IEEE Power & Energy Magazine - March/April 2021 - 23

megawatts of PFR generation can be replaced by 1 MW
of faster responding resources, depending on prevailing
inertia conditions. Introducing this ratio allowed ERCOT
to improve efficiency and reduce the overall procurement
costs of RRS, while better aligning procured amounts
with system needs under different inertia conditions.
✔ Regulation reserve service: This is the frequency restoration reserve deployed every four seconds. The upregulation and downregulation reserves are procured
separately. The regulation reserve amount is primarily
determined based on historic 5-min net-load variability.
✔ ECRS: This is a new service to be used as a replacement reserve that can be deployed within 10 min.
ECRS will be implemented in June 2024.
✔ Nonspinning reserve service: This is the existing replacement reserve that can be deployed within 30 min.
The amount of nonspinning reserve service is determined mainly based on historic hourly net-load forecast
uncertainty, evaluated based on wind, solar, and load
forecasts 3 h before an operating hour. The risk for netload ramps is also considered when determining nonspinning reserve service amounts.

Regulation

RRS
FFR
Load Resources on UFR
PFR

ECRS

10-min Ramp
Load Resources
May or May Not Be on UFR

Figure 6 provides more details about the ancillary services listed previously and reflects recently introduced
changes to the ancillary service set.

Interconnection Requirements
for Generation Resources
ERCOT ensures operational security through a strong set
of interconnection requirements that apply to generation
resources including IBRs. These requirements include, but
are not limited to the following:
✔ Voltage support: This is used to provide leading and
lagging reactive capability with a 0.95 power factor.
The capability is determined at the maximum active
power output, and voltage support within this capability limit has to be provided continuously, independent
of the active power output level.
✔ Frequency support: This provides the PFR with a 5%
maximum droop and a maximum frequency deadband
of ±0.017 Hz when frequency-responsive headroom
is available. Capacity reservation is not required unless the resource offered and was awarded RRS in the
day-ahead market. Figure 7 illustrates the frequency

No Change
FFR
* Triggered at 59.85 Hz and Gives a Full Response in 15 Cycles
* Once Deployed, Sustained for Up to 15 min; Once Recalled,
Restores Within 15 min
PFR
* PFR-Capable Capacity Reserved on Generators or
Controllable Load
* 1,150 MW Minimum Must Be Provided by Resources Capable of PFR
Load Resources on UFR
* Triggered at 59.70 Hz and Gives a Full Response in 30 Cycles
* Is Sustained Until Recalled; Once Recalled, Restores Within 3 h
* Beyond the Minimum PFR, Up to 60% of Total RRS Can Come From
Load Resources on UFR or FFR
Generation
* Online or Offline Capacity That Can Be Converted to Energy
Within 10 min
* Dispatched by Security Constrained Economic Dispatch
Load Resources (UFR Not Required)
* Up to 50% of ECRS Capacity Can Come From Load Resources
With or Without UFR
* Once Deployed, Must Respond Within 10 min; Restoration Within 3 h
No Protocol Changes

Nonspin

* Proposed Methodology for Nonspin Reserve Service Quantities in
This Framework-Quantities Computed Using 2018 Ancillary
Services Methodology Are Reduced by ECRS Quantities

figure 6. ERCOT ancillary services. The right-hand side illustrates recent changes introduced to the ancillary services
framework. UFR: under-frequency relays.
march/april 2021

ieee power & energy magazine

IEEE Power & Energy Magazine - March/April 2021

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - March/April 2021