Research And Suppression Of High-order Harmonics In Electrical Railway

With the rapid development of Chinese economy and high-speed rail industry,people pay more attention to the efficiency and security of railway.Recently,cross-traffic electric locomotives have been used greatly on domestic electrified railways.There are some advantages of cross-traffic electric locomotives,such as high power factor,relatively small harmonic current distortion rate,and large traction power.Due to the characteristics of an in-line electric locomotive itself,if the harmonic distribution range injected into the traction power supply system increase,the harmonic content in the high-frequency band will also increase.If the harmonic frequency of the high frequency band is stacked with the natural frequency of the traction power supply system,the harmonic resonance phenomenon will occur.Besides,the harmonic resonance may destroy the electric power supply equipment and even the normal operation of the electrified railway.Therefore,it is necessary to analyze the principles and characteristics of the traction network current transmission as well as the harmonic resonance suppression methods.This paper has analyzed the harmonic resonance characteristics of traction power supply system theoretically,and introduced the series resonance and parallel resonance mechanism,also classified the harmonic model of traction network transmission line and selected the harmonic model of transmission line that based on the equivalent ? model.This paper also searched for method of the harmonic frequency of the transmission line harmonics and established equivalent model of the transmission line through state variable analysis method.The harmonic current propagation characteristics of the electrified railway traction network are analyzed.Based on the existing research,the impedance and capacitance parameters of the traction network transmission line are calculated and reduced respectively to create the equivalent circuit model of the traction power supply system.The harmonic current amplification model is obtained,and the harmonic current propagation of the traction power supply system can be simulated and analyzed to obtain harmonic propagation characteristics of the traction network.Carnet joint simulation model is built and the coupling characteristics of the vehicle network are studied.The composition of the traction power supply system and the main power supply methods are introduced.The MATLAB software is used to create the simulation model of the traction power supply system,and its correctness is verified.The traction drive of the electric locomotive system was introduced and a CRH2 electric locomotive simulation model was created.Then,a car-net joint system was set up for simulation analysis.This paper studies the method of restraining harmonic resonance of car network system,introduces the main methods and principles of harmonic resonance of car network system,compares the advantages and disadvantages of active power filter and passive power filter and the second-order damping high-pass separately.The filter and the wave-blocking high-pass filter were designed,and the two filters were added into the vehicle network coupling system for simulation analysis,and the harmonic suppression effect was compared.