Network impedance estimation using two different signal processing algorithms and using discrete Fourier transform technique for single harmonic injection and statistical technique for double harmonic injection for photovoltaic inverter connected to the grid

The paper presents an on-line software method for impedance estimation of the energized impedances such as power system grid. The proposed method is based on producing a perturbation on the output of the power converter that is in the form of periodical injection of one or two voltage harmonic signals. The single harmonic injection uses a ۶۰۰ Hz signal and the double harmonic injection uses a ۴۰۰ Hz and ۶۰۰ Hz signals, respectively. During the perturbation, the current response(s) at the same frequency as the injected signal(s) is/are measured. The value of the grid impedance is estimated using two different signal processing algorithms. The DFT technique is used for the single harmonic injection and the statistic technique is used for the double harmonic injection. Selected results are presented to confirm the performances of the proposed method.

Keywords:

_Grid-connected systems , anti-islanding , adaptive flow controller_