SELECTIVE HARMONIC ELIMINATION IN VOLTAGE SOURCE INVERTER FED INDUCTION MOTOR DRIVE

Abstract

In 1973, H.S.Patel and R.G. Hoft for .the first time introduced the selective harmonic elimination technique. Since then, the problem of eliminating harmonics in switching converters has been given attention. For systems - where high switching efficiency is of importance, it is desirable to keep the switching frequency lower. For this an approach is to choose the switching times (angles) such that a desired fundamental output is generated and specifically chosen harmonics of the fundamental are suppressed. Here, a computer program using NAG Library Routine E04UCF is presented which is used to solve the non-linear transcendental equations in order to get the switching angles. By using this routine, two solutions to the switching angles have been identified, one in 0-60 degree and other in 0-90 degree mode. The plots of these switching angles for varying modulation indices are presented. A digital logic switching circuit is deigned to generate the firing pulses to the pulse width modulated voltage source inverter. Also, the total harmonic distortion is analyzed for various cases. An attempt has been made to implement the closed loop speed control of the voltage source inverter (VSI) fed induction motor drive using the Selective Harmonic Elimination technique