A compact model to coordinate flexibility and efficiency for decomposed scheduling of integrated energy system

The conflict between inflexible operation of high-efficient cogeneration system and demand for flexibility in power grid has engendered severe renewable energy curtailment, which raises a requirement of multi-energy management. Nowadays, researchers have focused on flexibility improvement, but rarely considered energy conversion efficiency of cogeneration systems based on the 2nd law of thermodynamics. This paper establishes a compact model of cogeneration systems by taking nonlinear energy conversion and heat transfer constraints of combined heat and power units into account, and further proposes a two-stage heat and power dispatch procedure. The lower stage conducts plant-level operation optimization to obtain the compact model, i.e., quantitation of the best trade-off relations between energy supply flexibility and conversion efficiency as well as the power generation feasible region in each cogeneration system. The upper stage formulates a convex optimal power flow problem based on the compact model to achieve the global coordination between energy supply flexibility and conversion efficiency in integrated energy system. To apply the model, we introduce a multi-energy management system consisting of a central power-grid dispatch system and multiple distributed plant-level energy management systems. Optimization results reveal that the proposed method saves 11.65% heat consumption comparing with traditional method.