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Author Topic: Two turbines with one grid tie inverter?  (Read 3158 times)
wigmyster
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« on: February 12, 2009, 11:55:41 AM »

Hi
I am guessing this is not possible due to sync problems? I am just thinking that it seems at low wind speed two 2kw turbines can produce more power & are much cheaper & safer. I am thinking of the aurora 6.5 with its interface.

Thanks
Nath
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guydewdney
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« Reply #1 on: February 12, 2009, 01:16:36 PM »

I have exactly the setup you describe. I have two miniwind type 2200w heads - both running off the same shaft via belt drives. Aurora 3.8Kw inverter.

long story short - it doesnt work. They fight each other.

Get one big one - and a smaller backup one?
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7.2kW Waterwheel and 9.8kW PV
Ivan
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« Reply #2 on: February 12, 2009, 04:08:56 PM »

Guy, you're trying to couple them together on the AC side, aren't you? Have you tried coupling the DC? It should work ok in your setup, I would have thought, as you have constant power input.

I'm not sure a DC-coupled turbine pair would work well if it was wind-powered, as one might be producing a higher voltage than the other, and I'm not sure the MPPT algorithm would be able to cope with that.
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guydewdney
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« Reply #3 on: February 12, 2009, 06:54:03 PM »

No - it failed as a DC coupled system, and thats why I looked at the AC couplign idea - which failed miserabley.


Basically - wigmyster - each generator is very very slightly different, and if the aurora is prograed to pull, say, 1kw at 200 volts - it will do that. BUT as each egn is differnt - one is making 501 watts, the other 499 watts - one will  get hotter than the other. This happens slowly, and in your case one will stall the other will try to provide all 1kw - which wont happen. Sorry. This idea cost me a fortune - I hope that my mistake will help you.
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wigmyster
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« Reply #4 on: February 12, 2009, 08:12:42 PM »

Hi
Thanks for that. I see what you mean.
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billi
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« Reply #5 on: February 12, 2009, 08:54:33 PM »

So basically the  well developed grid tie  technology fails  Huh  , sounds strange to me , cause thats the big idea behind it to supply a technology for a wide market , cause gridtied  Roll Eyes

But one gridtie inverter for each turbine should work or ?

Be it AC or DC  two or more Generators are no problem to connect to an offgrid idea  Roll Eyes  And those ideas have not the big companies in their Back for developing


Must be the Black Hole called Battery to cope with that

Billi
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
guydewdney
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« Reply #6 on: February 12, 2009, 09:01:14 PM »

No - just that 1 gen-> 1 inverter Yes. 2 gen -> 1 inverter = No

No batteries here my Germanic friend....
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billi
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« Reply #7 on: February 12, 2009, 09:18:40 PM »

Quote
No batteries here my Germanic friend....

fair play and respect    Grin   perhaps i open my mind one day (but hope i will not get compromised )  Feed in tariffs in England and Ireland are  not good enough to say Yes thats it   for me  Grin

So in my case 5 generators in to one Inverter  Grin

Billi
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
Ivan
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« Reply #8 on: February 13, 2009, 01:19:27 AM »

The SMA grid-tie inverters allow you to feed several 'strings' into the grid-tie inverter (3 on the ones I've got) and each string has mppt applied separately. I've only ever studied this for PV, but can't see why it wouldn't work with their wind or hydro options - they're only different curve-fit algorithms, after all.

I haven't used the Aurora yet, so don't know if there's a fiddle available. I'm speaking to the Aurora guys in the near future, so I'll bring it up with them to see if they've got a solution.
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guydewdney
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« Reply #9 on: February 13, 2009, 08:38:26 AM »

The aurora software doesnt allow for the 'wind' version (which is what I have) to have two differnt mppt curves - but the solar version (different sticker) does - aparantly theres not enough RAM to take any more code.

It gets upset if you feed the two inputs separately with differnt voltages (beyond a certain amount) - but in a version of my lashed up system, I had the two gennys runnign separately on the two inputs - worked fine, until one belt loosened slightly, and it threw a wobbly fit Wink
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wigmyster
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« Reply #10 on: February 13, 2009, 09:49:13 AM »

The Aurora guys do have a new product that I have seen somewhere that will take many inputs but it was very expensive. Think its called the pvi-6000 something.
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Ivan
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« Reply #11 on: February 17, 2009, 12:28:02 AM »

I'll discuss it with them when I speak to their UK guys. Last week's meeting was cancelled due to snow. SMA have a nifty option 'constant voltage' where the grid-tie inverter tries to maintain a constant voltage by varying the load. Couldn't really be simpler and ideal for water-power (also works quite well for wind in some situations). Wouldn't take a lot of code, either.
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