One of the most basic, yet persistent, challenges faced by grid operators is gaining access to inverter settings, often locked behind manufacturer-issued passwords. Without access, grid planners can’t collect or adjust the configurations that determine how solar and wind resources respond to disturbances.
That challenge prompted a Level-3 alert, the highest classification, from the North American Electric Reliability Corporation (NERC). The alert calls on transmission owners, transmission planners and generator owners to “enhance technical minimum requirements and study processes to mitigate risks posed by inverter-based resource performance during system disturbances.”
These minimum requirements are intended to guide how solar inverters respond to complex grid events, helping prevent the system from overreacting, like an immune system attacking itself, and shutting down.
The alert outlines four “essential actions”:
- Enhance the existing criteria and policies in their generator interconnection and planning activities, respectively, with additional technical details and performance criteria for inverter-based resources.
- Enhance their modeling and study practices to ensure sufficient study work and model quality verification are performed and documented to reflect models that are representative of installed, or to-be installed, equipment.
- Review currently operating inverter-based resources on their system to understand the extent of condition of both real-world performance and accuracy of their models.
- Ensure the models used for the evaluation of their design and submitted to the transmission planner and planning coordinators for use in generator interconnection and planning processes are—to the extent possible based on the available information—accurate and high-fidelity representations of their inverter based resource.
NERC’s report references 10 major event reports and four Level-2 alerts previously issued on wind and solar inverter performance. Still, years later, the organization laments that many solar power plant owners continue to report that they lack access to critical system settings.
These settings determine how inverters respond to grid disturbances. NERC’s proposed changes aim to enable inverters to “ride through” such events rather than shut down, allowing renewable generation to stay online during brief disruptions. Disturbances could include events like a power plant going offline, forest fires causing power line faults, or the recent large-scale grid failure in Spain. In many cases, current settings trigger a complete plant shutdown for up to five minutes, a delay typically intended to protect line workers. But as solar and wind resources supply a larger share of electricity, this protection-first logic increasingly risks cascading failures.
This risk was highlighted during the 2021 Odessa Disturbance. A single-line-to-ground (Phase A) fault occurred on a generator step-up transformer at a combined-cycle power plant near Odessa, Texas. Though the fault was resolved in just a few electrical cycles, its effects rippled across the grid, triggering shutdowns in more than 1 GW of solar generation, including sites up to 200 miles away.
At the time, many inverters were still operating with legacy settings from the 2010s that prioritized rapid disconnection during grid anomalies. While once a prudent safety measure, these configurations now pose a threat to grid stability when they are applied at scale. If too much generation drops offline at once, it can set off a chain reaction, like the one seen in Spain several weeks ago.
NERC also noted that many of the inverters affected in past events came from a small number of manufacturers. Some of those manufacturers are no longer in business, making it more difficult to access configuration data or implement the urgent changes NERC is proposing.
This content is protected by copyright and may not be reused. If you want to cooperate with us and would like to reuse some of our content, please contact: editors@pv-magazine.com.
By submitting this form you agree to pv magazine using your data for the purposes of publishing your comment.
Your personal data will only be disclosed or otherwise transmitted to third parties for the purposes of spam filtering or if this is necessary for technical maintenance of the website. Any other transfer to third parties will not take place unless this is justified on the basis of applicable data protection regulations or if pv magazine is legally obliged to do so.
You may revoke this consent at any time with effect for the future, in which case your personal data will be deleted immediately. Otherwise, your data will be deleted if pv magazine has processed your request or the purpose of data storage is fulfilled.
Further information on data privacy can be found in our Data Protection Policy.