Study of the Influence of Frequency Converters on Electrical Power Quality Indicators

The increase in the share of receivers with non-linear characteristics, among the most common being static frequency converters, produce important voltage and current distortions in electrical networks and require the adoption of effective measures to limit them. The paper presents details regarding the realization and results of an experimental study that reveals how the frequency converters that feed the asynchronous motors influence the electric power quality transmitted to the receivers. The data were acquired and processed in real time with the help of schemes made in the Labview software, being presented in the form of diagrams. The measurements performed in stationary mode highlight the shape and parameters of the line and phase voltages at the output of the converter for various operating frequencies and various load torques, analyze the frequency spectrum and the variation of the coefficients k
d
and THD. The frequency spectrum of the phase voltage highlights the fact that important harmonics appear around the switching frequency fc, respectively 2f
c
. Some aspects regarding the importance of using the current filters in improving system performance are also indicated.