Linearization issue using Fast V7.02

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Jason.Jonkman
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Re: Linearization issue using Fast V7.02

Postby Jason.Jonkman » Fri Apr 17, 2020 4:03 pm

Dear Babak,

For equivalent settings, I would expect quite similar results between FAST v7 and FAST v8. In your case, the power is quite a bit off, so, I would expect that you have some settings set inconsistently.

Is there a reason you are using both FAST v7 and FAST v8? I would suggest upgrading and using the same version for the full analysis (to minimize the possibility of using different settings between analyses). Better yet, upgrade to OpenFAST.

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

Babak.Gavgani
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Re: Linearization issue using Fast V7.02

Postby Babak.Gavgani » Fri Apr 17, 2020 4:23 pm

Dear Jason,

Thanks for your helps.
The reason is that I do not know how to linearize around specific rotor speed in FAST8 and in FAST8 it is not possible to specify the control input.
One more question is:
I only need to use GetMats to obtain the averaged model (Linearized plant). In my case, only GenDOF is activated and the control input is generator torque So MBC is not needed because I do not have state(s) in rotating frame, right?
I appreciate for your helps and information.

Kind regards,
Babak

Jason.Jonkman
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Re: Linearization issue using Fast V7.02

Postby Jason.Jonkman » Fri Apr 17, 2020 4:29 pm

Dear Babak,

Good point. The control trim functionality from FAST v7 was not available in FAST v8, making the operating-point determination process a bit more difficult (but not impossible). NREL has worked with Envision Energy to reintroduce trim functionality into OpenFAST. I'm not sure why this capability has not yet been merged into OpenFAST-dev, but it is available in an OpenFAST pull request (waiting to be reviewed before being merged)--see: https://github.com/OpenFAST/openfast/pull/373.

Yes, I agree, no need to apply MBC in your case because your linearized model does not have states, inputs, or outputs, in the rotating frame.

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

Babak.Gavgani
Posts: 29
Joined: Sat Mar 14, 2020 12:03 pm
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Re: Linearization issue using Fast V7.02

Postby Babak.Gavgani » Sat Apr 18, 2020 6:31 am

Dear Jason,

With regards to our previous discussion, I want to obtain (Power-Rotor Speed) curves (in region 2) for different constant wind speeds in FAST7 and then compare it with the linearized model in FAST7.
10kW wind turbine is selected (Test17.fst). Only GenDOF is activated and the ''RotSpeed'' and '''RotPwr'' are used in the output to get rotor speed and power, respectively. The pitch angle value is set to 7.5° (optimal value in region2). The primary input file is as below:

