Identification and Compensation of Converter Non-Linearities of a Multiphase Converter

Multiphase converters are usually composed of several standard 3-phase converters containing Intelligent Power Modules (IPMs). These 3-phase IPM have 6 sets of IGBT-diode pairs having similar switching properties. However, switching properties and/or forward voltage drops of different IPMs can vary significantly, causing an asymmetry in the converter's output. This paper proposes a generic method for identifying these converter asymmetries and estimates an average non-linear voltage drop across each converter leg. These identified voltage drops are experimentally evaluated on a 9-phase multiphase electrical machine (MPEM) supplied from three 3-phase converters, decomposed into four vector spaces and a zero component. With non-linearity correction, the fundamental components of vector spaces 1 and 3 are improved significantly while reducing the rest of the harmonic components.