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Anonymous Poster

Wind power

06/18/2010 10:46 AM

How does a wind power generates constant frequency electric power they all rotates in different speed in different time right.How do they synchronse each other in all means?

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Power-User
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#1

Re: Wind power

06/18/2010 10:57 AM

I think ac generated is stored as dc and convert it to ac. i dont have much clear idea hope that helps Hithu

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#2

Re: Wind power

06/18/2010 12:15 PM

There are many different types of alternators or generators used with wind turbines. DC generators will convert the wind motion to DC, then an inverter converts it to AC and synchronizes to the line (if grid connected). Induction Generators inherently synch to the line and the grid itself provides a modicum of speed control in that if the turbine attempts to go faster than the line frequency, a negative torque is produced to keep it in check (vastly over simplified). Think of it this way: if you have hundreds of megawatts of hydro generators producing power, do you think that one little wind turbine is even going to affect it noticeably? But some speed control of the turbine is still necessary to avoid having the induction generator overload trying to stay synched like that, so it is done on the turbine itself by rotating the blade pitch, mechanical brakes, changing the angle of attack etc. etc. Synchronous Alternators also will inherently synch with the line in the same way, but also allow off-grid operation.

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#3

Re: Wind power

06/18/2010 2:20 PM

Most of the wind turbine generator manufacturers use a standard induction (asynchronous) generator to produce something like 690VAC, although some (e.g. Clipper) use synchronous gens and inverters. The speed of the prime mover (turbine) input to the gen is controlled via the gearbox and the blade pitch, which adjust the generator rotor speed to the desired RPM. Generation is usually not started until speed reaches some minimum turbine RPM, and cut off if wind speed gets too high.

Synchronization of each generator to the wind farm collector system and the grid has been discussed in other threads on this forum. There would typically be an autosynchronizing function associated with the speed controller (it's all digitally controlled these days) that adjusts speed / voltage / frequency to sync with the collector system at the turbine's breaker. Once synced, the generator will follow the system frequency. Protection circuitry will disconnect the gen from the system if it gets outside of reasonable bounds.

The above is mainly in relation to large commercial generation units (500kW - 2.5MW), can't speak for smaller units built for residential / individual use.

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#4

Re: Wind power

06/22/2010 4:38 PM

Having commisioned the HV electrical side of 7 wind farms I think I almost understand.

The simple means would be an inverter linked to the grid frequency but that would be 2.5MVA or offshore 3.5MVA so thats not reasonable. My possibly flawed understanding is that the turbine is supplied with power from the 33kV system. This is transformed to 690 volts and feeds the electronic gubbins. Non english people... gubbins is stuff we dont understand!!! The alternator is then provided with a field winding that is not static. It is provided by an inverter. The speed of rotation of the field is constantly adjusted so that the speed of the rotor relative to the field always is the same as the frequency of the grid.

Thats how I have blagged my way through running many training courses for management of the electrical network outside of the turbine so if I am wrong please put me correct.

I always thought it was inverter driven but thats silly as the losses from a 2.5 MVA inverter would be far too high.

Pitch control would not work as its too slow to respond to wind speed

Look forward to comments

Kevin

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