Alternative Framework for Generator Coherency Analysis and Controlled-Islanding for Grids with High Penetration Levels of Inverter-Based Renewables

The increasing integration of inverter-based renewable energy sources has significantly altered power system dynamics and reduced inertia. Identifying coherent generators in such low-inertia systems remains a major challenge due to the dynamic influence of renewable variability. Previous research considered rotor angles and rotor speed separately. Also, the fast dynamics introduced by inverter-based renewables on power system variables make it pertinent to simultaneously consider rotor angles and rotor speed dynamics for coherency detection. Moreover, many authors have established coherency detection schemes but few have validated their methods with controlled islanding making their methods less practical for the modern grid with renewables. This paper proposes a unified coherency detection framework that combines rotor angles and rotor speeds within a dynamic state vector to capture both oscillatory and speed dynamics. An adaptive coherency threshold is computed from the geometric mean of the Euclidean distances between rotor state time series of distinct generators, allowing the threshold to adjust to changing system conditions. The framework is validated on the IEEE 30-bus system and applied to controlled islanding based on network topology and generation–load balance. The proposed framework achieved smooth dynamic responses following disturbances. These results confirm the method’s suitability for real-time application and its potential to improve resilience in modern power systems with high renewable integration.