一种适用于中点电压不平衡的低开关数量三电平逆变器的直流链电流纹波抑制方法

The reduced switch count three-level inverter (RSC TLI) can reduce the number of power switches, but the conventional space vector modulation (SVM) method generates the large dc-link current ripple and reduces the dc-link capacitor reliability. This article proposes a novel dc-link current ripple reduction method, which applies to both balanced and unbalanced neutral-point (NP) voltage (NPV) conditions. First, the duty-cycle calculation of the conventional SVM method is introduced. To realize the dc-link current ripple reduction, the region division method is optimized by analyzing the range of the duty-cycle distribution factor and combining the magnitude of output current. In doing so, the calculating complexity of duty cycles is reduced. Second, a deadbeat control (DBC) method is designed for accurate and fast separate control of capacitor voltages. At last, appropriate switching sequences are arranged. Compared with the conventional SVM method, the dc-link current ripple of the proposed method is reduced by one-fourth and two-fifths in the high- and low-modulation indices, respectively, and maintains the rewarding quality of output currents with balanced and unbalanced NPVs. The feasibility and effectiveness of the proposed method are verified by simulations and experiments.