基于EXB841的IGBT驱动电路设计

电力电子器件中,IGBT的综合性能方面占有明显优势,并广泛地运用在各类电力变换装置中。然而如何有效地驱动并保护IGBT,成为电力电子领域中的重要研究课题之一。设计了基于EXB841的驱动电路,结合实际运行过程中出现的故障,不断调整电路,最终完善了IGBT的驱动与保护性能,具有很好的实用性。     

电网短路故障下双馈风电机组传动链扭振响应

电网故障引起的电磁转矩波动易造成风电机组轴系扭振疲劳损耗,严重时会造成轴系故障,有必要研究不同类型电网故障下风电机组传动链扭振响应及其对关键部件的影响。首先,采用集中质量法,考虑叶片柔性建立了风电机组传动链四质量块模型,基于小信号模型,采用模态分析法对风电机组传动链扭振特性进行分析。其次,为了表征不同故障类型对风电机组传动链轴系扭振的影响,在双馈发电机电磁暂态模型的基础上,推导了电网对称与不对称故障下电磁转矩表达式。最后,基于四质量块传动链模型,仿真分析了单相、两相和三相接地电网故障对机组传动链扭振响应的影响。结果表明,不同类型电网故障会影响不同传动链扭振频率及其不同关键部件;三相接地电网故障引起的传动链扭振幅值大,齿轮箱和发电机转子间轴上传递转矩可以较全面反映扭振响应频率;与传动链其他部件相比,发电机转子受到电网故障影响更大。     

用模糊集合理论识别电力系统振荡中的短路的研究

本文通过对电力系统振荡和短路所呈出的不同特征的分析,从故障特征入手,利用模糊集合理论来识别振荡过程中发生的短路,对于振荡中的三相短路的识别,本文提出一种基于振荡中心电压的波形跟踪识别方法,对于振荡中的不对称故障的识别,本文选取模变换中的Ｃｌａｒｋ变换作为数学工具,与对称分子量变换相结合,构造了Ｉα／Ｉβ判据,Ｉａ－Ｉβ与序分量组合判据,文章给出了相应的模糊数学模型,并经大量的仿真试验,获得良好的仿     

牵引馈线自适应重合闸技术研究

就牵引馈线的自适应重合闸问题展开研究,提出了应用小波变换与人工神经网络相结合的方法来识别瞬时性故障与永久性故障,并应用Matlab软件进行了大量的仿真计算,仿真结果表明,应用小波变换与人工神经网络相结合的方法,故障识别的准确性较高,且没有误判现象。     

基于MODWT的变压器绕组轻微故障检测及分类研究

本文基于变压器在不同运行工况下的等效瞬时励磁电感的差异,利用最大重叠离散小波变换 (MODWT) 提取有效故障特征参数,实现对变压器绕组轻微匝间故障以及匝间电弧放电故障的检测。首先提取变压器在各种工况下的电气量,求取等效瞬时励磁电感,选取基于db4小波函数的最大重叠离散小波变换进行分析,提取特征量。将故障特征量作为决策树的训练集和测试集,从而实现变压器绕组轻微故障的识别以及分类。最后通过仿真证明,所提出的算法能够准确检测以及区分励磁涌流、轻微匝间短路故障以及匝间电弧放电故障。     

耦合双回线路电弧故障测距的新相模变换方法

输电线路故障测距一直是经久不衰的研究课题。,根据三相系统和同塔双回线系统的阻抗矩阵关系,从能用单一模量反映所有普通三相系统故障的新相模变换矩阵出发,推导出适用于双回线的相模变换矩阵。提出了一种基于新模量变换的双回线故障定位时域算法,该算法利用某一故障模量电弧电压、电流的转移特性来构造测距算法。它具有如下特点:算法在时域中进行,所需的时间窗短,不需要滤波等环节;用最小二乘法来提高测距精度,且测距的精度不受过渡电阻、故障类型及对端系统阻抗变化的影响。大量的电磁暂态仿真结果表明,该算法具有很高的精度。     

Hybrid Traveling Wave/Boundary Protection for Monopolar HVDC Line

A novel hybrid protection algorithm, based on traveling wave protection principle and boundary protection principle for a monopolar HVDC line is proposed. Stationary wavelet transform (SWT) is adopted in the traveling wave protection to process the dc signal and then wavelet modulus maxima are used to further represent the useful traveling wave signal. The boundary protection principle based on SWT is used jointly with traveling wave protection to distinguish internal faults from external faults. The effect of border distortion, noise, high ground fault resistance, close-up faults, transients caused by lightning strokes and different dc line terminations are considered in the paper.      

