ENTSO-E seeks stronger voltage-control rules

ENTSO-E is seeking changes to European connection network codes that would require all new power generation assets to support dynamic voltage control, following investigations into the 28 April 2025 blackout in continental Spain and Portugal.

The blackout affected large parts of the Iberian Peninsula for up to 16 hours and became the most severe incident on the European power system in more than two decades. ENTSO-E’s final expert panel report identified a combination of interacting factors, including oscillations, gaps in voltage and reactive power control, differences in voltage regulation practices, rapid output reductions, and generator disconnections in Spain.

Those factors led to fast voltage increases and cascading generation disconnections, causing the blackout across continental Spain and Portugal. A small area of south-west France experienced short disruption, while the wider European power system did not suffer a significant disturbance.

ENTSO-E’s proposed code changes would ensure that new generators can respond dynamically when voltage swings occur. Traditional gas-fired and conventional plants are usually capable of providing voltage support, while some renewable plants require specific equipment, settings, or regulatory obligations to provide the same service. Spain has already updated its own rules to expand voltage-control obligations for renewable plants.

The proposal reflects a technical requirement of a power system with higher levels of inverter-based generation. Renewable generation can provide voltage support when the capability is specified, connected, configured, and tested through the correct grid-code framework. Without those requirements, system operators can face a gap between the physical needs of the grid and the obligations placed on connected assets.

Voltage control is becoming more demanding as conventional synchronous generation declines and inverter-based generation grows. High shares of solar, wind, battery storage, and power electronics change how system strength, reactive power, inertia, and fault response are managed. Secure operation depends on connection standards, operational tools, data visibility, and coordination across generation, storage, and network assets.

The Iberian blackout has sharpened attention on system integration. ENTSO-E’s report covered monitoring, operational practice, data exchange, and regulatory adaptation, as well as the need to reflect local system behaviour within wider European coordination. These are practical grid management issues shaped by the changing generation mix, rather than questions of generation technology alone.

For new generation projects, stronger voltage-control requirements would affect plant design, inverter settings, control systems, compliance testing, and grid-connection processes. For system operators, they would provide a wider pool of controllable resources able to support voltage stability during fast-moving system events. For regulators, they would create a more consistent framework across European markets as renewable deployment continues.

Battery energy storage and grid-forming inverter technology are also part of the same system discussion. Batteries can contribute to system stability when configured and contracted appropriately, while inverter-based resources can provide services that previously came mainly from synchronous plant. Those capabilities have to be mandated, measured, and rewarded through connection rules, market design, and system-service procurement.

The Iberian outage has become a reference point for European grid planning because it exposed how voltage behaviour, local disconnections, and coordination gaps can escalate across an interconnected system. Updated connection codes would align new generation assets more closely with the operating requirements of a lower-carbon grid, where voltage support, reactive power, and fast control are no longer peripheral services.