Research On Hydraulic Optimal Control Of Heating Substation Based On Model Parameter Identification And Prediction

Compared with developed countries,Chinese district heating system construction started late,and there is still room for improvement in the regulation of the heating system.With the formulation of Chinese urbanization development planning policy and the stricter requirements for urban energy consumption control,the intelligent upgrading and transformation of heating systems have become a development trend.Due to the lack of advanced control equipment,optimal regulation methods and the limitation of investment costs,the application practice of intelligent heating in my country is still in the exploration stage.There are two main problems in the regulation and control of the primary network of the heating system at the present stage.One of the problems is oversupply or undersupply,in which the heat supply does not match the demand of users.The solution to this problem depends on the accurate prediction of the critical parameters of the existing heating system.The second problem is that the regulation of each heating substation of the primary network has not been coordinated and balanced.As in practical applications,the regulators did not conduct quantitative analysis on the differences in the heating load characteristics of each heating substation.Rough control based on manual experience cannot avoid the problem of unbalanced heating,which results in the phenomenon of "near hot and far cold."For solving the above two problems,an optimal control method based on modeling and analysis of the primary network of the district heating system is proposed in this thesis.By quantifying the valve opening of each heating station in the primary network based on model calculation,the hydraulic distribution of the heating station is adjusted to optimize the heat distribution of each heating station.Then the unbalanced heating problem of "near heat and far cold" is solved.The main research content and research results of this paper are introduced as follows:(1)Firstly,the preprocessing method for the operation data of the heating system is introduced,and the outliers and missing values generated in the data collection and transmission process are eliminated and filled.Based on the load characteristics of the heating substation,a data-driven mode is established to predict the primary side return temperature considering the load characteristics of the heating substation,which lays the foundation for the optimization and control work in the following text.(2)Secondly,for the hydraulic and thermal calculation of heating substation in the primary network,this thesis establishes the mechanism model of the primary pipe network bassed on the node-branch method.It analyzes hydraulic and thermal change processes under the primary network’s steady and dynamic conditions.At the same time,the least square method is used to identify the opening coefficients of the valves of each heating substation under different openings to ensure the accuracy of the mechanism model.For engineering applications,this thesis proposes a segmented hydraulicthermal modeling method,which calculates the thermal change process in each steadystate hydraulic segment according to the valve control action of the heating substation.The flow distribution and supply temperature of the primary side are obtained using this method,which provides parameter support for calculating each heating substation’s return temperature.(3)Finally,this thesis proposes a local optimization control method of local heating stations and an overall optimal control method of the whole primary network for different application scenarios.The local optimization control method solves individual heating substations’ over-supply and under-supply problems.The heating substation’s secondary side temperature supply expectation is used as the control target.The valve opening optimization strategy is generated according to the outdoor weather changes to reduce the secondary side temperature supply deviation from the expected value.The case calculation results show that in the oversupply scenario,the average percentage deviation between the actual heat station secondary side temperature supply and the expected value is 12.48% and 1.80% before and after optimization,and the deviation is reduced by 85.6%.As for the undersupply scenario,the average percentage deviation between the actual secondary side temperature of the heating substation and the expected value was 6.18% and 1.67% before and after optimization,which means the deviation was reduced by 73.0%.As for the problem of uneven heat supply,this thesis proposes the concept of heat supply imbalance degree and quantitative calculation method,which combines Chapter 2 and Chapter 3’s research content.Additionally,using the particle swarm optimization algorithm,each valve opening in the network is optimized at each period.The case study results show that the heat supply imbalance before and after the overall optimization of the primary network are 0.81°C and 0.47°C respectively,which means the heat supply imbalance of the primary network after optimization is reduced by 42.0%.It can be seen that the optimal control strategy effectively reduces the imbalance of the primary network and improves the energy efficiency of the heating system.This thesis mainly focuses on the research on the valve control of the heating substation in the primary network of the heating system.A hydraulic optimization control method is proposed based on the modeling and analysis of the primary network of the district heating system.The research in this thesis can improve the current situation that the valve control relies very much on manual experience,and provide guidance and reference for the intelligent control of the heating substation.