Electrified Railway Traction Load Negative Sequence Characteristics And Its Negative Sequence Source Modeling Study

The electric locomotive load is assymetrical with high-power,also has the complex changeable running status and randomness, when it works, massive negative sequence current can be produced and poured into the power system through the traction substation.It influences the quality of the electrical wave, poses certain threat to the power system's stable, security and economical operation.Along with the rapid growth of the traction load, the negative sequence contamination of the traction load is concerned by more and more people.Based on Simulink toolbox of the Matlab platform , this article modeled Ss-8 locomotive main circuit and auxiliary circuit , main transformers of the traction substations, then the traction load simulation platform is finished. Through the analysis of conduction process of electric locomotive in different output voltage by rectifying device , and the magnetic weaken of the traction motor in adjusting speed, effectively simulated the locomotive's stepless speed adjusting, through the adjusting of the traction motor load torque,we simulate the operation environment of the locomotive in different slope and wind resistance, etc , From the equivalent circuit and vector diagram, analysed several typical type of the traction transformer's negative sequence characteristics, and through the comprehensive simulation of the traction load simulation platform under different operation conditions and different types of the traction transformer, summarized the negative Sequence characteristics of the traction load.Traction load is a negative sequence source relative to the public grid, it is the source of the negative sequence power flow calculation. Based on the SVM(support vector machine) principle which optimized the parameters by genetic algorithm,with the data collected of traction load by the simulation platform,positive sequence voltage of traction substation bus at the public grid side and traction load's positive sequence current as the excitation,corresponding negative sequence current of traction load which set into the power grid as the response, established the negative sequence source model of the traction load. We used this model to negative sequence power flow calculation and the negative sequence simulation of dynamic operation electric locomotive, it showed good precision and applicability, suitable for engineering simulation application, it also set a foundation to the comprehensive analysis and management for the harm of traction load's negative sequence.The paper finally compiled power flow calculation program which containing traction load , used the negative sequence current source model for negative sequence power flow calculating, negative sequence voltage of each node and negative sequence current of each bar can be get. Thus can take a quantitatively description of the negative sequence influence of the traction load.