I'm doing some experiments on a wind turbine in my spare time. At the moment, my system runs well and I can measure good output values from my generator. For example:

  • 38V @18Hz at 30 RPM
  • 97V @37Hz at 60 RPM
  • 220V @72Hz at 120 RPM
  • 343V @108Hz at 180 RPM
  • 466V @144Hz at 240 RPM

The maximum measured current output is 18A.

Now, I would like to use an inverter in order to obtain a three phase output. The problem is that I tried to search on the net and I only found inverters for solar panels which require a stable voltage input (my rectified voltage output keeps changing depending on the RPMs). My system has a variable voltage output depending on the RPMs (obviously) and the frequency changes when the RPMs increase, too.

What is the most suitable solution to obtain a stable voltage output regardless the input RPMs? Is there a commercial inverter which accepts variable inputs?

Thank you!

You first have to rectify your variable frequency AC to DC, then use an inverter which turns DC into the AC of the grid. There are inverters in the market which include the rectifier.

There is an alternative solution which involves a rotor-fed asynchronous machine. The idea is to feed the difference AC frequency to the rotor so the stator frequency keeps being in phase with the grid. That way, the inverter doesn't have to pass all the power the turbine delivers. It was somewhat popular 20 years ago, when big inverters had been incredibly expensive.

  • Yes, I already rectify the output of my generator, but the problem is that I can't find a 8-10kW inverter which is able to accept variable voltage as input. Even if I rectify the voltage, it keep changing depending on the RPMs. Can you suggest me a good inverter for my case? – Marcus Barnet Dec 5 at 9:40
  • 1
    The voltage spread of commercial wind turbine inverters seems to be around 2.5. So, a 500V inverter accepts down to 200V on its input. You have to specifically look for wind turbine inverter, they are meant to deal with both problems. – Janka Dec 5 at 9:49
  • I already tried to look for "wind turbine inverter" but I only found scientific papers or small companies which never reply to my messages (may be they are not running anymore). I am really not able to find a commercial wind turbine inverter. – Marcus Barnet Dec 5 at 10:14
  • I was also considering to use a constant speed drive (or gearbox) like the ones used for the airplanes but I'm not able to find any of these devices for commercial use. – Marcus Barnet Dec 5 at 11:04
  • 1
    You are in the 10kVA range. That's a medium-sized windmill with about 100m² cross section to wind. Sure about that? ABB has some offerings for such generators. – Janka Dec 5 at 12:54

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