A Model Predictive Control Strategy with Fixed Switching Frequency for Three Phase Four Leg Voltage Source Inverter

The traditional three-phase full bridge inverter cannot maintain the balance of three-phase output voltage under special conditions such as the complete coupling of three-phase and the midline current, which affects the operation of the micro-grid and other systems. For this problem, adding the fourth bridge arm can provide a path for the unbalanced current, and then suppress the three-phase voltage imbalance due to the three-phase load imbalance. The model prediction control strategy can be used for the three phase four leg voltage source inverter(3P4L-VSI), but the switching frequency is not fixed, resulting in the magnetic element design difficulties. In this paper, according to the equivalent model of the inverter in the αβγ coordinate system, the prediction model of the single channel is established, and realizes the prediction and control of the fixed switching frequency model of the three phase four leg voltage source inverter with neutral inductor. The correctness of the designed control method is verified by simulation and experiment.