Learizing Baseline 5MW Wind Turbine with FAST

I just need a clarification regarding the linearization of the FAST.I got a Linearized model of the wind turbine using FAST7.2 . But i need to use the FAST8.10 for using LIDAR data. can we use the linearized model of the FAST7 with FAST8.10 for designing a controller? Is that the parameters are same in both versions?

Dear Srinivasa,

FAST v8 has many of the same features of FAST v7, as well as many new features not available in FAST v7. I suppose the answer to your question depends on how many of the new features of FAST v8 you’ve enabled. Certainly, if you obtain similar time-domain responses between FAST v7 and FAST v8 for your model, I would expect the linearized FAST v7 model to be applicable to cases using FAST v8.

Best regards,

Hello
In order to realize a linearization of 5MW NREL i have a problem related to the wind profile
I choose the step wind profile of 12, so i included it name in both ijn the input file and the aerodyn.ipt file, of course i specified the linear file and the modification nedded in the input
Bref when i launced the simulation, an error occur, where it is attached here
I would appreciate any guidance you can give me on how to overcome this error/problem.

The error you are encountering doesn’t seem to be related to linearizing the model. The error “NBlInpSt must be at least 1.” is a check on the input values from the FAST v7 individual blade input file (specified as BldFile(1-3) in the .fst file). The parameter NBlInpSt should be specified on the 5th line in that file, so you should check to see what is wrong in that blade file.

