A Real-Time Method for the Diagnosis of Multiple Switch Faults in NPC Inverters Based on Output Currents Analysis

Abstract

This paper presents a new approach for fault diagnosis in three-level neutral point clamped inverters. The proposed method is based on the average values of the positive and negative parts of normalized output currents. This method is capable of detecting and locating multiple open-circuit faults in the controlled power switches of converters in half of a fundamental period of those currents. The implementation of this diagnostic approach only requires two output currents of the inverter. Therefore, no additional sensors are needed other than the ones already used by the control system of a drive based on this type of converter. Moreover, through the normalization of currents, the diagnosis is independent of the load level of the converter. The performance and effectiveness of the proposed diagnostic technique are validated by experimental results obtained under steady-state and transient conditions.

A Review of Open-Circuit Switch Fault Diagnostic Methods for Neutral Point Clamped Inverter

“…In this signal, data such as current or voltage or both signals are directly used as fault signature information. Current-based fault diagnostic methods [18,[24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] are more popular as they do not require any extra hardware. Some authors used voltage-based fault diagnostic methods [39][40][41][42][43][44][45][46].…”

“…An open-switch fault detection of NPC inverters using output current is discussed in [34]. From the knowledge of switching states and output normalized average currents, the faulty leg can be identified.…”