Adam Szeląg

Electrified transport is strongly assorted, due to long term development and use of diversified solutions, particularly in the scope of electrical engineering considering the following aspects: nominal voltage of a power supply system, vehicles’ main circuits and electrical drives. The problem of compatible work of varied railway systems in mutual interaction regions, despite of various studies, still appears a significant issue. The main purpose of the paper is to present the negative impact of mutual interaction of AC DC railway regions on the electrified railway lines and power grid. A Matlab – Simulink model of the DC and AC traction systems has been developed. In the article, apart from the main problems which could appear in the AC-DC transition zones, the voltage unbalance analysis caused by the AC traction substation is covered and the influence of asymmetric input voltage of the rectifier traction substation on the DC voltage quality is analysed.

This article presents investigations performed on a 25 kV AC system with a Scott transformer simulation model. The model includes an energy quality parameter calculation algorithm with consideration to the train timetable. The simulation results enable an analysis of the energy quality parameters at the point of connection of the traction substation to the supplying grid. The presented tool enables the simultaneous calculation of voltage unbalance and harmonic content. The article presents the results of the energy quality analysis at the substation connection point for the specific location. The simulation results of the energy quality parameters are appraised on the basis of standard EN  50160:2010. The tool may prove helpful in the process of designing electrification systems, especially in the choice of traction transformer and power electronics device mitigating an imbalance and harmonic impact

Due to energy saving policy in the European Union and development of power electronics technology, one might expect an increase in the use of solutions, such as inverters in the substations of the 3 kV DC power supply system. The paper includes a study case of the analysis of traffic conditions on the use of inverters in 3 kV DC system traction substations so as to send back trains’ braking energy from a DC traction power supply to an AC power supply network. The authors presented possible estimated energy savings for a selected railway line. Furthermore, the character of a power waveform and energy available for transferring from a DC to an AC power supply network was discussed as well. The effectiveness of this solution largely depends on the nature of train traffic, so prior to applying the inverters, a detailed analysis is required.