FAULT DETECTION AND MITIGATION IN MULTILEVEL CONVERTER BY USING ACTIVE FAULT –TOLERENT CONTROL SYSTEM

Abstract

Modern renewable energy systems mostly utilize multilevel converter applications for improved power quality 
and grid synchronization purposes. A multilevel converter is an electrical device that may offer several amounts 
of voltage levels at the output in order to make the output more comparable to a pure sine wave.The integrity of 
the multilevel converter depends on the reliability of individual switches such that the converter will collapse in 
case of faults in these switches. In this paper, a novel 9-level Fault-Tolerant Cascaded H-Bridge Multilevel 
Inverter (FT-CHB-MLI) has been proposed that offer’s high reliability with improved power quality. A 
dedicated Fault Detection and Isolation (FDI)unit has been built to diagnose the faulty switch and replace it with 
a standby redundant switch. Total Harmonic Distortion (THD) and the determination of a normalized output 
voltage factor are employed for fault diagnosis. The Phase Disposition Pulse Width Modulation (PD-PWM) 
technique has been utilized for switching due to its superior performance as compared to other conventional 
techniques. This early fault detection method not only identified the issues but also performed preventative 
actions to keep the system healthy and stable. The proposed system was tested on the MATLAB / Simulink 
environment to verify its performance. The simulation results demonstrated that the THD has been reduced to 
almost 14% with a significant increase in reliability with advanced fault-tolerant architecture consisting of FDI 
units. The reliability analysis was carried out using Markov chains that also showed its increased reliability. A 
comparison of the proposed work with literature was also carried out to demonstrate its superior performance 
with increased reliability.