Abstract: Aiming at the unit tripping events and abnormal operation conditions caused by power supply failure of thermal control system in coal-fired power plants, the analysis on the failure mechanism and reliability of the DC power supply system is conducted. Based on the analysis, the solutions are put forward respectively, in which for the in-service units, special DC switching device is adopted to eliminate the coupling effects of diode on the reliability of DC power supply system, while for the newly built units, the AC system is chosen as the power supply of thermal control systems.

Key words: power supply of thermal control system, DC/DC, special DC switching device, dual channel