diy solar

diy solar

feed inverter from grid


New Member
May 3, 2024
Hello there,

In our situation there is a roof top solar installation 85000wp connected to a 60kw inverter.
The max delevery to the grid is max. 20kw.
The inverter communicate with the CP measuring device.
When the machines of the workshop are running and using for example 15kw, the inverter delivers 20+15=35kw

The idea was to connect a second solar inverter via a bridge rectifier or vfd+bridge rectifier to this same grid and pump the existing power to another grid adres.
From 3 phases ac directly to a bridge rectifier (semikron skd 100/12) into de DC solar string connection of de solar inverter won't work. The current will be to high.
Is there someone at this forum who tried this before?
Regards Minck
You could need an isolation transformer (two in open wye/delta or three) to avoid troubles.

A more custom transformer could also act as current shunt (similar to neon sign transformers with limited current). However, it may be more cost effective to accomplish this with buck boost circuity. That way, the current output is limited to the capacitor stage and never directly connected to the source (logically, with the current flow - schematic wise).
Thanks for your quick reply!
Thats indeed a good option.
Our inverter has 4 mppt inputs, so have to create 4x the same configurations to feed every input seperately.
Same problem when using a standard 3 phase transformer i gues.
Searched on the internet, bus there is not a standard device which deliver such a high dc voltage.
Dc input of grid is at this moment 400v*1,41=DC564volts.
Afbeelding van WhatsApp op 2024-05-08 om 15.41.40_80d7025b.jpg
Yesterday I've tried a Danfoss VFD.
From the vfd to a bridge rectifier to the DC solar input.
First run looked good.
But when solar inverter delever current to the grid, the vfd stopped.
Alarm 16 means short ciruit...