A PWM inverter with DC busbar voltage modulation of capacitor discharge

Abstract

A PWM (pulsewidth-modulated) inverter with DC busbar voltage modulation of the capacitor discharge is presented and analyzed. DC busbar voltage is periodically modulated to zero, which can arise the switching frequency of the power switches by about one order of magnitude. The inverter is well suited for fully controlled power switches. A PWM-controlled scheme for a variable-frequency three-phase induction-motor drive especially suitable for this inverter circuit is discussed. The scheme adopts linear adaptive delta modulation to produce the PWM sequence. With delta modulation it is easy to change from a PWM pulse sequence to a square sequence smoothly. Microcomputer software can be used to produce the PWM sequence in real time.<>