An analysis of resonant modes in electric power systems with a traction load
This research aims to investigate resonant modes in electric power systems with a traction load, as well as to study the cross-effect of the traction network and the external power supply network. Powerful non-linear loads represent one of the major reasons for the deterioration of the quality of electricity in high voltage networks. Among these loads are traction power supply systems, which have a significant effect on power supply systems with low values of the short circuit power. In the present study, a Matlab simulation model of a power supply system with a traction load was developed in order to investigate the effect of various parameters of the power supply system, such as the line length and the short circuit power of the external power supply system, on the resonant modes. Additionally, the effect of the spectral composition of currents in electric vehicles on the degree of voltage distortion in the traction and external networks was considered. Analytical expressions were obtained for the resonance frequencies in the "external network - traction transformer - traction network" system. Using the developed simulation model, an analysis of the resonant modes in the power supply system comprising a traction AC network and an external network was carried out. It is shown that voltage distortions in power supply systems with a traction load result from non-sinusoidal currents and the resonant modes of the traction network emerging in the external power supply system. When studying resonant modes, the traction power supply system and the external network should be considered as a single system. The frequency response characteristics of this system have resonance maxima, the frequency and amplitude of which depend on the parameters of both the traction network and the external power supply system.