Power coefficient/Aerodynamic torque

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Sina.Ameli
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Power coefficient/Aerodynamic torque

Postby Sina.Ameli » Tue Sep 24, 2019 9:45 pm

Dear Dr. Jonkman,

I need the power coefficient or aerodynamic torque output related to the 5MW offshore WT. Could you tell me what are the outputs for them in the outlist in Matlab? In some of messages I found out that RotCp is the output for power coefficient but I couldn't see it in the list of output!

Thanks
Best regards,
Sina

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Re: Power coefficient/Aerodynamic torque

Postby Jason.Jonkman » Wed Sep 25, 2019 6:50 am

Dear Sina,

I'm assuming you are referring to the Simulink interface of FAST v8 or OpenFAST. The outputs sent out of the FAST S-Function (OutData) are the same outputs written to the time-series output file, as defined by the inputs specified in each FAST module.

RotCp was an old output from FAST v7 not available in FAST v8 or OpenFAST. I would now recommend using AeroDyn v15 output RtAeroCp for aerodynamic power coefficient of the rotor and RtAeroMxh for the aerodynamic torque.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Sina.Ameli
Posts: 38
Joined: Mon Oct 15, 2018 11:23 am
Organization: FSU
Location: Florida

Re: Power coefficient/Aerodynamic torque

Postby Sina.Ameli » Wed Sep 25, 2019 7:41 am

Dear Dr. Jonkman,
Thanks for your prompt response. Actually I have two questions.

1- I cannot see any "RtAeroMxh" ,in the OutList in matlab, which lists 99 output parameters for test 24 in FAST 8. You mentioned this is the output of AeroDyn v.15. Where are its output located to enter them to the Matlab?
2-Is it possible to give a fixed value of the rotor speed and wind speed but variable pitch angle and then get the value of aerodynamic torque? What I mean is that the aerodynamic torque has only one time-varying parameter and based on it, FAST sends me its value during the simulation.

Thanks,
Best regards,
Sina

Jason.Jonkman
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Re: Power coefficient/Aerodynamic torque

Postby Jason.Jonkman » Wed Sep 25, 2019 8:46 am

Dear Sina,

Regarding (1), The AeroDyn v15 outputs are set in the AeroDyn primary input file. In Test24, this is the file named, "CertTest/5MW_Baseline/NRELOffshrBsline5MW_OC3Hywind_AeroDyn15.dat".

Regarding (2), yes. To fix the rotor speed, disable the generator and drivetrain degrees of freedom in ElastoDyn (GenDOF = DrTrDOF = False). To fix the wind speed, use WindType=1 in InflowWind. You can vary the blade-pitch linearly by setting the override pitch maneuver inputs in the ServoDyn input file.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Sina.Ameli
Posts: 38
Joined: Mon Oct 15, 2018 11:23 am
Organization: FSU
Location: Florida

Re: Power coefficient/Aerodynamic torque

Postby Sina.Ameli » Fri Sep 27, 2019 8:23 am

Dear Dr. Jonkman,
Thanks for your reply. I made those signals output but when I run the "Run_OpenLoop.m" for test 24, it gives me this error:

Error using Run_OpenLoop (line 30)
Error reported by S-function 'FAST_SFunc' in 'OpenLoop/FAST Nonlinear Wind
Turbine/S-Function':
FAST_Solution:FAST_AdvanceStates:AD_UpdateStates:BEMT_UpdateStates(node 5, blade
1):BEMT_UnCoupledSolve:DeterminePhiBounds:There is no valid value of phi for these
operating conditions! Vx = -1.1284, Vy = 22.627, rlocal = 11.757, theta = 0.23218

I also have another question about initialization. I need to initialize the blade pitch angles (all of them) not to start at zero. How can I initialize them?

Thanks,
Best regards,
Sina

Jason.Jonkman
Posts: 4280
Joined: Thu Nov 03, 2005 4:38 pm
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Re: Power coefficient/Aerodynamic torque

Postby Jason.Jonkman » Fri Sep 27, 2019 9:35 am

Dear Sina,

There were issues in AeroDyn v15.03 within FAST v8.16 that led to the error "no valid value of phi" in some cases. However, these issues have been fixed in AeroDyn v15.04 and newer in OpenFAST. I suggest you upgrade to OpenFAST: https://github.com/OpenFAST/openfast. The Simulink-OpenFAST interface has been developed, but it is sitting in a pull request, which has not yet been merged (I'm not sure what the hold up has been): https://github.com/OpenFAST/openfast/pull/204.

