question

andy156 avatar image
andy156 asked

Can the voltage rise too much if grid is lost on a Quattro with an inverter connected on AC Out2?

I'm trying to work out where to place my SolarEdge inverter. All my loads are on AC Out 1&2 on a Quattro 10000. A heat pump and car charger are on the AC Out 2 (dropped loads). My three options are

  • AC Out 1 - This was my first choice but is not an option at the moment as the APS functionality doesn't seem to be working.
  • AC IN 2 - this was my back up option but reading around it seems I require a meter ET112 in the UK which apparantly results in extremely slow response to load changes such as clouds move in or out. I can't bring myself to accept that as the power lost&extra cost importing energy is too much.
  • AC Out 2 - I am looking at this option as I already have a bypass switch wired up so I can choose to put them back on AC Out 1 if the grid goes down. This would give the fast response and a maybe a safe cut out if I am not around.

So my question is - If connected to AC OUT 2 worst case in the summer and the inverter is at maximum output of 5kW and the grid goes down what would happen at that point? Would the inverter shut down fast enough to avoid damaging the rather expensive heat pump and car charger? They might not be actually pulling any load so that seems like a lot of power to suddenly store in capacitors? Does a SolarEdge or any inverter for that matter shut down quickly enough in that scenario. I know I have the APS issue if I switch over to the critical loads but I can choose if I want to turn the inverter on/off before switching. Ie, in the winter it isn't a problem. I only have a few days to make this decision as the installation is being completed on Tuesday.


edit: made the question more specific to ac out 2

MultiPlus Quattro Inverter Chargerquattro 10kvasolaredge
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1 Answer
Kevin Windrem avatar image
Kevin Windrem answered ·

A PV inverter connected to either the AC input or AC 2 output of the Quattro will shut down when the grid is no longer present. At the instant the grid goes down or is otherwise disconnected (including the AC 2 output relay opening), the PV inverter would supply power to any connected loads for an instant, but should regulate its voltage to prevent damage.

The inactive input to the Quattro would not have AC voltage on it so the PV inverter would never start up. A PV inverter connected to the same AC input as the grid will work in the same way as it would without the Quattro.

A PV inverter connected to the AC 1 output of the Quattro must be managed properly to avoid over voltages or other conditions. At the instant the load shuts, the PV inverter is producing power that needs to go somewhere. With a grid connection, that power goes into the grid (even if you aren't feeding power to it in an ESS system). But without a grid connection, the Quattro absorbs the power spike to avoid overvoltage and a PV inverter shutdown. That power is pushed into the battery bank. The Quattro also begins increasing the output frequency which the PV inverter senses as an indication to reduce it's output power.

For Victron systems, the PV inverter power is limited to that of the Multi/Quatro max continuous VA rating. There is also a minimum battery size specified but I don't know what that is off the top of my head. With these constraints, the system will remain stable. If not, the PV inverter will probably overvoltage and shutdown.

I don't think you can use APS with a PV inverter on theQuattro's output.

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andy156 avatar image andy156 commented ·

Hi Kevin, Thanks for your detailed reply. AC Out 2 is the one that is probably my preferred choice now. However my concern is that in a normal grid failure whilst connected on AC IN the inverter has the whole network beyond the house as a 'dump load'. But if on AC Out 2 the Victron closes a relay leaving a very small network with almost no load. Would that the inverter protect everything with nowhere for the power to go? It seems most inverters have 10 seconds to shut down. I've had it working so far on AC Out 1 but I have to turn it off manually as the battery gets close to full charge to protect my equipment. That is a recipe for disaster.


APS is supported as per 2 technical notes. One from Victron and one from SolarEdge. Unfortunately the SE doesn't appear to respond to the frequency rise as per the spec.

https://www.victronenergy.com/live/venus-os:gx_solaredge

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andy156 avatar image andy156 andy156 commented ·
I isolated everything apart from old router and simulated shutting off ac out 2. Every thing was fine so that is where I will put it I think. Thanks
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