Research On Negative Sequence And Harmonic Method For Traction Power Supply System Of High Speed Railway

In recent years,China has achieved most of the railway electrification,high-speed railway operating mileage has exceeded 10 thousand km;along with the popularity of high-speed railway,high-speed railway is changing people's life,fast and comfortable experience so that more and more people enjoy the convenience of high speed railway.AC-DC-AC electric locomotive is generally used in high speed railway,although the pulse width modulation technology makes the electric locomotive running at unity-power factor,but it will also produce a wider spectrum of harmonic.Because of widely using single-phase power supply and the increase of traction load power compared with the traditional electrified railway,the negative sequence current increases and the three-phase voltage of the public power grid is unbalanced.Therefore,through the analysis,it is found that the power quality problems of high speed railway are mainly negative sequence and harmonic.This paper analyzed the characteristics of negative sequence and harmonic in traction power supply system of high speed railway.At first,his paper introduced the composition of high-speed railway traction power supply system,and compared several traction power supply models according to the principle of the traction power supply system,the current domestic and foreign high-speed railway is more with AT power supply,in order to meet the high speed,high power demand;and then through the analysis of types and characteristics of electrified railway traction transformer,concluded that the V/V transformer can satisfy the characteristics of high-speed railway traction.Secondly,this paper analyzed the negative sequence characteristics of high-speed railway,introduced the application of symmetrical component method in traction power supply system,introduced the concept of negative sequence current of traction power supply system,because of the high speed railway traction power supply most used V/V transformer,the analyses of negative sequence problems during operation of high speed in railway was based on V/V transformer.Finally,analyzed the harmonic characteristics of high-speed railway,the whole electric locomotive was nonlinear load,harmonic generation will be correspondingly,and the high speed railway locomotive was controlled by AC-DC-AC converter,locomotive converter had become the main harmonic source,so the research object was the four quadrant converter principle respectively and low harmonic,harmonic;through the analysis of the traction power supply system of high-speed railway negative sequence and harmonic characteristics,built a theoretical foundation for the comprehensive compensation system.In order to solve the problem of negative sequence and harmonic in traction power supply system of high speed electrified railway,a type of integrated control scheme based on the two-wire three-phase converter was presented in this paper.The scheme included the active part of the two-phase three-wire converter,the passive part of thyristor controlled reactor and thyristor switched capacitor,through the effective use and coordination control of the passive part,to reduce the capacity and cost of the active part.Through the real-time detection method of harmonic and negative sequence and active compensation strategy and active compensation strategy of deadbeat control,to improve the effect of comprehensive treatment on the quality of electric energy.Finally,this paper built the simulation model of two-phase three-wire converter and compensation control system,the simulation results shows that the proposed control scheme can effectively control negative sequence and harmonic problem generated by the high-speed railway load.