Lyapunov指数法在故障电弧早期探测中的应用

故障电弧产生的伴生信号主要有弧光、短路电流、弧声.实验研究表明,弧前声音信号能作为故障电弧的早期表征信息,对弧前声音混沌时间序列进行相位空间重构,基于模型LE法确定混沌检测系统内置信号阚值,基于Lyapunov指数的故障电弧弧前声音信号混沌检测方法,能定量地识别湮没在复杂背景噪声中弧前声音信号.若最大Lyapunov指数大于零,表明由弧前声音信息产生,以弧前声音信息为判据提出弧前预警算法.     

解耦自适应反步法永磁直线同步电机混沌控制

针对永磁直线同步电机运行过程中存在的混沌动态行为,构建电机混沌模型,编写程序,计算其任意参数下的最大Lyapunov指数.通过分析电机的混沌动态特性,构造状态反馈解耦,降低混沌系统阶数.基于永磁同步电机的状态反馈解耦模型设计反步法混沌控制器.针对系统中可能含有的不确定性参数,提出解耦模型下的自适应反步法混沌控制,构造虚拟控制量,设计控制律,实时跟踪预测系统参数.为使系统状态快速稳定收敛至零点,构造Lyapunov方程进行稳定性分析.仿真结果表明,所提解耦自适应反步法能使永磁同步电机混沌系统快速恢复到稳定运行状态,鲁棒性强,响应速度快、控制精度高.     

基于多回路理论的同步电机定子绕组内部故障仿真的谐波分析

同步电机定子绕组发生内部电气故障时,气隙磁场中存在很强的空间谐波分量。采用多回路理论进行仿真分析,充分考虑了谐波分量的影响。准确的电感参数计算是多回路分析的基础,采用磁路的气隙磁导分析法计算电机故障后各电感参数,分析了谐波的计入次数对电感参数计算的影响,进一步分析了谐波对定子绕阻内部故障仿真结果的影响,并提出了工程中合理的谐波计算次数,既能保证计算精度,又可以减少计算工作量,从而具有较快的计算速度。通过对仿真波形的分析,得出结论:在进行同步电机定子绕组内部故障的仿真计算中,必须充分计及谐波的影响。     

能量变换器内部单相接地故障建模与分析

为了研究能量变换器(Powerformer)定子绕组内部短路故障,以直接相量法为基础建立了能量变换器定子绕组内部单相接地故障分析的数学模型,并给出了基于Matlab/Simulink的仿真模型.该模型不仅可以对能量变换器中性点经高阻接地和经消弧线圈接地情况进行仿真,还能对沿绕组内部不同位置处发生的故障进行仿真.对一台130kW/5kV的能量变换器仿真结果表明,中性点经消弧线圈接地的接地电流很容易达到安全电流以下;而且与同容量的常规发电机相比,能量变换器的故障电流远小于常规发电机.     

Qualitative analysis of an interrupted electric circuit with spike noise

Switching non‐ideality and its effects have been reported in DC‐DC converters. In this paper, we examine the qualitative property of an interrupted electric circuit with spike noise. First, we show the circuit model that have the switch interrupted by its own state and a periodic interval. Here, we artificially add spike noise via every switching action. Then, we explain its dynamics and derive the Poincaré map for the rigorous analysis in a circuit with ideal switching and a circuit with spike noise, respectively. Finally, we discuss the dynamical effects of spike noise from experimental and analytical viewpoints based on the Poincaré map and bifurcation diagrams. As a result, some dynamical effects of spike noise are clarified in terms of the invariant set, bifurcations, and existence regions of coexisting attractor. Copyright © 2010 John Wiley & Sons, Ltd.     

Complete bifurcation analysis of a chaotic attractor in an electric circuit with piecewise‐smooth characteristics

We investigate the bifurcation phenomena of chaotic attractors observed in electric circuits with piecewise‐smooth characteristics. First, we present a circuit model whose switching action depends on its own state and on the clock interval. Next, we explain the behavior of the waveform. Following this, we sample the waveform at every clock period to define the return map, which is vital for a detailed understanding of the circuit dynamics. Finally, bifurcation phenomena of chaotic attractors are classified into four cases with a focus on the invariant interval. In particular, we discuss the characteristics of each bifurcation phenomenon, and then clarify the bifurcation structure of the chaotic attractor. Moreover, some of the numerical results are verified experimentally. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

相复励旋硅式无刷同步励磁电机旋转二极管的故障监测

分析了相复励旋硅式无刷同步励磁电机旋转二极管的开路和短路状态，并以某大功率中速柴油发电机组为例，分析了其旋转二极管监测电路框图的工作原理，该监测电路在二极管开路时能延时发出信号，而在二极管短路时能迅速解列发电机，以维护机组的安全。最后对监测电路的实际性能进行了简要的说明和探讨。     

