发电机内电势相角与功角的测量方法及应用

传统的发电机内电势与功角通过实时测量发电机端电压电流以及发电机直轴电抗Xd和交轴电抗Xq计算得到.由于发电机在不同运行状态下Xd,Xq发生变化,产生计算误差.为此,提出一种转子位置测量法,利用发电机组的键相脉冲信号和机端电压来测量发电机内电势相角与功角.该方法不受发电机等效计算模型和同步电抗参数误差的影响,具有较高的精度,适用于电网扰动和暂态过程的实时功角测量.     

基于转子位置传感器的同步发电机■波形实时生成方法

同步发电机空载电势■的有关参数对电力系统的运行与控制都是非常重要的,但是,目前现场的监控装置想要得到■的相关参数仍然存在困难。文中提出一种基于转子位置传感器的同步发电机■波形的实时生成方法,依据该方法开发的装置能够输出频率和相位都与空载电势■一致而幅值恒定的正弦电压信号,从而使得现场的监控装置能够像测量发电机机端电压那样方便地测量空载电势■的有关参数。详细地介绍了这种方法的工作原理和实现技术。     

基于转子位置传感器的同步发电机Eq波形实时生成方法

同步发电机空载电势Eq的有关参数对电力系统的运行与控制都是非常重要的,但是,目前现场的监控装置想要得到Eq的相关参数仍然存在困难.文中提出一种基于转子位置传感器的同步发电机Eq波形的实时生成方法,依据该方法开发的装置能够输出频率和相位都与空载电势Eq一致而幅值恒定的正弦电压信号,从而使得现场的监控装置能够像测量发电机机端电压那样方便地测量空载电势Eq的有关参数.详细地介绍了这种方法的工作原理和实现技术.     

同步发电机中不可直接测量量的左逆软测量方法

研究了同步发电机中一些不可直接测量量（功角、 dq轴暂态电势、dq轴电流分量等）的动态软测量问题。首先,建立了适合于软测量分析的同步发电机模型,该模型充分包含了同步发电机中的一些可直接测量量（如有功功率、无功功率、电流幅值等）,且是一类特殊的非线性微分 — 代数子系统。接着,针对所建立模型的特殊性,给出了适合此模型的推广的左逆软测量算法。然后,具体针对同步发电机的4阶实用模型设计了软仪表,实现了模型中所有不可直接测量量的软测量。最后,基于MATLAB/SimPowerSystems软件进行了数值仿真,用6阶次暂态模型模拟真实的同步发电机,验证了所提出的方法的有效性。     

永磁往复式发电机的磁场参数计算

为准确计算永磁往复式发电机运行时的电磁参数,基于二维有限元法,在考虑端部效应的情况下,建立了发电机的静态磁场数学模型,给出了在静态场下计算发电机运行一周期内电磁参数的方法,并计算了发电机的空载电势、同步电抗以及空载和负载电磁力。仿真及实验结果表明,该方法计算得到的数据与实测数据相比误差较小,避免了瞬态分析运算时间长的问题。     

基于估算对侧电源阻抗的自适应距离保护算法

在系统两端电源电势幅值比相等的假设下,基于故障前电源电势与负荷电流之间的相位关系合理地估算出对侧电源阻抗值.利用传统距离保护的测量阻抗和保护处实时相量建立起计算线路故障电抗和电阻的自适应数学模型,2个模型都为正序电流分支系数的相角的函数.根据测量阻抗的电抗分量和电阻分量与正序电流分支系数的相角之间的增减关系分别提出了防止保护拒动和超越的解决办法.仿真结果证明,这种距离保护性能令人满意,提高了保护的可靠性和灵敏度.     

