Linearized Modeling of Integrated Electricity and District Heating Systems with VF-VT Strategy Based on McCormick Envelopes

Combined harnessing of electrical and thermal energies has strengthened the interdependence between electricity and heating systems. It offers extra flexibility to system operation and improves energy efficiency. However, the nonlinearity in the coordinated operation of integrated electricity and district heating systems (IEDHS) brings about computational difficulties. This paper proposes a linearized modeling technique for the IEDHS which operates in variable flow rate and variable temperature (VF-VT) mode. Firstly, the district heating and electricity distribution network, as well as the key components such as combined heat and power (CHP) units are modeled. Then, the coordinated optimal operation (COO) of the IEDHS is formulated. Furthermore, the bilinear terms due to the VF-VT strategy are linearized based on McCormick Envelopes. In this way, the COO problem is reformulated into a standard quadratic programming problem, which can be well addressed by off-the-shelf solvers. Finally, the numeric results demonstrate the potential benefits of the proposed technique in terms of reducing system operation cost and wind curtailment.