Congestion Management and Ramp Rate for Delivering Ancillary Services

Resmi Surendran

ObservationsIssue • Too much AS capacity reserved in single Resource

Effect• Resources needed for congestion management doesn’t

have Ramp Rate available for SCED to re-dispatch since it is reserved for Regulation

• Room available for SCED is limited to HASL and hence capacity is unavailable for congestion management

• Reserved AS capacity are not simultaneously deliverable due to ramp limitation and not converted to energy when deployed hence affecting reliability

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Ramp Available for SCED for Congestion Management

SURAMP = RAMPRATE – (RUSTELEM/ 5)SDRAMP = NORMRAMP – (RDSTELEM / 5)

WhereSURAMP/SDRAMP - SCED up/down ramp rate RAMPRATE- Normal Ramp Rate when RRS is not deployed or

when the subject Resource is not providing RRS. Emergency Ramp Rate for Resources deploying RRS

RUSTELEM/ RUSTELEM -Reg-Up/Down Ancillary Service Resource Responsibility designation provided by telemetry

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Need Protocol Change

• With minimal system change• That ensures that at least some capacity is

available to SCED from all Resources to resolve congestion.

• That reduces the time needed to resolve congestion there by increase the efficiency and reliability of congestion management

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Suggested Protocol Change

SURAMP = RAMPRATE – (RUSTELEM* REGP / 5)SDRAMP = NORMRAMP – (RDSTELEM * REGP / 5)

WhereSURAMP/SDRAMP - SCED up/down ramp rate RAMPRATE- Normal Ramp Rate when RRS is not deployed or when the subject

Resource is not providing RRS. Emergency Ramp Rate for Resources deploying RRSRUSTELEM/ RUSTELEM -Reg-Up/Down Ancillary Service Resource Responsibility

designation provided by telemetryREGP- Percentage of Regulation Service for which Ramp Rate will be reserved in Real-

Time. The value will be between one and zero. Suggested value 0.75

Motion to endorse ERCOT comments to NPRR 277 to be considered by TAC with the initial value of REGP no less than 0.75 in conjunction with considering periods when any Resource is asked to move beyond its ramp rate as periods of abnormal operation related to GREDP and Base Point deviation and proper notification to the Market of changes to the value of REGP.

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Constraint Violation IssueConstraint is violated at 101 MW setting SP at $3500

• HSL =500• MW=100• Ramp = 5 MW• Reg = 25 MW• SURAMP = 5 -25/5 = 0• SF = -0.5

• suggested change• SURAMP = 5 - 25*.75/5=1.25• BP = 102• SP will be reduced

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AS Deliverability Requirement

The protocols require that the QSE providing Ancillary Service in Real-Time shall ensure that the Resource carrying the Ancillary Service capacity has enough Ramp Rate to provide the reserved Regulation Service energy in five minutes, Responsive Reserve Service energy in ten minutes and Non-Spin Reserve Service energy in 30 minutes when the services are deployed.

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AS Deliverability Requirement

• DAM doesn’t consider Ramp Rate when awarding AS – Except checking RRS award<= 10* max ERR

• It is QSEs responsibility – to bid into AS only the amount that can be

delivered in RT – to schedule in RT in a Resource only the amount

of AS that can be deployed simultaneously

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AS Offer Example• Assume:– A Resource with an HSL = 400 MW and an LSL = 50

MW and Normal Ramp Rate = 10 MW/min = Emergency Ramp Rate.

– The Resource can supply no more than the Min(0.2*400, 100) = 80 MW of RRS.

– The Resource offers and is struck during an hour in the DAM for 80 MW of RRS and 50 MW of Regulation Up Service.

– All 80 MW of RRS is deployed

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AS Offer Example• Then

– The SCED Up Ramp = 10 MW/min – 50/5 Mw/Min = 0.– In this case, the SCED High Dispatch Limit = Net Power Output;

SCED issues a Base Point = Net power Output; the Resource will not follow the RRS capacity deployment with an energy deployment.

– If the awarded Reg-Up is 25 MW then the SCED Up Ramp = 5 MW/min and the HDL = Net Power Output + 5*5 MW/Min = Net Power Output + 25; the Resource can follow the capacity deployment with an energy deployment of no more than an additional 25 MW.

