Hello,
Can I use any String Inverter to AC Couple to my MP2? I see the manual references Fronius and a couple others but as the Multi is the one doing the frequency change to turn on/off the PV Inverter I would think it wouldn’t be a problem please advise
If you going to AC-couple on the AC-OUT side, that inverter needs to be able to understand^1 frequency shifting, so the multis are able to reduce it’s output, when running in offgrid-mode and too much energy is beeing produced.
Also the Factor-1 Rule has to be obeyed:
https://www.victronenergy.com/live/ac_coupling:start
^1 If he does not understand complex frequency shifts he needs at least comply to requirements that it will turn off completly at a certain frequency. SHOULD be true for every grid-driven solar inverter, but never hurts to double check.
When running on AC-IN, there is AFAIK no need for anything.
Beeing able to integrate that inverter into the GX makes sence, so numbers would align properly.
But it still would work without, it will just lead to the assumption that there is 0 AC-Load on the AC IN, while the solar inverter is producing enough power to cover that needs.
(Therefore a dedicated meter could be use, if the inverter can’t be natively integrated or there is no community-solution to do so)
Yes will be on the AC-Out side I have a Solax Inverter model number X1-5.0-T-N
Which complies with the Factor-1 Rule
How do I find out if this Inverter is able to be controlled by my Multi
I was hoping Victron only recommended the Fronius brand as it’s an easy add using a GX device
Normally every new PV inverter should be controllable via frequency shift.
You have to look into the manual/datasheet or ask the manufacture about that.
Hi @M_Lange
I have a setup of 2xVictron Multiplus II’s 5kva connected in parallel single phase config along with with 3x4800wh lithium batteries. Everything has been properly configured and whole System is working fine with and without grid.
Officially multiplus can AC couple with certain brand grid tied inverters like fronius, sma, solar edge, etc. Can I try other brand inverter with frequency shifting for AC coupling purpose with my multiplus setup ? Would it void warrenty for my multiplus ?
Because the authorised dealer in my area says it will void warrenty and he is refusing to enable AC couple for my system.
Also they’re not willing to give me admin access to me in vrm. Honestly it Feels like I have system on lease which doesn’t even belong to me 
I have 3kw deye grid tied inverter with frequency shifting support which I want to ac couple with victron
Any ac coupled inverter understanding frequency shifting will work.
Direct communication through protocols is only needed for control in grid connected cases, where the multiplus has no control about frequency, cause it needs to stay synced with the grid.
I cant answer the warranty question, tho.
I wish I could try it with proper ESS Configuration. I know it would work
But the Dealer is just scaring me with warrenty issue if I even try it.
Initially before I bought the system, they said they would give it a shot and help me with AC COUPLING config.
Little did I know that they had other plans… They gave me read only access on VRM. Can’t do the necessary config for AC coupling even if I wanted to without admin/technician access on VRM. Pretty sure they must have put even some random password on VE CONFIG SOFTWARE in anticipation that I might try MK3 cable.
I guess my only option is to try ac coupling after 5 yrs when warrenty period is over. 
As said any new semi new solar inverter is able to cut out if in the UK this is baked into the grid code which all inverters coupled to the UK grid have, ie if the grid frequency ever fell or went up above or below its code those devices should drop allowing the grid to balance.
I have two Solis S6 3kW inverters on my 10kVA, AC out side both using ET112’s to monitor the output of the inverters, I’m using ESS and during that setup you set the cutoff for the solar inverter I did test, by putting in a low frequency in that setting for the Victron to send the signal to see if the solar inverter would power up when in island mode which it didn’t as soon as I went over to island mode the solar inverter wouldn’t power up at all, then I just fine tuned it once I knew it was working as should. Hope that helps
Thanks for the insight and valuable information…
My grid tied inverter is just 2 years old and manufacturer (Deye) also confirmed it.
I hope I can convince my Dealer/installer to do the necessary config for AC coupling. In my case Clearly Victron is being let down by it’s own authorized installer.
Make a suggestion to them if they are concerned about battery overcharge and grid feed back if you aren’t allowed to.
Are you using ac2 out? If not it can be set up with the generator assistant and the ac coupled installed there. You won’t have full use of it but it will kick in when needed.
What model? Your country location for the PV inverter install, You will need an ET112 on the output of the solar inverter though so it can adjust faster with the AC solar fluctuations on the load.
