Research On Heat And Power Joint Operation Optimization Based On Thermal Characteristics Of District Heating System

The purpose of this paper is to optimize the operation of the cogeneration unit by using the thermal characteristics of the central heating system to improve the flexibility of the cogeneration unit during heating period.This method aims to achieve the premise of ensuring the heating quality,improve the capacity of the cogeneration unit to participate in the peak adjustment,thus improving the utilization rate of renewable energy.This article tells the modeling principle of each module in the central heating system,and the connection between the modules.Parameter identification is used to identify unknown parameters of modules such as pipes,heat exchangers,and buildings.A central heating system in Changchun Province is used as an example.A model of central heating system that is suitable for CHP operation optimization was established.Then the heat storage,heat storage rate and the connection mode of the pipe section and the building are discussed in the central heating system.Using the central heating system model with a single user,the influence of the initial value,water electricity load flow initial value,indoor temperature limit,as well as the pipe length,pipe diameter,wall quality,wall area and the area of the radiator in buildings on operation optimization were discussed.Finally,a demonstration project of CHP operation basing on thermal characteristics of central heating system in Changchun Province was shown.The engineering process of implementation was described.Measured data are used to show the operation of demonstration project.Using a central heating system in Changchun Province as a case,through the central heating system module,hierarchical level,regional modeling method,supplemented by parameter identification,a simplified model of central heating system was established.The model is verified by the measured supply temperature and indoor temperature data of the central heating system.The calculated temperature of the heat exchange station primary side and secondary side supply water,building,the total return water of the system had almost the same change tend with measured values.The thermal conditions of central heating system can be described by this simplified model.Through the analysis of the influence of each part of the central heating system and the connection mode on the heat storage characteristics,it pointed out that the maximum heat storage capacity of central heating system is determined after the heat network is designed,and it has no relation with the regulating mode of heating.The dynamic response time constant of the heat network is closely related to the thermal network topology.The sensitivity analysis of the initial value,constraint conditions and some physical parameters in the central heating system to the operation optim ization is analyzed.It is found that initial value of electric force,initial value of water supply and constraint value of indoor temperature have great influence on operation optimization.In the analysis of the physical parameters,the physical parameters of the pipe section are more sensitive to the impact of the operation optimization than the buildings.This is related to the base of building wall quality,wall area and radiator area itself.In the demonstration project of CHP operation optimization basing on the thermal characteristics of the central heating system,indoor temperature is a rigid constraint.Under different levels of indoor temperature,outdoor temperature change and heating load plans,the indoor temperature minimum limit constraint can be satisfied.In addition,by optimizing the heating quantity of the central heating system firstly,adjusting the electric load distribution between the units secondly,the optimized thermal plan is relatively stable and has certain feasibility.