Analysis and Simulation of Single Phase Composite Observer for Harmonics Extraction

The method of extracting individual harmonics from repetitive signals using multiple asymptotic observers is analyzed in this paper. For proper operation of such a composite observer, it is sufficient if the fundamental frequency is approximately made known because, the implementation exhibits sufficient pass-bandwidth centered on the assumed fundamental as well as the harmonics. However, the settling period and the bandwidth of the observer depend on how far the observer poles have been placed from the origin of the s-plane or the z-plane. The effect of small deviations from the central fundamental frequency of the observer, on the magnitudes and phase angles of the extracted signals is discussed. These parameters assume significance when the composite observer is used in feedback loops. Simulation and experimental results are incorporated.