An Online Monitoring Method for IGBT Modules in Single-Phase Three-Level Neutral Point Clamped Inverters

Online monitoring of insulated gate bipolar transistor (IGBT) modules is an effective way to improve the reliability of inverters. This paper proposes a method for online monitoring of IGBT’s bond wires in single-phase three-level neutral point clamped inverters. The proposed method has a negligible impact on the output current of the inverter, the key of which is to clamp one leg of the inverter to the O state by zero-sequence component injection at the monitoring time. Based on this method, we can create an online monitoring environment to inject monitoring current into the idle IGBT. By sampling the collector-emitter saturation voltage during monitoring, the health state of the IGBT can be obtained. Calculations and simulations show that clamping duration is more significant than the one required for single monitoring, even under the worst conditions.