On generator power drop and pitch controller

Hello everyone,

I am doing my master thesis and have come across a problem that I lack the knowledge to answer. I aim to simulate near-realistic wind fields and their effects on a wind turbine. I use a site-specific spectral model[1] to create a wind field, then using .bts format analyze the resulting loads on FASTv8. Here, we have come across an interesting effect and hypothesize the following.
We notice drop in the generator power and torque for wind speeds above rated (please refer the plot provided), we were wondering if this behavior is due to switching of the controller in the transition between the pitch-controller and the torque-controller?

Your opinion on this would be highly appreciated.

Thank you
Adithya Vemuri
MSc. Sustainable energy technology - Wind energy
TU Delft

[1] researchgate.net/publicatio … dary_Layer

Dear Aditya,

Yes, these dips in torque and power are associated with dips in the wind speed and result from the Region 3 to Region 2 transition of the controller.

Presumably you are modeling the NREL 5-MW turbine. The baseline controller of this turbine is described in the NREL 5-MW specifications report: nrel.gov/docs/fy09osti/38060.pdf.

Best regards,

Dear Dr. Jonkman,

Thank you for the quick reply!
Yes, I forgot to mention, I am using NREL 5MW wind turbine.

Thank you