GENERATOR VIBRATION FAULT DIAGNOSIS METHOD BASED ON ROTOR VIBRATION AND STATOR WINDING PARALLEL BRANCHES CIRCULATING CURRENT CHARACTERISTICS

Rotor vibration characteristics are first analyzed, which are that the rotor vibration of fundamental frequency will increase due to rotor winding inter-turn short circuit fault, air-gap dynamic eccentricity fault, or imbalance fault, and the vibration of the second frequency will increase when the air-gap static eccentricity fault occurs. Next, the characteristics of the stator winding parallel branches circulating current are analyzed, which are that the second harmonics circulating current will increase when the rotor winding inter-turn short circuit fault occurs, and the fundamental circulating current will increase when the air-gap eccentricity fault occurs, neither being strongly affected by the imbalance fault. Considering the differences of the rotor vibration and circulating current characteristics caused by different rotor faults, a method of generator vibration fault diagnosis, based on rotor vibration and circulating current characteristics, is developed. Finally, the rotor vibration and circulating current of a type SDF-9 generator is measured in the laboratory to verify the theoretical analysis presented above.

Lower Bounds and a Nearly Fastest General Parallel Branch-and-Bound Algorithm

In this paper, it is supposed that the B&B algorithm finds the first optimal solution after h nodes have been expanded and m active nodes have been created in the state-space tree. Then the lower bound Ω(m+h log h) of the running time for the general sequential B&B algorithm and the lower bound Ω(m/p+h log p) for the general parallel best-first B&B algorithm in PRAM-CREW are proposed, where p is the number of processors available. Moreover, the lower bound Ω(M/p+H+(H/p) log (H/p)) is presented for the parallel algorithms on distributed memory system, where M and H represent total number of the active nodes and that of the expanded nodes processed by p processors, respectively. In addition, a nearly fastest general parallel best-first B&B algorithm is put forward. The parallel algorithm is the fastest one as p = max{hε, r}, where ε = 1/ rootlogh, and r is the largest branch number of the nodes in the state-space tree.

Modular Reciprocating HVDC Circuit Breaker with Current-limiting and Bi-directional Series-parallel Branch Switching Capability

The high-voltage direct current(HVDC)circuit breaker is becoming popular with the rapid development of the flexible HVDC grid for efficient DC fault ride-through purposes.This paper proposes a novel module for reciprocating HVDC circuit breaker topology,whose branch connections are able to switch between series and parallel modes to limit the rising rate and interrupt the DC fault currents.Diode-bridge submodules(DBSMs)are used to compose the main branch for current interruption.Besides fault clearance,the proposed topology has the advantageous function of DC fault current limiting by employing DBSMs with bi-directional conduction capability.The topology can easily switch among branch connection modes through the assembled trans-valves,and their resistance and reactance are very small in the normal state when branches are in parallel and the values become promptly large in the transient state when the branches are series connected.With the modular design,it is easy to change the number of branches or sub-modules and the types of sub-modules to adapt to more specific needs.A 6-terminal modular multi-level converter(MMC)based HVDC grid is established in PSCAD/EMTDC,and various simulation scenarios are carried out to validate the proposed topology.

Synthesis of Branched Chains with Actuation Redundancy for Eliminating Interior Singularities of 3T1R Parallel Mechanisms

Although it is common to eliminate the singularity of parallel mechanism by adding the branched chain with actuation redundancy, there is no theory and method for the configuration synthesis of the branched chain with actuation redundancy in parallel mechanism. Branched chains with actuation redundancy are synthesized for eliminating interior singularity of 3-translational and 1-rotational（3T1R） parallel mechanisms. Guided by the discriminance method of hybrid screw group according to Grassmann line geometry, all the possibilities are listed for the occurrence of interior singularities in 3T1R parallel mechanism. Based on the linear relevance of screw system and the principles of eliminating parallel mechanism singularity with actuation redundancy, different types of branched chains with actuation redundancy are synthesized systematically to indicate the layout and the number of the branched chainsinterior with actuation redundancy. A general method is proposed for the configuration synthesis of the branched chains with actuation redundancy of the redundant parallel mechanism, and it builds a solid foundation for the subsequent performance optimization of the redundant actuation parallel mechanism.

