I've decided that putting the two CT series vs. parallel is just sum vs. average.
CT1 + CT2 vs. (CT1 + CT2)/2
I’m interested in anyone who has used a pair of CT sensors with one of these GTIL inverters (ideally 1000W or 2000W GTIL2).
I’ve assumed that’s single sensor generated an DC voltage which will be zeroed-out as long as the GTIL inverter is connected to the same phase.
In my case, rather than using two sensors to read 240V power consumption from L1 and L2, I have separateGTIL inverters for each leg (so single CT per inverter works fine) but I have a grid-tied Microinverter-based grid-tied PV system and wanted the GTILs to offset home consumption even when net grid consumption was negative (because of higher Microinverter generation than house consumption).
I connected two CT sensors in parallel (‘Y’configuration), using the second in ‘reverse’ orientation to add ‘negative’ voltage according to ‘negative’ PV generation (so PV generation is added to net ‘home-consumption minus PV generation’) resulting in a measure of home consumption which is accurate with or without PV generation on the same leg.
I assumed that two CT sensors on the same phase connected in parallel would ‘add’ the two voltages (with my PV CT sensor being connected ‘backwards’ so that it actually subtracts the negative voltage from the PV generation) and it appears to be working as I had hoped. I see the same AC/coupled grid-tied export going to the grid with the entire house load shut down or active (as long as that load is within the GTILs capacity to offset), so it seems to be working as I had expected.
I don’t understand why you believe a parallel connection of two CT sensors should ‘average’. Are saying that if I connect my two CT sensors in Series I’ll end up generating twice as much output?
Either should work to approximately measure power so long as there is a multiplication factor which can be applied.
If Line1 and Line2 aren't exactly the same voltage, there will be some error.
Where software only implements "Zero Export" but not "Export up to XXX Watts", I have a hardware workaround:
Use a step-down transformer and resistor to obtain a current proportional to AC line, and feed it though many turns of small gauge wire wrapped around CT. This creates a signal of amps x turn current flowing. Inverter will think "Zero" when it balances that offset signal.
Another:
Use an op-amp to add an AC voltage to the CT's sense resistor voltage. An offset in reading.
I agree that there are a few ways to ‘amplify’ or scale a CT-sensor-generated voltage to get 1.X times output from a GTIL, but I’m still not understanding why you think two CT sensors connected in parallel are going to provide a different net signal than two CT sensors connected in series?