Three-Level DC Converter for Balancing DC 800-V Voltage

This paper studies a three-level dc converter for balancing the dc input voltage, which has a similar topology with the conventional three-level dc converter. It can easily build a neutral line for changing a dc voltage source into two dc voltage-level sources. A control strategy of conducting time extension of partial switch devices is also presented for achieving three-level states of each power switch. The operating principle of the converter is analyzed in detail based on the presented control strategy. The small-signal model and the effects of the proposed control strategy are also driven. Finally, a prototype is fabricated and tested in the lab and the experimental results verify the converter to achieve three-level characteristics and to have a good ability of balancing the input voltage.