Research On Optimal Scheduling Method For Integrated Electricity And District Heating Systems Considering Wind Power Uncertainty

For the past few years,with the continuous growth of energy demand,energy shortages and environmental issues have become increasingly severe.The clean energy has become promoting the innovation and transformation of the energy industry due to the non-renewable nature of fossil energy.Therefore,the combination and complementarity of energy systems are regarded as effective ways to increase energy efficiency and promote renewable power integration.Integrated energy system(IES)becomes an important form of energy society in the future.On this basis,in order to consider the structural characteristics of the actual heating network and cope with the uncertainty problem of wind power,a reasonable heating network model and an optimal method to solve the uncertainty problem are urgently needed to participate in the integrated electricity and district heating system(IEDHS).Under the background of this subject that above mentioned,the main work in this paper are as follows:First of all,the research status of IEDHS and uncertainty optimization is described,and the network model and modeling method of electricity power system and district heating system in IEDHS are explored,the structural characteristics and energy characteristics of each system are elaborated,and the coupling and complementarity relationship between the energy systems is revealed.Secondly,through the analysis of electricity-heat coupling relationship(combined heat and power units),considering the transmission delay characteristic of a heating network,an optimal scheduling model of an IEDHS is formulated to minimize the total IEDHS operation cost is established;and the uncertainties of both wind power and electricity and heating loads are described with interval numbers.Then an interval optimal scheduling model of an IEDHS is formulated,and the model is solved to obtain the optimal results by two-stage decomposition.Case studies are performed on PJM 5-bus electricity system with a 6-node district heating system and IEEE-39 bus power system and 6-node district heating system,and the IEDHS considering the transmission delay characteristic of the heating network is analyzed.The results demonstrate that the transmission delay characteristics of the heating network can accommodate more wind power,enlarge the width of the interval cost and minimize the IEDHS operation cost.The practicability and effectiveness of the proposed model and the rationality of applying interval optimization method are further verified by case studies.Finally,combining robust optimization with wind power forecast output interval,an optimized scheduling model of robust intervals for the IEDHS is constructed and the duality theory is applied to transform the model into a single level model,and CPLEX solver is used for solution.Based on the optimal scheduling model of IEDHS,and the power output,heat output and wind power output in the IEDHS is determined.The influence of the transmission delay characteristic of the heating network on wind power utilization is further analyzed.An IEDHS consisted of a PJM 5-bus testing system with a 6-node district heating system and an IEEE 39-bus testing system with a 12-node district heating system is used for analyzing and verifying validity of the proposed model.The result indicates transmission delay of the heating network can improve use ratio of wind power and reduce system operation cost.Meanwhile,optimized scheduling result of robust intervals is more reliable compared with that of conventional scheduling.