Code: Select all

--------------------------------------------------------------------------------
------- FAST INPUT FILE --------------------------------------------------------
FAST certification Test #17: FAST model of a SWRT 3-bladed upwind turbine.  Note- SWRT rotates in CCW direction- some inputs will be mirror image of the actual turbine.
Model properties from "SWRTv1p2.adm" and SWRT "AdamsWT_MakeBladeDat_v12.xls".  JEM Jan., 2004.  Updated by J. Jonkman, NREL, Feb, 2004.  Compatible with FAST v7.02.00.
---------------------- SIMULATION CONTROL --------------------------------------
False       Echo        - Echo input data to "echo.out" (flag)
   3        ADAMSPrep   - ADAMS preprocessor mode {1: Run FAST, 2: use FAST as a preprocessor to create an ADAMS model, 3: do both} (switch)
   1        AnalMode    - Analysis mode {1: Run a time-marching simulation, 2: create a periodic linearized model} (switch)
   3        NumBl       - Number of blades (-)
  70.0      TMax        - Total run time (s)
   0.001    DT          - Integration time step (s)
---------------------- TURBINE CONTROL -----------------------------------------
   0        YCMode      - Yaw control mode {0: none, 1: user-defined from routine UserYawCont, 2: user-defined from Simulink/Labview} (switch)
9999.9      TYCOn       - Time to enable active yaw control (s) [unused when YCMode=0]
   0        PCMode      - Pitch control mode {0: none, 1: user-defined from routine PitchCntrl, 2: user-defined from Simulink/Labview} (switch)
9999.9      TPCOn       - Time to enable active pitch control (s) [unused when PCMode=0]
   0        VSContrl    - Variable-speed control mode {0: none, 1: simple VS, 2: user-defined from routine UserVSCont, 3: user-defined from Simulink/Labview} (switch)
9999.9      VS_RtGnSp   - Rated generator speed for simple variable-speed generator control (HSS side) (rpm) [used only when VSContrl=1]
9999.9      VS_RtTq     - Rated generator torque/constant generator torque in Region 3 for simple variable-speed generator control (HSS side) (N-m) [used only when VSContrl=1]
9999.9      VS_Rgn2K    - Generator torque constant in Region 2 for simple variable-speed generator control (HSS side) (N-m/rpm^2) [used only when VSContrl=1]
9999.9      VS_SlPc     - Rated generator slip percentage in Region 2 1/2 for simple variable-speed generator control (%) [used only when VSContrl=1]
   1        GenModel    - Generator model {1: simple, 2: Thevenin, 3: user-defined from routine UserGen} (switch) [used only when VSContrl=0]
True        GenTiStr    - Method to start the generator {T: timed using TimGenOn, F: generator speed using SpdGenOn} (flag)
True        GenTiStp    - Method to stop the generator {T: timed using TimGenOf, F: when generator power = 0} (flag)
9999.9      SpdGenOn    - Generator speed to turn on the generator for a startup (HSS speed) (rpm) [used only when GenTiStr=False]
   0.0      TimGenOn    - Time to turn on the generator for a startup (s) [used only when GenTiStr=True]
9999.9      TimGenOf    - Time to turn off the generator (s) [used only when GenTiStp=True]
   1        HSSBrMode   - HSS brake model {1: simple, 2: user-defined from routine UserHSSBr, 3: user-defined from Labview} (switch)
9999.9      THSSBrDp    - Time to initiate deployment of the HSS brake (s)
9999.9      TiDynBrk    - Time to initiate deployment of the dynamic generator brake [CURRENTLY IGNORED] (s)
9999.9      TTpBrDp(1)  - Time to initiate deployment of tip brake 1 (s)
9999.9      TTpBrDp(2)  - Time to initiate deployment of tip brake 2 (s)
9999.9      TTpBrDp(3)  - Time to initiate deployment of tip brake 3 (s) [unused for 2 blades]
9999.9      TBDepISp(1) - Deployment-initiation speed for the tip brake on blade 1 (rpm)
9999.9      TBDepISp(2) - Deployment-initiation speed for the tip brake on blade 2 (rpm)
9999.9      TBDepISp(3) - Deployment-initiation speed for the tip brake on blade 3 (rpm) [unused for 2 blades]
9999.9      TYawManS    - Time to start override yaw maneuver and end standard yaw control (s)
9999.9      TYawManE    - Time at which override yaw maneuver reaches final yaw angle (s)
   0.0      NacYawF     - Final yaw angle for yaw maneuvers (degrees)
9999.9      TPitManS(1) - Time to start override pitch maneuver for blade 1 and end standard pitch control (s)
9999.9      TPitManS(2) - Time to start override pitch maneuver for blade 2 and end standard pitch control (s)
9999.9      TPitManS(3) - Time to start override pitch maneuver for blade 3 and end standard pitch control (s) [unused for 2 blades]
9999.9      TPitManE(1) - Time at which override pitch maneuver for blade 1 reaches final pitch (s)
9999.9      TPitManE(2) - Time at which override pitch maneuver for blade 2 reaches final pitch (s)
9999.9      TPitManE(3) - Time at which override pitch maneuver for blade 3 reaches final pitch (s) [unused for 2 blades]
  7.5     BlPitch(1)  - Blade 1 initial pitch (degrees)
  7.5     BlPitch(2)  - Blade 2 initial pitch (degrees)
  7.5     BlPitch(3)  - Blade 3 initial pitch (degrees) [unused for 2 blades]
  7.5     BlPitchF(1) - Blade 1 final pitch for pitch maneuvers (degrees)
  7.5     BlPitchF(2) - Blade 2 final pitch for pitch maneuvers (degrees)
  7.5     BlPitchF(3) - Blade 3 final pitch for pitch maneuvers (degrees) [unused for 2 blades]
---------------------- ENVIRONMENTAL CONDITIONS --------------------------------
   9.81     Gravity     - Gravitational acceleration (m/s^2)
---------------------- FEATURE FLAGS -------------------------------------------
False          FlapDOF1    - First flapwise blade mode DOF (flag)
False          FlapDOF2    - Second flapwise blade mode DOF (flag)
False          EdgeDOF     - First edgewise blade mode DOF (flag)
False          TeetDOF     - Rotor-teeter DOF (flag) [unused for 3 blades]
False          DrTrDOF     - Drivetrain rotational-flexibility DOF (flag)
True           GenDOF      - Generator DOF (flag)
False          YawDOF      - Yaw DOF (flag)
False          TwFADOF1    - First fore-aft tower bending-mode DOF (flag)
False          TwFADOF2    - Second fore-aft tower bending-mode DOF (flag)
False          TwSSDOF1    - First side-to-side tower bending-mode DOF (flag)
False          TwSSDOF2    - Second side-to-side tower bending-mode DOF (flag)
True           CompAero    - Compute aerodynamic forces (flag)
False          CompNoise   - Compute aerodynamic noise (flag)
---------------------- INITIAL CONDITIONS --------------------------------------
   0.0      OoPDefl     - Initial out-of-plane blade-tip displacement (meters)
   0.0      IPDefl      - Initial in-plane blade-tip deflection (meters)
   0.0      TeetDefl    - Initial or fixed teeter angle (degrees) [unused for 3 blades]
   0.0      Azimuth     - Initial azimuth angle for blade 1 (degrees)
     0      RotSpeed    - Initial or fixed rotor speed (rpm)
   0.0      NacYaw      - Initial or fixed nacelle-yaw angle (degrees)
   0.0      TTDspFA     - Initial fore-aft tower-top displacement (meters)
   0.0      TTDspSS     - Initial side-to-side tower-top displacement (meters)
---------------------- TURBINE CONFIGURATION -----------------------------------
   2.90     TipRad      - The distance from the rotor apex to the blade tip (meters)
   0.303    HubRad      - The distance from the rotor apex to the blade root (meters)
   1        PSpnElN     - Number of the innermost blade element which is still part of the pitchable portion of the blade for partial-span pitch control [1 to BldNodes] [CURRENTLY IGNORED] (-)
   0.0      UndSling    - Undersling length [distance from teeter pin to the rotor apex] (meters) [unused for 3 blades]
   0.1536   HubCM       - Distance from rotor apex to hub mass [positive downwind] (meters)
  -0.7456   OverHang    - Distance from yaw axis to rotor apex [3 blades] or teeter pin [2 blades] (meters)
  -0.2307   NacCMxn     - Downwind distance from the tower-top to the nacelle CM (meters)
   0.0910   NacCMyn     - Lateral  distance from the tower-top to the nacelle CM (meters)
   0.5475   NacCMzn     - Vertical distance from the tower-top to the nacelle CM (meters)
  34.0      TowerHt     - Height of tower above ground level [onshore] or MSL [offshore] (meters)
   0.515112 Twr2Shft    - Vertical distance from the tower-top to the rotor shaft (meters)
   0.0      TwrRBHt     - Tower rigid base height (meters)
  -8.0      ShftTilt    - Rotor shaft tilt angle (degrees).  Negative for an upwind rotor.
   0.0      Delta3      - Delta-3 angle for teetering rotors (degrees) [unused for 3 blades]
   0.0      PreCone(1)  - Blade 1 cone angle (degrees)
