Western balancing authorities should determine what caused the drastic errors in their load and generation forecasts during August’s massive heat wave and fix their forecasting process before next summer, WECC said this week.

That recommendation was just one of eight the regional entity offered the region’s BAs based on findings from its event analysis of the mid-August “heat storm” that gripped much of the West for nearly a week. The weather event prompted WECC Findings Show Complexity of Heat Wave Event.)

The heat wave was the topic of a technical session at a virtual version of WECC’s quarterly series of Board of Directors meetings. Tim Reynolds, WECC senior engineer, opened his presentation by saying there are two main reasons to perform an event analysis.

“One is you’re expected to, which is not the most ideal, because you’re doing the bare minimum checking the boxes, and you want to move on,” Reynolds said. “The second reason is more of learning mentality, and that’s definitely the approach the [WECC] team [took] for the analysis for the heat wave.”

WECC broke its heat wave event findings and recommendations into four categories: high load demand, use of transmission, inaccurate forecasting and resource adequacy.

Under the “high load demand” category, WECC determined that the Western Interconnection set a new peak record of 162,017 MW on Aug. 18, continuing a trend in which summer peak loads in the West have been increasing steadily over the past 10 years, creating increased competition for generating resources. Reynolds noted that some northern balancing authority areas that were previously winter peaking are becoming “dual peakers,” with both summer and winter peaks.

Reynolds said that 11 Western BAs were placed into an energy emergency alert (EEA) state during the event, with six elevated to the highest alert level — EEA 3 — but only CAISO was forced to shed load Aug. 14-15.

The event also indicated to WECC that reliability coordinators (RCs) and BAs may be applying NERC standards BAL-002-3 and BAL-002-WECC-2a inconsistently. The first standard ensures that a BA balances resources with demand and returns its area control error to defined values after a contingency event. The second specifies the quantity and types of contingency reserves required to operate in normal and abnormal conditions.

Reynolds said when an RC invokes an EEA, BAL-002-WECC-2a allows the affected BA to use multiple types of resources to meet its contingency reserve requirement but prohibits it from dropping below the required reserve to address a real-time emergency.

In response, WECC recommended that the regional entity work with industry experts to determine whether the standard should be changed to allow BAs to temporarily drop below the requirement. It also recommended further collaboration with experts to produce a document that provides more guidance to how BAs and RCs should respond to EEAs.

Unscheduled Flows, Unqualified Paths

Reynolds prefaced his description of WECC’s “use of transmission” findings by explaining how transmission flows in the West generally move in a circular fashion from north to south, with output from Northwest generation traveling on multiple transmission paths to serve loads in California and the Southwest.

Months before the heat wave, a windstorm damaged the Northwest AC Intertie (NWACI), a major line connecting the Bonneville Power Administration control area with California, reducing its rating by up to 1,250 MW. At the same time, a 750-MW derate on Path 3 limited transfers out of British Columbia. Transmission operators were able to increase the NWACI’s rating over Aug. 14-15, but derated it again after the system became unstable due to unscheduled flows.

Reynolds said the region’s existing procedure to mitigate unscheduled flows could not be applied to the NWACI because the line is not considered a “qualified path” under the Western Interconnection Unscheduled Flow Mitigation Plan (USFMP). As a result, the plan could not be invoked to coordinate phase shifters in the region because there were no unscheduled flows occurring on qualified paths at the time.

To avoid a similar outcome in the future, WECC recommended that RCs and BAs use phase shifters to help mitigate unscheduled flows beyond qualified paths. It also advised BAs to determine whether more transmission paths should be included in the USFMP.

WECC additionally recommended that RCs, BAs and transmission operators prepare for next summer by developing operating plans for a similar event. TOs should also work with their RCs to explore any phase angle concerns and establish “appropriate” system operating limits and interconnection reliability operating limits, WECC said.

Forecast Errors

A joint root-cause analysis of the blackouts by CAISO, the California Public Utilities Commission and the state’s Energy Commission found that under-scheduling by the state’s utilities contributed significantly to the ISO’s blackouts and subsequent EEAs. (See CAISO Says Constrained Tx Contributed to Blackouts.) WECC’s analysis has extended that finding to other areas of the West that declared alerts.

“What is interesting is when we asked the BAs that were in an EEA as to the cause of them being placed in it, some of the responses stated that their demand was higher than forecasted and it was difficult to find generation to purchase — so they had to go into an EEA,” Reynolds said. Other BAs told WECC that wind and solar production on Aug. 17-18 fell short of day-ahead forecasts, preventing them from meeting demand obligations.

“The BAs need to go back to this event, find the errors in their forecast leading up to it and make the changes needed to prepare for next summer,” Reynolds said.

“The longer out you can accurately forecast things, the more you can do ahead of time … like bringing back generation or transmission lines that were out for service,” he said.

Read, Understand, Follow

The California joint agency report and WECC have both pointed to outmoded resource adequacy planning as a central cause of the August energy emergencies. A key part of the problem, WECC found, is how current RA planning methods account for the contribution of the variable renewable resources that failed to perform as expected in intervals of peak demand during the heat wave.

That risk could be compounded as the West increasingly relies on renewable generation because of state clean energy mandates.

“From 2013 to 2019, we see overall about a 1% change in total net generation … which is not a significant change,” Reynolds noted, pointing to a bar graph in his presentation. “However, we do see an increased change in the use of solar and wind with a decrease in the baseload generation.”

“Resource adequacy usually forecasts a year out,” said Matt Elkins, WECC manager of performance analysis and resource adequacy. “We’re not really into forecasting day-ahead or anything like that, but you can see the same thing” with respect to the impact of variability on predictions.

Elkins said WECC found that current methods for planning RA are not reliable for extreme weather events. “We have to change the way we do things, and I think that’s what we’re getting at here.”

WECC’s recommendation? That industry participants “read, understand and follow” the recommendations to be included in WECC’s Western Assessment of Resource Adequacy, to be released later this month as a supplement NERC’s Long-Term Reliability Assessment for the entire North American grid.

Elkins provided board members a peek at those recommendations during their meeting Wednesday, which followed a technical session on the heat storm Tuesday. Included among the recommendations is a suggestion that the West adopt a dynamic reserve margin to better ensure reliability for all hours as more variable resources come into the system.

‘A Lot of Communication’

At the end of the Tuesday’s technical session, WECC Director Jim Avery asked how the heat wave analysis will be shared with state regulators.

“Will that be something the [Western Interconnection Regional Advisory Body] does? Is that something you’ll be reaching out to offer the regulators in the region? Because I know several regulators … raised concerns about what happened this summer, and if we’re part of the answer to explaining it, how are we getting the right information to them?” Avery asked.

“I think this is a very important message, and I think our plan will be to have targeted conversations with WIRAB and others to really inform them on what we’re seeing and what our plans are to mitigate some of these issues,” said Branden Sudduth, WECC vice president of reliability planning and performance analysis.

Avery noted also that the analysis covered the variability around renewable resources and weather, “but with extreme weather you get derates on baseload. How did that play out?”

“That’s an analysis we want to do,” Elkins replied.

Director Dan Arvizu asked about the biggest opportunities for improving forecasts. “Is it about the modeling? Is it about the computational capacity?” Arvizu asked.

“I’d be remiss if I didn’t mention from the team that it’s definitely been computational time,” Elkins said. “That’s one of the biggest problems with probabilistic studies to date is that the computing capability has not been there. We’re just now breaking into that.”

“And also, communication. … A lot of communication in the entire interconnection needs to be occurring,” he added.