Condition Analysis on Implementation of On-Line Monitoring of IGBT Modules of Three-Level NPC Inverters

Implementation of on-line monitoring of IGBT modules in the three-level NPC inverters is necessary nowadays. The implementation of on-line monitoring requires an on-line monitoring condition and off-line monitoring technique to attach. In the previous study, it has been researched that the saturated voltage drop (V
_CE
) is one of the most essential diagnostic sign of IGBTs' healthy status, which is the key point of off-line monitoring technique in the monitoring system. So the on-line monitoring condition is mainly researched in this paper. Analysis has been made to show that it is necessary to force the operating state of monitored phase of inverter to be O state during the on-line monitoring. The results of simulation and experiment of the process of on-line monitoring verify the correctness of the condition analysis in this paper.