Reduction of Harmonic Distortion for a Three-Phase Inverter Using Sinusoidal Pulse Width Modulator and Inductive-Capacitive Low Pass Filter

Abstract

In this work a three phase voltage source inverter which employed the sinusoidal pulse width modulated (SPWM) technique was simulated using the MATLAB/Simulink. The carrier signal (triangular) of high frequency was weighed against the reference signal (sine wave). The frequency of this signal wave was the preferred frequency. The index of modulation was set at 1 by maintaining amplitude of 1 for both the carrier signal and the modulating signal. The voltage output and current were displayed in the scope. The fast Fourier transform (FFT) of the output was analyzed to examine the Total Harmonic Distortion (THD) which varied with modulation index. In SPWM technique, the amplitude was kept constant while the width of the pulse varied as the duty cycle for each period changes. The modulated pulses were fed to the gate signals which in turn were connected to the inverter switches made up of insulated gate bipolar transistors (IGBTs). The result of the configuration resulted in a controlled output voltage. A low pass inductive-capacitive (LC) filter of a desired cut-off frequency was connected to the output to attain a well reduced THD with increased efficiency of the inverter. The inverter set-up can be employed for the control of speed of three-phase induction motors.