Harmonic Analysis And Three Harmonic Suppression Of Low Voltage Distribution

With the development of national economy and power electronics technology, more and more nonlinear loads are applied to the low voltage distribution, These nonlinear loads are mostly rectifier circuit, which increase the distribution harmonics, more three harmonic, three harmonic currents are superimposed on zero line, resulting zero line’s current too large, reducing its life or fires may occur. Three harmonic current not only make distribution current distortion but also affect power quality, and three harmonic current flows through wire cause unnecessary heat loss.From analysis harmonic and the effect of three harmonic on low voltage distribution as a starting point of the research, using the MATLAB/Simulink simulation analysis low voltage distribution’s harmonic, simulation three phase four wire system, analysis the simulation’s current content of three phase and zero line by using FFT method. And detect the resident low voltage distribution. From test results analysis three harmonic influences on low voltage distribution. For three harmonic current zero sequence characteristics, give a method for estimating losses caused by three harmonic.In order to verify the elimination of three harmonic current is beneficial to power, experimental program designed to suppress the three harmonic of three phase four wire system, comparative the test of before and after three harmonic current suppression analysis low voltage residential distribution by adding a three harmonic filter on zero line, through the measured test analysis the influence of eliminate three harmonic current on saving energy and power quality, in addition, a mathematical model of transient process caused by the switching device to switch in the experimental program is established, and analysis three harmonic current transient process of jump by difference method.The results of harmonic analysis and three harmonic suppression of low voltage distribution show that, due to the extensive use of nonlinear loads in low voltage residential distribution, three harmonic current is very high, the loss caused by three harmonic is the embodiment of heat loss, due to the phase current is mainly composed of fundamental current, despite the zero line is mainly the three harmonic current, the heat loss is limited because of the zero line is relatively short, therefore, the energy saving is very limited suppress three harmonic, but, in the three harmonic distortion more occasions, elimination three harmonic can achieve more obvious energy saving effect.