A Novel Approximate Model Based Fault Diagnosis Technique for a Photovoltaic DC/AC Grid Tied Inverter

摘要

The recent popularity in the utilization of photovoltaic (PV) systems over conventional power generation has placed focus onto the reliability of support equipment, such as DC-AC inverters. With prolonged use, short-circuit (SC) or open-circuit (OC) faults can develop in the semiconductor devices. This work is proposing a novel fault diagnosis algorithm. The method makes use of the H-bridge inverter approximated as a synchronous switching buck converter while assuming that the grid frequency is much lower than the inverter switching frequency. The proposed algorithm allows detection and identification of SC and OC faults by combining a comparison between the estimated and actual inductor current and the incremental change in the output voltage. To allow continuous functioning of the inverter post fault, a redundant leg is added to the PV inverter. In this PV inverter topology, a fuse is allocated for each switch to prevent overcurrent and a triode for alternating current (TRIAC) is added for each leg to allow isolation of the faulty leg and connection of the redundant leg.