Open loop V/f control of induction motor based on hybrid PWM with reduced torque ripple

Abstract

Voltage source inverter (VSI) fed induction motors are widely used in variable speed applications. Space Vector Pulse Width Modulation (SVPWM) has become the successful techniques to construct three phase sine wave Voltage Source Inverter (VSI) parallel to control three-phase induction motor using v/f control. Because of the low maintenance and robustness induction motors have many applications in the industries. The speed control of induction motor is more important to achieve maximum torque and efficiency. VSI fed induction motor produces a pulsating torque due to the application of non sinusoidal voltages. Among the various modulation strategies Space Vector pulse width Modulation Technique is the efficient one because it has better spectral performance and output voltage is more closed to sinusoidal. Torque pulsation is strongly influenced by PWM technique used. This paper compares the torque ripples of convectional space vector PWM with hybrid PWM techniques. In hybrid PWM both continuous PWM and discontinuous PWM techniques are employed. The open loop V/f control of induction motor with hybrid PWM shows better reduction in torque ripples when compared with conventional space vector PWM technique. The simulated design is tested using MATLAB 7.8.