Comparison of three harmonic extraction techniques for active filters

Active Alter relies heavily on the extraction of the harmonics to be eliminated from the supply waveforms. There are a variety of techniques available for achieving this. These techniques range from bandpass filters, to various configurations of phase locked loops, or synchronous rotating frame transformations and low pass filtering. This paper will introduce a variant of the standard PLL structure called the Advanced PLL, and then compare its performance against two other published PLL based techniques for harmonic extraction.