一种用于行波保护的电压过零附近故障检测方法

当电压过零点附近发生故障时行波信号十分微弱,并且叠加在强大的工频量信号上,再加上各种干扰因素,实际中行波保护不能正确检测到行波波头,可能导致保护拒动或误动.文章对电压过零点附近故障与非电压过零点附近故障进行了大量的电磁暂态仿真,结果表明,电压过零点附近故障时电流行波的低尺度小波变换波形绝大部分远离时间轴,而非电压过零点附近故障时电流行波的低尺度小波变换波形绝大部分靠近时间轴.并根据这一特征提出了一种检测电压过零点附近故障的方法,仿真试验表明该方法可靠、有效.     

基于MSP430的低压电动机保护装置的设计及研究

基于MSP430的电动机保护装置是在传统的电机保护装置上集成了多种保护措施,实现了对低压电动机故障的判断和保护.本文系统地分析了电动机故障,通过以电流为判据,将电机保护分解为过流、负序和零序保护3大类,由此可基本覆盖电动机所有常见故障类型.本文介绍了保护装置采用的保护算法,使用带减法滤波的傅氏算法.硬件电路的构成及其特点也给予详细的介绍.最后提出了软件设计流程.经实验表明,该装置能在故障时有效地保护电动机.     

电动汽车电机驱动系统故障与失效模式分析

结合传统汽车故障与失效模式的分类方法,将电动汽车电机驱动系统的故障、失效模式进行了分析与总结归类,指出了故障发生的原因和相应的处理措施。基于电动汽车电机驱动系统的特殊性,将故障分为硬性故障和软性故障,提出了一套适合电动汽车电机驱动系统故障诊断与容错的控制策略。     

基于小波变换和ANN的最佳重合闸时刻的研究

目前对于线路瞬时性故障的最佳重合闸时刻以离线计算为主,如利用能量函数法,但其计算困难,计算时间较长,在电力系统中不能满足实际运行条件变化的要求。文中提出了一种基于小波变换和人工神经网络（ANN）方法的在线寻求瞬时性故障最佳重合闸时刻的方法,只需较短时间就能计算出最佳重合闸时刻。首先利用MATLAB对电力系统故障进行仿真,把故障信号通过小波变换分解成不同尺度下的“近似”分量（approximation）和“详细”分量（detail）,并把提取的特征值作为人工神经网络的输入量,进行训练,从而找到最佳重合闸时刻。算例验证了所提出方法的有效性和准确性。     

Directional relaying using support vector machine for double circuit transmission lines including cross-country and inter-circuit faults

The conventional distance relaying algorithms are unable to detect the inter-circuit faults, cross-country faults, high resistance faults which may occur in a double circuit line. This paper presents combined Discrete Wavelet Transform (DWT) and Support Vector Machine (SVM) based directional relaying and fault classification scheme including inter-circuit faults, cross-country faults and high resistance faults. SVM modules are designed for forward or reverse fault identification and fault classification using single terminal data. The 3rd level approximate discrete wavelet transform coefficients of three phase current signals only have been used. Proposed method is tested with variations in fault type, fault location, fault inception angle, fault resistance, inter-circuit faults, and cross-country faults. The proposed method based on SVM does not need any threshold to operate which is an exceptional attribute for a protective function. As SVMs are not based on comparing with some threshold, rather initially the SVMs are trained with the wide variety of fault patterns which is an offline process and then the trained SVMs are tested online to detect and classify the fault within short time. The test results show that all types of shunt faults can be identified within half cycle time. The proposed scheme offers both primary protection to 95% of the line section and also backup protection to 95% of the adjacent reverse and forward line section also.     

Development of novel adaptive single-pole autoreclosure schemes for extra high voltage transmission systems using wavelet transform analysis

A novel wavelet transform analysis-based adaptive single-pole autoreclosure (SPAR) scheme of extra high voltage (EHV) transmission systems is presented in this paper. The discrete wavelet transform is adopted to analyse the fault transients caused by the secondary arc and permanent faults and the numerical results reveal that certain wavelet components can be effectively used to detect and identify the fault relevant characteristics in transmission systems. A threshold-based decision logic for the wavelet analysis coefficients is used to distinguish the transient and permanent faults, and in the case of a transient fault, to determine the secondary arc extinction time. The outcome of the study clearly indicates that the wavelet transform analysis technique can be used as an attractive and effective means of developing an adaptive autoreclosing scheme.     

