5MW FOWT linearization issue

Wind & Water General
47

Dear Dr. @Jason.Jonkman

Thanks a lot for your prompt response.
By

you mean that the generator torque is not constant because I did not set VS_RtGnSp, VS_Rgn2K, and VS_SlPc to 9999.9E-9 in the ServoDyn input file, don’t you?

I missed that detail before, but I modified it now. Then, after MBC transformation, I eliminated the rows and columns in AvgA, AvgB and AvgC matrices that correspond to the generator azimuth state. Now, it looks better, thanks to your advice. I have some other questions though.

  1. In the eigSol that results from the MBC transformation, are the natural frequencies and the damping ratios arranged to a certain order that correspond to each of the activated DOFs? If I am not mistaken, I think they follow the same order of DOFs in ElastoDyn input file.

  2. I have 4 DOFs activated, but I only get 3 natural frequencies after the MBC transformation, although it is mentioned here Learizing Baseline 5MW Wind Turbine with FAST - #2 by Jason.Jonkman that “The generator DOF results in a rigid-body mode, which in MBC3 shows up as a pair of zero-valued (or near-zero-valued) frequencies with +/- inf damping”. Is there an explanation for that?

  3. In HydroDyn input file, I set ExctnMod and RdtnMod to 0, which means that the hydrodynamic contribution is not included in the dynamics matrices, doesn’t it?. To consider their effect, ExctnMod and RdtnMod should be set to 2 instead, right? May you share the *.ss file for the OC3 to serve as a reference, please?

Best regards,