A Tuned Whitening-Based Taylor-Kalman Filter for P Class Phasor Measurement Units

Protection-oriented (P Class) phasor measurement units (PMUs) are required to reconcile high measurement accuracy and low latency in order to promptly detect possible anomalous operating conditions in power systems. Most of the existing estimators of synchrophasor magnitude, phase, frequency, and rate of change of frequency (ROCOF) of voltage or current AC waveforms need to acquire the samples of at least two power line cycles to meet the P Class requirements specified in the IEEE/IEC Standard 60255-118-1:2018. In this article, instead, a multistep technique based on the combination of multiple signal classification (MUSIC), narrowband disturbance whitening, and Taylor-Kalman Filtering (TKF) is proposed to maximize accuracy even over one-cycle-long observation intervals. Both MUSIC and disturbance whitening rely on a common theoretical framework (i.e., signal and noise vector subspace decomposition) and they are applied to compensate for the detrimental effect of off-nominal frequency deviations and harmonic distortion, respectively. The use of cascaded dynamic estimators such as the TKF is motivated by the need to track possible in-band amplitude and phase oscillations or step-like changes with low latency. While the basic TKF is very sensitive to possible narrowband disturbances, the tuned whitening-based TKF (TW-TKF) described in this article ensures superior accuracy under the influence of harmonics and amplitude or phase step changes, with just a minor performance degradation in the other P Class testing conditions reported in the IEEE/IEC Standard 60255-118-1:2018.