Cyber-Security Constrained Placement of FACTS Devices in Power Networks From a Novel Topological Perspective

Optimal placement of flexible AC transmission systems (FACTS) devices and the cyber-security of associated data exchange are crucial for the controllability of wide area power networks. The placement of FACTS devices is studied in this paper from a novel graph theoretic perspective, which unlike the existing approaches, purely relies on topological characteristics of the underlying physical graphs of power networks. To this end, the maximum matching principle (MMP) is used to find the set of required FACTS devices for the grid controllability. In addition, the cyber-security of the most critical data related to the FACTS controllers is guaranteed by introducing the concept of moderated-<inline-formula> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula>-security where <inline-formula> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> is a measure of data obscurity from the adversary perspective. The idea of moderated-<inline-formula> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula>-symmetry is proposed to facilitate the arrangement of the published cyber graph based on a permutation of nodes within the symmetry group of the grid, called generator of automorphism. It is then verified that the published cyber-graph can significantly obscure the data exchange over the cyber graph for adversaries. Finally, a similarity is observed and demonstrated between the set of critical nodes attained from the symmetry analysis and the solution of the FACTS devices placement that further highlights the importance of symmetry for the analysis and design of complex power networks. Detailed simulations are applied to three power networks and analyzed to demonstrate the performance and eligibility of the proposed methods and results.