A study of fault detection way for computer networks based on multiple stages

To relieve traliic overhead induced by active probing based methods, a new fault detection method, whose key is to divide the detection process into multiple stages, is proposed in this paper. During each stage, only a small region of the network is detected by using a small set of probes. Meanwhile, it also ensures that the entire network can be covered alter multiple detection stages. This method can guarantee that the traffic used by probes during each detection stage is small sufficiently so that the network can operate without severe disturbance from probes. Several simulation results verify the effectiveness of the proposed method.

The Detection of Inter-Turn Short Circuits in the Stator Windings of Sensorless Operating Induction Motors

This work proposes an alternative strategy to the use of a speed sensor in the implementation of active and reactive power based model reference adaptive system (PQ-MRAS) estimator in order to calculate the rotor and stator resistances of an induction motor (IM) and the use of these parameters for the detection of inter-turn short circuits (ITSC) faults in the stator of this motor. The rotor and stator resistance estimation part of the IM is performed by the PQ-MRAS method in which the rotor angular velocity is reconstructed from the interconnected high gain observer (IHGO). The ITSC fault detection part is done by the derivation of stator resistance estimated by the PQ-MRAS estimator. In addition to the speed sensorless detection of ITSC faults of the IM, an approach to determine the number of shorted turns based on the difference between the phase current of the healthy and faulty machine is proposed. Simulation results obtained from the MATLAB/Simulink platform have shown that the PQ-MRAS estimator using an interconnected high-gain observer gives very similar results to those using the speed sensor. The estimation errors in the cases of speed variation and load torque are almost identical. Variations in stator and rotor resistances influence the performance of the observer and lead to poor estimation of the rotor resistance. The results of ITSC fault detection using IHGO are very similar to the results in the literature using the same diagnostic approach with a speed sensor.

基于发电机定子接地燃弧电阻变化特征的主动降压熄弧机理与抑制方法

定子接地燃弧故障是制约大型发电机安全可靠运行的技术瓶颈。为解决定子绕组接地电弧引发的绝缘击穿与铁心损伤问题,该文提出基于发电机定子接地燃弧电阻变化特征的柔性接地主动降压熄弧方法。该文建立了定子接地燃弧电阻与弧道电压的解析关系,揭示了定子接地故障点电压降低过程中,接地燃弧电阻增大的变化规律;明确了将接地故障点电压抑制在电弧重燃电压以下时,可实现定子绕组击穿间隙回归正常绝缘状态的抑制方法。根据大型发电机定子柔性接地方式降压熄弧策略,在接地故障燃弧阶段,中性点电压源输出故障点工频与3次谐波反向电势,主动降低故障点电压,将故障点电压降低至燃弧电压以下,使定子接地电弧熄灭。利用注入信号感知定子接地燃弧状态,实时监测定子阻尼率矢量角变化趋势,判定降压消弧过程中接地燃弧故障是否消除。所提方法无需将故障点电压降低至零,可有效降低非故障相电压抬升,降低定子非故障相绕组槽内击穿风险。在PSCAD/EMTDC仿真环境模拟定子接地故障燃弧工况,对所提方法进行试验验证。试验结果表明,基于定子接地燃弧电阻变化特征的柔性接地消弧方法可主动降低定子接地故障点电压,助增故障点间隙绝缘电阻回归,抑制接地电弧重燃,降低定子非故障相绝缘击穿风险,实现定子接地燃弧故障的可靠消弧。

活动构造与强震:专辑序言

活动构造既是地壳最新活动的表现,也是导致强震的主要根源。中国内地因发育了复杂的活动构造系统,成为世界上强震活动及相关灾害特别严重的地区。因此,深入认识中国内地的活动构造特征与强震发生规律,有助于在城镇规划和重大工程建设中科学防范或规避强震灾害风险。为了及时交流活动构造与强震研究领域的最新成果,此期专辑优选了代表性论文12篇,主要涵盖了活动构造控震、古地震、活动断裂调查与探测、地震地质灾害、遥感技术应用和水库诱发地震共6个不同领域的研究进展。综合此期专辑的新成果和国内外相关领域的研究动态,建议活动构造与强震研究应关注4个方面的动态进展,包括:从活动构造演化及活动断裂体系角度更全面地认识区域强震的危险性;活动构造已步入定量化与精细化调查研究阶段;高精度遥感和多种定年技术的应用正在不断扩展古地震研究的范围和时限;人类活动诱发地震问题。

