Wind Operations Task Force Recommendation to ROS, 15 May 2008
Question 1: What can be done to improve STLF performance when previous day load profile and current day load profiles are obviously different?
Can a ‘similar day’ profile be substituted for the previous day profile? 
Changes to Protocols / Guides regarding Mid Term and Short Term Load Forecast weather sensitivity?

Consensus view:  The Market Analysis Interface tool has already been adjusted by ERCOT staff to consider weather-based wind generation forecasting as well as the previously used QSE Resource Plan.  Also, the Short Term Load Forecast and the MAI will no longer be used for projecting the need for balancing energy when the Nodal Protocols go into effect (currently set for Dec 1 this year).  The WOTF believes it is impractical to try to make minor improvements in this tool in the meantime.  The Operating Guide that describes the use of the STLF has not been identified.

The WOTF recommends no further action on the STLF.

Long Description

The Short Term Load Forecast (STLF) is a forecast that runs every 5 minutes and predicts the load in 5 minute increments up-to 60 minutes in advance.  This forecast is used by the real-time balancing process to calculate the amount of balancing energy to deploy.  The calculation is the difference between the STLF prediction and the aggregate total of all the ERCOT market schedules.  STLF is a neural network program that uses historical data to forecast the future 60 minutes of load, differentiating between weekdays and weekends, but not taking into account weather.  The ERCOT operators have the ability to manually offset for any known errors in the load forecast or in the aggregated ERCOT market schedules.  Improvements in the STLF could possible improve the balancing energy deployments but was not a factor in this event given that ERCOT had completely deployed all available Balancing Energy.   

ERCOT has taken the following action since the February 26th EECP event:

ERCOT has built an Adjusted Market Analysis Interface (MAI) spreadsheet that is used by the ERCOT Operator.  This new Adjusted MAI replaces the scheduled MWs for the wind plants with the AWS TrueWind forecast. The operators can look ahead and determine whether we have enough available resources for the day based on the TrueWind forecast instead of the resource plan scheduled output for wind resources, considering both the results of the previous version of the MAI and the Adjusted MAI. There have been hours when the scheduled MWs for the wind plants were significantly different from the wind forecast and the operators were able to plan ahead because of the Adjusted MAI spreadsheet.  The MAI is documented in Protocol #4.1.2, 4.5.5, and 5.6.3; and in Operating Guide #2.4.2; and in Shift Supervisor Procedure #2.1.7 and 2.2.2 .  The WOTF has not verified if these documents have been modified to reflect the usage of the Adjusted MAI.

Although changes to STLF could be imagined which may be an improvement on the existing application, all such proposals would be new research and development for a market design we plan to abandon with the adoption of the Nodal System Operations in December of this year.  ERCOT recommends no action on STLF.