1. “Look Ahead SCED”
Sai Moorty
ERCOT
November 28, 2011

2. Goals of “Look-Ahead SCED”
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.
November 28, 2011

3. White Paper on “Functional Description Of Core Market Management System (MMS) Applications For Look-Ahead SCED”
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.
The purpose of this White Paper is to provide a starting reference point for discussions with Market Participants, IMM and PUCT staff.
Settlement details including Make Whole provisions are not included in the White Paper.
ERCOT has not addressed the eligibility of a Make Whole for Generation, Load and Storage Resources in the White Paper.
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.
November 28, 2011

4. Significant upgrade to the Real-Time Market functionality.
“Look Ahead SCED”
Significant upgrade to the Real-Time Market functionality.
Requires rigorous involvement of ERCOT staff, Market Participants, IMM and PUCT staff.
“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.
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.
November 28, 2011

5. Comparison of Real-Time Market Features
PJM
MISO
NEISO
NYISO
SPP
CAISO
ERCOT
15-Minute
Load Forecasting
Yes
2 hr period No
2 ½ hour period
5 hr period
5-Minute
20 min period (?)
1 hr period
(?)
10 hr period (!)
Not used
Look-Ahead Commitment-
SCUC
(QSGR commitment)
IT SCED
1- 2 hr period
(new proposal)
(Resource Adequacy Assessment)
RTC for 2 ½ hour period
Intraday RUC
HASP 4 1/2 hr period
RTUC up to 2 hr period
Look-Ahead Dispatch
RT SCED
10-20 min period
(multi-interval optimized)
SCED
5-min period
for 5-min IT scheduling
RTD for up to 1 hr period
At least 2 time intervals
RTID for up to 1 hr period
Energy
Ramping Limits
Functions
single values
Single
values
functions/
Ancillary Service
Regions for deliverability
2 zones
seasonal
Seasonal
CAISO:
RTID is Real-Time interval Dispatch aka RTD.
November 28, 2011

6. Comparison of Real-Time Market Features (continued)
PJM
MISO
NEISO
NYISO
SPP
CAISO
ERCOT
Ancillary Service Co-Optimization
Yes
Both IT SCED and RT SCED
LOC/no AS offers
Both RTC and RTD
in RTUC No
Ancillary Service Substitution
Ancillary Service
Ramping Limits
single values
single
values
Ramp Rate
Sharing
Partial and separate ASO
Partial/
Configurable
configurable
Partial En/Reg
Transmission Constraints
Zonal
Nodal
Zonal(?)
Demand Response
Energy and reserve
Price Responsive Demand bids
Yes energy and reserve
Storage Resources
DLR Regulation
and Pump Storage Hydro
DLR Regulation and Pump Storage Hydro
PJM:
IT-SCED is intermediate SCED aka RTC
RT-SCED is Real-Time SCED aka RTD
ASO: Ancillary Service Optimizer
November 28, 2011

7. Moving Forward on “Look Ahead SCED”
Implementation Approach
Phased implementation.
Develop requirements / draft protocols for a given phase.
Components of “Look Ahead SCED” will be rolled into production in STUDY mode. i.e. outputs are NOT binding.
Similar to open-loop LFC testing prior to nodal go-live.
Utilize actual production data to verify/analyze non-binding results.
ERCOT will present & review results for each implemented phase
Finalize & Approve Protocols.
November 28, 2011

8. Moving Forward on “Look Ahead SCED”
November 28, 2011

9. Moving Forward on “Look Ahead SCED”
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
November 28, 2011

10. Moving Forward on “Look Ahead SCED”
December 2011-October 2012
Discuss and finalize features for “Look-Ahead SCED” with Market Participants, IMM and PUCT Staff.
White Paper provides framework.
Develop and approve Nodal Protocol Revisions.
Real-Time Market
Settlements
Review data and analysis of Open-Loop Phase-1 (Summer 2012).
November 28, 2011

11. Appendix -1
Phase-1 Summer 2012
November 28, 2011

12. Main Components of “Look-Ahead SCED”
The main components of “Look Ahead SCED” are:
Real-Time Commitment (RTC) Application
Real-Time Dispatch (RTD) Application
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:
Dispatch Instructions (Energy MW Base points) for Generation, Load and Energy Storage Resources.
LMP at all Settlement Points and Electrical Buses.
November 28, 2011

13. RTD is the dispatch engine in Real-Time Commitment (RTC) application.
Phase-1: Summer 2012
The first component of “Look-Ahead SCED” to be phased in will be a basic version of the Real-Time Dispatch (RTD) application
RTD key feature is a simultaneous multi-interval optimization with explicit ramp rate constraints modeled.
RTD is the dispatch engine in Real-Time Commitment (RTC) application.
NPRR 351
November 28, 2011

