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Regulatory Updates

New NERC Guidance Supports the Implementation of Grid Forming Inverters

Tim Farrar, PE | Jim Whitaker, PE | March 9, 2022

As inverter-based resource (IBR) penetrations continue to grow across North America, grid dynamics and control strategies must also be adapted.  Grid-Forming (GFM) inverter technology is gaining momentum because of its demonstrated superior performance during system disturbances. To support the proper implementation of these new technologies that protect reliability, NERC has issued a new report highlighting the key attributes, benefits and risks of various inverter controls.

Grid Forming Inverters

GFM inverters have been widely researched in battery energy storage systems (BESS), wind power plants, solar photovoltaic (PV) plants, and hybrid plants that are a combination of  generation and/or energy storage technologies controlled as a single entity and operated as a single resource behind a single point of interconnection.  Operating modes such as islanded operation capability without synchronous generation, blackstart, and operation in parallel with grid-following (GFL) inverter-based resources along with transitional synchronous generators have been explored.

There is limited explanation of GFM controls and their impact on BPS which is currently available. This NERC report is designed to provide that background to the industry.

Comparing Functionality: GFL vs. GFM

NERC provides the following comparison of  both GFM and GFL control systems.

The GFM control technology shows significant promise toward addressing the reliability risks being introduced with renewable generation operations during system upsets. Study findings from system conditions with high IBR penetrations show the potential benefits for GFM controls, and equipment vendors have commercially available products that can provide GFM capability. While GFM inverters must be studied and tuned to specific system conditions (like GFL controls), they do have a reliability risk mitigating advantage compared to the GFL control schemes. GFM IBRs are expected to be beneficial for increasing IBR penetration levels and will likely play an important role in contributing to the stability and reliability of the BPS under future high IBR penetration conditions.

Next Steps

Utilities are advised to carefully review NERC’s advice regarding inverter-based technology and its recommendations.  Companies should be prepared to modify their programs as necessary to address the reliability risks that inverter-based technology may introduce penetration of DER some regions are experiencing.

With expertise in all areas of power system planning and power delivery protection system engineering, TRC can provide independent project management services to review your company’s planning program. TRC is well positioned to assess your power system’s ability to perform as expected and in compliance with NERC mandatory standard including the potential impact of GFMs.


Your Trusted Regulatory Advisor

TRC closely follows the national and state regulatory trends in all regions of North America. Our approach to power system engineering, planning, design, construction and commissioning testing balances solutions that incorporate appropriate industry trends, mandatory standard requirements, regulatory guidance, compliance obligations, best practices, operational goals and budgets. With expertise in both power system planning and operations, we support public utilities and private energy providers in their effort to stay ahead of the curve to meet regulatory requirements as they evolve.

This regulatory update is a service to TRC’s utility clients, helping keep you informed of issues that impact your company’s electric system reliability risks along with related topics regarding regulatory developments to help you achieve your company’s business goals.

Tim Farrar, PE

Tim Farrar is a licensed professional engineer and works as the Protection & Controls Chief Engineer in TRC’s Augusta, Maine office. He is also a Certified Control System Technician (CCST) and Licensed Electrician with an Associate Degree from Eastern Maine Technical in Electrical Power Technology. Tim has 28 years of experience in protection and controls systems engineering for electric utilities and power generation industries including 10 years at Central Maine Power Company and 18 Years in the consulting engineering business. He has held several positions at TRC as an Engineer, Supervisor of Automation and Controls and Electrical Engineering Manager prior to his current position as Chief Engineer.

Contact Tim at

Jim Whitaker, PE

Jim Whitaker, PE is Supervisor of Power Systems Studies at TRC. He has over 30 years of experience in Transmission and Distribution Planning, and Substation, Transmission and Distribution Engineering. His Transmission Planning projects include coordinating joint/regional 10-year transmission plans, generator interconnections, regional system assessments, as well as NERC compliance studies. His projects have included studies for both Utilities and Project Developers across the United States in the Eastern and Western Interconnection transmission systems as well as ERCOT. Prior to joining TRC, Jim worked for Xcel Energy, Peak Power Engineering, Tucson Electric Power and Virginia Power. Contact Jim at

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