“Look Ahead SCED”

November 28, 2011

“Look Ahead SCED”

Sai MoortyERCOT

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Goals of “Look-Ahead SCED”

November 28, 2011

The goals of “Look-Ahead SCED” in its final version are:

•Efficiently commit and dispatch Generation (e.g. QSGRs), Load and Storage Resources with Intra-Hour temporal constraints.

•Improve Resource management during steep load ramps considering Resource ramp rate limitations.

•Real-Time Co-Optimization of Energy and Ancillary Services.

•Account for future topology changes e.g. Outages.

•Provide short term future indicative prices.

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White Paper on “Functional Description Of Core Market Management System (MMS) Applications For Look-Ahead SCED”

November 28, 2011

1. This White Paper broadly describes the concepts that are proposed for an ERCOT implementation of “Look Ahead SCED”. This White Paper leverages function and features that have been implemented at other ISO’s.

2. The purpose of this White Paper is to provide a starting reference point for discussions with Market Participants, IMM and PUCT staff.

3. Settlement details including Make Whole provisions are not included in the White Paper.

a) ERCOT has not addressed the eligibility of a Make Whole for Generation, Load and Storage Resources in the White Paper.

b) The commitment and dispatch described in this White Paper can introduce scenarios where Resources would need to be Made Whole. It is the expectation that the mechanics of the Make Whole payment would be developed after the concepts of the “Look Ahead SCED” are agreed upon.

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“Look Ahead SCED”

November 28, 2011

a) Significant upgrade to the Real-Time Market functionality.

b) Requires rigorous involvement of ERCOT staff, Market Participants, IMM and PUCT staff.

c) “Look Ahead SCED” functionality at other ISO’s are implemented as a package of two applications. One that perform a simultaneous multi-interval commitment and the other that performs a simultaneous multi-interval dispatch.

d) All major vendors have architected their solutions for “Look Ahead SCED” to comprise of a simultaneous multi-interval commitment application and a simultaneous multi-interval dispatch application.

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FEATURE PJM MISO NEISO NYISO SPP CAISO ERCOT

15-Minute Load Forecasting

Yes2 hr period

No No Yes2 ½ hour period

No Yes5 hr period

No

5-MinuteLoad Forecasting

Yes20 min period (?)

Yes1 hr period

No(?)

Yes1 hr period

Yes10 hr period (!)

Yes1 hr period

Not used

Look-Ahead Commitment- SCUC(QSGR commitment)

YesIT SCED 1- 2 hr period

Yes(new proposal)

No(Resource Adequacy Assessment)

YesRTC for 2 ½ hour period

NoIntraday RUC

YesHASP 4 1/2 hr periodRTUC up to 2 hr period

No

Look-Ahead Dispatch Yes RT SCED 10-20 min period(multi-interval optimized)

YesSCED5-min period

NoSCEDfor 5-min IT scheduling

YesRTD for up to 1 hr period(multi-interval optimized)

YesAt least 2 time intervals

YesRTID for up to 1 hr period(multi-interval optimized)

No

Energy Ramping Limits

YesFunctions

YesFunctions

Yessingle values

YesSingle values

Yesfunctions/single values

Yesfunctions/single values

Yessingle values

Ancillary Service Regions for deliverability

Yes2 zones

Yesseasonal

Yes Yes YesSeasonal

Yes No

Comparison of Real-Time Market Features

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FEATURE PJM MISO NEISO NYISO SPP CAISO ERCOTAncillary Service Co-Optimization

YesBoth IT SCED and RT SCED

Yes YesLOC/no AS offers

YesBoth RTC and RTD

Yes Yesin RTUC

No

Ancillary Service Substitution

Yes Yes No Yes Yes Yes No

Ancillary Service Ramping Limits

Yessingle values

Yessingle values

Yessingle values

Yessingle values

Yessingle values

Yessingle values

No

Ramp Rate Sharing

YesPartial and separate ASO

Yes No No YesPartial/Configurable

YesPartial/configurable

YesPartial En/Reg

Transmission Constraints

YesZonal

YesNodal

YesZonal(?)

YesNodal

YesNodal

YesNodal

YesNodal

Demand Response YesEnergy and reservePrice Responsive Demand bids

YesEnergy and reserve




Yes energy and reserve

No

Storage Resources YesDLR Regulation

YesDLR Regulation

YesDLR Regulation

YesDLR Regulationand Pump Storage Hydro

YesDLR Regulation

YesDLR Regulation and Pump Storage Hydro

No

Comparison of Real-Time Market Features (continued)

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Implementation Approach

a) Phased implementation.

b) Develop requirements / draft protocols for a given phase.

c) Components of “Look Ahead SCED” will be rolled into production in STUDY mode. i.e. outputs are NOT binding.

i. Similar to open-loop LFC testing prior to nodal go-live.ii. Utilize actual production data to verify/analyze non-binding results.

d) ERCOT will present & review results for each implemented phase

e) Finalize & Approve Protocols.

Moving Forward on “Look Ahead SCED”

November 28, 2011

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November 28, 2011

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November 28, 2011

Phase Timeline Feature Implemented Comment

Phase -1 Summer 2012

Short-Term future Advisory/Indicative Base Points and LMPs using basic version of RTD.

