Electronics > Power/Renewable Energy/EV's

PV production metering on Enphase systems fed by 208V from two phases


In Washington, DC there are blocks where single-family rowhouses have 120/208V services (two phases and a neutral from a wye-connected transformer secondary).  Enphase IQ7Plus microinverters work on these systems, but I see problems with production metering on the IQ Combiner, which measures current via a single CT on the combined output circuit.  The power production graph with the "Show Phases" option displays different values for lines L1 and L2.  I think it's because the meter is calculating total power as (IL1 * |EL1-N|) + (IL1 * |EL2-N|), and the 120-degree phase difference between L1-N and L2-N on a wye system (versus 180 on a split phase system) means that the magnitudes of the voltages aren't the same at the instant the measurement is made.

I've had a similar problem with Solaredge inverters, and the solution has been to set the inverter grid configuration to "208V No Neutral", which apparently forces the power to be calculated using the L1-L2 voltage instead of the L1-N and L2-N voltages, so the phase angle doesn't matter.

If everything can run on 208V you could just treat L1 as L and L2 as N. That way you get a system where that looks like regular single phase.

Yes, that's what the metering should be doing: simply multiplying the L1-L2 voltage by the current, without regard for the neutral.  But apparently the firmware isn't set up that way.


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