DC-link Ripple Cancellation in Single Phase Converters

Abstract

Single phase AC/DC converters have a pulsating power that flows from the ac line to the dc bus. As a result, a low frequency ripple voltage appears on the dc-link. The most common way to solve this problem is to filter out the voltage ripple with a bulky electrolytic capacitor. With a large size and a low lifetime such a solution might not be acceptable in many applications. In order to replace the bulky electrolytic capacitor by a small film capacitor, several decoupling units have been proposed in the literature. The control strategy of these decoupling units require them to be combined with the PWM recti fier giving rise to a unique converter. To avoid this limitation, a Universal Power Decoupling Unit that can be separately built from the single phase AC/DC converter is proposed in this thesis. It makes use of a bidirectional boost converter to absorb the undesired voltage ripples. Its analysis and design are validated by simulation and experimental results