Will initially run in Open-Loop i.e outputs (Base Points, LMPs) are Advisory/Indicative. i.e. non-binding.

Phase-2 Summer 2013

Commitment for QSGR and Load Resources with intra-hour temporal constraints using basic version of RTC.

Will initially run in Open-Loop i.e. outputs (Commitment instructions) are Advisory/Indicative. i.e. non-binding.

Phase-3 Spring 2014

Real-Time Ancillary Service and Energy Co-optimization using RTC.

Phase-4 Fall 2015 Transmission constraints for future intervals

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November 28, 2011

December 2011-October 2012

A. Discuss and finalize features for “Look-Ahead SCED” with Market Participants, IMM and PUCT Staff.a) White Paper provides framework.

B. Develop and approve Nodal Protocol Revisions.a) Real-Time Marketb) Settlements

C. Review data and analysis of Open-Loop Phase-1 (Summer 2012).

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Appendix -1

Phase-1 Summer 2012

November 28, 2011

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Main Components of “Look-Ahead SCED”

November 28, 2011

1. The main components of “Look Ahead SCED” are:

• Real-Time Commitment (RTC) Application

• Real-Time Dispatch (RTD) Application

1. The Real-Time Commitment (RTC) Application executes every 15 minutes with a rolling window for up to two hours study period that is comprised of up to 7 time intervals of 15 minutes each. The outputs of RTC are:

• Commitment Instructions for Generation, Load and Energy Storage Resources.

• AS Awards and MCPC. (Note: If a decision is made that Non-Spin is ONLY from OFFLINE Resources, AS Co-optimization can be moved to RTD).

• The Real-Time Dispatch (RTD) Application executes every 5 minutes with a rolling one hour window study period that is comprised of 12 time intervals of 5 minutes each. The outputs of RTD are:

2. Dispatch Instructions (Energy MW Base points) for Generation, Load and Energy Storage Resources.

3. LMP at all Settlement Points and Electrical Buses.

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Phase-1: Summer 2012

November 28, 2011

The first component of “Look-Ahead SCED” to be phased in will be a basic version of the Real-Time Dispatch (RTD) application

a) RTD key feature is a simultaneous multi-interval optimization with explicit ramp rate constraints modeled.

b) RTD is the dispatch engine in Real-Time Commitment (RTC) application.

c) NPRR 351

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November 28, 2011

1. Current Production SCED will continue to provide the settlement Base Points and LMP for dispatch and pricing.

2. Real-Time Dispatch (RTD) in STUDY mode:

a) Real-Time Dispatch (RTD) will run in parallel in study mode to current Production SCED.

b) ALL LMPs and Base Points from RTD are NOT BINDING. i.e. they are advisory/indicative.

c) Real-Time Dispatch (RTD) inputs will utilize the SAME inputs as the current Production SCED and additionally will utilize other inputs (short term load forecast, STWP).

d) Forward Advisory/Indicative LMPs at Settlement Points (NPRR351) will be output from Real-Time Dispatch (RTD) and posted on MIS Public, as well as QSE Resource Base Points on MIS Certified reports (neither data set will be telemetered).

e) By running in parallel Market will be able to observe production “what-if” for this building block of “Look-Ahead SCED” (similar to open-loop LFC testing prior to nodal go-live)

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November 28, 2011

2. Real-Time Dispatch (RTD) in STUDY mode: (continued)

f) Key feature of Real-Time Dispatch (RTD) will be the multi-interval optimization ( 1 hour study horizon comprising of twelve (12) 5-minute intervals) incorporating explicit ramp-rate constraint modeling.

g) Differences between MW dispatch and LMP for a given SCED interval between current Production SCED and Real-Time Dispatch (RTD) may occur if ramp constraints are binding due to future conditions.

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November 28, 2011

Current Production SCED

Real-Time Dispatch (RTD)

Current SCED Inputs

Additional “Look Ahead”Inputs

Binding MW Dispatch & Binding Prices for SCED interval T

Advisory/Indicative MW Dispatch & Advisory/Indicative Prices (LMP only) for SCED interval T+5, …T+60

ICCP & MIS

MIS

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Comparison of Current SCED And Real-Time Dispatch (RTD) Concepts

Current SCED Real-Time Dispatch (RTD) Objective Optimizes a single interval.

Simultaneously optimizes ALL intervals.

Power Balance (P.B.) Constraint

Single interval P.B. constraint

Each interval has P.B. constraint

Network Constraint: For each network constraint

1st Phase will enforce same TCM constraints for all intervals.

Ramp Constraint For each Gen. Resource

This is the constraint that connects all intervals.

Mitigation Two single interval optimization

runs (Step 1 & Step 2) Two multi-interval optimization runs (Step1 & Step 2)

Note that in RTD, the multi-interval dispatch run is followed by a single interval SCED for each interval in the optimization period.

