# Test18.fst - Power output

**URL:** <https://forums.nlr.gov/t/test18-fst-power-output/2141>\
**Category:** Testing\
**Created:** [October 22, 2019, 8:29am UTC](https://forums.nlr.gov/t/test18-fst-power-output/2141 "2019-10-22T08:29:00Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Jasmina.Sandvoss](https://avatars.discourse-cdn.com/v4/letter/j/3be4f8/32.png) [@Jasmina.Sandvoss](https://forums.nlr.gov/u/Jasmina.Sandvoss)\
**Post date:** [October 22, 2019, 8:29am UTC](https://forums.nlr.gov/t/test18-fst-power-output/2141/1 "2019-10-22T08:29:00Z")

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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  
[Test18.pdf](https://forums.nlr.gov/uploads/short-url/tXaRADk35csSzDpJPazdYZ1eG6F.pdf) (65.2 KB)

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**Author:** ![Jason.Jonkman](https://dub1.discourse-cdn.com/nrel/user_avatar/forums.nlr.gov/jason.jonkman/32/3086_2.png) [@Jason.Jonkman](https://forums.nlr.gov/u/Jason.Jonkman)\
**Post date:** [October 23, 2019, 7:43am UTC](https://forums.nlr.gov/t/test18-fst-power-output/2141/2 "2019-10-23T07:43:12Z")

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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,

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**Author:** ![Jasmina.Sandvoss](https://avatars.discourse-cdn.com/v4/letter/j/3be4f8/32.png) [@Jasmina.Sandvoss](https://forums.nlr.gov/u/Jasmina.Sandvoss)\
**Post date:** [October 23, 2019, 12:11pm UTC](https://forums.nlr.gov/t/test18-fst-power-output/2141/3 "2019-10-23T12:11:46Z")

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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  
[WindxüberderZeit.pdf](https://forums.nlr.gov/uploads/short-url/ugcVHXAeuBaVu7W3irZWdkJGYSS.pdf) (73.1 KB)

 ![Pitch Angle 1.jpg](https://europe1.discourse-cdn.com/nrel/original/2X/2/22760f02ddb5fcca1b21e66f07d9523e18f927f0.jpeg)

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<div class="post-metadata">

**Author:** ![Jason.Jonkman](https://dub1.discourse-cdn.com/nrel/user_avatar/forums.nlr.gov/jason.jonkman/32/3086_2.png) [@Jason.Jonkman](https://forums.nlr.gov/u/Jason.Jonkman)\
**Post date:** [October 23, 2019, 12:22pm UTC](https://forums.nlr.gov/t/test18-fst-power-output/2141/4 "2019-10-23T12:22:22Z")

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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 ([nrel.gov/docs/fy09osti/38060.pdf](http://www.nrel.gov/docs/fy09osti/38060.pdf)) for more information on how the baseline controller functions.

Best regards,