Harmonic Impedance Detection Based on Capacitor Switching and Wavelet Packet Analysis

In order to solve the problem of harmonic pollution of power grid, finding the harmonic impedance of the system it is an important premise of the evaluation of harmonic emission level, the division of harmonic responsibility and the design of harmonic control device. In this paper, we measure the harmonic impedance of the system by the capacitor switching method based on wavelet packet decomposition. The voltage and current signals are decomposed and reconstructed by the db4 wavelet packet to obtain the voltage and current frequency division results of each frequency band. Then we calculate the harmonic impedance of each frequency band by the PCC point harmonic impedance calculation method and summarize the law of the harmonic impedance of the system as a function of frequency. At the end of the paper, the effectiveness and accuracy of the method are demonstrated by simulation experiments.