Abstract
This paper describes research into a novel control strategy of traction converter for the AC-Trolley Line with the middle frequency transformer (MFT). Attention is paid to the problematics of finding a suitable control algorithm that will provide minimal magnetic saturation. This could be ensured by variable pulse widths, determined according to the actual value of input voltage. Special attention is focused on the single-phase matrix converter topology and the best commutation solution. Two basic methods of controlling the switches in the matrix converter are discussed. The first method requires some knowledge of the converter output current polarity and the second method assumes some 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 middle frequency transformers. The proposed algorithm is described and implemented in the laboratory model.DOI: http://dx.doi.org/10.5755/j01.eee.21.5.13318
Highlights
This research has been motivated by our industrial partner's demand to reduce the weight of the electrical equipment of the railway vehicle in order to enhance rated power
High voltage input is reduced by the traction transformer (TT)
Increasing traction transformer frequency can be realized by implementing the special high-voltage input frequency converter (HVC) [2], [3], [6]–[11]
Summary
This research has been motivated by our industrial partner's demand to reduce the weight of the electrical equipment of the railway vehicle (mainly the bulky line traction transformer [1] found on board of railway vehicles) in order to enhance rated power. Due to very low supplying frequency (i.e. traction systems in Europe use trolley voltage 25 kV/50 Hz or 15 kV/16.7 Hz), the traction transformer is very bulky (for example 15t for rated power 6.4 MW). On traction force in modern high-speed locomotives and special purpose vehicles (electric multiple units, tram-train for AC-Trolley Line etc.). The recent trend in research into new traction converter topologies for multi-system locomotives, trains, suburban units and vehicles supplied by AC electrification systems is strongly oriented towards the reduction of weight and emphasizes dimensions of a new generation of electrical equipment used in these vehicles [2]–[11]. Increasing traction transformer frequency can be realized by implementing the special high-voltage input frequency converter (HVC) [2], [3], [6]–[11]. Multisystem vehicles for all four traction systems used on European railroads – the trolley system 1.5 kV DC connection of output traction converters VSI is parallel (3 kV DC trolley system is realized by serial connection)
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