Revealing Structural and Functional Vulnerability of Power Grids to Cascading Failures

The highly intricate inter-connectivity and ever expanding scale of modern power grids have raised serious concerns on security and vulnerability of power grids. Much of the recent study on the vulnerability of power grids to cascading failure has focused on the structural changes or functional damage of the system, and results from previous studies often draw inconsistent and even contradictory conclusions. In this paper, the causes of these diverse and inconsistent results relating to structural and functional damages have been identified. In addition, the system's vulnerability to cascading failure is studied from an attacker's perspective, and a node attack strategy maximizing structural and functional damage is considered. Specifically, the problem of finding the optimal node attack strategy is formulated as a multi-objective optimization problem, and evolutionary algorithms are used to generate optimal solutions. Simulation results on four benchmark test systems show significant advantages of the proposed algorithms over heuristic and single-objective methods, and give important insights on identifying the critical nodes affecting vulnerability of power grids.