Synergistic flexibility enhancement method of photovoltaic-coal-fired hybrid power generation systems considering fatigue life assessment

With the rapid integration of renewable energy sources, coal-fired power plants have been increasingly required to provide auxiliary services. The accelerated low-cycle fatigue damage from rapid and frequent load cycling has become a potential concern. This study proposes a novel coordinated control framework for hybrid power generation systems combining photovoltaic (PV) and coal-fired power plants to mitigate steam turbine degradation while ensuring grid reliability. First, a multi-scale model of the hybrid system has been developed, which includes a physics-informed inertial element network model that captures the dynamic temperature gradients in steam turbine rotors, facilitating more precise calculations of equipment lifespan loss and maintenance costs. Next, a coordinated control method is proposed, featuring a “coal-fired plant leads, PV follows” strategy. This approach employs adaptive flexible power point tracking method for PV systems that assist coal-fired plants in frequency regulation, reducing the ramping rate to extend steam turbine maintenance cycles. Finally, the method is compared to independent regulation by PV or coal-fired plants, assessing flexibility and economic efficiency under different dynamic processes. Case studies reveal that implementing an optimal ramp rate constraint of 0.36%/min achieves dual benefits without a notable increase in total economic losses: frequency fluctuation amplitude reduction of more than 83%, rotor life loss mitigation to less than 10% of conventional operation levels. Therefore, the hybrid generation systems combining PV and coal-fired power plants improve frequency support while reducing regulation costs, offering a new approach to balancing lifespan and economic efficiency under rapid load changes.