New Configuration of Traction Converter With Medium-Frequency Transformer Using Matrix Converters

This paper presents a new configuration of a main traction converter with a medium-frequency transformer (MFT) using matrix converters intended for locomotives and particularly for suburban units supplied by a 25-kV/50-Hz and/or 15-kV/16.7-Hz ac electrification system. Single-phase matrix converters are employed in the primary medium-voltage converter which is directly connected to the ac trolley line. The output of the primary ac/ac converter supplies the primary side of the MFT. The proposed MFT-based topology of the traction converter replaces the bulky main line transformer found on board railway vehicles. Particularly in countries with a catenary of 15 kV/16.7 Hz, very low catenary frequency results in huge and heavy traction transformers. The developed topology is a power electronics solution that considerably reduces weight and losses in a traction propulsion system. The proposed converter configuration with cascaded matrix converters on the primary side of the MFT presents a new research direction in the field of traction converters with MFTs. This paper describes in detail the proposed power circuit and the control of the traction converter. The behavior of the traction converter configuration has been analyzed using simulations and experimental tests carried out on a developed low-voltage laboratory prototype of a traction converter with a rated power of 4 kVA. Based on extensive simulation and experimental study, this paper reviews the benefits, drawbacks, and constraints of the developed traction converter configuration.