IBR and DER Performance

What is an Inverter-Based Resource?

Inverter-based Resources (IBR) are electric generation resources that utilize an inverter (power electronic interface) to convert a direct current (dc) electricity supply to alternating current (ac) for connection to the grid. The figure at right shows examples of IBR that are predominantly solar, wind, and battery resources. Inverters are also prevalent in Distributed Energy Resources (DER) that connect to the grid at customer sites since most of these resources are solar photovoltaic arrays or batteries.

Risk Overview

IBRs connected to the bulk power system behave much differently than conventional generation, like coal and natural gas plants, and respond to grid conditions based on configured controls versus the physical response of a rotating machine. The unique behavior of these resources, limited industry experience, and challenges associated with implementation are having a major impact on electricity generation, transmission, and distribution systems. There have been 13 bulk power system disturbances since 2016 analyzed by NERC that involved performance issues with IBRs. Notably:

• Each event was characterized by significant loss of real power output following a system electrical fault.
• Each of these disturbances involved multiple solar and/or wind resources, which use inverters to generate into the grid.
• Some of these events also included the loss of real power from DER, which simultaneously increases load requirements of the grid.

The disturbance reports, alerts, guidelines, and other deliverables developed by the ERO thus far have highlighted that abnormal IBR performance issues pose a significant risk to bulk power system reliability. Each event analyzed has identified new performance issues, such as momentary cessation, unwarranted inverter or plant-level tripping issues, controller interactions and instabilities, and other critical performance risks that must be mitigated.

Trends

• The 2021 NERC Long-Term Reliability Assessment projects a rapid growth of IBRs—mostly wind, solar photovoltaic (PV), battery energy storage systems, and hybrid plants—with projections of nameplate capacity for solar PV projects in all development stages exceeding 500 GW over the next 10 years.
  • At the same time, wind projects are projected to total 360 GW of nameplate capacity.
  • This is an emerging risk for the MRO region as wind and solar resources become more prevalent.
• Dynamic load modeling generally aggregates data based on load characteristics, such as residential, commercial, and industrial, These modeling assumptions do not consider the unique characteristics of IBR and DER performance, which if not accounted for in operational and planning analyses, could be detrimental to reliability of the bulk power system.
• ERO Enterprise assessments identified a reliability gap associated with the increasing integration of IBRs as part of the grid and in which 16% of IBR owners and operators that are connected to the bulk power system are not yet required to register with NERC or adhere to its Reliability Standards, leading to reliability concerns.

Recommended Actions

• Ensure inverter settings support riding through a wide variety of grid disturbances.
• Evaluate inverter responses to grid disturbances for appropriateness, validate inverter models to actual performance, and share findings and corrective actions broadly.
• Modify interconnection requirements to clearly identify performance obligations and model accuracy expectations.
• Follow ERO Enterprise activity related to implementation of NERC’s IBR Strategy (linked below) and the related IBR Registration Initiative.

Mitigating Activities

NERC’s Inverter-Based Resource Strategy charts a path towards improving IBR performance issues, which includes supporting improvements to interconnection procedures and requirements, improving modeling, clarifying performance requirements, and increasing event analysis for abnormal performance. These efforts are in progress. One recent development is the issuance of FERC Order 2023 that in part requires IBR developers to provide models required for transmission providers to do accurate interconnection studies and to configure inverter controls to ride-through system disturbances. There are also several NERC standard projects in development to address some elements of the strategy.

FERC issued an Order in 2022 directing NERC to identify and register owners and operators of currently unregistered bulk power system-connected IBRs. Working closely with industry and stakeholders, NERC is executing a FERC-approved work plan to achieve the identification and registration directive by 2026. Resources for industry are posted on the registration page of the NERC website. NERC and the Regional Entities will work to identify and register new and existing IBR resources before the deadline of May 2026 listed in the FERC Order. A webinar series for industry in planned as part of this effort.

MRO partnered with MISO and Southwest Power Pool (SPP) in 2023 to analyze system disturbances within those entities’ respective footprints for any signs of IBR performance issues. The results showed few issues isolated to individual windfarms and no widespread issues like those seen in the California and Texas events. MRO’s Reliability Advisory Council also published an article (linked below) in June 2023 on the adoption of the IEEE 1547-2018 standard for Distributed Energy Resources. This article highlighted a reliability guideline developed by NERC’s System Planning Impacts from DER Working Group (SPIDERWG) on the same topic. The article listed key perspectives focused on the ridethrough capability of DERs and the need to coordinate settings and controls with expected grid operations to maintain reliability.

Additionally, the NERC System Planning Impacts from DER Working Group (SPIDERWG) has been analyzing the aggregate impacts that DERs can have on reliable operation of the bulk power system, and develops whitepapers, reliability guidelines, or standard authorization requests to address those impacts. Focus areas of the SPIDERWG are: displacement of generation providing various essential reliability services; balancing generation and demand and ramping requirements; adequate levels of voltage regulation and reactive power support; DER ride-through and trip settings; modelling and forecasting of DERs; and lack of observability or dispatchability of DERs.

Related Resources

IBR RIsk Information:

• Ensuring Grid Reliability Video (NERC)
• Introduction to Inverter-Based Resources on the Bulk Power System (NERC, June 2023)
• Inverter-Based Resource Strategy (NERC, June 2022)
• FERC-Approved IBR Work Plan (NERC, 2023)
• IBR Quick Reference Guide (NERC, October 2024)
• Inverter-Based Resource Performance Guideline (NERC, 2018)
• Distributed Energy Resources: Connection Modeling and Reliability Considerations (NERC, 2017)

IBR Registration Initiative Information:

• Open Letter to New Registrants
• Inverter-Based Resource Registration 101
• Inverter-Based Resource Registration Webinar and Slides (NERC)
• ERO Enterprise IBR Registration Initiative
• IBR Registration Initiative Comprehensive Slide Deck (NERC, 2024)
• IBR Registration FAQ
• Candidate for Registration: A Quick Reference Guide