Wind Power Integration Considering Dynamic Thermal Performance Of The District Heating System

In the "Three North" areas of China with large-scale wind power and high proportion combined heat and power(CHP)units,the CHP units are usually in the operation mode of power determined by heat during the heating seasons.The peak regulation capacity of the CHP units is restricted by the strong coupling operation constraint,which causes lack of the system flexibility,resulting in heavy wind power curtailment.Compared with the existing measures to improve the system flexibility,such as introducing energy storage and power-heat conversion devices,the dynamic thermal performance(DTP)of the pipelines network and buildings which are already existed in the urban district heating infrastructures,can be utilized to break the strong coupling operation constraint without large additional investment and with ensuring heat users' heating quality and thermal comfort by the optimal control of the CHP system,so as to further promote wind power integration.In this paper,the study is carried out as follows:Based on the analysis of basic structure of the district heating system(DHS)and main characteristics of the key components,the corresponding basic mathematical models are separately built according to the relevant principles of thermodynamics and the optimal dispatch theory of the electric power system(EPS).These models are utilized to describe the operation characteristics of electric and heat power of the heat sources(namely the CHP units),the thermodynamic characteristics,hydraulic characteristics and network topology characteristics of the district heating pipelines network,the dynamic heat balance characteristics of the heat loads(namely the buildings),as well as the heat transfer relationship among heat sources,pipelines network and heat loads.This part provides the basic models for the subsequent systematic study.Based on the contrastive analysis of the conventional operation mode of power determined by heat,and the operation mode of coordinating power and heat considering DTP of the pipelines network and buildings,the connotation of the proposed mode and the mechanism of expanding operation region of the CHP units are clarified.The combined heat and power dispatch(CHPD)models,which consider DTP of both pipelines network and buildings as well as only one of them,are formulated on the basis of the above detailed models.The dispatch models seek to minimize the total system operation cost including the penalty cost of wind power curtailment while satisfying the constraints of EPS and DHS.Compared with the conventional economic dispatch model without considering DTP.the proposed dispatch models can significantly increase wind power integration and effectively reduce the total system operation cost.Two kinds of centralized parameter simplified models,which are the model based on the equivalent to the heat storage devices and the one based on the auto-regressive distribution lag time series,are built on the basics of the detailed models for characterizing DTP of DHS considering the practical application in large-scale areas.The hierarchical CHPD mode is proposed considering that EPS is managed by centralized control and DHS is managed by decentralized control.Compared with the CHPD mode based on the detailed models,the variables number and calculation time of the proposed CHPD mode based on the simplified models can be reduced effectively,which can lighten the devices' calculation difficulty and communication pressure and the persons' cognitive burden of the electric power dispatch control center.With the background of the pilot reform for the northeast electric power peak regulation ancillary service market of China,the effect on power and heat output as well as real-time deep peak regulation ancillary service cost of the main entities in the market by the proposed measure to promote wind power integration utilizing DTP of DHS are studied.The individual benefit of each main entity and the overall benefit of the system are elaborated.Based on this,it is clarified that implementing the proposed measure can encourage the CHP units to actively participate in system peak regulation by utilizing DTP of the pipelines network and buildings at the individual level,and can furtherly realize optimal allocation of the system scarce peak regulation resources at the overall level.