14. Phase-1: Summer 2012
Current Production SCED will continue to provide the settlement Base Points and LMP for dispatch and pricing.
Real-Time Dispatch (RTD) in STUDY mode:
Real-Time Dispatch (RTD) will run in parallel in study mode to current Production SCED.
ALL LMPs and Base Points from RTD are NOT BINDING. i.e. they are advisory/indicative.
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).
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). 
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)
November 28, 2011

15. Phase-1: Summer 2012
Real-Time Dispatch (RTD) in STUDY mode: (continued)
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.
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.
November 28, 2011

16. Phase-1: Summer 2012 ICCP & MIS
Binding MW Dispatch & Binding Prices for
SCED interval T
Current Production SCED
Current SCED Inputs
Advisory/Indicative MW Dispatch &
Advisory/Indicative Prices (LMP only) for
SCED interval T+5, …T+60
Real-Time Dispatch (RTD)
Additional “Look Ahead”
Inputs
MIS
November 28, 2011

17. Comparison of Current SCED And Real-Time Dispatch (RTD) Concepts
Note that in RTD, the multi-interval dispatch run is followed by a single interval SCED for each interval in the optimization period.
November 28, 2011

18. 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 Point
c) Incentive to increase output
a) Resource UP ramp constraint binding
Resource UP ramp constraint binding
LMP <= Offer Point
Dispatched ABOVE economical level
DOWN ramp limited
a) Base Point = LDL
b) LMP <= Offer Point
c) Incentive to decrease output MW
Resource DOWN ramp constraint binding
LMP <=Offer Point
Incentive to decrease output
LMP >=Offer Point
Dispatched BELOW economical level
November 28, 2011

19. Current SCED & Real-Time Dispatch (RTD)
Appendix – 2
Examples
Current SCED & Real-Time Dispatch (RTD)
November 28, 2011

20. Example 1: No Ramping Constraints – Load Peak
Resource Parameters
Price Curves
Resource
LSL
(MW)
HSL
Ramp Rate
(MW/min)
Unit 1 15 1
Unit 2 3
$/MWh
$/MWh 40 30 20 10 MW MW 5 5 15 15
Unit 1
Unit 2
November 28, 2011

21. Example 1: No Ramping Constraints – Load Peak (continued)
Current SCED (sequential) System Dispatch
“Look-Ahead SCED” - RTD System Dispatch
Time Interval
GTBD
System Lambda
Over/Under Generation
System Costs
T+0 14 20
230
T+5 27 40
680
T+10
Total Cost
1140
Time Interval
GTBD
System Lambda
Over/Under Generation
System Costs
T+0 14 20
230
T+5 27 40
680
T+10
Total Cost
1140
November 28, 2011

22. Example 1: No Ramping Constraints – Load Peak (continued)
Current SCED (sequential)
Unit 1 Dispatch
Unit 2 Dispatch
Time Interval TM
LDL
HDL
Base Point
LMP
Payment
Cost
Profit
Payment-Cost
T+0 10 5 15 14 20
280
230 50
T+5 9 40
600
250
350
T+10
Net$
450
Time Interval TM
LDL
HDL
Base Point
LMP
Payment
Cost
Profit
Payment-Cost
T+0 15 20
T+5 12 40
480
430 50
T+10
Net$ 50
November 28, 2011

23. Example 1: No Ramping Constraints – Load Peak (continued)
“Look-Ahead SCED” - RTD
Unit 1 Dispatch
Unit 2 Dispatch
Time Interval TM
LDL
HDL
Base Point
LMP
Payment
Cost
Profit
Payment-Cost
T+0 10
n/a 14 20
280
230 50
T+5 15 40
600
250
350
T+10
Net$
450
Time Interval TM
LDL
HDL
Base Point
LMP
Payment
Cost
Profit
Payment-Cost
T+0
n/a 20
T+5 12 40
480
430 50
T+10
Net$ 50
November 28, 2011

24. Example 2: Ramping Constraints – Load Peak
Resource Parameters
Price Curves
Resource
LSL
(MW)
HSL
Ramp Rate
(MW/min)
Unit 1 15 1
Unit 2 2
$/MWh
$/MWh 40 30 20 10 MW MW 5 5 15 15
Unit 1
Unit 2
November 28, 2011

25. Example 2: Ramping Constraints – Load Peak (continued)
Current SCED (sequential) System Dispatch
“Look-Ahead SCED” - RTD System Dispatch
Time Interval
GTBD
System Lambda
Over/Under Generation
System Costs
T+0 14 20
230
T+5 27
250
2 (Under)
1100
T+10
Total Cost
1560
Time Interval
GTBD
System Lambda
Over/Under Generation
System Costs
T+0 14 20
250
T+5 27 50 60
680
T+10
Total Cost
1180
November 28, 2011

