Source - ACER Recommendation 03-2023 NC RfG DC (2023)

ACER Recommendation No 03/2023 — Reasoned proposals for amendments to Commission Regulation (EU) 2016/631 establishing a network code on requirements for grid connection of generators (NC RfG) and Commission Regulation (EU) 2016/1388 establishing a network code on demand connection (NC DC) Adopted: 19 December 2023 File: raw/ACER_Recommendation_03-2023_NC_RfG_DC.pdf

Annexes (published separately on ACER website):

• Annex 1: Amended NC RfG regulation text (clean)
• Annex 1a: Amended NC RfG regulation (tracked changes vs original)
• Annex 2: Amended NC DC regulation text (clean)
• Annex 2a: Amended NC DC regulation (tracked changes vs original)
• Annex 3: Policy paper
• Annex 4: Reasoning to proposed NC RfG amendments
• Annex 5: Reasoning to proposed NC DC amendments
• Annex 6: Evaluation of public consultation PC 2023/E/08 (NC RfG)
• Annex 7: Evaluation of public consultation PC 2023/E/07 (NC DC)

Document metadata

• Type: ACER formal recommendation to the European Commission
• Legal basis: Arts. 59(1)(b) and 59(6) Regulation (EU) 2019/942 (ACER Regulation)
• Scope: Proposes amendments to two grid connection network codes: NC RfG (EU 2016/631) and NC DC (EU 2016/1388)
• Note on filename: “DC” stands for “Demand Connection” — this is the combined NC RfG + NC DC recommendation. It is not about DC (direct current) or DC-connected power park modules specifically.
• 8 pages main body + 7 annexes including full amended regulation texts
• Preceded by: Two public consultations in autumn 2022 (PC 2023/E/07) and summer 2023 (PC 2023/E/08); policy paper (Annex 3); amendment process initiated spring 2022. 94 consultation responses received (56 for NC RfG, 38 for NC DC) from 62 stakeholders.

Summary

ACER submitted this recommendation to the European Commission after a two-year amendment process. It proposes comprehensive updates to both grid connection network codes to address three structural changes in the EU power system: (1) the mass deployment of electricity storage, (2) the growth of V2G-capable electric vehicles, and (3) the shift from synchronous to inverter-based generation.

The most important single change is the removal of the energy storage exclusion (Art. 3.2(d) of EU 2016/631), which explicitly brings BESS and other electricity storage systems into the scope of NC RfG for the first time at EU level. The recommendation also introduces mandatory grid-forming capability obligations for new inverter-based assets above certain thresholds — directly addressing the stability implications of declining synchronous inertia.

Legislative status

ACER submitted this to the European Commission for comitology (formal amendment procedure under Art. 55 Regulation 2019/943 / Art. 59 ACER Regulation). The Commission has not yet adopted the amendments into law as of 2026. During the comitology process, ACER advises the Commission through Grid Connection European Stakeholder Committee (GC ESC) workstreams established in mid-2024. Industry timeline estimate: full application “by end of this decade” (approximately 2027–2030), with a 3-year implementation period running from EC publication.

The recommendation is referred to in industry discussions as “NC RfG 2.0” or “CNC 2.0” (Common Network Code 2.0).

Key NC RfG amendments proposed

1. Electricity storage — explicit scope inclusion (removes Art. 3.2(d) exclusion)

Current position: EU 2016/631 Art. 3.2(d) explicitly excludes kraftlagringsenheter (energy storage units) from RfG scope, except pumped hydro. No RfG-based requirements apply to BESS — no fault ride-through, no frequency response obligations, no fault current injection requirements. Swedish practice classifies BESS operating in production mode as kraftparksmoduler and applies PPM requirements by interpretive convention, but this has no binding statutory basis.

Proposed change: Electricity storage systems are explicitly brought within scope. Requirements apply to both “input” (charging) and “off-take” (discharging) modes. This is the first time EU-level mandatory technical connection requirements would apply to grid-scale BESS.

Netherlands precedent: Netherlands had already incorporated storage in its national RfG implementation ahead of this EU-level change.

