Supercritical carbon dioxide closed Brayton cycle power system and control method

The invention discloses a supercritical carbon dioxide closed Brayton cycle power system and a supercritical carbon dioxide closed Brayton cycle power control method. The supercritical carbon dioxide closed Brayton cycle power system comprises a gas compressor, a working medium processing drainage assembly, a flow dividing assembly, a gas turbine, a power turbine power generation assembly and a working medium recycling processing assembly. A first flow path used for communicating with the gas turbine, a second flow path used for communicating with the power turbine power generation assembly and a third flow path used for communicating with the working medium recycling processing assembly are arranged at the output end of the flow dividing assembly. The flow of a medium working medium entering the first flow path and the flow of a medium working medium entering the second flow path are divided and controlled through the flow dividing assembly, and the remaining medium working media are guided into the working