A Neutral-Point Voltage Balancing Control Method Based on Model Predictive Control for T-Type Three-Level Inverter

The neutral-point voltage balancing control of the T-type three-level inverter system is the primary problem. The main circuit mathematical model and the load model of the T-type three-level inverter are set up, and the main reasons of neutral-point voltage unbalancing are analyzed, then based on the traditional predictive current control method, a neutral-point voltage balancing control method based on model predictive control (MPC) is proposed. Firstly, the load current is sampled used to calculate predictive value, meanwhile the DC bus neutral-point current is sampled to get the neutral-point voltage deviation; then minimize the quality function composed of the squared error between the predictive and reference current values and the neutral-point voltage deviation by choosing the appropriate state's switching signals and then applied to the inverter, the neutral-point voltage balancing control is achieved. Finally the results obtained through the Matlab/Simulink simulation verify that the proposed method ensures fast dynamic response and keeps the neutral-point voltage balancing, and the quality of its output voltage is high.