Generating electricity

[Ladaman]

A bit of a random question, but there seems to be a few people into electric on here, so here goes.

Is it possible to generate electricity into the grid at with a generator running at a variable speed? Or does the generator have to run at its syncronous speed, so a constant input speed?

If it is, then a "simple" explanation would be nice, raher than just a yes.

[Boyes]

Can i ask what you mean by variable speed, constantly changing?
So long as it the generator feeding into the grid has the same line voltage, frequency, phase angle, phase sequence and waveform it will be/will syncronise.

Not something I have looked into but on our turbine once it synchronises with the grid it stays connected, the revolution or duty on the turbine may vary slowly.

Any particular reason why you want to know this?

There are numerous gas powered generators feeding into the grid but the only gas ones the are cost effective are those used on landfill, gas powered stations are now not economically viable which is why quite a few have shutdown in the past few years, or shut down units.

[Ladaman]

Yeah, it's constantly changing.

It's for a small wind turbine. The larger ones (1 to 2.5MW) have variable pitch blades to allow for different wind speeds, so allowing a more or less constant speed. So a constant (ish) generator speed.

I'm now working on a much smaller turbine (75kW), and the input speed is varying from 17 to 50RPM and directly coupled to the generator, so I'm a bit puzzled.

Can an invertor deal with this?

[Tramp]

If you want to connect directly then no, uk's mains frequency is 50hz which is equivalent to 3000rpm on a single pole motor. The speed does alter but from around 2998 rpm up to 3002rpm if your generator isn't at this speed it will export power from the grid and run like a motor! I imagine if you want to feed into the grid you want do what solar power does, generate in dc then feed through an invertor onto the grid. Are you a member on difflock? Richard there has a wind turbine and knows all about getting them onto the grid, I think he has a large (for domestic) 200 odd kw turbine

[kiwizook]

there are many different ways of doing it. with any electricity generation, you need to have some sort of regulation. this could be through speed control, or a complicated regulation unit. generally these units produce power the same as the grid, so you can run your home of it. If you want to feed power into the grid, you need a synchronising unit, so the phase angle, frequency etc are the same as the grid. once you start doing this, your set up costs tend to go up a lot. I know there are more and more grid tied instalations being installed here in new zealand, and can be very economical in some cases. supply power when you have excess, draw power when you haven't got enough, so in essense you are using the grid as a storage facility. if you want more information on this, I'll do some more research, as I know a few people that deal with this stuff