   0.0      PreCone(2)  - Blade 2 cone angle (degrees)
   0.0      PreCone(3)  - Blade 3 cone angle (degrees) [unused for 2 blades]
   0.0      AzimB1Up    - Azimuth value to use for I/O when blade 1 points up (degrees)
---------------------- MASS AND INERTIA ----------------------------------------
   0.0      YawBrMass   - Yaw bearing mass (kg)
 260.5      NacMass     - Nacelle mass (kg)
 113.0      HubMass     - Hub mass (kg)
   0.0      TipMass(1)  - Tip-brake mass, blade 1 (kg)
   0.0      TipMass(2)  - Tip-brake mass, blade 2 (kg)
   0.0      TipMass(3)  - Tip-brake mass, blade 3 (kg) [unused for 2 blades]
  39.81     NacYIner    - Nacelle inertia about yaw axis (kg m^2)
   0.5      GenIner     - Generator inertia about HSS (kg m^2)
   7.71     HubIner     - Hub inertia about rotor axis [3 blades] or teeter axis [2 blades] (kg m^2)
---------------------- DRIVETRAIN ----------------------------------------------
 100.0      GBoxEff     - Gearbox efficiency (%)
  100.0      GenEff      - Generator efficiency [ignored by the Thevenin and user-defined generator models] (%)
   1.0      GBRatio     - Gearbox ratio (-)
False       GBRevers    - Gearbox reversal {T: if rotor and generator rotate in opposite directions} (flag)
9999.9      HSSBrTqF    - Fully deployed HSS-brake torque (N-m)
9999.9      HSSBrDT     - Time for HSS-brake to reach full deployment once initiated (sec) [used only when HSSBrMode=1]
"unused"    DynBrkFi    - File containing a mech-gen-torque vs HSS-speed curve for a dynamic brake [CURRENTLY IGNORED] (quoted string)
9999.9      DTTorSpr    - Drivetrain torsional spring (N-m/rad)
9999.9      DTTorDmp    - Drivetrain torsional damper (N-m/(rad/s))
---------------------- SIMPLE INDUCTION GENERATOR ------------------------------
9999.9      SIG_SlPc    - Rated generator slip percentage (%) [used only when VSContrl=0 and GenModel=1]
9999.9      SIG_SySp    - Synchronous (zero-torque) generator speed (rpm) [used only when VSContrl=0 and GenModel=1]
9999.9      SIG_RtTq    - Rated torque (N-m) [used only when VSContrl=0 and GenModel=1]
9999.9      SIG_PORt    - Pull-out ratio (Tpullout/Trated) (-) [used only when VSContrl=0 and GenModel=1]
---------------------- THEVENIN-EQUIVALENT INDUCTION GENERATOR -----------------
9999.9      TEC_Freq    - Line frequency [50 or 60] (Hz) [used only when VSContrl=0 and GenModel=2]
9998        TEC_NPol    - Number of poles [even integer > 0] (-) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_SRes    - Stator resistance (ohms) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_RRes    - Rotor resistance (ohms) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_VLL     - Line-to-line RMS voltage (volts) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_SLR     - Stator leakage reactance (ohms) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_RLR     - Rotor leakage reactance (ohms) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_MR      - Magnetizing reactance (ohms) [used only when VSContrl=0 and GenModel=2]
---------------------- PLATFORM ------------------------------------------------
   0        PtfmModel   - Platform model {0: none, 1: onshore, 2: fixed bottom offshore, 3: floating offshore} (switch)
"unused"    PtfmFile    - Name of file containing platform properties (quoted string) [unused when PtfmModel=0]
---------------------- TOWER ---------------------------------------------------
  10        TwrNodes    - Number of tower nodes used for analysis (-)
"SWRT_Tower.dat"        TwrFile - Name of file containing tower properties (quoted string)
---------------------- NACELLE-YAW ---------------------------------------------
   0.0      YawSpr      - Nacelle-yaw spring constant (N-m/rad)
   0.0      YawDamp     - Nacelle-yaw damping constant (N-m/(rad/s))
   0.0      YawNeut     - Neutral yaw position--yaw spring force is zero at this yaw (degrees)
---------------------- FURLING -------------------------------------------------
True        Furling     - Read in additional model properties for furling turbine (flag)
"SWRT_Furl.dat"         FurlFile    - Name of file containing furling properties (quoted string) [unused when Furling=False]
---------------------- ROTOR-TEETER --------------------------------------------
   0        TeetMod     - Rotor-teeter spring/damper model {0: none, 1: standard, 2: user-defined from routine UserTeet} (switch) [unused for 3 blades]
   0.0      TeetDmpP    - Rotor-teeter damper position (degrees) [used only for 2 blades and when TeetMod=1]
   0.0      TeetDmp     - Rotor-teeter damping constant (N-m/(rad/s)) [used only for 2 blades and when TeetMod=1]
   0.0      TeetCDmp    - Rotor-teeter rate-independent Coulomb-damping moment (N-m) [used only for 2 blades and when TeetMod=1]
   0.0      TeetSStP    - Rotor-teeter soft-stop position (degrees) [used only for 2 blades and when TeetMod=1]
   0.0      TeetHStP    - Rotor-teeter hard-stop position (degrees) [used only for 2 blades and when TeetMod=1]
   0.0      TeetSSSp    - Rotor-teeter soft-stop linear-spring constant (N-m/rad) [used only for 2 blades and when TeetMod=1]
   0.0      TeetHSSp    - Rotor-teeter hard-stop linear-spring constant (N-m/rad) [used only for 2 blades and when TeetMod=1]
---------------------- TIP-BRAKE -----------------------------------------------
   0.0      TBDrConN    - Tip-brake drag constant during normal operation, Cd*Area (m^2)
   0.0      TBDrConD    - Tip-brake drag constant during fully-deployed operation, Cd*Area (m^2)
   0.0      TpBrDT      - Time for tip-brake to reach full deployment once released (sec)
---------------------- BLADE ---------------------------------------------------
"SWRT_Blade.dat"        BldFile(1)  - Name of file containing properties for blade 1 (quoted string)
"SWRT_Blade.dat"        BldFile(2)  - Name of file containing properties for blade 2 (quoted string)
"SWRT_Blade.dat"        BldFile(3)  - Name of file containing properties for blade 3 (quoted string) [unused for 2 blades]
---------------------- AERODYN -------------------------------------------------
"Test17_AD.ipt"         ADFile      - Name of file containing AeroDyn input parameters (quoted string)
---------------------- NOISE ---------------------------------------------------
"unused"    NoiseFile   - Name of file containing aerodynamic noise input parameters (quoted string) [used only when CompNoise=True]
---------------------- ADAMS ---------------------------------------------------
"SWRT_ADAMS.dat"        ADAMSFile   - Name of file containing ADAMS-specific input parameters (quoted string) [unused when ADAMSPrep=1]
---------------------- LINEARIZATION CONTROL -----------------------------------
"SWRT_Linear.dat"       LinFile     - Name of file containing FAST linearization parameters (quoted string) [unused when AnalMode=1]
---------------------- OUTPUT --------------------------------------------------
True        SumPrint    - Print summary data to "<RootName>.fsm" (flag)
1           OutFileFmt  - Format for tabular (time-marching) output file(s) (1: text file [<RootName>.out], 2: binary file [<RootName>.outb], 3: both) (switch)
True        TabDelim    - Use tab delimiters in text tabular output file? (flag)
"ES10.3E2"  OutFmt      - Format used for text tabular output (except time).  Resulting field should be 10 characters. (quoted string)  [not checked for validity!]
  10.0      TStart      - Time to begin tabular output (s)
   8        DecFact     - Decimation factor for tabular output {1: output every time step} (-)
   1.0      SttsTime    - Amount of time between screen status messages (sec)
   0.0      NcIMUxn     - Downwind distance from the tower-top to the nacelle IMU (meters)
   0.0      NcIMUyn     - Lateral  distance from the tower-top to the nacelle IMU (meters)
   0.0      NcIMUzn     - Vertical distance from the tower-top to the nacelle IMU (meters)
   0.1      ShftGagL    - Distance from rotor apex [3 blades] or teeter pin [2 blades] to shaft strain gages [positive for upwind rotors] (meters)
   0        NTwGages    - Number of tower nodes that have strain gages for output [0 to 9] (-)
   0        TwrGagNd    - List of tower nodes that have strain gages [1 to TwrNodes] (-) [unused if NTwGages=0]
   0        NBlGages    - Number of blade nodes that have strain gages for output [0 to 9] (-)
   0        BldGagNd    - List of blade nodes that have strain gages [1 to BldNodes] (-) [unused if NBlGages=0]
            OutList     - The next line(s) contains a list of output parameters.  See OutList.xlsx for a listing of available output channels, (-)
"RotSpeed"
"RotPwr"

