After a great deal of research, I bought a Pytes V16, a Multi RS Solar, a Cerbo GX + display, a USB RS485 converter and an EM540 in order to build a PV battery storage system.
As I had previously read in reports that there can be problems with balancing in single-phase operation when using zero-export control on L1 via the VM-3P75CT, I ordered the EM540 instead and took the detour via Cerbo. I read about this option as a solution in a report.
I commissioned the system today and had to discover that although the Multi closes the grid contactors, it does not feed power into the grid.
After a bit of searching, I came across the information that the Multi’s internal ESS only works with the VM-3P75CT, and that with the EM540 you have to go via Cerbo GX and Node-RED.
Even the first tests in Node-RED, using an inject node for the ESS setpoint, showed that it takes 20 seconds to reach the specified value. That is completely unusable for a control system.
I set up a zero-export control system in Node-RED. It works as long as there are no significant load fluctuations, but as soon as even 500 W is removed, it takes 15 seconds for the value to be brought back into regulation. This is not due to the controller, but to the sluggish implementation of the ESS setpoint in the Multi. You can see the setpoint, e.g. 1500 W, while the actual value on the Multi’s display only increases very, very slowly.
Is there a solution to this problem?
Is it planned that the EM540 can also be used via Cerbo GX as a meter for the Multi’s internal ESS control?
Has the issue with the VM-3P75CT been resolved, so that summation in a three-phase system works with single-phase feed-in? If so, I would switch to this meter as well.
Also, it’s not the speed of the EM540 that’s the issue, but the latency of the Multi. I read in another thread that this problem only occurs with the German grid code and, for example, not with the European one.
However, if, for example, you enable Limit system feed-in and leave the value at 0 watts, only the phase to which the Multi RS is connected is regulated (L1 in this case).
This is actually logical, since only 0 watts can be fed into the grid on that phase. As a result, the other two phases are not balanced. What is missing is zero export across all three phases on a net basis. There is no setting for this, unlike with the MP2.
I may have overlooked something, though. If so, I would be interested to know how anyone has solved this.
With my three-phase Multi RS system and the directly connected Victron VM-3P75CT, the settling time following load changes is well under one second. So it is nowhere near the stated <10 s.
The control behaviour can be seen clearly in the video by “Meine Energiewende”.
@Dipl.Ing.1 As Arne has already mentioned, regulating load changes on a Multi RS with a directly connected VM-3P75CT takes less than a second. However, this does not apply to regulating changes to the grid setpoint when using the German grid code. Here, the control response is extremely slow (~26 W/s) and therefore does not meet the requirements of VDE AR-N 4105 either. This was discussed here ( Multi RS firmware bug in German grid code configuration - Reaction to grid setpoint changes too slow ) and has still not been fixed.
Many thanks for all your numerous and helpful replies.
I hope that Victron will provide a solution in the future that also allows for fast control using meters other than the VM-3P75CT.
I can understand that the response speed of the external setpoint input is limited, but I cannot find any indication in VDE-AR-N 4100 that control via a different meter, rather than the one directly connected, has to be slower.
It is probably related to the certification and the fact that Victron does not distinguish—or cannot distinguish—in Node-RED whether the specified setpoint comes from an “internal” controller or an “external” input.
Perhaps Victron will optimise this in the future.
I find the electrical integration of the VM-3P75CT more complicated and more space-consuming than that of an EM540, but that is a matter of personal preference.
