Abstract: With the continuous increase in the penetration rate of fluctuating renewable energy such as wind power, the power system has put forward higher requirements for the frequency regulation performance of main power sources such as thermal power.Energy storage assisted frequency regulation is an effective means to improve the frequency regulation performance of thermal power units and promote the large-scale development of renewable energy. Taking flywheel energy storage as the research subject,a primary frequency regulation model of the flywheel-thermal power joint system is established, and a method for decomposing primary frequency regulation instructions based on fuzzy adaptive adjustment of filtering time constant is proposed. A primary frequency regulation control strategy based on flywheel-thermal power frequency division collaborative support is designed,achieving a flexible response of the flywheel-thermal power joint system to grid frequency. Simulation verification is conducted on a flywheel-thermal power joint system with equal frequency modulation capacity, and the results show that the proposed strategy further improves the frequency regulation performance of the flywheel-thermal power joint system.