltage waveforms. Thus, this modulation effectively decreases the computational effort while keeping the balance of the NP potential. Finally, the experimental results verified the efficacy of the modulation method and the equilibrium of the NP potential.