Traction power systems for electrified railways:evolution,state of the art,and future trends

Traction power systems(TPSs)play a vital role in the operation of electrified railways.The transformation of conventional railway TPSs to novel structures is not only a trend to promote the development of electrified railways toward high-efficiency and resilience but also an inevitable requirement to achieve carbon neutrality target.On the basis of sorting out the power supply structures of conventional AC and DC modes,this paper first reviews the characteristics of the existing TPSs,such as weak power supply flexibility and low-energy efficiency.Furthermore,the power supply structures of various TPSs for future electrified railways are described in detail,which satisfy longer distance,low-carbon,high-efficiency,high-reliability and high-quality power supply requirements.Meanwhile,the application prospects of different traction modes are discussed from both technical and economic aspects.Eventually,this paper introduces the research progress of mixed-system electrified railways and traction power supply technologies without catenary system,speculates on the future development trends and challenges of TPSs and predicts that TPSs will be based on the continuous power supply mode,employing power electronic equipment and intelligent information technology to construct a railway comprehensive energy system with renewable energy.

Research on the longitudinal protection of a through-type cophase traction direct power supply system based on the empirical wavelet transform

This paper proposes a longitudinal protection scheme utilizing empirical wavelet transform(EWT)for a through-type cophase traction direct power supply system,where both sides of a traction network line exhibit a distinctive boundary structure.This approach capitalizes on the boundary’s capacity to attenuate the high-frequency component of fault signals,resulting in a variation in the high-frequency transient energy ratio when faults occur inside or outside the line.During internal line faults,the high-frequency transient energy at the checkpoints located at both ends surpasses that of its neighboring lines.Conversely,for faults external to the line,the energy is lower compared to adjacent lines.EWT is employed to decompose the collected fault current signals,allowing access to the high-frequency transient energy.The longitudinal protection for the traction network line is established based on disparities between both ends of the traction network line and the high-frequency transient energy on either side of the boundary.Moreover,simulation verification through experimental results demonstrates the effectiveness of the proposed protection scheme across various initial fault angles,distances to faults,and fault transition resistances.

New generation traction power supply system and its key technologies for electrified railways

Unlike the traditional traction power supply system which enables the electrified railway traction sub- station to be connected to power grid in a way of phase rotation, a new generation traction power supply system without phase splits is proposed in this paper. Three key techniques used in this system have been discussed. First, a combined co-phase traction power supply system is applied at traction substations for compensating negative sequence current and eliminating phase splits at exits of substations; design method and procedure for this system are presented. Second, a new bilateral traction power supply technology is proposed to eliminate the phase split at section post and reduce the influence of equalizing current on the power grid. Meanwhile, power factor should be adjusted to ensure a proper voltage level of the traction network. Third, a seg- mental power supply technology of traction network is used to divide the power supply arms into several segments, and the synchronous measurement and control technology is applied to diagnose faults and their locations quickly and accurately. Thus, the fault impact can be limited to a min- imum degree. In addition, the economy and reliability of the new generation traction power supply system are analyzed.

Industrial frequency single-phase AC traction power supply system for urban rail transit and its key technologies

To avoid stray current and maintain the benefit of no phase-split in the DC traction power supply system, an AC traction power supply system was proposed for the urban public transport such as metro and light rail transit. The proposed system consists of a main substation （MSS） and cable traction network （CTN）. The MSS includes a single-phase main traction transformer and a negative-se- quence compensation device, while the CTN includes double-core cables, traction transformers, overhead catenary system, rails, etc. Several key techniques for the proposed system were put forward and discussed, which can be summarized as （1） the power supply principle, equivalent circuit and transmission ability of the CTN, the cable-catenary matching technique, and the selection of catenary voltage level; （2） the segmentation technology and status identification method for traction power supply network, distributed and centralized protection schemes, etc.; （3） a power supply scheme for single-line MSS and a power supply scheme of MSS shared by two or more lines. The proposed industrial frequency single-phase AC traction power supply system shows an excellent technical performance, good economy, and high reliability, hence provides a new alternative for metro and urban rail transit power supply systems.