See if it is correctely that file

[code]------- ELASTODYN V1.00.* INDIVIDUAL BLADE INPUT FILE --------------------------
NREL 5.0 MW offshore baseline blade input properties.
---------------------- BLADE PARAMETERS ----------------------------------------
49 NBlInpSt - Number of blade input stations (-)
0.477465 BldFlDmp(1) - Blade flap mode #1 structural damping in percent of critical (%)
0.477465 BldFlDmp(2) - Blade flap mode #2 structural damping in percent of critical (%)
0.477465 BldEdDmp(1) - Blade edge mode #1 structural damping in percent of critical (%)
---------------------- BLADE ADJUSTMENT FACTORS --------------------------------
1 FlStTunr(1) - Blade flapwise modal stiffness tuner, 1st mode (-)
1 FlStTunr(2) - Blade flapwise modal stiffness tuner, 2nd mode (-)
1.04536 AdjBlMs - Factor to adjust blade mass density (-) !bjj: value for AD14=1.04536; value for AD15=1.057344 (it would be nice to enter the requested blade mass instead of a factor here)
1 AdjFlSt - Factor to adjust blade flap stiffness (-)
1 AdjEdSt - Factor to adjust blade edge stiffness (-)
---------------------- DISTRIBUTED BLADE PROPERTIES ----------------------------
BlFract PitchAxis StrcTwst BMassDen FlpStff EdgStff
(-) (-) (deg) (kg/m) (Nm^2) (Nm^2)
0.0000000E+00 2.5000000E-01 1.3308000E+01 6.7893500E+02 1.8110000E+10 1.8113600E+10
3.2500000E-03 2.5000000E-01 1.3308000E+01 6.7893500E+02 1.8110000E+10 1.8113600E+10
1.9510000E-02 2.5049000E-01 1.3308000E+01 7.7336300E+02 1.9424900E+10 1.9558600E+10
3.5770000E-02 2.5490000E-01 1.3308000E+01 7.4055000E+02 1.7455900E+10 1.9497800E+10
5.2030000E-02 2.6716000E-01 1.3308000E+01 7.4004200E+02 1.5287400E+10 1.9788800E+10
6.8290000E-02 2.7941000E-01 1.3308000E+01 5.9249600E+02 1.0782400E+10 1.4858500E+10
8.4550000E-02 2.9167000E-01 1.3308000E+01 4.5027500E+02 7.2297200E+09 1.0220600E+10
1.0081000E-01 3.0392000E-01 1.3308000E+01 4.2405400E+02 6.3095400E+09 9.1447000E+09
1.1707000E-01 3.1618000E-01 1.3308000E+01 4.0063800E+02 5.5283600E+09 8.0631600E+09
1.3335000E-01 3.2844000E-01 1.3308000E+01 3.8206200E+02 4.9800600E+09 6.8844400E+09
1.4959000E-01 3.4069000E-01 1.3308000E+01 3.9965500E+02 4.9368400E+09 7.0091800E+09
1.6585000E-01 3.5294000E-01 1.3308000E+01 4.2632100E+02 4.6916600E+09 7.1676800E+09
1.8211000E-01 3.6519000E-01 1.3181000E+01 4.1682000E+02 3.9494600E+09 7.2716600E+09
1.9837000E-01 3.7500000E-01 1.2848000E+01 4.0618600E+02 3.3865200E+09 7.0817000E+09
2.1465000E-01 3.7500000E-01 1.2192000E+01 3.8142000E+02 2.9337400E+09 6.2445300E+09
2.3089000E-01 3.7500000E-01 1.1561000E+01 3.5282200E+02 2.5689600E+09 5.0489600E+09
2.4715000E-01 3.7500000E-01 1.1072000E+01 3.4947700E+02 2.3886500E+09 4.9484900E+09
2.6341000E-01 3.7500000E-01 1.0792000E+01 3.4653800E+02 2.2719900E+09 4.8080200E+09
2.9595000E-01 3.7500000E-01 1.0232000E+01 3.3933300E+02 2.0500500E+09 4.5014000E+09
3.2846000E-01 3.7500000E-01 9.6720000E+00 3.3000400E+02 1.8282500E+09 4.2440700E+09
3.6098000E-01 3.7500000E-01 9.1100000E+00 3.2199000E+02 1.5887100E+09 3.9952800E+09
