Availability of file .dll from FAST v7 to v8


I am building a model FAST v8 from a model FAST v7, and I am having trouble when running operating load cases.
The software is running without any error message but the controller doesn’t work properly: variable speed control is active below rated but blade pitch control is inactive (blade pitch angle remains 0°) for wind speeds above rated.
I had no problem running FAST v7 with this controller, hence my question is: does the .dll file I used for FAST v7 need to be modified when used for FAST v8?

Thank you by advance.

Best regards,

The DLL shouldn’t have to be changed. Do you have PCMode=5 in your ServoDyn input file? And is TPCOn < TMax?

Thanks for your prompt reply.

I indeed have PCMode=5 and TPCon=0 (and the time to start pitch maneuver at 9999.9). In the results, HSS speed and output power largely exceed rated values so pitch control should be active.
I don’t see any other reason than a deflect in the file .dll.

Best regards,

Dear Yohan,

As Bonnie said, the DLL shouldn’t need to be changed when upgrading from FAST v7 to FAST v8. I’m not sure what is causing the problem in your case. To isolate the problem, I first suggest that you try running a simulation in both FAST v7 and FAST v8 without the controller. That is, if you disable the generator degree-of-freedom (GenDOF = False), do you obtain the same result from FAST v7 and FAST v8?

Best regards,

Dear Jason Jonkman,

Thanks for your help.

I ran calculations disabling the controller and GenDOF, and the resulting time series are identical between v7 and v8.
I also ran calculations enabling GenDOF and only variable speed control: time series and statistics are still very close (mean values and standard deviations of RotSpeed, RotThrust, RotTorq, blade deflections, GenSpeed, GenTq, GenPwr, tower base loads… are less than 1% different) between v7 and v8.

Maybe the controller was adapted to the compiled FATS v7 executable I have. I may ask for a new version of the DLL file.

Best regards,


One other thing you should check: make sure that the “Bladed Interface” inputs in the ServoDyn input file are set to whatever was hard-coded in the FAST v7 version you are using.
I know some people also hard-coded other variables to pass to the interface, so maybe your FAST v7 version is a little different…

Dear Bonnie Jonkman,

I tried to change the “Bladed Interface” inputs but it didn’t work. I indeed think my FAST v7 version is different and I will ask for a controller adapted to FAST v8.

Thanks for your time,