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In off-grid mode the Sunny Island uses frequency shift power control to
reduce the output of the Sunny Boy inverters and thereby regulate the
battery voltage. At some frequency shift (+1, or 2, or 3 Hz, I'm not
sure) the output of the SB is reduced by 100%. It's proportional so
that 1/2 as much frequency shift gives a 50% reduction in the SB
output. To keep clocks accurate, the Sunny Island later shifts the
frequency a negative amount, but the SB inverters ignore that. For a
grid backup system, a RS-485 cable is required so the Sunny Island can
activate (or deactivate) the frequency shift power control capability
of the SB.<br>
<br>
You need to stack two SI inverters to get 240-vac, but that will allow
you to have a 10-kW of grid backup power with up to 12-kW of solar. If
you need more, you can stack four of SI inverters.<br>
<br>
Kent Osterberg<br>
Blue Mountain Solar, Inc.<br>
<br>
<br>
Glenn Burt wrote:
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<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Our
installations of Sunny Islands (SI) with Sunny Boys (SB)
have always used the recommended RS-485 communications between all
units
involved. This with reprogramming the SB’s to be able to switch to
off-grid mode per the SI instructions allows a more integrated system.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">We
have had problems with the OB PSX-240 and stepping up the 120
to 240 for the crit load panel (where the SB’s connect) when the site
has
slightly high AC voltages. The SB pushes the existing ACV higher, then
it goes
out of UL spec & disconnects. Also the SB is now sensitive to
imbalance on
L1 & L2 because of the neutral sensing – we had a customer where
the
SB was disconnecting due to this as well…<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">I
thought the freq shifting was to allow other non-SMA inverters
to be controlled when batteries were full?<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Where
is the SMA rep on this list?<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">-Glenn<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif";">From:</span></b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif";">
<a class="moz-txt-link-abbreviated" href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a class="moz-txt-link-freetext" href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <b>On Behalf Of </b>Kirpal
Khalsa<br>
<b>Sent:</b> Tuesday, October 20, 2009 12:05 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] AC Coupled Re-visited<o:p></o:p></span></p>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Greetings......it is my understanding that the
Sunny Island
coupled with Sunny Boys is able to taper charge in an AC coupled system
as the
2 inverters are able to communicate with each other and the Sunny
Island alters
the frequency input of the Sunny Boys and lowers the total output of
the Sunny
Boys to match the needs of the battery bank....this is SMA's method of
not
using their "charger"....they simply alter the amount of available AC
input into the AC to DC converter present in the Sunny Island.....This
logic is
what encouraged me to select SMA's for an AC coupled design rather than
mixing
brands of battery-less and battery based inverters.....in a mixed brand
scenario there is no communication other than an on/off command so no
regulation is available.....My understanding may be flawed--please
correct me
if so....<br>
Another way for mixed brands to AC couple and provide some charge
"control" would be to have an AC dumpload on the AC input side of the
battery based inverter to suck up some of the excess power from the GT
inverters so not as much power is available for battery
charging.....This
dumpload would be voltage based and in a mixed brand system would add
more
relays to the mix...in many cases there may not be that many auxillary
outputs
available to connect relays to.....<br>
I would like to see more GT inverter companies make compatible battery
based
inverters......One idea is for micro inverters to be paired with the
battery
based inverters and when less power was needed to facilitate a taper
charge one
solar panel at a time could be switched off......effectively providing
a
smaller available charge current to help with the taper charging.....<br>
<br>
-- <br>
Sunny Regards,<br>
Kirpal Khalsa<br>
NABCEP Certified Solar PV Installer<br>
Renewable Energy Systems<br>
<a moz-do-not-send="true" href="http://www.oregonsolarworks.com">www.oregonsolarworks.com</a><br>
541-218-0201 m<br>
541-592-3958 o<o:p></o:p></p>
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<p class="MsoNormal"><br>
On Tue, Oct 20, 2009 at 8:34 AM, Mick Abraham <<a
moz-do-not-send="true" href="mailto:mick@abrahamsolar.com">mick@abrahamsolar.com</a>>
wrote:<o:p></o:p></p>
<p class="MsoNormal" style="margin-bottom: 12pt;">Hi, All~<br>
<br>
On an AC coupled system as Jeff describes, the "battery charge
circuitry" on the battery based inverter is not even participating. <br>
<br>
A straight pure sine inverter...with no charger function built
in...would also
"charge" the battery if AC coupled to a SunnyBoy with no grid
available. The "charge" is just the inverter's way of dealing with
back EMF.<br>
<br>
I agree that better control over that "recharge" is an important
area; I hope somebody is working on that. It's true that the "wild card
recharge" only occurs if grid goes away but as Jeff mentions, it only
takes a few times of crummy end of charge management to ruin a nice set
of
sealed batteries.<br>
<br clear="all">
Mick Abraham, Proprietor<br>
<a moz-do-not-send="true" href="http://www.abrahamsolar.com"
target="_blank">www.abrahamsolar.com</a><br>
<br>
Voice: 970-731-4675<br>
<br>
<o:p></o:p></p>
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<div>
<div>
<p class="MsoNormal">On Tue, Oct 20, 2009 at 9:21 AM, Jeff Yago <<a
moz-do-not-send="true" href="mailto:jryago@netscape.com"
target="_blank">jryago@netscape.com</a>>
wrote:<o:p></o:p></p>
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<div>
<div>
<div>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Arial","sans-serif";">We have
completed several totally different AC coupled systems using different
inverters, due to large ground mounted arrays that had to be located a
great
distance from inverter-battery-generator-grid BAS, which are working
just fine
even with the mis-match of inverter brands. The SunnyBoy seems to not
care what its connected to or how, as it just keeps doing what it does
and if a
relay cuts off its connection to the grid when the battery voltage goes
high
then it just waits and re-connects when the grid is back or the battery
voltage
drops.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Arial","sans-serif";"> <o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Arial","sans-serif";">What
I am bothered by is the need to custom design a power relay circuit on
each project which takes lots of fine-tuning of setpoints to get
everything to work correctly. If you have not done one the problem is
simple - when you backfeed the AC output from a remote grid-tie
inverter
"through" the AC side of a battery based inverter, everything works
great and the solar AC just passes straight through the sub-panel, back
throught the battery inverter, back into the grid. However, when
the grid is down and the battery-inverter is no longer receiving (or
sending) power from the grid, for some reason I cannot begin to
understand, any
AC being fed from the solar inverter goes straight into battery
charging with
absolutely no limit on charge rate or charge limit, and if you do not
add a
relay to dis-connect or shut-down the solar inverter you can quickly
destroy a
bank of AGM batteries if there are no major system loads as it just
keeps
charging and charging.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Arial","sans-serif";"> <o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Arial","sans-serif";">I
am not an electronics engineer, but if the battery is being charged by
the
battery charger built into the inverter, I just do not see why the same
battery
charger suddenly has no clue that the battery is being overcharged when
its now
receiving AC power from a different source. I think with larger and
larger arrays being installed as module costs fall, higher DC array
string
voltges to reduce wire costs, and more people worried about grid
reliability, there
would be a good market niche for an inverter that can properly charge a
battery
bank regardless of which way the AC power comes into the charger
section.
Whats the problem?<o:p></o:p></span></p>
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<div>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Arial","sans-serif";"> <o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Arial","sans-serif";">Jeff
Yago<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Arial","sans-serif";">DTI
Solar<o:p></o:p></span></p>
</div>
<p class="MsoNormal"><span
style="font-size: 10pt; font-family: "Arial","sans-serif";"><br>
<o:p></o:p></span></p>
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