Modeling non-linear loads for low-voltage electric grids

Abstract

The authors performed the computer modeling of a power distribution grid section comprising a significant non-linear and asymmetric household and office load. The modeling was performed using the SimInTech software. The developed model was used to study the impacts that non-linear single-phase consumers (e.g. computers, printers, TV sets, microwave ovens, etc) have on the distortion of current and voltage curves in the grid and the formation of current in the transformer neutral. The authors demonstrate the dependency between the higher harmonic values of the phase and transformer neutral currents and the total non-linear consumer power, their share in the overall power substation load, and the distribution of non-linear consumer load across the substation feeders. To reduce the level of harmonic current components, the authors suggest using narrow-band passive higher harmonic filters. A computer model was developed for the simultaneous operation of a single-phase non-linear load and a four-link filter compensating device that comprises the filters set for the frequencies of the third, fifth, seventh, and ninth harmonics. The analysis of the non-sinusoidal operating modes of the grids with -harmonic filters connected showed that there is practically no current in the neutral while the distortion factors of the phase currents and grid voltage curves are at the minimum.