Wind Forecasting at ERCOT

Dan Woodfin

Director of System Operations

ERCOT

Southeastern Wind Coalition UAG

March 30, 2016

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The ERCOT Region

The interconnected electrical system serving most of Texas, with limited external connections

• 90% of Texas electric load; 75% of Texas land

• 69,621 MW peak, Aug.10, 2015

• More than 43,000 miles of transmission lines

• 550+ generation units

ERCOT connections to other grids are limited to ~1100MW of direct current (DC) ties, which allow control over flow of electricity

220 MW with SPP

600 MW with SPP

30 MW with CFE

at Eagle Pass

100 MW with CFE

at Laredo300 MW with CFE at Mc Allen

(up to 300 MW Jan. 2016)

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ERCOT Inc.

• The Texas Legislature restructured the Texas electric market in 1999

and assigned ERCOT four primary responsibilities:

• Maintaining System Reliability

• Ensuring Open Access to Transmission

• Facilitating of Competitive Retail Market

• Facilitating Competitive Wholesale Market

• ERCOT is regulated by the Texas Public Utility Commission with

oversight by the Texas Legislature

• Registered with NERC as RC, BA, TOP, TSP, PA, RP

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ERCOT is not a market participant

and does not own generation or

transmission/distribution wires

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Table of Contents

– Overview – Wind Generation in ERCOT

– Wind Forecasting

– Wind Forecast Performance and Operations

– Operation at Low-load and High-wind Conditions

Acronyms for this presentation:WGR: Wind-powered Generation Resource

STWPF: Short-term Wind Power Forecast

POE: Probability of Exceedance

MAPE: Mean Absolute Percent Error

COP: Current Operating Plan

RUC: Reliability Unit Commitment

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Installed Wind Generation in ERCOT

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.

PANHANDLE

WEST NORTH

SOUTH

COAST

HOUSTON

EAST( SPP COUNTIES)

Wind Regions within ERCOT (Installed Capacity)

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North:

912 MW

Coast:

1,876 MW

West:

9,647 MW

Panhandle:

2,670 MW

South:

1,141 MW

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Wind Records

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Time

Load

(MW)

Wind

Generation

(MW)

Penetration

at Record

Time

02/18/2016

21:2035,528 14,023 39.47%

03/23/2016

01:1027,245 13,154 48.28%

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Wind Duration

8

Hours

MW

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Short Term Wind Power Forecast

• Produced by AWS Truepower for each WGR

(Wind Generation Resource)

• Delivery: Hourly at 15 minutes after the hour

• Forecast period: 0-168 hour forecast

• Forecast for each WGR is provided to the

WGR; aggregate forecast is provided publicly

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AWS - ERCOT Short-term Wind Power Forecast

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Wind generation forecasts

delivered to ERCOT every

hour for the next 168 hours

in hourly intervals

MOS=Model Output

Statistics

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Day-Ahead Wind Forecast Performance

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Day Ahead Load Forecast Performance

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Hour-Ahead Wind Forecast Performance

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Wind Forecast Error Distribution

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0%

5%

10%

15%

20%

25%

30%

<-4250 -3750 to-3250

-2750 to-2250

-1750 to-1250

-750 to -250

250 to750

1250 to1750

2250 to2750

3250 to3750

> 4250

Fre

qu

en

cy

MW Error (actual wind- 3-hour ahead wind forecast)

Histogram of 3-hour-ahead Wind Forecast

3-hour-ahead windforecasterror in 2014[MW]

3-hour-ahead windforecasterror in 2015[MW]

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Challenges in Wind Forecasting

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• Relatively concentrated geographic region for much of installed wind capacity (lack

of spatial diversity)

• Large changes in wind generation output caused by different types of extreme

weather (large wind ramps)

• Frontal system, trough, or dry line/Thunderstorms/Low-level jets/Weakening pressure

gradients/Strengthening pressure gradients

• Hypothetical wind speed-power curves are an approximation to the actual results

Hypothetical

Power Curve

Actual Wind

Farm Power

• Much of generation is in the steep part of the power curve from 4-12 m/s is

where power changes dramatically with small changes in wind speed.

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Icing Event on Dec. 30, 2014

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2,000

2,600

3,200

3,800

4,400

5,000

5,600

6,200

6,800

7,400

8,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

MW

Hour Ending

Day-ahead STWPF for Dec. 30, 2014 Est. Uncurtailed Output (MW)

Hour-ahead STWPF for Dec. 30, 2014

ICING and Cold Weather

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-5,000

-4,000

-3,000

-2,000

-1,000

0

1,000

2,000

3,000

4,000

5,000

-6,000 -4,000 -2,000 0 2,000 4,000 6,000

3-hour-ahead Wind and Load Forecast Error

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Wind – Under forecast

Load – Over forecast

Wind – Over forecast

Load – Under forecast

Wind Under forecastWind Over forecast

Lo

ad

Und

er

fore

ca

st

Lo

ad

Ove

r fo

reca

st

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Unit Commitment

• Generators in market are

generally self-committed

• ERCOT can do “residual”

unit commitment for

reliability

– Usually due to transmission

– Only once in over a year to

provide capacity

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Ancillary Services Quantities

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Non-Spin Reserve Service Responsive Reserve Service

30 min deployment required but

most provided by 10 min quick

start or unloaded on-line gen

Capacity reserved from market to

provide governor response

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High Wind, Low Load

Operations

(Inertia)

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Wind on the Margin – Example Day

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Inertia in 2016 by Unit Type

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Inertia and 3 Hour Ahead Back-Forecast

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Questions?

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