Comparison of Three-Level and Two-Level Converters for AFE Application

SiC-MOSFET based 2-level converters can be a promising topology for Active Front End (AFE) application in electric drives. The possibility of high switching frequency will make the grid filters smaller. Grid filters are used for EMC and power quality issues. However, there are practical limitations for increasing the switching frequency such as dead time in the gating signals, sampling requirements, and electro-magnetic interference (EMI) considerations, besides the need for high frequency magnetic material for the LCL line filter. However, 3-level converters provide the opportunity to switch at a lower frequency and also reduce the filter size compared to a 2-level IGBT converter. Three-level converters can be built using low voltage rated modules with lower switching losses and reduced cost compared to SiC based 2-level converters. In this paper, a comparison between 3-level converters and 2-level converters is presented focusing on power loss, filter size and application benefits.