Analysis of track circuits by the flow graphs method

This work describes the analysis and synthesis methods of rail lines, using track circuits models as flow graphs and using the shunt modes parameters as the load current ratio flowing in normal noise influence or shunt modes under multiplicative noise influence.     

Generalized reluctances in eddy current magnetic circuits

Summary The concept of generalized—complex or operational—reluctances is introduced. It is shown that these reluctances simplify considerably the calculation of systems, containing magnetic circuits with eddy currents. Two simple applications are worked out. Some results from a numerical study of the magnetic flux on breaking a telephone relay are given.

---

Übersicht Es wird gezeigt, wie der Begriff eines verallgemeinerten, komplexen oder operatorischen magnetischen Widerstandes (Reluktanz) eine bequeme Behandlung von Problemen über wirbelstrombehaftete magnetische Kreise zuläßt. Zwei einfache Beispiele werden durchgerechnet. Die Ergebnisse einer Untersuchung des magnetischen Flusses bei Ausschaltung eines Telephonrelais werden angedeutet.

---

---

With 6 Figures

---

To the memory of a great teacher of operational calculusHenning Pleijel (1873–1962) Professor of theoretical electrotechnics 1913–1934 at the Royal Institute of Technology, Stockholm

---

Presented at the First International Conference on Electromagnetic Relays, held at Tohoku University, Sendai, Japan, Oct. 8–11, 1963.     

光伏并网逆变器的自抗扰电流跟踪控制

为了使交流电网的输出电流能够更好地跟踪电网电压,并实现最大功率点跟踪控制,分析了光伏并网逆变器的工作原理与控制原理,讨论了自抗扰控制器的控制和参数整定.在此基础上,设计了一种基于自抗扰控制器的并网逆变器电流跟踪控制方法.通过对电流的闭环跟踪控制,实现了单位功率因数运行并向电网馈送电能和电网电流对电网电压的跟踪.实验研究结果表明,采用自抗扰控制器,输出电流、电压稳定快速、超调小,能有效抑制各种扰动,而且系统的启动性能与稳定性能都要优于常规控制器,从而提高了系统的鲁棒性.     

Alternating traction current dynamics in track lines of double-track hauls

The operational stability of track circuits and continuous cab signaling in electrified railway sections is disturbed most often by traction current noises in the track line. They are generated when asymmetrical traction current is produced at the points where track circuit equipment is connected to the tracks or under sending cab coils of continuous cab signaling. From the standpoint of traction current flows, a single-track haul track line can be considered a solitary double-wire circuit with two reciprocally induced singlewire electric circuits. As a result, traction current asymmetry becomes easier to calculate. In the case of double-track hauls, this problem is much more difficult to solve, because the traction network in these hauls additionally includes electrified trackways of adjacent tracks, second contact wire, and longitudinal power supply lines laid on catenary supports. These lines are reciprocally inductive with the considered trackways. The considered hauls are characterized by different distances from each trackway to additional electric lines, for which reason the reciprocal inductances inversely related to these distances are different as well. According to the analysis of the proposed procedure of calculating the traction current asymmetry in the track line, this asymmetry depends not only on electric resistances and specific reciprocal inductances of interlinked singlewire electric power lines, but also on the ratio of currents in these lines. It has been established that the absolute value of traction current asymmetry at a particular point of the track lines is indicated more adequately by the level of impact of traction current asymmetry on the operational stability of track circuits than by the traction current asymmetry factor. The time course of the traction current asymmetry in the track line depends on variations in the ambient temperature, traction current in the rails, and electric resistances in the junctions of parts of track bonds, choke jumpers, and ground circuits of catenary line supports. Additional changes in the traction current asymmetry under sending cab coils occur during train traffic and depend on the inbound resistances of track line sections ahead, as well as on any uneven longitudinal track magnetization.     

升压型Boost-PFC电路的频率反走临界电流控制

临界导通工作模式下的Boost PFC电路在交流输入电压过零点附近出现开关频率过高和过零点交越失真,导致电路开关损耗增加和总谐波失真增大,为此在恒定导通时间控制基础上,提出了一种电流控制频率反走的控制策略.通过在交流输入电压过零点附近将电路从临界工作模式切换到断续工作模式的方式,降低电路在交流输入电压过零点附近开关管的...     

