Instantaneous Frequency Tracking of Harmonic Distortions for Grid Impedance Identification based on Kalman Filtering

This paper presents a non-invasive approach for real-time grid impedance identification based on the principle of instantaneous frequency tracking of voltage and current harmonics already present in the system, by the use of Kalman Filter (KF). The KF based technique is compared to the FFT frequency domain approach highlighting the advantages and disadvantages of each method. The main limitation of the KF-based identification lies in its intrinsic model based nature, which in this case will limit its scope to the system steady state and to stationary signals. The KF based approach presented in this paper, can be useful as a basis for real-time grid stability assessment based on the impedance identification.