[RE-wrenches] Solaredge AC-coupling revisited

John Berdner John.Berdner at solaredge.com
Tue Feb 26 12:24:31 PST 2013


Kirk:

Yes, the latest version of firmware in the SE inverters supports AC coupling to SMA Sunny Island, and to a degree with Magnum (off grid systems).
We do not support AC coupling with Outback because they do not yet do frequency shift.

If you should get an inverter with older firmware we can update firmware two ways:


1)      Remotely update firmware for any inverter connected to the internet.

2)      All inverters with Suffix "A-US" have an SD card slot and we can send you a file or an SD card to update.

Unfortunately, I have not finished the White paper but briefly...
We need to activate the advanced power control features and then there are 4 parameters in the inverter that need to be changed.
Our support people can walk you through the programming (a bit cumbersome) or;  we can program it remotely if connected to the internet or;  we can create an SD card.
We can easily program our inverter match the Sunny Island frequency shift algorithm.
If you change any of those parameters then you would need to make the corresponding change in the SE inverter.

I am not understanding your concern regarding frying the battery and regulators.

A couple of easy solutions to what I think you are asking ...
Use a relay between the grid tied inverter and the battery inverter.
Control this relay with a voltage controlled relay or, use one of the aux relays in the SI to control it.
You need to be careful doing this to insure that the grid tied inverter disconnects only during a charge control failure.
You might need to disconnect this function during equalization which can be tricky.
Repeated disconnection of the grid tied inverter will shorten the life of the grid isolation relays in the grid tied inverter.

You might also consider a diversion regulator as a backup to conventional charge control.
A simple on off relay to an AC hot water or space heater can dissipate a lot of power relatively simply and inexpensively.

Best Regards,

John Berdner
General Manager, North America

SolarEdge Technologies, Inc.
3347 Gateway Boulevard, Fremont CA 94538 USA  (*Please note of our new address.)
T: 510.498.3200, X 747
M: 530.277.4894

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Kirk Herander
Sent: Tuesday, February 26, 2013 8:04 AM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Solaredge AC-coupling revisited

John,

The time has come where I am about to install the Solaredge system w/ AC-coupling capability. The actual battery inverter & batteries will come later as an add-on. Is the Sunny Island the only battery inverter that uses the frequency shift algorithm? The Solaredge software allows the Sunny Island to control it, backing off AC charging off like the Sunnyboy, correct? How do I know the inverter I'm getting has the new firmware installed? Thanks. Anyway I would be interested in your white paper on the subject if it's available.
Although I have AC-coupled before I feel more and more uncomfortable using a relay as an on/off charge controller, especially on large arrays vs. relatively small battery banks. Aside from the stone-age regulation akin to a Trace C-30, if the relay were to fail the battery bank could seriously fry in a matter of minutes.

Kirk Herander
VT Solar, LLC
dba Vermont Solar Engineering
NABCEPTM Certified Inaugural Certificant
NYSERDA-eligible Installer
VT RE Incentive Program Partner
802.863.1202

From: re-wrenches-bounces at lists.re-wrenches.org<mailto:re-wrenches-bounces at lists.re-wrenches.org> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of John Berdner
Sent: Wednesday, December 19, 2012 1:35 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Solaredge AC-coupling

Kirk:

We have a new version of firmware (in production January 1, 2013) that supports frequency shift power control, e.g. Sunny Island.
I am preparing a white paper on how to set it up but can walk you through it or we can preprogram it for you here and drop ship it to you for your distributor.
All of our recent product has an SD card slot so you can upgrade firmware in the field to the latest version should you receive an inverter with older firmware.
Feel free to contact me offline to discuss details on how to program.

We do not support ac coupling to other battery inverters that do not use a frequency shift algorithm.
There are a couple of issues with AC coupling to inverters that just use a relay to disconnect the grid tied inverter with a relay (ours our anyone else's).


1)      Every time you open the relay you create a grid fault and the isolation relays in the grid tied inverter cycle. Cycling on an off every 5 minutes is really hard on the relays and can lead to premature failure.

2)      The result of this relay cycling is that you end up with on/off charge control which is not very effective.  On/Off charge means the battery can never become fully charged (negative offset from the target set point).  If you increase the set point then you increase gassing which results in higher maintenance for flooded batteries and possible damage for sealed batteries.  It is a no win situation.

The magnitude or these downsides also depends on the intended application.  For a true off grid application I would never recommend AC coupling unless a frequency shift algorithm is used.  An off grid system has the potential to spends a lot of time in "regulation" and, because of the on/off charge control, the batteries never really get charged - which is not good for performance or longevity.  In a grid backup application these downsides are less of an issue because the grid is rarely down and when it is down the battery is normally discharging so the system is unlikely to spend much time in "regulation".  In my experience folks that have grid backup systems do not have the same energy awareness as those that live off grid and so they use more power.

Best Regards,

John Berdner
General Manager, North America

[cid:image001.jpg at 01CE141C.3A71A810]

3347 Gateway Boulevard, Fremont CA 94538 USA  (*Please note of our new address.)
T: 510.498.3201 ext 747
M: 530.277.4894

From: re-wrenches-bounces at lists.re-wrenches.org<mailto:re-wrenches-bounces at lists.re-wrenches.org> [mailto:re-wrenches-bounces at lists.re-wrenches.org]<mailto:[mailto:re-wrenches-bounces at lists.re-wrenches.org]> On Behalf Of Kirk Herander
Sent: Tuesday, December 18, 2012 1:16 PM
To: RE-wrenches
Subject: [RE-wrenches] Solaredge AC-coupling

Hello,

Anyone out successfully AC-coupled a Solaredge inverter with an Outback or other battery-based inverter? Thanks. I may want to do it for an upcoming job.

Kirk Herander
VT Solar, LLC
dba Vermont Solar Engineering
NABCEPTM Certified Inaugural Certificant
NYSERDA-eligible Installer
VT RE Incentive Program Partner
802.863.1202

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