Simulation of an offshore Wind turbine 5MW based DFIG

Dear Ali,

You should apply the MBC3 transform if you wish to derive a linear time-invariant model from a periodic linear model that has blade degrees of freedom enabled in a rotating frame of reference (for rotors with three blades). Your model has the blade flapwise-bending modes enabled, which are in a rotating frame, so, “yes”, you should apply MBC3 (assuming your rotor has three blades).

Best regards,

Thank you very much for your reply
Please let me know If the GenDOF and and DTrDOF are not in the rotating frame, and if the fixed reference frame is linked to the hub

Dear Ali,

While the generator and drivetrain rotate, there are not separate values for each blade, so, these are DOFs are considered in the fixed frame for the purposes of the MBC transformation.

Best regards,

Dear Mr Jason can you please qives the explantations of these stuffs or confirm:

  1. If Gendof is the vitesse or the dispalcment of the generateur
  2. If flap-wise is the deplacment of the blade in the direction normal to the rotor plan
  3. If fore-aft is the tower displacment in the plan normal to the rotor
  4. Also If you can explain me the vocabulary corresponding to fodation DOFS: yaw, sway, surge, role, pitch
  5. if we conduct for example linearization with flap-wise mode, the states obtained are: blade displcment and velocity

Sincerely yours

Dear Ali,

Here are my answers to your questions:

  1. The generator DOF (GenDOF) enables/disables the rigid-body rotation of the generator. If GenDOF is enabled, the generator is free to accelerate/decelerate based on the torques applied. If the GenDOF is disabled, the acceleration of the generator will be zero, the speed will be fixed (at its initial speed), and the azimuth will vary linearly.
  2. Flapwise is the direction normal to the principle axis of bending nominally aligned with the chord.
  3. Fore-aft is the direction that pushes the rotor into and out of the wind when the yaw angle and wind direction are zero.
  4. See Figure 20 in the old FAST v7 User’s Guide for a clear illustration of the platform DOFs: nwtc.nrel.gov/system/files/FAST.pdf.
  5. Yes.

Best regards,

Thank you for these explantations

Can we said that the DOGs of the foundation are: the displacements and rotations around the three axes of the repere located at the fondation

Sincerely yours

Dear Ali,

Yes, I agree.

Best regards,

Dear Jason,

I have a question concerning your about Ali’s question (5)if we conduct for example linearization with flap-wise mode, the states obtained are: blade displacement and velocity

There are 2 flapwise mode(FlapDOF1 and FlapDOF1), when linearizing the FAST, I enabled these 2 DOFs. then I obtained 4 states, how to explain these states, or can FAST output these 4 states?

Best regards,
Cheng

Normally each Flap-wise DOF will give you 6 states which are the displacments and velocities of the corresponding DOF

I hope this will help you

Dear Ali,

Yes, you are right, I wrote wrong, each Flap-wise DOF will give 6 states.

If I enable FlapDOF1 and FlapDOF2 can I get the 12 states from FAST?

Best regard,
Cheng

Dear Cheng,

Yes, if you enable FlapDOF1 and FlapDOF2 for a 3-bladed rotor, you will get 12 states i.e. the displacement and velocity of each flapwise mode of each blade ( 2 x 2 x 3 = 12).

Best regards,

Dear Jason,
Yes, I agree.
It seems that FAST can not output those states. e.g.

Row/column 4 = 1st flapwise bending-mode DOF of blade 1 (internal DOF index = DOF_BF(1,1)) Row/column 5 = 1st flapwise bending-mode DOF of blade 2 (internal DOF index = DOF_BF(2,1)) Row/column 6 = 1st flapwise bending-mode DOF of blade 3 (internal DOF index = DOF_BF(3,1))

If I enable FlapDOF1 only, the displacement can be approximated as TipDxb1, If I enable both FlapDOF1 and FlapDOF2, FAST cannot output those states, am I right?

Best regards,
Cheng

Dear Cheng,

FAST can output the states for both the first and second flapwise modes. The blade displacement state for a given mode is not equivalent to the tip-displacement output (although they are, of course, related).

Best regards,

Dear Mr Jason
I hope you are well
Tell me please why are you called the NREL’s 5MW WT as a benchmarking model
As well as the torque and GSPI why are you called they as reference controllers
As I know the word benchmarking must verify somes standard norms,which norms have benn verifyed by this model and their controllers

Sincerely yours

Dear Ali,

I’m sorry, but I’m not sure I understand your question.

I typically use the word “baseline” to refer to the specified NREL 5-MW turbine and its controller. I use the word “baseline” to distinguish from further developments/improvements by others.

Best regards,

I found in some articles the model os refered as" NREL’s 5MW Benchmarking WT’’

Can you please tell me what about this nomination

Dear Ali,

I’m not sure. Perhaps the term “benchmarking” is used because the NREL 5-MW baseline wind turbine has been used a lot in benchmarking exercises e.g. the IEA Wind Task 23 and Task 30 Offshore Code Comparison Collaboration (OC3), OC3 Continued (OC4), and OC4 plus Correlation (OC5) projects?

Best regards,

Thank you for your reply
Tell me again on how are you based to choose the step time of integration DT 0.0125 s

Sincerely yours

Dear Ali,

See the following FAQ for guidance on selecting a time step for FAST v7: wind.nrel.gov/designcodes/FAQ.html#FASTTimeStep. (FAST v8 has some further numerical options, but the FAQ still applies to ElastoDyn and AeroDyn.)

Best regards,

Thank you so much

Please explain me what about the two DOF the rotor tail furl

Sincerely yours