26. Example 2: Ramping Constraints – Load Peak (continued)
Current SCED (sequential)
@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$/MWh.
Unit 1 Dispatch
Unit 2 Dispatch
Interval TM
LDL
HDL
B. P.
LMP
Payment
Cost
Profit
Payment-Cost
T+0 10 5 15 14 20
280
230 50
T+5 9
250
3750
3500
T+10
Net$
3600
Interval TM
LDL
HDL
B.P.
LMP
Payment
Cost
Profit
Payment-Cost
T+0 10 20
T+5
250
2500
350
2150
T+10 15
Net$
2150
November 28, 2011

27. Example 2: Ramping Constraints – Load Peak (continued)
“Look-Ahead SCED” - RTD
Unit 1 Dispatch
Unit 2 Dispatch
Time Interval TM
LDL
HDL
Base Point
LMP
Multi
Final
Payment
(LMP Final)
Cost
Profit
Payment-Cost
T+0 10
n/a 12 20
240
190 50
T+5 15 60 40
750
600
250
500
350
T+10
Net$
600
450
Time Interval TM
LDL
HDL
Base Point
LMP
Multi
LMP Final
Payment
Cost
Profit
Payment-Cost
T+0
n/a 2 20 40 60
-20
T+5 12 50
600
480
430
170
T+10
Net $
130 10
November 28, 2011

28. Example 2: Ramping Constraints – Load Peak (continued)
“Look-Ahead SCED” – RTD
@T+0, the system lamda is set by Unit 1 = 20$/MWh. Unit 2 cost is 30$/MWh and the price is 20$/MWh. LMP < offer price for Unit 2 but unit 2 is ramped UP.
@T+5, System Lambda from multi-interval optimization 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:
+40 $ for Unit 2 moving up 1 MW for T+5
+30 $ for Unit 2 moving up 1 MW for T
-20$ for Unit 1 moving down 1 MW for T
+30 $ for Unit 2 moving up 1 MW for T+10
-20$ for Unit 1 moving down 1 MW for T+10
=50 60$
@T+10, Unit 1 is marginal. Unit 2 is ramp constrained (DOWN). This is similar to what happens with CURRENT SCED when resource dispatched down to LDL. Here, Unit 2 LMP ($20) < Offer Price ($30) and is dispatched DOWN.
November 28, 2011

29. Example 3: Ramping Constraints – Load Valley
Resource Parameters
Price Curves
Resource
LSL
(MW)
HSL
Ramp Rate
(MW/min)
Unit 1 15 1
Unit 2 2
$/MWh
$/MWh 40 30 20 10 MW MW 5 5 15 15
Unit 1
Unit 2
November 28, 2011

30. Example 3: Ramping Constraints – Load Valley (continued)
Current SCED (sequential) System Dispatch
“Look-Ahead SCED” - RTD System Dispatch
Time Interval
GTBD
System Lambda
Over/Under Generation
System Costs
T+0 14 20
230
T+5 7
-250
2 (Over)
590
T+10
Total Cost
1050
Time Interval
GTBD
System Lambda
Over/Under Generation
System Costs
T+0 14 30
250
T+5 7 10 90
T+10
Total Cost
590
November 28, 2011

31. Example 3: Ramping Constraints – Load Valley (continued)
Current SCED (sequential)
@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$/MWh.
Unit 1 Dispatch
Unit 2 Dispatch
Time Interval TM
LDL
HDL
Base Point
LMP
Payment
Cost
Profit
Payment-Cost
T+0 14 9 15 20
280
230 50
T+5
-250
-2250
130
-2380
T+10 4
Net$
-2280
Time Interval TM
LDL
HDL
Base Point
LMP
Payment
Cost
Profit
Payment-Cost
T+0 10 20
T+5
-250
T+10
Net$
November 28, 2011

32. Example 3: Ramping Constraints – Load Valley (continued)
“Look-Ahead SCED” - RTD
Unit 1 Dispatch
Unit 2 Dispatch
Time Interval TM
LDL
HDL
Base Point
LMP
Payment
Cost
Profit
Payment-Cost
T+0 14
n/a 12 30
360
190
170
T+5 7 10 70 90
-20
T+10
Net$
320
Time Interval TM
LDL
HDL
Base Point
LMP
Payment
Cost
Profit
Payment-Cost
T+0
n/a 2 30 60
T+5 10
T+10
Net$
November 28, 2011

33. Example 3: Ramping Constraints – Load Valley (continued)
“Look-Ahead SCED” – RTD
@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.
@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$
@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