3.9350000E-01 3.7500000E-01 8.5340000E+00 3.1382000E+02 1.3619300E+09 3.7507600E+09
4.2602000E-01 3.7500000E-01 7.9320000E+00 2.9473400E+02 1.1023800E+09 3.4471400E+09
4.5855000E-01 3.7500000E-01 7.3210000E+00 2.8712000E+02 8.7580000E+08 3.1390700E+09
4.9106000E-01 3.7500000E-01 6.7110000E+00 2.6334300E+02 6.8130000E+08 2.7342400E+09
5.2358000E-01 3.7500000E-01 6.1220000E+00 2.5320700E+02 5.3472000E+08 2.5548700E+09
5.5610000E-01 3.7500000E-01 5.5460000E+00 2.4166600E+02 4.0890000E+08 2.3340300E+09
5.8862000E-01 3.7500000E-01 4.9710000E+00 2.2063800E+02 3.1454000E+08 1.8287300E+09
6.2115000E-01 3.7500000E-01 4.4010000E+00 2.0029300E+02 2.3863000E+08 1.5841000E+09
6.5366000E-01 3.7500000E-01 3.8340000E+00 1.7940400E+02 1.7588000E+08 1.3233600E+09
6.8618000E-01 3.7500000E-01 3.3320000E+00 1.6509400E+02 1.2601000E+08 1.1836800E+09
7.1870000E-01 3.7500000E-01 2.8900000E+00 1.5441100E+02 1.0726000E+08 1.0201600E+09
7.5122000E-01 3.7500000E-01 2.5030000E+00 1.3893500E+02 9.0880000E+07 7.9781000E+08
7.8376000E-01 3.7500000E-01 2.1160000E+00 1.2955500E+02 7.6310000E+07 7.0961000E+08
8.1626000E-01 3.7500000E-01 1.7300000E+00 1.0726400E+02 6.1050000E+07 5.1819000E+08
8.4878000E-01 3.7500000E-01 1.3420000E+00 9.8776000E+01 4.9480000E+07 4.5487000E+08
8.8130000E-01 3.7500000E-01 9.5400000E-01 9.0248000E+01 3.9360000E+07 3.9512000E+08
8.9756000E-01 3.7500000E-01 7.6000000E-01 8.3001000E+01 3.4670000E+07 3.5372000E+08
9.1382000E-01 3.7500000E-01 5.7400000E-01 7.2906000E+01 3.0410000E+07 3.0473000E+08
9.3008000E-01 3.7500000E-01 4.0400000E-01 6.8772000E+01 2.6520000E+07 2.8142000E+08
9.3821000E-01 3.7500000E-01 3.1900000E-01 6.6264000E+01 2.3840000E+07 2.6171000E+08
9.4636000E-01 3.7500000E-01 2.5300000E-01 5.9340000E+01 1.9630000E+07 1.5881000E+08
9.5447000E-01 3.7500000E-01 2.1600000E-01 5.5914000E+01 1.6000000E+07 1.3788000E+08
9.6260000E-01 3.7500000E-01 1.7800000E-01 5.2484000E+01 1.2830000E+07 1.1879000E+08
9.7073000E-01 3.7500000E-01 1.4000000E-01 4.9114000E+01 1.0080000E+07 1.0163000E+08
9.7886000E-01 3.7500000E-01 1.0100000E-01 4.5818000E+01 7.5500000E+06 8.5070000E+07
9.8699000E-01 3.7500000E-01 6.2000000E-02 4.1669000E+01 4.6000000E+06 6.4260000E+07
9.9512000E-01 3.7500000E-01 2.3000000E-02 1.1453000E+01 2.5000000E+05 6.6100000E+06
1.0000000E+00 3.7500000E-01 0.0000000E+00 1.0319000E+01 1.7000000E+05 5.0100000E+06
---------------------- BLADE MODE SHAPES ---------------------------------------
0.0622 BldFl1Sh(2) - Flap mode 1, coeff of x^2
1.7254 BldFl1Sh(3) - , coeff of x^3
-3.2452 BldFl1Sh(4) - , coeff of x^4
4.7131 BldFl1Sh(5) - , coeff of x^5
-2.2555 BldFl1Sh(6) - , coeff of x^6
-0.5809 BldFl2Sh(2) - Flap mode 2, coeff of x^2
1.2067 BldFl2Sh(3) - , coeff of x^3
-15.5349 BldFl2Sh(4) - , coeff of x^4
29.7347 BldFl2Sh(5) - , coeff of x^5
-13.8255 BldFl2Sh(6) - , coeff of x^6
0.3627 BldEdgSh(2) - Edge mode 1, coeff of x^2
2.5337 BldEdgSh(3) - , coeff of x^3
-3.5772 BldEdgSh(4) - , coeff of x^4
2.376 BldEdgSh(5) - , coeff of x^5
-0.6952 BldEdgSh(6) - , coeff of x^6

