50 research outputs found
Mitigating Cascading Failures in Interdependent Power Grids and Communication Networks
In this paper, we study the interdependency between the power grid and the
communication network used to control the grid. A communication node depends on
the power grid in order to receive power for operation, and a power node
depends on the communication network in order to receive control signals for
safe operation. We demonstrate that these dependencies can lead to cascading
failures, and it is essential to consider the power flow equations for studying
the behavior of such interdependent networks. We propose a two-phase control
policy to mitigate the cascade of failures. In the first phase, our control
policy finds the non-avoidable failures that occur due to physical
disconnection. In the second phase, our algorithm redistributes the power so
that all the connected communication nodes have enough power for operation and
no power lines overload. We perform a sensitivity analysis to evaluate the
performance of our control policy, and show that our control policy achieves
close to optimal yield for many scenarios. This analysis can help design robust
interdependent grids and associated control policies.Comment: 6 pages, 9 figures, submitte
Structural transition in interdependent networks with regular interconnections
Networks are often made up of several layers that exhibit diverse degrees of
interdependencies. A multilayer interdependent network consists of a set of
graphs that are interconnected through a weighted interconnection matrix , where the weight of each inter-graph link is a non-negative real number . Various dynamical processes, such as synchronization, cascading failures
in power grids, and diffusion processes, are described by the Laplacian matrix
characterizing the whole system. For the case in which the multilayer
graph is a multiplex, where the number of nodes in each layer is the same and
the interconnection matrix , being the identity matrix, it has
been shown that there exists a structural transition at some critical coupling,
. This transition is such that dynamical processes are separated into
two regimes: if , the network acts as a whole; whereas when , the network operates as if the graphs encoding the layers were isolated. In
this paper, we extend and generalize the structural transition threshold to a regular interconnection matrix (constant row and column sum).
Specifically, we provide upper and lower bounds for the transition threshold in interdependent networks with a regular interconnection matrix
and derive the exact transition threshold for special scenarios using the
formalism of quotient graphs. Additionally, we discuss the physical meaning of
the transition threshold in terms of the minimum cut and show, through
a counter-example, that the structural transition does not always exist. Our
results are one step forward on the characterization of more realistic
multilayer networks and might be relevant for systems that deviate from the
topological constrains imposed by multiplex networks.Comment: 13 pages, APS format. Submitted for publicatio
Interdepedency modeling of cyber-physical systems using a weighted complex network approach
This paper introduces a three-dimensional weighted Complex Network Theory (CNT) model to study the dependency and interdependency of cyber-physical systems (CPS) and to identify the most critical and vulnerable components within the coupled network. Based on CNT, the electric power buses within power system and communication routers and multiplexers within communication network are modelled as nodes, while the power lines and communication channels are modelled as edges. The intrinsic properties of electric power system (e.g. power flow) and the communication network (e.g. gross bitrate) are assigned as weights to each edge. A novel CNT-derived index, Vulnerability-weighted Node Degree (VWND), has been developed and applied to assess the dependency/importance of each physical/cyber node to its own and to the other system and such to help identify potentially weak areas of the system. The approach is illustrated on a 14-bus synthetic power distribution network with supporting Information and Communication Technologies (ICT)