Hi All,
I have the above inverter installed, since it was installed I have been told that the inverter splits the solar production into thirds and feeds a third down each phase regardless of the load.
Is this standard for 3 Phase inverters?
I believe the Open Energy Monitor setup i have is confirming this, http://grantwatson.no-ip.org:7000/emoncms/grantwatson this annoys me a bit as we can be producing more power than the house is using but still be pulling power from the grid.
Example
Solar producing 6kW
Phase 1 - load 500W
Phase 2 - load 3.5kW
Phase 3 - load 0W
So the total usage is only 4kW we are producing 6kW but because the inverter puts 2kW down each phase on the second phase we will still be pulling 1.5kW from the grid.
I believe the dashboard above is confirming this, peoples thoughts?
Grant
Re: 3 Phase - Fronius Symo 7.0-3-M
Is this standard for 3 Phase inverters?
That sounds right yes. A 3 phase grid-tied inverter should act as current source, with the same current(*) being output on each phase. It knows nothing about your loads, and can't distinguish them from your neighbour's loads.
At least in these parts (Aus) it doesn't matter. A 3 phase meter will do a signed addition of the instantaneous power on each phase. If that result is positive, it'll book it to your import register, if it's negative it'll book it to your export register. Another common-ish scenario here is to have a 3 phase house, but a single phase inverter. Using that same metering algorithm you can see there's no advantage (at least from a billing point of view) in putting the inverter on your busiest phase, although it probably makes sense from a phase-balancing point of view.
(*) or more correctly, probably the same power. The distinction only matters in the case where the phase voltages are slightly different.
Re: 3 Phase - Fronius Symo 7.0-3-M
Last year, I helped with the installation of a Mk2 router in a 3-phase environment where each phase has 4kWp of south-facing panels. Most of the base-load consumption for the property was taken from one of these phases, with the other two phases being primarily for generation only.
The operation of my 3-phase Router is to sum the flow of energies on each phase so that the net power at the supply point can be evaluated. If the net flow of energy is export, then one or more dump-loads can be applied to maintain the balance.
The supply meter at the property in question has a "sweet-zone" that appears to be around 1200 Joules. In the UK, this is a fairly standard arrangement; other types of meter allow a full 3600 Joules' worth of flexibility.
Example
Solar producing 6kW
Phase 1 - load 500W
Phase 2 - load 3.5kW
Phase 3 - load 0W
In the above example, I would not expect the supply meter to register any charge because the net consumption across all three phases is negative. Providing that surplus power can be diverted within the energy range ("sweet-zone") that is permitted by the meter, I would expect that a further 2kW could be diverted for useful on-site purposes without any penalties being applied.