Multiplus II with 3rd party PV as boost and backup

DIY
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1

So the multiplus II has power assist, as well as backup capabilities, but it is not entirely clear to me how the disconnect and reconnect in case of power failure goes. Consider the following base setup, which I took from Victron website:

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In this setup, I would like both PowerBoost my small grid, as well as use the battery as backup.
The PowerBoost of course meaning that the MultiPlus is inverting, but in phase with the grid, just like how the 3rd party PV is inverting, in phase with both of them. Also, I would like PowerControl, meaning the battery is charged from the PV, not from the grid.

Imagine shore/grid falls away. The Multiplus will generate power, the PV will still supplement power, I assume the grid is automatically fully disconnected, as per grid requirement.

When the grid comes back, the sine is bound to be out of phase. Also, I think we do not want to reconnect it until it is stable for a few minutes.
Main question:

  • Does the Victron MultiPlus II automatically sync up the phase, before it reconnects.
  • Or is the switch back a relay switch, with a short discontinuity in both current and phase, similar to how older generations of backup systems worked?
  • If the latter, how does it deal with the 3rd party PV, which will most likely not like such discontinuity.

Ideally I imagine of course it matches grid, only then turns connects the grid.

Thanks for your input

Edit: adding this link for better study and easy finding:

2

Hi answer to your first question: yes

Your 3rd party pv does however has to support frequency shifting if its connected to ac out 1

So when the grid is lost and battery is full, the multi can throttle the pv inverter down, on grid and with grid feed in allowed this is no issue

3

Thanks

And with frequency shift, you mean the Victron will walk the frequency to 52Hz, just outside of the valid range, so the PV will turn off completely?

Or is there some smarter more intelligent and variable process?

4

Yes thats what i mean

other options are mppts to replace your pv inverter

5

Follow up question:

Been reading some more, and this page in Victron seems to tell me that the aforementioned frequency shifting is not merely on/off, but able to modulate the power: Integrating with SolarEdge [Victron Energy]

Am I interpreting that correctly?

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6

Yes thats correct, but your in inverter needs to support that

7

Since you mentioned “power assist”: what you actually want, in Victron parlance, is “ESS”, Energy Storage System. This does everything you mentioned, works with PV inverters that are not mentioned in the docs (I’m using a Huawei), and has good documentation.

It also works so well and without interruption that when we had a half-hour outage some time ago at night, we didn’t notice at all, no flickering of the lights, TV continued to work, computers didn’t crash, and I only noticed later when looking at the alarms in VRM…