Study On The Harmonic Model Of Electrified Railway And Software Development

Along with the scale enlargement of electrified railway, the traction power supply system is expanded, and the impact of electrified railway on the power quality of power system is also increasing. The traction load of electrified railway is a single-phase load, which breaks the symmetrical operation conditions of power system. Because of power electronic rectifier equipment in electric locomotives, while traction substations are connected to the power grid, a large amout of harmonics and negative sequence current is injected into the electric system which seriously endanger the safety and reliability of the operation of the public power grid without proper measures. Based on the present situation and requirement of traction power supply system in China, the algorithm, program development and engineering applications of harmonic and negative sequence current calculation about electrified railway are studied. The major work and contributions are as follows:(1) The principle of the three-phase-two-phase system transformation is researched. The three-phase equivalent model of traction power supply system including the traction transformer equivalent leakage reactance model, the traction load and compensation equivalent models is established. Traction power supply system and the three-phase power system are unified in topology by this method.(2) The equivalent mathematical models and passive cureent of traction transformers including single-phase connection, V/V connection, Yndll connection and Scott connection are analyzed in detail, and commonly used passive filters modelare analyzed as well(3) The program for calculating the harmonic and negative sequence current generated by electrified railway is developed, which can easily consider the traction transformers impedance and the passive power filter connected to the transformers secondary side, thus the accuracy of calculation is improved.(4)The validity and accuracy of the methods proposed in the study are proved by the example of CEPRI-36 and large-scale practical power system calculation.