AbstractWith the proposed goal of 30•60 carbon peak and carbon neutrality, the proportion of new energy continues to increase, the proportion of conventional power supply capacity continues to decrease, and the flexibility demand of the existing power system continues to increase and the flexibility adjustment ability is insufficient. Therefore, a medium and long term planning method is proposed to flexibly adjust the multi‐time scale coordination of thermal power support wind and solar storage. Considering the long‐term investment decision and the short and medium term operation simulation, the flexible transformation cost and the penalty cost of insufficient flexibility of thermal power units are included in the planning objective, and a multi‐time scale coordinated planning model is established with wind power as the main power source and thermal power and hydrogen energy storage as the auxiliary power source. Through the multi‐stage cycle iteration of investment decision model, medium and long term production simulation and typical daily operation simulation, the flexible transformation resources of wind and solar fire storage and thermal power are optimized. Finally, a provincial power grid in northeast China is taken as an example to verify that hydrogen energy storage equipment assisting thermal power unit flexibility transformation can better support load fluctuation and large‐scale new energy access in new power systems.