NERC Proposes Revisions to IBR Ride-through Standard PRC-029 

If you are developing an inverter-based resource (IBR), new federal reliability standards may require your project to ride through grid disturbances without disconnecting. For most projects, compliance is expected. But for developers who locked in hardware designs before these rules existed, or whose equipment is physically incapable of full compliance, a limited exemption has been proposed under the revised standard PRC-029-2. Here is what you need to know to determine whether your project qualifies as the standard undergoes ballot approval.

Background 

In July 2025, FERC issued Order No. 909, approving new reliability standards governing how IBRs must ride through frequency and voltage disturbances without disconnecting from the grid. One of those standards, PRC-029-1, establishes the core ride-through requirements for IBRs. 

Why a Revision Is Already Underway 

After reviewing industry feedback, FERC directed NERC to address two practical concerns within 12 months: 

• Some HVDC-connected IBRs with choppers have physical equipment constraints that make full compliance with PRC-029-1 technically impossible. 
• There is often a multi-year gap between when IBR hardware is specified and ordered and when a project comes online, meaning some developers locked in their designs before the new requirements existed. 

In response, NERC’s standards drafting team has fast-tracked a revised standard, PRC-029-2, targeted for an effective date of October 1, 2026, pending FERC approval. 

The Key Change: A Hardware Limitation Exemption (Requirement R4)

The centerpiece of PRC-029-2 is a narrowly scoped exemption for IBR owners who can demonstrate known hardware limitations that prevent compliance. To qualify, a project must meet one of two conditions:

1. Already in service by the effective date of PRC-029-1, or
2. Coming into service after the effective date of PRC-029-1, provided that:
   • An executed interconnection agreement was in place by October 1, 2026, and
   • An equipment procurement contract for the hardware causing the limitation was executed prior to September 1, 2025.

The September 1, 2025 procurement cutoff reflects the reality that IBR equipment is typically ordered three to five years before construction begins — meaning developers who committed to their hardware designs before Order No. 909 could not reasonably have anticipated these requirements.

Documentation Requirements

Qualifying projects must submit supporting documentation for any hardware limitation exemption by the following deadlines:

• IBRs already in service by the PRC-029-1 effective date: documentation due no later than 12 months after that effective date.
• IBRs coming into service afterward that meet the R4 criteria: documentation due within 90 days of the in-service date.

The revised standard provides detailed guidance on what evidence is required and how to document an exemption claim.