Real-Time Impedance Estimation in Grid-Connected Photovoltaic System Using the Discrete Fourier Transform

The insertion of distributed generation sources into the system, such as solar power, has been challenging the monitoring, control, and protection systems. In this context, one of the most important parameter for monitoring the power system is the grid impedance. The grid impedance estimation is helpful for control system in the grid-connected photovoltaic system, detection of the islanding conditions, and protection systems. In this paper, a discrete Fourier transform-based impedance estimation active method, available in the literature, was evaluated in an experimental platform of a three-phase photovoltaic system. The experimental tests were obtained through two actual case studies, including alteration of resistance and inductance of the grid impedance as well as by inserting linear and non-linear loads at the point of common coupling.