If I use three Quattros to produce a 230/400V three phase system, I get a three phase output. (So far so good)
If I supply the system with a single phase input, it can charge the battery from one Quattro.
Is there any way, it can produce a 3-phase output supplying one phase from the mains and the other two from the battery, with the single phase also charging the battery?
Technically, yes.
By unselecting the “switch as group” setting in the VE.Bus Configurator.
Note that this will disable features like ESS and the efficiency will be very poor, because one Quattro needs to rectify 2/3th of the power and put it on the DC bus for the two other Quattro’s to invert again into three phase.
If you want to create a three phase output from a single phase input there might better ways, depending on the use case.