图 1 音频轨道电路信号系统
Published:10 July 2024,
Received:10 January 2024,
Revised:27 June 2024
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This paper focuses on mitigating inductive interference caused by the traction systems of rail transit trains on track circuits. The initial analysis explored the interference mechanisms through inductive coupling. Based on the real layout and wiring of DC traction systems in metro applications, a 1:1-scale induced voltage testing platform for traction systems was built, as the first of its kind in domestic laboratories. This platform was employed to simulate transient inductive interference generated by train traction systems at the receiving end of track circuits under static laboratory conditions. These simulations revealed the induced voltage levels produced by different interfering components and coupling loops on track circuits, under different operating conditions of the traction systems and various relative positions of the track circuits. Moreover, the coupling circuit formed by the DC chopper and braking resistor during resistance braking was identified the maximum source of inductive interference from metro DC traction systems affecting track circuit systems. Additionally, by analyzing the relationship between the spectrum characteristics of induced emissions from the traction systems and the IGBT switching frequencies for chopping, a spectrum management method was adopted to reassign induced emissions characteristic frequencies of traction systems, resulting in staggered sensitive frequency bands for the track circuits. The experimental results demonstrate the effectiveness of the proposed inductive interference suppression strategy in reducing the risk of inductive interference caused by train traction systems on the track circuits.
traction system;
track circuit;
induced voltage;
DC chopper;
spectrum management
日渐成熟的电力牵引、控制及信号系统促进了世界轨道交通技术的不断发展。欧盟委员会指令96/48/EC明确提出:高速列车服务的前提是基础设施与机车车辆之间的良好兼容性,而该兼容性取决于性能水平、安全性、服务质量和成本[
我国机车车辆与轨道电路的兼容性研究起步较晚,但相较于欧美地区供电和轨道电路制式的复杂性,国内机车车辆与轨道电路在运行兼容性方面有着先天优势[
本文基于机车车辆与轨道电路兼容性中关注较少的感应干扰问题,深入分析车辆牵引系统对轨道电路造成感应电压的作用机制,并设计了一种牵引系统感应电压试验台位模拟真实车辆行驶过程中对轨道电路造成的瞬态感应干扰,便于在牵引系统设计阶段评估感应电压的干扰风险,为后续整车EMC试验阶段的感应电压测试提供正向解决方案。
现代轨道交通系统通常采用音频轨道电路来检测轨道上列车的存在[
图 1 音频轨道电路信号系统
Fig. 1 Audio signal system of track circuit
列车控制室内的轨道电路发射模块产生1个音频频率信号,并通过末端的耦合变压器将该音频信号注入到轨道中,该信号通常由频率、幅度或者编码调制。当轨道电路区间中不存在列车时,音频信号将经过轨道传输后被耦合变压器接收,轨道电路的接收模块通过滤波、放大以及检波电路等检测接收信号。若信号满足该轨道电路的振幅和调制要求,则接收模块将驱动轨道继电器的线圈通电,通电的线圈使继电器吸合,从而完成轨道区间“空闲”检测。当列车进入轨道电路区间时,列车的轮轴将使音频信号分流,若耦合变压器传输到轨道电路接收模块的音频信号低于预设水平,则接收模块将驱动轨道继电器断电,导致继电器断开,从而完成轨道区间“占用”检测。当列车的最后一个车轮离开轨道电路后,信号再次到达轨道电路接收模块,轨道继电器吸合,表示轨道区间“空闲”。音频轨道电路除用于轨道区间的空闲/占用检测外,还包括用于列车速度控制,由列车驾驶室前轴附近的车载天线通过感应拾取轨道上的音频调制信号以读取速度控制指令,速度控制指令通常被编码为调频码。
