I'm reading an article called "Online grid impedance estimation for single-phase grid-connected systems using PQ variations". I'm sending it attached.
In page 3 it is said that "...the difficulty in the estimation of Zg is that the voltage source of the grid (Vs) is immeasurable..."
Why? Can someone explain it to me?
Attachments
Online grid impedance estimation for single-phase.pdf
The difficulty is turning off the switch for all the grid current, as Ig is used everywhere, not just your location.
IMHO comments.
It is a classical ESR method except the grid distributes the problem, so the author localizes it by choosing 2 operating points. Normally 5% drop is allowed for distribution losses from transformer, so this already implies a certain ESR for the rated current of distribution feeder.