[RE-wrenches] Generator Controlled Mini Grid

[Chris Mason]

I am connecting a Kohler 12RES to my house, the roof has 3.1KW of PV
connected to a SB3000.
I thought we would have problems so we all knew to turn of the solar before
turning on the generator. One day, we forgot, and it all worked. Since that
I have left the solar on each time we ran the generator. As we are in a
small island, power outages are common.
The Kohler has a problem I cannot get to the bottom of and I'm going to
pull a Generac from inventory and install it, so I will find out if that
also works. My home and office is a test lab, I'll try anything there.


On Mon, Feb 11, 2013 at 8:44 AM, Drake <drake.chamberlin at redwoodalliance.org
> wrote:

>  Chris,
>
> It sounds like you are creating a generator supplied mini grid, if I
> understand correctly,  My reading is that your generator is creating the AC
> voltage, and the inverter is synchronizing with it, allowing power to be
> fed into the system from a PV source.
>
> This approach could represent a major innovation in solar industry.  I
> remember a decade or so ago when it was proposed, on this list, that
> battery based inverters could be backfed to charge batteries, and someone
> tried it.  It worked.  Today AC coupling is standard operating procedure.
>
> Up to that time, it was only understood that to connect an AC source to
> the output of a battery based inverter could damage it.  Maybe the next
> step is to AC couple to generator supplied sub panels and allow PV usage
> during power outages.
>
> What inverter and generator are you using?  How many Watts of PV are
> connected?
>
> Thank you,
>
> Drake
>
>
>
> At 02:04 PM 2/10/2013, you wrote:
>
> 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/
>
> Kevin
>
> -----Original Message-----
> From: re-wrenches-bounces at lists.re-wrenches.org
>  [ mailto:re-wrenches-bounces at 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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-- 
Chris Mason
President, Comet Systems Ltd
www.cometenergysystems.com
Cell: 264.235.5670
Skype: netconcepts
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