Source - 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)
Date: November 3, 2025
File: raw/svk/the-nordic-position-on-grid-forming_publication.pdf
Pages: 10
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 defines the urgency, the technical requirements, and the staged implementation path. It is the primary public Nordic TSO statement on GFM requirements as of late 2025.
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 power fed into the grid during peak renewable penetration came through converters.
- By 2030: Converter-connected generation capacity is expected to more than double from 2022 levels.
Grid-following converters (current industry standard) rely on Phase-Locked Loops to synchronize with an existing grid signal. In a system dominated by such devices, there is a circular dependency — all devices follow each other with nothing providing a stable reference. This is the “inverter stability” problem.
Grid-forming definition
CONDON defines grid-forming (GFM) as a control strategy that enables power-electronic interfaced devices (PEIDs) to function as a controlled voltage source behind an impedance, capable of self-synchronization with the grid. This is distinct from:
- Grid-following: PLL-based current source; cannot operate without an existing reference
- Island mode: Generates voltage waveform but cannot self-synchronize with other voltage sources
Four key behaviors of a GFM converter:
| Behavior | Description |
|---|---|
| Voltage-source behavior | Maintains nearly constant internal voltage phasor immediately following a disturbance; deviation from PoC voltage drives inherent power injection/absorption |
| Inertial response | Immediate active power response proportional to RoCoF, without frequency measurement |
| Self-synchronization | Autonomously synchronizes with the grid regardless of conditions; can operate without any synchronous generators |
| Positive damping power | Inherently mitigates power oscillations through dynamic interaction between internal and PoC voltage |
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:
| Technology | Timeline | Reason |
|---|---|---|
| HVDC links | Near-term — requirements already being introduced | Custom-engineered per TSO spec; GFM specifiable from design phase |
| FACTS (STATCOMs etc.) | Near-term — requirements already being introduced | Same as HVDC; TSO-procured custom systems |
| BESS | Near-term — requirements already being introduced | Stiff DC bus makes GFM technically feasible; inherent storage capability |
| Wind/solar | Depends on EU network codes | Standardized product-based; GFM not mandatable without regulatory mandate |
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 specifications already in use:
- 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.”
These show that individual TSO specifications predate this joint position — the report harmonizes them.
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)
- German 4-TSO paper, NERC BESS white paper, AEMO voluntary spec, GB grid code GC0137 — all broadly aligned
CONDON explicitly positions the Nordic requirements within the European harmonization process (NC RfG, NC HVDC).
Testing framework
CONDON commits to developing standardized test protocols using envelope curve methodologies. 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: nearing completion
- For wind/solar: in development, timed to be ready when EU network codes arrive
Key claims
- Nordic system vulnerability is accelerating, not future — the crossing of 50% converter penetration already happened (2022)
- GFM requirements are not theoretical — they are already being introduced in Nordic TSO procurement specifications for HVDC, FACTS, BESS
- The joint position lays groundwork for common negotiation with manufacturers across all four Nordic countries
- Self-synchronization is the defining property that distinguishes GFM from both GFL and island mode
Relevance to wiki
Directly resolves all open data gaps in Grid-Forming Inverters:
- Svk timeline for HVDC specifications: already published (spec quoted in this report)
- Whether Nordic TSOs mandate GFM for specific projects: yes, HVDC/FACTS/BESS already
- EU-level harmonization: InterOPERA + ACER/ENTSO-E work underway, NC RfG/HVDC as vehicle
- Technical performance metrics: testing frameworks nearing completion; envelope curve methodology
Also relevant to Svenska kraftnät, Balancing Markets (BESS qualifying for FFR + GFM simultaneously), NordSyd (HVDC GFM requirements).