Fault Tolerance Analysis of Five-Level Neutral-Point-Clamped Inverters under Clamping Diode Open-Circuit Failure

Abstract

Multilevel inverters are increasingly used in industrial applications in which service continuity is crucial. This paper presents an original approach to ensure the fault-tolerant operation of neutral-point-clamped (NPC) inverters in the case of an open-circuit fault event in a clamping diode, which is rarely investigated in the conducted research work. The proposed fault-tolerant strategy meets the following criteria: restoring rated output voltage and current during post-fault operation, realizing fault-tolerant operation without additional components, maintaining rated total harmonic distortion (THD) during fault-tolerant operation, and fast transition between faulty operation and remedial operation. In the proposed approach, prior to applying the appropriate remedial action, identification of the defective clamping diode is required. In this respect, a very fast and simple logic-based fault diagnosis is presented whose implementation does not need any additional components and external circuit. Moreover, it does not require any component modeling and complicated calculations. The proposed strategy is validated by simulation and experimentation.