An Adaptive Phasor Estimator for Power System Waveforms Containing Transients

Synchronized phasor measurement has gained wide acceptance in many power system applications, particularly for tracking dynamic transitions during various disturbances. Fourier filter-based phasor estimation algorithms, which have been predominately used in phasor measurement units, have difficulties in processing dynamic sinusoidal waveform distortions, such as modulation, frequency drift, abrupt change in magnitude, etc. This paper proposes an adaptive approach for accurately estimating phasors while eliminating the effect of various transient disturbances on voltages and currents. The method preanalyzes the waveform spanning the window of observation to identify and localize the discontinuities which affect the accuracy of phasor computation. A quadratic polynomial signal model is used to improve the accuracy of phasor estimates during power oscillations. Extensive experimental results demonstrate the advantages. The method was implemented on a PC-based PXI system for real-time phasor computations. It can also be used as reference algorithm for testing the performance of the devices extracting synchronized phasor measurements.