[skippy]

I realise this doesn't really belong here but.... It's the closest thing I could find. Just wondering if someone with electrical experience can help me out here with a bit of knowledge. I’m researching tied-to-grid 3 phase power generation. Let’s say we have a source of motive power, either a steam powered turbine geared down to the correct revolutions or a diesel engine and from this we want to drive a generator. All theoretical in this case and let’s say we are talking in the range of 0.5Mw power generation. The part that intrigues me is the electricity generation.

I have a friend who told me about a set up in an engine testing laboratory whereby a ~ 400hp diesel engine is connected to a dc generator and from there the dc output passes via an inverter which converts the dc into 400v 3phase ac which is fed back into the grid. He explained to me that it has to be done this way because although 400v 3phase ac generators are available, the problem is matching the frequency both in terms of frequency count and timing.

Yesterday I read this very interesting article http://www.windpower.org/en/tour/wtrb/async.htm from the Danish Wind Industry Association about Asynchronous (Induction) Generators. One reason for choosing this type of generator is that it is very reliable, and tends to be comparatively inexpensive. The generator also has some mechanical properties which are useful for wind turbines. (Generator slip, and a certain overload capability)..... ......... a 4-pole generator will run idle at 1500 rpm if it is attached to a grid with a 50 Hz current. If the generator is producing at its maximum power, it will be running at 1515 rpm...... It seems that as this type of generator is excited by the grid therefore frequency (count and sychronization) are already taken care of. ......... the turbine will generate alternating current at exactly the variable frequency applied to the stator.
Anyone have experience or knowledge in this area? (Not of windturbines but of tied-to-grid 3 phase power generation via turbine or diesel engine, etc.) Looking for general knowledge at the moment and maybe later on some paid consulting work.
Skippy
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[Geof]

What are you planning Skippy, going into electricity generation as a sideline using old cooking oil to run a diesel?

Thank you for the Danish link. I have wondered whether anyone was going to clue into asynchronous generation. Anyone who runs a CNC machine or has a VFD with regenerative braking is familiar with asynchronous generators (although they may not be aware of it); that is what the motor is acting as when the controller brings it to a halt and all the rotational kinetic energy is dumped across the regen resistors and dissipated as heat.