This is for RV/Boat setup, where the Multiplus2 has GridCode “None”, and is not allowed to feed into the grid, GX (VenusOS), and DVCC (forced by BMS).
My issue is, that from my perspective the MP2 acts in a way not desirable as it’s provided by Victron:
It always wants to use Grid, if Grid is available. The virtual Switch (from within VeConfig to ignore AC) is way too inflexible for my taste, and a combination with “Prefer renewables” in the Advanced Tab is not an option either (e.g. request for a full charge made impossible due to AC ignored).
Problem above, solution below?
With that in mind I did create some logic in NodeRed to monitor Watts on the Multiplus and Alarm state. If Alarm > 0 or Watt > my setting: switch from InverterOnly (Mode2) to On (Mode3).
Logic works flawless.
In Node-Red the switching between modes is instant (logic works as expected),
The massive issue:
The actual switching Mode2→Mode3 (after NodeRed sends the ModeChange request to the MP2) takes very long (for an overload scenario).
5-10 seconds until the grid is connected (after mode change request), which is way too long in case of real overload; the inverter will shut down before grid is connected. Result: Power is off for a few seconds until grid is actually connected.
Flexible “ignore AC” is necessary from my current perspective, because only with that I can also create (in Node-Red) certain other thresholds (like creating a flexible slider to set min SOC before not ignoring the grid any more), or force a full charge of the batteries, or a general grid connect if I want for whatever reason 100% SOC and not use battery/DC.
I assume the issue is that grid frequency is not monitored when in Inverter mode, and this is the reason why the transfer from Inverter to grid takes so long?
Any suggestions in regards to improving the speed from “ignore AC” to “connect to Grid”?
The system has a waiting time to ensure the grid is stable. It also has to properly synchronise. Once done it will ramp ac usage gradually. Iirc this is also affected by the grid code.
AC2 out has an even longer reconnection time.
Relevant points, thank you. I would like to elaborate a bit further:
“System has waiting time and has to synchronize”.
Makes perfect sense, there however must be more to it: The technology in the MP seems to be capable of performing a transfer much faster. If trough VeConfig VirtualSwitch “Ac Ignore” is enabled (tested on a 1P system), the transfer to accept grid (connetc from inverter to grid) happens pretty much in an instant, and Inverters will not shutoff due to overload before the transfer happens. So the same behavior must be realizable (from a technical perspective) when using logic from Node-Red (most likely only possible with the support/acknowledgement) from Victron itself.
I assume that with the virtual Switch “AC Ignore” enabled trough VeConfig, the MP2 will continuously monitor Grid and Frequency (even if relay is not connected) to ensure Inverters are in sync to realize the fast (instant) transfer.
If previous assumption is true, it should be possible (and relatively easy) for Victron (if they would chime in) to program an addition node to control this monitoring, named like “Keep sensing ACIn Freq” (On/Off). So if this sensing is enabled, changing from Mode 2 to Mode 3 could most likely be as instant as with the Virtual Switch “Ignore AC” available in VeConfig, no?
I assume the “ramp up” you referring to is only for a ESS (connected and synchronized to the grid with grid code enabled) system. This topic is specifically for MP2 which have no grid code set, and feeding the grid is not allowed.
It really is troubling that I can not easily realize a fast transfer (as “ignoer AC” does). I have to say I did test the fast transfer only in a 1P system, and here this is about a 3P system.
All the multiple brand-names of China Inverters I have had my hands on in the past were switching faster on inverter overload (only a flicker in the lights at worst, electronics most of the time would not reset). I however wanted to have something of a higher quality, and more possibilities for smart integration, so Victron. But the limitations for (from my perspective) basic stuff (with no grid code) as laid out in other posts is highly frustrating, and no direct communication channel either to discuss feasibility/usefulness of certain requirements which from my perspective are not too hard to implement…
That is a bit of an assumption.
There is a ct on the other side of the two open AC input relays, so the system can monitor voltage and frequency.
Syncing involves more than just knowing the frequency. There is no instant transfer, the system has to accept grid and ensure that output and input are coordinated, this takes times and there are limits imposed by grid codes and the multis have a ramp time, so they can never just go from disconnected to full AC.
You can drop the grid instantly, or close enough. Accepting it again is a process.
As such it makes no sense to try flick between ac on and off, you want a hysteresis so that the system isn’t triggered by transients.
The inverter system should be sized sufficiently so that the 45 or so seconds (sometimes more depending on grid and loads) isn’t an issue.
Chinese inverters are high-frequency (transformerless). The multi is a different architecture. It has a massive transformer that hums away and longer response times.
If you want a better comparison then you need to use the RS series which is also high-frequency.
I get what you say, but I have a different experience: For testing I used a 1P MP2 with Virtual Switch and “Ignore AC” activated. Inverter → Grid is instant, when the inverter is overloaded (above whatever I set), it instantly throws off the inverter and is grid connected. I tested this on a 48-5000, and deliberately turned on a mixed load at once to also force inverter overload (aside from exceeding my limit for “Ignore AC” (roughly 5kW resistive, and 2kW inductive). Result: Instant switch to grid as soon as the load was activated. This is what my assumption is based on.
I do not get the ramp time (in a non grid code, non ESS system). All the MP2 does is (when it’s ready) to turn off the inverter, and pretty much in the same instant connect grid… Maybe that behavior would be different if Power Assist is enabled, because then the inverter would also run, but that does not apply here.