END of FAST input file (the word "END" must appear in the first 3 columns of this last line).
--------------------------------------------------------------------------------




However, the speed and power curves do not seem to be correct, Fig2. Speed increases and settles in a constant value and the power is a negligible negative value.
I would be appreciated to let me know what could be the problem.

Kind regards,
Babak
Attachments
Fig2.JPG
Speed and power curves
Fig2.JPG (34.17 KiB) Viewed 451 times

Jason.Jonkman
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Location: Boulder, CO
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Re: Linearization issue using Fast V7.02

Postby Jason.Jonkman » Mon Apr 20, 2020 7:29 am

Dear Babak,

If you enable GenDOF, you must enable a generator model or torque controller to regulate the rotor / generator speed. In your case, you've set VSContrl = 0 and GenModel = 1, which selects the simple induction generator (SIG) model. But all of your SIG inputs (SIG_SlPc, SIG_SySp, SIG_RtTq, and SIG_PORt) are set to meaningless values (9999.9), which is resulting in the unexpected behavior.

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

Babak.Gavgani
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Joined: Sat Mar 14, 2020 12:03 pm
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Location: Belgium

Re: Linearization issue using Fast V7.02

Postby Babak.Gavgani » Tue Apr 21, 2020 7:17 am

Dear Jason,

Thanks for your reply.
1. I want to use PMSG generator model, what needs to be done for linearization? (Considering that the dynamics of the generator is too fast comparing to the turbine aerodynamical equations so the generator model can not much effect the linearization, right?)

2. If I want to find the ''MPP Rotational Speed'' for linearization around it, it is better to find the optimal value of the Tips Speed Ratio (TSR) (For example for 10kW turbine, Optimal TSR is 5.6) and then find the optimal value of the rotational speed for every wind speed (according to : TSR = (Radius*Rotation Speed)/Wind Speed) or find it according to the Power-Rotational Speed curves?
I would be appreciated to advice me on this.

Kind regards,
Babak

Jason.Jonkman
Posts: 4862
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Linearization issue using Fast V7.02

Postby Jason.Jonkman » Tue Apr 21, 2020 9:21 am

Dear Babak,

Here are my answers to your questions:

1. As far as FAST and its linearization are concerned, likely the most important feature to capture is the slope of the generator torque versus generator speed curve. You can likely use the simple inputs to the SIG model to capture the correct torque-speed relationship.

2. I'm not sure I fully understand your question, but I would think the result from either approach would be the same if done consistently.

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

Babak.Gavgani
Posts: 29
Joined: Sat Mar 14, 2020 12:03 pm
Organization: ---
Location: Belgium

Re: Linearization issue using Fast V7.02

Postby Babak.Gavgani » Mon May 25, 2020 12:51 pm

Dear Jason,

I have linearized the 10kW wind turbine at 11.5 m/s wind speed (rated wind speed) around optimal rotational speed which is calculated as below:
Optimal Rotor Speed = (Optimal TSR * Wind Speed)/Radius = 22.20689 rad/sec
in which the Optimal TSR for the 10kW wind turbine is 5.6 and Radius = 2.9m. I have fixed the pitch angle to its optimal value, 7.5° and only the GenDOF is active and the Rotor speed is set to 22.20689.
The primary input file and the linearization output file are as below:

Code: Select all

This linearized model file was generated by FAST (v7.02.00d-bjj, 20-Feb-2013) on 23-Apr-2020 at 02:41:32.
The aerodynamic calculations were made by AeroDyn (v13.00.02a-bjj, 20-Feb-2013).

