How to synchronize AC output of two offgrid systems

There's an existing offgrid installation using 2x 24/3000 Multiplus in parallel. In order to charge an EV the owner plans on installing a 2nd offgrid system (with separete panels and battery) based either on 48V/5000 MP (one or two units in parallel - TBD) or a 8kVA Quattro.

For several reasons, the owner would like both AC outputs of the two Offgrid systems to be synchronized, that is, the voltage difference between both AC live wires = 0 V.

Offgrid 1 and offgrid 2 will have separate AC board, but may share conduits. There is (backup) GRID available both to offgrid 1 and offgrid 2 systems. How to achieve AC output synchronization?

I was thinking in using grid as input to both systems (even if not used) in order to the inverters synchronize. Or even feed one Inverter to the other.

Has anyone tried something similar?

2 |3000

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mt-geek commented · Oct 20, 2020 at 02:58 AM

2 inverter system can have on as much 460 volts between the live wires before they synchronize with the grid. Even when they are synchronized there will not be 0 volts because of deferent inverter and loads. [That is for a 230 volts system]

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Elimac commented · Oct 23, 2020 at 01:01 AM

Some difference is fine. What is important is that both sine waves are in sync. Anyone can give an input on how to achieve this?

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Jack Peters Elimac commented · Oct 23, 2020 at 02:42 AM

You cannot connect the outputs together. You can feed the output of one system into the input of the other. Then you will need to consider how the two systems interact, for example:

Will the first system use all of its power to charge up the battery on the second system while the PV component of the second system sits idle?

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