Research On Identification Of Vulnerable Links And Protection Strategy In Integrated Energy System Based On Complex Network Theory

With the increased energy and environmental problems in the world,how to change the traditional mode of energy supply and realize the clean and efficient use of energy has become the focus of people’s research.The Integrated energy system integrates various energy sources such as cold,heat,electricity and gas,and can realize comprehensive management and unified dispatching of various energy sources.It is an important direction for the development of energy supply system in the future.At present,research on integrated energy systems is mainly concentrated in modeling and simulation,power flow calculation,operation control and so on,but the identification of vulnerable links and protection of integrated energy system are seldom studied.However,like electric power system,integrated energy system,as an important social infrastructure,will also be damaged by natural disasters or man-made attacks.Therefore,it is necessary to study the vulnerability of integrated energy system,including identification of vulnerable links and related protection measures.In view of this,based on the complex network theory,this paper puts forward the identification index of the vulnerable link of the integrated energy system,and on this basis,carries on the protection strategy research and analysis of the integrated energy system.The main research contents are as follows:(1)The complex network model of integrated energy system is constructed.The structure and key coupling links of integrated energy system were analyzed,and the complex network model of the integrated energy system based on energy hub has been built.Based on the complex network modeling and the complex network characteristics analysis,it is found that the system belongs to the scale-free network,and more likely there are vulnerable links,which provides a rational basis for the subsequent identification of vulnerable links.(2)An identification index of vulnerable link of integrated energy system based on complex network is proposed.Combined with the nature of interconversion of energy in the integrated energy system,the weighted weighted line betweenness index of the power system is improved,and the identification index of vulnerable nodes and lines of the integrated energy system is proposed.The effectiveness of the proposed index is verified by simulation on the established complex network model of integrated energy system,and it is proved that the proposed index can identify the vulnerable link which cannot be identified by the traditional betweenness index.(3)Based on the cost constraint,this paper studies the protection strategy which comprehensively considers physical protection,adding spare stations/lines and adding extra lines.A protection decision optimization model with the goal of minimizing the expected loss of weighted betweenness under attack is established for integrated energy systems,and it is transformed into a bi-level decision optimization model solved by the hybrid algorithm of genetic algorithm-Cplex.Firstly,the model is solved and it is found that protect the nodes and lines with high weight betweenness first have a greater improvement on the robustness of the system.The simulation results show that line addition can greatly improve the system’s ability to resist random line damage,and protection decision line addition can significantly improve the system’s ability to resist deliberate line damage.Finally,the effects of different protection methods on the robustness of the system are analyzed.The results show that multiple protection methods are more effective than single protection method,especially physical protection or spare protection based on line addition.