Modeling And Analysis Of Optimal Energy Flow In Combined Heating And Electrical Multi-Energy System Considering The Linenr Network Constraints

Under the background of the global energy Internet and the widespread use of renewable energy,the interconnection of multiple energy supply networks and the coordinated transformation of multiple energy forms are becoming a new trend.The district heating network is one of the possibilities to realize the integrated utilization of the power grid and the multi-energy flow system,and has become an important part of the sustainable development energy system at home and abroad.With the increase using of heating-electrical coupling components worldwide,the connection between the electrieal network and the district heating network is closer,so it is important to formulate and model the heating network and electrical network as a whole.This paper focuses on the analysis of network transmission characteristics and the topology of combined heating and electrical network.A fast linearized matrix formulation of the integrated heating-electrical network is established and its optimal energy flow is analyzed where the parameters of the heating network are optimized.To some extent,it fills the vacancy of systematic topology analysis method of the multi-energy system in the existing literature.The heat medium and energy distribution in the heating network are analyzed,and the thermodynamic formula is linearized and approximated.The topology of heating network is analyzed in detail and the node-pipe incidence matrix,loop-pipe incidence matrix and temperature coefficient matrices are constructed.Systematic matrix formulation is pursued and the coefficient matrices can be modified rapidly according to different types of topology,which proves strong applieability in all types of heating networks.The load model of the district heating network is analyzed and modelled,and a parameter optimization method considering demand response is established from the perspective of satisfying the heating balance.Under the condition of insufficient energy supply or extreme weather,the difference in discomfort of users is reduced through the centralized control and optimization of the load-side parameters,which improves the overall heating benefit and the heating supply balance is achieved.Then the optimal operating point of the load side in the energy flow calculation is obtained.In order to realize the linear programming of the combined heating and electrical network,the linearization methods of power system are studied.The classic DC power flow model is one of the most widely used linear models for its fast calculation,but it ignores the voltage magnitude and branch power losses.Hence several linear power flow models are introduced in this paper.A linearized decoupling method is proposed based on DC model and the matrix formulation is pursued,which simplifies the calculation process.Then the idea of network losses equivalent power is used to construct an improved linear decoupled equivalent power flow model.In case studies,different linearized power flow models are compared and analyzed in aspect of the completeness of power flow information,calculation accuracy,calculation efficiency and application scenarios.A comprehensive energy supply system including CHP,heat pump and the circulation pump is established as the heating-electrical coupling component to construct the comprehensive model formulation of the combined heating and electrical network.The traditional non-linear algorithm(Newton-Raphson method)and linear programming method are used to solve the optimal energy flow model of combined heating and electrical network.On the basis of ensuring the calculation accuracy,transforming the non-convex,non-linear problem into a linear programming problem can greatly improve the computational efficiency,reduce the calculation time and the potential convergence problem which may exist in the traditional algorithm is avoided.