A Control Strategy for Three-Level Inverters With Unbalanced DC-Link Voltages in the dq0 Coordinate

When faced with unbalanced dc-link voltages in three-level inverters, the output voltage and current will be distorted if conventional control strategies and modulation schemes are applied. Therefore, in this paper, a control strategy is proposed for three-level inverters with unbalanced dc-link voltages in the dq0 coordinate. Based on the dual-loop control strategy, the unbalancing degree closed-loop is added and feedforward decoupling is adopted to mitigate the interact between different control loops. Finally, the effectiveness of the proposed unbalancing degree control strategy is verified by simulation results.