Overview
Over the past decade, the Electric Reliability Council of Texas (ERCOT) has experienced a shift in its energy mix from constant-fuel synchronous generators to variable-fuel inverter-based resources (IBRs). As IBR penetration levels continue to increase, ERCOT is evaluating how to increasingly revise its ancillary services to accommodate IBRs while maintaining grid reliability.
GE Vernova’s Consulting Services team conducted a study to evaluate the need for new limits on resources that provide primary frequency response (PFR) given that IBRs—and particularly battery energy storage resources—are increasingly applying to provide these services. The study included an evaluation of system impacts to assess whether there may be reliability risks (particularly frequency performance risks) associated with the enhanced capabilities inherent in IBRs. Results of the study provided ERCOT with recommendations for future resource qualification, procurement structure, and operational practices.
Outcomes
IBRs have performance characteristics that can differ from those of synchronous machines. These performance characteristics, such as capability for lower droop settings which provide more rapid response, seem to offer advantages with respect to maintaining stable frequency.
The question the Consulting Services study set out to answer is “What are the risks of allowing battery energy storage systems (BESS) or any IBR on 1% frequency droop to displace PFR from synchronous machines on 5% frequency droop and what should ERCOT do to mitigate those risks?"
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