A preventive opportunistic maintenance method for railway traction power supply system based on equipment reliability

Conventional maintenance mode for the traction power supply system(TPSS)is to perform scheduled regular maintenance activities for power supply equipment,while such maintenance mode may result in undue maintenance tasks and low efficiency due to different degradation processes of different sorts of equipment.To address this problem,this paper introduces a preventive opportunistic maintenance(POM)method for TPSS based on equipment reliability.Firstly,a POM model is established by considering the equipment reliability degradation process based on Weibull distribution.Then,by considering the total power outage time in the planned operation cycle of TPSS as the optimization objective,the optimal maintenance scheme of TPSS is formulated by iterative method of maintenance strategies.The proposed method is verified by introducing practical maintenance strategies and fault record data of the traction transformer,circuit breaker and disconnector in an actual TPSS of a railway administration.Results show that the presented method can make full use of the existing fault data to develop a POM scheme for TPSS.It can improve maintenance efficiency and reduce power outage time,providing guidance to formulate scientific maintenance strategies for TPSS.

Test Analysis of Traction Battery Peak Power

The test process of electric vehicles (EVs) traction battery peak power is analyzed in detail. Aimed at a special “traction” design of versatile battery—HORIZON~ C~2M Battery, the features are introduced. According to the peak power test schedule, the test parameters of HORIZON~ C~2M Battery are calculated and the charging and discharging experiments are carried out. The sustained (30 s) discharge power capability of battery at 2/3 of its open circuit voltage at each of various depths of discharge is determined. The dynamic internal resistance under peak power test is established. Considering the temperature impact during discharging, the peak power capability at each of various depths of discharge is corrected. The correctness of peak power test is validated by combining theory analysis with test results.

Improved fault location method for AT traction power network based on EMU load test

The autotransformer(AT)neutral current ratio method is widely used for fault location in the AT traction power network.With the development of high-speed electrified railways,a large number of data show that the relation between the AT neutral current ratio and the distance from the beginning of the fault AT section to the fault point(Q-L relation)is mostly nonlinear.Therefore,the linear Q-L relation in the traditional fault location method always leads to large errors.To solve this problem,a large number of load-related current data that can be used to describe the Q-L relation are obtained through the load test of the electric multiple unit(EMU).Thus,an improved fault location method based on the back propagation(BP)neural network is proposed in this paper.On this basis,a comparison between the improved method and the traditional method shows that the maximum absolute error and the average absolute error of the improved method are 0.651 km and 0.334 km lower than those of the traditional method,respectively,which demonstrates that the improved method can effectively eliminate the influence of nonlinear factors and greatly improve the accuracy of fault location for the AT traction power network.Finally,combined with a shortcircuit test,the accuracy of the improved method is verified.

Investigation of Power Factor Behavior in AC Railway System Based on Special Traction Transformers

The single-phase traction load has essentially an unbalance characteristic at the Point of Common Coupling (PCC), which injects harmonic into the utility grid. In this paper, the effect of harmonic distortion and unbalance loading are investigated simultaneously for electrical railway systems. Special traction transformers (i.e. single-phase, V/V, Wye-Delta, Scott, and Le Blanc) are used between the utility grid and the traction load. For analysis, different defini-tions of power factors are considered, which are presented by IEEE Std.1459. The detailed simulation study is made with MATLAB/SIMULINK program to represent the impacts of harmonic components and unbalance loading on the power factor behavior in the Electrical Railway systems.

Comparison of Three Modes of AT-fed Traction Power Networks

The features of three modes of AT-fed traction power networks (TPNs) have been briefly described in the existing literature, which is not adequate yet. In this paper, these three modes of TPNs are compared mainly on TPN capacity, transformer capacity, rail potential and voltage level, etc., and conclusions are drawn.

A fast power control method based on high-speed communication for the continuous co-phase traction power system

Continuous co-phase traction power system is an effective method to eliminate neutral sections and provide high quality power for both the public grid and the catenary.The substations have the ability to provide cooperative support to each other to reduce capacity and improve system reliability.A fast power control method for substations is needed due to rapid load changes and low overload capability of the system.This paper proposes a fast power control method based on high-speed communication between substations,with additional transient power control to significantly improve the dynamic response of the system.

