The Analysis On Cyber-physical Interaction Mechanism In Cyber-physical Power Systems And Its Application

Nowadays,the smart trend of power grid and interconnection requirement of regional systems have driven traditional physical power grid to deeply depend on communication network,thus physical power grid is gradually evolving into Cyber-Physical Power Systems(CPPS)which are deeply coupled of physical power grid and communication network.Physical power grid provides communication network with continuous power energy for run,and communication network provides physical power grid with effective control commands for adjustment.On the one hand,application of advanced information and communication technologies in communication network improves the controllability and observability of physical power grid.On the other hand,the tiny failure in communication network/physical power grid can propagate to physical power grid/communication network through coupling connection.This process continues propagating between physical power grid and communication network and leads to cascading failure,causing catastrophic blackouts in CPPS.There are many blackouts happened at home and abroad,which directly or indirectly verifies the negative effect of communication network on triggering,propagating or enlarging cascading failure in blackouts.Thus,this dissertation,based on complex network theory,researches on coupling model of physical power grid and communication network,cyber-physical interaction mechanism,propagation mechanism of cascading failure,robustness evaluation,critical nodes analysis and protection strategies,which have significant meanings both in theory and reality.The main research ideas are: first,analyze the cyber-physical interaction mechanism between physical power grid and communication network,and propagation mechanism of cascading failure in CPPS;then,propose the robustness evaluation indexes;further,study the attack path of cyber attack,strategies on critical nodes analysis and redundancy protection based on above research.According to the research ideas,the research work of this dissertation is as follows:(1)Study the distribution state of isolated sub-clusters and its cyber-physical interaction mechanism of CPPS in cascading failure.First,analyze the state of CPPS in cascading failure,i.e.physical power grid and communication network are broken into abundant isolated sub-clusters,and point out that the isolating sub-clusters in CPPS can still stay alive through inter coupling connection.Further,considering the heterogeneity of nodes in physical power grid,wherein physical nodes are divided into generator nodes and substation nodes,and the sub-clusters which contain generator nodes can stay alive in isolated state.Then,the cyber-physical interaction mechanism considering the isolated sub-clusters and heterogeneity of physical nodes is proposed,and the relation between states of isolated sub-clusters and different attack scenes and coupling connection in cascading failure is attained.(2)Study the method on vulnerability of physical nodes and connectivity of CPPS.Considering the dynamics of loads on nodes/links in physical power grid and communication network in reality,the load-capacity model is introduced for quantitative analysis.Based on the dynamics of loads on nodes/links and the redistribution mechanism of loads in CPPS after failure of certain nodes/links,the overloading failure and the new round of cascading failure triggered by failure of nodes/links are analyzed,and the mechanism of cascading failure iterating between physical power grid and communication network is proposed.Meanwhile,based on the dynamics of loads in cascading failure,the load spill index is defined and the vulnerability matrix of CPPS is established,thus methods on vulnerability of physical nodes and connectivity of CPPS are proposed.Compared with traditional evaluation method on giant component,the proposed methods can effectively differentiate the influence of different failure nodes on robustness of CPPS,and can accurately describe the state of CPPS in cascading failure.(3)Study the problem on attack path of cyber attack in CPPS.Based on the cyber-physical interaction mechanism considering the isolated sub-clusters and heterogeneity of physical nodes,the model of CPPS is established,and the coupling relation between physical power grid and communication network is analyzed.First,considering the energy consumed by propagation of control commands in communication network and the probability that control commands are successfully transmitted from communication network to physical power grid,the attack cost is defined for quantitative analysis.Then,the attack gain is defined to analyze the damage on CPPS caused by cyber attack.Finally,the attack efficiency is defined to analyze the gain-cost relation between attack cost and attack gain.Based on calculating the attack efficiency of all attack paths in CPPS,the most efficient attack paths are figured out,i.e.the attack paths that attacker are in high possibility to adopt,which can provide guidance for future research on protection strategy of CPPS.(4)Study the strategies on critical nodes analysis and redundancy protection in CPPS.Based on the cyber-physical interaction mechanism of complex network theory,the model of CPPS is established,and the coupling relation between physical power grid and communication network is analyzed.Considering the heterogeneity of coupling systems in CPPS,the inter-node significance is defined to evaluate the importance of nodes in CPPS and four evaluation strategies on assessment of critical nodes are proposed.Meanwhile,the inter-difference index is defined to analyze the number of addition links and two redundancy protection strategies of addition links are proposed.The simulation results prove that the proposed evaluation strategies on critical nodes analysis can effectively evaluate the importance of nodes in CPPS,and the proposed redundancy protection strategies of addition links can largely improve the robustness of CPPS.