A tri-level optimization model for power grid defense with the consideration of post-allocated DGs against coordinated cyber-physical attacks

Abstract Due to the extensive integration of communication infrastructures, the power grid is vulnerable to a range of cyber-physical coordinated attacks. To increase the reliability of the power grid against coordinated attacks, a defensive strategy considering post-allocated Distributed Generators (DGs) is developed in this paper. The problem is formulated as a tri-level optimization model: the upper-level problem represents the action of the planner to determine the optimal plan for the defensive line and the pre-allocated DGs before attacks; the middle-level problem formulates the behaviour of the attacker in identifying the targets; the lower-level problem simulates the reaction of the defender to optimize power flow and the placement of post-allocated DGs on the remaining microgrid system. Minimizing the system load shed is the objective of this tri-level optimization framework. Furthermore, the traditional Load Redistributed (LR) attack model is reformulated in a discrete form to facilitate the utilization of duality-based method in the tri-level model. The solution process is developed based on the Nested Column-and-Constraint Generation (NCCG) algorithm with the duality-based method. Case studies are conducted on the IEEE 14-bus system and the IEEE RTS79 system and they indicate that the tri-level model and algorithm are productive and promising. In addition, a sensitivity analysis is implemented on the parameters and settings.