[RE-wrenches] Powerwall 2 AC PV regulation

[Darryl Thayer]

Regarding 3 Power Walls PWs, more solar modules, and inverters.   I hope
this is helpful, I am always going to first principles.  You did not
mention what the customer expectations are.  I see three common
possibilities, 1) For backup power, in which case you need generation
control, such as the AC Diversion control that Magnum solar used to make,
or the frequency shift of the master PW shutting down the inverters.  I
have no idea how the PWs synchronize.  Depending upon the model and age of
the inverters they will back down until they shut off by frequency shift.
>From full power to shutoff is about 0.6 Hz.  If the inverters do not have
frequency shift power correction the inverters will shut down.  Then stay
down for 5 min until time to restart.   2) TOU or TOD (time of day energy
pricing)  with and without full net metering.  The grid is connected the
solar inverter can export when the battery is full.  When the solar is
insufficient the gateway programming directs the PWs to carry enough of the
load to prevent power import. excessive charges.  If you have two different
pricing a study by Egauge or similar should be done to full fill the
highest cost energy needs.  This study should reveal the lowest price
period and the amount of off-peak energy to buy.  If you have data from the
SMA or Egauge as to the past records you can modify your program using the
probability of sun.  3)  No export, this is similar to backup power except
the grid provides synchronization and the inverters must have non-frequency
power limitation.  This is very tricky.    .  not sufficient power is


On Sat, Apr 17, 2021 at 2:26 AM Jason Szumlanski <
jason at floridasolardesigngroup.com> wrote:

> I think the limit is now stated as 7.6kw if memory serves me right.
>
> Jason
>
> On Fri, Apr 16, 2021, 12:11 PM Matt Partymiller <matt at sesre.com> wrote:
>
>> They used to advocate 7.9kW AC/DC per Powerwall.  That number may have
>> gone down recently.  Coupling an inverter on the line side of the backup
>> gateway will resolve your issue of meeting homeowner demand.  Tesla will
>> want you to add a CT to that inverter to ensure it does not mess up their
>> monitoring system, though that may already be incorrectly configured and
>> not monitoring the whole home if the system is backup only.
>>
>>
>>
>> Matt
>>
>>
>>
>>
>>
>>
>>
>> Matt Partymiller
>>
>> General Manager
>>
>> Solar Energy Solutions, LLC
>>
>> Lexington | Louisville | Bloomington | Cincinnati | Evansville |
>> Indianapolis
>>
>> 859-312-7456 (Office)
>>
>> 877-312-7456 (General)
>> matt at sesre.com
>>
>>
>>
>> Check out our amazing new website and social media updates: www.sesre.com
>>
>> <http://www.sesre.com/>
>> <https://www.facebook.com/SolarEnergySolutionsLLC>
>> <https://www.instagram.com/solarenergysols>
>> <https://twitter.com/SolarEnergySols>
>> <https://www.linkedin.com/company/sesre>
>>
>>
>>
>> *From:* RE-wrenches <re-wrenches-bounces at lists.re-wrenches.org> *On
>> Behalf Of *Kirk Herander, VSE
>> *Sent:* Friday, April 16, 2021 11:13 AM
>> *To:* re-wrenches at lists.re-wrenches.org
>> *Subject:* [RE-wrenches] Powerwall 2 AC PV regulation
>>
>>
>>
>> Hello all,
>>
>> I am adding more PV to an orphaned Powerwall 2 AC system (which is all
>> new to me), -3- PW's stacked to total about 40kwh of usable storage. it
>> presently has about 13kw of PV, though -2- SMA inverters, feeding into it
>> through a common subpanel between the PW gateway and the main panel. I'm
>> wondering if there is a limit to the amount of PV the powerwall can
>> regulate/backoff (or use for battery charging) during a utility outage.
>> What is the max PW charge rate? I need to add about 10 kw of PV to produce
>> the owners goal of 100% coverage of electrical demand.
>>
>> If necessary for safety, i assume the extra pv inverter can be routed to
>> the main panel, and then won't participate in battery charging if the grid
>> goes down. Am I correct? Thanks. The PW manuals are of little use here.
>>
>>
>>
>> *Kirk Herander / kirkh at vermont.solar <kirkh at vermont.solar>*
>>
>> *Owner|Principal, VT Solar, LLC*
>>
>> *Celebrating our 30th Anniversary 1991-2021!!*
>>
>> *www.vermont.solar*
>> <https://nam02.safelinks.protection.outlook.com/?url=www.vermontsolarnow.com&data=02%7C01%7C%7C9f0330d75a244870112408d685311841%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636842843233477645&sdata=0NjyuKeQbEK6245SNnk8X4XnP9Q%2B%2BqtvcALkdDghvk4%3D&reserved=0>
>>
>> dba Vermont Solar Engineering
>>
>> 802.863.1202
>> _______________________________________________
>> List sponsored by Redwood Alliance
>>
>> List Address: RE-wrenches at lists.re-wrenches.org
>>
>> Change listserver email address & settings:
>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>>
>> There are two list archives for searching. When one doesn't work, try the
>> other:
>> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/
>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>>
>> List rules & etiquette:
>> http://www.re-wrenches.org/etiquette.htm
>>
>> Check out or update participant bios:
>> http://www.members.re-wrenches.org
>>
>> _______________________________________________
> List sponsored by Redwood Alliance
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Change listserver email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> There are two list archives for searching. When one doesn't work, try the
> other:
> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/
> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules & etiquette:
> http://www.re-wrenches.org/etiquette.htm
>
> Check out or update participant bios:
> http://www.members.re-wrenches.org
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches_lists.re-wrenches.org/attachments/20210418/3cfddede/attachment.htm>