GTBD Forecasting

Using SCED to Produce Projections of Future LMPs

Floyd J. TrefnyFebruary 17, 2011

Topics

ERCOT System Load Examples Sunday, January 30, 2011 Thursday, February 3, 2011

GTBD Forecasting Methodology Analysis of Forecasting Errors Implementation in SCED Next Steps

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LoadJanuary 30, 2011

System Load Mw/MinAverage Mw Change in Mw/Min over 15-minute SCED interval

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LoadFebruary 3, 2011

System Load Mw/Min

Average Mw Change in Mw/Min over 15-minute SCED interval

GTBD Forecasting Methodology

GTBD (Generation To Be Dispatched) is the sum of the Base Points dispatched in SCED

Typically, calculated by summing up the current actual generation from all the Generation Resources that are going to be dispatched by SCED

SCED LMPs are based on this amount of total power A reasonable forecast of future GTBD can be calculated

from: System ramp rate sampled over the last fifteen minutes

Ramp rate may be positive or negative

Add: Real-Time SCED GTBD + (Ramp Rate*15) gives the “Forecasted GTBD”

System Load* Projection Error Analysis

Interval Average

GTBD

15 Minute Load Change

Mw/Min

15 - Min Load

Projection Error % Error

0 23,229 15 23,458 na na15 23,625 35 24,145 167 0.7%30 23,834 20 24,130 (311) -1.3%45 24,104 18 24,373 (27) -0.1%60 24,391 9 24,521 18 0.1%15 24,765 14 24,977 244 1.0%30 24,722 -3 24,679 (255) -1.0%45 24,960 16 25,199 282 1.1%60 25,262 20 25,563 63 0.2%15 25,815 36 26,362 251 1.0%30 26,200 26 26,585 (162) -0.6%45 26,602 27 27,005 17 0.1%60 26,817 14 27,031 (188) -0.7%

*- Load s tarting at 0600 on 1/30/2011

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LoadJanuary 30, 2011

System Load Mw/Min

System Load* Projection Error Analysis

Interval Average

GTBD

15 Minute Load Change

Mw/Min

15 - Min Load

Projection Error % Error

0 51,541 53 52,332 na na15 52,651 74 53,760 319 0.6%30 53,399 50 54,147 (362) -0.7%45 53,923 35 54,447 (224) -0.4%60 54,369 30 54,814 (79) -0.1%15 54,901 35 55,433 87 0.2%30 54,573 -22 54,246 (860) -1.6%45 54,276 -20 53,978 30 0.1%60 54,257 -1 54,239 280 0.5%15 54,260 0 54,262 21 0.0%30 54,335 5 54,410 73 0.1%45 54,426 6 54,518 16 0.0%60 54,632 14 54,837 114 0.2%

*- Load s tarting at 0600 on 2/3/2011

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LoadFebruary 3, 2011

System Load Mw/Min

Implementation in SCED In addition to the existing SCED, execute the same

SCED algorithm once at the top of each 15-Minute period, but using the Forecasted GTBD

Use same offer curves, Resource Limits and Status that were available to SCED for the actual dispatch of generation

Assume that the same transmission constraints that are active in real time SCED are also active in the Forecast SCED calculation

Provide via ICCP and post on MIS, the LPM’s generated for:

Resource Nodes Hubs Load Zones (LMPZ) Generation

Load

HUB

SUPERHUBHUB

HUB

HUB

Next Steps

Get Comments from ERCOT Staff Draft NPRR WMS Discussion Seek expedited implementation to support

Quick Start objectives and demand response

Discussion

Appendix

SCED UP and SCED Down