Abstract: This paper analyzes the faults of the main unit outage control system, the stability and reliability of the DEH power supply system is very important when the unit is in normal operation and the generating control is abnormal, in order to ensure the safe and stable operation of the steam turbine when the AST solenoid valve loses power when the ETS power supply fails, the solving methods and treatment measures are put forward pertinently, to improve the standardization of control system maintenance from the aspects of technical treatment and professional management, summarize and analyze the main factors of thermal control power system failure, avoid the occurrence of similar problems can be dealt with quickly and effectively.