Three-phase four-leg inverter based on current positive feedback control

The power quality of grids has been influenced by the mounting number of asymmetric loads. Recently, the three-phase four-leg inverter which adds a bridge to three-phase three-bridge inverter has been researched because of the merit of the compact structure, small bulk and high efficiency. The three-phase four-leg inverter has subsequently brought vigor into the power system with broad application prospects but its control method becomes much more complex than ever and difficult to achieve. Therefore, a new control method has been proposed in this paper based on positive feedback of current control and three-dimensional space vector modulation (SVM). Through analyzing the four-leg inverter system, three-phase unbalanced current is introduced from the three-phase voltage feedback control. Furthermore, the amount of imbalance is increased through positive feedback in order to control the balanceness of three-phase output voltage more quickly and accurately. The simulation showed the feasibility and effectiveness of the method proposed in this paper.