Prediction Current Control Strategy Based on Sliding Mode for NPC Three-Level LCL Inverter

Prediction model is an important part of model predictive control, and the accuracy of the model directly affects the control performance of the system. Aiming at the problem of poor robustness caused by parameter mismatch in model predictive control, this paper proposes a sliding mode predictive current control strategy, which combines the advantages of sliding mode control with model predictive control for NPC-type three-level LCL grid-connected inverters. Firstly, the split-capacitor method is used to reduce the system order, which varied from the third order to the first one. The proposed method simplifies the prediction model, and indirectly controls the grid-connected current with the intermediate current of two capacitors as the control target. Then, the cost function of model prediction is established by the sliding mode control principle, and the delay compensation is carried out by two-step method. Finally, the effectiveness of the proposed control strategy is verified by simulation, which shows that the method can improve the parameter robustness of the system in the case of parameter mismatch.