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Real Time Wind Generation Dispatch in a Nodal Market ... Nodal Systems will dispatch individual Generation Resources and therefore must

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Nodal Market Tools to Manage Wind Generation

April 17, 2009

Presentation to the Project No. 34577 Workshop

Presented by Dr. Spangler, P.E.Luminant Slide Deck Created by Floyd Trefny, P.E.


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Disclaimer

  • This presentation is made for the express purpose of describing the operation of the expected ERCOT Nodal Market Security Constrained Economic Dispatch application. The presentation is not intended to convey, and does not represent, any official position by Luminant Energy or Luminant Power on the subject matter presented herein.


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Topics

  • Generation Resource Parameters

  • System Parameters in a Nodal Operation

  • Real Time Wind Generation Dispatch in a Nodal Market

    • Typical Operation

    • Energy Offer Curves

    • Output Schedules


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Generation Resource Parameters

  • Nodal Systems will dispatch individual Generation Resources and therefore must “reserve” capacity by individual unit to support Ancillary Services requirements

  • Generation Resource Limits

    • HSL – High Sustained Limit*

    • HASL – High Ancillary Services Limit**

    • HDL – High Dispatch Limit**

    • LDL – Low Dispatch Limit**

    • LASL – Low Ancillary Service Limit**

    • LSL – Low Sustained Limit*

      * - Telemetered by QSEs for Real Time Dispatch; COP for future studies

      ** - Calculated by ERCOT for each Generation unit


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Generation Resource Parameters

  • HSL

    • Established by QSE to represent the maximum amount of available generation capacity in real time

      • May be equal to the Net Dependable Capability

      • If different than NDC in Real Time, then the QSE must provide a text reason why and send that to ERCOT

  • LSL

    • Similar to HSL but for the minimum amount of generation capacity

      • May be updated at QSE’s discretion


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Generation Resource Parameters

  • HASL

    • Established by QSE as the maximum capacity a unit may be dispatched while maintaining its scheduled ancillary services

    • Calculated as the HSL minus the Ancillary Service Schedules for Reg-Up, Responsive, and Non-Spin

    • Critical that QSEs not “withhold” capacity or overstate true generation capacity

  • LASL

    • Similar to HASL but for the minimum amount of generation capacity

    • Calculated as the LSL plus the Ancillary Service Schedule for Reg-Down


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Generation Resource Parameters

  • Ramp Rate used for HDL and LDL calculation must first back out any ramp rate reserved for Regulation

  • Deployment of Responsive Reserve assumes the QSE will use “Emergency Ramp Rate Curve” to assure delivery capability within 10 minutes

  • Deployment of Non-Spin Reserve assumes the QSE will use normal ramp rate curve because delivery is over 30 minutes

Ramp Rate

Mw/ Minute

  • Generation Resource Ramp Rates

    • Normal Curve and an Emergency Curve are provided by the QSE at time of Registration

    • Curves may be updated anytime by API

    • QSE also sends current ramp rate by telemetry; but only for information and IMM monitoring

Ramp Rate Curve

LSLG

HSLG

Gross Generation

Mw


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Generation Resource Parameters

  • HDL

    • Calculated by ERCOT as the maximum net generation achievable within 5 minutes given the current Mw generation and the units SCED Up Ramp Rate but not to exceed HASL/HSL

    • SCED-Up Ramp Rate is the normal ramp rate given the current generation less any ramp rate reserved for Reg-Up

  • LDL

    • Calculated by ERCOT as the minimum net generation achievable within 5 minutes given the current Mw generation and the units SCED Down Ramp Rate but must be greater than LASL/LSL

    • SCED Down Ramp Rate is the normal ramp rate given the current generation less any ramp rate reserved for Reg-Down


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System Parameters

  • Nodal Protocols require the calculation of various reserves in Real-Time and Protocols and PUC rules require calculations for future hours

    • RT reserves are based on telemetry of Generation limits and actual net generation

    • Future projections are based on COP and ERCOT’s Load Forecast

  • All calculation results are used by ERCOT operators and are posted to the market

