Dear FAST users,
I am trying to get more insight on the yaw system of the 5Mw reference onshore wind turbine.
In order to do that, i downloaded the latest FAST V7 version (Aerodyn 13 included).
In order to set the simulations, I made the following assumptions:
1.- Turbine is UpWind, and rotates clockwise when looking from upwind to downwind.
Although this is very common for UpWind turbines, it is not so clear to me when reading aerodyn and FAST manuals.
2.- Azimut angle increases when turbine rotates clockwise.
3.- Yaw reference coordinate system is defined by vectors d1, d2 and d3
d1 (x pointing downwind = IEC x)
d3 (y pointing left when looking from upwind to downwind = -IEC y)
d2 (z pointing upwards = IEC z)
4.- A positive yaw angle takes place when rotating FROM d1 TO d3.
That is: clockwise is positive when looking the turbine from above.
5.- Variable HorWndDir (FAST) is positive when the wind rotates FROM d1 TO d3.
That is: clockwise when looking the turbine from above.
6.- Variable YawBrMzn is the Action Torque over the yaw bearing according to d2 axis.
That is: Negative when looking the turbine from above.
Next figures tryes to point out these assumptions graphically and the simulations I have tried to set up
in FAST 7.02.
YawBrMzn behaves as I expected in all cases when setting yawdof to false, meaning:
1.- YawBrMzn is negative due to tilt.
2.- YawBrMzn decreases when HorWndDir goes negative.
3.- YawBrMzn decreases when YawPos goes positive.
So far, all is ok (unless one of the former assumpions were wrong).
Now, when I switch on the yaw control logic, my aim is to evaluate the torque to be supplied by the actuator in order to perform a certain yaw manoeubre. Next figure show the results for variable YawBrMzn in the cases Yawdof = true and false in a yaw manoeuvre.
The first thing I dont understand is that, when setting yawdof = on and YawSpr and YawDamp = 0, the turbine is stable. That is: it achieves yawerror = o for all initial HorWndDir I set as initial condition.
Could you please explain how the phisics work in this case?
The most probable is that I miss something …
Thank you in advance.