[Objective] Improving the control level of reheat steam temperature under deep peak shaving and rapidly varying load demands has become the key to enhancing the flexibility and safety of double-reheat coal-fired power generation units. [Methods] The control strategies of the primary and secondary reheat steam temperature during the load cycling process were studied and optimized based on a coupled model of steam temperature control and dynamic simulation for a 660 MW ultra-supercritical double-reheat coal-fired power generation unit. [Results] The original control strategy for adjusting the primary and secondary reheat steam temperature by flue gas dampers in triple-rear passes was adopted. The temperature deviations of the main steam

primary reheat steam and secondary reheat steam at the boiler outlet under the steady-state conditions ranging from 30%THA to 100%THA can be controlled within 5.00 ℃. However

the load tracking capability of the primary and secondary reheat steam temperatures of the double-reheat coal-fired power generation unit is poor during the load cycling process. The primary and secondary reheat steam temperatures of the double-reheat coal-fired power generation unit are too low during the loading up process

and they are too high during the loading down process

which seriously affects the safe operation of the ultra-supercritical double-reheat coal-fired power generation unit. Regarding the problem of poor load tracking capability of the primary and secondary reheat steam temperatures for 660 MW ultra-supercritical double-reheat coal-fired power generation units

the control logic of the water-coal ratio is redesigned. The revised water-coal ratio control strategy with the main steam temperature deviation

primary reheat steam temperature deviation and secondary reheat steam temperature deviation is adopted based on the original control strategy for the 660 MW ultra-supercritical double-reheat coal-fired power generation unit

considering variation characteristics of heat storage in the coal-fired boiler during the load cycling process

namely the accumulation of heat storage in the coal-fired boiler during the loading up process and the release of heat storage in the coal-fired boiler during the loading down process. The results show that

the revised control strategies could enhance the load tracking capability of the primary and secondary reheat steam temperatures for 660 MW ultra-supercritical double-reheat coal-fired power generation units

significantly reduce the maximum overshoots during the load cycling process

and significantly improve the control accuracy of the primary and secondary reheat steam temperatures during the load cycling process. [Conclusion] The control strategy optimization of the reheat steam temperature in this paper can provide references for the operation of the double-reheat coal-fired power generation units.