涡流脉冲热像对钢轨滚动接触疲劳裂纹表面长度的量化评估研究

涡流脉冲热像技术作为一种新型的无损检测技术,兼具有感应加热非接触、高效和红外热像快速直观等优点,已应用于不同领域关键部件的缺陷检测与评估.针对钢轨踏面存在的滚动接触疲劳裂纹,利用涡流脉冲热像开展裂纹表面长度量化研究分析.针对滚动接触疲劳裂纹形貌分布复杂这一特点,设计了一套结合裂纹响应提取和裂纹识别的流程.并通过线性拟合...     

双跟踪模式的智能太阳能追踪系统设计

针对提高太阳电池板光电转换率问题,以MSP430F149单片机为控制核心设计了一种太阳能智能追踪系统。采用光电式跟踪和视日运动轨迹跟踪相结合的方式,通过MSP430F149的ADC12检测采集值判断天气情况,晴天采用光电式跟踪,阴天采用视日运动轨迹跟踪。控制系统通过控制双轴步进电机令太阳电池板转动使其始终垂直于太阳光,从而使太能光的利用率大幅度增加。运行表明,系统运行稳定,节能减排,适用于各种小型太阳电池板充电系统。     

Realization of a multiport gyrator using current mirror circuits

A current‐mode signal processing circuit is quite attractive for low supply voltage operation and high‐frequency application. A current‐mode continuous‐time filter consists of simple bipolar current mirrors and capacitors, and are quite suitable for monolithic integration. In this paper, we propose a design for a multiport gyrator using current mirror circuits. Using the multiport gyrator and capacitors, we can simulate passive LC filters. The tuning of the filter frequency can be achieved by adjusting the current of a single dc current course. As examples, third‐ and fifth‐order low‐pass filters are designed for frequencies of 20 to 80 MHz, and SPICE simulation results are shown to demonstrate the effectiveness of the proposed method. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 139(4): 41–47, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.1167     

Improvement of high‐voltage impulses in track circuits with Kasami and LS codes

Track circuit systems based on high‐voltage impulses (HVI) have already been used in China to detect the state of track sections. With the demand for more reliable intelligent transportation systems in recent years, new advances, improvements, and innovations are being applied to their development. This work defines a HVI track circuit based on the encoding of the transmitted signal. Not only 15‐bit and 63‐bit Kasami sequences but also 19‐bit and 71‐bit loosely synchronized codes are applied to encode simultaneous HVI transmissions from 2 emitters. Train occupancy in different parts of the track section is also considered. The quality of the detection is evaluated by means of the correlation bounds. Furthermore, a simulation model for double‐track railways has been developed, which can be dedicated to the evaluation of a suitable signal processing in the track circuit under study. Compared to previous HVI track circuits, as a novelty, this work proposes the use of encoded transmissions to these track circuits, to improve their performance in terms of scanned distance and detection accuracy. The correlation properties of the sequences involved also make feasible to avoid any synchronization link between emitters and receivers, thus providing a significant advantage for later deployment.     

雷电流在线监测系统中噪声干扰的处理方法

针对雷电流在线监测系统中的噪声干扰,提出一种基于模糊神经系统的雷电流波形处理方法.利用所提方法对噪声频率在0.001～10 MHz间变化的雷电流波形进行仿真测试,消噪后雷电流波形的峰值误差小于0.06％,说明所提方法具有很强的抑噪能力.分别用曲线拟合法、小波分析法和所提方法对设备实测波形消噪,分析结果表明,所提方法具有更好的非线性快速逼近性能,得到的波形匹配度高,参数误差最小.     

