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dutchsolarfreak avatar image
dutchsolarfreak asked

Multiplus II: Limit total current (PV at AC-OUT + Inverter) to 16A

Hello

Sorry for asking this question but I couldn't find the answer in the documentation or here on this forum.

I have a simple set-up with one MP and a AC-Coupled PV (2400wp).

I would like to connect this AC-Coupled PV to the AC-OUT of the MP.


I'd like to dynamically restrict the total current on the AC-IN to 16A.

So for example

  • In case the PV's are producing 10A, the inverter should only invert max 6A (if case there is a total demand of 16A)
  • In case the PV's are producing 4A the inverter should invert 12A (in case there is a total demand of 16A)
  • In case there is no solar the MP should deliver this 16A.

Can this be achieved by installing a Current Transformer for MultiPlus-II on the AC-IN Side and limit the inverter current in the MP to 16A?

Thanks for your help

Multiplus-IIAC PV Couplingac out 2
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Jason - UK avatar image
Jason - UK answered ·

@DutchSolarFreak The Multiplus has its own current sensor on the AC-In. Assuming you set up the Multiplus as a ESS, if you set a inverter limited to 16A, the grid would make up any loads over 16amp if you had no PV.

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daniel-feist avatar image daniel-feist commented ·

@Jason - UK Simply limiting the inverter power does not meet @DutchSolarFreak requirements. They need to limit "feed-in" not inverter power. This can be done like this:

1701697088554.png

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Jason - UK avatar image Jason - UK daniel-feist commented ·
@Daniel Feist would I be correct in saying if Maximum feed in is set to 3600w on the above, if a load of 4000w was applied to the AC-out of the Multiplus, it would take the extra 400w from the grid with no PV? Therefore this is simplifying my solution by combining both inverter and AC input current limit into a single figure?


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daniel-feist avatar image daniel-feist Jason - UK commented ·
Yes, but I think OP wants to limit export though, (even if this wasn't said explicitly) unless I misunderstood.


I'm not sure what the use case is for limiting inverter + PV power to loads TBH. Also, I'm not sure how you would do this anyway without i) a PV meter ii) configuration which I'm not sure exists.

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dutchsolarfreak avatar image dutchsolarfreak daniel-feist commented ·
@Daniel Feist Aha a new parameter ;)

So this parameter will limit the current from MP => grid (AC-IN)

So the question is: what does the parameter "Max Inverter Power" actually do? Does it limit the DC power?

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daniel-feist avatar image daniel-feist dutchsolarfreak commented ·
Yes "max feed-in" limits export. Max inverter power does what it says, limits inverter power (inverter power may be used for loads or export). I assume you want to limit exports, right? In this case, you can configure "max feed-in" and don't need to set max inverter power.
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dutchsolarfreak avatar image dutchsolarfreak daniel-feist commented ·
Actually I'd like to limit the current to 16A only on the AC-IN (both directions) of my MP. My plan is to connect the AC coupled PV to the AC-OUT-2 of my MP.

This AC-Coupled PV is capable to deliver max 10A.

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Jason - UK avatar image Jason - UK dutchsolarfreak commented ·
@Daniel Feist its myself who limited my 5kva Multiplus to 6kW, just to stop the Multiplus from trying to supply sudden high loads which also puts a massive draw on the batteries. Nothing to do with @DutchSolarFreak . I just used my system as an example.
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daniel-feist avatar image daniel-feist dutchsolarfreak commented ·

OK, Apologies then, I assumed you were talking about limiting export. You need more than just feed-in limit configuration.


Confused as to why you would put AC-coupled PV on AC-OUT-2 though, and also why you need to limit inverter+pv to 6000W. What is the motivation for this?


EDIT: Sorry, I meant 16A (not 6000W)

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dutchsolarfreak avatar image
dutchsolarfreak answered ·

@Jason - UK Thanks for your quick answer. So I don't need a additional current meter. That's nice.

But this ESS option "Limit inverter power" confuses me a bit. Especially the word "inverter".

I thought maybe that the DC-AC inverter current is limited to 6000W. Maybe it's not true....

For example what happens if 2400W (AC-coupled PV power) is supplied to the MP at the AC-OUT? Does the DC-AC inverter only "inverts" max (6000W-2400W) = 3600W?

So 6000W is the limit of the DC-AC inverter + AC OUT?

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Jason - UK avatar image Jason - UK commented ·
@DutchSolarFreak the 6000w is just a limit I have set on my 5kva unit otherwise for several seconds during higher loads, the inverter will try and achieve where ever it can but it generates too much heat in doing so. Its specific to my installation and a setting I have applied. Ive seen my unit peak at 6.4kW for a couple of seconds but as I'm grid connected, I don't need the inverter to work so hard, more so when my high 245v grid supply voltage, sometimes it hits 253v.


The inverter inside your Multiplus has a performance range, which is dependent of several factors. grid voltage, DC voltage, ambient temperature, the internal temperature of the Multiplus, etc.

If you want to limit the inverter inside the Multiplus to 16amps, then work out the equivalent watts based on your supply voltage or just use the nominal voltage, and set the limit in the settings.

Why do you want to limit your unit?

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dutchsolarfreak avatar image dutchsolarfreak Jason - UK commented ·

@Jason - UK

Yes I was aware that this setting of 6000W was specific for your set-up

I'd like to limit more or less the AC connection to 16A (16A*230V=3600W)

So either the 3600W is supplied by my AC-coupled PV + battery or from battery only.

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Jason - UK avatar image Jason - UK Jason - UK commented ·
@DutchSolarFreak Are the AC loads on the AC-In side or the AC-Out side?
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dutchsolarfreak avatar image dutchsolarfreak Jason - UK commented ·
AC-Out
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Jason - UK avatar image Jason - UK Jason - UK commented ·

@DutchSolarFreak In basic terms, that should just be a case of limiting the inverter to 3,600w in the settings/ESS. That way the inverter will only 'generate' a maximum of 3600w. In the event of the PV generating 1000w, the inverter will make up the 2600w.

Should your loads be 5000w for example, and you have 500w of PV, the inverter will so 3600w still therefore 900w will come from the grid.

If you are trying to limit the AC-IN also to 16amps, you will have to set the current limit in VE Configure as well to 16amps. This will still allow greater than 16amps should you hav a load greater than 16amps and no PV generation.

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dutchsolarfreak avatar image
dutchsolarfreak answered ·

@Jason - UK

Thanks again for your great support!

Do you know what this checkbox "Overruled by remote" means? Is there any setting in the CerboGX?

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Jason - UK avatar image Jason - UK commented ·

@DutchSolarFreak having the box ticked I believe allows me to adjust the grid limit in VRM once I have also turned on Inverter/Charger Control in VRM settings.

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dutchsolarfreak avatar image dutchsolarfreak Jason - UK commented ·
As a start I will use the AC input limit set to 16A and uncheck the overruled by remote.
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Jason - UK avatar image
Jason - UK answered ·

@DutchSolarFreak
I have a schematic of my system in my VRM photos. I used to have a CT sensor on my grid supply then I realised I didnt need it. Then I added a EV charger so then I added a ET112 grid meter just so I can see my grid loads which are NOT supplied by the ESS via Power assist.
I have both a current limit on my AC-IN and also a inverter limit on my Multiplus like our above discussion but for different reasons.

The schematic is a little out of date as it doesn't show my 3 blueSolar 100/20 MPPT solar arrays.
https://vrm.victronenergy.com/installation/171934/share/db6807bb

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dutchsolarfreak avatar image
dutchsolarfreak answered ·

Thanks for sharing your set-up

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