 FAST certification Test #17: FAST model of a SWRT 3-bladed upwind turbine.  Note- SWRT rotates in CCW direction- some inputs will be mirror image of the actual turbine.


Some Useful Information:

   Type of steady state solution found                Trimmed generator torque (TrimCase = 2)
   Azimuth-average rotor speed, RotSpeed      (rad/s)    2.22069E+01
   Period of steady state solution              (sec)    2.82939E-01
   Iterations needed to find steady state solution     253
   Displacement 2-norm of steady state solution (rad)    4.47321E-03
   Velocity 2-norm of steady state solution   (rad/s)    2.46429E-03
   Number of equally-speced azimuth steps, NAzimStep    36
   Order of linearized model, MdlOrder                   1
   Number of active (enabled) DOFs                       1 ( 2 states)
   Number of control inputs, NInputs                     1
   Number of input wind disturbances, NDisturbs          0
   Number of output measurements                         1


Order of States in Linearized State Matrices:

   Row/column  1 = Variable speed generator DOF (internal DOF index = DOF_GeAz)
   Row/column  2 to  2 = First derivatives of row/column  1 to  1.


Order of Control Inputs in Linearized State Matrices:

   Column 1 = electrical generator torque       (N·m)    4.36029E+02 op


Order of Input Wind Disturbances in Linearized State Matrices:

   None selected


Order of Output Measurements in Linearized State Matrices:

   Row   1 = LSSTipV    (rpm)     


