DTU 10-MW Reference Wind Turbine

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Jason.Jonkman
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Re: DTU 10-MW Reference Wind Turbine

Postby Jason.Jonkman » Mon May 25, 2020 7:18 am

Dear Abhinay,

I'm not sure I really understand what the text you are quoting is saying.

Regardless, the tower influence model in AeroDyn v14 is limited to a fixed undeflected/undisplaced position of the tower, so, I would not enable AeroDyn v14's tower influence model for floating wind turbines, which have the potential for substantial platform displacement or tower deflection. AeroDyn v14 is no longer being worked on and will be deprecated soon.

That said, AeroDyn v15 has more functionality than AeroDyn v14 and AeroDyn v15 does consider the impact of floating platform motions and tower deflection on the tower influence 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

Lixian.Zhang
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Re: DTU 10-MW Reference Wind Turbine

Postby Lixian.Zhang » Wed Jun 17, 2020 8:44 pm

Dear Dr.Jason
Thanks for reading my email.
I'm using openfast v2.3 to simulate the IEA 10 MW reference wind turbine. And I used the DISCON_IEA_offshore.dll controller. However,I faced some problems when I simulated the rated wind speed condition(turbulent wind). The simulation can run but the blade pitch is zero during the simulation under the rated wind speed, which casue large rotor thrust force and genrator power (over 12 MW). Aslo, when i tried to simulate the over-rated wind speed condition, the simulation aborted. I have uploaded some input files and results.Can you give me some advice?I'm not familiar with controller, maybe the problem of the controller?
inputfile.rar
(242.2 KiB) Downloaded 22 times

总的.png
总的.png (194.82 KiB) Viewed 552 times


Thanks a lot in advance!
Best regards
Lixian Zhang

Jason.Jonkman
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Re: DTU 10-MW Reference Wind Turbine

Postby Jason.Jonkman » Thu Jun 18, 2020 6:51 am

Dear Lixian,

I'm not familiar enough with the DTU 10-MW reference wind turbine OpenFAST model that you are simulating to comment much, but I don't see that you are referencing the DISCON_IEA_offshore.dll in your ServoDyn input file (instead, you set DLL_FileName = "controller\DTU_10MW_Braceless_Controller_Lib.dll"); could that be a problem? Also, are the initial conditions you've set (RotSpeed = 9 rpm, BlPitch = 0.0) the expected values for the mean wind speed you are simulating?

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

Lixian.Zhang
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Re: DTU 10-MW Reference Wind Turbine

Postby Lixian.Zhang » Fri Jun 19, 2020 8:12 pm

Dear Dr.Jason
Thanks for your quick response.
I'm so sorry that I uploaded the wrong input files of servodyn. I think that I use the right path of dll file into servodyn file after I doubled checked the input files. I also found some simliar questiones in the fourm, and try to use "dtu_we_controller" into openfast. However, simliar problem happened. The controller can not be loaded into either openfast 32-bit and 64-bit. I found that no matter how I changed the intial pitch angle, the output pithc angle will become zero and the simualation will be aborted in seconds under over rated wind speed(18 m/s:constant wind).
bladepitch.png
bladepitch.png (56.55 KiB) Viewed 525 times

I downloaded the input files of IEA 10 MW wind turbine including the controller in github afew mothons ago. I'm wondering if I use the wrong dll file for 10MW controller. Is there any newest version for the dll of 10 MW?
IEA-10.0-198-RWT_ServoDyn.rar
(3.03 KiB) Downloaded 13 times

Thank you very much!

Best regards
Lixian Zhang

Roger.Bergua
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Re: DTU 10-MW Reference Wind Turbine

Postby Roger.Bergua » Mon Jun 22, 2020 2:11 pm

Dear Lixian,

I have been using the IEA-10.0-198-RWT (based on the offshore DTU 10-MW wind turbine design) within the OC6 project.

