Applying wind signal as input to the simulink

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Jason.Jonkman
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Re: Applying wind signal as input to the simulink

Postby Jason.Jonkman » Wed Oct 24, 2018 7:53 pm

Dear Sina,

In the NREL 5-MW baseline controller, the torque will be computed in Region 2.5 if the generator speed is between the lower (1136.498 rpm) and upper (1161.963 rpm) limits of Region 2.5 and if the blade-pitch angle is less than 1 degree.

I have not reviewed your Simulink implementation in detail, but Leonardo.Lopez uploaded his Simulink implementation of the baseline controller for the NREL 5-MW turbine in the Mar 03, 2017 post in the following forum topic: viewtopic.php?f=30&t=1777&p=8736.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Sina.Ameli
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Re: Applying wind signal as input to the simulink

Postby Sina.Ameli » Wed Oct 31, 2018 9:38 am

Dear Dr. Jonkman,

Thanks a lot for mentioning the forum. I implemented the baseline control and enter a fixed wind speed of 15 m/s and got these results:
Capture.PNG
Capture.PNG (36.44 KiB) Viewed 5178 times

The Fast document for 5 MW offshore windturbines (https://www.nrel.gov/docs/fy09osti/38060.pdf), mentions that if wind speed is 15 m/s, the pitch angle should be around 11 deg, while mine is around 17! I also think the generator speed and power should be much higher with this wind speed!
Moreover, when I enter a fixed wind speed of 20 m/s, at the beginning of the simulation I encounter such an error in Matlab:

An error occurred while running the simulation and the simulation was terminated
Caused by:
Error reported by S-function 'FAST_SFunc' in 'PI_Control10312018_Offshore/FAST Nonlinear Wind Turbine/S-Function':
FAST_Solution:FAST_AdvanceStates:AD_UpdateStates:SetInputs:TwrInfl:getLocalTowerProps:Tower strike.
TwrInfl:getLocalTowerProps:Tower strike.
TwrInfl:getLocalTowerProps:Tower strike.
AD_UpdateStates:SetInputs:TwrInfl:getLocalTowerProps:Tower strike.
TwrInfl:getLocalTowerProps:Tower strike.
TwrInfl:getLocalTowerProps:Tower strike.
FAST_Solution:CalcOutputs_And_SolveForInputs:SolveOption2:AD_CalcOutput:SetInputs:TwrInfl:getLocalTowerProps:Tower strike.
TwrInfl:getLocalTowerProps:Tower strike.
TwrInfl:getLocalTowerProps:Tower strike.
AD_CalcOutput:BEMT_CalcOutput(node 19, blade 2):Compute_UA_AirfoilCoefs:UA_CalcOutput:Mach number exceeds 1.0. Equations cannot be evaluated.

Thanks

Best Regards,
Sina

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Re: Applying wind signal as input to the simulink

Postby Jason.Jonkman » Wed Oct 31, 2018 3:58 pm

Dear Sina,

If you are not getting the correct rotor speed and blade-pitch angle (as well generator power etc.) response to steady wind, then I would guess that there is a problem with your controller implementation.

My guess is your tower-strike error is caused by the use of improper initial conditions. To reduce start-up transients (and errors such as tower strike), normally we recommend that at a minimum, the initial conditions of rotor speed and blade-pitch angle be set to their steady-state values for the given wind speed being simulated.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Sina.Ameli
Posts: 75
Joined: Mon Oct 15, 2018 11:23 am
Organization: FSU
Location: Florida

Re: Applying wind signal as input to the simulink

Postby Sina.Ameli » Fri Nov 02, 2018 8:22 am

Dear Dr. Jonkman,

Thanks for the reply. Actually, I checked the controller several times, it is completely matched with the simulink figures located on that forum you stated!

Regarding the error, the problem is that even when I run test 24 (only the open loop), the matlab gives me this error:

Error using Run_OpenLoop (line 30)
Error reported by S-function 'FAST_SFunc' in 'OpenLoop/FAST Nonlinear Wind Turbine/S-Function':
FAST_Solution:FAST_AdvanceStates:AD_UpdateStates:SetInputs:TwrInfl:getLocalTowerProps:Tower strike.
TwrInfl:getLocalTowerProps:Tower strike.
TwrInfl:getLocalTowerProps:Tower strike.
AD_UpdateStates:SetInputs:TwrInfl:getLocalTowerProps:Tower strike.
FAST_Solution:CalcOutputs_And_SolveForInputs:SolveOption2:AD_CalcOutput:SetInputs:TwrInfl:getLocalTowerProps:Tower strike.
TwrInfl:getLocalTowerProps:Tower strike.
TwrInfl:getLocalTowerProps:Tower strike.
AD_CalcOutput:BEMT_CalcOutput(node 19, blade 3):Compute_UA_AirfoilCoefs:UA_CalcOutput:Mach number exceeds 1.0. Equations cannot be
evaluated.

That is the same as the error I mentioned previously. Previously I didn't get such an error and could run the test completely!

Thanks

Best Regards,
Sina

Jason.Jonkman
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Re: Applying wind signal as input to the simulink

Postby Jason.Jonkman » Fri Nov 02, 2018 8:48 am

Dear Sina,

What modifications did you make to Test24 to run it OpenLoop? If you are disabled all control, I could imagine you'd get a tower-strike error because the blades won't pitch to shed load when the turbulent wind speed increases.

