Reliability Modeling and Analysis on Metallized Film Capacitors for MMC

Metallized film capacitor's (MFC's) reliability directly affects the stable operation of MMC valve. Conventional reliability assessment method based on data statistics is limited. This paper studies the reliability modeling of MFC considering aging for the application condition of MMC valve. Firstly, the temperature field and electric field model of MFC is established, and the temperature and electric stress distribution are explored. Secondly, the lifetime model of MFC is established based on the electrical-thermal aging of dielectric films. Finally, the aging model of MFC is established from the aspect of equivalent series resistance. Results show that the aging rate of MFC increase with the service time going by, and increase sharply after 21 years. The failure rate of MFC is small at the beginning of operation, and there is a turning point in the 23rd year. Since then, the failure rate of MFC increases sharply. The lifetime of MFC is concentrated.