This paper presents various applications of a nonlinear
adaptive notch filter which operates based on the concept
of an enhanced phase-locked loop (PLL). Applications of the filter
for online signal analysis for power systems protection, control and
power quality enhancement are presented. The proposed scheme
can be applied for signal analysis both under stationary and nonstationary
conditions. Based on digital time-domain simulations,
applications of the filter for a) sinusoidal waveform peak detection,
b) harmonic identification/detection, c) detection/extraction
of individual components of a signal, d) instantaneous reactive
current extraction, e) disturbance detection, f) noise reduction in
zero-crossings detection, and g) amplitude (phase) demodulation
for flicker estimation, are presented.