    • Updates to RT are made every 10 seconds

    • Updates to future hours occurs every time LF is updated or if hour changes


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System ParametersExample

  • Ancillary Services

  • Reg-Up – 300 Mw

  • Reg-Down – 300 Mw

  • Responsive – 2300Mw

  • Non-Spin – 1200 Mw

  • Ramp Rate 250 Mw/Min

ΣHSL = 45000

3800 Mw

MW

Capacity

ΣHASL = 45000 – 3800 = 41200

SCED Up Reserve

RT Generation = 35000

SCED Dispatch

ΣHDL = 35000 + 1250 = 36250

SCED Down Reserve

ΣLDL = 35000 - 1250 = 33750

Σ LSL = 25000

Σ LASL = 25000 + 300 = 25300

Generation


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System ParametersExample

  • Ancillary Services

  • Reg-Up – 300 Mw

  • Reg-Down – 300 Mw

  • Responsive – 2300Mw

  • Non-Spin – 1200 Mw

  • Ramp Rate 250 Mw/Min

ΣHSL = 45000

3800 Mw

MW

Capacity

ΣHASL = 45000 – 3800 = 41200

SCED Up Reserve

RT Generation = 35000

SCED Dispatch

ΣHDL = 35000 + 1250 = 36250

SCED Down Reserve

ΣLDL = 35000 - 1250 = 33750

Σ LSL = 25000

Σ LASL = 25000 + 300 = 25300

Generation


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System ParametersExample

ΣHSL = 45000

3800 Mw

SCED Up Reserve

MW

Capacity

ΣHASL = 45000 – 3800 = 41200

RT Generation = 38000

SCED Dispatch

ΣHDL = 38000 + 1250 = 39250

SCED Down Reserve

ΣLDL = 38000 - 1250 = 36750

  • Ancillary Services

  • Reg-Up – 300 Mw

  • Reg-Down – 300 Mw

  • Responsive – 2300Mw

  • Non-Spin – 1200 Mw

  • Ramp Rate 250 Mw/Min

Σ LSL = 25000

Σ LASL = 25000 + 300 = 25300

Generation


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SCED Operation

  • Security Constrained Economic Dispatch (SCED) is the best means of prioritizing dispatch of all generation

    • Determines the Base Points for all generation units in the system including wind generation

    • Assures the maximum use of wind generation delivered to the ERCOT Load centers

    • Allows wind generation to compete on a even field with other types of generation including other forms of renewable generation

  • Correctly determines the price to be paid to wind generation for their energy when there are shortages and when there are excess amounts

  • Manages transmission congestion for ERCOT dispatch


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Resource

Node LMP

$/ Mwh

Mw Generation

SCED Offer Curves & Output Schedules

  • Each Generation Resource provides either an Energy Offer Curve (EOC) or an Output Schedule (OS) for ERCOT’s use in determining how to dispatch the generation on the grid

  • The EOC or OS must be provided to ERCOT prior to the Operating Period and have restrictions on how they may be updated and changed

  • Absence of an EOC or OS, ERCOT will create one (see appendix)

  • If dispatch priority is driven by something other than

    prices for the supply, then the prices paid to

    wind generators will not be in alignment with prices

    paid to other generators

  • An EOC is a curve that provides a price at any point for the full output range of the resource

  • A OS is a list of predetermined outputs for each 5 minute dispatch


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SCED DispatchSpecial Features for Wind Generation

  • Nodal Market provides for wind generators to send their maximum generation capability (High Sustained Limit) to ERCOT for use in every SCED cycle (nominally 5 minutes)

    • Normally set at the current amount of wind production

  • SCED uses this HSL to restrict dispatches to amounts that the wind generator can produce given current wind conditions

  • SCED determines if the wind generation can be set to the maximum or if a reduction is needed to manage the transmission system

  • SCED produces a Base Point for each wind Resource

    • Sent to the controlling QSE


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Typical Energy Offer CurvesNo Requirement for Congestion Management

