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

The present paper introduces a novel topology for a single-phase PWM voltage source power converter and a related control method that can produce not only a sinusoidal input current but also zero-ripple output current. The main circuit of this power converter is composed of a conventional single-phase PWM voltage source power converter and a ripple reduction circuit. The ripple reduction circuit is composed of an additional switching leg, an inductor and a switching leg that is shared with the PWM power converter. Input current control is achieved by the conventional high-frequency PWM current control technique. On the other hand, DC ripple reduction control is associated with some difficulties because one of the switching legs in the ripple reducing portion is shared with the PWM power converter portion. In order to reduce the DC ripple current, the inductor current at the ripple reducing portion must be maintained to an adequate value which is deeply influenced by the modulation factor on the PWM power converter. The relationship between the modulation factor and the inductor current was analysed and the inductor current necessary for DC ripple current reduction was studied. The effectiveness of this circuit was confirmed experimentally and by simulation The power converter is useful for UPSs and DC power supplies, particularly in the case in which batteries are connected to the DC line.