Electrified Railway Traction Simulation Analysis

Electrical locomotive is a kind of single-phase rectifier load, it brings a lot of harmonic currents and negative sequence currents to the electrical network while operating normally by the traction power supply system. This harmonic and negative sequence components produced by electrical locomotive not only causes added losses and reduce the utilization ratio of the electrical power system, but also influences the stability and security of the electrical power system. This is why harmonic control in traction network system attracts lots of interests.The mathematical and simulation model of power engine in this paper is according to the type SS4 electrical locomotive. The commutation and breakover processes of the rectifier set in different output voltages are analyzed in detail in this thesis. According to the practical information, the simplified model is obtained.In this paper, we pay attention to the problem of harmonics in different power supply systems of electrical locomotive. At present, there are three kinds of traction network in power systems: Scott connection, three phase connection, single phase connection. The Scott connection traction network takes Scott transformer as traction transformer, which covers two kinds of power supply model, auto-transformer mode and booster transformer mode. Three phase connection traction network takes the normal YnD11 connection three phase transformer as traction transformer, phase C is the common end which is connected to railway, phase A and phase B were connected to contact lines. In single phase traction network, single phase transformer is used in power supply system, which covers single-phase connection mode and V-V connection mode. In this paper the upwards three kinds of traction network were introduced in details, the according models were established for simulation, and then we got the harmonics and negative sequence currents of different traction networks. At last we compared the simulation data with data collected in 220Kv substation, which was used to modify the simulation model and parameters.In the end of the paper, in the purpose of reducing harmonics and improve powerquality, considering the harmonic and negative sequence current of the traction network, we bring forward the methods to improve harmonic pollution from electrical railway. The analyses of power supply in different traction network plays an important role to the search of electrified railway in the future.