Design an on grid system but with DC injection behind an AC to DC stage

[Antoine]

Hi,

I am trying to design a project a bit unusual i guess.

I have an on grid system that run on 400 V DC with an power convertion from AC main 230 V AC to DC 400 V.

I want to add a certain amount of PV energy in self-consumption, and by that way determine what amount of PV production give the best ROI. I don't want to be totally of grid and i don't want to use batterys for now. The general idea is to lower the electricity bill as much as possible with the best ROI.

My idea was to use an mppt system behind the PV array and inject directly in the 400 V DC bus, there are already some mppt on the market using this configuration (Eltek smartpack lineup for exemple).

I tryed different configuration but i cannot set a system with a DC regulation without battery.

Do you know if something like that is possible to design in PVsyst ?

NB : i am sorry for my english, i try to be as understandable as possible.

[André Mermoud]

I don't see the principle.

If you don't have a battery, and a "constrained" consumption in your DC circuit, this will comsume this energy whatever the origin (PV or grid) at a given time.

Now if you have 2 counters (grid injection and grid consumption): if the reinjection tariff is higher, you have always advantage of counting your PV electricity as reinjected. In the opposite case, you have advantage to auto-consume your PV energy. There is no better intermediate case.

In this problem, no need to assume a 400VDC circuit: you can think in terms of energy (internal load). For this evaluation, you can therefore use the "Self-consumption" option.