A Generalized Modulation Method for Capacitive AC-Link Universal Converter with Wide Reactive Power Range

This paper proposes a generalized structure with extended modulation scheme for capacitive AC-Link universal converters. Capacitive AC-Link universal converters use a small capacitor for transferring power from any type of source to any type of load. They offer numerous advantages, including high reliability, due to eliminating the need for large electrolytic capacitors, as well as high power density, due to using small capacitors and the possibility of using compact high-frequency transformers. There are still some analytical gaps in the earlier studies on this converter. Firstly, the switching pattern is power-direction dependent, and asymmetrically defined for input/output ports. Secondly, with the previously proposed modulation scheme, the power factor is limited to 0.866 lead/lag. In this paper, a generalized modulation scheme is introduced that is independent of the port type (DC or AC) or the power direction (input or output). Moreover, the proposed approach mitigates the problem of limited power factor in earlier studies and extends it to a full range operation by defining 12 new operating zones. The effectiveness of the presented modulation scheme in this work is verified through simulation and experiment.