Optimal SCUC Considering Nodal RoCoF Security Constraints in Single Generator Trip Contingencies

The rate of change of frequency (RoCoF) is a critical metric of power system frequency security. Post contingency nodal RoCoFs are not identical across a power system, with spatial characteristic significantly related to the fault size/location, network connections and parameters, as well as the system's inertia distribution state. However, most traditional security-constrained unit commitment (SCUC) strategies typically rely on aggregated frequency models, lacking necessary granularity to differentiate disparities among nodal RoCoFs. Consequently, certain generators may suffer from extremely large RoCoFs, potentially triggering unexpected pole slip protection and trip operations, even if the system's RoCoF estimated by an aggregated model remains within the allowable range. To address this issue, a nodal RoCoF security constrained unit commitment is proposed considering N-1 contingencies of any single generator trip in this letter. First, unified boundary conditions of generators are established to depict their disparate inertia response behaviors in online/offline states. Then, nodal RoCoF security constraints are further derived and embedded into an optimization problem for SCUC scheduling. Following the proposed SCUC strategy, nodal RoCoF security can always be guaranteed in any single generator trip contingencies, which is further verified by simulation results of the South East Australia Power System in different scenarios.