Novel control strategy of traction converter with medium frequency transformer

Abstract

This paper describes research into a novel control strategy of traction converter for the AC-Trolley Line with the medium frequency transformer (MFT). Attention is given to the problematics of finding a suitable control algorithm that will provide minimal magnetic saturation of MFT. This could be ensured by variable voltage pulses on MFT input defined by the control algorithm to ensure proper MFT saturation. Special attention is focused on the single-phase matrix converter topology and the best commutation solution. Two basic methods of switch control of the matrix converter are discussed. The first method requires the knowledge of the converter output current polarity and the second method assumes the knowledge of the input voltage polarity. In addition, the article describes the switching method in uncertain states - when the voltage or current cross zero. Moreover, the paper presents a new modular topology with several separate medium frequency transformers. The proposed algorithm is described and implemented in the experimental model.