弓网电弧对牵引传动系统电气特性的影响

Influences of Pantograph-catenary Arc on Electrical Characteristics of a Traction Drive System

随着列车运行速度的提高,弓网离线及离线电弧的发生率大幅上升,对牵引传动系统电气特性的影响日益显著,因此有必要研究弓网电弧对牵引传动系统电气特性的影响。为此,考虑了离线电弧的演化过程,建立了牵引传动系统仿真模型;研究了不同弓网离线时间下弓网离线对牵引传动系统电压特性的影响,并分析了离线过程中不同阶段的电压谐波情况。研究结果表明：弓网离线时间较长且在电弧熄灭的情况下,弓网离线对牵引传动系统电气特性的影响最严重;从电压方面来看,弓网离线时间为300 ms的工况下,熄弧后车载变压器高压侧出现的过电压值为47.5 k V,牵引变流器直流侧电压快速降为零,在离线恢复时产生的过电压值可达到6.4 k V,会对其中的电力电子器件产生严重冲击;从波形畸变程度来看,车载变压器高压侧电压的总谐波畸变率（total harmonic distortion,简称为THD,符号为λTHD）随着时间的延长而增大,畸变的电压输入牵引变流器,增加了其控制难度,恶化了变流质量。综上所述,弓网离线时间越长,弓网离线对牵引传动系统交直流侧电压的影响就越大,进而威胁到牵引传动系统电气设备的安全稳定运行。

With increase of train speed, the occurrence rate of pantograph-catenary disconnection and arc increases greatly, which influences the electric characteristics of traction drive system more obviously. Therefore, it is necessary to study the influences of pantograph-catenary arc on the electrical characteristics of the traction drive system. We built a simulation model of traction drive system by considering the evolution process of disconnection arc. Based on the model, the influences of pantograph-catenary disconnection on the electrical characteristic of traction drive system was studied with different pantograph-catenary disconnection time, and voltage harmonic of different periods was analyzed in the process of the disconnection. The results show when the arc is extinguished under a longer pantograph-catenary disconnection time, the impact induced by pantograph-catenary disconnection on the electrical characteristics of the traction drive system is most serious. From the perspective of voltage value, when the arc is extinguished for a pantograph-catenary disconnection time of 300 ms, the primary side of vehicle transformer presents an overvoltage whose value is 47.5 k V, and DC link voltage of traction converter drops to zero quickly. When the pantograph and catenary contact well again, a high overvoltage whose value reaches to 6.4 k V appears on the DC link, which has a serious impact on the power electronic devices of traction converter. From another aspect of waveform distortion degree, the total harmonic distortion（THD） of primary side voltage of vehicle transformer increases with the increase of time. The distorted voltage inputted to traction converter increases its control difficulty and distorts the quality of converting current. Above all, longer pantograph-catenary disconnection time induces greater impact of the AC and DC measurement voltage of the traction drive system, threatening the safety and stable operation of the electrical equipment of the traction drive system.