By now I have installed the BYD BBox 5.0 at a Multigrid (MG) and connected a Sunny Boy 2.5 (SB) with 2300Wp Modules.
If I try to use this as an island (mains disconnected) with only a 60W bulb as load and the battery nearly fully charged the following is happening:
Battery is working, MG is inverting and supplying the load, frequency is 50.01Hz.
After connecting the SB it will wait for some minutes, then starting and slowly increasing power up to e.g. 920W.eThe MG starts to charge the Battery. Frequency remains at 50.01Hz. Battery voltage is increasing as it it charged.
After some minutes battery voltage reaches 54.4V, MG starts to increase frequency. When 50.2Hz is reached the SB starts to reduce its power. Frequency is increased to 51.51Hz at which the SB still provides 460W (completely in line with AR4105).
Battery voltage is increasing to 55.6V. Then the MG switches off (or the BBox, I am not sure). After some seconds it starts inverting again, now at 52.01Hz. SB waits for 10 Minutes before starting up again. Freq. is still 52.01Hz, SB starts another waiting period. After some time MG reduces frequency to 50.01Hz, so SB starts again and the same thing is happening again.
I guess I need to adjust some values so that the MG switches off the SB by increasing frequency to above 51,5Hz before the battery voltage gets too high. Can you give me some advice which values to set?
Currently I have:
Bulk voltage 55.2V
Absorption: 55.0V
In ESS the frequency at which the AC couple PV interverter starts regulating is set to 50.2Hz, end of regulation 51.5Hz, Switch off at 51.51Hz.
Setting the last to 52Hz does not help.
If I set these values to 50.2/52.0/52.01 it now seems to be working.
But I would expect that the MG increases the frequency to at least the shut down frequency when the power generated is still too high and the battery voltage continues to increase. But for me it seems, the MG does not want to shut down the PV inverter even if it generates to much power for the battery to take.
Regards,
Martin