A strengthened mixed-integer linear programming formulation for combined-cycle units

Due to increased utilization of gas-fired combined-cycle units for electric power generation in the U.S., accurate and computationally efficient models for operating these units are crucial to keep an electricity system reliable. The recently proposed edge-based formulation for combined-cycle units helps accurately describe the operations of combined-cycle units by capturing the state transition processes and physical constraints for each turbine. In this paper, we derive tighter constraints and several families of strong valid inequalities to strengthen the edge-based model and improve its computational efficiency by exploring the physical characteristics of combined-cycle units and utilizing the edge-based modeling framework. Meanwhile, we provide the validity and facet-defining proofs for certain inequalities. Finally, the computational results indicate that our derived formulation significantly reduces the computational time, which verifies the effectiveness of proposed tighter constraints and strong valid inequalities.