Fault Diagnosis for the Cascaded H-Bridge Multilevel Converter Considering Fault Coupling Between Switches and Sensors

Power switches and sensors could suffer from undesired failures during the operation period of the cascaded H-bridge multilevel converter (CHBMC). Existing diagnostic algorithms are designed primarily for one category of component failures, easily resulting in misdiagnosis when the failure is from another category of component. Considering this issue, the detection variable, independent of modeled sensor signals, is designed to decouple the fault features of switches and sensors. The fault detection and isolation (FDI) in different sensors is accomplished by state estimation and comparisons. The switch open-circuit faults can also be further identified by extracting fault information from the designed variable. The simulation and experimental results have confirmed the validity of the proposed method.