Response to Discussion on “A Variable Switching Frequency PWM Technique for Induction Motor Drive to Spread Acoustic Noise Spectrum With Reduced Current Ripple”

Abstract

In random pulse width modulation (RPWM) category, a wide variety of schemes is seen as described in the paper. The discussion part is mainly focused on the randomized carrier frequency approach, where the switching periods are selected randomly, irrespective of the ripple voltage. For prediction of rms current ripple over a switching cycle as well as rms current ripple over the line cycle, precise knowledge of the switching period is required; this is not possible with random PWM techniques, though these methods are following a probability distribution function. However, accurate prediction of current total harmonic distortion (THD) is possible with the variable frequency PWM (VFPWM) method, as the switching period is a function of the fundamental angle. The procedure followed for current THD prediction is explained in [1].