融合灭弧信息的有源串联接地配电网故障检测方法

为了优化有源全补偿消弧设备和挖掘灭弧状态信息包含的故障特征,该文提出基于串联分压的配电网消弧原理及融合灭弧状态信息的接地故障检测方法。提出采用单个H桥变流器与消弧线圈串联的有源降压消弧全补偿方法和灵活接入保护电容的有源消弧装置保护方案,在消弧原理与控制、设备承压与安全、功率输出与过压防护等方面表现出良好性能。提出融合有源降压消弧全补偿“伪正常”状态信息的接地故障检测方法,利用系统正常-故障-灭弧3种状态信息构造故障检测判据,在免受过渡电阻和分布参数不对称影响的基础上优化故障检测方式和提高故障检测效率,无需线路间信息的横向比较即可实现系统全域零序导纳测量、故障馈线独立判别和故障程度跟踪识别。仿真实验证实了方法的有效性,为优化配电网有源消弧和接地故障检测提供创新方案。

基于电阻变化率和有功功率的混合孤岛检测方法

为解决传统检测方法阈值设置困难、对电能质量影响大的问题,提出一种基于电阻变化率和有功功率扰动相结合的混合孤岛检测方法。电阻变化率作为被动方法,该特征量在孤岛后可快速响应,有功功率扰动模块仅在被动方法怀疑孤岛时开启,自适应注入能使公共耦合点电压越限的最小有功功率。仿真结果表明,该方法可快速正确地检测出孤岛,即便在非孤岛情况下也不会发生误判。

基于主动探测原理的直流配电线路短路故障测距

为克服对端系统助增作用的影响,实现直流配电线路短路故障的准确测距,提出一种主动探测式的故障测距原理。故障发生后,设计限流策略限制短路电流,进而切换至主动探测控制策略下,向直流线路注入特征频率探测信号。根据特征频率下故障等效电路的激励与响应特性,构建故障测距方程,实现了基于故障分析法的单端量故障测距。基于PSCAD电磁暂态仿真软件搭建了对应模型,仿真验证了不同故障位置和故障过渡电阻情况下测距原理的性能,采用特征频率探测信号构建测距方程,克服了对端电源助增作用的影响,测距结果的相对误差在0.5%以内。

综合物探和钻探技术在第四纪隐伏断层探测中的应用

采用以高分辨率地震勘探为主,配合瞬变电磁和高密度电阻率探测的方法,快速、准确圈定了北坞断裂的上断点位置、埋深等信息;通过跨断层联合剖面钻探和地球物理测井工作,查明了晚第四纪地层特征和层序,精确定位了目标断层的空间位置和断层位移量,进而揭示了目标断层的活动性。结果表明:综合物探技术的解释结果和钻探结果基本吻合,证明了方法的有效性。

基于静止同步补偿器的主动支撑型控制及其限流方法

随着新能源发电渗透率不断提高,并网系统的电压稳定性和惯量降低,需配置一定储能的静止同步补偿器(Static synchronous compensator,STATCOM)参与电网进行电压和惯量主动支撑。首先,基于储能型STATCOM的拓扑结构和数学模型,利用同步控制建立虚拟内电势的三相电压,以实现自主惯量响应和电压主动支撑,提升新能源场站的友好并网能力;接着针对该控制容易过流的问题,提出了一种自适应的限流方法,并在电压外环增加虚拟阻抗环节,最后提出电流检测方法;在MATLAB/Simulink仿真平台上搭建了仿真模型验证了主动支撑策略及限流方法的有效性。

基于换相阈值精准计算的三电平逆变器故障行为挖掘

三电平结构在高压功率下可实现交流电机的变频调速,但是由于死区时间的引入,导致系统控制性能变差,输出的电压与电流发生畸变,甚至会导致电动机发生机械谐振。为有效控制电压波形的分布,提出基于换相阈值精准计算的三电平逆变器故障行为挖掘方法。计算非导与导通绕组电感的具体数值,完成逆变器故障行为建模。按照三电平逆变器结构定义故障行为表现区间,得到准确的换相阈值计算结果,实现对三电平逆变器的故障检测。实验结果表明,电压传输波的极大值不超过257.5 V、极小值不低于134.8 V,符合有效控制电压波形分布形式的要求。