青藏线双源动车组黏着适应性研究

为了分析运行效率更高的双源动车组在青藏线(格尔木—拉萨段)运行的可行性,建立机车动力学模型并进行了验证;采用动力学方法研究了双源动车组机车(动车)和青藏线成熟运营的HXN3内燃机车在直线段、曲线段和坡道上的牵引黏着系数、牵引力、蠕滑率与速度之间的关系;通过对比2个机车的动力学响应,验证牵引工况下双源动车组的黏着特性.通过分析可以发现:1)机车的牵引黏着系数与机车的牵引力成正比,当车速在40~120km/h时,双源动车组机车的黏着系数由0.19降低至0.09,黏着富裕度则由59.0%提高至85.7%;2)在直线段和坡道情况下,双源动车组的黏着富裕度均大于HXN3机车,对适应恶劣外界环境引起的轮轨黏着下降能力更强,对高原环境的适应性更优;3)曲线段,忽略结构引起的黏降差异,R300m曲线时,双源动车组和HXN3型机车的黏降幅度分别为6.3%和6.8%,R800 m曲线时,HXN3型机车曲线黏降幅度为3.0%,而双源动车组低于限值,可以保证有足够的黏着.

轨道交通直流干扰的车-地-网动态耦合仿真

针对中性点接地变压器直流偏磁电流受轨道交通动态杂散电流泄漏和段场接地影响的问题,综合考虑多列车运行工况,建立杂散电流分布扩散的车-地-网耦合模型,并采用复镜像法计算大地电位;定义接地网的自电阻系数和互电阻系数,建立直流偏磁电流与大地电位的耦合关系,根据杂散电流侵入路径的拓扑结构,构建大地电位和直流偏磁电流的场路耦合模型;设计轨道交通杂散电流侵入电网的缩比模拟试验,并通过试验与模型计算进行验证.研究结果表明:试验结果和模型计算之间的最大误差为8.41%;钢轨对地过渡电阻从3.00Ω•km增大到15.00Ω•km,直流偏磁电流的绝对平均值减小82.4%;在车辆段和正线之间采用阻断式连接装置比采用单向导通装置减小23.45%的直流偏磁电流.

新型电缆贯通供电系统短路特性分析

新型电缆贯通供电系统能够实现长距离输电、减少电分相数目,但两级供电模式将导致该系统结构复杂.为研究电缆贯通供电系统短路特性,首先,建立单位长度的牵引电缆和接触网-钢轨的二端口网络参数,将各个子网络级联等效成1个二端口网络,进而转化为Ⅱ型电路,实现牵引电缆和接触网-钢轨任意长度的分布参数建模;由于接触网短路后导致机车电压下降,基于车网耦合关系采用迭代计算求解短路电流电压,仿真验证计算方法的准确性.最后,解析不同短路类型的电气特性,重点分析分布电容对短路电流、电压的影响.研究结果表明:分布电容会引起短路电流增大,且在不同短路情况下均造成牵引变压器输出电压增加;接触网短路电流由两侧牵引变压器共同提供,距短路点越远提供的电流越少;电缆相间短路对非故障回路机车运行影响最大.

基于国外经验的城市轨道交通牵引供电系统发展路径研究

[目的]在当前城市轨道交通智能智慧化、绿色低碳化的发展背景下,牵引供电系统作为城市轨道交通的“心脏”,其升级换代对于实现城市轨道交通的绿色智慧发展至关重要,有必要对牵引供电系统未来的发展路径展开研究,以推动其技术革新与产业升级。[方法]总结德国、日本、法国等国外典型国家在优化轨道交通牵引供电系统配置、新能源利用、数字信息化等方面的前沿技术和创新成果;从推广牵引供电系统创新成果应用,加大新能源在牵引供电系统中的应用,以及建立智能化牵引供电系统管理平台等3个维度出发,探讨我国城市轨道交通牵引供电系统的创新发展路径。[结果及结论]提出的城市轨道交通牵引供电系统创新发展路径,可推动实现牵引供电系统升级换代,进一步助力城市轨道交通绿色化、智慧化发展。

城市轨道交通牵引供电系统双向变流装置设计方案及综合效益

[目的]目前双向变流装置在我国城市轨道交通(以下简称“城轨”)牵引供电系统中处于推广阶段,存在多种配置方案且有实际应用,需综合评估各方案优劣,统一技术标准,同时进行全生命周期效益分析,为工程应用提供决策依据。[方法]基于双向变流装置在设备功能、直流牵引供电能力、综合节能、电能质量等方面的优势,从用房面积、设备投资、电能质量、经济效益及可靠性等方面,对我国现有的5种双向变流装置配置方案进行技术经济比选,给出推荐配置方案。以某城轨正线为例,分析了双向变流装置在节能、无功补偿、杂散电流防护等方面的全生命周期综合效益。[结果及结论]经综合比选,双向变流装置推荐采用1套二极管整流机组+1套双向变流机组方案,其全生命周期成本最低。预计该城轨正线20年全生命周期总成本减少256.8万元/km。