Code: Select all

--------------------------------------------------------------------------------
------- FAST INPUT FILE --------------------------------------------------------
FAST certification Test #17: FAST model of a SWRT 3-bladed upwind turbine.  Note- SWRT rotates in CCW direction- some inputs will be mirror image of the actual turbine.
Model properties from "SWRTv1p2.adm" and SWRT "AdamsWT_MakeBladeDat_v12.xls".  JEM Jan., 2004.  Updated by J. Jonkman, NREL, Feb, 2004.  Compatible with FAST v7.02.00.
---------------------- SIMULATION CONTROL --------------------------------------
False       Echo        - Echo input data to "echo.out" (flag)
   3        ADAMSPrep   - ADAMS preprocessor mode {1: Run FAST, 2: use FAST as a preprocessor to create an ADAMS model, 3: do both} (switch)
   2        AnalMode    - Analysis mode {1: Run a time-marching simulation, 2: create a periodic linearized model} (switch)
   3        NumBl       - Number of blades (-)
   300      TMax        - Total run time (s)
   0.001    DT          - Integration time step (s)
---------------------- TURBINE CONTROL -----------------------------------------
   0        YCMode      - Yaw control mode {0: none, 1: user-defined from routine UserYawCont, 2: user-defined from Simulink/Labview} (switch)
9999.9      TYCOn       - Time to enable active yaw control (s) [unused when YCMode=0]
   0        PCMode      - Pitch control mode {0: none, 1: user-defined from routine PitchCntrl, 2: user-defined from Simulink/Labview} (switch)
9999.9      TPCOn       - Time to enable active pitch control (s) [unused when PCMode=0]
   0        VSContrl    - Variable-speed control mode {0: none, 1: simple VS, 2: user-defined from routine UserVSCont, 3: user-defined from Simulink/Labview} (switch)
9999.9      VS_RtGnSp   - Rated generator speed for simple variable-speed generator control (HSS side) (rpm) [used only when VSContrl=1]
9999.9      VS_RtTq     - Rated generator torque/constant generator torque in Region 3 for simple variable-speed generator control (HSS side) (N-m) [used only when VSContrl=1]
9999.9      VS_Rgn2K    - Generator torque constant in Region 2 for simple variable-speed generator control (HSS side) (N-m/rpm^2) [used only when VSContrl=1]
9999.9      VS_SlPc     - Rated generator slip percentage in Region 2 1/2 for simple variable-speed generator control (%) [used only when VSContrl=1]
   1        GenModel    - Generator model {1: simple, 2: Thevenin, 3: user-defined from routine UserGen} (switch) [used only when VSContrl=0]
True        GenTiStr    - Method to start the generator {T: timed using TimGenOn, F: generator speed using SpdGenOn} (flag)
True        GenTiStp    - Method to stop the generator {T: timed using TimGenOf, F: when generator power = 0} (flag)
9999.9      SpdGenOn    - Generator speed to turn on the generator for a startup (HSS speed) (rpm) [used only when GenTiStr=False]
   0.0      TimGenOn    - Time to turn on the generator for a startup (s) [used only when GenTiStr=True]
9999.9      TimGenOf    - Time to turn off the generator (s) [used only when GenTiStp=True]
   1        HSSBrMode   - HSS brake model {1: simple, 2: user-defined from routine UserHSSBr, 3: user-defined from Labview} (switch)
9999.9      THSSBrDp    - Time to initiate deployment of the HSS brake (s)
9999.9      TiDynBrk    - Time to initiate deployment of the dynamic generator brake [CURRENTLY IGNORED] (s)
9999.9      TTpBrDp(1)  - Time to initiate deployment of tip brake 1 (s)
9999.9      TTpBrDp(2)  - Time to initiate deployment of tip brake 2 (s)
9999.9      TTpBrDp(3)  - Time to initiate deployment of tip brake 3 (s) [unused for 2 blades]
9999.9      TBDepISp(1) - Deployment-initiation speed for the tip brake on blade 1 (rpm)
9999.9      TBDepISp(2) - Deployment-initiation speed for the tip brake on blade 2 (rpm)
9999.9      TBDepISp(3) - Deployment-initiation speed for the tip brake on blade 3 (rpm) [unused for 2 blades]
9999.9      TYawManS    - Time to start override yaw maneuver and end standard yaw control (s)
9999.9      TYawManE    - Time at which override yaw maneuver reaches final yaw angle (s)
   0.0      NacYawF     - Final yaw angle for yaw maneuvers (degrees)
9999.9      TPitManS(1) - Time to start override pitch maneuver for blade 1 and end standard pitch control (s)
9999.9      TPitManS(2) - Time to start override pitch maneuver for blade 2 and end standard pitch control (s)
9999.9      TPitManS(3) - Time to start override pitch maneuver for blade 3 and end standard pitch control (s) [unused for 2 blades]
9999.9      TPitManE(1) - Time at which override pitch maneuver for blade 1 reaches final pitch (s)
9999.9      TPitManE(2) - Time at which override pitch maneuver for blade 2 reaches final pitch (s)
9999.9      TPitManE(3) - Time at which override pitch maneuver for blade 3 reaches final pitch (s) [unused for 2 blades]
  7.5     BlPitch(1)  - Blade 1 initial pitch (degrees)
  7.5     BlPitch(2)  - Blade 2 initial pitch (degrees)
  7.5     BlPitch(3)  - Blade 3 initial pitch (degrees) [unused for 2 blades]
  7.5     BlPitchF(1) - Blade 1 final pitch for pitch maneuvers (degrees)
  7.5     BlPitchF(2) - Blade 2 final pitch for pitch maneuvers (degrees)
  7.5     BlPitchF(3) - Blade 3 final pitch for pitch maneuvers (degrees) [unused for 2 blades]
---------------------- ENVIRONMENTAL CONDITIONS --------------------------------
   9.81     Gravity     - Gravitational acceleration (m/s^2)
---------------------- FEATURE FLAGS -------------------------------------------
False          FlapDOF1    - First flapwise blade mode DOF (flag)
False          FlapDOF2    - Second flapwise blade mode DOF (flag)
False          EdgeDOF     - First edgewise blade mode DOF (flag)
False          TeetDOF     - Rotor-teeter DOF (flag) [unused for 3 blades]
False          DrTrDOF     - Drivetrain rotational-flexibility DOF (flag)
True           GenDOF      - Generator DOF (flag)
False          YawDOF      - Yaw DOF (flag)
False          TwFADOF1    - First fore-aft tower bending-mode DOF (flag)
False          TwFADOF2    - Second fore-aft tower bending-mode DOF (flag)
False          TwSSDOF1    - First side-to-side tower bending-mode DOF (flag)
False          TwSSDOF2    - Second side-to-side tower bending-mode DOF (flag)
True           CompAero    - Compute aerodynamic forces (flag)
False          CompNoise   - Compute aerodynamic noise (flag)
---------------------- INITIAL CONDITIONS --------------------------------------
   0.0      OoPDefl     - Initial out-of-plane blade-tip displacement (meters)
   0.0      IPDefl      - Initial in-plane blade-tip deflection (meters)
   0.0      TeetDefl    - Initial or fixed teeter angle (degrees) [unused for 3 blades]
   0.0      Azimuth     - Initial azimuth angle for blade 1 (degrees)
212.061    RotSpeed    - Initial or fixed rotor speed (rpm)
   0.0      NacYaw      - Initial or fixed nacelle-yaw angle (degrees)
   0.0      TTDspFA     - Initial fore-aft tower-top displacement (meters)
   0.0      TTDspSS     - Initial side-to-side tower-top displacement (meters)
---------------------- TURBINE CONFIGURATION -----------------------------------
   2.90     TipRad      - The distance from the rotor apex to the blade tip (meters)
   0.303    HubRad      - The distance from the rotor apex to the blade root (meters)
   1        PSpnElN     - Number of the innermost blade element which is still part of the pitchable portion of the blade for partial-span pitch control [1 to BldNodes] [CURRENTLY IGNORED] (-)
   0.0      UndSling    - Undersling length [distance from teeter pin to the rotor apex] (meters) [unused for 3 blades]
   0.1536   HubCM       - Distance from rotor apex to hub mass [positive downwind] (meters)
  -0.7456   OverHang    - Distance from yaw axis to rotor apex [3 blades] or teeter pin [2 blades] (meters)
  -0.2307   NacCMxn     - Downwind distance from the tower-top to the nacelle CM (meters)
   0.0910   NacCMyn     - Lateral  distance from the tower-top to the nacelle CM (meters)
   0.5475   NacCMzn     - Vertical distance from the tower-top to the nacelle CM (meters)
  34.0      TowerHt     - Height of tower above ground level [onshore] or MSL [offshore] (meters)
   0.515112 Twr2Shft    - Vertical distance from the tower-top to the rotor shaft (meters)
   0.0      TwrRBHt     - Tower rigid base height (meters)
  -8.0      ShftTilt    - Rotor shaft tilt angle (degrees).  Negative for an upwind rotor.
   0.0      Delta3      - Delta-3 angle for teetering rotors (degrees) [unused for 3 blades]
   0.0      PreCone(1)  - Blade 1 cone angle (degrees)
