Currently I have a 3-phase system with the Multi RS and VM-3P75CT in operation.
I’ve noticed that when exporting power to the grid during PV excess, the power on the phases are not even. (grid code: Europe)
But not just that, it doesn’t even match the individual PV power. For example:
Load [L1,L2,L3]: 100W, 100W, 100W
PV [L1,L2,L3]: 2000W, 2000W, 3000W
grid export [L1,L2,L3]: 4000W, 1000W, 2000W
So there’s a significant load on the 48V DC bus, reducing the overall efficiency.
This behavior is more or less random, sometimes the export power matches the PV power (with little to no load on the DC bus).
Is this planned to be fixed in an upcoming release?
And can I expect three phase certification for Germany any time soon?
Each grid phase has a different load and voltage → different grid export conditions → different exports.
I am referring above to the grid load outside your house, not your loads, because you export outside your house.
So all normal here, nothing to fix.
The exported power should be the excess on the individual phase though.
However, excess power from one phase is transferred to another phase via the 48V bus, which doesn’t make any sense.
Please have a look at my example. I will add a screenshot of my actual installation tomorrow.
Only if the grid conditions allows it. You cannot export whatever quantity you want. Electrical physics 101 + grid code specs.
Also, each RS is capable of exporting up to 5kW+. If it can, it will, taking the additional energy from battery system, besides PV.
But the above is just my knowledge and can be far removed from the truth…
Unless any grid parameters of one phase are out of bounds, I wouldn’t expect power transfers on low-voltage side.
And even then, the inverter should disconnect the grid entirely instead of generating uneven phase distribution IMHO.
Also, before installing the Victron system, I was using normal three-phase PV inverters which always exported evenly on the three phases. There is no issue with the grid here.
I’m not having the same issues with my 3 phase Multi RS system. Mine is following phases as you would expect. Is there maybe a phase in the wrong order on your PV system? That would be a logical explanation. Or a mixed up CT clamp from the energy meter could explain this too.
Mine is following the phases as expected aswell, but only if there’s no PV excess.
As soon as I’m exporting to the grid, the power on the phases is distributed randomly. Which means of course, that there’s significant extra load on the DC-bus.
I have two 3-phase Multi RS installations in operation by now, and I experience this issue with both. The phase order and CT clamp orientation is correct, I’ve double and triple checked that.
Phase 1 is at its limit of the inverter (~5,5kW), but is still pulling 1,4kW from the DC bus. The consequence is that it’s limiting the PV power (see first screenshot, it should produce as much as phase 2, since both are identical).
I believe this is a bug. I can’t think of a situation where this behavior makes any sense.
The total PV power is NOT shared among inverters.
The available PV power for this inverter (at its PV inputs) is 4300W.
It pushes to the grid 5500W.
The difference must come from somewhere, so the 1400W difference is from battery. (account for about 200W loses)
LE:
I believe I know now where you are hinting…
The DC energy can come from PV, rather than battery.
But I’ve seen situations, when rapid variation of the injected energy is present, up until the PV is searching for a best MPP, the battery is supplying the difference, because is much quicker at reacting than the PV.
And it’s not only under ESS.
For example, for a total off-grid installation, when a big load is suddenly starting, up until the PV is coming from behind to supply the whole power, the battery is taking over and supplies power, up until slowly, the PV is generating over the load power and the situation is balanced.
And then the consumed energy from battery is filled back up.
This is the way of things…
No, the available PV power is more than that.
4300W is the de-rated power. It’s clearly visible for multiple reasons:
phase 2 continues to deliver maximum PV power (identical setup)
phase 1 actively decreases PV current (while the voltage is rising)
without inverter overload on phase 1, both always have identical PV power
And even if the available PV power would just be 4300W, it still shouldn’t pull additional power from the battery, since it’s already exporting excess to the grid… (load on this phase is ~3000W)
Like I’ve said above. Could be a temporary situation up until the system is reaching equilibrium.
Do you mean that the draw from the battery is permanent, for say, 30 seconds or more continuously?
And also take into account grid conditions and that when the grid voltage is rising, the inverter will derate injection power.
It’s continuously drawing from the battery (like hours, if nothing changes).
The grid voltage for all three phases is nearly identical. As you can see from my screenshot, phase 1 even has the lowest grid voltage in this case.
