Improving Primary Frequency Response

Bob GreenPDCWG

August 3, 2011

Improvement Overview

• Ensure that there is adequate capacity available for frequency response

• Enhance compliance enforcement for significant events

• Add protocol requirements for sustained response

• Hold more joint workshops for QSE and Production staff

Adequate Capacity• One issue is that larger resources normally

have the largest MW/0.1HZ rate of governor response [given that all resources have the same droop %], but the larger units are usually the most cost efficient and are fully loaded [no governor response capacity].

• For any market product to be developed that would reserve distributed capacity for governor response to a unit trip, we need to model frequency versus available capacity.

B Point Frequency vs Generation

Governor Response Model

Frequency Response Model Data

Compliance Enforcement• Great progress is being made regarding the

definition and enforcement of adequate primary governor performance.

• Droop is hard to measure if the resource if the capacity is limited; therefore, adequate reserve must be factored into the measurement.

• We might need two tiers of enforcement. For instance, a 600 MW trip might result in warnings and fines issued for a 1,000 MW trip.

NPRR for Sustained Response• The PDCWG has been using the response terms

that follow for many years, but these key parameters are not in the Protocols or Operating Guides.

• ERCOT might need a requirement for sustained response more than larger interconnections.

• Steam supply might not be sustainable after aggressive governor response, but the frequency bias must be applied to plant set points.

Governor Response Terms

Response Term Specifications

QSE/Production Joint Workshops

• ERCOT engineering market participants are predominately electrical engineers [TSP and QSE representatives].

• ERCOT will have better primary frequency response if market participant mechanical engineers [Production representatives] are fully engaged in resolving issues leading to poor B point recovery.

• ERCOT should sponsor annual workshops.

Demo of Governor Model• Governor Model starts with 3 units serving

360 MW of load at 60.000 HZ.• A 35 MW disturbance is simulated by

changing load to 395 MW. B point=59.900 HZ• Simulate response with Unit #3 HSL=172 MW

by adding 21 MW and then 14 MW of load.• Unit #3 reaches 172 MW @ 59.940 HZ• Restore 60 HZ by adding 21 MW to Setpt(MW)• Add 14 MW; with Units #1 and #2 responding,

observe frequency B point=59.847 HZ.

Governor Response Model

Governor Response Model

Governor Response Model

Governor Response Model

Governor Response Model

Demo of Governor Curve Prototype• Key Governor Model parameters are

transferred to the Governor Curve Prototype.• Observe Frequency at HSL for each unit and

copy them into the Sort Freq field below.• The frequency vs generation curve will be linear

with break points at the Sort Freq values.• Sort the Freq values in decending order and

calculate total generation for each freq brk pt.• Enter New Gen for each section of the curve.• Observe New Freq calculated for each New Gen.

Frequency Response Model Data

B Point Frequency vs Generation

Possible Next Steps• Expand the EXCEL model with a subset of

ERCOT data.• Work with a graduate student to create a

study program that could handle the complete ERCOT system.

• If results could be informative in real-time, investigate an on-line application.

• Could be used for training of operations staff.• Might be used in the development of a market

product for governor response to a unit trip.