Closed-loop fault detection for full-envelope flight vehicle with measurement delays

Abstract A closed-loop fault detection problem is investigated for the full-envelope flight vehicle with measurement delays, where the flight dynamics are modeled as a switched system with delayed feedback signals. The mode-dependent observer-based fault detection filters and state estimation feedback controllers are derived by considering the delays＇ impact on the control system and fault detection system simultaneously. Then, considering updating lags of the controllers/filters＇ switching signals which are introduced by the delayed measurement of altitude and Mach number, an asynchronous H analysis method is proposed and the system model is further augmented to be an asynchronously switched time-delay system. Also, the global stability and desired performance of the augmented system are guaranteed by combining the switched delay-dependent Lyapunov Krasovskii functional method with the average dwell time method （ADT）, and the delaydependent existing conditions for the controllers and fault detection filters are obtained in the form of the linear matrix inequalities （LMIs）, Finally, numerical example based on the hypersonic vehicles and highly maneuverable technology （HiMAT） vehicle is given to demonstrate the merits of the proposed method.

Pilot protection of hybrid MMC DC grid based on active detection

Considering the advantages and limitations of traditional identification method,combined with the strategy of active detection,the principle of DC grid pilot protection based on active detection is proposed to improve the sensitivity and reliability of hybrid MMC DC grid protection,and to ensure the accurate identification of fault areas in DC grid.By using the DC fault ride-through control strategy of the hybrid sub-module MMC,the fault current at the converter station DC terminal is limited.Based on the high controllability of hybrid MMC,sinusoidal fault detection signals with the same frequency are injected into the line at each converter station.Based on model recognition,the capacitance model condition is satisfied by the detected signals at both ends during external faults whereas not satisfied during internal faults.The Spearman correlation coefficients is then introduced,and the correlation discriminant of capacitance model is constructed to realize fault area discrimination of DC grid.The simulation results show that the active detection protection scheme proposed in this paper can accurately identify the fault area of DC grid,and is not affected by fault impedance and has low sampling rate requirement.

Novel Fault Diagnosis Scheme for HVDC System via ESO

A novel fault detection and identification(FDI)scheme for HVDC(High Voltage Direct Current Transmission)system was presented.It was based on the unique active disturbance rejection concept,where the HVDC system faults were estimated using an extended states observer(ESO).Firstly,the mathematical model of HVDC system was constructed,where the system states and disturbance were treated as an extended state.An augment HVDC system was established by using the extended state in rectify side and converter side,respectively.Then,a fault diagnosis filter was established to diagnose the HVDC system faults via the ESO theory.The evolution of the extended state in the augment HVDC system can reflect the actual system faults and disturbances,which can be used for the fault diagnosis purpose.A novel feature of this approach is that it can simultaneously detect and identify the shape and magnitude of the HVDC faults and disturbance.Finally,different kinds of HVDC faults were simulated to illustrate the feasibility and effectiveness of the proposed ESO based FDI approach.Compared with the neural network based or support vector machine based FDI approach,the ESO based FDI scheme can reduce the fault detection time dramatically and track the actual system fault accurately.What's more important,it needs not do complex online calculations and the training of neural network so that it can be applied into practice.

主动探测式保护关键技术概述及展望

以新能源为主体的新型电力系统中广泛应用的电力电子设备引入了新的故障特征,对继电保护性能提出了更高的要求,传统继电保护技术难以适用。主动探测式保护利用可控的电力电子设备生成特定的探测信号,引入了更为清晰明确的故障特征,可以构造更为简便、灵敏、可靠的保护新原理。基于扰动的故障分析方法为主动探测式保护提供了理论基础,电力电子技术的发展为主动探测式保护提供了应用基础。针对主动探测式保护的具体实现方案,详细分析了探测信号的选择、生成、注入时机和处理等关键技术,归纳整理了主动探测式保护在直流系统和新能源发电等典型场景下的应用。对未来的研究方向和工程实践中可能遇到的问题进行了总结评述,期望能为主动探测式保护的深入研究提供参考。

