Hi Dan,
Many thanks for your reply and insight. I do not quite understand why setting Fl_Mode to 1 gives issues (i.e. excessive pitching / instability, see 15MW towerbase pitching moment discrepancy - #9 by Salem.Okpokparoro ) for my model. Any take on this?
Regards
Salem
Hi Salem,
Fl_Mode of 1 uses the nacelle IMU translational acceleration (in the x-direction) to provide floating feedback. The gain Fl_Kp will translate this into a blade pitch signal.
Fl_Mode of 2 uses the rotational acceleration (about the y-axis) to determine the floating feedback pitch term. The same Fl_Kp gain is used to translate the rotational acceleration into a blade pitch signal.
So, if the same Fl_Kp is used in both modes, it will be too high when Fl_Mode is 1 by a factor of the tower height. Fl_Mode of 2 is the default and re-tuning using the ROSCO Toolbox should account for these factors if you choose to use Fl_Mode of 1.
Best, Dan
Hi Dan,
Thank you for your responses, much appreciated.
Regards
Salem
Dear all,
I have a doubt about the impact of floating feedback control strategy on the turbine performance. In particular I want to make a comparison between detuning and floating feedback for different peak shaving (PS): considering the 100% of the load, so No PS, the 90% of the load, and the 75% of the load.
I simulated the IEA 15MW coupled with VolturnUS, still water and steady wind.
From the step response it seems that there are important fluctuations close to the rated condition.
In a first moment I believed that was just a matter of transient, so maybe the turbine needed more time to reach the steady state. So I simulated just the conditions in which these fluctuations occur, so for wind speeds equal to 11m/s and 12m/s.
How it is visible from the picture it is not a matter of time, but the system looks like not damped / almost unstable. This phenomenon happens only for these 2 wind speeds, in particular when the peak shaving is not adopted or slightly adopted (100% and 90% of the load). Furthermore, adopting the detuning strategy these fluctuations, that are found in the thrust, power, platform pitch angle, are completely damped.
For this reason my conclusion is that the problem is the so called “platform pitch instability”, and the floating feedback is working properly in above rated but not in the range of wind speeds equal to 11m/s and 12m/s. Do you have any advice? Do you think I did something wrong in the simulation setup?
Thank you,
Kind regards,
Marco