Lyapunov Stability Constraining Solution of the Cascaded Inverter Based on Model Predictive Current Control

摘要

Cascaded system is one of the basic components of the power electronic converter in the distributed energy system. However, it may become unstable even each subsystem is stable individually, especially when the film capacitor is used to stabilize DC voltage. At present, the existing objective function of finite control set model predictive control(FCS-MPC) does not conform to the definition of Lyapunov function. Most of the existing stabilization methods are linear control method which based on small signal model. Therefore, these methods may be ineffective to fix large-signal stability issues. Thus, the system cannot be guaranteed to operate stably. In this paper, a Lyapunov stability constraining solution(LSCS) is proposed for the cascaded inverter based on FSC-MPC to improve the system stability in the distributed energy system. First, this approach theoretically presents how to add the Lyapunov stability constraining to the MPC objective function in an analytic way instead of using the traditional `experience based' weight method. In addition, the LSCS-MPC itself is also an improvement to realize constant switching frequency. Finally, the feasibility of the method is verified by simulation.