NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Testing Active Power Control from Wind 

Power at the National Wind Technology Center

Erik Ela

May 25, 2011

WindPower 2011

Anaheim, CA

Erik.Ela@nrel.gov

NREL/PR-5500-51607

PIX 16562
National Renewable Energy Laboratory Innovation for Our Energy Future

Current Mainstream Limitations of Wind

• Two of the most talked about limitations of wind...

• It costs too much

• It cannot behave as traditional generators (non-dispatchable)
APCFWP Team

NREL

Erik Ela

Vahan Gevorgian

Paul Fleming

Ed Muljadi

Colorado School of Mines

Kathryn Johnson

Yunho Jeong

National Renewable Energy Laboratory Innovation for Our Energy Future

EPRI

Daniel Brooks

Pouyan Pourbeik

Aidan Tuohy
Active Power Control

National Renewable Energy Laboratory Innovation for Our Energy Future

0 s typically, 

5 - 10 s

 typically, 

20 - 30 s

 typically, 

5 – 10 min

Initial slope of decline is 

determined by system 

inertia (or cumulative 

inertial response of all 

generation)

Primary Freq. Control AGC

Disturbance

Normal 

conditions

Where can 

wind power fit 

in?

Frequency (Hz)

60
Differences in Perspective

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Operators

Wind 

Owner/Operator

Manufacturer

Sure I desire it, 

but why would I 

ask them to 

provide the 

capability if they 

cannot provide it?

Why would I provide 

that capability if I don’t 

have to and will lose 

revenue?

Sure I can build 

this, but why 

market this 

capability if nobody 

desires it?

Regulator

Why create a 

market or policy for 

that capability if 

there currently is 

enough or it is given 

for free?

Research and 

Demonstration
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Making the Case

 Current decline of the North American Eastern Interconnection 

frequency response of about 60-70 MW/0.1 Hz per year 

 Ingleson and Allan 2010, Ingleson and Ellis 2004, etc.

 2011 FERC/LBNL study on Frequency Response Metrics to 

assess requirements for reliable integration of VG:

 Though states wind not being the cause to frequency decline, recommends 

“expanded use of frequency control capabilities that could be provided by 

variable renewable generation technologies (primary frequency control, 

etc.)”

 Kirby et al “Providing minute to minute regulation from wind 

plants”

 “The analysis has shown that there is a potential for wind plants to aid 

power system reliability and increase their own profits by providing 

regulation.”

 Wind power integration studies (e.g. EWITS, WWSIS, etc.) have 

recommended use of wind power providing secondary and 

tertiary reserve power during min load periods
Regulation: A Lucrative Business

• Regulating is essential to an area; since 

“deregulation” markets have been 

formed to pay for this service along with 

other ancillary services

• Many units take wear and tear hits on 

their machine and turn this into high 

offer costs to provide the service that 

lead to high prices (also efficiency loss 

costs)

• These prices are in $/MWh of capacity, 

the unit will be paid the energy price 

based on where it actually produced in 

addition

• Resource is ONLY asked to provide 

regulation if it is economic

• The prices can often be higher than 

energy prices and will increasingly be so 

as more low-variable-cost resources 

enter the energy market

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Eastern Date Hour

Pricing 

Region

10 Min 

Sync

10 Min 

Non Sync

30 Min 

Non Sync

Regulatio

n

10/1/2009 0:00 EAST 3.34 3.34 0.25 28

10/1/2009 1:00 EAST 3.35 3.35 0.25 28

10/1/2009 2:00 EAST 3.35 3.35 0.25 28

10/1/2009 3:00 EAST 3.35 3.35 0.25 28

10/1/2009 4:00 EAST 3.35 3.35 0.25 28

10/1/2009 5:00 EAST 3.35 3.35 0.25 45

10/1/2009 6:00 EAST 3.36 3.36 0.25 209.02

10/1/2009 7:00 EAST 7 3.4 0.5 39.5

10/1/2009 8:00 EAST 5 3.38 0.5 43

10/1/2009 9:00 EAST 6.11 3.38 0.5 41.5

10/1/2009 10:00 EAST 6.2 3.36 0.5 41.5

10/1/2009 11:00 EAST 7 3.37 0.5 28

10/1/2009 12:00 EAST 6.11 3.35 0.5 28

10/1/2009 13:00 EAST 6.14 3.35 0.5 28

10/1/2009 14:00 EAST 6.11 3.35 0.5 28

10/1/2009 15:00 EAST 6.1 3.35 0.5 28

10/1/2009 16:00 EAST 6.11 3.32 0.5 41.5

10/1/2009 17:00 EAST 6.1 3.32 0.5 41.5

10/1/2009 18:00 EAST 6.89 3.32 0.69 41.5

10/1/2009 19:00 EAST 9.84 3.34 2 41.5

10/1/2009 20:00 EAST 5 3.32 0.5 41.5

10/1/2009 21:00 EAST 5 3.34 0.5 41.5

10/1/2009 22:00 EAST 5 3.36 0.5 41.5

10/1/2009 23:00 EAST 0.25 0.25 0.25 28

21 cents per kWh just to 

provide regulating capacity!

