Analysis of three-level neutral point piloted power converter topology

This paper deals with three-level topology of neutral point piloted converters (3L-NPP). These converters can be realized in two variants. The first one is represented by one power semiconductor switch only placed in the top and bottom part of an output leg of a half bridge representing a phase of a three phase converter; the second one is represented by two serial connected semiconductor switches in top and bottom part of the converter leg. These topologies are often compared with neutral point clamped converters but not between themselves. Therefore, the analysis of those topologies is performed in detail in this paper and furthermore, they are compared with a standard two level voltage source converter (2L-VSC) in the point of view of converter losses and output quantities distortion