Linear model DTU 10MW Triple spar

Wind & Water Controls
1

Dear readers,

I’m asking advice about acquiring a linear model of the DTU 10MW Floating Wind Turbine on a triple spar platform. I want to implement an experimental non-linear controller for floating wind turbines in FAST, but for designing the controller a linear model would be helpful.

The FAST files supplied to me are for FAST v8 with AeroDyn v14. However, the linearization function in FAST doesn’t help, because it uses AeroDyn v15.

Then I tried different identification methods in Matlab by acquiring input and output data. I changed the pitch around a steady state under steady conditions and recorded the rotor speed and fore-aft movement. The problem is that FAST doesn’t seem to handle random binary signals well, which are regularly used as an input signal for identification. Other signals didn’t give an accurate model.

What is the best way forward to acquire a linear model? Is there a way to make the linearization from FAST work, or are there better identification methods available for this?

Thanks in advance,
Jan Berens

2

Dear Jan,

If your only issue is that your model uses AeroDyn v14, but the linearization functionality is only available in AeroDyn v15, I would simply upgrade your AeroDyn v14 model to v15.

Please note that we have recently added linearization functionality in OpenFAST for floating offshore wind turbines, including linearization of HydroDyn and MAP++ (in addition to the linearization of wind turbine related modules previously available). See our IOWTC 2018 paper for more information: nrel.gov/docs/fy19osti/71865.pdf. We presented the tentative verification results at the DeepWind 2019 conference in January. We are currently finalizing the verification results and documentation before the public release.

Best regards,

3

Dear mr Jonkman,

Thanks a lot for your reply. I will try both approaches. Is there an easy way to convert the input files from aerodyn v14 to v15? Or is this just done manually? Is there a way to get a notification for the release of said documentation?

Thanks again,
Jan

4

Dear Jan,

NREL has provided MATLAB scripts to convert from AeroDyn v14 to v15. See the section titled MATLAB Conversion Scripts in the FAST v8 ReadMe file: wind.nrel.gov/nwtc/docs/README_FAST8.pdf.

All current FAST work happens through OpenFAST: github.com/OpenFAST/openfast. You can follow the various developments there.

Best regards,