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Comparison of Current SCED And Real-Time Dispatch (RTD)Ramp Constraints: LMP, Base Point, Offer Price Relationship

Current SCED Real-Time Dispatch (RTD)

UP ramp limited

a) Base Point = HDL

b) LMP >= Offer Price@Base Point

c) Incentive to increase output

a) Resource UP ramp constraint binding

b) LMP >= Offer Price@Base Point

c) Incentive to increase output

a) Resource UP ramp constraint binding

b) LMP <= Offer Price@Base Point

c) Dispatched ABOVE economical level

DOWN ramp limited

a) Base Point = LDL

b) LMP <= Offer Price@Base Point

c) Incentive to decrease output MW

a) Resource DOWN ramp constraint binding

b) LMP <=Offer Price@Base Point

c) Incentive to decrease output

a) Resource DOWN ramp constraint binding

b) LMP >=Offer Price@Base Point

c) Dispatched BELOW economical level

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Appendix – 2

Examples

Current SCED & Real-Time Dispatch (RTD)

November 28, 2011

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Example 1: No Ramping Constraints – Load Peak

• Resource Parameters

• Price Curves

November 28, 2011

0 5 15

10

20

$/MWh

MW

0 5 15

30

40$/MWh

MW

Unit 1 Unit 2

Resource LSL(MW)

HSL(MW)

Ramp Rate(MW/min)

Unit 1 0 15 1

Unit 2 0 15 3

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Example 1: No Ramping Constraints – Load Peak (continued)

• Current SCED (sequential) System Dispatch

• “Look-Ahead SCED” - RTD System Dispatch

November 28, 2011

Time Interval

GTBD System Lambda

Over/Under Generation

System Costs

T+0 14 20 0 230

T+5 27 40 0 680

T+10 14 20 0 230Total Cost 1140

Time Interval

GTBD System Lambda


System Costs

T+0 14 20 0 230

T+5 27 40 0 680

T+10 14 20 0 230Total Cost 1140

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• Current SCED (sequential)

– Unit 1 Dispatch

– Unit 2 Dispatch

November 28, 2011

Net$ 450

Net$ 50

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• “Look-Ahead SCED” - RTD

– Unit 1 Dispatch

– Unit 2 Dispatch

November 28, 2011

Net$ 450

Net$ 50

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Example 2: Ramping Constraints – Load Peak


• Price Curves

November 28, 2011

0 5 15

10

20

$/MWh

MW

0 5 15

30

40$/MWh

MW

Unit 1 Unit 2

Resource LSL(MW)

HSL(MW)

Ramp Rate(MW/min)

Unit 1 0 15 1

Unit 2 0 15 2

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Example 2: Ramping Constraints – Load Peak (continued)



November 28, 2011

Time Interval

GTBD System Lambda


System Costs

T+0 14 20 0 230

T+5 27 250 2 (Under) 1100

T+10 14 20 0 230Total Cost 1560

Total Cost 1180

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@T+5, the load to be served is 27MW, the system is 2 MW short. The System Lambda is set by the under generation penalty cost of 250$/MWh.

– Unit 1 Dispatch

– Unit 2 Dispatch

November 28, 2011

Net$ 3600

Net$ 2150

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– Unit 1 Dispatch

– Unit 2 Dispatch

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Example 3: Ramping Constraints – Load Valley


• Price Curves

November 28, 2011

0 5 15

10

20

$/MWh

MW

0 5 15

30

40$/MWh

MW

Unit 1 Unit 2

Resource LSL(MW)

HSL(MW)

Ramp Rate(MW/min)

Unit 1 0 15 1

Unit 2 0 15 2

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Example 3: Ramping Constraints – Load Valley (continued)



November 28, 2011

Time Interval

GTBD System Lambda


System Costs

T+0 14 20 0 230

T+5 7 -250 2 (Over) 590

T+10 14 20 0 230Total Cost 1050

Time Interval

GTBD System Lambda


System Costs

T+0 14 30 0 250

T+5 7 10 0 90

T+10 14 30 0 250Total Cost 590

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@T+5, the load to be served is 9MW, the system is 2 MW over. The System Lambda is set by the over generation penalty cost of 250$/MWh.

– Unit 1 Dispatch

– Unit 2 Dispatch

November 28, 2011

Net$ -2280

Net$0

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– Unit 1 Dispatch

– Unit 2 Dispatch

November 28, 2011

Net$ 320

Net$ 0

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• “Look-Ahead SCED” – RTD

1) @T+0, The System Lambda is set by Unit 2 is 30$/MWh. Unit 1 cost is 20$/MWh and the price is 30$/MWh. LMP > offer price for Unit 1 but Unit 1 is ramped DOWN.

2) @T+5, System Lambda is the change in objective function to a change in demand (by +-1 MW). If system demand changes by +1 MW for T+5, then change in objective function is:

+20 $ for Unit 1 moving up 1 MW for T+5

+20 $ for Unit 1 moving up 1 MW for T

-30$ for Unit 2 moving down 1 MW for T

=10$

3) @T+10, Unit 2 is marginal. Unit 1 is ramp constrained (UP). This is similar to what happens with CURRENT SCED when resource dispatched up to HDL. Here, Unit 1 LMP ($30) > Offer Price ($20) and is dispatched UP.

November 28, 2011

Documents

“Look Ahead SCED”