Switch fault detection and diagnosis in space vector modulated cascaded H-bridge multilevel inverter

This article investigates the development and online implementation of the power switch open-circuit fault detection and diagnosis in symmetric cascaded H-bridge multilevel inverter. A mathematical modelling technique is presented to understand the effect of the fault on the bridge voltages and output voltage. The modelled values of the output voltage, simulation results and experimental results indicate that the fault diagnostic methods based on the output voltage as the diagnostic feature have certain ambiguity in identifying the fault switch, since the output voltage waveform and its features remain the same for a group of switches under the fault condition. In order to overcome this, fault detection and diagnosis method based on the mean values of the bridge voltages is proposed in this article, which identifies the faulty switch pair and H-bridge in which the fault has occurred. Further, this method has been experimentally validated on a five-level space vector modulated symmetric cascaded H-bridge multilevel inverter.