Research on Diagnosis and Coordinated Suppression Method of Steady-State Deviation in Reheat Steam Temperature of Coal-Fired Units

Reheat steam temperature is an important operating parameter for coal-fired power units, and its long-term steady-state deviation may affect the safety of reheater heating surfaces and increase the use of desuperheating water. Taking a coal-fired unit in a power plant as the research object, this paper analyzes the steady-state deviation of reheat steam temperature from the aspects of on-site control mode, operating data characteristics and regulating delay. The results show that this deviation is not a simple temperature fluctuation, but is closely related to load variation, fuel input, flue gas temperature distribution, damper execution characteristics and desuperheating protection logic. On this basis, a coordinated suppression strategy is proposed. Load, fuel flow and flue gas temperature are introduced as feedforward variables, final-stage reheat steam temperature is selected as the main controlled variable, and flue gas temperature at the inlet of the regulating damper is used as the auxiliary controlled variable. A feedforward-feedback cascade control structure is then established, together with coordinated damper allocation, variable-parameter PID regulation and emergency desuperheating water protection. The proposed method can reduce frequent manual adjustment, limit unnecessary desuperheating water use, and improve the automatic control performance of reheat steam temperature, providing a reference for the safe and economical operation of similar coal-fired units.