Experimental research on an integrated thermooptic switch based on multimode interference couplers

The experimental results of a 2 × 2 integrated thermooptic Mach-Zehnder interferometer (MZI) switch based on multimode interference (MMI) couplers are reported. The insertion loss (IL) is 3.40 dB, the polarization dependent loss is 0.47 dB, the extinction ratio (ER) at bar state and cross state is 32.01 dB and 16.42 dB respectively, the response time is less than 3 ms, and the power consumption is 658 mW. Regarding the asymmetry of extinction ratio at bar state and cross state, theoretical analysis is first presented. The coupling ratio of the two MMI couplers deviates from 50:50 but the deviation is nearly the same, which is decided by good uniformity of semiconductor planar lightwave circuit (PLC) process. This property affects the extinction ratio at bar state and cross state in different mechanisms. Adding a metal electrode on the waveguide affects its effective index and analysis based on experimental results is given. The increment of waveguide effective index is in the order of 2 × 10⁻⁴. Translated from Acta Optica Sinica, 2006, 26(8): 1187–1191 [译自: 光学学报]     

An effective and accurate method for the design of directional couplers

A new method which combines the three-dimensional (3-D) beam propagation method with the overlap integral method is presented for the design of directional couplers. A backward beam propagation is calculated for the output region to reduce the computation time greatly. The design method is illustrated with buried silica-on-silicon waveguide couplers. Results obtained with the 3-D model are compared with those from the two-dimensional model and it is shown that the 3-D model should be used. The design results are verified by both 3-D simulations and experiments. The new design method is shown to be effective and accurate.     

基于递归中值滤波的暂态能量方向元件仿真分析

阐述了基于递归中值滤波的暂态能量方向元件的原理,并给出其快速实用算法.建立一500 kV超高压输电系统模型,对该方向元件的动作特性进行了ATP仿真分析.仿真结果表明,该方向元件能够非常明确地判别出故障的方向,且不受故障位置、类型、初始角、过渡电阻等因素的影响,具有很好的方向识别性能.     

基于递归中值滤波的暂态能量方向元件仿真分析

阐述了基于递归中值滤波的暂态能量方向元件的原理,并给出其快速实用算法。建立一500 kV超高压输电系统模型,对该方向元件的动作特性进行了ATP仿真分析。仿真结果表明,该方向元件能够非常明确地判别出故障的方向,且不受故障位置、类型、初始角、过渡电阻等因素的影响,具有很好的方向识别性能。     

自适应相补偿电压突变量方向元件动作特性的仿真分析

在分析了自适应相补偿电压突变量方向元件动作特性的基础上,针对该元件进行了正、反方向不同故障点,不同故障类型的仿真分析。利用ATP/EMTP建立了振荡典型参数可控的振荡仿真模型,并对自适应相补偿电压突变量方向判别元件在纯振荡中和振荡中再发生故障的情况分别进行了仿真分析,结果表明该方向元件在各种故障情况下均能正确动作,在纯振荡中不会误动。     

自适应相补偿电压突变量方向元件动作特性的仿真分析

在分析了自适应相补偿电压突变量方向元件动作特性的基础上,针对该元件进行了正、反方向不同故障点,不同故障类型的仿真分析.利用ATP/EMTP建立了振荡典型参数可控的振荡仿真模型,并对自适应相补偿电压突变量方向判别元件在纯振荡中和振荡中再发生故障的情况分别进行了仿真分析,结果表明该方向元件在各种故障情况下均能正确动作,在纯振荡中不会误动.     

一种基于方向行波的平行双回线保护方案

在分析故障后电气量特征的基础上,提出了一种基于方向行波的平行双回线保护方案,利用线路两侧方向行波之间的关系判别区内、区外故障和故障线路,该方案可以保护线路全长,不受母线出线数目的影响,在双回线单回运行时,可以正确动作。与传统基于工频量的保护相比,动作速度快,不受CT饱和影响,且不受负荷电流影响。仿真计算验证了该方案的可行性。     

一种基于方向行波的平行双回线保护方案

在分析故障后电气量特征的基础上,提出了一种基于方向行波的平行双回线保护方案,利用线路两侧方向行波之间的关系判别区内、区外故障和故障线路,该方案可以保护线路全长,不受母线出线数目的影响,在双回线单回运行时,可以正确动作.与传统基于工频量的保护相比,动作速度快,不受CT饱和影响,且不受负荷电流影响.仿真计算验证了该方案的可行性.     

A novel digital directional transformer protection technique based on wavelet packet

This paper presents a novel digital technique for transformer protection. The technique is based on deriving a directional quantity proportional to the fault current signal and the prefault voltage signal. Standard fast wavelet transform (FWT) schemes may not be as effective for data that has chiefly oscillatory features. An effective solution to discrimination involves examining the signal in both the time and frequency domains simultaneously. The wavelet packet transform is an extension of the FWT that allows for finer characterization of signal content for both time and frequency together. A 11/132-kV transformer connected to a 132-kV power system was simulated using Alternative Transient Program/Electromagnetic Transient Program (ATP/EMTP). Results indicate that the proposed technique is stable, reliable, and fast during the discrimination between internal and external faults, magnetizing inrush currents, and internal faults, ratio-mismatch, and saturation of current transformers (CTs).     

正序故障分量方向元件误动的原因分析及其对策

文中简单介绍了正序故障分量方向元件的判别原理,给出了该方向元件在保护装置中比较详细的判向流程,深入分析了现场某次故障中该方向元件将正向故障误判为反向的原因,并给出了解决方案.新方案的物理意义明确,实现方法简单,对正反方向元件都有较高的灵敏度,提高了反方向元件的动作可靠性,能可靠防止上述故障事例中的误判向现象.新方案中的判据同样适用于负序、零序功率方向元件,且其已通过一系列有针对性的动模试验的验证,用于保护现场.     

