Experimental investigation of parasitic side effects in MOSFET-based multilevel inverter for electric vehicle applications

摘要

Recently, multilevel inverters (MLIs) have been intensively investigated due to the high potential this technology offers compared to traditional inverters. In order to fulfill system requirements in terms of efficiency and losses, a major research goal is to achieve a topology with highest functionality while simultaneously keeping the number of inserted switches as low as possible. However, the developed MLI topologies can exhibit side effects such as parasitic commutation paths during switching processes. Since these effects have not been the focus of many MLI studies to date, this publication experimentally investigates a special MOSFET-based MLI topology with regards to side effects that occur during one representative switching operation. It is found that switches actually not actively involved in the switching scenario carry a parasitic current by performing a self-turn-on. For the switching transition concerned, a total of four different parasitic commutation paths are identified. Thereby, a maximum parasitic drain current of more than 13 A is measured based on a load current of 40 A. The measurement findings obtained for a load current of 80 A show that the drain currents appearing during self-turn-on rise proportionally with the load current, whereby the amplitude of a resonant ringing is not affected.