Research On Key Technologies Of Modeling And Analysis Of Smart Substation Cyber-Physical System

With the development of computer technology,network technology and communication technology,digital and smart substation has been widely built and applied.The application of intelligent electronic device and the network process of substation operation function makes the physical system and cyber system of substation closely combine and cooperate with each other,forming a typical cyber-physical system.The stable operation of various functions in the substation is affected by the uncertain communication delay induced by the information network transmission process.More seriously,the substation functions will fail when the network is attacked by the outside world,even endangering the safe operation of the power grid.At present,there are many researches considering the effects of network delay on the power system using simulation methods or actual data statistics.However,the analysis of time delay inducement factors and their influence is not enough.There still lacks the exact mathematical expression of the randomness of the delay.In the aspect of network delay,existing researches mostly focus on analyzing the influence of various factors on network delay,and usually ignore the physical factors generating the delay,which makes the simulation results pay much attention to the stochastic characteristics caused by non-network factors,and cover up the stochastic characteristics caused by the physical structure.Therefore,this dissertation takes the network delay of smart substation cyber-physical system as the research content,focusing on the modeling method,network performance evaluation and network scheduling strategy considering network attacks,etc.The main research content is divided into four parts:(1)An information network communication modeling method based on the smart substation architecture of “three-layer two-network” is proposed.The smart substation information network is modeled of three important parts: network topology,information data flow and network strategy.Based on the scale-free characteristics of smart substation information network topology,an adjacency matrix model of smart substation information network is established.Then the information data flow is divided into three categories according to their transmission mechanism,namely periodic information data flow,stochastic information data flow and burst information data flow.The network strategy is modeled based on the network topology in this dissertation.The above three parts together constitute the smart substation information network model to lay a foundation for the follow-up research.(2)A mechanism analysis method of communication delay stochastic characteristics based on the queuing theory is proposed and a method of communication delay distribution characteristics based on the Monte Carlo simulation is studied.Based on the topology of communication network and network nodes,the mechanism of delay generation is analyzed,and the characteristic curve of delay distribution is estimated by the Monte Carlo simulation method.Comparing the simulation data with the experimental data,the validity of the proposed method is verified.The effect of stochastic communication delay on smart substation operation is analyzed by using the results.(3)The influence analysis of network topology of smart substation information network based on the Floyd-Warshall algorithm is proposed.The influence of network topology on smart substation is evaluated by constructing the network response to network storm cost parameter,which is congestion response cost.Simulation analysis under different network topologies verifies the effectiveness of network impact analysis based on the Floyd-Warshall algorithm.(4)The network smooth strategy of smart substation network based on delay locked loop(DLL)strategy is proposed.Due to the real-time and reliability requirements of smart substation are contradictory,considering the network jamming phenomenon caused by possible network attacks in the network,a widely effective network smooth strategy is proposed.Based on the digital modeling of the information forwarding process,the numerical value of information in advance or lag is obtained,and the time difference is compensated by the principle of DLL,so as to achieve the goal of a stable communication network.Multiple simulation results verify the effectiveness of the proposed network smooth strategy.