Open-Circuit Fault Diagnosis and Fault-Tolerant Control with Sequential Indirect Model Predictive Control for Modular Multilevel Converters

Fault diagnosis and fault-tolerant control are significant for the reliability of an MMC system, which usually has a large number of switching devices and high potential of operation failure. This paper proposes a simple fault diagnosis method for sub-module open-circuit faults and a new fault-tolerant control method. The proposed methods combine a novel sequential indirect MPC structure with sorting algorithm. Different from the well-known solutions, we detect and locate open-circuit faults in any sub-module efficiently with the maximum voltage output of the capacitor voltage sorting result, which is based on the physical characteristics of circuits when capacitor voltage rises. Thereafter, a new fault-tolerant control solution based on MPC is implemented through modifying circuit structure and control algorithm. The proposed methods are easy to implement and add little computational complexity to the control algorithm. Finally, the MATLAB/Simulink verification results confirm the effectiveness of the proposed solutions.