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AC windturbines in Series to boost input voltage for inverter Answered

I just purchase a VAWT (Vertical Axis Wind Turbine) and an inverter. The wind turbine is rated at 24V AC, however, I see that the rated V AC is requiring quite a lot of wind to produce that Voltage. By mistake, I ordered a grid-tie inverter that starts at 22 V AC and so far I have not been able to reach the startup voltage of the inverter.

  • The inverter is rated 1000W and has AC input 3 phase. It can manage up to 60V AC input.
  • The VAWT is 600W 24 V AC 3 phase.

So here my questions:

Currently, I don't get any power at all, so how can I modify my setup to make this work. I have a few suggestings that I would love to get some feedback on:

Option 1: Buy a second VAWT + two rectifies that convert AC to DC. I should mention that the windmills will stand close to each other and receive more or less the same wind strength, so they should produce fairly the same amount of power. On the DC side, I would put them in series and then I would use a DC to AC converter to get the power back to AC current. The idea is that by doing this I would increase the voltage at least 22 V required by the inverter. I would expect some power loss and probably also voltage, using the rectifier and DC to AC converter.

Option 2: Same as option 1, but after the rectifier and connecting in series, buy a new inverter that can handle DC input within the range that the VAWT's produces. (W and Voltage)

Option 3: Buy a new Controller that charges a battery and connect an inverter to the battery to send power to the grid. Depended on the solution this solution might require a rectifier.

Any comment on these or maybe other options?

Discussions

0
Downunder35m
Downunder35m

6 weeks ago

I might be overthinking it here...
A wind generator should be able to produce electricity from very little windspeed all the way up to full speed.
Means either the following inverter or something between needs to be capable to make use of these variations.
I am almost certain there are purpose build inverters with a wide input range but:
If your generator, at low speed and with a rectifier only produces about 10V then you might still struggle.

Right now I see two options:
a) Rectify the output and use a step up converter to get to a fixed 24V.
b) Rectify and use an inverter rated for a few volts up to 24V.
Instead of a rectifier you also use a 3-phase transformer to get a higher AC and then rectify if required.

0
percbakk
percbakk

Reply 6 weeks ago

Thanks for valuable input. I struggle to find grid-tie inverters that go as low as I need. I do like the idea of a 3 phase transformer. The question is how these behave if I have variable voltage delivered. I assume these are pre-defined input-output. Let say they have 12V input and 24v output. What happens if the input is 8v or higher like 20v? What will be the output?

0
Downunder35m
Downunder35m

Reply 5 weeks ago

Did I miss the grid thingy? :(
That makes things complicated indeed.
With a max of 600W for the turbine and no three phase transformer available you could use three identical 600W transformers - or make them from salvaged microwaves.
But there might be a cheaper option if you can modify the turbine.
Can you upload some detailed images of it?
Generator, axle, blades and such?
Thinking of adding a small gearbox with load control to get more generator speed from low wind.

In case you don't want to mod it or add stuff to it, the transformer idea would go like this:
Find a bunch of old microwaves.
You need at least three but usually require about 8 until you ge three identical looking transformer cores.
A MOT - the microwave transformer, makes about 1000V from the usual 220V input.
Or if used on the turbine, from a max of 24V in about 110V would come out.
Now, there will be quite some losses if you use a MOT, so the realistic output would probably be in the range of 70-85V at 24V input.
You could use a 24V transformer and check what comes out of the MOT.
Carefully unwind the primary coil until yout get an output of just under 60V.

On the other hand I am also wondering about the output frequency of the turbine in relation to the wind speed.
I have to assume it is not a very expensive 50/60Hz syncronised turbine.
And in most cases these AC input inverters actually just rectify whatever comes in anyway before processing it.
It might really pay off to either get the schematics for the inverter or to open it up to check for a rectifier circuit right on the input.
In case this assumption is true you would actually have a really simple solution at hand:
With a rectifier on the input the 3 phase AC is changed to most likely just a single DC output.
This means you could feed a DC voltage right onto the output of the inverter's rectifier on the input.
Why would that make a difference you might wonder?
Firstly, your rcified turbine output will be a bit higher.
Secondly you could a simple diode/capacitor step up converter to basically double the DC output.
Means you generated 20V would become 40V for the DC input circuit of the inverter.
And since your inverter is good for 60V you could add a second diode/capacitor stage to actually triple the output voltage.
Downside is though that for 60W you are looking at quite expensive diodes and capacitors.
Upside is you won't have to worry about it for many years.

0
percbakk
percbakk

Reply 5 weeks ago

Not easy to find transformers or step-up converters either. I guess output could be 22 VAC or higher (up to 60)