– In both cases with an 80 MW RRS deployment the Resource is expected to deliver RRS energy at 8 MW/min (or 80 MW in 10 mins) and is unable to do so. Only when the amount of Reg-Up Resource Responsibility is 10 MW or less can the Resource’s SCED Up Ramp be ≥ 8 MW/min.

– The responsibility for assuring that the AS Offer is deliverable belongs with the QSE. If the QSE offers both RRS and Reg-Up into the DAM, the QSE should no offer more than 10 MW of Reg-Up into the DAM concurrent with an 80 MW RRS offer.

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AS Offer Example

Start Hr End Hr Block No. Multi-Block Block Type F/V

Capacity MW

Reg-Up $/MWH

RRS $/MWH Online Non-Spin $/MWH

1 24 1 No V 80 10

2 V 10 10

The QSE could manage the ramp limitation for the AS Offers in this example by making • a single block offer linked to other AS as shown above OR• use of separate blocks in its AS Offer submission as shown in the above table. When the DAM clearing engine evaluates these AS Offers, it may strike in each hour up to 80 MWs of RRS and up to 10 MWs of Reg-Up. OR

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Start Hr End Hr Block No. Multi-Block Block Type F/V

Capacity MW

Reg-Up $/MWH

RRS $/MWH Online Non-Spin $/MWH

1 24 1 No V 50 10 10 10

AS Offer Example

The QSE could manage the ramp limitation for the AS Offers by the following method if the QSE can deliver the NSRS in the last 20 min

• REG offer <= NRR*5• RRS offer <= (ERR –REG offer/5)*10• NSRS offer <= (NRR - REG offer/5)*20

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Start Hr End Hr Block No. Multi-Block Block Type F/V

Capacity MW

Reg-Up $/MWH

RRS $/MWH Online Non-Spin $/MWH

1 24 1 No V 10 10

1 24 2 No V 80 10

1 24 3 No V 160 10

Appendix

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AS Offers• AS Offers requirements are contained in Nodal Protocol 4.4.5.• The Business Rules for AS Offer Submissions are included in the

following documentation:– MMS- Day-Ahead Market and Supplemental Ancillary Service Market

Requirements Specification (B2) version 4.0, Appendix 5. http://nodal.ercot.com/docs/pd/mms/pd/damsasmr/mms_dam_and_sasm_req_09q1_v4_0%20%28blackline%29.doc

– MMS – Explanation of Market Submissions Items version 0.3 http://nodal.ercot.com/docs/pd/mms/odfr/emsi/mms_explanation_of_market_submission_items_v0_30.doc

– EIP - External Interfaces Specification version 1.19P http://nodal.ercot.com/readiness/sandbox/docs/eip_external_interfaces_specification_v1_19P.zip

– Market Manager User Guide Version 0.06 http://nodal.ercot.com/readiness/markettrials/connectivity/keydocs/Market_Manager_User_Guide_06.doc

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AS Offers Cleared in the DAM• The DAM solution co-optimizes AS Offers and Three Part Supply Offers for a

Resource across the DAM’s Operating Day study period.– This results in the maximization of a Resource’s earnings across the Operating Day relative to its

Energy and AS Offers that are cleared in the DAM.

• The DAM clearing engine enforces the following Resource limits:– The total Energy and AS capacity for the Regulation Up/Down, Non-Spin and Responsive Reserve

awarded to the Resource must be less than or equal to the Resource’s HSL.– The amount of Off-line Non-spin AS capacity awarded to the Resource must be less than or equal to

the Resource’s HSL – LSL. – Responsive Reserve Service awarded to a Resource must meet the requirements established by

Nodal Protocol 3.18:• The amount of RRS provided from a Generation Resource must be less than or equal to 20% of thermal unit

HSL for an Ancillary Service Offer and must be less than or equal to ten times the Emergency Ramp Rate (the DAM uses the maximum emergency ramp rate as submitted in the RARF or Market Manager Resource Parameter Update Application);

• Hydro-powered Resources operating in the synchronous condenser fast-response mode may provide RRS up to the Resource’s proved 20-second response (which may be 100% of the HSL);

• For any hydro-powered Resource with a five percent droop setting operating as a generator, the amount of RRS provided may never be more than 20% of the HSL; and

• The amount of RRS provided from a Load Resource must be less than or equal to the HSL minus the LSL.

