Research On Risk Rropagation And Defense Strategy Of CPS System Under Network Attacks Enviroment

Under the background of accelerating in the smart grid construction,cyber equipment and physical equipment interdependence gradually rise.The physical system and cyber system become into Cyber-Physical System.At the same time,with the diversification and complexity of intelligent devices constantly connected to the distribution network,the risk of the system being damaged by network attacks is increasing,which brings huge hidden dangers to the power grid.Therefore,it has great practical significance to study the risk assessment and prevention of power Cyber-Physical System under network attack.In this thesis,risk propagation and prevention strategy for Cyber-Physical System under network attack are studied.Firstly,this thesis classifies attacks launched by the network attackers from the perspective of attackers and analyses the impact of attacks.At the same time,the network attack effect in SCADA system is analysed.The dissemination process of network attack virus in the cyber system is analyzed.At the same time,the process of network attack is explained in detail and the dissemination model suitable for network attack in power CPS system is constructed.Secondly,the mechanism of cross space interaction CPS system under network attack risk is researched.The operation characteristic and structural characteristic of CPS system before the attack is analyzed.From the perspective of risk origin of CPS system,it analyzes the possible risk sources under the current operating conditions.and classify the type of risk in the CPS system.Combined with the operation characteristics of CPS system,the evolution process of risk in cross-space environment is analyzed,which paves the way for the following risk management and control.Then the process of interactive propagation of information and physical system security risk in distribution network is studied in depth.It also simulates the alternating propagation process of the physical side risk caused by the cyber side risk penetrating the boundary,which leads to the further expansion of the cyber side risk.Thirdly,building a potential attack path through association algorithm and considering the attacker's ability,the attacker's behavior and the target network's characteristics,the probability of choosing attack path is analyzed.At the same time,from the cyber side and the physical side,the impact factors of attack action layer and attack target layer are established to quantify the impact of attack on the CPS system as a whole.Combined with the above steps,the risk of potential attack path can be recognized.The level of risk caused by the attack on the power grid CPS system is estimated.The current risk level of the system is reasonably graded by the method of fuzzy comprehensive evaluation.Finally,a risk prevention framework based on intrusion tolerance technology in CPS system is proposed.The framework is a multi-stage defense system for the risk interaction mechanism and evolution process in the CPS system.The aim is to minimize the risk loss to a minimum through a multiphased defense strategy.Considering the phase characteristics of risk propagation in distribution network CPS,a safe operation state transition model considering intrusion tolerance is established.In order to detect the occurrence of key events in the process of risk evolution of CPS system as early as possible,a self-organizing critical state identification method based on the characteristics of risk development of CPS system under attack is proposed,which integrates the characteristics of physical network power flow and information network traffic flow.According to the structural characteristics of CPS,a corresponding protection strategy is established.Finally,a decision-making model of risk prevention and control strategy based on risk game is established to provide the optimal strategy combination for curbing risk propagation.