Rectifiers and electrical networks

[barendfaber]

Hi,

I have read on Wikipedia (http://en.wikipedia.org/wiki/Rectifier, under Rectifier output smoothing) "In extreme cases where many rectifiers are loaded onto a power distribution circuit, it may prove difficult for the power distribution authority to maintain a correctly shaped sinusoidal voltage curve.".

Does anyone know how many rectifiers you can add to an electric network while still maintaining a correctly shaped sinusoidal voltage curve? If I look at a wind farm, not all the turbines will spin at the same speed at the same time. How do they manage to put out a perfect curve?

 

[cjameshuff]

Does anyone know how many rectifiers you can add to an electric network while still maintaining a correctly shaped sinusoidal voltage curve?

When a large part of the power through the network leaves through the rectifiers. A more precise answer depends on your exact needs.

If I look at a wind farm, not all the turbines will spin at the same speed at the same time. How do they manage to put out a perfect curve?

They don't, but it doesn't matter what waveform they put out, because you're rectifying it. You're only interested in the output of the rectifier in that case, you're not using the input to power anything else. The rectified DC from all the turbines is added, filtered, and used to power an inverter that gives clean AC sine waves of the proper phases. You don't just plug a wind turbine into the grid.

 

[Enthalpy]

Every single wind turbine of significant size has an inverter. This has been the case for decades... too short for books and teachers to know it.

So: wind turbines produce AC power with the most perfect form.

 

[barendfaber]

Awesome! Thanks for the help. Not everything you read on the internet always makes sense! So regardless of the waveform, once rectified and put through an inverter, you will always get a perfect sinusoidal wave form? One last question, can you combine a 2.5 kW, 5 kW and 7.5 kW turbine to the same network, and once rectified and put through and inverter, you will still get the perfect wave?

 

[cjameshuff]

Awesome! Thanks for the help. Not everything you read on the internet always makes sense! So regardless of the waveform, once rectified and put through an inverter, you will always get a perfect sinusoidal wave form? One last question, can you combine a 2.5 kW, 5 kW and 7.5 kW turbine to the same network, and once rectified and put through and inverter, you will still get the perfect wave?

The purpose of such an inverter is to provide as close to such a waveform as is practical...you're basically asking if it will operate as designed. Hopefully the answer is yes, you've got a problem if it isn't.

 

[barendfaber]

Thanks, question answered!