Applying wind signal as input to the simulink

Dear Sina,

TMax is defined in the FAST primary input (*.fst) file.

Best regards,

Dear Dr. Jonkman,

Thanks for replying with celerity. All *.fst files are related to all tests. Which test I should change TMax in it? In other words, how do I know the simulink runs which test number? Should I define the number of the test for Matlab?

Thanks

Best Regards,
Sina

Dear Sina,

When running FAST v8 interfaced to Simulink, the TMax specified in MATLAB will be used in place of the TMax set in the primary FAST input file. Which of the 26 different FAST models in the CertTest directory do you want to run? E.g. Test18 is a model of the land-based NREL 5-MW turbine. If you are running Run_OpenLoop.m, you can choose which of these models to run e.g. set iTest = 18. In this case, TMax is set within the Run_OpenLoop.m script.

Best regards,

Dear Dr. Jonkman,

Thanks again for your prompt response. I am doing research on fault tolerant control of Pitch and Torque control of wind turbines. Could you tell me which model (test) is a 5 MW offshore variable speed wind turbine that is appropriate for my research?

Thanks

Best Regards,
Sina

Dear Sina,

When you say “offshore”, what type of support structure do you have in mind? Test18 is a model of an offshore 5-MW wind turbine, but installed on land. Tests 19-25 are for the same turbine installed atop various offshore support-structure configurations, including monopile, tripod, jacket, and various floating configurations.

Best regards,

Dear Dr. Jonkman,

Thanks for your reply. I want to work on a three-blade offshore wind turbine model that has a realistic nonlinear model to work on pitch and torque control and accepts wind turbulences, and I can apply realistic fault scenarios such as faults in actuators, generator and converters. Which model meets these features the most?

Thanks

Best Regards,
Sina

Dear Sina,

I gather that you do not need a specific support structure. Thus, I’d recommend that you use the NREL 5-MW turbine installed on land (Test18.fst), which meets the needs you’ve laid out.

Bets regards,

Dear Dr. Jonkman,
Thanks for clarifying the issue. I have encountered a problem. I implemented the pitch and torque controller mentioned in the document (using nrel.gov/docs/fy08osti/42437.pdf ) for 5MW offshore wind turbine but I encountered a problem by weird simulation results. For instance, based on table (please see the bellow picture) located in 38060, I considered a pitch angle of zero and entered a the wind input of 11.4 m/s in the 40th seconds of the simulation.

As mentioned in the document, the translational generator speed for region 2.5 to 3 is 1161.93 rpm and the rated generator speed is 1173.7 rpm. Does the generator speed begins the region 2.5 by the speed of 1161.93 rpm?
I implemented the torque and pitch control like this (for the torque controller I changed the values of document 42437 to be compatible for a 5MW WT and for the pitch controller I exactly used the PI gains mentioned in 38060):

Here are my results:


The problem is that based on the controllers, the wind turbine was supposed to work in region 3, but the generator speed is decreasing to a very low value (from region 2 to region 1!) and the generator power is in the maximum level (5MW)! And the most uncanny part of that is when the generator power goes to 10MW between 0.012 to 0.025 sec and afterwards, it goes to 5MW. In region 2, it was supposed to have a pitch of zero to capture the maximum power, while based on the figure above, the blade pitch is decreasing more and more!
Thanks

Best Regards,
Sina

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: http://forums.nrel.gov/t/baseline-nrel-5mw-controller-on-simulink/1557/13.

Best regards,

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:


The Fast document for 5 MW offshore windturbines (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

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,

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

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,

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

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,

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

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
Capture3.PNG
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

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: wind.nrel.gov/nwtc/docs/README_FAST8.pdf.

Best regards,

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 (nrel.gov/docs/fy09osti/38060.pdf)?
Capture.PNG
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
Last but not least, how and where can I create a fault in pitch actuator in FAST/Simulink?

Thanks

Best Regards,
Sina

Dear Sina,

The total drivetrain (rotor + generator) inertia of the NREL 5-MW baseline wind turbine is documented in the following forum topic: http://forums.nrel.gov/t/whats-the-exact-meaning-of-hubiner/595/8.

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,

Dear Dr. Jonkman,

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

Best Regards,
Sina