Analysis of real-time frequency event in Indian power system: Quantifying frequency response reserves and effective-droop performance

In modern power systems, characterized by converter-interfaced generation and electronic interface loads, system inertia (M_sys) is declining. While existing methods primarily focus on inertia estimation, a broader understanding of its impact on frequency response is imperative. This study proposes a comprehensive approach to quantify reserve supports beyond M_sys, i.e., self-regulation (D_self) from frequency-dependent loads, governor response (FRG_ov), and effective governor-droop (R_eff.droop) performance. Using high-resolution frequency dynamics and rate of change of frequency (RoCoF) data, a Gaussian filter (GF) is applied to remove transients and detect event onset based on RoCoF triggers. The response time frames of different ancillary support mechanisms are distinguished through robust curve fitting and RoCoF analysis over the average frequency trajectory. This method provides precise time-frequency coordinates corresponding to inertia, load, and governor response time frames. The proposed method is first validated through real-time simulation on the IEEE 24-bus system using a high-fidelity real-time digital simulator (RTDS). Additionally, it is tested on nine real-frequency excursion events following renewable generation trips in the Indian power system between May 2020 and 2023. The calculated results closely align with actual system event estimates, demonstrating the effectiveness of the approach with minimal deviations. Furthermore, a case study on operational challenges arising from high renewable energy penetration in the Indian power system on August 11, 2022, is discussed.