Preventing Outages under Coordinated Cyber-Physical Attack with Secured PMUs

Due to the severe consequences of the coordinated cyber-physical attack (CCPA), the design of defenses has gained a lot of attention. A popular defense approach is to eliminate the existence of attacks by either securing existing sensors or deploying secured PMUs. In this work, we improve this approach by lowering the defense target from eliminating attacks to preventing outages in order to reduce the required number of secured PMUs. To this end, we formulate the problem of PMU Placement for Outage Prevention (PPOP) as a tri-level non-linear optimization and transform it into a bi-level mixed-integer linear programming (MILP) problem. Then, we propose an alternating optimization algorithm to solve it optimally. Finally, we evaluate our algorithm on IEEE 30-bus, 57-bus, and 118-bus systems, which demonstrates the advantage of the proposed approach in significantly reducing the required number of secured PMUs.