DC ripple current reduction on a single phase PWM voltage source converter

This paper presents a novel topology for a single phase PWM voltage source power converter which can achieve not only sinusoidal input current but also zero-ripple output current. The proposed power converter consists of a conventional single phase PWM voltage source converter and a ripple reduction circuit. The ripple reduction circuit consists of an additional switching leg, an inductor and a switching leg that is shared with that of the PWM converter. Input current control is achieved by the conventional PWM current control technique. However, DC ripple current reduction control has some difficulties because one of the switching legs in the DC ripple current reduction circuit is shared with that of the PWM converter circuit. Two kinds of control methods for DC ripple current reduction, which the authors call the "DC inductor method" and the "AC inductor method", are proposed and their characteristics are discussed. Both of these control methods are implemented by employing microprocessors. The effectiveness of this circuit is confirmed by experiments and simulations. This converter is useful for UPSs and DC power supplies, especially in case that batteries are connected to the DC line.