Hi all,
I would like to ask that if the the rotor can be stopped at the specific time during the simulation. For example, if the full time period of the simulation is 1000s, can I stop the rotor at 500s?
Best regards
Yajun
Dear Yajun,
Yes, there are a number of methods available in the ServoDyn module of FAST / OpenFAST to trigger a turbine shutdown event including pitching the blades, disabling the generator, applying a high-speed shaft brake, yawing the turbine, etc.
Best regards,
Dear Jason,
Thank you very much for you reply.
So if I would apply the pitch control to stop the rotor by the specific time, can I just use Pitch Controller block in the Simulink interface.
Best regards,
Yajun
Dear Yajun.Ren,
Yes, you can use Simulink for that.
The override pitch maneuver settings in the ServoDyn input file (TPitManS(k), PitManRat(k), BlPitchF(k) for k={1,2,3}) are another way to stop the rotor via simple pitch ramps.
Best regards,
Dear Jason,
Thank you for your reply. Yes I think the modification of ServoDyn input file is a much easier way. As my understand, to stop the blade rotation from 1000s, I changed the Pitch Control sector as follow:
---------------------- PITCH CONTROL -------------------------------------------
5 PCMode - Pitch control mode {0: none, 3: user-defined from routine PitchCntrl, 4: user-defined from Simulink/Labview, 5: user-defined from Bladed-style DLL} (switch)
0 TPCOn - Time to enable active pitch control (s) [unused when PCMode=0]
1000.0 TPitManS(1) - Time to start override pitch maneuver for blade 1 and end standard pitch control (s)
1000.0 TPitManS(2) - Time to start override pitch maneuver for blade 2 and end standard pitch control (s)
1000.0 TPitManS(3) - Time to start override pitch maneuver for blade 3 and end standard pitch control (s) [unused for 2 blades]
2 PitManRat(1) - Pitch rate at which override pitch maneuver heads toward final pitch angle for blade 1 (deg/s)
2 PitManRat(2) - Pitch rate at which override pitch maneuver heads toward final pitch angle for blade 2 (deg/s)
2 PitManRat(3) - Pitch rate at which override pitch maneuver heads toward final pitch angle for blade 3 (deg/s) [unused for 2 blades]
90 BlPitchF(1) - Blade 1 final pitch for pitch maneuvers (degrees)
90 BlPitchF(2) - Blade 2 final pitch for pitch maneuvers (degrees)
90 BlPitchF(3) - Blade 3 final pitch for pitch maneuvers (degrees) [unused for 2 blades]
Could you please let me know if I am correct or not.
Best regards,
Yajun
Yes, those look like reasonable settings to me.
Best regards,
Dear Jason,
I have a further question regarding to this problem. When I ran the simulation with the above setting, I can see the blade was pitched to 90 degree from the time that the turbine was supposed to be parked and the aerodynamic loading was obviously reduced. However, the RotSpeed was unchanged (12.1rpm as default), does this mean that the rotor keeps rotating during the simulation?
Additionally, I found that the mean RotTorq reduces from 8407 kNm (rotor rotates) to -44255 kNm after the override control, however, if I simulate the turbine to be parked from the start of the simulation by setting:
BldPitch = 90˚
RotSpeed = 0
PCMode = 0
WakeMod = 0
The mean RotTorq is -173kNm. Does that show the rotor is likely to rotate towards the inverse direction?
Best regards,
Yajun
Dear Yajun,
Regarding your first question, I would guess there is something incorrect in your torque-control setting (normally, I’d expect that you’d disable generator torque when feathering the blades, i.e., GenTiStp = True, TimGenOf = TPitManS) or you’ve disabled the generator degree of freedom (GenDOF) in ElastoDyn.
I’m not sure I understand your second question, but again, I’d expect that you’d zero the generator torque when idling the rotor.
Best regards,
Dear Jason,
Thanks for your reply.
For the first question, here is the setting of the torque control:
VSContrl = 5, GenModel = 2, GenTiStr = True, GenTiStp = True, TimGenOn = 1000 (TPitManS)
I can’t find anything wrong with this, could you suggest if there is any other setting I should notice?
For the second question, what I mean is that the aerodynamic load of the parked turbine is different between the two control strategies (directly setting rotor speed to 0 in ElastoDyn and override pitch control in ServoDyn).
Best regards,
Yajun
Dear Yajun,
For your torque control settings, did you mean that you set TimGenOf = 1000 (instead of TImGenOn = 1000)? TimGenOf will disable the torque controller, resulting in a generator torque of zero.
Regarding your second question, I would guess the difference in torque is related to the difference in rotor speed between the two simulations.
Again, you should ensure that the generator torque is zero and then I would expect the same mean torque (zero) for the same (likely zero) mean rotor speed.
Best regards,
Sorry I actually set TimGenOn = 0 and TimGenOf = 1000. I wanted to stop the turbine from 1000s.
In that case, I would expect the rotor speed and torque to tends toward zero after the shut down.
Best regards,
Dear Jason,
I did set the input file using the above settings and the output shows that the rotor speed is unchanged after the shut down. The generator torque reduces to 0 after 1000s which looks correct. In this situation I think the generator stops to produce power, but the blades are still rotating. But what I expect is to stop the rotor as well.
Best regards
Yajun
Dear Yajun,
It will take some time after feathering the blades to slow the rotor down to standstill.
Best regards,
Dear Jason,
The total simulation is 8000s, and the rotor speed is unchanged until the end of the simulation.
Best regards,
Yajun
Dear Yajun,
Then I would guess you’ve disabled the generator degree of freedom in ElastoDyn (GenDOF), which prevents the generator-side of the drivetrain to changing speed, regardless of the applied torques. You should set GenDOF = True to allow the drivetrain to react to the changing torques.
Best regards,
Dear Jason,
That works. Thank you very much for your kind help.
Best regards,
Yajun
Dear Jason,
I have one more question regarding PitManRat. For 5MW turbine, the maximum blade pitch control rate is 8 degree/s, is this limitation also applicable for PitManRat for override maneuver?
Best regards,
Yajun
Yes.
Best regards,