Online Monitoring of Capacitor of Submodule in M3 C Converter

Modular multilevel matrix converter (M3C) is a crucial device in fractional frequency transmission system (FFTS). Its submodule capacitor needs to bear the impact of huge bridge arm current and has the highest failure rate in the system. ESR (equivalent series resistance, ESR) value and capacitance value, as important parameters reflecting capacitor health, play a significant role in aspects such as capacitor efficiency evaluation, predictive protection and so on. Based on the M3C converter model, this paper raises an online monitoring method of ESR value on the account of changing characteristics of switch signals of M3C submodule and capacitance value using Kalman filter. Finally, through PSCAD/EMTDC simulation platform, the 59 level M3C converter model is simulated, and the simulation data shows the practicability of the online monitoring method.