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Old 04-04-2013, 08:31 AM
1,278 posts, read 1,057,316 times
Reputation: 836


Originally Posted by my54ford View Post
MMMMM as I stand here in the middle of the 3 yr old wind farm I manage O&M on, I don't see a single VFD controlling generator speed.....And as I turn and look at the 26mw Srice plant I have under construction I see govoners controlling fuel input that controls engine speed...
Let me help you out a bit...
A quick review of VFD operation would remind you the VFD's control FREQUENCY of electricity going INTO an induction motor thus controlling motor speed.
How Does a VFD Work? | eHow.com

What is a Variable Frequency Drive (VFD)? How Does a VFD Work?

Another review of synchronous vs asynchronous generatoror operation (Real generator vs wind trubine)

A synchronous generator does not have a time varying magnetic field. It will not produce a current into the rotor coil. That is why a CC current supply is needed.

The rotor needs to have a magnetic field either by an induced current or a current supply in order to use the power of attraction and repulsion to turn.

An asynchronous generator is really only an induction motor used as a generator. It will only supply 1/3 of a facilities power requirements because it still needs to be tied to the grid for excitation currents. The only time it will produce power is when the frequency of the rotor is greater than the frequency of the grid. This is what makes it asynchronous (out of synch). This is also the reason it can't be used to produce 100% of a facilities power generation.

The synchrounous generator still will need an excitation current as well. It can be from a source independent of the grid. In fact, once the generator is running, it can produce it's own excitation.
Yahoo! Video Detail for GenTec Home Generator: How Does It Work?

AC Motors and Generators

How a Generator Works
I stand corrected. I cant believe they still use the gearbox or CVT and blade pitch to achieve peak efficiency according to wind speed.

I worked on a VFD for torque control and speed control of a teetered rotor wind turbine in the 90's. We used a space vector control to vary the sychronous speed of the motor, and yes we had to use a voltage source inverter to standardize the power output and connect to the grid. I suppose that the cost is still too high for that type of wind turbine.
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Old 04-04-2013, 08:50 AM
Location: Chicagoland
1,789 posts, read 1,629,010 times
Reputation: 1599
Originally Posted by MissingAll4Seasons View Post
The scenario I see more likely to happen at 100% RE adoption, being somewhat cynical, is that grid-tie will be mandatory (at your expense) and net metering will be mandatory (at your expense) and you will be charged for the power you draw off the system but not paid for the power you feed into the system. You can be sure that the utility companies (and the government backers) are not going to allow RE to interfere with their profits.
Thanks, that ties in with my OP. For whatever reason, most replies skirted the original question, though many had good ancillary information.
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