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Dan Woodfin Director, System Operations
Lessons Learned in Wind Integration in ERCOT
National Conference of State Legislatures Energy Program Webinar April 25, 2013
The ERCOT Region
The interconnected electrical system serving most of Texas, with limited external connections • 75% of Texas land; 85% of Texas load • 68,294 MW peak demand (set August 3, 2011) • More than 40,000 miles of transmission lines • 2 DC ties with SPP; 3 DC ties with Mexico;
1106 MW total • 550+ generation units
April 25, 2013 2
Markets • Fully unbundled Wholesale market
• ERCOT operates a single Control Area with ancillary services markets • Generators are paid Locational Marginal Prices (LMPs) at their node • Load-serving entities pay averaged load-zone prices
• Full Retail competition except in municipal & co-op utility areas
Transmission Service • All transmission costs are rolled-in to single postage-stamp rate paid by load • All generators have, essentially, “network service”
NCSL Webinar
ERCOT ISO
April 25, 2013
ERCOT Inc.: A non-profit corporation designated the “Independent Organization” under state law and assigned these responsibilities [Texas Public Utility Regulatory Act (PURA) 39.151]: • Maintaining System Reliability • Ensuring Open Access to Transmission • Facilitating the Competitive Wholesale
Market • Facilitating the Competitive Retail Market
Regulatory Characteristics: • ERCOT is regulated by the Texas
Public Utility Commission with oversight by the Texas Legislature
• ERCOT is not a market participant and does not own generation or transmission/distribution wires
• ERCOT is the sole Reliability Coordinator, Balancing Authority, Planning Authority, Interchange Authority, and Transmission Service Provider for the ERCOT Region
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Installed Wind Generation in ERCOT
April 25, 2013 NCSL Webinar 4
1,224
3,620 4,189 4,389
116
816 977 1,173 1,385 1,854
2,875
4,785
8,005
8,916 9,400
9,604 10,407
11,794
14,190 14,759
14,959
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
MW
Cumulative MW Installed
Cumulative Planned (Signed Interconnection Agreement)
ERCOT Wind Installations by Year (as of March 31, 2013)
The data presented here is based upon the latest registration data provided to ERCOT by the resource owners and can change without notice. Any capacity changes will be reflected in current and subsequent years' totals. Scheduling delays will also be reflected in the planned projects as that information is received.
This chart now reflects planned units in calendar year of installation rather than installation by peak of year shown
10,570
Currently, 10,570 MW nameplate capacity installed
Wind Output
• Peak wind generation output on 9,481MW on 2/9/13 – 27.8% of Load at the time
• 8.7% of Nameplate Capacity of wind counted towards reserve margin
% Energy Produced by Fuel Type 2012
0
500
1000
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4000
4500
5000
25,000
30,000
35,000
40,000
45,000
50,000
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65,000
70,000
8/9/10 8/9/10 8/10/10 8/10/10 8/11/10 8/11/10 8/12/10 8/12/10 8/13/10 8/13/10 8/14/10 8/14/10 8/15/10 8/15/10 8/16/10 8/16/10
Load
MW
Integrated Load Actual Integrated Wind Output
Wind M
W
Load
Wind
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Natural Gas, 44.6
Coal, 33.8
Nuclear, 11.8
Wind, 9.2
Water, 0.1 Other, 0.5
Competitive Renewable Energy Zones (CREZ)
• Transmission Plan designed to serve approximately 18GW:
– ~4600 circuit miles of 345 kV
– $6.7 billion project cost • All line certification
cases completed – Construction underway – All lines expected to be
complete by end of 2013
• Lines are open-access; use not limited to wind
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Operational Challenges for Wind Integration
• Uncertainty • Variability • Interconnection
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Wind Forecast
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• Wind power production forecast – Hourly 50% probability
of exceedance forecast for a rolling 48 hour period
– Provided for each wind farm and total for system
• Used to determine need for “residual” unit commitment
Forecasted and Actual Wind Power Production: Current Day
Graph Updated: Apr 24, 2012 15:20
Wind Power Production: 2,585 MW
