Frequency of Wind-generated electricity

[Archduke]

Hey, I've made an observation about the turbines on a local wind farm. I've noticed that, in one instance, two turbines seem to be in sync; but a short time afterwards they get gradually more out of sync, and then become in sync again.

Surely, then, if we just consider these two turbines in isolation, the electricty produced will show a beat pattern, since the frequencies must be similar. Shouldn't the all the turbines be made to oscillate at the same frequency, so all the electricity is varying at 50Hz (I'm in the UK)? Or am I not understanding the way the electricity is produced by wind turbines?

Thanks in advance for your help!

 

[lalbatros]

frequency conversion

 

[berkeman]

The wind farms that I'm familiar with run the windmills in synch with the local grid. When generating power and connected to the grid, they are all in perfect sync. If they are not connected to the grid, then they just free-wheel. If the wind is not blowing real hard, the windmills are disconnected from the power grid to avoid sinking power instead of sourcing it. Could it be that you saw this during moderate wind conditions, when the windmills were not connected to the power grid?

I suppose it's possible that some windmill designs would use AC-DC-AC converters, but I'm not aware of any at this time. I believe that the straight AC connection to the grid is more efficient (at least in areas where there is often steady, strong wind).

 

[LURCH]

Ac-DC-AC used at a small house at this school:
http://www.energy-now.com/lakerschools/
Unfortunately, you can't see it in this image, the three big fellas (210 Kw) there are for powering the school. They run in synch with the grid like berkeman was talking about. But the school super is required to have his house on campus, so they hooked him up with a 50k and some PVC's. The 50 generates AC, rectifies it to DC, then converts it to AC 60.
If you check the link regularly, you can see the power being generated at different times. The school sometimes generates more than it's using. The house (which is not on the website) generates a LOT more than it uses.
I was there last Spring as a field trip.