Simplified Diagnosis Method for CHBMIs under Open-circuit Switch or Battery Failure

Abstract

This paper deals with the diagnosis of cascaded H-bridge multilevel inverters controlled by a sinusoidal level-shifted pulse-width modulation technique. For this purpose, the behaviour of 3, 5, 7 and 9-level inverters is studied for regular and faulty operation modes. Three types of recurring faults are considered, namely open-circuit of a switch, damaged and disconnected battery. Under a single fault, the output voltage signals are presented where the impact of each fault is discussed. In order to detect, identify and locate the three types of fault, a signal processing method is proposed, elaborating the output voltage of inverters with and without fault. The obtained results are convincing for the considered cases. The study shows no real correlation between the selected features from one to the other type of fault. Indeed, each fault type has its own trajectory with respect to the evolution of the output voltage characteristics. Thus, localizing the faulty component within the multilevel inverter can be made with no ambiguity. Such findings obviously solve a large part of problems associated with the presence of faults in multilevel inverters. They can help improving the reliability of the inverter in such way it continues working.