[/code]

The blade file you posted is for ElastoDyn, which is compatible with FAST v8. You are linearizing with FAST v7, so you need the FAST v7 version of that blade file. It is very similar, except it has different number of header lines and the PitchAxis column is replaced with AeroCent.

Thank you verry much for your help Mr Bonnie
Now I would like to peform a linearization of the system WT around differents operating points ( the operating point is fixed by the wind speed) so at each fois i use a step of wind speed.
Firstely i did the modification in the input file(anallmode=2,PCMode=0,VsControl=0, I turn on GenDOF and DrTDOF and in the list of output i listed GenSpeed, i didTrimcase=2 (so i should use a wind below the rated value i.e the system work in the partial load),Ninput=1,CntrlInput=3,NDisturb=1 and Distrub=1)
The linearization work fine, it gives some things
I will apreciate if you can calrify me this points
If my reason of linearization is true
Why
-AvgAMat=a matrix(4,4) normaly there is three DOF in this simulation(GenSpeed,RotSpeed and the torque of torsion)

-VsControl=0 (when i did Vscontrol=1 an error occur, and when Trimecase=3 PCMode=0or 1?)

I would appreciate your guidance

Dear Ali,

The generator azimuth state is often removed from a linearized model through post-processing to convert the 4x4 system to a 3x3 system, as discussed in the following forum topic: http://forums.nrel.gov/t/fast-linearized-models/249/1 (starting Sep 16, 2014).

You must set VSContrl = 0 when using TrimCase = 2 because the trim solution in this case will calculate the generator torque necessary to maintain the specified rotor speed. Likewise, you must set PCMode = 0 when using TrimCase = 3 because the trim solution in this case will calculate the blade-pitch angle necessary to maintain the specified rotor speed.

Best regards,

Hello everbody
I hope you are very well

Ta=a*Omega_r+b*wind_speed

I would like to run a linearization with in order to determine the coefficient of the equation above (Ta is the aerodynamic torque or the low shaft speed torque, depend normally to (wind speed,beta,rotational speed) and i work in the wind speed above the the rated value, so the torque is expressed by the above equation)
When I want to perform the linearization (firstlly i did the modification in the input file, i work with a lumed mass so i activated GenDOF, I trimed on the generator torque and i fixed VScontrol to zero(really i dont know if it is possible to do linearization without trime case, because i would like to determine the aerodynamic charcteristic of the wind turbine it may be independent of the trime case process, if you can please explain me at this point), and i worked with a one step of wind speed (12 m/s)
Brifely when i run the simulation an error is occured FAST cannot linearize a model with no DOF with somes notes ( GenDof was chenged from false to true since Rot speed=0 meaning the generator is locked in place)
If you can please tell me what is the raison of this mistakes and also if my idea to determine the the coefficient (a and b) is correct , elsewhere if you any suggestion in this regards
I would appreciate any guidance from you to give me on how to resolve this problem.

Dear Ali,

I’m not really sure I understand everything you are saying/asking, but here are a few comments:

  • Normally above rated, one would trim blade-pitch angle (TrimCase = 3) instead of generator torque (TrimCase = 2) because above rated pitch varies, but torque is constant (and known from the rotor speed and rated power).
  • You can perform a FAST linearization without trim by disabling CalcSteady (i.e. linearizing about the initial conditions) or by disabling GenDOF (i.e. fixed generator speed).
  • I think you are referring to the following error message: “NOTE: GenDOF changed from True to False since RotSpeed = 0 meaning the generator is locked in place.” This error message is generated because in the old linearization of FAST v7 and earlier, one had to disable GenDOF during linearization if the rotor speed was set to zero. It was also not possible to linearize a model with no states.
  • It appears that you simply want to find coefficients of a simple expression for the aerodynamic torque. You shouldn’t need to use the linearization functionality of FAST to do this. Instead, you can find the coefficients that provide the best fit from a curve of aerodynamic torque as a function of rotor speed and wind speed. For a given rotor, you can use a tool like the standalone driver for AeroDyn v15 (nwtc.nrel.gov/AeroDyn) (independent of FAST) to compute the aerodynamic torque as a function of rotor speed and wind speed.

I hope that helps.

Best regards,

Thank you very much for your reply Mr Janson.It is exactly what i want to calculate the the aerodynamic torque as a function of the wind speed and the retational speed.
Enable me to ask you how to extract these coefficient.I have read the document that you have provide me and i have did the simulation with the standlone driver aerodyn, I obtained the output file. But not enough details apperas in the documentation about how to extract the coefficient from the output file and also to configure the simulation with what i want.
If you can please tell me how to obtain the coefficient for the 5MW WT.

Sinceerly

Dear Ali,

The standalone AeroDyn driver input file can be set up to run multiple cases for different wind speeds (WndSpeed), rotor speeds (RotSpd), and pitch angles (Pitch) via the “Combined-Case Analysis” options. You can include the rotor aerodynamic torque in the AeroDyn output file by including “RtAeroMxh” in the output list (OutList) in the AeroDyn primary input file. Simply run multiple cases and take the time- (or, preferably, azimuth-) averaged torque to find the RtAeroMxh as a function of WndSpeed, RotSpd, and Pitch (or the like).