At the beginning I was also having problems with the blades pitch. The IEA-10.0-198-RWT uses the ROSCO controller. You can find a 64-bit version of this controller already compiled in the next GitHub repo: https://github.com/IEAWindTask37/IEA-10.0-198-RWT/tree/master/controller/dll_windows

In order to run this controller, you will need the controller parameters file (*_DISCON.IN). You can find this file in the same GitHub repository that I was commenting: https://github.com/IEAWindTask37/IEA-10.0-198-RWT/tree/master/openfast

Note that the wind turbine is a direct-drive wind turbine. Accordingly, you can see that line 76 in the parameters file defines the gearbox ratio as 1:

Code: Select all

1.0                 ! WE_GearboxRatio   - Gearbox ratio [>=1],  [-]

At this point, there is something very important: line 79 of the parameters file defines the location of the text file IEA-10.0-198-RWT_Cp_Ct_Cq.txt that contains the rotor performance tables (Cp, Ct, Cq). You must edit the parameters file and point to the proper location in your computer. I recommend using an absolute path rather than a relative path when pointing to this file. For example, in my case, line 79 looks like this:

Code: Select all

"C:\OC6_PhaseII\OpenFAST_model\IEA-10.0-198_Wind_Turbine\ServoData\IEA-10.0-198-RWT_Cp_Ct_Cq.txt"      ! PerfFileName      - File containing rotor performance tables (Cp,Ct,Cq)

Note that this IEA-10.0-198-RWT_Cp_Ct_Cq.txt file is also available at: https://github.com/IEAWindTask37/IEA-10.0-198-RWT/tree/master/openfast

I guess this should solve your problems with the controller. Please, let me know if it's not the case.

Roger

Lixian.Zhang
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Re: DTU 10-MW Reference Wind Turbine

Postby Lixian.Zhang » Tue Jun 23, 2020 8:48 pm

Dear Dr. Roger
Thanks for your reply!
Now, It's working after I used the ROSCO controller according to your comments. Thanks again!
I have another questions when using ROSCO controller.
When I simulated the constant wind with wind speed (11.4 m/s) for monopile wind turbine, the simulation results looked pretty good. However, when I simulated turbulent wind(11.4 m/s), it seams that some numerical instabilities occurred in generator power(Figure 1).And for overrated wind speed (18 m/s:constant wind ), the simulation results are also quite strange(Figure 2).
11.4ms.png
11.4ms.png (217.74 KiB) Viewed 461 times

Figure 1 simulation results of turbulent wind(11.4 m/s)

18.png
18.png (86.12 KiB) Viewed 461 times

Figure 2 simulation results of constant wind (18 m/s)

I would be appreciate if you can give me some suggestions.
Anyway, thank you very much!
Best regards
Lixian Zhang

Roger.Bergua
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Re: DTU 10-MW Reference Wind Turbine

Postby Roger.Bergua » Wed Jun 24, 2020 2:23 pm

Dear Lixian,

I'm glad that the controller is finally working at your side.

Regarding the issues observed, I guess that a developer of the ROSCO controller would be the most suitable person to explain the specific behavior that you are observing. Note that there is a GitHub repository for the ROSCO controller: https://github.com/NREL/ROSCO. You may contact them to better understand what could be the reason for your results.

Hopefully they can address your doubts with the controller performance.

Roger

Lixian.Zhang
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Organization: Dalian University of technology
Location: China

Re: DTU 10-MW Reference Wind Turbine

Postby Lixian.Zhang » Wed Jun 24, 2020 6:33 pm

Dear Dr. Roger

Thank you very much!

best regards
Lixian Zhang

Nikhar.Abbas
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Re: DTU 10-MW Reference Wind Turbine

Postby Nikhar.Abbas » Thu Jun 25, 2020 10:12 am

Hi Lixian,

Glad to see that you got the ROSCO controller working. A few quick questions: Is the x-axis here time-steps? Or time?

Also, I am not sure I see what you mean when you say that there are "some numerical instabilities in the generator power". Are you referring to the drops in generator power (e.g. around 1600 time-steps)? If so, these are likely attributed to the turbine dipping into region two - perhaps tuning the controller or the set-point smoother could improve this behavior a bit, but it does not look abnormal.

As far as the 18m/s simulation (Figure 2), this is certainly strange and something that I have not seen before. I just ran a 10 minute simulation at 18 m/s and am not seeing similar results (shown below). I also just pulled the most recent IEA 10MW model before running. Have you changed anything in the model, other than file paths and wind speeds?

Screen Shot 2020-06-25 at 10.05.27 AM.png
Screen Shot 2020-06-25 at 10.05.27 AM.png (152.79 KiB) Viewed 425 times

Thanks,
Nikhar

Lixian.Zhang
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Location: China

Re: DTU 10-MW Reference Wind Turbine

Postby Lixian.Zhang » Thu Jun 25, 2020 8:34 pm

Dear Dr. Nikhar

Thanks for your reply!
Sorry about the vague, the X-axis is referred to the simulation time, not time step. The simulation time is 5000s.

