Sensitivity-Based Approach for Assessment of Dynamic Locational Grid Flexibility

In this paper, the concept of dynamic locational flexibility of a power system is introduced. A quantitative dynamic flexibility index is proposed, which reflects the effect of changing bus injections on the system small-signal stability. A mathematical expression of this index is analytically formulated to demonstrate the sensitivity of the critical electromechanical mode on bus active power loads. Further, a sensitivity-based approach for calculating the inertial distribution index and center of inertia (COI) location is also proposed. Flexibility and inertia are system-inherent properties and the relationship between the flexibility index and inertial distribution index is explored to identify the most flexible bus in the power system, where any change in loading level (within acceptable limits), or variation of power injected from renewable energy sources (RES) would have least effect on the small-signal stability of the system. Validation of these indices are done by simulation studies performed on IEEE 39-bus system and 68-bus system. Applicability and numerical performance of the proposed framework is also discussed for the Northern Regional Power Grid (NRPG) of the Indian power system.