Harmonic impedance measurement based on short time current injections

•Real time estimation of power systems impedance of composite network, e.g. with lumped or distributed parameters, linear and nonlinear loads.•No modification in the power system is required, such as, nonlinear load disconnecting. It is necessary only a point to inject the test source.•Generation of a small perturbation is used to estimate the impedance.•The method was validated in real time using the hardware in the loop approach, and an experimental case demonstrates the feasibility of the method.•The background harmonic distortion in the supply source does not affect the accuracy of the method. This work presents an alternative method of measuring the equivalent impedance of an electric power network by injecting a short time current waveform based on Modulated Gaussian Signal. The frequency domain measurement of the equivalent impedance of an electric network is an important issue to correctly design harmonic filters and capacitor banks, detect resonance and antiresonance frequencies and evaluate the harmonic penetration and emission limits. The method proposed in this paper uses the Sliding Window Recursive Discrete Fourier Transform (SWRDFT) to extract the harmonic components of the measured voltage due to the injection of the short time current into the network. The proposed method was tested with different electric system topologies and the estimated impedance was compared with the impedance estimated by other methods found in the literature. Real time simulation using Hardware-in-the-Loop (HIL) methodology, as well as experimental results are presented in this paper.