Test18.fst - Power output

[Jasmina.Sandvoss]

Dear All,
for my bachelor thesis i am examining the difference in efficeny of eroded and new rotorblades.
For that firstly I simulated Test.18 (NREL 5 MW On Shore with DLL) without any modifications. The Power_windspeed graph shows a large decrease after 20 seconds. When i am simulating the pitchangle it shows an angle of zero degrees after 20 seconds. The windspeed doesen´t show any particularities.
Can you help me?
Thanks in advance and sorry for my english.
Jasmina

[Jason.Jonkman]

Dear Jasmina,

You haven't shown a plot of the wind speed, but I would guess that the wind speed has dropped at around 20 s, resulting in the controller transitioning from Region 3 (above rated) control to Region 2.5 (transition between below and above rated) control.

Best regards,

[Jasmina.Sandvoss]

Dear Mr Jonkman,
thank you for your answer! I´ll do the Plot of the windspeed in direction of the x-axis in the attachments.
The windspeed drops after 45 seconds again - but there is no change in the Power, shouldn´t it drop again?
The pitch angle of blade drops as well after 45 seconds. ( the plot is in the attachments as well - the green line shows the modified version of the eroded rotor blades!)

Best regards, Jasmina

[Jason.Jonkman]

Dear Jasmina,

The baseline controller for the NREL 5-MW turbine prevents the torque and power from dropping from Region 3 to 2.5 if the blade-pitch angle values are sizeable. So, sudden drops of wind speed below rated will not lead to a power drop unless the blade-pitch angle is already low. If the wind drops below rated long enough for the blade-pitch angle to drop, the torque and power will drop into Region 2.5. See the NREL 5-MW specifications report (http://www.nrel.gov/docs/fy09osti/38060.pdf) for more information on how the baseline controller functions.

Best regards,