1. Yes, "some numerical instabilities in the generator power'' means the drops in the generator power(1600 s) ,in the turbulent wind simulation.
2. For 18 m/s simulation, the simulation results seems quite good in the first 1800s. However, the results are quite strange after 1800s. I didn't change anything for IEA 10 MW wind turbines. I'm not familiar with the controller before. Maybe not the controller issues? I will download the recent model of IEA wind 10MW in GitHub and to see if the same problems happened.

I would be appreciate it if I can receive you reply.
Thanks again!

Best regards
Lixian Zhang

Abhinay.Goga
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Re: DTU 10-MW Reference Wind Turbine

Postby Abhinay.Goga » Mon Jun 29, 2020 6:19 am

Dear Jason and Matt,

For the regular wave simulation on OO-star semi floater there is a strange behavior. A sudden jump in the mooring line tensions (after 512secs) but no effect on platform displacements. LIFES50+ project also mentioned such behavior in their report. Could you explain the cause for such instability?

Thank and regards
Abhinay Goga
Attachments
Regwave Chain observations.jpg
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Nikhar.Abbas
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Re: DTU 10-MW Reference Wind Turbine

Postby Nikhar.Abbas » Tue Jun 30, 2020 5:22 pm

Hi Lixian,
I am not currently able to re-construct your results. I am running OpenFAST in single precision with a 64 bit architecture and the most recent version of ROSCO. My results are below. Let me know if if your problems persist after updating your IEA 10MW model.

Also, just to note, the power is slightly offset from 10MW in these results - this is due to a bug in how the rated torque was calculated for the DISCON.IN file in this model. I've talked to the person managing this and it will be remedied soon.

Figure_1.png
Figure_1.png (34.5 KiB) Viewed 357 times


Nikhar

Matt.Hall
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Re: DTU 10-MW Reference Wind Turbine

Postby Matt.Hall » Tue Jun 30, 2020 10:09 pm

Dear Abhinay,

I appreciate you bringing this up and sharing the illustrative plots. This has come up before, and it's tricky because I can't think of anything in MoorDyn that would cause a change in behavior partway through a simulation. Other instances of this are documented in these threads:
viewtopic.php?f=4&t=2045&hilit=moorDyn+time+step
viewtopic.php?f=3&t=2348
When the change occurs seems to depend on the time step size, and it only seems to be a problem in some versions of FAST/OpenFAST.

Could you let us know what version of FAST/OpenFAST you're using, and what MoorDyn time step size (dtM) you've set?

If this is occurring with the current version, we will try to replicate the problem and investigate further.

Best,
Matt

Abhinay.Goga
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Re: DTU 10-MW Reference Wind Turbine

Postby Abhinay.Goga » Wed Jul 01, 2020 4:56 am

Dear Matt,

The previous simulations were performed with FAST v8.16 and dtM 0.001. Following your comments in attached thread, I ran a new simulation with OpenFAST v2.3.0 and increased MoorDyn time step (dtM) to 0.0001. Yet the behavior remains same after 512secs and surprisingly the rise in magnitude seems a bit higher compared to the one with FAST v8.16.

Kind regards
Abhinay Goga
Attachments
regwave behavior.jpg
regwave behavior.jpg (96.27 KiB) Viewed 342 times

Matt.Hall
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Re: DTU 10-MW Reference Wind Turbine

Postby Matt.Hall » Thu Jul 02, 2020 3:25 pm

Dear Abhinay,

We traced this problem with the tensions back to how the time variable is stored in MoorDyn. It seems that the existing single-precision float causes problems with the interpolation/extrapolation of fairlead kinematics when the simulation time reaches a certain point (in this case 512 s). I was able to solve the problem by changing the variable to double precision. (I wish I had fixed this years ago, but unfortunately I did very little maintenance of the Fortran version of MoorDyn prior to joining NREL.)

If I remember right, you have been compiling OpenFAST yourself. In that case, you can access the updated code here: https://github.com/mattEhall/openfast/tree/MDmods

We will get this fix included in the next release of OpenFAST.

Thanks again for bringing this issue to our attention.
Matt


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