   0.0      PreCone(2)  - Blade 2 cone angle (degrees)
   0.0      PreCone(3)  - Blade 3 cone angle (degrees) [unused for 2 blades]
   0.0      AzimB1Up    - Azimuth value to use for I/O when blade 1 points up (degrees)
---------------------- MASS AND INERTIA ----------------------------------------
   0.0      YawBrMass   - Yaw bearing mass (kg)
 260.5      NacMass     - Nacelle mass (kg)
 113.0      HubMass     - Hub mass (kg)
   0.0      TipMass(1)  - Tip-brake mass, blade 1 (kg)
   0.0      TipMass(2)  - Tip-brake mass, blade 2 (kg)
   0.0      TipMass(3)  - Tip-brake mass, blade 3 (kg) [unused for 2 blades]
  39.81     NacYIner    - Nacelle inertia about yaw axis (kg m^2)
   0.5      GenIner     - Generator inertia about HSS (kg m^2)
   7.71     HubIner     - Hub inertia about rotor axis [3 blades] or teeter axis [2 blades] (kg m^2)
---------------------- DRIVETRAIN ----------------------------------------------
 100.0      GBoxEff     - Gearbox efficiency (%)
  100.0      GenEff      - Generator efficiency [ignored by the Thevenin and user-defined generator models] (%)
   1.0      GBRatio     - Gearbox ratio (-)
False       GBRevers    - Gearbox reversal {T: if rotor and generator rotate in opposite directions} (flag)
9999.9      HSSBrTqF    - Fully deployed HSS-brake torque (N-m)
9999.9      HSSBrDT     - Time for HSS-brake to reach full deployment once initiated (sec) [used only when HSSBrMode=1]
"unused"    DynBrkFi    - File containing a mech-gen-torque vs HSS-speed curve for a dynamic brake [CURRENTLY IGNORED] (quoted string)
9999.9      DTTorSpr    - Drivetrain torsional spring (N-m/rad)
9999.9      DTTorDmp    - Drivetrain torsional damper (N-m/(rad/s))
---------------------- SIMPLE INDUCTION GENERATOR ------------------------------
9999.9      SIG_SlPc    - Rated generator slip percentage (%) [used only when VSContrl=0 and GenModel=1]
9999.9      SIG_SySp    - Synchronous (zero-torque) generator speed (rpm) [used only when VSContrl=0 and GenModel=1]
9999.9      SIG_RtTq    - Rated torque (N-m) [used only when VSContrl=0 and GenModel=1]
9999.9      SIG_PORt    - Pull-out ratio (Tpullout/Trated) (-) [used only when VSContrl=0 and GenModel=1]
---------------------- THEVENIN-EQUIVALENT INDUCTION GENERATOR -----------------
9999.9      TEC_Freq    - Line frequency [50 or 60] (Hz) [used only when VSContrl=0 and GenModel=2]
9998        TEC_NPol    - Number of poles [even integer > 0] (-) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_SRes    - Stator resistance (ohms) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_RRes    - Rotor resistance (ohms) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_VLL     - Line-to-line RMS voltage (volts) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_SLR     - Stator leakage reactance (ohms) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_RLR     - Rotor leakage reactance (ohms) [used only when VSContrl=0 and GenModel=2]
9999.9      TEC_MR      - Magnetizing reactance (ohms) [used only when VSContrl=0 and GenModel=2]
---------------------- PLATFORM ------------------------------------------------
   0        PtfmModel   - Platform model {0: none, 1: onshore, 2: fixed bottom offshore, 3: floating offshore} (switch)
"unused"    PtfmFile    - Name of file containing platform properties (quoted string) [unused when PtfmModel=0]
---------------------- TOWER ---------------------------------------------------
  10        TwrNodes    - Number of tower nodes used for analysis (-)
"SWRT_Tower.dat"        TwrFile - Name of file containing tower properties (quoted string)
---------------------- NACELLE-YAW ---------------------------------------------
   0.0      YawSpr      - Nacelle-yaw spring constant (N-m/rad)
   0.0      YawDamp     - Nacelle-yaw damping constant (N-m/(rad/s))
   0.0      YawNeut     - Neutral yaw position--yaw spring force is zero at this yaw (degrees)
---------------------- FURLING -------------------------------------------------
False        Furling     - Read in additional model properties for furling turbine (flag)
"SWRT_Furl.dat"         FurlFile    - Name of file containing furling properties (quoted string) [unused when Furling=False]
---------------------- ROTOR-TEETER --------------------------------------------
   0        TeetMod     - Rotor-teeter spring/damper model {0: none, 1: standard, 2: user-defined from routine UserTeet} (switch) [unused for 3 blades]
   0.0      TeetDmpP    - Rotor-teeter damper position (degrees) [used only for 2 blades and when TeetMod=1]
   0.0      TeetDmp     - Rotor-teeter damping constant (N-m/(rad/s)) [used only for 2 blades and when TeetMod=1]
   0.0      TeetCDmp    - Rotor-teeter rate-independent Coulomb-damping moment (N-m) [used only for 2 blades and when TeetMod=1]
   0.0      TeetSStP    - Rotor-teeter soft-stop position (degrees) [used only for 2 blades and when TeetMod=1]
   0.0      TeetHStP    - Rotor-teeter hard-stop position (degrees) [used only for 2 blades and when TeetMod=1]
   0.0      TeetSSSp    - Rotor-teeter soft-stop linear-spring constant (N-m/rad) [used only for 2 blades and when TeetMod=1]
   0.0      TeetHSSp    - Rotor-teeter hard-stop linear-spring constant (N-m/rad) [used only for 2 blades and when TeetMod=1]
---------------------- TIP-BRAKE -----------------------------------------------
   0.0      TBDrConN    - Tip-brake drag constant during normal operation, Cd*Area (m^2)
   0.0      TBDrConD    - Tip-brake drag constant during fully-deployed operation, Cd*Area (m^2)
   0.0      TpBrDT      - Time for tip-brake to reach full deployment once released (sec)
---------------------- BLADE ---------------------------------------------------
"SWRT_Blade.dat"        BldFile(1)  - Name of file containing properties for blade 1 (quoted string)
"SWRT_Blade.dat"        BldFile(2)  - Name of file containing properties for blade 2 (quoted string)
"SWRT_Blade.dat"        BldFile(3)  - Name of file containing properties for blade 3 (quoted string) [unused for 2 blades]
---------------------- AERODYN -------------------------------------------------
"Test17L_AD.ipt"         ADFile      - Name of file containing AeroDyn input parameters (quoted string)
---------------------- NOISE ---------------------------------------------------
"unused"    NoiseFile   - Name of file containing aerodynamic noise input parameters (quoted string) [used only when CompNoise=True]
---------------------- ADAMS ---------------------------------------------------
"SWRT_ADAMS.dat"        ADAMSFile   - Name of file containing ADAMS-specific input parameters (quoted string) [unused when ADAMSPrep=1]
---------------------- LINEARIZATION CONTROL -----------------------------------
"SWRT_Linear.dat"       LinFile     - Name of file containing FAST linearization parameters (quoted string) [unused when AnalMode=1]
---------------------- OUTPUT --------------------------------------------------
True        SumPrint    - Print summary data to "<RootName>.fsm" (flag)
1           OutFileFmt  - Format for tabular (time-marching) output file(s) (1: text file [<RootName>.out], 2: binary file [<RootName>.outb], 3: both) (switch)
True        TabDelim    - Use tab delimiters in text tabular output file? (flag)
"ES10.3E2"  OutFmt      - Format used for text tabular output (except time).  Resulting field should be 10 characters. (quoted string)  [not checked for validity!]
  10.0      TStart      - Time to begin tabular output (s)
   8        DecFact     - Decimation factor for tabular output {1: output every time step} (-)
   1.0      SttsTime    - Amount of time between screen status messages (sec)
   0.0      NcIMUxn     - Downwind distance from the tower-top to the nacelle IMU (meters)
   0.0      NcIMUyn     - Lateral  distance from the tower-top to the nacelle IMU (meters)
   0.0      NcIMUzn     - Vertical distance from the tower-top to the nacelle IMU (meters)
   0.1      ShftGagL    - Distance from rotor apex [3 blades] or teeter pin [2 blades] to shaft strain gages [positive for upwind rotors] (meters)
   0        NTwGages    - Number of tower nodes that have strain gages for output [0 to 9] (-)
   0        TwrGagNd    - List of tower nodes that have strain gages [1 to TwrNodes] (-) [unused if NTwGages=0]
   0        NBlGages    - Number of blade nodes that have strain gages for output [0 to 9] (-)
   0        BldGagNd    - List of blade nodes that have strain gages [1 to BldNodes] (-) [unused if NBlGages=0]
            OutList     - The next line(s) contains a list of output parameters.  See OutList.xlsx for a listing of available output channels, (-)
"LSSTipV"


