DC ripple current reduction on a single-phase PWM voltage-source rectifier

A novel topology of single-phase pulsewidth modulation (PWM) voltage-source rectifier capable of achieving not only a sinusoidal input current, but also a zero-ripple output current, is presented. The rectifier consists of a conventional single-phase PWM voltage-source rectifier, a pair of additional switches and an inductor. Hence, the proposed rectifier requires neither a large DC capacitor nor a passive L-C resonant circuit. The input current control is achieved by the conventional PWM current control technique. However, DC ripple current reduction control is difficult because one of the switching legs in the DC ripple current reduction circuit is shared with the PWM rectifier circuit. Two control methods, referred to here as the DC C inductor method and the AC inductor method, are proposed for DC ripple reduction, and the characteristics of these control methods are discussed. These control methods are implemented using a microprocessor, and the effectiveness of the circuit is confirmed experimentally. This rectifier has useful applications in uninterruptible power systems and DC power supplies, especially for cases in which the batteries are connected in parallel to the DC line.