NYISO pricing data www.nyiso.com
NYISO Regulation Prices

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$0

$50

$100

$150

$200

$250

$300

0:001:002:003:004:005:006:007:008:009:00

10:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:00

Regulation Exceeds Energy
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Primary Response Status

• Europe: UCTE (ENTSO-E requires 3000 MW of primary 

response throughout interconnection, distributed based on 

load/generation ratio.

• NERC: No quantifiable requirement for primary response.

• Current decline (Ingleson research).

• Eastern Interconnection currently has no “C” point.
Primary Response Status

• Reasons for decline:

• Governor dead bands;

• Stepped droop vs. proportional droop;

• Blocked governors;

• Market issues;

• Generator modes (sliding pressure, exhaust temperature control mode).

• Neither Europe nor North America have designated ancillary 

services market for primary response ─

• E.g., Spinning reserve market does not necessarily mean governors are 

enabled.

• If enough wind displaces and de-commits conventional units 

providing this service, and wind does not provide these 

capabilities, this can cause a further decline.

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Active Power Control Project

National Renewable Energy Laboratory Innovation for Our Energy Future

• NREL and EPRI joint project, to test at NWTC facilities.

• Economic and power system analysis and simulations.

• Computer simulations of control capabilities.

• CART machine field-test.

• Utility scale wind turbine test and demonstration.

• Push the boundaries, more in-depth testing

• Parameter adjustments (dead bands, ramp rates, droop 

characteristic, etc.).

• Different wind speeds, upward and downward, high varying wind.

• All responses together.

• Publish results and demonstrate to regulators, operators, wind 

owner/operators, and manufacturers.
Active Power Control from Wind Power Workshop

National Renewable Energy Laboratory Innovation for Our Energy Future

www.nrel.gov/wind/systemsintegration/active_power_control_workshop.html
Project Tasks

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Task1: Steady 

State and 

economic 

analysis

Task2: 

Transient 

Analysis

Task3: 

Turbine 

Controls 

Simulation

Task4: 

Turbine Field 

Test

Next Phase: 

Farm Field 

Test

Task5: 

Dissemination 

of results to 

key 

stakeholders
Project Objectives

• Task 1: Economic and Steady State Analysis:

• What is the priority?

• What is the business case?

• Task 2: Transient Analysis:

• What is the needed system response?

• How does wind power impact the system response?

• Task 3-4: Turbine simulation and field tests

• What does the response look like?

• How does the response compare to current providers?

• How does the response affect the machine/component life, 

etc.?

• Task 5: Dissemination

• How can these capabilities be adopted?

• Will industry endorse these capabilities?

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Steady-State Modeling Results

120-MW Wind Plant:

Wind plant supplied regulation 2800 of the 3282 hrs 

regulation price exceeded energy.

Wind plant earned an additional $3.5 million or $9.96/MWH 

spread over the plants production ─

– 4% reduction if the plant had to flatten production before selling 

regulation.
Field-testing APC

• Research assumes a single turbine 

can actively control its power within 

different time frames

• Need to test methods to implement this 

on a real turbine to learn:

• What is possible controller performance?

• Bandwidth, settling time, steady-state error

• What are potential upper-bound setting 

constraints?

• Added structural loading

• Interactions with existing control loops, 

resonances

• Compare strengths/weaknesses of 

various APC designs

National Renewable Energy Laboratory Innovation for Our Energy Future

PIX 18279
Simulation and Field-Testing Plan
Design and Tune Control Strategies

Currently being 

simulated and field 

tested
Field-testing results

Evaluate captured power 

against theoretically available

Investigate performance: RMS 

error, settling time, overshoot

Look at effects of APC on 

structural loads

Determine resultant additional 

actuation usage
Schedule

• September-December 2010: Project initiation, 

cooperative research and development agreement.

• January 2011: Active Power Control from Wind 

Power Workshop in Boulder, CO.

• February-March 2011: Project technical kickoff, 

scope breakdown.

• Late 2011: Interim project report.

• October 2010 – April 2011: Next wind season field 

tests.

• Late 2012: Final project report, demonstrations.

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The End Goal

• When tested, and reports show wind turbine 

providing capability satisfactorily...

• It costs too much?

• Additional revenues per wind plant could possibly be very 

high should they choose to participate and market rules are 

correctly designed.

• It cannot behave as other generators?

• Studies may show it providing the finest scale of active 

power control capability on a better quality than other 

generation.

National Renewable Energy Laboratory Innovation for Our Energy Future