Generalized open switch fault diagnosis of cascaded h bridge multilevel inverters

Abstract

Multilevel inverters (MLIs) are essential part of high power DC to AC conversion newlinesystems owing to their high-quality voltage output using switches having lesser newlineratings. Cascaded H-bridge multilevel inverter (CHB MLI), which is popular among newlineMLIs, is a prospective component in high-power medium-voltage industrial and newlineautomotive drives due to its modularity and fault ride-through capability. CHB MLI newlinecan integrate low voltage renewable sources to the industrial drive systems. Since newlineMLIs are realised with a larger number of power switches than conventional two-level newlineinverters, these inverters have an elevated probability of switch failures. newlineWhen different types of possible faults in inverter-fed drives are considered, newlinenearly one-third of defects are due to the switch failures. The common faults occur newlinein power semiconductor devices are short-switch fault (SSF) and open-switch newlinefault (OSF). The SSFs are the most destructive and frequent; hence dedicated protection newlinesystems for these faults are integrated with most of the existing inverter-fed newlineindustrial drives. Even though OSF is less severe than SSFs, it is a significant contributor newlinein drive failures. The presence of open switch in the converters results in newlineunbalanced output voltage, load torque oscillations, increased stresses in switches newlineand local hot spots. OSFs may not lead to an immediate halt of the drives, but they newlineusually remain undetected in the system and eventually lead to secondary failures newlinethrough voltage and thermal stresses. Hence, an open switch fault diagnostic strategy newlinemust be incorporated with crucial drive systems to improve their reliability. The newlineidentification of faulty switch is the preliminary step for fault-tolerant operation of newlineinverter-fed drives. Therefore, in this work OSF detection and classification in CHB newlineMLI is selected as the topic for investigation. newline