Dead-time effect and compensations of three level neutral point clamp inverters for high performance drive applications

Due to the use of high power devices and slow switching frequency in a three level neutral point clamp inverter, the dead-time effect may not be compensated sufficiently fast by using methods developed for the two level inverter. In this paper the dead-time effect in a three level inverter with snubber circuits is analyzed to reveal that it does not only depend on load current direction but also on magnitude. The snubber network also plays an important role in determining the output phase voltage during the dead-time period. Software techniques are proposed to compensate the dead-time effect as soon as it occurs as demanded by the slow switching frequency. Experimental results show their effectiveness