NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Contract No. DE-AC36-08GO28308

NWTC Dynamometer and 

Controllable Grid Interface 

Commissioning and Testing of 

General Electric Wind Turbine 

Drivetrain

Cooperative Research and 

Development Final Report

CRADA Number: CRD-14-551

NREL Technical Contact: Scott Lambert

CRADA Report

NREL/TP-5000-72089

July 2018
NOTICE

This work was authored in part by the National Renewable Energy Laboratory, operated by Alliance for 

Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. 

Funding provided by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Wind and 

Water Technologies Office. The views expressed in the article do not necessarily represent the views of the DOE 

or the U.S. Government.

This report is available at no cost from the National Renewable 

Energy Laboratory (NREL) at www.nrel.gov/publications.

U.S. Department of Energy (DOE) reports produced after 1991 

and a growing number of pre-1991 documents are available 

free via www.OSTI.gov.

Cover Photos by Dennis Schroeder: (left to right) NREL 26173, NREL 18302, NREL 19758, NREL 29642, NREL 19795.

NREL prints on paper that contains recycled content.
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This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Cooperative Research and Development Final Report

In accordance with Requirements set forth in Article XI. Reports and Abstracts A.(3), of the 

CRADA agreement, this document is the final CRADA report, including a list of Subject 

Inventions, to be forwarded to the Office of Science and Technical Information as part of the 

commitment to the public to demonstrate results of federally funded research.

Parties to the Agreement: General Electric Company – GE Power & Water

CRADA Number: CRD-14-551

CRADA Title: NWTC Dynamometer and Controllable Grid Interface Commissioning and

Testing of General Electric Wind Turbine Drivetrain

Joint Work Statement Funding Table Showing DOE Commitment:

Estimated Costs NREL Shared Resources

Year 1

Year 2

Modification #1

$ 100,000 .00

$ 300,000.00

$ 400,000.00

TOTAL $ 800,000.00

Abstract of CRADA Work:

This CRADA (1) facilitates commissioning of the new NWTC 5MW dynamometer facility while 

testing a General Electric (Participant) 2.75MW wind turbine drivetrain under loaded conditions, 

(2) facilitates commissioning of the new NWTC the Controllable Grid Interface (CGI) as part of 

testing the GE 2.75MW drivetrain, (3) facilitates further wind turbine drivetrain testing utilizing 

the commissioned dynamometer and CGI test facilities.

Summary of Research Results:

In 2013 the Department of Energy (DOE) and the National Renewable Energy Laboratory 

finished construction of a new wind turbine test facility at the National Wind Technology Center 

(NWTC) south of Boulder, Colorado. This facility augmented the NWTC’s capability for 

dynamometer testing embodied in the 2.5 MW dynamometer.

The new facility enables testing wind turbine drivetrains up to 5 MW – the largest size expected 

to be deployed on land. DOE also provided support for the construction of a Controllable Grid 

Interface (CGI) that is used in conjunction with dynamometer testing. The CGI enables 

engineers to control electrical characteristics of the grid as seen by a drivetrain in the 

dynamometer.
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This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Commissioning of the equipment in the 5 MW dynamometer occurred in two stages: a no-load 

commissioning test and a second “loaded” commissioning test that included commissioning of 

the CGI. To test the dynamometer drivetrain under load, it is necessary to connect it to a wind 

turbine drivetrain. This test configuration has been named Integrated System Test (IST).

NREL completed commissioning test planning and interface equipment design to connect the GE 

drivetrain to the 5MW dynamometer and CGI. This work is documented in “NWTC 5 MW 

Dynamometer & Controllable Grid Interface Commissioning Test Plan”. GE confirmed that the 

test conditions during NREL facility commissioning were acceptable operating conditions for the 

drivetrain. GE prepared a test plan that described drivetrain tests to be conducted during the period 

of GE testing. NREL reviewed the desired test conditions to verify that the 5 MW dynamometer

and CGI had the needed capability. NREL also designed and fabricated hardware needed to 

connect the GE drivetrain to the 5MW dynamometer and provided a 3 MVA transformer.

In September of 2013, NREL finished the installation of the 2.75 MW drivetrain in the 5 MW 

dynamometer with GE technical support.

NREL commissioning tests intended to verify safety, instrumentation, control, and loading 

capabilities of the dynamometer and CGI were conducted according to the test plan. Verification 

of safety includes: Emergency Power Off capability to isolate the dynamometer, CGI, and GE 

drivetrain electrically; Emergency Shut Down capability to quickly stop rotation of the 

dynamometer due to fault conditions; and prevention of overspeed, overtorque, overloading in 

thrust, lateral shear, vertical shear, pitch moment, and yaw moment. Verification of 

instrumentation included measurements of low speed shaft speed, torque, thrust, lateral shear, 

vertical shear, pitch moment, and yaw moment; power into the dynamometer VFD and out of the 

GE drivetrain; voltage, frequency, current, phase angle, harmonic distortion of the CGI. 

Verification of control included: operation of the dynamometer motor in both speed and torque 

control; operation of the non-torque loading device in both force and displacement control in 

each of its five degrees of freedom; and operation of the CGI at voltages and frequencies above 

and below nominal. Verification of loads includes: application of torque and non-torque loads to 

approximately 50% of dynamometer ratings as limited by GE specification of acceptable loads 

on the GE drivetrain.

Following completion of GE testing, NREL prepared a report and produced other related 

documents describing the configuration and results of commissioning tests of the 5 MW 

dynamometer and CGI. The publishing of “Phase 1 Integrated Systems Test and Characterization 

Report for the 5-Megawatt Dynamometer and Controllable Grid Interface” made this 

information available to the public (available at https://www.nrel.gov/docs/fy18osti/63073.pdf). 

Specific findings encountered with the GE drivetrain or other sensitive GE information are 

considered proprietary information and have not be publicly reported.

Additional investigations of the dynamometer performance were published in papers titled, 

“Theoretical and experimental study on gear-coupling contact and loads considering 

misalignment, torque, and friction influences” (available at: 

https://www.sciencedirect.com/science/article/pii/S0094114X15002748?via%3Dihub) and 

“Characterizing the Influence of Abstraction in Full-Scale Wind Turbine Nacelle Testing”

(available at: https://www.nrel.gov/docs/fy16osti/66302.pdf)
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This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.

Subject Inventions Listing:

None

ROI#:

None

Report Date:

June 18, 2018

Responsible Technical Contact at Alliance/NREL:

Scott Lambert

Name and Email Address of POC at Company:

Roger Schonewald, roger.schonewald@ge.com

DOE Program:

Office of Energy Efficiency and Renewable Energy Wind and Water Technologies Office

This document contains NO confidential, protectable, or proprietary information.