END of FAST input file (the word "END" must appear in the first 3 columns of this last line).
--------------------------------------------------------------------------------



I calculated the power through multiplying rotor speed and generator torque at operating point which the linearization has been done (MPP). I expected it to be 10 kW because the rated wind speed (11.5m/s) has been considered but it is 9.682 kW. I would be appreciated to let me know what could be the problem?
(Generator and gearbox efficiencies are 1)

Kind regards,
Babak

Jason.Jonkman
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Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
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Re: Linearization issue using Fast V7.02

Postby Jason.Jonkman » Tue May 26, 2020 3:39 pm

Dear Babak,

I'm not too familiar with the design details of the SWRT turbine model, which it appears that you are using, to confirm all of your numbers (e.g., the optimal TSR and pitch), but I would guess that the SWRT FAST model does not predict 10 kW at the conditions are you simulating. You may want to start be using FAST in the time-domain mode to calculate the steady-state power (and perhaps torque) as a function of wind speed and pitch angle to understand what to expect through the FAST linearization (steady-state operating point / trim) process.

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

Babak.Gavgani
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Joined: Sat Mar 14, 2020 12:03 pm
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Location: Belgium

Re: Linearization issue using Fast V7.02

Postby Babak.Gavgani » Wed May 27, 2020 3:36 am

Dear Jason,

Thanks for your reply.
The values for optimal TSR and pitch angle are correct. Generator torque has trimmed to obtain the linearized model of the turbine at the optimal rotational speed (MPP). Only GenDOF is active.
The rated wind speed for 10kW wind turbine is 11.5 m/s so If we linearize the turbine at the optimal rotor speed (in the MPP) under 11.5 m/s wind speed, the calculated power according to the linarization output file should be 10kW but it is lees than 10kW. If you look at the linearization output file in my previous post, the rotational speed*torque is 9.682kW.
Even for the other wind speeds, less than the rated value, it is the same. the obtained power does not match with the MPP according to the linearization output file.

All the bests,
Babak

Jason.Jonkman
Posts: 4862
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Linearization issue using Fast V7.02

Postby Jason.Jonkman » Wed May 27, 2020 6:38 am

Der Babak,

As I said, this FAST model does not appear to predict a power of 10 kW at the conditions you've simulated. I would recommend using FAST in the time-domain mode to calculate the steady-state power (and perhaps torque) as a function of wind speed and pitch angle to understand what to expect through the FAST linearization (steady-state operating point / trim) process.

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

Babak.Gavgani
Posts: 29
Joined: Sat Mar 14, 2020 12:03 pm
Organization: ---
Location: Belgium

Re: Linearization issue using Fast V7.02

Postby Babak.Gavgani » Fri May 29, 2020 3:29 am

Dear Jason,

Thanks for your helps.
I searched the forum about the linearization and in one of your posts you have mentioned:
Cq (torque coefficient) usually reaches a maximum at a TSR slightly below the TSR for optimal power coefficient (Cp) for a given blade-pitch angle.

Please let me know, can it be the reason why the calculated power through linearization around MPP is less than the expected value?
Because the calculated torque through linearization is the torque value for TSR below the optimal TSR for the Cpmax.

Best regards,
Babak

Jason.Jonkman
Posts: 4862
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Linearization issue using Fast V7.02

Postby Jason.Jonkman » Fri May 29, 2020 6:46 am

Dear Babak,

I would not expect this characteristic of most Cq and Cp versus TSR curves to be the cause of the issue you are seeing. I think the FAST model simply predicts a lower power than you are expecting. I would verify this through time-domain simulations, independent from a linearization analysis.

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

Babak.Gavgani
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Re: Linearization issue using Fast V7.02

Postby Babak.Gavgani » Fri May 29, 2020 8:30 am

Dear Jason,

Thanks for your reply.
I tried this:
I disabled all DOFs and I set the rotor speed to its optimal value through equation below and setting the TSR to its optimal value = 5.6.
TSR = Rotor radius * Rotor speed/wind speed
Considering 10m/s wind speed, the optimal rotor speed is 184.4 rpm.
I obtained "RtTSR", "RtAeroCp", and "RtAeroPwr" from AeroDyn. However, TSR value is 5.65, Cp is 0.391 and RtAeroPwr is 6.15 kW.
I expected that the Cp to be its optimal velue (0.422).
Please let me know what could be the reason?

Kind regards,
Babak

Jason.Jonkman
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Location: Boulder, CO
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Re: Linearization issue using Fast V7.02

Postby Jason.Jonkman » Fri May 29, 2020 8:37 am

Dear Babak,

I'm not an expert on this SWRT model. I would try repeating this analysis at different TSR and pitch angle values to obtain the Cp surface.

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


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