A tracking bandpass filter for the rejection of power system disturbances

The authors present a bandpass filter topology suitable for tracking the fundamental frequency component of a monitored AC waveform with no phase shift between the input and output. Online dynamic phase angle information is preserved in the process. The filter is capable of rejecting severe disturbances, yet tracking longer term frequency changes. The following filters are considered: adaptive biquadratic notch filter, adaptive biquadratic bandpass filter, and combined adaptive bandpass filter of arbitrary order with a phase locked loop. The latter approach provides the greatest amount of flexibility. Results are verified experimentally with the use of an adaptive switched capacitor bandpass filter