Blade pitch control

Hi, all.
Now, I am working on the blade pitch control of 5-MW baseline wind turbine.
I would like to use a simple model of the blade pitch actuator as
dot(B)=-1/tauB+1/tauBd
where B is the blade pitch angle; tau is the time constant; and Bd is the desired blade pitch angle as a command.

Could anyone tell me how to determine the value of tau for such a reference wind turbine?

Thanks in advance.

Best regards
Lei DUAN

Dear Lei DUAN,

Section 7.4 of the NREL 5-MW specifications report describes the characteristics of a very fast blade-pitch actuator: nrel.gov/docs/fy09osti/38060.pdf. I’ll let someone else respond if they know of more realistic values for a 5-MW turbine.

Best regards,

Dear Jason,
Thanks for your reply.
I also think the pitch actuator mentioned in Section 7.4 is too fast.

Anyway, thank you very much.

Best regards,
Lei DUAN

thank you for your prompt response. I get it now! :slight_smile:

Dear Jinsong,

As discussed in several papers (e.g.: nrel.gov/docs/fy08osti/42589.pdf), the control system may have a strong influence on the response of a FOWT and vice-versa. Have you adopted a controller (particularly the pitch-control gains) to work with your floating wind system?

Best regards,

Dear Jason,

I am currently trying to run the 5-MW NREL onshore using “FAST_v7.02.00d-bjj_AeroDyn_v13.00.02a-bjj_BladedDLLInterface.exe”. I want to run the same wind turbine in Bladed. Is DISCON.DLL is the same controller as the one used in the exe mentioned before?
I have to model the pitch actuator in Bladed. Have you found any realistic values for this turbine?

Regards,

Hi,

I think I can help on this. DISCON.DLL should be in the Bladed external controller format already so should be the same. I’m not sure there is defined a pitch actuator for this turbine. A reasonable choice though is probably just a first or second order lag.

Paul

Dear All,

I would like to learn what is the main objective of the blade-pitch process control? Could anyone describe in more detail (possibly using charts) what is happening when PI is used for eroded blades?

Thank you,

Raivis.Nikitins

Dear Raivis,

The main objective of a baseline blade-pitch control system is to regulate the rotor (or generator) speed. See section 7.3 of the NREL 5-MW specifications report for the development of a standard baseline pitch control system: nrel.gov/docs/fy09osti/38060.pdf.

More advanced pitch control systems may include additional actuation (e.g. independent blade pitch) and additional control objectives (e.g. reducing loads).

If the rotor-blades are eroding, the controller gains may not be as the designer expected and the controller would not perform optimally.

Best regards,

Thank you, Jason!

I will study the NREL 5-MW specifications report.

Best regards,

Raivis.Nikitins
Adaplab

Hi everyone
I’m working on individual pitch control and set PCMode to 4 to get the pitch command from the simulink controller but the pitch remains fixed to the final value of 2.6 and does not command the simulink. Where is the problem?
thanks

Dear Zarei,

Are you saying that you running FAST interfaced to Simulink, you’ve set PCMode=4, but the commands from Simulink are being ignored? Have you enabled the override pitch maneuvers (TPitManS(), PitManRat(), BlPitchF(*)), which override the commands from the controller?

Best regards,

No I did not enable these. I just set PCMODE to 4 and then run the simulation.

Dear Zarei,

And you are running the simulation from Simulink?

Best regards,

Yes, I’m running from Simulink.

Dear all,

I am trying to implement a simple pitch controller in FAST using MATLAB (Simulink). However, I observe discrepancy in the pitch angle between MATLAB and FAST.out. Kindly note that here i am not using two different controllers in FAST and MATLAB. I am simply setting PCMode to 4 in servodyn.dat file and using the controller as given in the figure “PitchController.Jpg” (attached) and performing the simulation . I could successfully track the generator speed at fixed value above the rated speed. When I plot pitch activity reported in the FAST output file,(pitch_FAST.jpg) it does not match with the same I plotted through scope variable “pitch angle” in simulink (pitch_MATLAB.jpg). I expect a difference of units i.e FAST output in deg and MATLAB in radians but i see a significant difference in both, can some one help me the reason for this difference. Thanks.

PS: I understand that this sort of pitch activity is meaning less, nevertheless, both FAST and simulink output should match. Right?

Regards,
Kumara



hi every one
How much should be used to the value of time constant of the 1.5 MW wind turbine pitch actuator for the FAST reference turbine?

Dear Zarei,

By “1.5-MW wind turbine…for the FAST reference turbine” are you referring to the WindPACT 1.5-MW baseline turbine? The documentation for this turbine (WindPACT Turbine Rotor Design Study: nrel.gov/docs/fy06osti/32495.pdf) refers to a second-order blade-pitch actuator (with a given natural frequency and damping ratio) rather than a time constant of a (presumably) first-order actuator that you are asking about.

Based on our separate e-mail communication, can I assume that you now have the FAST-Simulink interface working?

Best regards,

Dear Kumura,

The FAST-S-Function will use extrapolated values of the inputs (including blade-pitch angle) passed from Simulink (as discussed in other forum topics e.g. http://forums.nrel.gov/t/s-function-input-output-signal-mismatch/1502/2). Thus, the FAST S-Function may not report exactly the same values of the blade pitch angles that are input from Simulink. I would always ensure that (1) the initial pitch angle set within the ElastoDyn primary input file matches the pitch specified within the Simulink model at time zero and (2) the pitch angle changes are defined smoothly within Simulink.

Best regards,

thanks for your help.
i read it. There, it is said that ωn = 4Ω, where Ω is the rotor angular velocity and I’ve considered 20,463 rpm for the rotor speed and it is said ξ = 80% of critical damping. I want to know how much the critical damping value is?

Yes i am working FAST-Simulink interface now.

best regards.