Fault Diagnosis Method Based on Half-bridge Modular Multilevel Converter Power Modules

Modular multilevel converters are widely used in engineering fields because of their low loss and high waveform quality. However, when the number of its sub-modules is high, the switching tubes in the power module are prone to open-circuit and short-circuit faults, which seriously affects the safe operation of the MMC. In order to improve the reliability of the modular multilevel converter converter operation and quickly detect the faults, this paper proposes a detection method based on the combination of hardware circuit and capacitive voltage increment ratio to quickly diagnose the switching tube faults in power modules. Firstly, the switching tube fault characteristics of the power module are analysed, and mathematical relationships are established according to different fault characteristics; secondly, the predicted voltage at the two ends of the capacitor during normal operation is used to diagnose the fault by comparing it with the actual detection voltage. Then, the category of the fault is quickly determined by combining with the hardware. Finally, the simulation is carried out by using Matlab/Simulink, and the results show that the proposed method can accurately and quickly locate and identify the power module faults, which solves the problem of difficult diagnosis of power modules.