Trying to keep my question simple so I’m leaving out a some context. I have 3-phase MP2 and AC coupled solar panels using ESS (not DESS). External current clamps on the grid input.
Normal situation I keep the Grid Setpoint at 50W.
I have a heavy load that I don’t want to supply from the battery. If I set the Grid Setpoint to the heavy load power (e.g. 2000W) it all works fine. The grid supplies the load, the rest of the house works as normal.
However, once the load stops, the batteries will get charged at 2000W due to the setpoint.
Is there a way I can configure “don’t charge from grid”?
Note that I would like this to work on the sum of the 3 phases.
I’ve tried writing this question a few times with proper context, but it gets way too complex.
My issue is: when I have an ESS setpoint >0W and not enough load, the battery will get charged with the “spare” power and I don’t want that.
I could set the charge current to 0A, but I do want the excess (AC coupled) solar to charge the batteries.
About your suggestion: I have external CTs at the grid input (for EnFluRi). Those are needed in Belgium because it’s the only setup that is certified. The MP2s are not allowed to inject more than my existing AC solar panels.
Does the MP2 know if a load is on AC IN or AC Out (1 or 2)? If so. How?
Currently only AC IN is connected, but I’m considering putting the house on AC Out 1 so I always have backup power. The heavy load would remain on AC IN.
Usually this is related to the battery min soc in case of grid failure setting.
Not quite sure I understand what you mean by this. “Minimum SOC (unless grid fails)” is set to 10%. No matter what the battery SOC is, when I set the gridpoint >0W the MP2 will charge the battery to reach the setpoint (if the house load is lower).
For this it would be easier to set the limit inverter power instead.
Are you manually adjusting these settings or have you got them automated by something
I don’t want to limit the inverter. Whatever the house needs can be supplied via the battery. I just don’t want the heavy load to be supplied. Even if I limit it, the battery would still supply the heavy load up until the limit.
I can automate it. I can detect when the load drops and set the gridpoint back to 50W, but for most of the year I actually never want the battery to charge from grid. So if I could just tell the MP2 to only charge with excess AC power I wouldn’t need to worry about my automation failing.
Basically I expect:
Grid < 0W then charge the excess into battery (keep grid at 0W (or 50W))
This means solar provides enough to power the house and the heavy load and still has excess
Between 0W and adjustable limit (e.g. 2000W): Do nothing
This means solar is providing part of the heavy load (on top of the house)
Above 2000W: Supply from battery to keep grid at 2000W
This means solar is only partially covering the house, rest comes from battery
My setup has the Victron MP2s connected to the grid (in parallel with the house and AC solar). So everything is on AC In, nothing on AC Out1/2.
I have external CT clamps that I placed at the grid connection, so they are measuring the actual grid input/output.
I’ve just been reading some more and this doesn’t seem to be a standard setup in ESS. Although (please correct me if I’m wrong), the MP2s have no way to be aware of this. They don’t know if the house is on AC IN or AC OUT, right? Or are there two internal CTs, one on IN and one on OUT (or maybe even 3)?
EDIT: In my case, with the clamps at the grid connection, the MP2 thinks that is their AC IN (I think). Whatever else load is (virtually) on the AC Out. The challenge I have here is that both my house (that I want to supply) and the heavy load (that I don’t want to supply) are (virtually) on AC Out from the MP2s perspective.
Yes, the MP can tell that apart. So, you could usually connect the loads you want to be supplied by the batterie to AC OUT, and any loads you don’t want to drain to ACIN, between the multi and the grid meter.
Then, in ESS Settings, you can specify, if the multi should only cover loads on ACOUT (critical loads only) from the battery, or both loads.
In that case, you don’t have to manually set a different grid set point to avoid energy beeing taken from the battery and hence you would not have the issue, that a too high gsp would charge your battery, when consumption ends.
Could you please explain to me how the MP knows this? Are there internal CTs on the outputs?
So, you could usually connect the loads you want to be supplied by the batterie to AC OUT, and any loads you don’t want to drain to ACIN
This is my ultimate goal, but not so easy to install at the moment.
In this setup, where would the current clamps be? Still at the grid, like now, or just at AC IN?
In Belgium we must have the clamps at the grid for EnFluRi. The MP2s are not certified to use an external grid meter for EnFluRi.
How can I see the load on AC Out (I can use Node-Red to visualize if that makes it easier)? I just added a load on AC Out 1 to my setup, but it’s not showing up anywhere (I assume it’s just part of the indicated AC load).
When I look at “Power on output of inverter/charger” and “AC Consumption” the values are always the same. “Power between meter and inverter/charger” is always 0.
This makes me believe the MP2 does not really measure what is on AC Out, it (presumably) just calculates it based on AC IN (CT clamp) and whatever the inverter/charger is doing (which it knows/measures).
So for my setup where the CTs are at the grid entry (where “energy meter” is in your picture), the MP2s assume all loads are on AC Out (again, I think).
The CT clamps replace the internal measurement so the MultiPlus thinks that everything measured by the CT is going trough itself.
I think that’s why “Power on output of inverter/charger” and “AC Consumption” are the same.
I think you can only solve that with an external meter.
You are not allowed to use other grid meters like the EM540 or VM-3P75CT?
The CT clamps replace the internal measurement so the MultiPlus thinks that everything measured by the CT is going trough itself.
That’s what I assumed. And I think the AC Loads is calculated (CT value - Inverter/Charger), not separately measured on AC Out. So in my setup the MP2s don’t know what is on AC IN or AC OUT.
You are not allowed to use other grid meters like the EM540 or VM-3P75CT?
When we add a battery we need to make sure that our battery system cannot inject more than the AC coupled PV system that is already registered. There is a list of certified devices (C10/26 from Synergrid) where the MP2 needs “Current transformer for Multiplus-II” as “Power control system type EnFluRi”.
I’ve heard people passing inspection with an external meter, but theoretically it’s not allowed.
Anyway: my clamps must be at grid input because that is how the MP2 is certified. This means the MP2 assumes any load is at ACOUT, but I don’t care too much about that.
We’ve digressed a bit from my original question though: How can I tell the MP2 to not charge from the grid and only charge when there is injection?
Am I missing something or do you only need to move the ‘heavy load’ wiring to connect to the grid before the clamp meters and then manage your total combined maximum of ‘heavy load’ plus ‘the rest’ separately, if at all needed, not to exceed your grid main fuses. For instance by using any sort of signal that the heavy load is running and use that to limit the charge / AC-in power of the MP-II’s. There are many many ways to do that, for instance by switching the MP-II’s to inverter only but that might be much to crude a measure w.r.t. what is actually required.
I’m (technically) not allowed to move anything before the clamps because they should measure the grid. If we look at what the regulations intend to do though, then it (again technically) it can’t hurt because it’s only a load and the clamps are there to limit injection.
But that setup would prevent me from using solar for the heavy load because the MP2s will store the excess solar in the battery instead of using it for the load (with grid setpoint 50W).
It would also over-limit my injection when the load is present (although that scenario is less likely).
Are you willing to invest time to learn how to use Node-RED to read the ‘heavy load’ power (from separate meter) and use that value to actively compensate your grid setpoint for that power when needed?
I re-read above, I think @dognose correctly stated what needs to be done:
Anyway, I’ve been procrastinating from doing my taxes all day, going to log out now.
