Have not seen any reference to what source the MK 2 gets powered from. It would seem that it makes a great deal of difference since the MK 2 needs to get a specific reference of V and I for comparison.
Energy from the grid normally flows into the premises where consumption is taking place (when importing power). In this situation, the voltage and current waveforms are in-phase; they always have the same polarity.
The situation is reversed whenever surplus PV becomes available. To get energy to flow away from the premises (when exporting power), the instantaneous voltage at the PV’s inverter must always be slightly greater than that of the mains. While in this state, the voltage and current are 180° out-of-phase; their polarities are always opposite.
So, since the Export V and I are 180 degrees out of phase, this would NOT be a good reference for the MK 2 PV Router pcb then?..Am I thinking correctly here?
To detect whether energy is being imported or exported at any given moment, it is only necessary to ascertain whether the instantaneous value of Power at the grid connection point (i.e. Voltage × Current) is positive or negative.
And at what point between the mains in and the PV output can any change in polarity be recognized since they are both always different?