Parallelization of a Branch and Bound Algorithm on Multicore Systems

The general m-machine permutation flowshop problem with the total flow-time objective is known to be NP-hard for m ≥ 2. The only practical method for finding optimal solutions has been branch-and-bound algorithms. In this paper, we present an improved sequential algorithm which is based on a strict alternation of Generation and Exploration execution modes as well as Depth-First/Best-First hybrid strategies. The experimental results show that the proposed scheme exhibits improved performance compared with the algorithm in [1]. More importantly, our method can be easily extended and implemented with lightweight threads to speed up the execution times. Good speedups can be obtained on shared-memory multicore systems.

Optimization for Hydroforming Loading Paths of Parallel Multi-branch Tubes Based on Grey System Theory

According to characteristic of hydroforming of parallel multi-branch tubes,multi-objective problems were transformed to single objective problem of relational grade comparison by grey system theory.Two different objectives were selected,according to the principle that process parameters were optimal which of grey relational grade were maximum,the optimal loading parameters under different objective condition were obtained,and loading paths were optimized.The results indicated that parallel multi-branch tubes hydroformed under loading paths optimized by grey system theory could meet with the requirement that objective was optimal.And the optimal loading paths under different objectives were different,and the appropriate objective should be selected according to forming characteristic.

车用锂离子并联电池组连接故障特性

首先设计并联电池组连接故障试验,对并联电池组连接故障特性进行了初步分析,发现连接故障电阻越大,故障电压曲线偏离正常电压曲线程度越大;然后搭建并联电池组故障仿真模型,探究不同位置连接故障下并联电池组电压及支路电流特性,结果表明,发生连接故障的位置越靠近负载连接点,各支路电流分配不均匀程度受影响越小;最后,探究不同程度连接故障下电压、电流及容量增量(incremental capacity,IC)曲线特性,发现不同连接故障程度下支路电流曲线存在明显的差异性,不同倍率下IC曲线特征差异性较大,Ⅱ峰相对较为稳定,其与接触阻抗存在一定的相关性.

基于多模态数据融合的飞行员注视区域分类

为了解决图像采集过程中眼图消失和头部姿态估计不准确的问题,利用基于非接触式的眼部信息获取方法采集人脸图像,从单个图像帧中确定飞行员当前的注视方向.同时,针对现有网络忽略头部运动对视线造成遮挡所导致的分类效果不佳问题,结合人脸图像与头部姿态特征,通过改进的MobileViT模型提出一种用于飞行员注视区域分类的多模态数据融合网络.首先提出了多模态数据融合模块解决特征拼接过程中尺寸不平衡导致的过拟合问题,其次提出一种基于并行分支SE机制的逆残差块,充分利用网络浅层的空间和通道特征信息,并结合Transformer的全局注意力机制捕捉多尺度特征.最后,重新设计了Mobile Block结构,使用深度可分离卷积降低模型复杂度.利用自制数据集FlyGaze对新模型和主流基线模型进行对比,实验结果表明, PilotT模型对注视区域0、3、4、5的分类准确率均在92%以上,且对人脸发生偏转的情况具有较强适应力.研究结果对提升飞行训练质量以及飞行员意图识别和疲劳评估具有实际应用价值.

自由度可调模块单元系统运动学并行建模

针对多个自由度可调模块单元组成的系统,提出含标准化流程的模块化机器人拓扑结构数学描述及运动学并行建模方法。首先,建立模块单元运动传递库,并提出含标准化流程的四元组矩阵模块化机器人拓扑结构数学描述。接着,以模块单元运动学模型为基础,考虑多分支模块化机器人各分支间耦合影响,建立适用于链式模块化机器人的位置级与速度级运动学模型。随后,提出模块化机器人运动学并行建模方法,理论分析和仿真结果均表明该算法能够适应各类型拓扑结构模块化机器人的快速建模。拓扑结构数学描述与并行计算的引入降低了模块化机器人建模难度,提升了建模效率。

