A Hierarchical Modeling Method Of Grid Cyber Physical Systems:the Hierarchical Model And Its Application

Grid Cyber-Physical Systems(GCPS)is an interdependent multi-dimensional complex heterogeneous system which is deeply integrated with power physical system and information system.The deep coupling between physical system and information system and the synergistic interaction between energy flow and information flow in power grid bring great improvement to smart grid,at the same time,new security risks are introduced.The grid fluctuation and large-scale blackouts caused by network attacks occur frequently,so the risk factors of information space need to be taken into account in the reliability or risk assessment of power grid.It is necessary to study the fusion modeling of the information space and physical space of grid CPS.However,the grid CPS not only contains discrete computational process,but also needs to deal with the continuously changing physical events,so it is not suitable to use the modeling method of physical space in the modeling of grid CPS directly.This paper considers the complexity of the information system of grid CPS,and proposes an object-oriented hierarchical modeling method of grid CPS.The specific research contents include the following aspects:1)According to the system architecture,the complexity of information space and the fusion characteristics of information space and physical space are analyzed.2)Considering the structural characteristics of grid CPS,a hierarchical structure is proposed and it is divided into five layers:physical system layer,information service layer,information system layer,network layer and communication sub-network layer;Considering the different characteristics of nodes and links at different levels,the adjacency matrix is redefined to realize the topology modeling of grid CPS;The Markov model is improved and the object state transition model of grid CPS is established;Referring to the idea of DEVS(discrete event system specification)coupled model,the hierarchical relationship modeling of grid CPS is carried out to describe the vertical relationship between hierarchies.Finally the Grid Cyber-Physical Systems Hierarchical Model(GCHM)is established.3)On the basis of the above work,the hierarchical modeling based on GCHM is carried out for the propagation of cascading failures across space in grid CPS.And taking a provincial power dispatching data network as example to analyze the propagation process of cascading failures across space in different scenarios,and the probability of cascading failures propagation chain is calculated quantitatively to illustrate the specific application method of the model proposed in this paper.Moreover,the propagation process of the cascading failure caused by OSPF attack is simulated and analyzed,and the validity of the proposed model and its application in cascading failure modeling is verified.4)Based on the two scenarios of service reliability evaluation and situation prediction of grid CPS,the application method of GCHM in different scenarios is further explained.The hierarchical modeling method of grid CPS provides a new idea and reference method for the fusion modeling research of grid CPS.The GCHM can be used to describe the influence mechanism of various unsafe factors in information space of grid CPS,which provides an effective method support for reliability and security risk analysis of grid CPS.