First the setup: 3-phase domestic system with 2 Multiplus II 5000 70/48 per phase, Victron solar charger connected to DC (about 5kwp) as well as a DIY battery system. Additionally, ACout has AC-coupled PV installed (about 12kwp) as well as domestic loads.
Situation: whenever I switch “Ignore AC Input” on the Multi to on and put the system effectively into island mode, the Multis start raising the AC frequency to 53Hz in roughly 30sec intervals:
This effectively shuts down the AC coupled PV, as I suppose is the intention of the system. But: why? The battery is not full nor at voltages close to those configured for cutoff. I have the BMS even issue a “charge request” as if empty yet the Multis keep shutting out the AC PV supply (when grid connected, this immediately has the Multis pushing every electron they can get hold of towards the batteries). I can see no configured reason why the system would think it should regulate the AC PV down?
I had the same issue (3p MP2 10k, 40kWh battery, 13kWp solar): island frequency jumping to 53Hz and then ramping down to 50Hz approx. every 25sec. Turns out software-disabling AC-IN (eg via MQTT topic W/…/Ac/Control/IgnoreAcIn1 or Modbus) is apparently leading to this behavior.
If AC-IN is physically disconnected (eg. at the grid-side breaker), the island frequency stabilizes at 50Hz (resp. increases as needed to throttle down PV inverters).
read this on the bus and before anything else tripped breakers when coming home et voilà: frequency stable at 50 Hertz, PV keeps producing.
Thank you so much for the reply, this hits the nail on the head!
Might I kindly inquire how you found out? If there is some use case behind this where it should be the way it is, I might accept the behaviour. Otherwise I’d like to open a case with Victron to get this sorted out.
Kind regards,
Christian
PS: nice setup! 30k inverting power on a 13k solar array: why this and how did you convince the installer? Mine tried all he could to convince me that 1:1 ist the ratio I just have to go for.
Hi Chris, glad to hear this fixes your issue! I vaguely remember having seen a post that suggested the MP still tracks grid frequency even when ignoring AC-IN, in order to enable a quicker sync when switching back. That obviously wouldn’t work with the current behavior, so IMO that may well be a bug.
Cheers, -Hannes.
PS: that was a DIY upgrade from 15kWh storage originally installed, similar to what your installer suggested. My plan is to make use of dynamic pricing as that becomes available in order to top up battery from the grid during low-cost hours, in addition to solar.
So to anyone finding this later: this document at VEConfigure: grid codes & loss of mains detection [Victron Energy] describes, well, mentions the behaviour: “To detect a loss of mains, the inverter/charger will constantly try to shift the AC frequency.” It remains to be explained why that applies to ACout rather than ACin, and why it applies in a situation where a loss of mains has already been declared. I have asked my dealer to find that out with the good folks at Victron. I hope I get an answer.
I have noticed that not only the PV inverters will cease working, but it is noticable in household appliances as well, ie fans will speed up and certain lights will become brighter for the short periods the frequency shifts to 53Hz. Needless to say that this renders the mode unusable.
