AC coupled: Multiplus II does not always reduce frequency

DIY
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1

I am off grid with an Easysolar II GX (a SmartSolar charger, Multiplus II inverter/charger and a Venus GX controller all in one box).
Then I have an AC coupled SunnyBoy inverter on the Multiplus’ AC Out, and I have experimented with the settings in the PV Assistant.
My batteries are 48v, base AC frequency is 50 Hz and I have these settings working mostly well:

Charge curve Adaptive + BatterySafe
Absorption voltage 57.20 V
Float voltage 54.80 V

*) Restart PV Inverters when the (temperature compensated) battery voltage becomes lower than 55.00 V.
*) The solar converter will start reducing its output power at 50.20 Hz.
Output power will be reduced to minimum when the frequency is 51.30 Hz.
The converter will disconnect when the frequency is higher than 51.40 Hz.
*) Total installed PV inverter power is 3000 Watts.
Total installed PV panel power is 3000 Watts.

The problem I am having is that the Multiplus II sometimes keeps the AC frequency high when the battery voltage has dropped below the set point of 55V which means AC load is running off batteries even though the sun is shining.

I don’t want to deplete the batteries too often and the only other way I have found to drop the frequency is to turn the EasySolar off and on again- then it senses the battery properly and sets the AC frequency to the normal 50 Hz.

Can anyone please shed any light on this behaviour?

Thanks, Graham

2

you must have relatively recent firmware on the EasySolar-II to have the restart voltage.

How does the Victron gear know what power the SMA is producing? (eg: an energy meter? comms with the SMA ?)

3

Multiplus firmware is 2623552. It seems to be 4 behind the latest 556. Is that a problem?

There are no comms between SMA and victron. The SMA responds only to the grid frequency generated by the multiplus.

4

OK, I have updated the MultiPlus II 48/5000/70-50 firmware to the latest v558, updating was painless. All the other components are also at their latest versions. Frequency was being held at 51.3 Hz for no good reason, of course has dropped since the update/restart, we will see.

I have discovered that I can manually reset the frequency by restarting the Multiplus (through VRM and the remote console feature). It would be nice to have a way to reset the high frequency without momentarily turning all the load off.