Staff from NERC and the Texas Reliability Entity commended ERCOT in a webinar Tuesday for its “extremely proactive approach” to mitigating the challenges exposed by the Odessa disturbances of 2021 and 2022, while reminding listeners that more work is needed across the ERO Enterprise to overcome the underlying issues.
The webinar was part of Texas RE’s monthly “Talk with Texas RE” series, in which presenters from the regional entity discuss ongoing and emerging reliability challenges in both the Texas Interconnection and the broader bulk electric system. Patrick Gravois, an electrical engineer at ERCOT, and Rich Bauer with NERC’s event analysis division joined David Penney of Texas RE in a discussion that built on the report that NERC and the RE released last year on the 2022 Odessa disturbance. (See NERC Repeats IBR Warnings After Second Odessa Event.)
The Odessa events occurred about a year apart near the town of Odessa, Texas. Both were initiated by faults at synchronous generation plants and resulted in the loss of significant amounts of solar PV and synchronous generation, with a reduction of 1,340 MW in 2021 and 2,555 MW in 2022.
In their report on the second event, NERC and Texas RE staff pointed out that most of the solar PV sites that responded abnormally in 2022 also did so in 2021. However, the cause of reduction for most of the facilities in the 2022 report was different from that recorded the previous year; many of these had implemented changes intended to prevent the causes of reduction in 2021.
The report concluded that addressing the performance issues of solar plants and other inverter-based resources is a “paramount” priority for the ERO that also requires the assistance of stakeholders including FERC, ERCOT, and electric utilities.
Gravois reviewed the risk mitigation measures that ERCOT undertook following last year’s disturbance. The first step was to convene discussions with generator owners (GO), original equipment manufacturers (OEMs) of the inverters involved in the incident, Texas RE, and NERC to investigate the root causes of the inverter tripping.
Following these meetings, the ISO ordered the affected GOs to submit mitigation plans and timelines within three weeks for correcting the identified issues. After the utilities submitted their plans, Gravois said ERCOT “followed up with them continuously … to make sure they were meeting the timeline [and] when we can expect these corrective actions to be implemented.”
Although the utilities have only had “the better part of fall 2022” to put their mitigation plans in place, Gravois said they are “getting really close” to completion. One of the few remaining measures needed on a widespread basis is a firmware update to inverters manufactured by Toshiba Mitsubishi-Electric Industrial Systems to address the DC voltage imbalance observed at three facilities.
“They had this ready to go at the time of the Odessa 2022 event, they just hadn’t implemented it yet,” Gravois said. “So they … will be implementing this in the rest of the facilities with these inverters throughout Texas as well, [and] ERCOT’s going to be reaching out to these facilities as well to make sure they’re working … to get this implemented.”
Further activities planned by ERCOT for 2023 include requesting GOs of affected facilities to update and resubmit their dynamic models to verify that they match the equipment’s field settings. The ISO also plans to contact all facilities, whether “operational or in the commissioning phase … to make sure they’re also proactively implementing all these corrective actions we’ve identified so they don’t trip off for future events.”
ERCOT’s longer-term goals include improving the interconnection process to check for known issues during commissioning and developing automated tools to look for small trips that might be signs of larger developing issues. Gravois said there also “really needs [to be] some discussion within ERCOT to look into running some kind of systemwide validation” to make sure GOs’ updated models are accurate.