机载LiDAR技术快速识别断裂出露部位新方法

为探讨机载LiDAR技术在快速识别活动断裂中的作用,以关中渭河盆地与秦岭接壤的铁炉子断裂为研究对象,精确提取地形点云数据,给出2 m分辨率的DEM,探究扫描区域的几何展布特征。结果表明,高分辨率DEM数据与断裂特征槽谷、三角面的解译有助于提高机载LiDAR技术在复杂地形活动断裂快速识别中的准确度,为快速探测活动断层提供技术支撑。

eSeis节点单元与手簿通讯故障的维修方法

eSeis节点仪器已规模化应用于三维采集项目中,在维修中发现eSeis节点单元经常出现手簿不能激活节点或节点单元能被激活但检测不到参数的问题。该类故障主要涉及到eSeis节点单元通讯、存储功能等方面的器件,以及MCU固件烧写和电台模块升级等问题。本文针对这些问题,分析、讨论了eSeis节点的组成和基本工作原理,并全面阐述了此类故障的维修过程。同时针对eSeis节点单元通讯故障、存储故障提出了一些维修方法。

地球物理方法探测活动断层效果和方法最佳组合分析

采用综合地球物理方法对长春市的已知断层进行探测实践,表明不同的地球物理方法解决不同问题,并具有不同的效果。例如重磁方法、联合剖面方法可以缩小活动断层的研究范围;探地雷达、浅层地震、高密度电法等方法在研究活动断层的剖面形态中具有很好的作用,而且探地雷达、高分辨率地震能够提供断层的时间等信息,为活动性探测提供依据。针对研究实例分析了综合地球物理方法在活动断层中的组合方法,为开展活动断层的研究提供借鉴。

宿迁城市活动断层探测多方法技术运用的典型案例

城市活动断层是城市潜在危害之一,而对城市隐伏活动断层的准确定位及其最新活动时代的判定,一直是活动断层探测的难题。文中以宿迁市合欢路隐伏活动断层探测为例,通过地质地貌调查和浅层地震勘探初步确定断层位置。依据对折定位法原理,实施钻孔联合剖面探测,把断层上断点限定在平面5m、深度4.4~6.1m的范围内。再通过开挖探槽,精确查明断层近地表位置以及断层最新一次活动时间。利用多层次,多手段综合探测方法,在合欢路场地对安丘-莒县断裂宿迁段的断层精定位和活动性研究中取得了很好的效果。合欢路场地探测结果显示,断层最新一次事件发生在（5.9±0.3）ka BP以后,属于全新世活动断层。

基于克拉克电流相角差值的低压有源配电网故障定位方法

分布式电源大量接入低压配电网,使其变为一个复杂多变的有源网络,导致基于单点测量信息的配电网故障定位方法因不具备自适应性而不再适用。通过研究低压有源配电网区段故障前后其克拉克电流相角差值的变化,得出区内/外故障的判据,并由此提出一种适用于低压有源配电网的故障定位方法。该方法仅需电流测量,通过本地数据采集与处理装置对各区段两端节点处的克拉克电流相角进行等效高频采样,利用控制中心集中计算各区段的克拉克电流相角差值完成快速的故障定位。通过Matlab/Simulink仿真验证了所提方法,该方法可在微电网并网或孤岛运行状态下实现故障区段的准确定位。

基于单相级联H桥变流器的配电网故障消弧与选线新方法

为解决配电网单相接地故障消弧与选线保护难题,提出了一种配电网有源接地方式及其故障消弧与选线新方法。采用单相级联H桥多电平变流器直接接入配电网的中性点,配电网发生单相接地故障时,通过多电平变流器向中性点注入补偿电流,补偿流经接地点的故障全电流,并强制使故障相电压为0,实现故障消弧。经过一定延时后,逐渐减少注入电流至0,多电平变流器退出补偿,进行接地故障判断;若判断系统发生了永久性接地故障,则根据多电平变流器退出补偿前后的注入电流量及各出线零序电流改变量,进行选线保护。理论分析和仿真结果表明:该方法原理清晰、易于实现,具有可行性。