Grid-Forming: A New Foundation for Power System Stability

EirGrid and SONI’s All Island Grid Forming Strategy published in February 2026, sets out how grid forming (GFM) capability will be introduced across the All Island power system to maintain stability as non synchronous generation increases and conventional synchronous generation declines.

Objective of the Grid Forming Strategy

The objective of the strategy is to establish a framework to integrate GFM technologies into the All-Island power system. It highlights the benefits of shifting from synchronous generation to inverter-based resources. Currently, the reduction in online synchronous generation is negatively impacting system torque and damping. As the system shifts to inverter-based resources, the grid becomes more elastically coupled and changes in inverter current can more readily influence system behaviour, effectively “moving” the power system and increasing its sensitivity to disturbances.

With rapid growth in non synchronous generation, the system has less inherent stabilising capability, increasing the risk of frequency and voltage instability, particularly during faults, low demand periods and weak grid conditions. The strategy sets out how GFM will be integrated over time to address these risks.

Why Grid-Forming Technology Matters

GFM is highlighted as a key enabler for operating securely at high renewable penetration and for making best use of available resources.

The publication differentiates between:

• Grid Following (GFL) technologies: Respond to an existing grid signal inverters synchronised to an existing grid voltage waveform. Generally require a sufficiently strong system to operate reliably; and
• Grid Forming (GFM) technologies: Can actively establish voltage and frequency themselves. Controls can establish and sustain stable voltage and frequency when system strength is low.

Key Considerations

•  RES E capacity is forecast to rise from ~10.2 GW (2025) to ~18.6 GW (2030).
• European network codes are expected to evolve (including RfG 2.0 and HVDC 2.0) with mandatory GFM related requirements.
• System operations, regulation and funding will need to adapt as synchronous plant availability declines and renewable penetration increases.

Action Points

Implementation is phased:

1. Early adoption and trials: Voluntary GFM requirements for PPMs and HVDC projects.
2. System learning and standards: Targeted trials and operational learning to refine grid codes/testing, plus a distribution level roadmap.
3. System wide integration: Mainstream GFM across new inverter based resources and HVDC connections.

Delivery will require ongoing engagement with industry as requirements, testing and codes evolve.

Impact on Market and Business

Key non technical implications include:

• Grid Code evolution: Enhanced compliance obligations for new, and potentially existing, generators.
• System services: GFM enabled assets are likely candidates to provide future stability services.
• Investment signals: Clearer direction may reduce technology uncertainty. Focus may shift from capacity to site capability.

The overall impact will vary by role in the energy system, but the strategy is intended to be protective rather than disruptive.

Conclusion

The strategy provides a practical, phased framework for maintaining stability as renewable penetration rises, enabling learning, code evolution and wider deployment of GFM capability.

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This article has been produced for general information purposes and further advice should be sought from a professional advisor. Our Energy Sector team at Cleaver Fulton Rankin can provide you with the specialist advice you need.

For further information, please contact the Energy Sector team by clicking here.

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