Abstract: In order to solve the problem that the start-up failure and the normal equipment are isolated by the TCMS due to the misoperation of the auxiliary converter during the start-up control of the medium voltage power supply, this article designed a pre-set clear and late backup troubleshooting method. The control strategy can not only effectively avoid unnecessary medium voltage load shedding, but also significantly improve the reliability of the train medium voltage power supply system and passenger comfort, it also ensures the smoothness of the auxiliary converter starting logic cycle. Ground simulation platform simulation and vehicle field test verification results were very effective.