$/ Mwh

Resource

Node LMP

Actual RT

Generation

Net Dependable

Capability

Mw Generation

LSL

HSL

HSL

HSL

HSL – High Sustained Limit

LSL – Low Sustained Limit

SCED

Base Point

Wind Decrease

Wind Increase


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Typical Energy Offer CurvesTransmission Congestion Present

$/ Mwh

Requested

Generation Decrease

Resource

Node LMP

Actual RT

Generation

Net Dependable

Capability

Mw Generation

LSL

HSL

HSL – High Sustained Limit

LSL – Low Sustained Limit

SCED

Base Point


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Deployment of Ancillary Services

  • Regulation

    • Deployed as a provider ratio share to the QSEs who are providing Regulation

      • QSEs deploy energy to individual Resources according to those Resource's DAM awards

  • Responsive Reserve

    • Deployed via signal to QSEs who reduce the telemetered Ancillary Service Schedule according to the amount of deployment

    • A new HASL is calculated for each Generation Resource using Emergency Ramp Rate Curves; Effect is to add previously reserved AS capacity to Real Time Reserves

    • SCED provides new Base Points to Resources

  • Non-Spin

    • Deployed similar to Responsive Reserve but uses Normal Ramp Rate Curves with same effect


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System ParametersDeployment of Non-Spin Reserve Ancillary Service

2600 Mw

ΣHSL = 45000

3800 Mw

SCED Up Reserve

MW

Capacity

2600 Mw

42400 Mw

ΣHASL = 45000 – 3800 = 41200

SCED Dispatch

RT Generation = 38000

ΣHDL = 38000 + 1250 = 39250

SCED Down Reserve

ΣLDL = 38000 - 1250 = 36750

  • Ancillary Services

  • Reg-Up – 300 Mw

  • Reg-Down – 300 Mw

  • Responsive – 2300Mw

  • Non-Spin – 1200 Mw

  • Ramp Rate 250 Mw/Min

Σ LSL = 25000

Σ LASL = 25000 + 300 = 25300

Generation


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System ParametersDeployment of Non-Spin Reserve Ancillary Service

2600 Mw

ΣHSL = 45000

SCED Up Reserve

MW

Capacity

ΣHASL = 45000 – 2600 = 42400

ΣHASL = 45000 – 2600 = 42400

SCED Dispatch

RT Generation = 38000

ΣHDL = 38000 + 1250 = 39250

SCED Down Reserve

ΣLDL = 38000 - 1250 = 36750

  • Ancillary Services

  • Reg-Up – 300 Mw

  • Reg-Down – 300 Mw

  • Responsive – 2300Mw

  • Non-Spin – 0 Mw

  • Ramp Rate 250 Mw/Min

Σ LSL = 25000

Σ LASL = 25000 + 300 = 25300

Generation


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Conclusions

  • ERCOT will provide to all Market Participants information on the current and projected amount of reserves to serve the load

    • QSEs who are watching the reserves, can respond to provide SCED with more generation when needed or take generation off when not needed

  • SCED is the most effective means of determining the dispatch priority of wind generation and assures correct price relationships to other types of generation

  • Wholesale competitive markets resolve at the least cost who should be allowed to generate when transmission congestion is present

    • Prices paid to wind generators for their energy will effect their willingness to generate

      • LMPs can be as low as -$250


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Appendix


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Typical Output ScheduleNo Requirement for Congestion Management

$3000

$/ Mwh

Resource

Node LMP

(set by other

Resources’

Dispatch)

Actual RT

Generation

Net Dependable

Capability

Mw Generation

LSL

HSL

HSL

HSL

-$250

SCED

Base Point

HSL – High Sustained Limit

LSL – Low Sustained Limit

Wind Decrease

Wind Increase


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Typical Output ScheduleTransmission Congestion Present

$3000

$/ Mwh

Requested

Generation Decrease

Resource

Node LMP

Actual RT

Generation

Net Dependable

Capability

Mw Generation

LSL

HSL

-$250

SCED

Base Point

Note LMP is

Set at -$250


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