PLL Based Digital Adaptive Filter for Detecting Interharmonics

Abstract

Studies on the PLL (phase locked loop) based interharmonic measurements have been considerably increased recently. The method proposed in this study is a hybrid method based on the frequency analysis. The proposed method presents solutions for the leading problems about the interharmonic measurement, such as fundamental frequency shifting, spectral leakage, and picketfence effect, using digital PLL and adaptive notch filter. In addition, a new approach is presented to solve the multizero crossing problem encountered in the analysis of the harmonicinterharmonic. Both simulative and field data tests have been performed to verify the effectiveness of the proposed method.