基于逆阻型IGCT器件的固态式直流断路器设计及研制

直流系统是支撑高比例新能源接入与灵活高效用能的重要技术方向。固态式直流断路器(solid state DC circuit breaker,SSCB)具有开断速度极快、无电弧、寿命长等优点,在中低压直流系统的故障保护中得到广泛应用。随着电力电子器件的发展,固态式直流断路器的拓扑结构、工作性能也在不断进步。为此基于逆阻型集成门极换流晶闸管(intergated gate commutate thyristor,IGCT),提出了一种新型的固态式直流断路器结构及设计方法,通流支路采用逆阻IGCT反并联结构实现双向通流,缓冲支路采用金属氧化物避雷器(metal oxide varistor,MOV)-电容结构来抑制过电压,吸能支路采用MOV吸收系统能量。进一步地,给出了关键元器件的参数设计方法,并验证了有效性;设计了性能良好的重力热管散热器,单个模块散热功率可达700 W;提出了主被动结合的控保策略,提高断路器的保护性能。最后,研制了固态式直流断路器样机,可用于750 V以内的低压直流系统,额定通流可达2 kA,可在百微秒内开断10 kA故障电流,成本低、体积小、高可靠,具有良好的应用前景。

一种复合驱动并联机构刚度分析

针对直升机旋翼支撑平台,设计了一种复合驱动四自由度并联机构,利用复合驱动分支增大了并联机构工作空间。推导了并联机构中各驱动分支和动平台之间的运动关系式,考虑约束力、驱动力和驱动力矩综合作用下复合驱动分支的横向变形、轴向变形和扭转变形,结合机构的运动学方程推导了复合驱动并联机构的刚度矩阵。利用有限元软件验证了并联机构整体刚度矩阵的正确性。仿真结果表明该并联机构的刚度满足使用需要,为含复合驱动并联机构的应用和推广奠定了理论基础。

一类加工需要额外资源的平行机调度问题的算法设计

给出了一类加工需要额外资源的平行机调度问题的精确算法。针对在平行机上加工的工件,除需要机器资源外,还需要一个单位额外资源的问题,考虑额外资源的种类和数量有限,以给出问题的最优调度使工件的完工时间最小为目标。该问题源于地球观测卫星的数据下载,在智能制造和信息处理等领域亦有广泛应用。给出了该问题的整数规划模型、最优解下界和分支定界算法;给出了一种有效的分支策略以避免重复分支,设计了相应的定界方法以提高算法的收敛速度。通过小规模实例和大量的数值仿真实验,验证了算法的正确性和在不同参数配置下的有效性。

并行双分支融合网络用于视网膜血管分割

针对视网膜图像中拓扑结构复杂、对比度差的毛细血管,已有的深度学习模型存在分割精度低、分割结果不连续问题,提出一种基于深度学习的并行双分支融合网络,该网络包含并行双分支模块和融合模块两部分.并行双分支模块使用两条U形支路:像素级分割支路和中心线级分割支路,旨在分别获取视网膜图像中粗血管和细血管.基于空间注意力的融合模块旨在进一步优化并行双分支模块输出的初步分割图,获取毛细血管的更多细节特征.在ROSE-1的SVC数据集上的实验结果表明:所提出的模型在所有评价指标中表现优异,其中,ROC曲线下的面积占比(AUC)达到了93.63%,精确度(ACC)达到了92.25%.

一种含中心驱动五自由度并联机构运动学分析

设计了一种含中心驱动五自由度并联机构,分析了该机构的自由度和结构特点。利用矢量法建立了含中心驱动五自由度并联机构中各驱动分支和动平台运动之间的映射关系,利用中心驱动分支中的约束力/约束矩,推导了该并联机构的Jacobean矩阵和Hessian矩阵。建立了含中心驱动五自由度并联机构的运动学模型。利用先进CAD软件验证了并联机构运动学模型的正确性。分析了含中心驱动五自由度并联机构定姿态工作空间,为该类并联机构的应用奠定了理论基础。

定子匝间短路对发电机并联支路环流特性的影响

分析了汽轮发电机定子匝间短路故障下的并联支路环流特性,以及故障参数发展对环流特性的影响。对故障时的气隙磁密进行了推导,得到两条并联支路电势差表达式,分3种情况对并联支路的环流特性进行了分析。分析了短路程度加剧、两条支路有效匝数差增大、励磁电流增大等故障参数发展对环流特性的影响。实测了SDF-9型故障模拟发电机在3种不同匝间短路情况下的环流信号,实验结果与理论分析基本吻合。研究表明,当单条支路短路或两条支路不对称短路时,并联支路内部将产生基波与三次谐波环流,且环流数值将随短路不对称程度加剧或励磁电流增大而增大;当两条支路对称短路时,并联支路内部不产生环流,且不论短路如何发展、励磁电流如何增大,环流数值不变。

