An abnormal pitch angle variation in my openfast simulation.

[zujama]

Hello.
I am fairly new to openfast and i am using the tool for my master thesis where coherence is introduced to a stochastic variable wind field and the loads should be examined. My problem is that when plotting the pitch angles of the blades, they are oscillating between 0 and 90 degrees all the period pretty fast. For this i am using the IEA22MW turbine imported from the official source. The Discon.dll i am using is imported from the official openfast page in Github and located properly in same folder as my servodyn.dat as you can see below
"Discon.dll" DLL_FileName
"IEA-22-280-RWT-Semi_DISCON.IN"
"DISCON" DLL_ProcName
default DLL_DT

Here are the changes i tried so far with no success.
I deactivated all Hydrodyn, Mooring, aerodyn, seastate and kept only Servodyn, Elastodyn and inflow in use to simplify the problem.
Then i removed the wind field i generated using Matlab and used steady windfield with HWindSpeed = 15 and 8. At 8 m/s, the pitch angle fluctuate for the first two time steps and stabilize on 0 degree. However, when using HWindSpeed = 15, this chaotic oscillation returns. (In both cases i am changing the initial conditions properly of course)
I also tried to update the Discon.IN file and it did not help. I feel like something regarding the .dll file which is imported from openfast files is wrong but i could not manage to try the one provided by Resco since it require knowledge in compiling (creation of the .dll ). I tried to test the .dll file provided for version 2.8.0 but the simulation did not run at all, probably a matter of version compatibility.
last thing i tried was to set PCMode and VSContrl to 0 to make sure that the control files are the problem, and the initial pitch angle stayed constant when they are disabled.
But now i am out of ideas for what is going wrong.

[jjonkman]

Dear @zujama,

The OpenFAST models of the IEA Wind 22-MW RWT provided on the IEA Wind Systems GitHub repository: https://github.com/IEAWindSystems/IEA-22-280-RWT/tree/main/OpenFAST uses a ROSCO-based controller. ROSCO is not provided through the OpenFAST GitHub repository, but is available through the ROSCO GitHub repository: https://github.com/NREL/ROSCO. (By using the DISCON.dll from the OpenFAST repository, you are not using the correct controller, but rather are using a controller for the NREL 5-MW baseline wind turbine.) Presumably you are using the ROSCO input file from: https://github.com/IEAWindSystems/IEA-22-280-RWT/blob/main/OpenFAST/IEA-22-280-RWT-Semi/IEA-22-280-RWT-Semi_DISCON.IN, which requires ROSCO v2.9.0. You can find a precompiled version of ROSCO v2.9.0 for Windows here: https://github.com/NREL/ROSCO/releases/download/v2.9.0/libdiscon.dll

Best regards,

[zujama]

Dear @jjonkman
Thank you for your respond. It is working now.