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Fedya Skitsko avatar image
Fedya Skitsko asked

Generator AC-IN and PV Inverter on AC-Out (Zero feed protection)

Hi community,

I want to take some safety and be sure that my generator will never get feed-in from the PV inverter, so my flow is like this:

  • if the grid has been lost and batteries go near 20%, I will start the generator (a small gasoline generator, without automation functions)
  • then on CerboGX, change AcSource to Generator (there is no way to change using automation, over Modbus, unfortunately)
  • the change of ac-source-type will trigger an automated workflow that will change a contactor to enable the generator and also change ac-in Amps to what the generator can make (24A) (Modbus /Ac/ActiveIn/CurrentLimit)
  • Multiplus will soak as much energy from the generator as possible from AC-In + PV solar (Fronius) on ac-out
    • while batteries are low, and still in bulk is It safe to run PV solar (Fronius) with the generator on ac-in? is it possible to get feed-in by multi into the generator?
  • The batteries will reach some "end" goal which is 80%, my plan is to disable the PV inverter using `/PvInverter/Disable` Modbus, this will give me an opportunity to PowerAssist OR change the contactor that goes to a generator

As for now, my main concern is safety and not burning generators with feed-in, all other automation of how to get back to the grid could be automated later.

Thanks for the help!

GeneratorModbus TCPFroniusvictronsafety
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2 Answers
Kevin Windrem avatar image
Kevin Windrem answered ·

You should be fine as long as the batteries can absorb any load reduction. Your plan to disable the PV inverter at high SOC may just do the trick.

The main issue is handling the excess power from the PV inverter when a load reduction occurs rapidly. The issue and the "Factor 1 rule" (aka 1:1 rule) applies in this case and is described here:

https://www.victronenergy.com/live/ac_coupling:start

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Fedya Skitsko avatar image Fedya Skitsko commented ·

If victron is in ESS mode, with full self-consumption mode, then you can clearly see even if batteries not charged till absorption- there is a feed-in from time to time.

Yes, I am following 1:1 rule

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marekp avatar image
marekp answered ·

@Fedya Skitsko

You can avoid this problem by charging battery directly from the generator.

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Fedya Skitsko avatar image Fedya Skitsko commented ·
Yea, that’s what I am seeing by default when enabling the generator ac type
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marekp avatar image marekp Fedya Skitsko commented ·
@Fedya Skitsko

What I mean by "charging directly" is that you simply install another charger between generator and battery.

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Fedya Skitsko avatar image Fedya Skitsko marekp commented ·

uh oh, why do I need another charger if I have multiplus II, that will charge with 70A ? :)


This also removes an ability to power assist in case of a huge load that victron can't handle when on batteries only

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