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
<<mailto:drake.chamber...@redwoodalliance.org>drake.chamber...@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:
<mailto:re-wrenches-boun...@lists.re-wrenches.org>re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@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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