I don't really understand enough about what you are doing to offer more advice.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Sina.Ameli
Posts: 75
Joined: Mon Oct 15, 2018 11:23 am
Organization: FSU
Location: Florida

Re: Applying wind signal as input to the simulink

Postby Sina.Ameli » Mon Nov 05, 2018 3:52 pm

Dear Dr. Jonkman,

Thanks for your reply and help. My problem was solved by getting the implemented file from the forum you introduced. I want to design a pitch controller but I don't have dynamic equations of the offshore 5 MW wind turbine. I need an equation relating generator speeds (for example its second order derivative equation) to three variables pitch angle, generator and wind speed. What I mean is the equation with perturbed values of these variables. Where can I find them?

Thanks
Best Regards,
Sina

Jason.Jonkman
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Re: Applying wind signal as input to the simulink

Postby Jason.Jonkman » Mon Nov 05, 2018 10:31 pm

Dear Sina,

If I understand your question correctly, you want the linearized (perturbed) equations of motion of the drivetrain dependent on perturbations of the rotor-collective blade-pitch angle, generator torque, and wind speed. Such a linear form of the equations of motion can be derived from FAST using FAST's full-system linearization functionality.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Sina.Ameli
Posts: 75
Joined: Mon Oct 15, 2018 11:23 am
Organization: FSU
Location: Florida

Re: Applying wind signal as input to the simulink

Postby Sina.Ameli » Tue Nov 06, 2018 8:14 am

Dear Dr. Jonkman,

Thanks for your reply.To illustrate, I want to design a nonlinear controller for the 5 MW offshore wind turbine. I need such an equation:
Capture.PNG
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but the problem is Cp that does not give me a specific equation. It seems one way is linearizing the model in this way:
Capture2.PNG
Capture2.PNG (3.04 KiB) Viewed 5112 times

Capture3.PNG
Capture3.PNG (5.44 KiB) Viewed 5112 times

My question is that since I want to design a nonlinear controller, is there any specific nonlinear equation of this model? If not, how can I linearize the model using Fast 8? Should I use a software or Matlab does it for me?

Thanks

Best Regards,
Sina

Jason.Jonkman
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Joined: Thu Nov 03, 2005 4:38 pm
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Re: Applying wind signal as input to the simulink

Postby Jason.Jonkman » Fri Nov 09, 2018 6:45 am

Dear Sina,

FAST itself is a nonlinear model, so, there certainly are specific nonlinear equations. But the equations are extensive (and can't be shown in a forum post), their solutions are numerical (not analytical), and their linearization is done numerically in some areas of the model due to the complexity of the equations.

The linearization functionality of FAST v8 is built into FAST. Linear models can be generated while running FAST in Simulink or with the standalone executable. See the "Linearization" and "Linearization Files" sections of the FAST v8 ReadMe file for more information: https://wind.nrel.gov/nwtc/docs/README_FAST8.pdf.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Sina.Ameli
Posts: 75
Joined: Mon Oct 15, 2018 11:23 am
Organization: FSU
Location: Florida

Re: Applying wind signal as input to the simulink

Postby Sina.Ameli » Wed Nov 14, 2018 7:35 pm

Dear Dr. Jonkman,

Thanks a lot for your help that I need in these days to progress my research. Actually, in your document for 5 MW offshore WT, you have already given the perturbation equations and parameters (the linearized drive-train equation)! Now, I have three questions. First, what is the value of the drive-train inertia (I_Drivetrain) mentioned in (https://www.nrel.gov/docs/fy09osti/38060.pdf)?
Capture.PNG
Capture.PNG (5.67 KiB) Viewed 4801 times

Second, as the FAST in Simulink/Matlab does not have any actuator dynamic, I need to add a dynamic for the pitch actuator. What is the response time constant of pitch angle (actuator)? In the mentioned file for 5MW offshore, it mentions (Equivalent Blade-Pitch-Actuator Linear-Spring Constant=971,350,000N•m/rad and Equivalent Blade-Pitch-Actuator Linear-Damping Constant=206,000N•m/rad/s). I need an a dynamic equation of the pitch actuator like this:
pact.PNG
pact.PNG (3.52 KiB) Viewed 4801 times

Last but not least, how and where can I create a fault in pitch actuator in FAST/Simulink?

Thanks

Best Regards,
Sina

Jason.Jonkman
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Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
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Re: Applying wind signal as input to the simulink

Postby Jason.Jonkman » Wed Nov 14, 2018 8:27 pm

Dear Sina,

The total drivetrain (rotor + generator) inertia of the NREL 5-MW baseline wind turbine is documented in the following forum topic: viewtopic.php?f=4&t=731&p=5622.

The equivalent blade-pitch-actuator spring and damping constants stated result in a second-order transfer function (with a natural frequency and damping ratio) rather than the first-order form you are showing. Thus, there is no true equivalency. That said, the frequency of the second-order actuator is very high--as if the actuator does not exist. This would be equivalent to a very low value of tau_theta in your first-order transfer function.

Pitch faults are set by the override pitch maneuvers defined within the ServoDyn module.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Sina.Ameli
Posts: 75
Joined: Mon Oct 15, 2018 11:23 am
Organization: FSU
Location: Florida

Re: Applying wind signal as input to the simulink

Postby Sina.Ameli » Thu Nov 15, 2018 7:24 am

Dear Dr. Jonkman,

Thank you so much for your prompt response and for clarifying the issue.

Best Regards,
Sina


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