Research On Modeling And Operation Optimization Of Heat And Electricity Integrated Energy Systems

With the increasing exhaustion of fossil energy and the increasingly severe environmental problems,it has become an inevitable choice in the energy field to improve the comprehensive utilization efficiency of energy,reduce pollution gas emissions,and develop efficient,clean,and renewable new energy systems.Integrated energy systems(IESs),with the power system as the core,integrate various kinds of energy,such as gas and heat,and rely on the continuous innovation of cogeneration equipment,energy conversion equipment,renewable energy generation,and other related technologies,which can achieve a high degree of coordination of different aspects including multiple energy production,transmission,distribution,utilization,and storage.IESs have significant advantages in improving energy utilization efficiency and promoting renewable energy consumption,and hence have received lots of attention from academia and industry.Compared with the traditional independent energy systems,IESs has the following advantages: 1)The joint analysis and control of multiple energy systems can be achieved,which effectively improves the operational security and stability of energy systems;2)The coordinated planning and operation of heterogeneous energy systems can be realized,which can effectively reduce energy cost and pollutant emission and bring economic and environmental benefits that cannot be achieved by independent planning and operation;3)The energy systems,such as the natural gas system and district heating system,can provide considerable flexibility for the power system operation,promote the renewable energy consumption,and help the development of high proportion of renewable energy power systems.However,the dynamic characteristics of multiple energy carriers in IESs are complicated,the time scale differences are significant,the coupling of multiple energy carriers presents strongly nonconvex characteristics,and the system operation environment is complicated.Therefore,there are many challenges in the modeling and cooperative operation of IESs.This thesis focuses on the safe and economic operation of heat and electricity IESs,systematically analyzes the physical characteristics of energy flow,operation and control requirements,and complicated operation environment,and summarizes the critical challenges faced by the efficient and economical operation of IESs from two aspects of analysis and calculation.Based on this,a series of research is carried out from the thermal inertia modeling and the cooperative optimization algorithm,which provides systematic theoretical and technical support for the modeling and operation optimization of heat and electricity IESs.The main contents of this thesis are summarized as follows.1)High-resolution modeling of thermal inertia in IESs.Aiming at the dynamic process of thermal inertia in the district heating network and buildings,the influence of thermal inertia dynamic errors on the operation and control of IESs is systematically analyzed.Based on this,several key indices are developed to quantify the influence of thermal inertia dynamic errors,and a time resolution selection procedure based on the "operation decision & simulation evaluation" framework is proposed for thermal inertia.Furthermore,to realize the precise coordination of heat and electricity,a high-resolution optimization method is proposed for IESs to ensure efficient and economical operation.This work provides a generic framework for the high-precision thermal inertia modeling and operation optimization of IESs.2)Thermal inertia aggregation model of IESs.Aiming at the thermal inertia analysis and optimization problem of IESs,an equivalent model of the district heating network and the synchronous response model of buildings are proposed,respectively,and then the thermal inertia aggregation model is developed.Next,the equivalent thermal battery model is proposed by extending the thermal inertia aggregation model,which reveals the physical essence of thermal inertia energy storage capacity.Furthermore,the properties of the model are analyzed and proved,and several key theorems are presented to prove the generality and scalability of the model,which also provide theoretical support for the application of the model in analysis and optimization problems.Simulation results show that the proposed model greatly reduces the computational complexity of the optimization problem.This work provides a mathematical model with concise mathematical form and clear physical meaning for the district heating network and buildings,which can directly reflect the relationship between the input,output,and internal state of district heating system,and provides a good model basis for the analysis,planning,and operation of IESs.3)Cooperative optimization of electricity-heat-hydraulics in IESs based on convex optimization.Aiming at the cooperative operation optimization of the electricity,heat,and hydraulics in IESs,a high-dimensional nonconvex cooperative operation optimization model with nonlinear constraints and quadratic equality constraints is developed,and a second-order cone relaxation model based on model reconstruction and convex relaxation is proposed.To recover the feasible solution for the original nonconvex model,a model with the penalty function is developed,and a feasible solution recovery algorithm is proposed based on the convex-concave procedure method.Furthermore,to improve the convergence performance of the algorithm,an enhancement model is constructed,and the locally optimal solution of the original nonconvex model is quickly obtained through the iterative solution of the model.Finally,the relationship between the models and the convergence performance of the algorithm are analyzed.The proposed method provides an algorithm basis for the cooperative optimization of electricity,heat,and hydraulics in IESs.4)Operation optimization of IESs in an uncertain environment with robust thermal comfort control.Aiming at the complicated uncertainties in the operation of IESs,the uncertainties related to the users’ thermal comfort and power system operation are analyzed and modeled,respectively.Based on the stage characteristics of the forecast information of uncertain factors,a two-stage adaptive robust optimization model is proposed for the operation decision of IESs,which can cooperatively optimize the system security,economy,and thermal comfort of users.A sampling-based approximation method is proposed to convert the model into a min-maxmin problem,which is then solved by the column-and-constraint generation method.This work integrates a robust thermal comfort control strategy in the operation decision problem of IESs,which provides an effective solution to the operation decision problem of IESs under various uncertain factors.