The initial blade-pitch angles for each blade are set in the "Initial Conditions" section of ElastoDyn input file.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Sina.Ameli
Posts: 38
Joined: Mon Oct 15, 2018 11:23 am
Organization: FSU
Location: Florida

Re: Power coefficient/Aerodynamic torque

Postby Sina.Ameli » Sun Sep 29, 2019 10:14 pm

Dear Dr. Jonkman,
Thanks for your prompt response and sending me those links. Regarding the openfast-master file, when I run the "Run_OpenLoop.m" I get this error:
Error using Run_OpenLoop (line 30)
Error reported by S-function 'FAST_SFunc' in 'OpenLoop/FAST Nonlinear Wind
Turbine/S-Function':
FAST_InitializeAll:FAST_Init:FAST_ReadPrimaryFile:OpenFInpFile:The input file,
"..\..\CertTest\Test01.fst", was not found.
I had a look at the openfast-master files, it seems there is no CertTest in them.
Regarding the second link, could you tell me what is it?
Thanks
Best regards,
Sina

Jason.Jonkman
Posts: 4280
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
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Re: Power coefficient/Aerodynamic torque

Postby Jason.Jonkman » Mon Sep 30, 2019 6:44 am

Dear Sina,

In the transition from FAST v8 to OpenFAST, what used to be the CertTest of FAST v8 has been changed to the regression tests (r-test) of OpenFAST: https://github.com/OpenFAST/r-test.

I'm not sure I understand your second question; are you asking about the Simulink Pull request? OpenFAST development happens within github. See the github workflow documentation for more information: https://openfast.readthedocs.io/en/mast ... kflow.html.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Sina.Ameli
Posts: 38
Joined: Mon Oct 15, 2018 11:23 am
Organization: FSU
Location: Florida

Re: Power coefficient/Aerodynamic torque

Postby Sina.Ameli » Mon Sep 30, 2019 7:55 am

Dear Dr. Jonkman,
Thanks for your prompt response. So far, you have sent me several files including "openfast-master", and "r-test". Now, I am a little confused. The tests located in a different place with different names, while the "Run_OpenLoop.m" asks me for "CertTest"! What I need is to plot the power coefficient and aerodynamic torque in Matlab related to test 24. Could you help me ease this procedure?
Thanks
Best regards,
Sina

Jason.Jonkman
Posts: 4280
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
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Re: Power coefficient/Aerodynamic torque

Postby Jason.Jonkman » Mon Sep 30, 2019 8:53 am

Dear Sina,

My guess is you obtained Run_OpenLoop.m from FAST v8, not OpenFAST. The Master branch of OpenFAST does not yet support the Simulink interface. Instead, the Simulink interface was added through Pull Request #204, which has not yet been merged into the Dev(elopment) (or Master) branches of OpenFAST. You'll have to merge the changes from #204 into your branch of OpenFAST in order to use the Simulink interface.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Sina.Ameli
Posts: 38
Joined: Mon Oct 15, 2018 11:23 am
Organization: FSU
Location: Florida

Re: Power coefficient/Aerodynamic torque

Postby Sina.Ameli » Mon Sep 30, 2019 2:43 pm

Dear Dr. Jonkman,
Thanks for your reply and online supports. Let's discuss a little analytically. I plotted the power coefficient (CP) in the closed-loop system when the wind speed is below the rated value (10m/s) with the TI around 25%, and the controller tries to regulate the rated generator speed. Weirdly, I got this CP:
CP.PNG
CP
CP.PNG (76.07 KiB) Viewed 107 times

while the CP in wind turbines cannot go beyond 0.45. On the other hand, its plot above the rated value are below 0.45 like this (wind speed is 18m/s):
CP_above_rated.PNG
CP_above_rated
CP_above_rated.PNG (61.48 KiB) Viewed 107 times

Thanks,
Best regards,
Sina

Jason.Jonkman
Posts: 4280
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Power coefficient/Aerodynamic torque

Postby Jason.Jonkman » Mon Sep 30, 2019 3:55 pm

Dear Sina,

I'm not sure which power coefficient output from FAST / OpenFAST you are plotting (in general, I would recommend outputting RtAeroCp from AeroDyn v15). Regardless, as has been discussed on this forum, by nature of its calculation within the aero-elastic solution, I would only use the power coefficient output in a time-averaged sense to avoid apparent violations in the Betz limit that may occur instantaneously as a result of the calculation approach. The instantaneous values are effected by rotor acceleration / deceleration, and so, can instantaneously exceed the Betz limit.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Sina.Ameli
Posts: 38
Joined: Mon Oct 15, 2018 11:23 am
Organization: FSU
Location: Florida

Re: Power coefficient/Aerodynamic torque

Postby Sina.Ameli » Tue Oct 01, 2019 8:37 am

Dear Dr. Jonkman,
Thanks again for your prompt response. I used FAST 8 and Aerodyn v15.03!
Best regards,
Sina


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