Do not feed to grid but charge battery from AC solar on AC OUT when ignoring AC IN

Q&A and troubleshooting
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1

Hi all,

I have a MPII that is semi off grid by setting it to ignore AC IN in VE configure, this works great.

Also there is a small AC solar system connected to AC-OUT, so whenever there is sun, my loads are being powered by the AC solar inverter, or the MPII charges the battery with excess solar power (awsome feature!)

But whenever AC is not ignored (due to too low battery level), so my system is temporarily connected to the grid, excess solar power is fed back to the grid instead of charging the battery with it.

I would like to configure the system such that it will always charge the battery with excess solar and never feed back to the grid when AC is not ignored.

Is this possible?

Thanks!

2

How did you configure the system?

As ess System with grid code or as off-grid without grid code?

3

I configured it with VE Configure, no ESS, no assistants, just plain VE Configure.

Grid code: None

4

Hi,

Clearly you would like your batteries to be charged, but do you have any regulatory constraints discouraging/prohibiting feed-in to the grid?

5

No, that’s not an issue in my case.

I just want the MP2 to prevent feeding back to the grid when not ignoring AC-IN. I need this to let the solar system (coupled to ACOUT) charge by battery when it’s at a low SOC. Now, when the sun shines and i have almost no loads active, the solar power is fed back. I would like to feed it into the battery instead of to the grid.

Thanks!

6

Why not using ESS with the correct grid code?
Maybe some Node-Red for fine tuning.

1 Like
7

Hi @basco

If the MP is connected to the grid and the AC solar power is greater than the used charging power of the MP2, then the unused power is fed back into the grid.

In this case, the grid frequency control does not apply, as this is specified by the grid operator. The AC solar inverter would have to be controlled, which I believe is possible with Fronius.

One idea worth trying is the priority solar function.

I haven’t tried it with AC solar yet, but it works with DC solar.

8

I think what you want is exactly what the ESS assistant will default to.

My ESS system works like you want yours to work.

9

But with unregulated AC PV inverter happens the same in ESS systems when the battery is fully charged. The unused power is fed back to the grid.

See chapter 6.1

10

For ESS i need GX device, which i don’t have. I would like to keep it simple and was hoping to configure everything with VEConfigure…

But if i can configure the system to not feed back to the grid and have ignore AC-IN working at the same it it might be worth the purchase…

11

So you enables the ESS assistant in VEConfigure? Do you also use a GX device?

thanks!

12

Can you describe why you chose the configuration you have? What advantage do you have over an ESS configuration?

What does “semi off grid” mean for you? Does your MP decide for itself when to connect to the grid?

I’m asking because your configuration is unknown to me.

13

It’s a fairly simple system:

MPII + battery

AC Solar connected to AC-OUT

Ignoring AC-IN 99% of the time even when hooked up to the grid. But then hooked up to the grid and there is lot’s of solar, i would like the MP to charge my battery instead of pushing excess current onto this grid.

14

What Mp2 model did you use and how many kW Ac solar did you have?

15

MP2 5k and 1kw Solar

16

Have a lock at chapter 10.5 ac input control

Connect to the grid by voltage/SOC should work

But it seems that the AC Solar assistant and the VS AC input control couldn´t installed at the same time.

17

Again, can you say why you chose this option? What are the advantages of this configuration?

18

´Hi @dmajwool

think he use

10.5.1. When can the grid be controlled?

The AC input relay can be programmed to selectively ignore the grid, while looking at two parameters: It can look at battery voltage and/or at AC load parameters.

The grid is ignored when the batteries are full enough. The grid is let in when the batteries are empty:

Configuration with Victron Connect is much easier as with VE.Configure

The advantage is that the mp2 could manage it alone without cerbro

19

Hi @DirkW

Yes, I get that, but why?

Why choose to “float” the house away from the grid for some periods of time? Are there advantages in frequency and voltage control of the AC in the property?

If the MP2 voltage and frequency are NOT still aligned with the grid when 10.5.1 is “ignoring” the grid then surely this introduces a wiring constraint in the house - that ALL circuits must be fed from the MP2 ACouts - Otherwise different circuits in the house will have different AC in them and this could be hazardous, no?

20

Yes i configured it just like this.

But, the current my ac coupled (at AC-OUT) solar system is making is not pushed into the battery when NOT ignoring AC-IN. but is pushed onto the grid….

I would like to push it into the battery and not onto the grid.

The MPII hardware should be able to do this (current sensor on AC-IN is there)…