Direct Model Predictive Current Control Strategy of Quasi-Z-Source Inverters

This paper presents a direct model predictive current control (MPC) strategy for quasi-Z-source inverters (qZSIs). A discrete-time model is derived that accurately captures all operating modes of the converter. Both sides of the qZSI are controlled simultaneously based on the inductor current and capacitor voltage on the dc side as well as the output current on the ac side. To improve the closed-loop performance of the converter, a long prediction horizon is implemented. However, the underlying optimization problem may become computationally intractable because of the substantial increase in the computational power demands, which in turn would prevent the implementation of the control strategy in real time. To overcome this and to solve the problem in a computationally efficient manner, a branch-and-bound strategy is used along with a move blocking scheme. Simulation and experimental results are provided to verify the effectiveness of the presented control strategy.