Novel Space Vector Based Generalized Discontinuous Pwm Algorithm for Induction Motor Drives

This paper presents a novel space-vector based Generalized Discontinuous pulse width modulation (GDPWM) algorithm without angle estimation based on the concept of imaginary switching times. The conventional space vector pulse width modulation (CSVPWM) method with equal division of zero state vectors V0 and V7 is modified. A constantvariable μ and modulation phase angle δ ranging from 0 to 1 are used to generate infinite number of modulating waveforms. Also, the classical triangle comparison approach is replaced by space vector approach. To avoid the complex coordinate transformations, trigonometric calculations and sector identification involved in CSVPWM, the concept of imaginary switching times is utilized. The imaginary switching times proportional to the reference phase voltages are used to calculate the actual switching times for reduced complexity and memory required. The proposed PWM technique results in reduced current ripple over the CSVPWM at high modulation indices and low switching losses at all modulation indices. To validate the proposed method, simulation is carried out on V/f controlled induction motor and the no-load current waveforms at different modulation indices and frequencies are presented and %THDs is compared.