Problem about baseline controller of NREL 5MW wind turbine

Wind & Water Controls
1

Hi all,

I am trying to design baseline torque controller and pitch controller as the description of Chapter 7.2 and 7.3 of this Pdf " [url]http://www.nrel.gov/docs/fy09osti/38060.pdf[/url]" .Now I have some confusion about the baseline torque controller. The curve between generator torque and generator speed is like the blue one in Figure 1

Figure 1.jpg
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. I set the wind speed is a constant 18m/s and results are obtained like in Figure 2. You can see the generator power and torque both have some fluctuation at near 11s -16s which is caused by the little fluctuation of the rotor speed. I found this is because when the generator speed vibrates lightly between region 2 1/2 and region 3, the output torque and power have a big fluctuation showed in Figure 2
Figure 2.jpg
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. I think the fluctuation of generator power like in Figure 2 is caused by the region 2 1/2. What’s the purpose of the region 2 1/2?

Because the above problem, when I set the wind speed as changing, the generator power fluctuated too much like in Figure 3

Figure 3.jpg
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. Can anyone help me to explain or solve this problem? It drives me crazy. Thank you so much!

All the best.

Yanhua

2

Dear Yanhua,

Region 2 1/2 exists to limit tip speed (and hence noise emissions) at rated power i.e. without it, rated power would not be reached until a much higher speed.

To eliminate the drastic drops of torque and power in Region 3, the NREL 5-MW baseline controller places uses a conditional statement so that the torque is computed as if it were in Region 3–regardless of the generator speed–whenever the blade-pitch-angle command exceeds 1 deg, as explained in Section 7.2 of the NREL 5-MW specifications report that you referenced.

I hope that helps.

Best regards,