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Renewables are cleaning the grid. They’re also messing it up

Renewables are cleaning the grid. They’re also messing it up

Episode 67 of the Factor This! podcast features Ryan Quint, who oversees engineering and security integration for the North American Electric Reliability Corporation, which oversees the reliability of the bulk power system. Subscribe wherever you get your podcasts.

Power system engineers are wired to walk before they run. The block and tackle, crossing t's and dotting i's — whatever your favorite idiom — are critical to ensuring a safe and reliable energy supply.

But the energy transition has spurred a massive shift on a grid built around principles and rigid rules of stability and reliability built predominantly for synchronous generation. The race to decarbonize has brought on a new problem: In the absence of clear reliability interconnection requirements and standards, inverter-based resources are, in some instances, “misbehaving” and messing up the grid, and doing so despite repeated warnings. The North American Electric Reliability Corporation (NERC), which oversees the reliability of the bulk power system, has issued more than a dozen reports in recent years diagnosing the shortfalls of inverter-based resources (IBR) like solar PV, wind, and batteries. Some incidents are what the grid watchdog identifies as "faint signals" of broader implications. Others have teetered on complete grid collapse. 

Ryan Quint leads a team of engineers at NERC who are charged with pinpointing the root causes of these disturbances which, in the case of IBRs, typically involve a resource tripping offline due to a normal grid event: a tree falls on a powerline, a squirrel climbs on a substation bus, and so on. And these grid events happen every day. 

"When we have a normal grid event like that and we lose power from dozens of solar PV facilities, hundreds, or maybe even a thousand, inverters all at the same moment in time, that's a potential recipe for a catastrophically bad day," Quint said on the Factor This! podcast from Renewable Energy World. 

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Due to the volume of grid disturbances, NERC's postmortems are taking on a sterner tone. 

In its 2023 Southeast Utah Disturbance, which detailed the loss of 921 MW of solar generation from nine large-scale solar projects due to a normally-cleared fault on a faraway transmission circuit, NERC, in no uncertain terms, called out inverter original equipment manufacturers and generator owners for failing to address persistent, and previously identified, reliability issues. 

Generator owners "are often not addressing performance issues that latently exist within the existing fleet," NERC wrote, adding that in "all of the causes of abnormal performance in this event have been previously documented by NERC in past reports; however, actions were not taken." 

The disturbances have not, to this point, caused blackouts on their own. But that's due to IBRs playing a relatively still-small role in the power system. As renewable energy rapidly displaces fossil-fueled, synchronous sources, those “faint signals” may lead to systemic failures if the industry does not remain vigilant in addressing these underlying reliability risks. 

No one — not inverter manufacturers, developers, engineering, procurement and construction entities,, or asset owners — wants to be responsible for a blackout, and most parties involved in disturbances act prudently to remediate deficiencies, Quint said. But, at the same time, the pleas from his team at times seem to echo in the industry void, underutilized for proactive mitigation. 

In business, regulations typically follow innovation. So, the lag for IBR reliability is in part a predetermined consequence that stems from cleaning the grid. But Quint warns that broad buy-in is critical to ensuring reliability today and tomorrow. 

"We need to get out in front of this before (IBRs) grow and (these disturbances) get bigger and bigger and become a really, really bad day," Quint said. "It's a societal failure, right? And we do it. We do what we need to do make sure that that doesn't happen." 

Transmission lines outside Houston, Texas (Courtesy: BFS Man/Flickr)

The poster children for a "catastrophically bad day" are two major events that took place in Texas in 2021 and 2022. The now-infamous Odessa disturbances changed the landscape for reliability hawks. 

During Odessa #1, 1,300 MW tripped offline, and most of the capacity was brand new. Reliability concerns could be expected from first-mover markets, like California. But these inverters had the luxury of being developed earlier in the learning curve. 

Quint commended ERCOT, the state grid operator, OEMs, and asset owners, for taking quick action to patch inverter firmware to account for the improper settings. However, changes weren't implemented before the Odessa #2 disturbance took 2,500 MW offline for similar reasons the following year. 

"That's nearly the size of (ERCOT's) largest allowable event— the point where the rubber band snaps," Quint said. "That one was a very close call." 

Efforts are also underway to enhance the NERC reliability standards specifically related to IBR risks. The Federal Energy Regulatory Commission recently issued Order 901, which directed NERC to develop new or modified reliability standards. NERC is developing a comprehensive work plan regarding standards development activities to meet this directive, and is also making changes to its registration criteria and process to bring smaller projects on the bulk power system under NERC jurisdiction per a separate FERC directive. 

"(OEMs) want to provide a high-quality product, at least cost, though," Quint said. "What drives quality? Regulations, requirements, and markets. To me, it comes down to: do we have enough clear, consistent, and appropriate requirements in place? We’ve got to bring up requirements.”