– The DAM clearing engine does not consider Resource Ramp Rates in the optimization of Energy or AS Offers.

– The DAM Offer validation process checks that the offering Resource is qualified to provided the offered AS but does not check if the offered quantity is within the Resource’s qualified amount.

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AS Offer Business Rules• AS Offers must be submitted according to the following groups:

– Regulation Down– Online reserves, including Regulation UP, responsive Reserve and Online Non-spin– Offline Non-spin

• Each AS Offer Group is treated independently• Within each group AS Offers that are submitted are studied as hourly offers, subject to the

following:– AS Offers in each hour may consist of up to 5 blocks of AS offers. In each hour, the DAM may clear AS Offers

from multiple blocks.• Each block of AS Offers may be designated as a fixed or variable block

– Fixed means that the AS Quantities specified in the block may only be struck only if the entire quantity for an AS Service in the block is dispatched. This can only be used by Load Resources and cannot exceed 150 MW.

– Variable means that the AS Quantity dispatched for an AS Service specified in the block may be up to the quantity specified in the offer.

– Contiguous hours may be grouped together by use of the multi-block designator – if the multi-block indicator is set the AS Offer will only be struck if all hours in the block are cleared.

• A Resource submitting a Three Part Supply Offer and AS Offers in the same hour may designate the Energy Offer as Inclusive meaning that the Resource can only be selected by the optimization if both the Energy Offer and an AS Offer is cleared in that hour.

• A Resource submitting a Three Part Supply Offer and AS Offers in the same hour may designate the Energy Offer as Exclusive meaning that the Resource can be cleared by the optimization to provide either Energy only or Ancillary Services but not both in the same hour.– If Exclusive AS Offers are dispatched in an hour, the DAM clearing engine simultaneously dispatches the

Resource at its LSL.

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Characteristics of AS Services• Regulation Service (Reg-Up and Reg-Down)– Regulation Service is the amount of energy that a

Resource is qualified by ERCOT to deliver in 5 minutes.– The amount of a Resource’s regulation energy deployment

is determined by the QSE assigned Regulation Participation Factor applied to the QSE’s Regulation Energy deployment directed by ERCOT’s LFC system.

– A portion of the Resource’s Ramp Rate equal to the Regulation AS Resource Responsibility ÷ 5 minutes is reserved for Regulation energy deployment from economic deployments (i.e. the SCED Up Ramp = (Normal Ramp Rate – Reg Responsibility/5), where the SCED Up Ramp is the ramp rate used to determine the economic deployment limits for SCED.

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• Responsive Reserve Service (RRS)– RRS is the amount of energy that a Resource is qualified by

ERCOT to deliver in 10 minutes.– RRS capacity is deployed by the QSE upon an instruction

from ERCOT to release Responsive Reserve Capacity for SCED Energy Dispatch.

– SCED based on the Resource’s Energy Offer Curve controls the amount of energy deployed by the Resource.

– For Resources supplying RRS capacity deployed by ERCOT, the SCED uses the a SCED Up/Down Ramp Rate determined by using the Resource’s emergency ramp rate at the current Net Power output to determine the maximum and minimum energy deployment instruction that can be issued to the Resource (refer to Slide 4).

Characteristics of AS Services

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• Online Non-spin Reserve Service (NSRS)– NSRS is the amount of energy that a Resource is qualified

by ERCOT to deliver in 30 minutes.– NSRS capacity is deployed by the QSE upon an instruction

from ERCOT to release Non-Spin Reserve Capacity for SCED Energy Dispatch.

– SCED based on the Resource’s Energy Offer Curve controls the amount of energy deployed by the Resource.

– For Resources supplying NSRS capacity deployed by ERCOT, the SCED uses SCED Up/Down Ramp Rate determined by using the Resource’s Normal Ramp Rate at the current Net Power output to determine the maximum energy deployment instruction that can be issued to the Resource (refer to Slide 4).

Characteristics of AS Services

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