FERC Moves to Address Reliability Issues Tied to Growth of Inverter-Based Resources

by Paul Ciampoli
APPA News Director
November 27, 2022

The Federal Energy Regulatory Commission (FERC) on Nov. 17 took a number of actions addressing reliability issues tied to the growth of inverter-based resources (IBRs). 

IBRs are solar photovoltaic, wind, fuel cell and battery storage resources that use power electronic devices to change direct current power, produced by generators, to alternating current power, to be transmitted on the bulk-power system. “As use of this technology grows, it is important to ensure that IBRs do not adversely impact the technical reliability of the grid,” FERC noted.

At the meeting, FERC Commissioners approved an order and a notice of proposed rulemaking (NOPR) containing directives and proposed directives to the North American Electric Reliability Corporation (NERC), to account for the increasing number of IBRs in the nation’s resource mix. 

FERC Order

In the order, FERC directed NERC to submit within 90 days a work plan for Commission approval describing, in detail, how NERC plans to identify and register owners and operators of Bulk-Power System-connected IBRs that are not currently required to register with NERC under the bulk electric system definition but that in the aggregate have a material impact on the reliable operation of the Bulk-Power System.

Many IBRs connecting to the Bulk-Power System do not individually meet the current bulk electric system definition and, thus, are not registered with NERC, FERC staff said in a presentation.  NERC’s Commission-approved bulk electric system definition defines the scope of NERC’s reliability standards and the entities subject to NERC compliance. This means that those IBRs are not required to comply with mandatory reliability standards or respond to NERC Alerts. 

The order directs NERC to do three things. First, to complete modifications to its registration processes no later than 12 months after Commission approval of the work plan.  Second, to identify all owners and operators of Bulk-Power System-connected IBRs that in the aggregate affect the reliable operation of the Bulk-Power System no later than 24 months of Commission approval of the work plan.  And third, to register owners and operators of Bulk-Power System-connected IBRs that in the aggregate have a material impact on the reliable operation of the Bulk-Power System no later than 36 months after Commission approval of the work plan. 

The order recognizes that smaller Bulk-Power System-connected IBRs may not present the same reliability impact in all circumstances as generation that has historically been registered.  Accordingly, the order acknowledges that NERC may determine that the full set of reliability standard requirements otherwise applicable to generator owners and operators need not apply to all newly registered Bulk-Power System-connected IBR generator owners or operators.

NOPR

In the NOPR, FERC preliminarily finds that the reliability standards do not fully address the impacts of IBRs on the reliable operation of the Bulk-Power System. 

The NOPR proposes to direct NERC to develop new or modified reliability standards that address four reliability gaps related to IBRs:

• Data sharing: Currently, IBR owners and operators do not consistently share IBR planning and operational data, and the information that is shared is often inaccurate or incomplete; 
• Model validation: Once planners have IBR data, they must ensure the accuracy of such data to create valid system models;
• Planning and operational studies: Once planners and operators validate system models, they must include those models in planning and operational studies to assess the reliability impacts—both of individual and collective IBRs—on Bulk-Power System performance;
• Performance requirements: For example, IBRs’ ability to ride through system disturbances. 

The NOPR proposes to direct NERC to submit a compliance filing within 90 days of the effective date of the final rule detailing a comprehensive standards development and implementation plan explaining how NERC will prioritize the development and implementation of new or modified reliability standards to address the reliability gaps. 

The NOPR explains that NERC’s plan should take into account the risks posed to the reliable operation of the Bulk-Power System, standard development projects already underway, resource constraints, and other factors as necessary. 

Comments in response to the NOPR are due 60 days after the date of publication in the Federal Register, with reply comments due 30 days later.

FERC also issued an order that approved reliability standards that are related to IBRs, which NERC proposed earlier this year.