Online monitoring method of MMC flexible DC converter valve IGBT health state monitoring system

The invention discloses an online monitoring method of an MMC flexible DC converter valve IGBT health state monitoring system, and relates to the technical field of flexible DC power transmission. Most of existing MMC flexible direct current converter valve IGBT monitoring systems carry out IGBT health state monitoring through turning off voltage, current, resistance, junction temperature and other characterization parameters and through an expert diagnosis system, and calculation and training of the expert diagnosis system are relatively complex. According to the method, the turn-off time is calculated according to the voltage at the two ends of the IGBT, the current flowing through the IGBT and the gate voltage of the IGBT, and the health state is judged through an expert diagnosis system. By selecting the turn-off delay time of the IGBT as the characterization quantity of the health state of the IGBT, the calculation quantity and the learning training quantity of an expert diagnosis system are reduced, and