Visible to the public Modeling and Analysis of Cascading Failures in Interdependent Cyber-Physical Systems

TitleModeling and Analysis of Cascading Failures in Interdependent Cyber-Physical Systems
Publication TypeConference Paper
Year of Publication2018
AuthorsZhang, Y., Ya\u gan, O.
Conference Name2018 IEEE Conference on Decision and Control (CDC)
ISBN Number978-1-5386-1395-5
KeywordsAnalytical models, Cascading Failures, Communication networks, complex networks, compositionality, Cyber Dependencies, cyber-network, Cyber-physical systems, failure analysis, Human Behavior, human factors, initial flow, integrated cyber-physical systems, interdependency model, interdependent cyber-physical systems, intra-dependency, intricate dependencies, large-scale failures, Metrics, network parameters, network theory (graphs), novel interdependent system model, Numerical models, physical network, power system faults, Power system protection, pubcrawl, resilience, Resiliency, Robustness, Scalability, security of data, system robustness

Integrated cyber-physical systems (CPSs), such as the smart grid, are becoming the underpinning technology for major industries. A major concern regarding such systems are the seemingly unexpected large scale failures, which are often attributed to a small initial shock getting escalated due to intricate dependencies within and across the individual counterparts of the system. In this paper, we develop a novel interdependent system model to capture this phenomenon, also known as cascading failures. Our framework consists of two networks that have inherently different characteristics governing their intra-dependency: i) a cyber-network where a node is deemed to be functional as long as it belongs to the largest connected (i.e., giant) component; and ii) a physical network where nodes are given an initial flow and a capacity, and failure of a node results with redistribution of its flow to the remaining nodes, upon which further failures might take place due to overloading. Furthermore, it is assumed that these two networks are inter-dependent. For simplicity, we consider a one-to-one interdependency model where every node in the cyber-network is dependent upon and supports a single node in the physical network, and vice versa. We provide a thorough analysis of the dynamics of cascading failures in this interdependent system initiated with a random attack. The system robustness is quantified as the surviving fraction of nodes at the end of cascading failures, and is derived in terms of all network parameters involved. Analytic results are supported through an extensive numerical study. Among other things, these results demonstrate the ability of our model to capture the unexpected nature of large-scale failures, and provide insights on improving system robustness.

Citation Keyzhang_modeling_2018