Half-cell Flying Capacitor Multicell converter: a Reduced Number of Switches Topology

In this paper a new topology of flying capacitor based multicell converter with reduced switches has been introduced. Compared with conventional multicell converters (Flying Capacitor Multicell and Stacked Multicell converters), the proposed converter doubles the number of output voltage levels and the RMS of output voltage by canceling the midpoint of DC source while the number of high frequency switches is decreased to half. The main advantages of this configuration beside mentioned improvements are minimizing the number of power electronic switches and converter cost, while the voltage rating of switches and capacitors, and the switching frequency of high frequency switches during a full cycle are kept constant. This configuration is achieved by removing one switch of each cell, which decreases the number of high frequency switches to half, and adding only four low-frequency switches to the conventional structure of Flying Capacitor Multicell converter. A modified Phase Shifted Pulse Width Modulation control scheme has been applied to the proposed topology in order to maintain the natural self balancing capability of flying capacitors. The simulation results obtained from PSCAD/EMTDC software confirm the validation of this proposed configuration advantages and its control method. Keywords— flying capacitor; multicell converter, stacked multicell converter, phase shifted pulse width modulation;