正序故障分量方向元件误动的原因分析及其对策

文中简单介绍了正序故障分量方向元件的判别原理,给出了该方向元件在保护装置中比较详细的判向流程,深入分析了现场某次故障中该方向元件将正向故障误判为反向的原因,并给出了解决方案。新方案的物理意义明确,实现方法简单,对正反方向元件都有较高的灵敏度,提高了反方向元件的动作可靠性,能可靠防止上述故障事例中的误判向现象。新方案中的判据同样适用于负序、零序功率方向元件,且其已通过一系列有针对性的动模试验的验证,用于保护现场。     

一种基于方向元件的微网保护控制方案

随着新能源利用的不断提高,微电网受到了越来越多的关注。在微网孤岛运行结构特点研究基础上,提出了一种基于负序方向元件的微网孤岛运行保护方案。该方案只需比较保护安装处的负序电压与电流的相角差即可判别故障方向,且具有很好的抗过渡电阻能力。基于PSCAD/EMTDC搭建的仿真模型验证了结论的正确性。     

A combined directional and faulted phase selector element based onincremental quantities

In this paper, differential incremental or superimposed voltage and current quantities are used in order to determine directionality of a fault in a network. It is shown that this can be accomplished by performing three scalar products between three voltage and current phasor pairs. The relative levels of these same three scalar products can be furthermore used to identify the faulted phases. While, in ultra-high-speed directional comparison relays, superimposed voltage and current had to be treated in the time domain in order to get speed. In this paper, all computations are done in the frequency domain     

Electricity consumption and human development level: A comparative analysis based on panel data for 50 countries

As a representative of modern energy, the level of electricity consumption can be regarded as an appraisal criterion of a country’s development level. This study analyses the causality between electricity consumption and human development and assesses the changing trend of electricity consumption. The models in this study are established using panel data from 1990–2009 for 50 countries divided into four groups according to income. For human development indicators, per-capita GDP, consumption expenditure, urbanisation rate, life expectancy at birth and the adult literacy rate were selected. The results show that long-run bidirectional causality exists between electricity consumption and five indicators. Additionally, the higher the income of a country, the greater is its electricity consumption and the higher is its level of human development. Further, the variables of four income-groupings vary considerably. Specifically, as income increases, the contribution of electricity consumption to GDP and consumption expenditure increases, but the urbanisation rate, life expectancy at birth and adult literacy rate present a weakening trend. This mainly because that the latter indicators in high-income countries are increasing to converge. To improve human development, electricity should be incorporated into the basic public services construction to enhance the availability of electricity for low-income residents.     

基于同侧电流变化的线路方向保护算法研究

在输电线路发生故障时,故障电流与正常运行负荷电流的相位变化存在一定的规律,利用此规律可以构成一种新的方向元件.通过上述对负荷电流与故障电流相位关系的定性分析,提出了一种基于同侧电流变化的线路方向保护算法,它通过判断故障前后的电流的相位关系构成了一种新型的方向元件,来判断故障区域.这种判别方法作为方向元件只用到了电流信息,可以应用于双端以及多电源的线路故障判断,尤其是电压过小时的故障判断,可以较好解决传统方法在电压过低时误判而导致误动的情况.通过大量的EMTDC/MATLAB仿真验证,表明这种新型的判别算法是正确可行的.     

基于STM32的全方位移动平台设计和控制

为了实现移动平台的全方位移动和避障,设计了一种基于 STM32开发板的移动平台控制系统。该系统利用红外传感器以及无刷电机的差速转动实现循迹,利用超声波传感器进行测距,并通过对收集到的数据信息进行处理与分析实现避障。另设有无线控制模式,当移动平台遇到障碍或处于非循迹轨道上时,操作者可通过摇杆实现对移动平台的方向控制。实验结果表明,移动平台可以自动检测方位并修正,实现无碰撞行驶。     

YOT51型和R17K型液力偶合器故障分析及处理

对17K1-E和YOT51型液力偶合器在实际运行过程中经常出现的勺管卡涩、易熔塞熔化、轴承烧损、工作油压消失以及偶合器振动等故障进行了原因分析,并提出改进措施。     

基于适应型Petri网的多环电陬方向保护简单回路拓扑分析

为了减少复杂环网方向保护整定计算中有向简单回路形成的复杂性。对双回线支路进行处理．使得简单回路计算规模得到预先缩小。考察网络实时拓扑分析的动态特性。运用适应型Petfi网推理系统拓扑结构．将复杂系统的网络分解为若干基本分析单元。描述了一个由保护开关状态变化引起网络关联节点变迁的离散事件动态过程。通过对电网节点支路关联信息进行推理．得到约简有向简单回路矩阵。通过实际算例仿真．建立模型，分析该方法的拓扑机理。计算结果与传统算法一致．验证所提方法的有效性，得出该方法计算准确、过程简便且易于实现的结论。     

基于适应型Petri网的多环电网方向保护简单回路拓扑分析

为了减少复杂环网方向保护整定计算中有向简单回路形成的复杂性,对双回线支路进行处理,使得简单回路计算规模得到预先缩小。考察网络实时拓扑分析的动态特性,运用适应型Petri网推理系统拓扑结构,将复杂系统的网络分解为若干基本分析单元,描述了一个由保护开关状态变化引起网络关联节点变迁的离散事件动态过程。通过对电网节点支路关联信息进行推理,得到约简有向简单回路矩阵。通过实际算例仿真,建立模型,分析该方法的拓扑机理,计算结果与传统算法一致,验证所提方法的有效性,得出该方法计算准确、过程简便且易于实现的结论。