Identifying Integer-Variable-Induced Disjointness Within Security Region Considering Unit Commitment Adjustments

The security region (SR) is an effective tool for assessing power system operational feasibility and security. However, frequent on/off adjustments of quick-start units in near real-time scale can break the fixed unit commitment assumption of traditional SR, leading to disjoint subregions and internal infeasible gaps. To address this, this letter proposes an iterative infeasible subregion identification approach, which integrates a two-stage optimization model with Farkas-lemma-based local exclusion cuts to iteratively detect and exclude infeasible subregions. Logical exclusion constraints are incorporated into subsequent iterations to prevent redundant searches until all disjoint regions are captured. Numerical studies demonstrate the method's effectiveness, precisely identifying internal infeasible regions, which occupy up to 12% of the convex relaxation in some cases, supporting secure and flexible operation.