Vulnerability Analysis Evaluating Bilevel Optimal Power Flow Approaches for Multiple Load Cases

This work presents two methodologies to enhance vulnerability assessment in power systems using bilevel attacker-defender network interdiction models. First, we introduce a systematic evaluation procedure for comparing different optimal power flow formulations in the lower-level problem. We demonstrate the procedure for a comparison of the widely used DC approximation and a linearized AC optimal power flow model. Second, we propose a novel scoring methodology to identify and prioritize critical attack vectors across diverse load and generation scenarios. Both methodologies go beyond traditional worst-case analysis. Case studies on a SimBench high-voltage test grid show that the DC approach fails to detect a significant portion of critical vulnerabilities. The scoring methodology further demonstrates the dependency of vulnerabilities on the considered load case and time step, highlighting the importance of assessing multiple scenarios and going beyond worst-case solutions. The proposed methodologies enhance power system vulnerability assessment and can support the effective development of robust defense strategies for future power systems.