question

JimV avatar image
JimV asked

Quattro in off-grid operation but AC input (Grid) is always present as back-up

Hi,


We are to install an off-grid PV system using 15VA Quattro, lithium batteries, and Fronius inverters. The site has grid available, hence we would want to use it as the back power supply.

We would want the AC Grid to be used by system during the following conditions:
1. Battery SoC < 20%, grid back-up to disconnect at SoC > 80%

2. Load > 12KW, grid back-up to disconnect at Load < 10kW


I read that there is an "Ignore AC Input" setting that we could possibly use to program the Quattro. Has anyone done this before?
Or do we need to use the relays and use contactors to connect /disconnect the grid to/from the Quattro?

Thanks in advance.

MultiPlus Quattro Inverter ChargerGenerator
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2 Answers
Alexandra avatar image
Alexandra answered ·

@JimV

Yes we have used ac ignore based on soc. It worked as expected. I think with your fronius you may need to make sure that when it does connect there is no grid injection if it connects during the day.

The main issue was wether to use the ac pv assistant (because technically offgrid) or ess.

The main thing is the ac ignore overrides the ess program. And of courseiif you want grud charging or not.

The other way it has been done is with relays and contactors using the aux or the bmv, gx relay for triggering. Also with the same results.

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Vangelis Beligiannis avatar image
Vangelis Beligiannis answered ·

Hi. @JimV. I have a very similar installation. A Quattro, a BYD battery, a Fronius and an MPPT. Both options mentioned were available but I decided to go with relay and the contactors using the Generator conditions of the CCGX to connect and disconnect the grid.

The advantages are:

1) Easy customisation of the parametets of connecting the grid through the Generator menu without having to reload assistant.

2) You can also manually connect and disconnect the grid any time through the GX screens

3) The Quattro is not connected directly to the grid because of the contactor. I believe this could protect it from grid problem like surges.

Only disadvantage is that contactors could become faulty over time.

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