This paper reports a method to calculate the system-side harmonic impedance based on fast independent component analysis (FastICA). Since harmonic emission of the system-side is approximately independent of the customer-side

x-y orthogonal components of voltage and current fluctuations at the point of common coupling can be demixed by FastICA to obtain independent components

and the mixed coefficients can be calculated by using ordinary least square. Thus the system-side harmonic impedance is figured out according to the linearity of mixed coefficients. By considering the joint influence of both sides

this method can reduce the system-side interference to a certain extent. The proposed method provides more accurate results in the case of larger phase-angle fluctuations without prior data to match. Based on an analysis of simulation results and field test

it is proved that the above method is effective in suppressing system harmonic interference and able to yield more accurate harmonic impedance.