Load Flow Analysis of District Heating Systems by a Newton-Raphson Method

This paper proposes a Newton-Raphson (NR) based method for solving the steady-state load flow model of a district heating network which has two physical processes interacting with each other, i.e., the hydraulic and thermal processes. In this method, the flow directions in the hydraulic and thermal models are determined systematically. The outflow (direction) indication variables are introduced and updated in each step (iteration) of the NR method. As such, the formulation of the hydraulic and thermal models can be integrated as a hydraulic-thermal model and be solved together, which previously were considered separately and solved in sequence with less efficiency. Case studies are performed and the results show that the hydraulic-thermal model can handle the changes of flow directions during the iterative steps of the NR method and correctly obtain the steady-state load flow analysis results of a district heating network.