A pulse frequency modulated PWM scheme for sinusoidal inverters

A pulsewidth modulated (PWM) pulse pattern optimization method using pulse frequency modulation (PFM) is described. The PFM technique is aimed at not only reducing the magnetic acoustic noise of driven motors, but also at improving the performance of sinusoidal inverters. The PWM pulse patterns are controlled so that the time-integral function of the output voltage in the space vector notation may draw a circular locus. The pulse frequency of PWM is controlled so that the performance index (PI), which represents the degrees of achieved objectives, may be minimized. Two PIs, one for minimizing the distortion of output currents and the other for minimizing the torque pulsation of driven motors, are used. The method is implemented using a single-chip microprocessor, and experimental results demonstrate its validity