Analysis of Multilevel Electronic Balancer for AC Traction Substation with PS-PWM

The main goal of this paper is the analysis of an behavior for the electronic balancer of the AC traction substation. This balancer consists of three delta connected multilevel cascade H-bridge converters. The employed phase-shifted pulse width modulation causes the significant decrease of the current ripple due to multilevel nature of the voltage at the converter AC terminals. This paper describes the basic level of modulation technique for single H-bridge cell and analyzes low harmonic interferences of the converter. These results are extended to twelve cells H-bridge multilevel converter with 250 Hz switching frequency. The results of the analysis are based on a created model of the multilevel converter with the nominal power of 12.5 MVA (for traction substation use).