Unified Formulations for Combined-Cycle Units

In this letter, we describe and develop edge-based and node-based formulations for combined-cycle units (CCUs) with different levels of accuracy in respect of the physical constraints of each turbine, from no requirement to partially and fully respecting all physical constraints, including min-up/-down time, capacity, and ramping constraints. We develop corresponding models for independent system operators (ISOs) and vertically integrated utilities (VIUs), respectively. These models demonstrate complexity in terms of the size of decision variables and show the tradeoff between accuracy and computational complexity. To the best of our knowledge, this letter provides one of the first models that can capture both configuration transition restrictions and all the physical constraints of each turbine within CCUs, for both ISOs and VIUs.