Abasement of Harmonics by Adopting Fault-tolerant Nine-level Inverter for Grid- independent PV System

Abstract: In this paper, a fault-tolerant single-phase nine-level inverter configuration is proposed for photo-voltaic (PV) generation systems. Conventional two-level inverters are popularly used in PV applications, but these inverters provide the output voltage with considerable harmonic content. One of the efficient ways to improve the power quality of PV generation systems is to replace a two-level inverter with a multilevel inverter. Conventional multilevel inverters reduce total harmonic distortion and filter requirements effectively, but it has limitations in terms of reliability due to increased device count and capacitor voltage balancing issues. Therefore, a fault-tolerant single-phase five-level inverter is presented, which is constructed by using a half-bridge two-level inverter, a three-level diode clamp inverter, and a bidirectional switch. fault-tolerant single-phase five-level inverter has less number of switching devices compared to conventional five-level inverters, but these inverter also provides considerable harmonic content. Therefore a fault-tolerant single-phase nine-level inverter is presented. The proposed inverter topology can tolerate the system faults due to failure of the source and/or switching devices with least modification in the switching combinations. Nine-level inverter configuration is formed by cascading the two five-level inverters. The proposed system under normal and faulty condition is simulated in MATLAB/Simulink environment.

Keywords: Fault-tolerant multilevel inverters, photo-voltaic (PV) generation system, power quality, total harmonic distortion (THD).