基于小波能量统计法的HVDC换相失败故障诊断

将小波变换应用于高压直流输电系统换相失败的故障诊断中,基于多分辨率分析分别对不同故障情况下的直流电压、直流电流、交流电压和交流电流等暂态信号进行分解,提取每一层的特征;根据各层小波能量统计,定义2个故障诊断指标作为辨识各种故障的判据,并针对这2个指标分别设置4个阈值以诊断直流线路故障和不同原因引起的换相失败故障。仿真结果表明,该方法不仅能准确区分换相失败故障和直流线路故障,而且能判断引起换相失败的原因。     

基于小波变换的开关磁阻电机系统功率变换器故障诊断

适用于开关磁阻电机(SRM)驱动系统的功率变换器是决定系统可靠性的关键环节,功率变换器的长时间故障运行会导致整个系统的崩溃,因此,功率变换器的故障诊断具有重要的作用。采用离散小波变换方法,提取故障相电流的平均值与标准差的比值作为诊断特征量,对功率变换器斩波管和位置管的4种故障类型进行分析和讨论,实现了故障类型的确定与故障器件的定位。最后通过仿真和试验验证了所提的故障诊断方法具有良好的可行性和有效性。     

Fault detection and isolation on a PWM inverter by knowledge-basedmodel

This paper presents an approach based on knowledge models to detect and isolate faults in a pulsewidth modulation inverter supplying a synchronous machine. These faults do not affect the system protection. A diagnosis system which uses only the input variables of the drive is presented. It is based on the analysis of the current-vector trajectory and of the instantaneous frequency in faulty mode. These two methods have been successfully applied to an experimental system     

Transmission line distance protection based on wavelet transform

Wavelet transform (WT) has the ability to decompose signals into different frequency bands using multiresolution analysis (MRA). It can be utilized in detecting faults and to estimate the phasors of the voltage and current signals, which are essential for transmission line distance protection. A digital distance-protection scheme for transmission lines based on analyzing the measured voltage and current signals at the relay location using WT with MRA is presented in this paper. The scheme has been tested by both computer simulation and experimentally. The tests presented include solid ground faults, phase faults, high impedance and nonlinear ground faults, and line charging.     

Diagnostics of eccentricities and bar/end-ring connector breakages in polyphase induction motors through a combination of time-series data mining and time-stepping coupled FE-state-space techniques

This paper develops the foundations of a technique for detection and categorization of dynamic/static eccentricities and bar/end-ring connector breakages in squirrel-cage induction motors that is not based on the traditional Fourier transform frequency-domain spectral analysis concepts. Hence, this approach can distinguish between the "fault signatures" of each of the following faults: eccentricities, broken bars, and broken end-ring connectors in such induction motors. Furthermore, the techniques presented here can extensively and economically predict and characterize faults from the induction machine adjustable-speed drive design data without the need to have had actual fault data from field experience. This is done through the development of dual-track studies of fault simulations and, hence, simulated fault signature data. These studies are performed using our proven time-stepping coupled finite-element-state-space method to generate fault case performance data, which contain phase current waveforms and time-domain torque profiles. Then, from this data, the fault cases are classified by their inherent characteristics, so-called "signatures" or "fingerprints." These fault signatures are extracted or "mined" here from the fault case data using our novel time-series data mining technique. The dual track of generating fault data and mining fault signatures was tested here on dynamic and static eccentricities of 10% and 30% of air-gap height as well as cases of one, three, six, and nine broken bars and three, six, and nine broken end-ring connectors. These cases were studied for proof of principle in a 208 V 60 Hz four-pole 1.2 hp squirrel-cage three-phase induction motor. The paper presents faulty and healthy performance characteristics and their corresponding so-called phase space diagnoses that show distinct fault signatures of each of the above-mentioned motor faults.     

混合式步进电机细分驱动系统建模及故障仿真

为提高步进电机细分驱动系统的故障诊断水平,在Simulink下建立了包含两相混合式步进电机本体、细分驱动、功率驱动及电流控制等模块在内的仿真模型。针对H型逆变桥臂四个功率开关管正常运行、短路及开路故障等状况进行了仿真,得到了相应的相电流波形。对各类故障进行了研究,分析了不同故障条件下电流波形的特征,分析结论为步进电机细分驱动系统的故障诊断提供了参考。     

边缘检测在HVDC系统故障诊断中的应用

为了及时分辨HVDC系统故障类型并快速恢复,对直流输电标准测试系统在各种故障,包括交流系统发生故障、逆变换相失败故障以及直流线路故障下的典型响应特性进行了分析。采用劋trous小波方法将行波信号分解成不同尺度下的小波面,其中包含了该尺度下细节信息,实现对故障的边缘检测;提出了3种故障判别准则,推出了模极大值能量的概念,并利用反射行波信号的小波变换模极大值的幅值、极性及模极大值能量等变化规律对不同HVDC系统故障进行诊断,实现逆变器换相失败和交流系统单相故障的识别。MATLAB仿真结果表明提出的方法能很好地完成HVDC系统的故障诊断。