speed control in low speed region

Wind & Water Controls
1

Hi, all
When I using the FAST simulation to simulate the torque control in low speed region. From the Fast user manual, I know that the control is
Tem=K_opt* omega_r
where K_opt is a constant, and the omega_r is the rotor speed. I have a question about the simulation result. Here is the wind speed (I using the constant wind speed (9m/s))

wind.jpg
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Here is the torque input and rotor speed
torque.jpg
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rotor.jpg
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Since I using the constant speed, in time interval [0 5]s, why the rotor speed is increasing. Is this normal?

2

Hi,

Torque should be related to rotor speed squared in your formula (see page 26 of manual), does this resolve the issue?

Paul

3

Dear Prof. Paul.Fleming
Thanks for your reply. From the figures, I can see that the optimal rotor speed is 17rpm when the wind speed is 9m/s. But when I set the initial rotor speed as 17 rpm, I think the rotor speed should stay around 17rmp. But when I simulate this, the rotor speed will also increase to a large value, and then back to the neighborhood of 17rpm. Why this phenomenon appear?
rotor.jpg

4

There could be a couple of reasons for the transient behavior. I mentioned earlier relating torque to the square of rotor speed, did you try this?

5

Dear Paul.Fleming.
Yes, the figures are obtained using the torque controller which the square of rotor speed. Thanks
Best wishs

6

In that case my guess is it is a start-up transient, usually I remove the first 30-60s from a simulation as being a period of time while the transients settle-out,

7

Thanks for your reply