Capacitor voltage regulation and pre-charge routine for a flying capacitor active rectifier

In this paper, a research is carried out on a single-phase flying capacitor active rectifier. In order to regulate the voltage of the flying capacitors, a method based on redundant state selection is developed that generates an offline switching table. In addition, an online process is introduced that, by using the offline table, reduces the total number of switching events in the converter which leads to a reduction of switching losses. This method can be used for a flying capacitor converter with any number of levels. Furthermore, in order to control the inrush current during the start-up procedure and avoid extra voltage and current stresses for active switches and capacitors, a pre-charge routine for the flying capacitors is proposed. Experimental results demonstrate the benefits of the new concepts.