[RE-wrenches] Generator Controlled Mini Grid

[Chris Mason]

I have a generator and PV system that just works together, despite all the
dire predictions that it won't. from my experience of PV and generators (I
am also a generator tech), the biggest issue is the AVR board and how it
responds to back fed voltage, and the generator controller's over voltage
settings.
I think that it would probably on only require a reprogrammed inverter to
make this work as follows.
The AVR produces excitation voltage to vary the strength of the rotor field
and therefore the induced voltage in the stator. When the PV system back
feeds the generator, the excitation level is reduced to control the
voltage. When there is no load, the inverter keeps raising the voltage to
attempt to push the current to the grid and at some point the generator
trips out on overvoltage.

 If the inverter was programmed to reduce the production of power in
response to the rise in voltage, it would sync pretty nicely with the
generator. However, this would likely violate the IEEE parameters for a
grid tied inverter. SMA has off-grid mode, I suspect that is the best
solution.

In a Sunny Island system, as I understand it, the Sunny Island caries the
frequency to communicate to the inverter to reduce the current output. That
avoid the problem of the inverter raising the voltage.




On Sun, Feb 10, 2013 at 2:45 PM, Drake <drake.chamberlin at redwoodalliance.org
> wrote:

> Hi Kevin,
>
> Thanks for the Eigg video.  What a great place.
>
> I didn't see evidence of any AC coupling of inverter produced AC to a
> generator produced mini grid.  I understand this is being done in a
> homebrew manner by some.
>
> The current wisdom on the issue is that the less the PV contribution to
> the generator supplied grid is, the easier.  It would seem that if a grid
> tie inverter output could be regulated, using Sunny Island type controls,
> it should be possible to have a small inverter generator create a mini grid
> that could be fed by PV.
>
> A system featuring this type of technology was linked in a posting on this
> list some years ago, The link seems dead now.  In that case a large
> generator was feeding a number of houses, and PV was fed into the system.
>
> The reason for this interest is that battery backup systems are much more
> expensive than generators.  We need to find a way to utilize PV arrays
> during outages without the expense of battery backup systems.
>
> Drake
>
>
>
> At 07:42 PM 2/8/2013, you wrote:
>
>> Hi Drake,
>>
>> SMA has very good solutions for this. Does this out of the box without a
>> bunch of custom control systems. I have put a few systems in like this, but
>> the renewables not yet online (generator / battery now). If you google Isle
>> of Eig you will find some info on what they have done there.
>> http://islandsgoinggreen.org/**about/eigg-electric/<http://islandsgoinggreen.org/about/eigg-electric/>
>>
>> Kevin
>>
>> -----Original Message-----
>> From: re-wrenches-bounces at lists.re-**wrenches.org<re-wrenches-bounces at lists.re-wrenches.org>
>> [mailto:re-wrenches-bounces@**lists.re-wrenches.org<re-wrenches-bounces at lists.re-wrenches.org>]On
>> Behalf Of Drake
>> Sent: February 8, 2013 6:41 AM
>> To: RE-wrenches
>> Subject: [RE-wrenches] Generator Controlled Mini Grid
>>
>>
>> A potential customer is interested in a mini grid, set up by a
>> generator, to connect his array to.
>>
>> Some years back, on this list, an article was linked about a
>> community with a central generator that had PV input to the generator
>> supplied, local grid, using electronic controls.
>>
>> Has any progress been made in this technology?  Does anyone have a
>> link to the electronic control equipment or any other relevant
>> information?
>>
>> Thanks,
>>
>> Drake
>>
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-- 
Chris Mason
President, Comet Systems Ltd
www.cometenergysystems.com
Cell: 264.235.5670
Skype: netconcepts
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