Harmonic Analysis of Power System and Comparative Study of It’s Mitigation Technique

Abstract

Modern load equipment and power electronic devices, which are controlled by microprocessors, are an important source of concern for the power quality issue of electrical grids. A conventional electrical grid must produce sinusoidal voltages and currents that are unaffected by amplitude or frequency fluctuation. But the sinusoidal voltage and current waveform could not be maintained distortion free when harmonics appear due the loading of non-linear load. The harmonics mainly generate from loading of non-linear load and also there are many other reasons which are further discussed in this paper. Harmonics in load currents can have a number of negative effects, including low power factor, conductor loss, eddy current loss in transformers, etc. Harmonics cannot be totally eliminated from the grid but that can be mitigate in admissible limit. IEEE 519-2014 has given limit of THD for current and voltage distortion for various range of voltages and current. Finding a way to reduce harmonics is therefore crucial for maintaining the ideal nature of a power grid or the source. Harmonics can be mitigated by various technique which are discussed in this paper but among them the mitigating harmonics by passive, active or by hybrid filters are popular. Depending on THD of the system and current rating on have to choose the right and affordable solution for the system. In this paper we did a comparative study on passive filters types by simulating them in Matlab/Simulink. Then for overall THD reduction of a simulated 3 phase power system with nonlinear load connected we tried passive filters, active filters and hybrid filter to see the best performance. The current harmonic distortion values obtained with active and hybrid filters were well within the permissible threshold suggested by IEEE 519-2014.