列车牵引系统对轨道电路的电磁干扰可以分为传导和感应两种模式,可能会造成轨道电路发生错误空闲(False Clear,FC)危险或错误占用(False Occupied,FO)故障[
传导干扰导致的轨道电路FC故障示意如
图 2 传导干扰导致的轨道电路错误空闲(FC)故障
Fig. 2 Track circuit FC failures caused by conducted interference
传导干扰导致的轨道电路FO故障示意如
图 3 传导干扰导致的轨道电路错误占用(FO)故障
Fig. 3 Track circuit FO failures caused by conducted interference
图 4 牵引系统对轨道电路的感应干扰机理
Fig. 4 Inductive interference mechanism of traction system on track circuit
(a) 感应环等效电路
(b) 戴维南等效变换
图 5 牵引系统对轨道电路产生感应电压的等效电路
Fig. 5 Equivalent circuit of inductive voltage generated by traction system on track circuit
感应电压VIN为
(1) |
开展本测试的目的是在模拟轨道电路的条件下,在实验室中再现列车牵引系统的感应发射,得到影响最大的感应电压排放水平,从而能够提前评估列车上线后与轨道电路的电磁兼容性风险,并为车辆感应干扰轨道电路提供正向的解决方案。
如
图 6 牵引系统感应电压测试方法
Fig. 6 Testing method for induced voltage of traction system
图 7 不同运行工况的感应电压测试结果对比
Fig. 7 Comparison of induced voltage testing results under different operating conditions
图 8 不同制动力矩下的感应电压测试结果对比
Fig. 8 Comparison of induced voltage testing results under different braking torques
图 9 不同相对位置时的感应电压测试结果对比
Fig. 9 Comparison of induced voltage testing results at different relative positions
基于上述牵引系统感应电压的测试,可以明确本文研究的地铁直流牵引系统产生感应电压的主要干扰源为直流斩波器-制动电阻的工作回路。最恶劣的运行条件为最大制动力矩的电阻制动模式,最恶劣的运行位置为列车轮轴-轨道-耦合变压器所构成的2个感应环路面积相差最大时,即装载牵引系统的单节列车前轮轴刚驶过轨道电路上方或后轮轴即将驶过轨道电路上方时所对应的运行位置。
图 10 牵引系统感应电压与轨道电路抗扰度频谱特性对比
Fig. 10 Comparison of spectrum characteristics between induced voltage from traction system and track circuit immunity
根据上述对比结果,本文所示的牵引系统感应电压排放水平在部分频段超过了音频轨道电路的抗扰度水平,因此牵引系统存在对轨道电路的感应干扰风险。通过分析牵引系统感应电压的频谱特性,可以发现感应电压的谐波分量由于直流斩波器采用随机开关频率策略表现出不稳定性和分散性,不稳定性是指谐波频率不可控,导致谐波频率与轨道电路工作频段重叠;分散性是指感应电压并不完全集中在每个谐波频率处,还分散在每个谐波频率附近,导致谐波的旁瓣感应电压超过了轨道电路的抗扰度。通过分析轨道电路的抗扰度频谱特性,可以发现每个音频轨道电路的工作中心频率都相差180 Hz的整数倍,而每个音频轨道电路的工作带宽都为±90 Hz,这就造成每个音频轨道电路之间都存在一个“频率间隙”,这种特征是轨道电路设计者在考虑了线路上变电站6脉波整流器谐波(6×60 Hz)可能会通过传导干扰轨道电路而特意实施造成的。因此若能控制牵引系统的感应电压谐波也恰好插入这些频率间隙位置时,就能将感应电压的干扰频谱与轨道电路的工作频谱彻底错开,从而大大降低牵引系统感应干扰轨道电路的风险。
基于此,本文提出了一种基于牵引系统与轨道电路频谱管理的感应电压抑制方式,将牵引系统直流斩波器IGBT开关频率固定为360 Hz。
图 11 基于频谱管理优化后的牵引系统感应电压与轨道电路抗扰度对比
Fig. 11 Comparison of spectrum characteristics between induced voltage from traction system and track circuit immunity after optimization based on spectrum management
本文在模拟轨道电路的条件下设计了一种地铁直流牵引系统感应电压测试平台,可在实验室静态环境中再现列车动态运行中对地面轨道电路产生的瞬态感应干扰,其主要用于在牵引系统设计阶段评估对轨道电路的感应干扰风险,有利于产品的电磁兼容正向迭代设计,提升车辆上线后与轨道电路之间的电磁兼容性。另外,提出了一种基于频谱管理的感应干扰抑制策略,是在深入分析牵引系统感应发射与轨道电路感应抗扰的频谱特性基础上,通过精细化地将干扰谐波分量分配到轨道电路工作频带外来实现的,是一种主动、高效且节约成本的感应干扰解决方案。但这种方式也存在一定的应用局限性,可能与解决牵引系统传导干扰轨道电路需要的抑制策略相矛盾,这就需要全面地考虑牵引系统感应发射和传导发射的频谱特性,分析两种干扰模式对轨道电路影响的主次性,进行更合理的频率分配与优化。
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