Best regards,

thank you very much for your very helpful response
But it still me some ambiguities
For example i have run the simulation and the results are follew[code]
Predictions were generated on 10-Mar-2016 at 19:23:52 using AeroDyn_driver (v1.00.00-bjj, 7-Oct-2015)
AeroDyn (v15.00.00b-bjj, 6-Oct-2015)

Case 1: WndSpeed=5 m/s; ShearExp=0 ; RotSpeed=71.9 rpm; Pitch=0 deg; Yaw=0 deg; dT=3.97000E-02 s; Tmax=0.8345 s

 Time           	RtAeroMxh 
  (s)           	(N·m)     
     0.0000	-9.401E+01
     0.0397	 3.617E+02
     0.0794	 3.617E+02
     0.1191	 3.617E+02
     0.1588	 3.617E+02
     0.1985	 3.617E+02
     0.2382	 3.617E+02
     0.2779	 3.617E+02
     0.3176	 3.617E+02
     0.3573	 3.617E+02
     0.3970	 3.617E+02
     0.4367	 3.617E+02
     0.4764	 3.617E+02
     0.5161	 3.617E+02
     0.5558	 3.617E+02
     0.5955	 3.617E+02
     0.6352	 3.617E+02
     0.6749	 3.617E+02
     0.7146	 3.617E+02
     0.7543	 3.617E+02
     0.7940	 3.617E+02
     0.8337	 3.617E+02

[/code]
the average value =sum(value)/sum(number of time step)
So what represent the obtained value in relation to a and b
thank you to calrifiy plus

Dear Ali,

This is a single simulation showing that the aerodynamic rotor torque (RtAeroMxh) at 5 m/s and 71.9 rpm is 3.617E+02 N·m. You’ll have to run additional simulations at different wind speeds and rotor speeds in order to form a surface from which to derive “a” and “b”.

Best regards,

Ok so if i would like to works on the 5MW i should parameters firstely the file.dvr( Numblades=3,HubRad=1.5,HubHt=90;for Overhang,ShftTilt,Precone i change their values or not?); and I use the aerodynamique file with Airfoils and the balde file given in the archive as it is or i must change somthings?
After i did the simulation for differents values of wind speed and the rotational (of course these should be raisonable, i.e it must located in the partial load operation of the wind speed (wind<11,4 and rotational speed<12,1elsewhere we must consider the blade pitch value). Therefore as we increase the number of simulations as the result are accurate i think and finally, "a "represents the slope of the torque according the wind speed axis and “b” is the slope according to the rotational axis
Tell me please if these points is raisonable or there is somthings wrong

Sinceerly

Dear Ali,

Yes, that sounds reasonable. The Overhang, ShftTilt, and PreCone of the NREL 5-MW turbine are -5.0191 m, -5 deg, and -2.5 deg, respectively.

Best regards,

Thank you very much Mr Janson for your clear response
It still me a thing from your previous speech “run multiple cases and take the time- (or, preferably, azimuth-) averaged torque”, what you means by multiples cases ? and how i can average the torque on the azimuth rather than time?

Dear Ali,

Without skewed flow (without shaft tilt or nacelle-yaw error), the aerodynamic torque will be constant, as your results have shown in your post dated Mar 10, 2016 above. In this case, there is no need to time- or azimuth-average the results. If you introduce skewed flow, the aerodynamic torque will be periodic with a period of a rotor revolution. I was suggesting that you calculate the average torque over a revolution (known as azimuth-averaging).

By “multiple cases”, I meant that you should run additional simulations at different wind speeds and rotor speeds.

Best regards,

Thank you very much Mr Janson for your clear response, really it help me well to resolve the problem
However it still some informations to know:
the equivalent inertia of the wind turbine of 5MW (if we consider it as a lumped mass)=Hub inertia+Nacelle inertia or what

Dear Ali,

I’m sorry, but I don’t understand your question.

Best regards,