Dynamic models of pipe using circuit equivalents for efficient co-simulation of electric and thermal transients in energy system

Abstract

As power-to-heat technologies are increasingly utilized to support the heating and cooling demand in the building and industry sectors, electric power systems will integrate more closely with heating and cooling systems. The interaction between different energy systems becomes important for system operators. It would be beneficial for grid operators to model heating and cooling systems in the simulation environments typically used for the analysis of electric systems. To facilitate such simulation, two novel models for pipes are proposed in this paper. Based on the analogy between thermal quantities and electric quantities, electric circuit equivalents are used to develop the models. In the proposed models, the hydraulic and thermal quantities of fluid in a pipe are represented by electrical quantities. By exploitating the “end-to-end” thermal relationship of a pipe, the first model comprises only two nodes for a pipe and is thus computationally efficient. Taking axial diffusion into account, the second model is extended from the first model to capture fast thermal transients. Both models have been validated against experimental measurement data for slow transients with an error less than 1%. The second model additionally provides highly accurate approximation to fast transients. The value of the models is explained and demonstrated through a case study thereafter. With the proposed pipe models, thermal dynamics in pipes can be efficiently simulated in circuit-oriented simulators. The proposed work extends the application scope of such simulators and improves the simulation efficiency. This facilitates the analysis of energy interactions between power systems with district heating and cooling systems.