question

daniel-suchy avatar image

Multiplus II with no grid feed

Hi,

I want to use 3x Multiplus II 5 kw (3-phase) in my solar system and I am not sure about grid connection. I want it work this way:

1) If batteries are more than 20% use power from batteries.

2) If batteries are lower than 20% use energy from grid (just to power appliances, not to charge batteries)

3) If batteries are 100%, turn off MPPT or lower MPPT out power to match just my appliances demand.

4) Most important, never feed anything back to grid, because it's violating rules of our grid provider.

Can Multiplus II work this way or I need different device?

PS.: All other devices in setup will be also Victron (MPPT, Cerbero...)


Multiplus-IIgrid
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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·
5 comments
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@Matthias Lange - DE - Thank you for answer, I studied everything about ESS but I am still not sure if it's really completely prevents feed-in. From what I understand some small feed-in still can happen, when some heavy load is disconnected or something, but I really can't afford any feed-in even for one sinus wave or I can be fined.


From what I understood from trainings and manual, using Virtual Switch for triggering Ignore AC input relay is only option to really prevent any feed-in. Am I correct?

@Daniel Suchy

We are also not allowed to feed into grid without special permission. So for most of our setups we use ESS but are always pulling a small amount from the grid. Some sites 50W some sites 250W. Depending on loads and power factor.

You may also want to look into is ignore AC using the generator assistant. Especially if you are wanting to program other assistants in on the system.

There are ways to overide ignore ac on demand as well, plenty of clever resources on the forums.

Is there a reason why you are using 2xmulti 5kva instead of a 10kva?

Thanks, I will study that :) Do you have any resource or formulas how to calculate how much I need to draw depends on load and power factor?


About 2x Multiplus... sorry that was mistake, I already edited origin question, it's 3x Multiplus for 3-phase system.

No worries. No with all sites being different with both the grid feed side (resistance) and the load side PF and the like. It is more of an experiment to see how low we can go.


Normally we start higher and observe the system and see how much under the set point it "feeds back" under (and usually it is just temporary spikes), then work it down from there. So start maybe about 800W in then some sites get down to about 100W others sit above 250W.

I think there is also a determination on the definition of feedback as well that may need to be considered for your local regulations. For example a pump switching off with no Inverter in place would still have some back emf anyway. So in the case of an inverter install is that considered feedback? The obvious definition is of course produced pv power feeding to grid is not allowed.

Some countries like South Africa have very sensitive meters and any kind of back emf sets them into tamper mode.


matess4rs avatar image
matess4rs answered ·

Hi, I´m using on my 3 Multi´s ESS No Grid feed in, with Grid setpoint on 120W. Here in Czech is feed-in (also consumption) measured in 15-minute average, so small overflows in a few seconds are not registered by an electrometer.

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