Grid-Forming Converter Deployment in Korea: From Pilot Demonstration to Market Mandate
On 28 April 2025, around midday, Spain and Portugal experienced a complete power blackout. ENTSO-E’s Expert Panel, in Grid Incident in Spain and Portugal on 28 April 2025 (March 2026), attributes the event not to a single cause but to several interacting factors — power oscillations, gaps in voltage and reactive-power control, and differing voltage-regulation practices — that drove rapid voltage rises and cascading disconnections [1]. The panel also found that the renewable share was not the cause, instead underscoring the voltage-control and stability challenges of inverter-based resources (IBR). A strikingly similar inverter-driven cascade shed 1,112 MW near Odessa, Texas, four years earlier. The common diagnosis: conventional grid-following (GFL) inverters, which track an external voltage reference, can become a systemic liability when that reference is weak or disturbed. Grid-forming (GFM) converters, which generate their own voltage and frequency reference and emulate the stabilizing behavior of synchronous machines, are now widely recognized as a necessary complement to GFL technology in high-IBR systems [2]. Korea has taken this lesson seriously.
