A digital method for the identification of the source of distortion in electric power systems

The correct identification of the source of distortion in voltages and currents in the electric power systems is an important factor to attain an effective compensation of the non-active components of power. The authors illustrate a method based on the evaluation of the sign of the harmonic active powers that can identify the source of distortion in three-phase systems. The practical application of this method requires the accurate determination of the frequency-domain components of voltages and currents both in amplitude and phase. An instrument is also described based on digital signal processing techniques, specially realized to perform such a frequency-domain analysis in real-time and to indicate whether the current distortion is caused by load nonlinearity or by nonsinusoidal supply voltages. The results of some experimental work are reported and the instrument accuracy is discussed