Optimal Operation And Flexibility Assessment Of Integrated Electricity And District Heating Systems Utilizing Thermal Inertia

With high penetrations of wind power,large amounts of wind power curtailments can still occur in the traditional collaborative scheduling of integrated electricity and district heating systems(IEDHS),the ability of optimal operation and flexibility regulation between multiple energy sources in the system is facing a major test.At present,the thermal inertia of the district heating system is not considered the traditional collaborative scheduling of IEDHS,this method is lack of research on the district heating system with great flexibility potential.Some studies have proposed the use of thermal storage devices to integrate wind power to improve the flexibility absorb wind power to increase flexibility,but this method has low efficiency,high cost and insufficient flexible operation of all equipment in the system.In view of the above-mentioned issues,this paper aims to explore the underlying flexibilities which thermal inertia of district heating network and aggregated buildings can provide within the existing infrastructure can be beneficial to the further integration of wind power and reduce costs,the main research contents of this paper are as follows:1)The model of electricity subsystem and district heating subsystem in the IEDHS is established,and its operation characteristics and coupling mechanism are analyzed.The operation principle of the IEDHS and the interaction coupling relationship between the two types of energy are revealed,a detailed modeling analysis of the transmission time delay characteristics of heating network pipelines on the network side of district heating system is performed,indicating that the network side of district heating system has considerable potential for thermal storage.2)The thermal inertia model for the aggregated buildings is constructed and applied to the integrated energy systems of the industrial park,a day-ahead scheduling model for an integrated energy system in an industrial park that considers the energy storage characteristics of the cooling areas is proposed.Firstly,the energy storage model of the cooling areas based on detailed thermal model of buildings is established,and the component modeling in the industrial park is further carried out.Then,with the objective function of minimizing the total operating cost of the industrial park,s integrated energy system,the components and energy storage models are integrated into the scheduling model.Finally,the validity of the model is verified by numerical results.The results show that the energy storage characteristics of the cooling areas can effectively reduce the purchase power and operating cost,it proves that the thermal inertia of aggregated buildings is effective and combined with the heat storage characteristics of the network side of district heating system to further reduce the cost and provide flexibility for IEDHS.3)According to the relevant characteristics of EEDHS and the specific analysis of thermal inertia of district heating network and aggregated buildings,this paper proposes a eollaborative scheduling model of IEDHS with the objective function of minimizing the total operating cost and assesses the flexibility of IEDHS based on flexibility indices.Firstly,with the detailed thermal model of the aggregated buildings and the transmission time delay characteristies of heating network pipelines,a thermal inertia model of the district heating systems is proposed.Then,the optinal scheduling model of IEDHS considering thermal inertia is established.Four scheduling cases based on whether to consider the transmission time delay characteristics of heating network pipelines or the adjustable indoor temperature of aggregated buildings are designed,and a flexibility assessment method of different cases for the electricity system and coupling component is proposed.Taking into account the building parameters of different aggregated buildings,the validity of the model is verified by cases studies.Numerical results show that the proposed optimization scheduling model can make use of the heat storage capacity of district heating network and aggregated buildings,reduce operating costs,increase the flexibility of electricity system and effectively promote wind power integration.