Implementation of phasor measurement units on low-cost embedded platforms: A feasibility study

Abstract

The Phasor Measurement Units (PMUs) are currently considered among the most useful instruments for smart grid monitoring. While the traditional PMUs deployed at the transmission level are usually high-performance and expensive instruments, the interest in smaller and cheaper units able to perform synchronized measurements of voltage and current waveforms at the distribution level is currently growing. In this paper, a feasibility study about the implementation of state-of-the-art estimation algorithms for PMUs in low-cost embedded platforms is presented. The proposed approach relies on an Interpolated Discrete Fourier Transform (IpDFT) for static frequency offset estimation followed by a modified Taylor-Fourier Transform (TFT) for waveform amplitude, phase, frequency and rate of change of frequency (ROCOF) estimation under dynamic conditions. Both algorithms, implemented in C++, run on a Beagle-Bone Black board. After evaluating the total computation time as a function of both the sampling rate and the number of observed cycles, a criterion to choose the data acquisition stage is described. Finally, the accuracy of synchrophasor, frequency and ROCOF estimators is determined by emulating most of the testing conditions reported in the IEEE Standards C37.118.1-2011 and C37.118.1a-2014.