Power system oscillations pose a significant influence on power grids and may potentially result in instability and blackouts. Traditional solutions for damping these oscillations include power system stabilizers (PSS) associated with synchronous generators and Flexible AC Transmission Systems (FACTS) devices [1,2]. However, as renewable energy sources replace conventional power plants, the PSS based on synchronous generators is no longer feasible. Consequently, damping power system oscillations in large systems, e.g. Entso-E system, with a large share of renewable energy sources is becoming a challenging task, e.g. the low-frequency oscillation before the blackout in Spain on 28.April 2025 shown in Fig. 1 [3].

Fig. 1. Power system oscillation before the blackout in Spain on 28. April 2025

Based on the measured data from Gridrada [4], this paper investigates the oscillations before the blackout in Spain and Portugal, as shown in Fig. 2.

Fig. 2. Power system oscillations before the blackout in Spain and Portugal

The study employs modal analysis to evaluate the interactions in the EU network and the eigenvalues are shown in Fig. 3.

Fig. 3. Eigenvalue analyses

The results of this paper underscore the importance of grid-forming controls of renewable generation in ensuring the reliability of modern power systems under the global energy transition.

References

[1] P. Kundur, Power System Stability and Control, McGraw-Hill Education Ltd, ISBN-10:‎ 007035958X.

[2] G. Rogers, Power System Oscillations, Springer, 978-1-4615-4561-3.

[3] https://www.linkedin.com/posts/philippe-jacquod-76227a5_time-will-tell-what-circumstance-or-chain-activity-7322729833828945920-HS44/

[4] https://gridradar.net/en