Electrical characteristics of new three-phase traction power supply system for rail transit

A novel three-phase traction power supply system is proposed to eliminate the adverse effects caused by electric phase separation in catenary and accomplish a unifying manner of traction power supply for rail transit. With the application of two-stage three-phase continuous power supply structure, the electrical characteristics exhibit new features differing from the existing traction system. In this work, the principle for voltage levels determining two-stage network is dissected in accordance with the requirements of traction network and electric locomotive. The equivalent model of three-phase traction system is built for deducing the formula of current distribution and voltage losses. Based on the chain network model of the traction network, a simulation model is established to analyze the electrical characteristics such as traction current distribution, voltage losses, system equivalent impedance, voltage distribution, voltage unbalance and regenerative energy utilization. In a few words, quite a lot traction current of about 99% is undertaken by long-section cable network. The proportion of system voltage losses is small attributed to the two-stage three-phase power supply structure, and the voltage unbalance caused by impedance asymmetry of traction network is less than 1 parts per thousand. In addition, the utilization rate of regenerative energy for locomotive achieves a significant promotion of over 97%.