机械变速拖拉机牵引试验特性研究和分析

牵引试验是农业拖拉机试验鉴定中最重要的试验之一,且牵引功率是衡量拖拉机动力性能和经济效益的重要技术指标。为此,对不同档位下拖拉机行驶速度、牵引功率、牵引力和滑转率等参数进行测量,结合测量得到的数据结果绘制参数关系曲线图,分别绘制了牵引力和行驶速度、牵引功率和行驶速度、牵引力和驱动轮滑转率、牵引功率和牵引比油耗的曲线变化图。同时,运用数学运算得出各参数间一次线性和二次多项式的拟合方程,对比决定系数R2值,得出最真实的回归方程。试验结果表明:得出的回归方程对研究农业拖拉机牵引功率试验有一定的指导和应用价值,可对牵引功率试验中的测量参数进行提前预测。

基于背靠背变流器的牵引变电所群供电系统负序集中补偿方案

针对牵引变电所群供电系统导致的外部电源公共连接点处三相电压不平衡问题,提出了一种基于背靠背变流器的集中式有功型负序补偿方案。该方案的补偿装置可实现容量配置的最优解,且负序补偿的同时还可兼顾无功补偿。介绍了基于背靠背变流器的牵引变电所群供电系统拓扑结构;根据牵引变电所群供电系统及补偿装置间的功率关系分别阐述了该方案的负序、无功补偿原理,推导了补偿装置计算容量表达式,分析了补偿装置计算容量变化规律;为保证补偿装置快速、稳定运行,提出了适用于负序、无功补偿的双闭环控制策略;通过仿真证明所提方案的有效性和可行性。结果表明:所提方案对牵引变电所群供电系统具有良好的负序、无功补偿效果,且补偿装置容量配置实现了最优解,具有较强的经济性与应用潜力。

群组列车牵引供电系统过分相合闸过电压特性分析

群组列车运行过程中会频繁经过分相区,产生的合闸过电压将对牵引供电系统以及列车高压设备箱造成严重的绝缘损害。为定性分析群组列车的合闸过电压特性,首先,根据电路等效简化原则,建立群组列车牵引供电系统的等效简化动态电路,通过提出合理的假设条件求解出合闸瞬间列车端电压的表达式,从定性关系上揭示了合闸过电压的形成原因;其次,基于群组列车牵引供电系统暂态模型,分析了不同列车数量、分布位置以及运行功率对群组列车合闸过电压的作用机制;最后,在PSCAD/EMTDC中搭建仿真模型,验证了理论分析结果的正确性。结果表明:群组列车数量越多、运行位置越集中、牵引功率越大,就会使得合闸过电压峰值越小。该结果可有效指导群组列车过分相合闸过电压的抑制,降低群组列车经过分相区时产生的合闸过电压。

牵引变电所功率因数提升方法研究

铁路开通运行初期牵引变电所功率因数远低于电力系统要求,导致增加了变电所力率电费。为提升牵引变电所功率因数,以衢宁铁路某牵引变电所为例计算并验证了牵引变电所各馈出线路的空载无功,在理论上对比了退出部分馈线与磁控电抗器补偿两种功率因数提升方法的效果。结果表明对于该牵引变电所,退出部分馈线的方法并不能使功率因数达到0.9,而磁控电抗器补偿法能使功率因数接近1。磁控电抗器补偿法实施完成后的实际功率因数验证了这一结果。牵引变电所在进行功率因数提升方案研究时应结合实际线路、行车组织特点,综合考虑不同方案。

双源制磁浮式工程车总体设计

为解决现有橡胶轮式磁浮工程车运行速度低、噪声大、检测维护效率较低等问题,满足长距离磁浮线路的检测维护需求,文章提出了一种新型磁浮式工程车的技术方案,着重从提升车辆运行速度和检测维护效率等方面开展研究。该工程车采用“磁浮制式”替代“橡胶轮制式”的技术模式,采用“蓄电池+供电轨”双源制动力替代内燃动力,设计速度100 km/h,可以实现快速带电检测和无电维护的功能需求,为长浏、长宁等长距离磁浮线路的检测维护提供了一种新的系统解决方案。