平行/同杆双回线的单线故障精确测距算法

平行/同杆双回线的一条线路发生故障时,由于非故障线路包含了对侧系统的信息,可以实现利用单端故障信息实现故障测距.介绍平行/同杆双回线的单线故障的一种故障测距算法,算法采用正、负、零序分量的分布参数模型和传输线方程,利用线路单端的故障信息,根据实际故障点的纯电阻特征,得到平行/同杆双回线单线故障时距离测量点的距离.用特征模量分解方法解决同杆双回线的零序分量网络中存在互阻抗和互电纳的难题.算法的精度不受分布电容影响和对端系统阻抗变化的影响.精确计算表明,线路换位(相序排列)对测距精度的影响可以用误差校正曲线或表格的方法校正.     

The average capacitor current method for delay calculation in MOS circuits

The transient response of metal-oxide-semiconductor (MOS) gates is a topic covered in most textbooks on digital integrated circuits and very-large-scale-integration (VLSI) design. One method often used to calculate first-order estimates of gate delays is the average capacitor current method. Using this method, the delay is calculated assuming that the capacitor current is constant and equal to the average of the capacitor current values at the limits of the time interval of interest. In this paper, this method is discussed and compared with other methods of delay calculation using integration and curve-fitting techniques familiar to electrical and computer engineering students. Since the computation of the capacitor current is relatively complicated because it requires the calculation of the MOS transistor currents, for propagation delay calculation there is no benefit in calculating the capacitor current twice. A single current calculation, corresponding to the familiar midpoint integration method, is sufficient to get the same or better accuracy as that of the average capacitor current method. The two-point Gauss quadrature formula is shown to provide excellent results with two capacitor current evaluations.     

On statistical models of the amplitude and the duration of pulsed electromagnetic interference in automatic-control and telemechanic channels of subway lines

On the basis of the results of experimental studies of the interference from the traction current of subway trains, the distribution type of this interference has been established. Approximation of experimental data by an analytical expression based on the Pearson curve family underlies the proposed method. The approximation is performed by calculating the first four distribution moments. The common array of the initial data on the electromagnetic interference is divided into two parts, depending on the type of the rolling stock—either with the switched-on-off tracking regenerative-rheostatic braking system or without it. The 7?10-min recordings of the data on the traction current for trains with or without regenerative braking have been processed. To normalize the experimental data, the mathematical expectation estimate is subtracted from the former and the obtained values are divided by the estimate of the standard deviation. The resulting new data array has normalized properties, i.e., the zero mathematical expectation and a unit standard deviation. Then, from the normalized data array, the first four sampling moments are found, on the basis of which the corresponding Pearson curve is selected. The method underlies the estimation of the distribution density of the pulsed interference amplitude and the duration of the electromagnetic interference pulses. It has been shown that, in all 12 frequency ranges from 50 to 780 Hz that are used in subway automatic control and telemechanical devices, the distribution density of the pulsed interference amplitude and the interference pulse duration can be described by the analytical expression of the β-distribution of the first and second kind.     

基于磁通轨迹特征的变压器励磁涌流识别新方法

介绍了变压器保护正常动作率的现状,分析了当前比较流行的变压器励磁涌流判断方法,并指出缺陷。提出了一种基于磁通轨迹特征的变压器励磁涌流识别新方法,该方法根据变压器发生内部故障时铁心不饱和,而出现励磁涌流时铁心饱和的原理,利用实测的变压器电压和电流量推算变压器主磁通的轨迹,通过提取主磁通轨迹的特征来判断主磁通变化范围,从而确定变压器是否发生励磁涌流。仿真结果证明了识别方法的可行性。     

基于FPGA的干涉信号双ADC采集系统设计

干涉信号在光谱分析领域有着广泛应用.干涉信号具有动态范围大的特点,为了提高其采样精度,设计了一种以FPGA为核心的双ADC采集和数据处理系统,将输入信号分两路分别进行预处理和AD量化,并通过FPGA进行校正、滤波等信号处理得到一路高精度采集的干涉信号,由CameraLink接口传输至上位机进行显示和分析.通过上位机MATLAB对采集数据进行分析,并与单通道采集结果进行对比,证明采用本文的双ADC采集系统能够提高干涉信号的量化精度,对得到更精确的光谱分析结果具有重要的意义.