IDENTIFICATION OF HARMONIC DISTORTION SOURCES IN DISTRIBUTION SYSTEMS USING THE DISCRETE FOURIER TRANSFORM ON PERIODS

Abstract

The presence of non-linear loads and the increase in the number of systems of distributed generation of electricity lead to a distortion of the voltage and current waveform in distribution systems (DS), то есть к появлению гармоник тока и напряжения. In this case, the power system is obliged to supply electricity only to the fundamental frequency of 50 Hz with constant amplitude. Power supply organizations usually disclaim responsibility for the causes of harmonics by introducing standards or recommendations for limiting the levels of harmonic components in the points of common connection of consumers. These documents do not take into account the composition of DS equipment and, accordingly, the damage from this harmonics for network equipment and consumer equipment. The urgency of the work is due to the need to reliably identify the sources of harmonic distortion in the supply system for the effective functioning of the system of penalties and fines and to more effectively determine the list of measures to improve the electric power quality. The paper reviews the existing methods for distortion sources identification in supply systems. In most cases, the fast Fourier transform (FFT) is used as a method of harmonic analysis to determine the sources of distortion, which in the case of a rapidly changing non-linear load does not reliably determine the sources of distortion and the degree of participation of each DS’s subject in the power distribution of higher harmonics. In order to detail the frequency content of the signal at the measurement interval, the spectral points obtained as a result of the FFT were calculated using the Discrete Fourier Transform (DFT). A new approach to the harmonic sources identification is proposed using a method based on the measurement of harmonic power flux sense using the Discrete Fourier Transform on periods by the example a distribution network model.