Rotor Speed output

Discuss the effects of turbulence on wind turbines and its simulation.

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Luigia.Riefolo
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Rotor Speed output

Postby Luigia.Riefolo » Mon May 29, 2017 10:22 am

Dear all,

I am simulating NTM through Turbsim (Uref=7m/s), concerning the spar buoy wind turbine Hywind.
A problem came up when I checked the output of the Rotor Speed. I have set an initial RotSpeed equal to 8.469 rpm. Is it normal that the RotSpeed jump to a mean value of 11.2 rpm ? Could be the problem in the ServoDyn settings?

Thank you in advance for your kind help

Best regards,
Luigia

RotSpeed_wind_turbulent_7m_s.jpg
RotSpeed_wind_turbulent_7m_s.jpg (31.49 KiB) Viewed 1939 times

Jason.Jonkman
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Re: Rotor Speed output

Postby Jason.Jonkman » Tue May 30, 2017 6:31 am

Dear Luigia,

A mean rotor speed around 8.5 rpm sounds correct for the NREL 5-MW turbine operating at 7 m/s mean wind speed. I'm not sure why you are not seeing that. Have you verified that the mean wind speed at hub height in the FAST simulation is around 7 m/s? Are you calling the standard Bladed-style DLL torque and pitch controller provided for the OC3-Hywind spar buoy model?

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

Luigia.Riefolo
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Organization: Polythecnic of Milan
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Re: Rotor Speed output

Postby Luigia.Riefolo » Tue May 30, 2017 7:16 am

Dear Jason,

Thank you very much for your quick reply.

I have verified the mean wind speed. It is 6.994 m/s, as you can see from the plot here attached.
Furthermore, I have used this settings in ServoDyn input. Please, may you tell me if they are correct?


---------------------- BLADED INTERFACE ---------------------------------------- [used only with Bladed Interface]
"ServoData/DISCON_OC3Hywind_x64.dll" DLL_FileName - Name/location of the dynamic library {.dll [Windows] or .so [Linux]} in the Bladed-DLL format (-) [used only with Bladed Interface]
"DISCON.IN" DLL_InFile - Name of input file sent to the DLL (-) [used only with Bladed Interface]
"DISCON" DLL_ProcName - Name of procedure in DLL to be called (-) [case sensitive; used only with DLL Interface]

Thank you again for your support

Best regards,
Luigia
Attachments
wind velocity time series.jpg
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Jason.Jonkman
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Re: Rotor Speed output

Postby Jason.Jonkman » Tue May 30, 2017 9:33 am

Dear Luigia,

That portion of the ServoDyn input file looks OK. Have you set PCMode = VSContrl = 5 in ServoDyn?

Is the blade-pitch angle remaining at 0 degrees? What generator torque are getting? (I would expect a mean of 15 kNm for this wind speed.)

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

Luigia.Riefolo
Posts: 20
Joined: Tue Sep 13, 2016 2:24 am
Organization: Polythecnic of Milan
Location: Milan
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Re: Rotor Speed output

Postby Luigia.Riefolo » Tue May 30, 2017 9:58 am

Dear Jason,

I have set PCMode = VSContrl = 5 in ServoDyn and the pitch angle remains at 0 degrees.
The generator torque I am getting jump from 15 kNm to 43 kNm, which is the value corresponding to a wind velocity equal to 11.2 m/s.
I have verified the results related to a wind velocity equal to 11.2 m/s and are aligned to the results from NREL report.
My doubt is that there somenthing wrong in my input files (even if the case with Uref=11.2 m/s works well). So when the wind velocity is less than 11.2 m/s something wrong happens. I really can not understand where could be the problem. Do you have any other suggestion to give me, in order to check other parametrs that could vary my results?

Thank you very much for your time

Best regards,
Luigia
Attachments
GenTq.jpg
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Jason.Jonkman
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Re: Rotor Speed output

Postby Jason.Jonkman » Tue May 30, 2017 12:15 pm

Dear Luigia,

It sounds like your ServoDyn inputs are set appropriately. And the generator torque looks to be consistent with the rotor speed, but corresponding to what I would expect from a higher mean wind speed. It is like there is more aerodynamic torque than I would expect for the mean wind speed. Have you disabled the wake/induction model in AeroDyn? In AeroDyn v15, WakeMod should be set to 1 for simulations involving operation of the turbine. Are you using WakeMod = 0 instead of 1?

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

Luigia.Riefolo
Posts: 20
Joined: Tue Sep 13, 2016 2:24 am
Organization: Polythecnic of Milan
Location: Milan
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Re: Rotor Speed output

Postby Luigia.Riefolo » Thu Jun 01, 2017 3:18 am

Dear Jason,

I have solved the problem thanks to your help. I have enabled WakeMod setting it to 1, obtaining a correct mean value of the Rotor Speed and of Generator Torque for Uref=7m/s.
Is it correct my AeroDyn input? Should I also set SkewMod to 2 ? Furthermore, I read from another post that it is needed to recompile AeroDyn to the new version to do not get the error 'no valid value of phi'. The latest update of AE is already available?

====== Blade-Element/Momentum Theory Options ====================================================== [used only when WakeMod=1]
1 SkewMod - Type of skewed-wake correction model (switch) {1=uncoupled, 2=Pitt/Peters, 3=coupled} [used only when WakeMod=1]
True TipLoss - Use the Prandtl tip-loss model? (flag) [used only when WakeMod=1]
True HubLoss - Use the Prandtl hub-loss model? (flag) [used only when WakeMod=1]
true TanInd - Include tangential induction in BEMT calculations? (flag) [used only when WakeMod=1]
False AIDrag - Include the drag term in the axial-induction calculation? (flag) [used only when WakeMod=1]
False TIDrag - Include the drag term in the tangential-induction calculation? (flag) [used only when WakeMod=1 and TanInd=TRUE]

Thank you very much for your support

Best regards,
Luigia

Jason.Jonkman
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Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
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Re: Rotor Speed output

Postby Jason.Jonkman » Thu Jun 01, 2017 6:55 am

Dear Luigia,

Your AeroDyn inputs look fine. There is some guidance on the choice of SkewMod provided in Section 6.4 of the draft AeroDyn User's Guide and Theory Manual: https://nwtc.nrel.gov/system/files/Aero ... 15.04a.pdf.

Yes, the BEMT algorithm in AeroDyn v15.04 is more robust than in earlier versions. We've recently uploaded AeroDyn v15.04 here: https://nwtc.nrel.gov/AeroDyn, but we have not yet released an update to FAST v8 with this version of AeroDyn.

I'm not sure what you mean by "AE".

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


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