The 28 April 2025 blackout in the Spanish interconnected power system from a converter-technology perspective and the need for grid reinforcement

Abstract

The rapid growth of inverter-based renewable generation is changing the stability constraints of modern power systems. The Iberian blackout of 28 April 2025 provides a critical case for examining this transition. This study links converter behaviour, published laboratory experiments, reported event ordering and engineering reinforcement options. Public system-level records are consistent with voltage-led propagation: voltage excursions and generation disconnections preceded the steepest frequency decline under low demand, high photovoltaic output and reduced synchronous support. This interpretation does not constitute a full dynamic reconstruction or identify every initial trip cause. Spain continued renewable deployment: year-end installed power capacity reached approximately 142.6 GW, including storage but excluding self-consumption facilities, and renewables supplied 55.5% of generation excluding estimated self-consumption. The engineering assessment distinguishes static synchronous compensators (STATCOMs), extended STATCOMs with energy storage (E-STATCOMs) and high-voltage direct-current (HVDC) links. The Mehrum Nord E-STATCOM illustrates transmission-scale integration of dynamic reactive-power support, short-duration active-power exchange and grid-forming control. Manufacturer-reported capabilities include ±300 Mvar and a 200 MW supercapacitor unit; these ratings do not establish that the installation would have prevented the Iberian blackout. The findings indicate that renewable-rich systems require coordinated voltage-control margins, dynamic reactive-power resources, electrical reference formation, short-duration active-power support and protection, alongside adequate generation and operational flexibility. Converter behaviour is used to assess the propagation of the Iberian blackout. Reported timing supports voltage-led propagation before the steepest frequency fall. Low demand and reduced synchronous support characterised the pre-event state. Spain’s 2025 deployment and reforms inform the engineering response. Mehrum Nord combines reactive-power support with stored-energy response. Converter behaviour is used to assess the propagation of the Iberian blackout. Reported timing supports voltage-led propagation before the steepest frequency fall. Low demand and reduced synchronous support characterised the pre-event state. Spain’s 2025 deployment and reforms inform the engineering response. Mehrum Nord combines reactive-power support with stored-energy response.