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Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Thu Jul 13, 2017 2:09 pm
by Jason.Jonkman
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,

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Fri Jul 14, 2017 8:08 am
by Ali.Elyaakoubi
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

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Fri Jul 14, 2017 8:52 am
by Jason.Jonkman
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,

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Sat Feb 17, 2018 6:40 am
by Ali.Elyaakoubi
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

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Sat Feb 17, 2018 3:24 pm
by Jason.Jonkman
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: https://nwtc.nrel.gov/system/files/FAST.pdf.
5) Yes.

Best regards,

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Mon Feb 19, 2018 11:30 am
by Ali.Elyaakoubi
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

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Tue Feb 20, 2018 6:18 am
by Jason.Jonkman
Dear Ali,

Yes, I agree.

Best regards,

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Wed Feb 21, 2018 7:15 am
by Cheng.Zhang
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

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Wed Feb 21, 2018 7:23 am
by Ali.Elyaakoubi
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

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Wed Feb 21, 2018 7:39 am
by Cheng.Zhang
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

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Wed Feb 21, 2018 8:50 am
by Jason.Jonkman
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,

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Wed Feb 21, 2018 9:06 am
by Cheng.Zhang
Dear Jason,
Yes, I agree.
It seems that FAST can not output those states. e.g.

Code: Select all

   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

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Wed Feb 21, 2018 9:39 am
by Jason.Jonkman
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,

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Sat Mar 10, 2018 5:39 am
by Ali.Elyaakoubi
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

Re: Simulation of an offshore Wind turbine 5MW based DFIG

Posted: Sat Mar 10, 2018 8:28 am
by Jason.Jonkman
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,