A Study on Dynamic Analysis and Operational Optimization of an F-Class Combined-Cycle Power Plant Under Seasonal Load Conditions

With the increasing penetration of intermittent renewable energy, combined-cycle power plants are increasingly operated under frequent and deep load-following conditions. Under such conditions, transient irreversibility and its coupling with seasonal boundary changes cannot be adequately characterized by conventional steady-state analysis. Therefore, this paper constructs a dynamic analysis framework based on actual operational data. The first- and second-order rates of change in component exergy destruction are introduced to quantify the direction, intensity, and acceleration of thermodynamic deterioration during winter and summer load ramp-ups and ramp-downs. The results reveal a hierarchical dynamic response. The combustion chamber and gas turbine exhibit the highest and nearly synchronous sensitivity, whereas the heat recovery steam generator (HRSG) and steam turbine respond later and their fluctuations persist longer because of water-/steam-side thermal inertia. The air compressor, condenser, and fuel heater are comparatively insensitive. Load direction and season jointly produce pronounced asymmetric behavior. Winter transients generally exhibit stronger and longer-lasting exergy fluctuations than summer transients. Based on the dynamic diagnosis and engineering adjustability, HRSG feedwater flow is selected as the optimization variable. A feedwater-response adjustment scheme, guided by dynamic exergy analysis, is evaluated through offline calculations and comparisons with historical plant operating data. Relative to the original operation, the maximum relative reduction in HRSG exergy destruction is 20.14%, and the maximum relative increase in exergy efficiency is 7.56%.