Voltage Stress Reduction for New 3L-ANPC Modulation Scheme Using Both Current Paths in Zero State

Abstract:
Various modulation schemes exist for the Active Neutral Point Clamped (ANPC) inverter that aim to distribute the power loss more evenly across all switches. This paper introduces a modulation scheme which uses both current paths in zero state simultaneously and thus distributes the conduction losses over the paralleled power devices. The switches belonging to the long commutation loop are turned off in zero voltage condition by introducing a dead time before turn on the second n-path or after switching it off respectively. During this modulation scheme an overvoltage occurs on the slow switching IGBTs. Execution of several experiments shows remaining charge carriers in the IGBT as reason. The method given in this paper aims to eliminate remaining charge carriers and decrease overvoltage to acceptable levels.