To be honest my dealer didn’t have any experience with AC solar so pretty much left to do it myself but as I was system installer and the process is straightforward from Victron standard point ie rule 1 to 1 and a meter on the solar inverter and your good to go once PV is setup if using ESS it would guide you through the process asking you the kW of the array and where the solar inverter is placed ie input side or output side. If your not using ESS then you would use PV assist all the best let us know how you get on
OP is more than likely feeding back to the grid with AC solar as it’s already converted to useable energy but in a grid down situation the dual relay would stop any back feed to the grid as long as the Victron is grid compliant for that country, the likely hood that OP could use all of the energy it would generate in the house load the panels would need to be undersized or have permanent loads like heat pumps used that would give continuous load in order not to feed back to the grid in any normal situation when the grid is up.
But you raised an issue that I overlooked ie battery integration does the BMS communicate direct to the GX? Like Pylontech? As that’s what I’m using.
Yes you can use output 2 but won’t give flexibility of the true power of a Victron system. My reasoning for using AC out if there is a grid line fault in the day your AC solar is still able to generate and charge the battery if it continues for another day is an issue as no dark start AC solar needs to be available to do the battery charging the frequency shifting is the secret source to the batteries not overcharging as long as they integrate with the Victron system.
But if your grids are like the UK’s at some point I can see either them sending the signal push to shut down kit due to over voltage or do rolling brown outs more winter time for that one though but this is when AC solar staying online is most important as there isn’t much in winter at all. But that was my reasoning and understanding of the AC solar limitations and most importantly not having Dark start facility, OP might not even have those concerns
Hi…
Yes the ESS config for AC couple is really easy on VE config PC software and pretty straightforward.
Ok, here is the whole story…
I’m from India, I have been exporting to grid (as per our local regulations and signed agreement with grid operator) using my deye grid tied inverter from last 2 years.
Decided to go with victron setup and lithium battery (the batteries directly communicate with GX over CAN bus 500kbps, just like pylontech), so that I can use solar when there is a grid failure and export the excess energy of solar via ac coupling when grid is available. Plan was to connect deye to AC OUT 1 of victron. I even have a victron 3P energy meter.
My installer’s reasoning is he doesn’t trust chinese grid tied inverters or any other grid tied inverter which doesn’t communicate with victron via Modbus or Sunspec protocol. He totally understands the concept of frequency shifting. But he says He says only fronius, solar edge, sma grid tied inverters are compatible and only those are victron approved. So he said he simply cannot guarantee the reliability of Chinese inverters. They may work but he won’t take any responsibility if Multiplus gets damaged due to any mishappening caused by my Deye inverter (including any overcharging of batteries caused due to deye not stopping production even when battery is full charged during a microgrid situation). I suggested we can atleast try and monitor for few days to see if it works or not. But he’s refusing to even try
He said if I even try AC coupling with any unapproved inverter, it would void my Multiplus’s warrenty
Then I pointed out that many people are using 3rd party inverter brands for AC coupling in Victron community forums. He replied that those people are DIY’ers and they can try whatever they like but that doesn’t mean victron will honor warrenty of those products of DIY’ers.
And here I though Victron was DIY’ers paradise. That why is said that My Victron’s potential is let down by victron’s own authorised dealers/installers
My other issue is they are not giving me admin access to my own system… Just read only access on VRM
Inverter model :Multiplus II 5kva 48V
I have victron 3P energy meter in single phase config
It’s a CanBus based energy meter unlike ET112 which is Modbus device
Grid tied device is deye 3kw model name “SUN-3K-G04P1-EU-AM1”
Yeah that’s a hard one as you can’t force him to do it as liability is on him but don’t know about your country but in the UK equipment has to go through ENA in order that is can be grid certified for connection meaning it’s compliant with UK grid code. Victron do support a few on a protocol level the others are just using frequency shifting this is a snippet from Victron manual
In an AC-coupled system, a grid-tied PV inverter is connected to the output of a Multi, Inverter or Quattro. PV power is first used to power the loads, then to charge the battery, and any excess PV power can be fed back to the grid.
When the Multi or Quattro is connected to the grid, this excess PV inverter power will automatically be fed back to the grid.
When the Multi or Quattro is operating in inverter-mode, disconnected from its AC input, it will create a local grid: a micro-grid. The PV Inverter will accept this micro-grid and will therefore operate even during a black-out. The PV power can even be used to charge the batteries: when there is more PV power available than used by the loads, the power will automatically run through the inverter in reverse direction and charge the batteries. It is necessary to regulate that power to prevent overcharging the batteries as well as overloading the inverter/charger. This is where ‘frequency shifting’ comes in to the picture, see next section.
