| In traditional energy systems,different energy systems are relatively independent,and there are few physical interconnection and information communication interactions,leading to low overall energy utilization efficiency.The integrated energy system breaks the inherent mode of independent planning,independent design and independent operation of the original energy system,and carries out overall coordination,cooperation and optimization of different energy supply systems in the planning,construction and operation stage,which is the only way to improve the efficiency of social comprehensive energy use,promote the utilization of renewable energy and realize the sustainable development of energy.It is a prerequisite for its popularization and application to model and simulate the integrated energy system by means of analysis and to reveal its operating mechanism and dynamic characteristics.Unified modeling analysis of integrated energy systems is helpful to reveal the commonalities among heterogeneous energy flows,promote the understanding of power systems to other energy systems,promote the development of disciplines,and improve the efficiency of joint analysis of integrated energy systems.However,there is still a lack of basic research on the physical mechanism and modeling of integrated energy systems.The main research work of this paper is as follows:(1)Starting from the analysis of mechanical Lagrange equation,the Lagrange equation of electric system is obtained by comparing the similarity of mechanical systems and electrical systems,and on this basis,Kirchhoff law is derived.On the basis of Fourier’s law of heat conduction,the variational form is applied to the process of heat conduction,and the heat displacement field and generalized coordinates are introduced to obtain the Lagrange equation of heat conduction.The equivalent circuit of heat conduction is obtained by comparing the Lagrange equation of electrical system with that of thermal system.In this paper,the Lagrangian equation of electrothermal system is unified and the generalized Kirchhoff law is derived by means of the state parameters of thermodynamic system,namely the strong measure and the extensional quantity.The feasibility of unified modeling of integrated energy system is proved from the physical point of view.(2)On the basis of studying the waterway model and the heat route model of the heating system,the branch characteristic equation and the network topology constraint equation of the waterway model and the heat route model are derived by using the electric network analysis method,and finally the waterway and heat route network equation is obtained.A calculation method of steady-state power flow based on water and hot road network equations is designed to realize a unified modeling method of electric heating system.(3)The conclusion of this paper is verified by two simulation examples.Firstly,the steady-state power flow calculation analysis is carried out in the example of heating system based on the network equation of heating system and the calculation method of steady-state power flow,including the hydraulic calculation analysis and the thermodynamic calculation analysis.The calculation example shows the feasibility of unified modeling of integrated energy system and the correctness of the water route model.Secondly,a simulation example of the electric comprehensive energy system is built in the CloudPSS cloud simulation platform,and the feasibility of the proposed unified modeling method of the electric comprehensive energy system is verified by the simulation analysis results. |
