Abstract: A power generation company has 3 stages of plant security power supply, turbine security MCC I stage, Turbine Security MCC II stage, boiler security MCC stage. Three power sources are installed in each section of the plant security power supply: Turbine Boiler PC 1A section, Turbine Boiler PC 1B section and diesel generator group. There are some problems such as long switching time and low reliability of power supply. Based on the fast start-up characteristics of the battery and converter of the 18MW/9MWh energy storage frequency modulation system in Xinchang power plant, the power supply system of the security section is optimized and retrofitted. It can start and support the auxiliary security power after the auxiliary power supply loses power, and improve the reliability of the auxiliary security section.