Harmonic Minimization in a Three-phase Asymmetrical PWM Rectifier

- A new pulse-width modulation (PWM) method for a three-phase bridge rectifier developed here gives minimized low order harmonics. As a PWM rectifier, it offers better input and output characteristics than phase-controlled rectifiers. It has inherited the chmcteristics of the PWM rectifier such as having high power factor at the input with low harmonic content of the input current and zero phase-shift of input voltage and current. The availability of power transistors at high power ratings enabled the implementation of PWM rectifiers much easily. The modulation method is applied to a dc-motor drive system at 1kW rating. A high speed micro-controller produces the switching pulses