Employment of Interpolated DFT-based PMU Algorithms in Three-Phase Systems

Phasor measurement units (PMUs) are the key measurement devices of modern power networks monitoring systems. The high accuracy and fast reporting rates required for PMU implementations ask for improvements in both hardware and software solutions. Depending on the characteristics of the monitored voltages and currents, the accuracy of PMU algorithms may represent the main contribution to the overall measurement performance. For this reason, research is ongoing in the field of signal processing techniques for phasor and frequency estimation. In this context, Interpolated Discrete Fourier Transform (IpDFT) is one of the most interesting techniques, mainly because it allows accurate measurements under off-nominal frequency conditions while preserving simplicity and computational efficiency. In this paper, the applicability of IpDFT to three-phase signals that are typical of power networks is discussed. Then, it is proposed to combine the advantages of IpDFT with those of the Space Vector approach for positive sequence synchrophasor and frequency measurements