不同工况下永磁同步风力发电机饱和同步电抗的计算与分析

以一台400W永磁同步风力系统所用发电机为例,给出了不同工况下电机内电磁场的求解方法,计算了永磁体嵌入转子表面结构的永磁同步发电机的饱和同步电抗值,在此基础上进一步分析了不同运行工况下永磁同步风力发电机同步电抗参数的变化规律,并进行了相应的实验验证,可为控制系统的设计及风力发电机运行性能的进一步研究提供参考。     

计及双因素非线性影响的汽轮发电机同步电抗的计算方法

汽轮发电机不同负载运行条件下的气隙电势与合成磁势的关系是与空载特性之间存在明显差异的一个曲线族。这种差异主要是由磁路饱和与磁场畸变双因素非线性共同作用引起的。该文以有限元方法为工具,研究不同功角时计及双因素非线性的定子绕组电感系数随转子角变化的特
　　点,并比较分析其与不计饱和值之间的差异。提出一种通过寻求随转子角变化的定子电感矩阵的特征值来获取同步电抗的方法,该方法不仅能考虑双因素非线性和转子的运动,还能充分考虑定子电感系数的特点。用该方法计算的同步电抗都比制造厂给出的参数要小。计算定子电流的实例研究表明,用计及双因素非线性的同步电抗的计算结果与直接采用有限元方法的计算结果更接近。     

基于DSP的自适应电流速断保护中系统参数实时计算的实现

提出了基于DSP的自适应电流速断保护中系统参数实时计算的实现方法,同时给出了硬软件的设计。在系统发生故障时采用带补偿的全波傅氏算法,实时计算出系统的等值内电抗,然后再利用记忆在计算机存储器中的故障前的测量电压、电流采样值来计算系统等值内电势的相电势幅值。分析表明该方法能够满足数据的实时处理和精度要求。     

运行电压下用转差法测量200MW发电机的同步电抗

通常在电力系统的理论计算分析中,发电机的同步电抗用的是设计值,认为汽轮发电机的定子与转子之间的气隙是均匀的,转子磁路是对称的,因而一般取同步电抗值x_d=x_q或者x_d≈x_q。但在实际运行中,发电机的铁芯处于接近饱和状态;转子结构上也有大齿和小齿之差,所以同步电抗的设计值与发电机在运行中的实际值有一定差别,而且,     

Determination of Synchronous Reactance and No‐Load Saturation Curve of Synchronous Machines by dc Test Considering Magnetic Saturation Effect

dc Tests can accurately determine the unsaturated synchronous machine‐equivalent circuit constants by a simple standstill test. This paper presents two improved dc tests that account for the magnetic saturation of the stator iron core by the main flux. These tests are tentatively named Step Response Test (I) and Step Response Test (II). The former can predict the incremental d‐axis synchronous reactance by performing a Fourier transform of the voltage and current measured when a small step voltage is applied to the two armature terminals as a field current flows. The latter can determine the incremental d‐ and q‐axes synchronous reactances by the same Fourier transform of the voltage and current measured when a small step voltage is applied to the two armature terminals as an armature current flows. In addition, this paper introduces a new method to calculate not only the static d‐ and q‐axes synchronous reactances but also the no‐load saturation and short‐circuit characteristic curves. This new method does not require the results from any additional tests including the rotational driving tests and dimensional information, which can only be obtained from the manufacturer. To demonstrate the validity of the proposed method, results of an experiment using 10‐kVA laminated synchronous machines with damper winding are presented.     

An extension of delta method to synchronous machine transient stability study

Contents The delta method is applied to solve the transient stability problem of a synchronous machine connected to an infinite bus. In the machine analysis emphasis is placed on the governor action or flux-decay effect. The swing equation of the machine is a third-order non linear differential equation. In the paper the delta method is extended to this third-order nonlinear swing equation. — The system trajectory and the critical clearing time of the system have been obtained. A numerical example is given.

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Anwendung der Delta Methode zur Untersuchung der transienten Stabilität einer Synchronmaschine

Übersicht Das Problem der transienten Stabilität einer Synchronmaschine, die an einem starren Netz angeschlossen ist, wird durch die Delta Methode untersucht. Besonders wird das Abklingen des magnetischen Durchflusses und der Einfluß der Reglertätigkeit untersucht. Die Schwingung der Maschine wird durch eine nichtlineare Differentialgleichung dritter Ordnung beschrieben. Die Delta Methode wird zur Anwendung dieser nichtlinearen Schwingungs-differentialgleichung dritter Ordnung erweitert. Die Systemtrajektoren und die kritische Abschaltzeit des Systems werden dadurch abgeleitet. Ein numerisches Beispiel folgt.