发电机气隙偏心时定子并联支路的环流特性分析

为了有效监测和诊断发电机主要的机械故障之一的气隙偏心故障,在分析发电机正常情况及气隙偏心故障时定子绕组并联支路环流特性的基础上,提出了一种基于环流特性的气隙偏心故障诊断方法。通过分析汽轮发电机在正常运行和气隙偏心故障时的气隙磁势、磁导、磁密,推导得到了发电机定子绕组各并联支路感应电势瞬时值和电势差的瞬时值表达式,然后结合静偏心、动偏心、动静复合偏心3种偏心故障下的气隙情况,具体分析了偏心故障下的定子并联支路环流的谐波成分特性及其与对应故障参数的变化关系,从而得到了定子绕组并联支路环流特性即故障使环流基频成分突出,环流值随偏心程度的加重而增大。实测SDF-9型故障模拟发电机气隙偏心故障时环流信号与理论分析结果基本符合。

基于并联支路环流特征的转子匝间短路故障识别

汽轮发电机转子绕组匝间短路是一种常见的发电机故障,为了对其进行状态监测和故障识别,提出了基于定子绕组并联支路环流特性的汽轮发电机转子绕组匝间短路故障识别方法。通过分析汽轮发电机正常运行及转子匝间短路故障运行时各参数的变化,得到了定子绕组并联支路电压差和环流特性,即理想电机在正常运行时不存在电压差和环流,而转子匝间短路故障导致发电机定子绕组并联支路之间出现了电压差和环流,其大小和分布与短路严重程度呈对应关系。最后,实测了MJF-30-6型故障模拟发电机正常运行及故障运行时的环流信号,与理论分析结果基本符合。

多功能电池管理系统及其使用平台

针对并联电池组性能的研究,开发了一套多功能电池管理系统。该电池管理系统的特点在于能够测量并联电池组里单体电池支路电流和计算单体SOC,同时还具备一般电池管理系统的电压采集、温度采集、通讯以及保护等功能。介绍的电池管理系统将突出其对并联电池组支路电流的测量,从硬件和软件方面介绍该电池管理系统,并介绍了电压通道校准的原理和方法。该电池管理系统已应用于并联电池组特性研究中和电池寿命测试平台里,给出了电池管理系统测得的并联电池的特性,介绍了电池寿命测试平台,并从中验证电池测试系统的功能和可靠性。

荔枝树枝力学特性的试验研究

为获取荔枝树枝的力学特性参数,以糯米糍品种荔枝树枝为试验材料,在精密型微控电子式万能试验机上进行了压缩特性和剪切特性试验。测得荔枝树枝顺纹抗压强度平均值为32.77MPa,顺纹抗压弹性模量平均值为1068.02MPa,顺纹压缩能平均值为56.57N.m;树枝横纹抗压比例极限应力平均值为8.02MPa,横纹抗压弹性模量平均值为422.84MPa,横纹压缩能平均值为1.25N.m;树枝剪切强度平均值为9.52MPa,剪切功平均值为17.59N.m。采用统计软件对树枝力学特性参数进行相关性分析,结果表明:顺纹抗压强度和顺纹压缩能之间呈指数函数正相关关系;横纹抗压比例极限应力和横纹压缩能之间呈弱对数函数正相关关系;峰值剪切力、剪切功都与树枝横截面面积呈强线性正相关。试验结果为研制果树修剪机具提供了依据。

多并联支路型可控电抗器短路电抗对支路电抗和电流的影响

短路电抗对支路电抗和电流的影响是造成多并联支路型可控电抗器(Controllable Reactor of Multi-parallel Branch Type,CRMB)支路电抗和电流额定值的选取困难、以及设备利用率下降的重要原因。根据CRMB各支路晶闸管依次导通和关断的工作特点,采用递推算法求得了CRMB支路电抗和电流的计算公式。对这些计算公式的函数分析和算例分析后指出,支路电抗随着短路电抗的增大而减小;支路电流额定值随着短路阻抗的增大而增大,而其支路电流额定值利用率最小值随着短路电抗的增大而减小;为了提高CRMB设备利用率,CRMB短路电抗应小于一个由电流额定值利用率的最小值、CRMB支路容量递增系数和支路数决定的最大值,由此可以选取短路电抗、支路电抗和电流的设计额定值。研究结论可为CRMB的工程设计和变压器式可控电抗器的研究提供理论参考。