Three Phase Vsi Using Sinusoidal Pwm Technique

Abstract

Inverter is the most important device to utilize the renewable energy sources efficiently. The Sinusoidal Pulse Width Modulation (SPWM) technique is one of the most popular PWM techniques for harmonic reduction of inverters since there are used three sine waves displaced in 1200 phase difference as reference signals for three phase inverter. This paper presents the simulation of three phase voltage switching inverter in MATLAB/Simulink using Sinusoidal Pulse Width Modulation (SPWM) scheme. The carrier wave (triangular) is compared to the reference (sine wave), whose frequency is the desired frequency. The modulation index is varied from 0.4 to 1 by changing the amplitude of the modulating signal. The output phase and line voltages are observed in scope along with their Total Harmonic Distortion (THD) which varies with modulation index. In SPWM technique, the amplitude is constant but the width of the pulse varies by changing the duty cycle for each period. The width of the pulses are modulated to provide gate signals to the switches (IGBTs) connected in the inverter. In this way the output voltage is controlled and THD also reduces significantly with the increase in efficiency of the inverter. This method is popularly used in speed control of three phase induction motors. The load taken here is resistive and inductive (RL).