Fault Tolerant Five-Level Active NPC Inverter for High-Reliability Photovoltaic Applications

Increasing penetration of the Photovoltaic (PV) systems in electric power generation sector entails high-reliability grid-connected PV inverters. In fact, inverter faults are one of the most common root causes for PV system failures that significantly increase the levelized cost of energy (LCOE). Meanwhile, higher voltage levels are favorable for utility-scale PV applications due to higher energy efficiency. Hence, a novel fault-tolerant four-leg five-level active neutral point clamped (5L-ANPC) inverter is proposed in this paper. In a fault scenario, the fourth leg can replace any of the faulty phases of the inverter to provide the fault-tolerant capability for post-fault operation. In normal healthy condition, the fourth-leg can be used for heavy-load current sharing to mitigate the thermal stress on the semiconductor devices of the main phase legs, which further enhances the PV system reliability. Simulation results are demonstrated to verify the effectiveness of the proposed PV inverter.