An Optimized Three-Phase Three-Level VSVPWM Modulation Algorithm

The fluctuation of NP is a distinctive issue specific to 3L NPC inverters, which can have adverse effects on power quality and even result in inverter failure. This paper focuses on the three-level inverter and aims to establish a mathematical model to study the performance advantages and disadvantages of SVPWM, VSVPWM modulation algorithms, and NPP fluctuation problems. Then, the NP active control method based on the distribution factor is proposed, aiming to rectify the initial imbalance in capacitor voltage by adjusting the action time of positive and negative virtual small vectors. The corresponding model for simulation verification and hardware-in-the-loop experiment was established using MATLAB/Simulink and HIL. Experimental results demonstrate the favorable effect of the proposed algorithm on the active control of NP voltage.