Operational Aspects of an Auxiliary Converter Used in Railway Applications


This paper presents operational aspects of an auxiliary converter for rail traction which was designed, simulated and realized by authors under the frame of an academia-industry project based partnership. The general technical and functional characteristics of the equipment are described. Data representing electrical waveforms ac-quired from the realized converter’s key test points are pre-sented. High harmonic orders (exceeding the 70-th rank) had to be removed through original programs in order to reveal the significant low harmonic order components. The instantaneous values representing the pollution with har-monic orders were evaluated, along with the components oscillating at the fundamental frequency. Highly variable levels of noise were revealed. Unlike the current waveforms from the analyzed converter’s output, the phase voltages preserved a significant content of harmonic distortions after the removal of harmonics higher than 70. Therefore an analysis based on the Fast Fourier Transform was per-formed. Most significant power quality indices were com-puted for cutoff frequencies corresponding to the harmonics from the set {40, 70 and 80}. Harmonic spectra for phase currents, voltages, active and reactive powers were also rep-resented, along with the phasor diagram. Filtering of all frequencies over the 40-th harmonic was revealed to be a good solution for electromagnetic compatibility compliance. images