Controlled islanding using transmission switching and load shedding for enhancing power grid resilience

A controlled splitting strategy is proposed as the last resort to determine the splitting points of an interconnected power system before occurring a critical transition. The proposed strategy is expressed as a mixed-integer formulation with considering the slow coherency of synchronous generators. In the proposed integer programming formulation, each coherent group of generators is located in an individual island. This grouping constraint may assure the synchronism of generators after islanding. Each island contains a coherent group of generators and its boundary is determined with the aim of achieving minimum load shedding. Two artificial DC load flow algorithms are proposed to model grouping and connectivity constraints. In addition to operational limits, a switching constraint and a frequency stability constraint are proposed to limit the number of line switchings and assure the stability of resulted islands, respectively. The proposed mixed integer model is solved using Benders Decomposition (BD) technique. Using BD technique, the CPU time of computation is reduced significantly. The proposed splitting strategy is simulated over the IEEE 30-Bus and IEEE 118-Bus test grids. Transient stability simulations are done to validate the accuracy of the proposed method.