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Optimal scheduling for combined district heating and power systems using subsidy strategies

The ongoing development of cogeneration technology has promoted public awareness on the integration of different types of energy systems. Integration of power and heating systems is the most common approach for energy transmission. The heat and power coupling of combined heat and power (CHP) units constrains the improvement of flexibility to accommodate more wind power, especially in winter. To address this problem, electrical boilers (EBs) are utilized as independent heat sources in one heat station to enhance their flexibility. This paper proposes a subsidy based bi-level optimal model. The objective of the upper problem is to minimize the operating cost, while the lower problem is to maximize the benefits of CHP and EBs based on the subsidy signals sent by the power system operator (PSO). The bi-level model is reformulated as a single -level linear problem by Karush Kuhn Turck (KKT) conditions and recast to a mix integer quadratic program using strong duality theory. Numerical results performed on an IEEE six-bus system with a eight-node district heating system validate the proposed model. The results demonstrate that the subsidy strategies can make the EB and CHP units operate according to the system operators' preferences to accommodate more wind power.