Phasor measurement units for smart grids: Estimation algorithms and performance issues

In the near future, Phasor Meaurement Units (PMUs) are expected to play a key role not only in power transmission networks, but also to monitor power flows within distribution networks. Unfortunately, in order to face the challenges of next-generation smart grids, faster and more accurate techniques have to be developed for measuring waveform phasors, fundamental frequencies and rate of change of such frequencies (ROCOF). While the Standard IEEE C37.118.1-2011 defines clear accuracy and responsiveness boundaries for synchophasor estimation under the effect of different type of disturbances, the proposed limits have sometimes been considered as inadequate for distribution networks (either too strict or too loose). In this paper, after a brief overview of the general PMU architecture, the performance of two classes of phasor estimators (i.e. based on Discrete Fourier Transform and Least Squares optimization, respectively) are shortly, but effectively analyzed and compared both in steady-state and transient conditions.