Configurable front-end converters for multicurrent locomotives operated on 16 2/3 Hz AC and 3 kV DC systems

A configurable converter topology is presented as front-end converter for a locomotive that can be operated as well on a high voltage AC-system as on a medium voltage DC-system. The configurable converter is realized on the base of a multilevel chain, where all modules are fed through reversible and isolated DC-DC stages. The medium frequency transformers used in the isolation stages of the DC-DC converters allow a significant weight reduction of the locomotive, in comparison with the classical low-frequency voltage-transformers. A first solution using hard switching techniques is presented, using a three-times silicon-conversion. A second solution based on ZVT/ZCS techniques is then presented, with the advantage of having ideally only a two times silicon conduction. Prototype modules have been realized with association of diodes and IGBTs in order to provide reverse-blocking devices. First results of the two-stage conversion are also presented.