An MMC-based modular unipolar/bipolar high-voltage nanosecond pulse generator with adjustable rise/fall time

Abstract

The rise/fall time of a high-voltage nanosecond pulse affects the application effect of the pulse; therefore, it is of great significance to study the adjustment of the rise/fall time. In this paper, a new type of generator topology based on a half-bridge modular multilevel converter (HB-MMC) is proposed that uses MOSFETs as solid-state switches to produce a unipolar/bipolar high-voltage nanosecond pulse with an adjustable rise/fall time. The proposed topology consists of 2 arms, each of which contains several HB-MMC submodules. The capacitors of each arm are charged with a positive voltage and negative voltage in parallel. By controlling the discharging sequence of the two arms, a unipolar or bipolar pulse can be generated. For each arm, by setting the switching sequence of the MOSFETs, the number of capacitors inserted into the discharging circuit can be controlled to allow a multilevel pulse to be generated. The rise/fall time of the output pulse can be adjusted by changing the number of levels and the duration of each level. Detailed illustrations of the proposed configuration and its operational concept are presented. Experimental results for a scaled-down prototype are presented to validate the concept.