Simplified SVPWM Capacitor Voltage Balancing Control Method for Four-Level Neutral Point Clamped Inverters

This article proposes a simplified four-level SVPWM (4L-SVPWM) method by combining two-level SVPWM (2L-SVPWM) scheme and three-level SVPWM (3L-SVPWM) scheme to solve the capacitor voltage imbalance issue of the four-level neutral point clamped inverters. It is realized using two simple PI controllers: one aims to balance the middle capacitor voltage, while the other is used to balance the upper and lower capacitor voltages. Operating principle of the proposed method has been provided and analyzed. Finally, taking the 4L-DT inverter as an example, simulation results of it have been provided and analyzed to prove the effectiveness and feasibility of the proposed simplified 4L-SVPWM voltage balancing method.