A Novel fault-tolerant structure for a single-phase seven-level cascaded Hh bridge multilevel inverter

Abstract

Cascaded H-bridge multilevel inverter (CHBMLI) is the most popular topology for high power and high voltage applications. There are total 4m numbers of power electronic switches in a CHBMLI having m numbers of modules (m2). Because of higher number of switches; the possibility of faults in switches is more. A CHBMLI is said to be “reliable”; if it continues delivering output voltage; even after fault in switches of m-1 number of modules. A fault-tolerant structure is proposed for CHBMLI having 3 modules. Wherein; any 1 out of 3 modules gets faulty; the remaining 2 healthy modules will continue delivering output voltage with the same amplitude and the same voltage level as in case of normal operation having all the 3 modules are healthy. When any 2 out of 3 modules get faulty; the remaining 1 healthy module will continue delivering output voltage with the same amplitude and reduced voltage level. In this way, the proposed fault-tolerant structure of CHBMLI improves the system reliability by preventing the breakdown of the whole system till at least 1 module is healthy.