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Integrating Southwest Power Pool Wind to Southeast Electricity ...

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<strong>Wind</strong> Delivery (MW)<br />

12000<br />

10000<br />

8000<br />

6000<br />

4000<br />

2000<br />

0<br />

0:00 1:00 2:00 3:00<br />

Time in hours<br />

4:00 5:00 6:00<br />

Figure 3-7<br />

Worst short term event<br />

In addition <strong>to</strong> the wind production data, the dataset for this study also contained a day-ahead<br />

forecast of the wind production that exhibited the approximate error characteristics of current<br />

state of the art forecast models. Individual wind plant forecasts have an MAE (mean absolute<br />

error) of 17% on average for all of the sites used in the study. However, the aggregation effects<br />

discussed earlier apply <strong>to</strong> the forecasts as well. The statistics for the forecast for each of the<br />

regions is shown in Table 3-3. These DA forecasts of wind output are used in the day-ahead<br />

commitment process of the SCUC/SCED simulations ensuring that the actual DA forecast errors<br />

have <strong>to</strong> be accommodated during the real-time dispatch using resources online or expensive<br />

quick start generation.<br />

Table 3-3<br />

<strong>Wind</strong> production forecast error statistics<br />

Worst Short Term Event<br />

ENTERGY SOCO SPP TVA Footprint<br />

MAE %Nameplate 8.3% 7.6% 8.6% 8.0% 7.7%<br />

MAE MW 653 1141 1268 829 3710<br />

Max Error 37% 35% 44% 35% 37%<br />

Reserve Requirements<br />

The increased variability and uncertainty from wind power causes an increase in operating<br />

reserve requirements. Those requirements have <strong>to</strong> be provided by some combination of flexible<br />

generation and responsive load. Together, these contribute <strong>to</strong> the operating reserve that is<br />

available <strong>to</strong> help manage the wind and load variability. This reserve is calculated dynamically,<br />

and is a function of the observed variability of the wind power and the load. A methodology was<br />

developed <strong>to</strong> estimate the increased requirements for reserves with wind variability in the<br />

Eastern <strong>Wind</strong> Integration and Transmission Study (EWITS).<br />

Short-term variability is challenging because it is difficult <strong>to</strong> fully anticipate the scheduling<br />

changes and fluctuations that must be covered with reserves. In a system with 10-minute or<br />

faster dispatch update cycles, a typical approach is <strong>to</strong> forecast a flat value for wind output for the<br />

3-8<br />

SPP Entergy<br />

SoCo TVA

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