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List of principal symbols x _d direct-axis transient reactance - x _d, x_q direct-axis and quadrature-axis synchronous reactances - x _l reactance of each transmission line - x ₁₂ total reactance between generator terminals and infinite bus - measure of the distance of the fault from the machine terminals - rotor angle with respect to a synchronously rotating reference - E _q instantaneous voltage proportional to field flux linkage - E _ex exciter voltage refered to armature circuit - E voltage of infinite bus - M inertia constant of the machine - P _d damping coefficient - P _mx amplitude of power/angle curve - P _i mechanical input power - T _d equivalent time constant of the governor - T _d0 open-circuit transient-time constant of the generator - K _g loop gain of the governor system - - ₀ 2f ₀ - t _cl clearing time - t _cr critical clearing time - _s stable equilibrium rotor angle     

一种同步发电机进相运行时功角的计算方法

功角是判断机组运行稳定的一个重要参量.提出一种在进相运行工况下,实时计算发电机功角的新方法,该方法采用发电机运行中的实时同步电抗,并综合考虑变压器、线路等外部回路参数.通过试验及实际验证该方法具有很好的精度.     

基于改进信号注入法的配电网电容电流测量方法

本文提出了一种改进的信号注入法,解决现有在测量中性点不接地配电网电容电流时未考虑零序电压而精度不高的问题。该方法通过测量不同情况下电压互感器开口三角端的电压值来求解系统的对地电容,采用计及互感器绕组漏抗和系统零序电压的戴维南等效电路模型。该方法操作简单,具有较高测量精度。通过仿真计算和实际应用,验证了该方法在系统不平衡情况下测量电容电流的准确性和适用性。     

SVPWM逆变器供电时FSCW-PMSM损耗特性研究

为探究空间矢量脉宽调制(space vector pulse width modulation,SVPWM)逆变器引入的时间谐波电流对分数槽集中绕组永磁同步电机(fractional-slot concentrated-winding permanent magnet synchronous machine,FSCW-PMSM)损耗特性的影响,文中提出一种SVPWM逆变器与FSCW-PMSM联合系统中电机损耗谐波特性分析方法。首先,理论分析了考虑时间谐波电流时电机损耗的时空谐波特性。其次,以一台三相双层绕组10极12槽PMSM为例,搭建电机与SVPWM逆变器的场路联合仿真模型,求解样机在恒转矩和恒功率调速时损耗的谐波特性,揭示各谐波损耗的产生机理。结果表明：转子谐波损耗由基波电流与次谐波、iZ±p次齿谐波和(f_c±4f)/f、(f_c±2f)/f次时间谐波电流与p、Z±p次空间谐波引起;定子铁芯谐波损耗由基波磁场、谐波励磁磁场及(f_c±4f)/f、(f_c±2f)/f次时间谐波电流引起。该结论适用于其他极槽组合的FSCW-PMSM。最后,通过实验验证了该分析方法的有效性。     

Measurement of dynamic magnetic loss parameter in ferrites

The measurement of the iron loss in ferrites is important for developing high‐efficiency switching power supplies. The authors have proposed the dynamic magnetic loss parameter, λ_f, for evaluating the iron loss in ferrites. In previous studies, the parameter was assumed to be a constant value for an individual ferrite material and defined for one period of a small B–H loop. In this paper, assuming that λ_f is a function of the time derivative of the magnetic flux density, dB/dt, a novel measurement method of λ_f of a Ni‐Zn ferrite is proposed using rectangular wave voltage excitation and the Fourier expansion of the exciting current. In order to realize an iron loss measurement system with the rectangular wave voltage excitation, a high‐frequency FET inverter has been developed. The results of measuring λ_f show that it is uniquely determined by dB/dt regardless of the B–H loop size. The measured dB/dt characteristics of λ_f are applied to practical examples for switching power supplies and sinusoidal wave voltage excitations. Their experimental and computational results coincide and it is clarified that the measured dB/dt characteristics are effective and useful. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(1): 1–6, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20101     