Auxiliary storage carve-out: Electricity storage integrated solely to meet another module’s requirements (e.g., a buffer within a wind turbine controller) is considered part of that module and its capacity does not count toward the significance (type classification) threshold.

2. Grid-forming capability — new mandatory requirement for Type B/C/D

Type B, C, and D Power Park Modules (PPMs) — including newly in-scope BESS — must provide grid-forming support: voltage source behaviour, voltage support, and inertia support. The threshold is ≥10 MW or connection at ≥110 kV.

This requirement is a direct response to the loss of synchronous inertia as thermal and hydro generators are displaced by inverter-based resources. Under the current NC RfG (EU 2016/631) and EIFS 2018:2, FSM (frekvenskänslighetsläge) provides reactive frequency response for types C/D, but there is no grid-forming obligation. Grid-forming goes further: it requires the inverter to act as a voltage source rather than a current-follower, enabling autonomous voltage and frequency stabilisation.

ENTSO-E published its Phase II technical report on grid-forming requirements in November 2025, outlining specific implementation specifications for the comitology process.

Microgrid relevance: The inverter current limitation problem documented in Source - Energiforsk 2023-957 Felbortkoppling i Mikronät (2023) and Source - Lund Arholma Microgrid Fault Detection (2025) (≤2 p.u. fault current from grid-following inverters vs ~6 p.u. from synchronous generators) arises precisely because current inverters are grid-following rather than grid-forming. A mandatory grid-forming requirement for large BESS would, over time, raise the fault current contribution from new inverter installations at threshold scale.

3. RoCoF ride-through requirements for storage

Storage systems must withstand rate-of-change-of-frequency events without disconnecting:

These complement the existing frequency range stay-connected requirements and are designed for plausible European grid disturbance scenarios.

4. Electric vehicles and V2G — scope inclusion

V2G-capable electric vehicles and EVSE (electric vehicle supply equipment) that export power to the grid are brought within NC RfG scope. Requirements apply to the bidirectional power export function.

Significance threshold: V2G EVs and EVSE below 1 MW are treated separately from other PPMs for type classification — individual V2G units below 1 MW are not classified as type B/C/D PPMs. This practical threshold reflects the very small individual capacity of consumer EV installations.

5. Type A/B threshold: no change — type A gaps remain

ACER considered lowering the type A/B threshold from 1 MW (Nordic NRA threshold: 1.5 MW) but reverted to keeping 1 MW unchanged. The type A generator gaps identified in Source - Energiforsk 2023-957 Felbortkoppling i Mikronät (2023) — no LVRT requirement, no fast fault current injection requirement — are not addressed by this recommendation. Most small DERs (rooftop solar, small BESS, small wind) remain in type A with no new RfG-based technical obligations under NC RfG 2.0.

6. Negative sequence injection: not addressed

The gap identified in Generator Connection Requirements › Regulatory gaps for microgrid applications — no EU/Swedish requirement for inverter-based generators to inject negative sequence current during asymmetric faults — is not addressed in Recommendation 03-2023. ACER’s 2022 consultation raised this; the 2023 recommendation does not include a harmonized negative sequence injection mandate (cf. Germany: VDE-AR-N 4110/4120).

Key NC DC amendments proposed

The NC DC (EU 2016/1388, Demand Connection Code) amendments expand the demand-side framework to cover:

• Electric vehicles and EVSE: V2G, smart charging, bidirectional connections covered under harmonized EU demand connection requirements
• Heat pumps: brought under standardized connection requirements, creating a regulatory foundation for heat pump demand response at EU scale
• Power-to-gas / electrolysers: large electrolysers classified as significant demand facilities with connection requirements
• Criteria for significant modernisation: new definition of when an existing demand facility is substantially modified, triggering updated connection requirements

These changes create the regulatory foundation for NC DR’s FIS (Flexibility Information System) to register and manage the new categories of demand-side flexible assets.

Context and predecessor

The amendment process was initiated in spring 2022. The Generator Connection Requirements page references “ACER’s 2022 policy paper on RFG revision” — that is the policy paper and consultations that preceded this formal recommendation. Recommendation 03-2023 is the formal outcome of that 2022–2023 process.

Relevance to existing wiki pages