Hi Justin,

I googled "hydroelectric generator synchronization" and after trying a
few of the hits, I came upon this little gem of a paper:

http://andrewferguson.net/wp-content/uploads/2008/04/boulder-hydro-paper.pd=
f

At least in this one example of a relatively small (20MW)
hydroelectric power station, they synchronize the generators by
varying the water flow rate through the turbine which then speeds up
or slows-down the generator. A fly-ball governor performs this
adjustment continuously.

I did also see that there are SOME cases where they do convert to DC
and then back to AC but those seem to be only for very small hydro
plants.

The converters which you mention do exist but the only really high
power use I know of for these units is in long-distance DC power
transmission. The advantages of using DC for such long distances is
reduced losses (due to capacitive coupling and EM radiation) and
relieving the need to synchronize phase (which is difficult to do
between two ends of a very long transmission line with a varying
load). I believe that these converters are made using large stacks of
semiconductor devices in series, carefully driven and matched to
ensure that they share the voltage equally. They are very expensive as
you suggest.

Sean


On Sun, May 8, 2011 at 12:56 AM, Justin Richards
<justin.richards@gmail.com> wrote:
> The question has come up regarding syncronising hyrdoelectric power stati=
ons.
>
> I can see how a diesel fired station is controlled but I cant see how
> you could control a hydro powered turbine.
>
> I guess they generate ac and variable freq convert to dc and convert to a=
c.'
>
>
> However, the converts would have to handle a huge amount of power and
> perhaps not possible to build such a device.
>
> Any ideas.
>
> The web didn't want to play.
>
> Cheers Justin
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