A Key Nodes Mining Algorithm For CPPS Cyber Layer

Under the background of energy internet,modern power system has gradually evolved into a system that is coupled by a physical power grid and an information network,called the Cyber Physical Power System(CPPS).The computing,communication and control functions of the cyber network have significantly improved the information perception,integration,and sharing capabilities of the CPPS,but also Introduced new vulnerabilities.In the "N-K" failure caused by information attacks,the simultaneous failure of a few key nodes may lead to cascading failures,causing the system to crash quickly.Therefore,accurately locating key nodes in the cyber layer and strengthening their ability to resist risks are of great significance to avoid large-scale power outages and enhance the robustness of CPPS.The difficulties in mining the key nodes of the CPPS cyber layer are: on the one hand,the dynamic models used by the existing algorithms only consider the structural characteristics of the single-layer network,and ignore the influence of the interlayer effects of coupling network on the fault propagation process,so they are not applicable to the CPPS;on the other hand,due to the interconnection of power systems strengthening,the system scale is continuously expanding,making the time overhead of obtaining key nodes through direct traversal too long.In order to obtain a key nodes mining algorithm that is applicable for CPPS and has both accuracy and efficiency,the main work of this thesis is as follows:1.The CPPS cascading failure model considering the operating characteristics of the cyber layer is constructed.Firstly,this thesis analyzes the influence mode of cyber layer nodes failure on the physical layer,so as to clarify the interaction mechanism between the cyber layer and the physical layer.Then,the propagation process of the failure in the CPPS system is modeled,which considers the effect of upstream and downstream information transmission delays on the stability control commands validity,to achieve an accurate description of the cascading failure development process of the CPPS;Finally,according to the physical layer load loss rate,the cyber layer nodes influence is evaluated to ensure the accuracy of the overall algorithm.2.Drawing on the existing community-based heuristic search ideas,a key nodes mining algorithm for the CPPS cyber layer is proposed.Firstly,this thesis integrate the network information of each layer of the CPPS system,the concept of label relevance is defined,and communities are discovered based on the closeness of node communication to avoid the problem of unstable community discovery results caused by random label selection.Then,the potential influence of the candidate nodes is evaluated based on multi-level comprehensive indicators to filters the candidate nodes in the community,thereby reducing the search space,the number of cascading failure simulations and the time complexity of algorithm.Finally,this thesis uses the cascading failure model to evaluate the failure influence of candidate nodes and completes the mining of key nodes.3.The effectiveness of the algorithm in this thesis is verified.The experimental results show that using the cascading failure model proposed in this thesis to measure nodes influence has good accuracy and high discrimination.This model can be used as the basic dynamic model of key nodes mining algorithm.In addition,compared with the existing key nodes mining algorithm,the algorithm proposed in this thesis can improve efficiency and ensure the accuracy of results.The overall performance of the algorithm is better,and it can be applied to large-scale CPPS systems.The work in this thesis provides a reference for further protecting the key nodes of the CPPS cyber layer,and helps to build a safe and reliable energy internet.