[RE-wrenches] Outback AC coupling Sunpower?

[Mac Lewis]

Here is a paper on AC coupling the magnum.
http://www.wholesalesolar.com/pdf.folder/inverter%20pdf%20folder/MagnumACcoupling.pdf

The key is to connect the AC input terminals on the Magnum to the main
panel (or a panel closer to the utility feed) and then feed the utility
interactive inverter to a subpanel that is connected to the AC output
terminals on the Magnum.  If the grid goes down, the internal relays
isolate the Magnum and the critical load panel from the grid and the Magnum
starts to make a sine wave.

You have to keep the critical load panel amperage below the pass through
rating on the internal relays, and the grid connected inverter needs to
have a lower output than the Magnum (I think by 10%).  Also, I'm not sure
if the diversion controller Magnum has been working on is out yet or not.

I've never done this, but I am about to.  Any wrenches have experience
doing an AC coupled magnum?


On Tue, Jul 30, 2013 at 11:37 PM, Kelly Keilwitz, Whidbey Sun & Wind <
kelly at whidbeysunwind.com> wrote:

> Ray,
> The battery-based inverter in an AC-coupled system should not be
> grid-interactive. The grid passes through the BB inverter to the
> grid-direct inverter(s). The BB inverter is there to create a stable
> grid-like signal for the grid-direct inverters when the grid is not
> present, and to manage the batteries. Thus, the pass-through AC capability
> of the BB inverters normally (there is a complicated work-around) must be
> able to handle all of the PV AC output, when loads are low.
> You probably are aware, but to make it clear in this thread: the system
> needs to have some method to protect the batteries from overcharging, as a
> result of the grid-direct inverter output when the grid is down and loads
> can't use all the solar energy available. With the Sunny Islands it's done
> by a signal that reduces output from the Sunny Boys without disconnecting
> them. With Outback and others it's done with a installer-designed relay
> that disconnects the grid-direct inverter when the battery voltage gets to
> a set point. We haven't done an AC-coupled system with the Radian, yet.
> Sounds like the remote controlled breaker is Outback's approved and listed
> way to do it. About time.
>
> -Kelly
>
> Kelly Keilwitz, P.E.
> Principal
> Whidbey Sun & Wind
> Renewable Energy Systems
> NABCEP PV Installation Professional
> WA Electrical Administrator
> kelly at whidbeysunwind.com
> PH & FAX: 360.678.7131
>
>
>
> On Jul 30, 2013, at 4:23 PM, Ray Walters <ray at solarray.com> wrote:
>
> The Outback rep got me some good info, and I'm liking the Radian with the
> Remote controlled breaker to control the GT inverter when the grid is out.
>  I've heard of quite a few problems related to the Sunny Island frequency
> controlled system.
> My question is can off grid inverters like the Magnum be AC coupled?  I'm
> trying to get the price down, and still handle the 240 vac input from the
> GT inverter.
> I penciled out the Radian and I was topping $10k before installation.
>   This customer is hoping for a solution under $10k, and closer to $5k if
> possible.  I think an elegant lower cost solution for Grid tie with battery
> back up is in order.  A Radian Lite?
> For backup, it could even be mod sine, as it wouldn't be much worse than
> generator power or the average UPS setup.
>
>
> R.Ray Walters
> CTO, Solarray, Inc
> Nabcep Certified PV Installer,
> Licensed Master Electrician
> Solar Design Engineer
> 303 505-8760
>
> On 7/30/2013 2:59 PM, Ray Walters wrote:
>
> Hi All;
>
> I know AC coupled systems have been covered before, but I have a new
> issue:  positive grounding.  A customer with an existing 8kw Sunpower
> system wants to add backup.   He was put off by the high cost the Sunny
> Island, so I was steering him towards a single Outback VFX coupled to just
> one of his 3 inverters.  The issue is how will the VFX work with positive
> grounded inverters.  I'm assuming that since the two inverters will only be
> connected by AC, that the positive vs negative grounding of their separate
> DC systems will not matter.  Any experience with this particular scenario:
> Sunpower system AC coupled to an Outback?
> Also, would I even need a GVFX, since the inverter would only be used
> during outages  (which might allow a generator to be used later as well)  A
> VFX should still AC couple to the GT inverter during an outage, right?
>
> Thanks as always,
>
>
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-- 



Mac Lewis

*

"Yo solo sé que no sé nada." -Sócrates
*
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