Hello everybody,
I am simulating the 15MW turbine subjected to a steady-state wind of about 20 m/s.
I would like to capture the effect of the brake system and I set up the following parameters
---------------------- HIGH-SPEED SHAFT BRAKE ----------------------------------
1 HSSBrMode - HSS brake model {0: none, 1: simple, 3: user-defined from routine UserHSSBr, 4: user-defined from Simulink/Labview, 5: user-defined from Bladed-style DLL} (switch)
50 THSSBrDp - Time to initiate deployment of the HSS brake (s)
0.6 HSSBrDT - Time for HSS-brake to reach full deployment once initiated (sec) [used only when HSSBrMode=1]
20000 HSSBrTqF - Fully deployed HSS-brake torque (N-m)
I have also turned off the generator:
50 TimGenOf - Time to turn off the generator (s) [used only when GenTiStp=True]
My aim was to stop the rotor (RtSpeed= 0) and reduce the aerodynamic thrust (“RtAeroFxg”),
but regardless of the parameters I am using, I obtained the steady state rotor speed of 7.55 rpm.
Why so? What is the correct way to stop the rotor? Many thanks
Dear @Alessandro.Tombari,
Your input settings look OK to me. Is the HSS brake deployment having any effect? Is the generator degree of freedom enabled in ElastoDyn (GenDOF = True)?
Best regards,
Dear @Jason.Jonkman ,
thank you. So you are confirming I have some problems. Yes, the generator’s degree of freedom is active and I can read the generated power.
I am working on the IEA 15 MW offshore reference model monopile files, and I tried to stop the generator and activate the breaks at 50 sec. I tried several combinations,
------- OpenFAST INPUT FILE -------------------------------------------
IEA 15 MW offshore reference model monopile configuration
---------------------- SIMULATION CONTROL --------------------------------------
False Echo - Echo input data to <RootName>.ech (flag)
"FATAL" AbortLevel - Error level when simulation should abort (string) {"WARNING", "SEVERE", "FATAL"}
250.0 TMax - Total run time (s)
0.005 DT - Recommended module time step (s)
2 InterpOrder - Interpolation order for input/output time history (-) {1=linear, 2=quadratic}
0 NumCrctn - Number of correction iterations (-) {0=explicit calculation, i.e., no corrections}
99999.0 DT_UJac - Time between calls to get Jacobians (s)
1000000.0 UJacSclFact - Scaling factor used in Jacobians (-)
---------------------- FEATURE SWITCHES AND FLAGS ------------------------------
1 CompElast - Compute structural dynamics (switch) {1=ElastoDyn; 2=ElastoDyn + BeamDyn for blades}
1 CompInflow - Compute inflow wind velocities (switch) {0=still air; 1=InflowWind; 2=external from OpenFOAM}
2 CompAero - Compute aerodynamic loads (switch) {0=None; 1=AeroDyn v14; 2=AeroDyn v15}
1 CompServo - Compute control and electrical-drive dynamics (switch) {0=None; 1=ServoDyn}
0 CompHydro - Compute hydrodynamic loads (switch) {0=None; 1=HydroDyn}
1 CompSub - Compute sub-structural dynamics (switch) {0=None; 1=SubDyn; 2=External Platform MCKF}
0 CompMooring - Compute mooring system (switch) {0=None; 1=MAP++; 2=FEAMooring; 3=MoorDyn; 4=OrcaFlex}
0 CompIce - Compute ice loads (switch) {0=None; 1=IceFloe; 2=IceDyn}
0 MHK - MHK turbine type (switch) {0=Not an MHK turbine; 1=Fixed MHK turbine; 2=Floating MHK turbine}
and on top of the changes on the servodyn indicated earlier, I modified in Inflow:
20.0 HWindSpeed - Horizontal windspeed (m/s)
Having said that,
I noticed the results are different by deploying the brakes with or without shutting off the generator. I am checking both GenPWr and HSSBrTqC; everything makes sense.
I have also increased the brake torque (reading GenTrq , I understand it should be 20000 kN, not N), but I did not have really any effects except at the moment the brakes are activated for 0.6sec, the rotor speed goes down but catch up after 5-7 sec to reach the steady state of 7.55 rpm
The aerodynamic forces are very different when testing different values and/or combinations with the generator on/off and brakes.
Here in the figure is an example where I deployed the brakes at 66 sec
Anyway, thanks for confirming it should go to 0 rpm, I will attempt more tests
Just to add,
would it be possible the problem is generated by
5 VSContrl - Variable-speed control mode {0: none, 1: simple VS, 3: user-defined from routine UserVSCont, 4: user-defined from Simulink/Labview, 5: user-defined from Bladed-style DLL} (switch)
?
Dear @Alessandro.Tombari,
I’m not following everything you are saying. Are you disabling the generator torque, e.g., by setting GenTiSp = True with TimGenOf = 50 s (or so)?
FYI: HSSBrTqF is specified in Nm (not kNm) and is specified relative to the high-speed shaft.
Best regards,
Dear @Jason.Jonkman , sorry for confusing you
I tried 2 methods (separately or the 2 together):
Method 1 : Activate HSS
---------------------- HIGH-SPEED SHAFT BRAKE ----------------------------------
1 HSSBrMode - HSS brake model {0: none, 1: simple, 3: user-defined from routine UserHSSBr, 4: user-defined from Simulink/Labview, 5: user-defined from Bladed-style DLL} (switch)
50 THSSBrDp - Time to initiate deployment of the HSS brake (s)
0.6 HSSBrDT - Time for HSS-brake to reach full deployment once initiated (sec) [used only when HSSBrMode=1]
20000000 HSSBrTqF - Fully deployed HSS-brake torque (N-m)
Method 2: Shutting down the generator
---------------------- GENERATOR AND TORQUE CONTROL ----------------------------
5 VSContrl - Variable-speed control mode {0: none, 1: simple VS, 3: user-defined from routine UserVSCont, 4: user-defined from Simulink/Labview, 5: user-defined from Bladed-style DLL} (switch)
1 GenModel - Generator model {1: simple, 2: Thevenin, 3: user-defined from routine UserGen} (switch) [used only when VSContrl=0]
95.756 GenEff - Generator efficiency [ignored by the Thevenin and user-defined generator models] (%)
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]
50 TimGenOf - Time to turn off the generator (s) [used only when GenTiStp=True]
I am having some effects on the aerodynamic forces values but rotor speed trend is similar to the figure I attached in the previous post.
Dear @Alessandro.Tombari,
Are you applying both methods together? I would expect that you’d only want to deploy the HSS brake (method 1) after disabling the generator (method 2).
Moreover, you should also disable active pitch control at the same time using the override pitch maneuvers set to force the pitch of the blades to feather (90deg).
Best regards,
Thank you, @Jason.Jonkman ,
I got it now
it was mainly the pitch control, once the blades are feathered, the rotor speed drops to 0.
This solved my question
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