Merus Power has brought online the Nordic region’s first grid-forming battery energy storage system (BESS), a 30 MW / 36 MWh plant in Valkeakoski, Finland, built for Swiss energy company Alpiq to help stabilise a power system increasingly dominated by renewables.
The installation is the first large-scale battery in the Nordics to meet the new grid-forming requirements set by Finland’s transmission system operator Fingrid, which only published its specifications for type C and D storage units in summer 2023. The Valkeakoski project has now passed Fingrid’s full verification process, including extensive simulations and demanding field tests.
Unlike conventional grid-following batteries, which rely on an existing stable grid, grid-forming systems can independently set and maintain voltage and frequency. This allows them to stiffen weak grids, support fault ride-through and even help re-energise the network after a blackout. Their role is becoming essential as inverter-based resources such as wind and solar expand and conventional synchronous generators retire.
“Units operating with traditional grid-following control, such as wind turbines, require a sufficient amount of grid-forming capacity to function stably,” Fingrid CEO Asta Sihvonen-Punkka noted. “This first grid-forming energy storage system developed in the Nordics is an important step towards an even cleaner and more flexible electricity system. It is great to see new technological solutions like this being introduced to the power system to ensure its reliable operation and enable the growth of renewable energy in the grid.”
Developed, built and commissioned by Merus Power as EPC contractor, the Valkeakoski system uses in-house designed and manufactured power electronics and control software. The company says a strong focus on grid-forming capabilities has become central to its technology roadmap.
For Alpiq, the Finnish project is its first grid-forming storage asset and a strategic move to expand its portfolio of flexible energy solutions across European markets.
With the Valkeakoski plant now in operation, Finnish system operators and European utilities will be watching closely how grid-forming storage can anchor future networks with far higher shares of variable renewable power.
