G'day, I have a customer that we installed a Fronius 5kW AC Coupled to a 5kVa Multiplus in an off grid install. I've also DC Coupled in a SmartSolar and connected to SunGel Carbon Gel batteries.
The customer is now experiencing his AC powered clocks running fast and I suspect it is caused by frequency shift as the Multi controls the Fronius.
Is there a solution to remedy this issue? Thanks in advance!
I can confirm that it is caused by the increase in AC frequency that happens when the batteries are full and the Multi is sending the the signal to the Fronius to stop producing.
One remedy is to replace the clocks with those that use a quartz timer instead of the AC frequency.
Another solution would be to have a dump load available that consumes any surplus power when the batteries are full so that the solar production has somewhere to go without needing to be turned off (such as hot water).
This is a common and known consequence of all frequency shifting power control setups. It is also one of the reasons that DC solar charge controllers are preferred when off grid and charging batteries.
A last resort (and I have had a customer do this) is to get a battery charger, battery and seperate inverter and create ANOTHER micro-power system just for running his favourite bedside alarm clock!
Hello https://community.victronenergy.com/users/14/guy.html Guy, does Victron have any function for ajusting de clocks in reverse?
for the time that the frequency is above 50Hz, SMA does have a function for that.
Tks
Hi @ditmarco,
No we don't.
I think the reason that SMA went to the extra effort for such a system is because they use frequency shift power control as the PRIMARY control method with the Sunny Island and Sunnyboy system.
From Victron's perspective, while we support AC frequency control, we recommend DC coupled PV as the primary method, Modbus TCP as the secondary method, and frequency shift power control as the last.
Get a small UPS system like you have for a computer, power it from the inverter, and run the clock off that, problem solved.
The solution to this frequency shifting would be to use the same concept that Selectronic uses in its AC coupled off-grid systems.
Managed AC coupling directly controls the DC panel input into the Fronius inverter at up to 0.1% steps, resulting in very quick and accurate control all while eliminating the need for frequency shifting.
As the off-grid systems are getting bigger all the time maybe Victron should look at producing their own AC coupled inverter that is directly controlled by the VE Direct system, that would solve the issue altogether.
