Efficient OPF calculations for power system reliability assessment based on state similarity

As power systems grow more complex and integrate intermittent renewable energy sources, assessing system reliability has become increasingly time-consuming. A significant challenge arises from the repetitive calculations of optimal power flow (OPF), which minimizes load curtailment. To address this, a state-similarity-based method is proposed to accelerate the OPF calculations for reliability assessment. It is based on the observation that many states in reliability assessment exhibit similar OPF solutions with identical active constraints. This similarity allows system states to be grouped into categories, with each category containing states sharing the same active constraints. For states within the same category, the optimal load curtailment can be calculated by solving linear equations instead of optimization algorithms. Furthermore, optimality conditions are employed to ensure that states are accurately matched to their respective similarity categories. Also, this method can be conveniently integrated with the impact increment and cross-entropy methods for further efficiency improvements. Case studies conducted on the RTS-79, RTS-96, and Brazilian systems demonstrate that the proposed method significantly improves computational efficiency without sacrificing accuracy, when compared with traditional methods