CONDON Nordic Position on Grid-Forming (2025)

Title: The Nordic Position on Grid-Forming — Enabling the Future Nordic Power System
Authors: CONDON (the four Nordic TSOs: Fingrid, Energinet, Statnett, Svenska kraftnät)

Summary

A joint policy and technical position statement from the four Nordic TSOs establishing a common understanding of grid-forming (GFM) converter technology and coordinating timelines for its introduction across different technology categories in the Nordic synchronous area.

The report sets out the urgency, a shared general understanding of GFM behavior, and how implementation timelines differ by technology. It states that its definitions are non-exhaustive and that the TSO will still need to specify parameters; it is a position paper, not a set of binding requirements.

Context — why now

The Nordic system is crossing a threshold in converter-connected generation:

• 2022: For the first time in Nordic history, more than half of the power fed into the grid during peak renewable penetration came through converters.
• By 2030: Converter-connected generation capacity is expected to more than double (the report gives no baseline year).

Most power-electronic interfaced devices today operate in grid-following mode, using a Phase-Locked Loop (PLL) to track the voltage angle at the point of connection. The report notes that in weak grids and during disturbances such as short-circuits the PLL may struggle to track the angle, potentially compromising stability, and that converters lack the inherent ability to provide inertia or damp oscillations as synchronous generators do.

Grid-forming definition

CONDON defines grid-forming (GFM) as “typically understood” as a control strategy that enables power-electronic interfaced devices (PEIDs) to function as a controlled voltage source (within current and energy limits) behind an impedance, capable of self-synchronization with the grid. This is distinct from:

• Grid-following: PLL-based controlled current source that tracks the voltage angle at the point of connection
• Island mode: Generates voltage waveform but cannot self-synchronize with other voltage sources

Four key behaviors of a GFM converter:

The report also lists limits (additional requirements for active/reactive current outside operational limits) as a discussed requirement area.

Important caveat: GFM functionality in the absence of dedicated energy storage is limited. Converters without storage can exhibit voltage regulation and short-term dynamic response but cannot sustain active power exchange over time, limiting frequency support capability.

Technology implementation timelines

Implementation timelines vary by technology type:

The report adds that progress differs between the Nordic TSOs.

For HVDC, FACTS, BESS: testing frameworks are “complete or nearing completion” as of November 2025.

For wind/solar: test scenarios and parameters should be “fully developed” by the time future network codes are introduced, so that they can be implemented immediately on code entry into force.

Existing Nordic TSO specifications cited

The report quotes two TSO specifications as examples of definitions that align with the general understanding:

• Svenska kraftnät HVDC spec: “The GFM control mode shall enable dynamic voltage magnitude and phase control similar to a controllable voltage source behind an impedance.”
• Fingrid requirements for grid energy storage (SJV2024): “GFM shall provide autonomous, near-instantaneous frequency and voltage support by maintaining a nearly constant internal voltage phasor in the sub-transient time frame.”

The report presents these as illustrative examples; whether they predate or will be harmonized by the joint position is not stated.

International alignment

Definitions align with:

• InterOPERA (EU HVDC/PPM coordination): GFM = HVDC system or DC-connected PPM as voltage source behind impedance
• ACER/ENTSO-E: PPM shall behave as voltage source behind internal impedance (Thevenin source)
• The report says the basic definitions “largely align” and gives these examples; the German 4-TSO paper, NERC BESS white paper, AEMO voluntary specification and GB GC0137 appear only in its bibliography, not as alignment claims

CONDON explicitly positions the Nordic requirements within the European harmonization process (NC RfG, NC HVDC).

Testing framework

The report states the Nordic TSOs must develop standardized test protocols and evaluation criteria, with envelope curve methodologies given as an example (“such as”). Key goals:

• Harmonize test benches and parameters across Nordic countries to strengthen negotiating position with suppliers
• Benefit suppliers/manufacturers by removing country-by-country adaptation
• For HVDC/FACTS/BESS: frameworks “either complete or nearing completion”
• For wind/solar: test scenarios and parameters “should be fully developed” by the time future network codes are introduced

Key claims

• Converter-connected generation already exceeded half of infeed at peak renewable penetration (2022) and is expected to more than double by 2030, which CONDON says heightens system stability vulnerability
• GFM requirements are already being introduced for HVDC links, FACTS and BESS, though progress differs between the Nordic TSOs
• Harmonizing test benches and parameters is intended to strengthen the Nordic TSOs’ position when negotiating with suppliers and manufacturers
• Self-synchronization is the defining property that distinguishes GFM from both GFL and island mode

Relevance to wiki

Informs Grid-Forming Inverters on several points:

• Svk HVDC specification: one sentence quoted in this report (no timeline given)
• GFM requirements are already being introduced for HVDC, FACTS and BESS, with progress differing between TSOs (no project-level detail)
• EU-level harmonization: InterOPERA and ACER/ENTSO-E work underway, NC RfG/NC HVDC as vehicle
• Performance metrics: not specified; the report says TSOs must still specify parameters, with testing frameworks complete or nearing completion for HVDC/FACTS/BESS

Also relevant to Svenska kraftnät, Balancing Markets and NordSyd (wiki connections; this report does not discuss FFR or NordSyd).