Power system engineers are accustomed to proceeding cautiously, ensuring meticulous attention to detail—the nuts and bolts, the fine print. The energy transition, however, has induced a seismic shift on a grid originally designed for stability and reliability with synchronous generation at its core. The push to decarbonize has unearthed a new challenge: the absence of clear reliability interconnection requirements and standards for inverter-based resources (IBR) like solar PV, wind, and batteries. Despite repeated warnings, these resources, in some cases, are causing disruptions and grid issues. The North American Electric Reliability Corporation (NERC), responsible for overseeing bulk power system reliability, has released numerous reports highlighting the shortcomings of IBRs. Some incidents are minor “faint signals,” while others have posed a serious threat to the grid’s integrity. Ryan Quint and his engineering team at NERC focus on identifying the root causes of these disturbances, often involving IBRs tripping offline due to commonplace grid events like a fallen tree on a powerline or a squirrel on a substation bus. The potential simultaneous shutdown of numerous IBRs during such events poses a significant risk, as highlighted by Quint on the Factor This! podcast from Renewable Energy World.

Due to the increasing frequency of grid disturbances, NERC’s analyses are adopting a more stern tone. In its evaluation of the 2023 Southeast Utah Disturbance, outlining the loss of 921 MW of solar generation across nine large-scale projects due to a fault on a distant transmission circuit, NERC unequivocally called out inverter original equipment manufacturers and generator owners for neglecting persistent, previously identified reliability issues.

NERC explicitly stated that generator owners often overlook performance issues within the existing fleet, despite documented concerns in past reports. The disturbances, although not causing blackouts independently, highlight the potential risks as inverter-based resources (IBRs) play an increasingly significant role in the power system, displacing traditional synchronous sources. As renewable energy replaces fossil-fueled sources, addressing these underlying reliability risks becomes crucial to prevent systemic failures triggered by subtle warning signs.

While no party involved wishes to be accountable for a blackout, there appears to be a gap between the industry’s prudent actions to address deficiencies and the calls for proactive mitigation from NERC’s team. In business, regulations often trail innovations, and the lag in IBR reliability is, in part, an anticipated consequence of grid improvements. However, Ryan Quint emphasizes the necessity of widespread cooperation to ensure reliability both now and in the future, urging the industry to address these challenges before IBRs become more prominent and disturbances escalate into a severe crisis.

The harbingers of a potential “catastrophically bad day” are exemplified by two significant incidents in Texas in 2021 and 2022, famously known as the Odessa disturbances, which reshaped the landscape for reliability advocates.

In Odessa #1, 1,300 MW went offline, with a considerable portion of the capacity being newly established. While reliability concerns might be anticipated in pioneering markets like California, these inverters benefited from early development in the learning curve.

Ryan Quint praised the prompt response of ERCOT, the state grid operator, as well as original equipment manufacturers (OEMs) and asset owners for swiftly addressing inverter firmware issues. However, adjustments were not implemented before Odessa #2, where 2,500 MW went offline for similar reasons the following year, posing a significant risk to ERCOT’s largest allowable event threshold.

Concerted efforts are in progress to fortify NERC reliability standards, particularly concerning inverter-based resource (IBR) risks. The Federal Energy Regulatory Commission’s Order 901 directed NERC to craft new or revised reliability standards. NERC is formulating a comprehensive work plan for standards development activities in response to this directive. Simultaneously, adjustments are being made to registration criteria and processes to include smaller projects within NERC’s jurisdiction, per a separate FERC directive.

Quint emphasizes the role of regulations, requirements, and markets in driving the quality of products by OEMs. The key question, according to Quint, revolves around having clear, consistent, and appropriate requirements in place to ensure the necessary standards are met.