Grid Resilience under high shares of Non‑Synchronous Generation: Insights from the 2025 Iberian Peninsula Blackout
S. Martín-Arroyo(1), M. García-Gracia(1), J.A. Cebollero(1), Á. Llamazares(1), O. Anaya-Lara(2) 1. Department of Electrical Engineering, EINA, Zaragoza University Campus Río Ebro, Zaragoza (Spain). 2. Department of Electronic and Electrical Engineering, Faculty of Engineering, University of Strathclyde, Glasgow, UK 2026-06-27

Abstract

This paper investigates grid resilience in powersystems with high shares of non‑synchronous generation, using the 28 April 2025 Iberian Peninsula disturbance as a real‑world case study. The objective is to characterize the dynamic mechanisms governing instability propagation under structurally low‑inertia conditions. The study integrates high‑resolution measurement analysis, dynamic event reconstruction, and a layered root‑cause framework that distinguishes the initiating network disturbance from subsequent amplification processes. Results indicate that fast inter‑area oscillations emerged in a context of reduced synchronous generation, leading to elevated rate‑of‑change‑of‑frequency (RoCoF) values and accelerated frequency decline. The interaction between grid‑following inverter‑based resources, RoCoF‑sensitive protection schemes, and constrained interconnection capacity contributed to cascading generation and load disconnections. The reduced effective inertia significantly limited the time available for corrective control actions, amplifying system vulnerability. The paper concludes that ensuring resilience in low‑inertia grids requires explicit inertia and fast frequency response adequacy criteria, deployment of grid‑forming converter capabilities, adaptation of protection settings to high‑RoCoF environments, and reinforcement of cross‑border support mechanisms. The findings provide a structured analytical basis for the design of stability services in future renewable‑dominated power systems.

Key words: Power system stability, grid resilience, low‑inertia systems, nonsynchronous generation, blackout analysis.

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