小波包与样本熵相融合的PMSM失磁故障诊断

为了研究永磁同步电机失磁故障最为敏感的特征量和区分故障频率来源,提出采用小波包与样本熵相融合的失磁故障诊断方法,研究该诊断方法的数学机理,并给出小波包分析定子电流频谱的详细步骤和小波包变换后最大能量频率子带样本熵的计算过程,通过比较样本熵的大小,确定故障频率来源。搭建实验平台,采集不同工况下的永磁同步电机定子电流数据,用该诊断方法进行分析,其结果表明,永磁同步电机失磁故障宜取5次、7次谐波作为故障特征量;样本熵的大小因电机运行状态不同而不同,可以确定故障频率来源于永磁同步电机失磁故障。     

虚拟同步机并网运行下电网谐波抑制和故障穿越策略

针对电网发生对称故障瞬间传统阻抗重塑型谐波电流抑制方法严重加剧虚拟同步发电机(virtual synchronous generator, VSG)故障电流的问题,介绍了传统阻抗重塑型谐波电流抑制方法的原理。基于电网不对称故障下VSG谐波阻抗模型,揭示了传统阻抗重塑型谐波抑制方法加剧VSG故障电流的机理。在此基础上,提出一种VSG谐波电流与故障电流协同抑制方法。通过引入虚拟电感重塑电网故障点至VSG的等效阻抗,实现了VSG并网运行下电网谐波和故障电流的协同抑制,有利于改善电网电能质量并提高VSG的故障穿越能力。最后,通过仿真验证所提控制策略的正确性和有效性。     

Calculation of equivalent circuit constants of synchronous machines considering field transient characteristics using DC decay testing method with open and shorted field windings

It has been reported that the calculated values of field transient behavior in a synchronous machine differ considerably from the measured values. This discrepancy is caused by the use of equivalent circuit constants in the standardized tests provided by JEC‐2130 and IEC‐60034‐4, in which the mutual leakage reactance between the damper and field windings is not accounted for. The authors have been studying a method for calculating equivalent circuit constants for the accurate simulation of transient behavior including the field winding side, by means of a standstill test with a small‐capacity DC power supply (DC decay testing method). The authors have previously presented a calculation method using operational impedances with the field windings opened, shorted, and shorted with an external resistance, obtained by the DC decay test. This paper presents a new method in which the external resistance used in our previous method is no longer needed. Instead, the field winding impedance is determined on the basis of its invariability against slip. The validity of the new method is demonstrated by comparing the calculated and measured values of the armature and field currents during a sudden three‐phase short‐circuit using 10 kVA/200 V/31.9 A/4 P/50 Hz test machines. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(2): 39–46, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21207     

Analysis and investigation of size spectrum of synchronous machines operating as wind-power-generators in the range of rotation frequencies of 75–300 rpm

The modern design tendencies of wind power generators based on synchronous machines with permanent magnets have been analyzed. It is shown that it is possible to create a spectrum of wind power generators with tangential magnetic flux and stator concentric windings in the range of rotation frequencies of 75–300 rpm. Some parameters of the developed generators are presented.     

具备内部故障仿真能力的永磁同步发电机电磁暂态建模与仿真方法

对永磁同步发电机(PMSG)内部定子绕组故障的精确建模与仿真有助于设计有效的状态检测系统和控制保护策略。首先对PMSG内部故障特征进行分析和详细的数学推导,给出了适合电磁暂态(EMT)建模的状态空间形式的动态方程。进而提出了一种PMSG内部故障EMT建模与仿真方法,并推导出其等效电路。利用MATLAB对推导出的方程进行了数值计算迭代求解,并在PSCAD/EMTDC中搭建了PMSG测试模型,与数值计算结果进行分析和对比验证。分析结果表明,PMSG内部故障会在短路路径中产生较大的循环故障电流,但是从发电机外部特性很难判断是否发生内部故障。对比验证结果表明,所建立PMSG内部故障EMT模型可准确反映内部故障特征,验证了所提建模方法的正确性。     

一种有效区分空投涌流与空投于故障的变压器保护新算法

在有功差动原理的基础上,提出一种基于变压器基波正序功率因数以实现变压器保护的新原理。该原理利用帕克变换,构造了d-q坐标系上变压器端口电压、电流的基波正序分量的旋转向量,进而可计算变压器在各种暂态过程中的基波正序功率因数。根据变压器基波正序功率因数的大小,来判断变压器是否发生内部故障。该原理基于能量守恒,物理意义清晰,算法简洁,无需任何先验参数,不受变压器接线方式的影响,易于工程实现。经仿真试验验证,新原理能够快速、可靠地切除变压器内部故障,在性能上优于传统的以波形特征为主的变压器保护原理,对空投轻微故障     