Highlights:
AC-coupling is available in single-phase, split-phase and also three-phase systems.
Victron Multis and Quattros can prevent feeding back PV power to grid.
Systems with only a grid-tied PV inverter will fail when there is a grid black-out. A micro-grid system will continue to operate, and even keep using solar power.
It is also possible to run a AC-coupled micro-grid on a generator
Most brands of PV inverters can be used for these systems, they need to be setup to support frequency shifting, often called the island-mode or micro-grid mode. For SolarEdge settings, see Integrating with SolarEdge, for Fronius settings, see AC-coupled PV with Fronius PV Inverters & for reading and controling ABB/Fimer inverters, see AC-coupled PV with ABB/Fimer PV Inverters.
To read out SMA inverters, see AC-coupled PV with SMA PV Inverters.
If power will be fed back into the grid an anti-islanding device may have to be added to the system, depending on local regulations.
Frequency shifting is used to regulate the output power of a Grid-tie PV Inverter, or Grid-tie Wind inverter, by changing the frequency of the AC. The MultiPlus (or Quattro) will automatically control the frequency to prevent over charging the battery. See also the chapter 'Example & background
Yes issue with that meter is it can only read one device it’s can’t do the grid and solar, I have one that is left lonely as I can only use it to monitor one device which is my EV
I agree. That’s true. You are absolutely right…
I can’t force him to do AC coupling with 3rd party grid tied inverters with freq shifting. I guess I will have to live with it.
I guess I have no choice but to connect my grid tied inverter directly to grid instead of AC OUT 1 of victron multiplus…
I pray victron officially approves all other brands so that no one else has to suffer this kind of misunderstanding between victron, installer and customer
My installer suggested me to go for victron charge controllers and be happy with dc coupled system. Unfortunately I don’t have the budget right now to add more victron products
It’s an official configuration method just Victron only offer help supported via the protocol method rather than the grid tie frequency shift. As @lxonline said see if they will connect it to AC out 2.
Yes I thought they would say DC as that’s what many are happy to do which does have its advantage but also disadvantages.
Reasons why I went AC instant usable power without multiplus conversion, fail over protection multi or solar go down the system is independent whilst the other is is being fixed.
Less work for the multi to do as load is supported so less AC power multi has to inject.
Higher load can be sustained ie 5kVA inverter 5kW AC solar will see you over the 5kVA multiplus’s capacity when the sun is shining that is without overloading the multiplus.
Flexibility of AC if it’s not being use can go straight to grid for payment or that to be minus’d from the bill if for whatever that changes then can be used with EV ac charger to dump solar to the cars without the multiplus doing any of the work.
For me the main disadvantage to AC. Double conversion when charging the batteries ie it’s already changed from DC to AC at the solar inverter then multiplus inverter changes it back to DC to charge the batteries.
Complexity of the system/setup ie more to configure so it can run hand in hand with Victron and also planing on if input, output 1 or output 2 used.
Reliability of the AC inverter more prone to fail due to more components in the solar inverter than the DC string equipment.
No ability to Dark start the system ie if batteries are depleted their is no other way Safeway to boot the system back up but could always get a small charger grid only and use it to charge and get it to switch off once batteries could allow system to turn on but that a bit janky.
Multiplus finds AC solar harder to balance grid import export in my experience based in the UK clouds and so on as it takes a little while to read the input signal of the ET112 or the VM3P75CT so allows swings of power.
Hope this helps all the best with what you do
Thanks for the detailed explanation. Appreciate it !!!
BTW I was in contact with Victron, Netherlands about my particular issue where installer was basically scaring me off with voiding warranty if I even dare to try AC COUPLING 3rd party GRID TIED Inverter to Multiplus…
Finally the Big Guys have spoken, here is their final mail
Looks like we’re moving in the right direction folks. Atleast now we have official clarification from victron that WARRENTY WON’T BE VOIDED, UNTIL THERE IS SOME DAMAGE TO THEIR EQUIPMENTS AND THAT DAMAGE TO MULTIPLUS IS TRACED BACK TO 3rd PARTY GRID TIED INVERTER.
Now that’s a relief 
I can totally work with that. I will be in touch with my installer (Saswat, from Sunmeister Pvt Ltd), hoping to get full VRM access soon 
so that I can proceed with AC coupling config myself…
Will Update everything here for future reference for anyone planning AC coupling
Nice I would look up the Victron professional online course before doing that as there is a lot of knowledge to be gained from that before any attempts made.
