Analytical Calculation of Supply Current Harmonics Generated by Train Unit

Analytical model of 3 phase converter traction drive with 2 drive unit supplied from 3 kV DC line is analyzed. The harmonics generated by the converter system injected into the supplying line are determined in analytical way. The calculation method is based at the generalized theory of static converter described in the literature [3,4,5,6,7,8]. The calculation results achieved in that way are compared with the measuring made in traction drive realized in the praxis. The generation of harmonic in traction drive system, independent of the complexity of the system, can be describe in closed analytical way. The analytical description allows systematic investigation of the effects connected with the propagation of the harmonics in the drive system and the environment of the system. The harmonics of the system can be divided into three groups of harmonics. To the first group belongs harmonics depending on the internal properties of the substation, its symmetry and the accuracy of the substation transformer. The harmonic of this group are positioned on the harmonic raster of the supplying network. The second group of harmonic is generated by the 3 phase converter traction drive. Harmonics of this group are depending on the operating point of the traction converter, (the stator frequency of the traction motor) and are sliding along the harmonic raster of line frequency. The third group of harmonics is generated trough the convolution of the both previous type of harmonics.