Required limiting impedance and capacity of fault current limiter installed in customer system with synchronous generator

We investigated the required limiting impedance and capacity of a fault current limiter (FCL) installed at an incoming feeder of a customer system with a synchronous generator in a utility distribution system. It was assumed that two types of FCL were installed, i.e. a resistive type (R‐type) FCL and an inductive type (L‐type) FCL. A fault current out of the customer system and a voltage in the customer system were calculated following a three‐phase, short‐circuit fault occurrence. It was found that the required type of FCL and the required limiting impedance depended on the rated capacity of the generator in order to obtain the suppression of the fault current under 0.1 kA_S and to maintain of customer voltage between 85 and 100% of the nominal voltage (6.6 kV). The capacity of FCL consisting of the smallest limiting impedance is discussed. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Research on a direct torque control for an electrically excited synchronous motor drive with low ripple in flux and torque

The electrically excited synchronous motor (ESM) has typically small synchronous inductance values and quite low transient values because of the damper windings mounted on the rotor. Therefore, the torque and stator flux linkage ripples are high in the direct torque control (DTC) drive of the ESM with a torque and flux linkage hysteresis controller (basic DTC). A DTC scheme with space vector modulation (SVM) for the ESM was investigated in this paper. It is based on the compensation of the stator flux linkage vector error using the space vector modulation in order to decrease the torque and flux linkage ripples and produce fixed switching frequency under the principle that the torque is controlled by the torque angle in the ESM. Compared with the basic DTC, the results of the simulation and experiment show that the torque and flux linkage ripples are reduced, the maximum current value is decreased during the startup, and the current distortion is much smaller in the steady-state under the SVM-DTC. The field-weakening control is incorporated with the SVM-DTC successfully. __________ Translated from Proceedings of the Chinese Society for Electrical Engineering, 2006, 26(7): 152–157 [译自: 中国电机工程学报]     

三峡发电机内部故障主保护及TA配置方案的研究总结

简单介绍了三峡左岸电站 14台发变组内部故障主保护及TA配置方案 ,对清华大学关于三峡发电机内部故障主保护及TA配置方案所做的工作进行了总结 ,从主保护配置方案的灵敏性、发电机中性点侧TA的数目等方面对两种保护方案进行了对比 ,为三峡工程今后的工作提供借鉴。     

Eccentricity Fault Diagnosis and Torque Ripple Analysis of a Four-pole Synchronous Reluctance Machine in Healthy and Faulty Conditions

Abstract—In this research, torque ripple is analyzed, considering both slot opening and distributed winding effects for a 4-pole 60-slot synchronous reluctance machine under healthy and eccentricity fault conditions. Mathematical-based models and numerical methods are used to study the behavior of the machine, especially when it is supplied with a voltage source. For this purpose, the parameters of the machine are computed in both healthy and eccentricity fault conditions using the winding function theory. This article proposes a method that deals with both dynamic and static eccentricity fault diagnosis using a vibration signature; consequently, the results demonstrate that the eccentricity fault has no significant effect on the machine's current signature. Moreover, unbalanced magnetic pull is computed considering eccentricity fault, and then mechanical instability is proven to occur under such circumstances. It should be noted that previous works were generally based on the finite-element method, and current sources were used as suppliers; in this article, a mathematical-based model is utilized and voltage sources are considered as suppliers, which are two main advantages of this article over previous ones. Verification carried out by simulation via the finite-element method supports the effectiveness of the model and control approach.     

Studies of characteristics and design of superconducting fault current limiter with adjustable trigger current level in current limiting operation

Superconducting fault current limiters (SCFCLs) are expected to improve not only reliability but also stability of power systems. To introduce an SCFCL in a power system, various specifications such as trigger current level, impedance in current limiting operation, recovery time, and so on are necessary. Fault analyses point out that accuracy of the trigger current level is necessary. Therefore, an SCFCL of a transformer type with adjustable trigger current level was proposed and manufactured. Using the trial SCFCL, adjustability of the trigger current level was confirmed. It is found that the SCFCL has good limiting and recovery characteristics. In this paper, characteristics of the SCFCL are considered from a design point of view. Most of the specifications necessary for design depend on the characteristics in current limiting operation. Therefore, the characteristics of the SCFCL in current limiting operation are discussed. It is shown that this kind of SCFCL has good property for easy design, and its design principle is summarized. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(3): 30–38, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10054