Research On Modeling And Multi-objective Optimization Of Integrated Energy System Based On Dynamic Supply And Demand Balance

The development of the integrated energy system(IES)has effectively avoided the disadvantages of the traditional independent energy supply system,such as decentralization and energy waste.It can meet the multiple demands of the energy use end,realize the cascade utilization of energy,improve the energy use efficiency and effectively reduce pollutant emission.In practical application,it is of great significance to build an integrated energy system based on local conditions to realize energy transformation and reduce carbon emissions in China.In this paper,a modeling method combining the energy hub method with transient simulation and a multi-objective optimization method based on the hourly dynamic balance of supply and demand in the annual energy supply cycle is proposed.At the same time,a software for transient simulation and optimization of integrated energy system is developed,which provides a method for modeling and optimization of integrated energy system.Through the analysis of two cases,it provides a reference for the selection of the operation mode of the integrated energy system and the optimization design of the system configuration in actual engineering,and verifies the rationality of the theoretical method and the practicability of the software developed in this paper.The main work finished is as follows.Firstly,a general model of comprehensive energy system and the mathematical model of each component are constructed.The modeling method using energy hub describes the energy input,distribution,transformation,storage and supply process of integrated energy system.According to the energy output form and use characteristics of various energy equipment,the transient simulation models including different energy conversion equipment--gas triple subsystem,combined heat and power subsystem,heating supply subsystem,cooling subsystem and power supply subsystem were built.Secondly,a multi-objective optimization model with the weighted sum of the annual cost saving rate,the primary energy saving rate and the shadow cost saving rate of environmental pollutants as the optimization objective function was established,and a method was proposed to avoid the subjectivity of the selection of the weighting coefficient affecting the optimization results.On the basis of TRNSYS transient simulation,the objective function of Hooke-Jeeves algorithm is used to solve the problem,so as to realize the optimization of the integrated energy system.Then,the transient simulation and optimization software of the integrated energy system is developed with the help of Matlab and TRNSYS platform.The software can simulate the transient operation process of multi-energy system,calculate and optimize the equipment ratio and its operation strategy of the integrated energy system,and provide efficient calculation tools and theoretical guidance for the construction,design,optimization and evaluation of the integrated energy system.Finally,the influence of the operation mode of the integrated energy system on the system performance and the optimization design process of the system are analyzed through a case study.The case analysis shows that the operation mode of the integrated energy system is one of the important factors affecting the performance of the system.If the electric following mode is adopted,more heat will be wasted when the electric load is large.If the heat following mode is adopted,the online power will increase and the system income will increase when the heat load is large.If there is a big difference between cooling and heating loads,different operating modes should be adopted in winter and summer to make the system achieve a better operating state.Optimization of the same equipment configuration in the integrated energy department can significantly improve the performance of the integrated energy system.In the second case,the optimized integrated energy system has obvious advantages in economy,energy saving and environmental benefits compared with the traditional distribution system and the soil source heat pump system,among which the environmental benefits are the most obvious.Compared with the separate supply system and the separate soil source heat pump system,the reduction rates of nitrogen oxides are up to 314.5% and311.8%,the reduction rates of carbon dioxide are 153.8% and 158%,the annual cost saving rates are 3.2% and 18.3%,and the primary energy saving rates are 83.7% and 73%,respectively.