Elimination of Low-speed Vibration in Vector-controlled Permanent Magnet Synchronous Motor by Real-time Adjusted Extended Kalman Filter

The inaccuracy and delay of speed feedback cause a vibration problem when the permanent magnet synchronous motor runs at low speed. As the low-speed smoothness is a key point of many applications of the permanent magnet synchronous motor, this article solves this problem by adding a real-time adjusted extended Kalman filter to low-precision-sensor vector control. In the mathematical model, the estimated speed of the extended kalman filter is significantly impacted by the deviations of the resistance and magnetic flux rather than other parameters. Thus, under i_d = 0 vector control, a R_s-ψ_f-identifier is designed to calculate the values of the resistance and flux simultaneously with a small compensating i_d. This algorithm runs on the platform in real time. Finally, the experiment results validate that when the velocity reaches as low as 1 r/min, the proposed method eliminates the vibration problem in the low-precision-sensor permanent magnet synchronous motor.     

基于PMU的发电机参数量测对电网输送能力提高的研究

针对目前难以获得同步发电机实际运行工况参数的问题,利用同步相量测量单元（PMU）能直接测量发电机的功角以及机端电压和电流相角的特点,计算获得发电机实际运行的同步参数xd。将该直接测量的发电机运行参数运用于电力系统仿真计算,可提高电力系统暂态功角稳定水平和输电能力,同时也提高了系统的静态功角稳定水平。通过算例表明了此方法的实用性和方便性。     

发电机定子绕组端部振动静态特性的试验研究

对发电机定子绕组端部振动静态特性进行了试验研究,提出了发电机定子绕组鼻端头部自振静频率落入100H。共振的危险性取决于其振幅的大小,给出了间接判断发电杌定子绕组鼻端头部静频率振幅大小的方法;分析了当发电杌定子绕组端部椭圆形振动落入100Hz附近时,应根据发电杌的历史状况来决定其处理的方法．     

Determination of excitation parameter limits for generator dynamic stability

Contents The voltage regulator and the excitation system are known to affect strongly the dynamic stability of a synchronous generator. This effect is often detrimental, sometimes leading even to dynamic instability. This paper concentrates on determining the excitation system parameter values for which the generator's dynamic stability becomes marginal. This defines a stable and an unstable region in the space of the dominant excitation system parameters, namely the transient or the steady state gain and the dominant time constant of the excitor-voltage regulator system. In the case of a first order excitation system model, the stability limits can be determined analytically in the form of an inequality constraint. A fourth order excitation system is also examined but this time the stability limits are computed using the concept of the gain margin. The determination of the stable region in the parameter space is an extremely useful tool for the proper selection of excitation system parameter settings.

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Bestimmung von Grenzen der Erregerparameter für dynamische Stabilität von Generatoren

Übersicht Erregersystem und Spannungsregler beeinflussen bekanntlich die Stabilität von Synchrongeneratoren beträchtlich. In dem Beitrag werden Parameter des Erregersystems, insbesondere die Verstärkung und die dominante Zeitkonstante an der Stabilitätsgrenze berechnet. Nach einem Erregermodell erster Ordnung wird ein solches vierter Ordnung behandelt. Die Darstellung mittels Stabilitätskarten kann als Hilfsmittel bei der Parameterwahl genutzt werden.

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List of principal symbols p time derivative of flux linkage - S apparent power - P real power - Q reactive power - X _d steady state direct axis reactance - X _q steady state quadrature axis reactance - X _d transient direct axis reactance - direct axis transient open circuit time constant - H stored energy constant (sec) - r _e total external resistance - X _e total external reactance