Updated: Apr 24, 2012 15:35
Current Day Next Day
STWPF
Actual
Hour-ahead
Day-ahead
Wind Forecast Error
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0
50
100
150
200
250
<-4250 -3750 to -3250
-2750 to -2250
-1750 to -1250
-750 to -250
250 to 750
1250 to 1750
2250 to 2750
3250 to 3750
> 4250
Freq
uenc
y
MW Error (Estimated Uncurtailed Output - STWPF)
Histogram of Hour-Ahead MW Forecast Error All Hours
(Estimated Uncurtailed Output -STWPF) [MW]
0
1000
2000
3000
4000
5000
6000
0%
2%
4%
6%
8%
10%
12% Monthly M
ean Estimated U
ncurtailed Power O
utput [MW
]
Mon
thly
Mea
n Ab
solu
te P
erce
nt E
rror
of I
nsta
lled
Cap
acity
[%]
WIND POWER FORECAST Mean Absolute Percent Error
Monthly Mean Estimated Uncurtailed Power Output [MW] Day-Ahead 1430 STWPF Hour-Ahead STWPF
Average hour-ahead wind forecast error is significant
(MAPE is ~7%)
MW errors may be high (>1000 MW; occasionally
>2000 MW)
Wind Forecasting
• ERCOT Large Ramp Alert System (ELRAS) – Probabilistic forecast
which alerts Operators of ramps during the next 6 hours
– Provided on the system and regional level
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Predicting Large Ramps in Wind Power Output
April 25, 2013 NCSL Webinar
Ancillary Services - Regulation
• ERCOT typically dispatches generation each five minutes • Regulation Service is used to balance the variation in load and
generation between five-minute economic dispatch executions • Primary driver for determining required amount of regulation is
historical deployments – Adjusted for increase in installed wind capacity
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Ancillary Services – Non-Spin
• Non-spin Reserve Service – 30 minute product that can be provided by unloaded capacity,
offline Generators, and Load Resources – Wind power forecast error is one of the inputs used for
calculating the requirement for this service
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0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
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
Operating Hour
Actual Aggregated Wind Power Output Hour-Ahead COP HSL Day-Ahead COP HSL
Actual Wind, Wind Hour-Ahead COPs and Wind Day-Ahead COPs on June 27, 2011
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
30,000
35,000
40,000
45,000
50,000
55,000
60,000
65,000
Load MW
ERCOT Load PRC Wind Generation
Wind & PRC MW
2,300EEA Level 1 PRC below 2,300 MW for 1 minute
5,351 MW
1,135 MW
Non- Spin Deployed
Primary Frequency Response
• All generation in ERCOT is required to provide governor response with a 5% droop setting
• Wind farms are required to provide primary frequency response to frequency deviations from 60 Hz.
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100
110
120
130
140
150
160
170
100
110
120
130
140
150
160
170
CPS1
Ave
rage
Monthly Average 12 Month Rolling Average
Generation Ramps
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0
5000
10000
15000
20000
25000
30000
35000
40000
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
1 10 19 28 37 46 55 64 73 82 91 100
109
118
127
136
145
154
163
172
181
190
199
208
217
226
235
244
253
262
271
280
289
298
307
316
325
334
343
352
361
370
379
Agg
rega
te M
W O
utpu
t by
Typ
e
15 Minute Interval - Starting 4/17 0:00
Wind
Total Gen
Gas_CC
Coal
Gas
Nuclear
DC Ties
Hydro
Biomass
Other
Solar
Interconnection-Related Requirements
April 25, 2013 NCSL Webinar
• Inverter-connected resources may not fit with traditional technical requirements
• Need to address these issues to maintain system reliability:
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• Static and dynamic reactive capability
• Voltage-ride through capability
• Modeling o Collector system and
support device modeling o Dynamic model and
parameters
Impact of Wind Generation on Prices
• There is a clear shift down in the duration curve of real-time prices for higher levels of wind power output
16 NCSL Webinar April 25, 2013
Summary
• Sufficiently large Balancing Area • Nodal market mechanisms with short dispatch cycle to incent
flexibility in generation fleet and efficiently allocate curtailment • Accurate wind forecast and wind ramp projections • All generators required to contribute to system needs for
voltage support and frequency control • Incorporation of wind uncertainty and variability into ancillary
services requirements
17 NCSL Webinar April 25, 2013
Questions?
