Dear all,
I am currently using BeamDyn to perform an IEA-22MWRWT steady-state wind analysis and compare it to Bladed. The steady-state wind analysis is performed from 3 m/s to 25 m/s in 1 m/s increments.
The results show that the standard deviation of the wind turbine operating characteristics becomes very large at wind speeds of 23, 24, and 25 m/s.
A graph of the results is attached.
I would like to know if anyone knows the cause of this problem.
Best regards,
Dear @Wataru.Mochizuki,
It looks like your model is unstable above around 22 m/s.
Are you running the OpenFAST model available from the IEA Wind 22-MW RWT repository: IEA-22-280-RWT/OpenFAST at main · IEAWindSystems/IEA-22-280-RWT · GitHub? Have you changed this model in any way?
Can you clarify how you are running the steady-state wind analysis? Are you running separate simulations with steady wind at each wind speed? If so, at each wind speed are you initializing the rotor speed and blade-pitch angles to their expected values for each wind speed?
Best regards,
Dear @Jason.Jonkman ,
Sorry for the delay in responding.
I have increased the Tolerance for stopping criterion in BeamDyn for the model data in the IEA Wind 22-MW RWT repository.
stop_tol=1.0E-02.
This change was made because the calculations were not converging with the default settings.
The steady-state wind analysis is simulated for each wind speed and the statistics are calculated.
The initial values for rotor speed and blade pitch angle were not changed for each wind speed, and BlPitch=5(deg) and RotSpeed=5.0(rpm) for all wind speed cases.
Best regards,
Dear @Wataru.Mochizuki,
The initial values for rotor speed and blade pitch angle were not changed for each wind speed, and BlPitch=5(deg) and RotSpeed=5.0(rpm) for all wind speed cases.
That is likely your problem. The ROSCO controller used by the IEA Wind 22-MW RWT can get confused and not respond properly if you don’t initialize the blade-pitch angles and rotor-speed near their expected values conditioned on the mean hub-height wind speed. To avoid issues in the controller, we generally recommend setting the initial blade pitch and rotor speed based on their expected (mean) values conditioned on the mean hub-height wind speed you are simulating.
Best regards,
Dear @Jason.Jonkman ,
Setting the initial values for rotor speed and blade pitch angle to the expected values at the respective wind speeds did not avoid this problem.
The time series data is shown below.
Please note that the version of OpenFAST we are using is v.3.5.3.
Please let me know your views.
Best regards,
Dear @Wataru.Mochizuki,
Hope you are doing well.
I am Riad, a wind trbine enthusiast.
Could you please share your servodyn input file ? and ElastoDyn file ?
Because, the rotor speed is quite weird for me.
Best Regards,
Riad
Dear @Riad.Elhamoud ,
My company’s security system makes it difficult to share files publicly using file sharing services such as google drive, onedrive, etc.
Please specify the areas of ElastoDyn and ServoDyn you would like to see and I will copy and paste that section into this chat.
Best regards.
Dear @Wataru.Mochizuki,
Ok No problem.
Please could you share the part of ElastoDyn where the initial conditions are specified as well as the part of the degrees of freedom? Moreover, could you share the part of ServoDyn where the pitch control are specified as well as the part of the nacelle yaw control ?
Best Regards,
Riad
Hi @Wataru.Mochizuki,
I did observe similar instabilities in OpenFAST during the design and subsequent verification studies, see DOI 10.1088/1742-6596/2767/5/052042.
I could finally get the model to stay stable by using UAMod = 4 in AeroDyn15. Can you please confirm that you are also using UAMod=4? If you are, would you mind switching to UAMod=3 and see what happens?
Thanks,
Dear @Pietro.Bortolotti ,
I have set UAMod=4 as you advised and the instability has been resolved.
Thank you very much for your useful information!
@Jason.Jonkman , @Riad.Elhamoud , thank you also for your help!
Best regards,
