# Help for generator of NREL 5MW Turbine

Hello,
I’d like to build the mathematical model of NREL 5.0 MW Baseline Wind Turbine for Use in Offshore, but I don’t know the generator type of NREL 5MW Turbine. Is it doubly-fed induction generator or other type generator? And I’d like to know the time constant of the generator and the slope coefficient of the Torque-Speed curve. Where could I find these?
Sincerely,
Xuejian Bai

Dear Xuejian Bai,

The NREL 5-MW baseline turbine is a conceptual design only, and the details of the electrical drive, including generator details (other than the active torque controller), have never been specified for this turbine. If you need to apply a torque-speed relationship etc. different from those of the active torque control, you’ll have to make some assumptions and specify them yourself.

Best regards,

Hi Jason,

The generator information for the AWT 750KW is mentioned in different references and FAST documents as:
SIG_SlPc = 1.5125; % - Rated generator slip percentage [>0] (%) Now HSS side!
SIG_SySp = 1200.0; % - Synchronous (zero-torque) generator speed [>0] (rpm) Now HSS side!
SIG_RtTq = 1367.9; % - Rated torque [>0] (N-m) Now HSS side!
SIG_PORt = 2.0; % - Pull-out ratio (Tpullout/Trated) [>1] (-)%
SIG_SySp = SIG_SySppi/30; % convert to rad/s
SIG_RtSp = SIG_SySp
(1.0+0.01SIG_SlPc);
SIG_POS1=SIG_PORt
(SIG_RtSp-SIG_SySp);
SIG_POTq=SIG_RtTq*SIG_PORt;
SIG_Slop=SIG_RtTq/(SIG_RtSp - SIG_SySp);

Are these details applicable only for the 750KW wind turbine? Can we apply the same numbers for 5MW wind turbine? If not, is there a way to determine these values or any references that have already determined them?
Your guidance is so much appreciated.

Dear Vahid,

The Simple Induction Generator (SIG) model available within ServoDyn is documented in the old FAST v7 User’s Guide: drive.google.com/file/d/1d_-vRR … d91gg/view. The properties will need to be changed between turbines, e.g., SIG_RtTq*SIG_RtSp should equal the rated power.

Best regards,

Dear Jason,

Isn’t there a Thevenin-Equivalent induction generator model for the 5MW NREL wind turbine? In order to represent well the Torque-VS-GeneratorSpeed of it.
Otherwise, what is the model used in OpenFAST to compute this characteristic with the parameters given as input of the Thevenin-Equivalent induction generator?

Kindest regards

Dear @Younes.Oudich,

The Thevenin-Equivalent induction generator (TEC) model implemented in ServoDyn is valid for fixed speed generators. To accommodate variable speed operation, I’m not aware that a TEC model has been developed for the NREL 5-MW baseline wind turbine. Instead, in the baseline controller for the NREL 5-MW turbine, the torque is computed as a function of speed using a segmented torque-speed curve (covering control regions 1, 1.5, 2, 2.5, and 3). See the specification document for the NREL 5-MW baseline wind turbine for more information: https://www.nrel.gov/docs/fy09osti/38060.pdf.

Best regards,

Dear Jason,

Thank you so much for the reply!
I would like to use only the pitch controller for derating and let the torque acts on its own depending on the generator speed (Torque -VS- Generator speed). That is why the torque controller for power maximization is not convenient for me. Looking at the FAST tutorial, it seems possible to have the following curve by adjusting the TEC parameters inside ServoDyn. But my question is: How this curve is generated using these ServoDyn parameters? What is the model considered in this case?
I am aiming at adjusting these parameters to have a Torque -VS- Generator speed curve for the 5MW NREL HAWT

Kindest regards

Dear @Younes.Oudich,

Good question. It has been many years since I looked at the equations for the Thevein Equivalent Circuit (TEC) induction generator model. And I can’t seem to find the notes I had when this model was implemented. That said, you can find the equations used implemented within the ServoDyn source code. See how the TEC parameters are set on lines 2949-2969 and see how the torque and power are computed based on these parameters on lines 3944-3966 of ServoDyn.f90 here: openfast/ServoDyn.f90 at main · OpenFAST/openfast · GitHub.

Best regards,

Dear @Jason.Jonkman

That’s exactly what I was looking for. Thank you for the information and the reference. It helps a lot!
I will look at that model.

Kindest regards