Have a look on Arduino pages
in a documentation film they showed a remote micro-grid..
the controller for these was i think ESP32 or so based and the cases 3d-printed..
i did not remember what it was called..
a quick search on open source micro-grid resulted in this:
but after looking at it it turns out its only a very meta starting point..
the second is from GreatScott! - i like his style to explain things...
i personally just use a commercial one (phoenix 500) in my small off-grid setup..
(i needed something that just works ;-) - and if i find some spare time i will try to read / do something with the VE.direct management connection)
if you find a good tutorial / build one - please post here!