Ancillary services are crucial for reliability, especially with increasing supply and demand variability.
NERC requirements for frequency control necessitate maintaining certain standards, including a minimum frequency response obligation and recovery within a specific timeframe after disturbances.
Analysis compared ERCOT's requirements with those of other North American operators, noting differences, such as California's 30-minute AS requirement, influenced by interconnection standards.
ERCOT's analysis of NERC standards, frequency deviation events, and peer ISO practices led to a set of recommended AS duration requirements. Regulation and responsive reserve should have at least a 30-minute duration for procurement in real-time, with ECRS requiring one hour and non-spin requiring four hours. These durations were chosen based on a combination of frequency control events, forecast uncertainty, and historical deployment durations.
For frequency control, events typically lasted under 15 minutes, but some exceeded that range. SCED unavailability events were analyzed, showing that 9 out of 10 events lasted 30 minutes or less, supporting the 30-minute recommendation for regulation and RRS.
ERCOT also reviewed net load forecast uncertainty and ECRS deployments, with a notable finding that 24 of 59 ECRS deployment events lasted over 60 minutes. For non-spin, 36 of 122 offline deployments lasted more than four hours, and 10 out of 73 events on non-scarcity days exceeded four hours.
Further examples were cited, such as the 03/02/2025 event, where non-spin was deployed for nearly five hours during a major underforecast of net load. This and similar days informed the recommendation of a four-hour duration for non-spin.
The analysis also noted that as new tools like DRRS are implemented, these duration requirements may need to be re-evaluated. Concerns were raised about rapidly changing these durations, with participants urging ERCOT to avoid frequent shifts to maintain market stability and clear investment signals.
State of charge (SOC) considerations were also emphasized. As more reserves are held by duration-limited resources like batteries, ERCOT is exploring additional layers of operational oversight beyond current PRC definitions, including potential megawatt-hour-based requirements.
Participants discussed how resource-specific AS awards under real-time co-optimization make SOC considerations critical. ERCOT noted that while batteries may respond based on market signals, operator visibility into aggregate energy stored on the system is becoming essential for reliability planning.
▶️2 - Discussion of Ancillary Services duration changes in NPRR1282 and NOGRR277
Discussion opened on NPRR1282 duration recommendations and possible language clarifications.
Eric Goff representing TSSA initiated discussions about market management of duration requirements, suggesting a conversation about triggers for energy and PRC. He proposed that instead of enforcing fixed duration constraints for each unit, ERCOT could manage total stored energy needs system-wide, enforcing requirements only when needed.
Andrew Reimers from IMM noted upcoming comments, and emphasized possible misconceptions regarding non-spinning reserve deployments and their duration requirements. He pointed out that increased non-spin procurement affects observed deployment lengths and cautioned against drawing conclusions solely from deployment durations.
Nitika Mago from ERCOT clarified deployment dynamics between offline and online non-spinning resources, mentioning the importance of maintaining sufficient reserves during forecast errors. She explained that ERCOT’s analysis primarily used offline non-spin deployments as a proxy for identifying difficult-to-forecast system events, and acknowledged the distinction between these and total non-spin deployments.
Eric Goff and others discussed concerns about implementing systemic changes without significant operational shifts at the go-live date. He acknowledged that certain aspects of his proposal would require system changes and should be considered post go-live.
Bob Helton echoed the importance of adapting methodologies to actual need rather than fixed periods and agreed with returning the proposal for further examination.
Caitlin Smith from Jupiter Power proposed that RTC might allow for lesser duration requirements than current values and advocated for a separation between qualification values and real-time service call expectations. She emphasized the rolling nature of 5-minute dispatch in RTC and argued that enforcing full duration in each interval could limit flexibility and increase prices.
Further discussion explored how SOC is evaluated in RTC, with Nitika clarifying that SOC is calculated based on end-of-interval conditions, considering the basepoint. Caitlin noted that, in practice, this could still require full SOC at every interval and create challenges for batteries providing frequent AS awards.
Blake Holt (LCRA) and others raised questions about NERC compliance, particularly whether some events under normal operations would still require robust SOC enforcement. Eric responded that tuning system-wide SOC requirements based on PRC or anticipated evening ramps could address those concerns.
Discussion highlighted concerns about implications on market dynamics and potential price impacts on consumers due to varying reserve duration requirements. Several participants, including Anna Mazenburg from Key Capture Energy, called for additional time and analysis to assess potential price impacts and market behavior changes pre-RTC implementation.
Summary closed with a reminder of the tight timeline to resolve open issues, aiming for a June board meeting decision to ensure inclusion in market trials.
