共查询到20条相似文献,搜索用时 31 毫秒
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Girgis A.A. Baldwin T.L. Makram E.B. Fortson H.S. Jr. 《Industry Applications, IEEE Transactions on》1990,26(4):689-695
Computer-based testing of a three-phase induction watthour meter in the presence of harmonic distortion is reported. Two three-phase harmonic generators produce the distorted current and voltage waveforms. Each waveform consists of prespecified harmonic magnitude and phase. Therefore, balanced or unbalanced conditions can be simulated in the testing. A fiber optic sensor is designed to convert the rotation of the disk of the meter into digital signals to be stored in an IBM PC/AT. A data acquisition system transfers the samples of current and voltage waveforms to compute the power and energy for comparison. Presented are: the computer-based harmonic generator facilities for testing, the testing procedure, and the impact of the different harmonics magnitude and phase angle on the meter's registration error 相似文献
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感应型电能表在畸变波形下的数学模型 总被引:1,自引:0,他引:1
本文从感应型电能表基本结构和工作原理出发,建立了电能表在畸变电压和电流作用下的数学模型,并通过对某工业谐波点的实测结果分析,验证了模型的正确性。 相似文献
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谐波对感应式有功电度表计量误差的影响 总被引:4,自引:1,他引:4
建立一种感应式有功电度表在谐波电压和谐波电流状况下计算计量误差的非线性数学模型。用该模型可分析谐波对感应式有功电度表计量误差的影响。计量误差考虑了电度表电压线圈和电流线圈在不同的谐波次数以及谐波大小时的非线性效应。按照数学模型用C语言编制了程序,计算结果表明:输入电压和输入电流中的谐波会引起较大的电度表计量误差,实验结果也证明了这一结论。 相似文献
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电力企业在处理计量故障时,原有计算更正系数及追补电量方法的应用对象主要是机械式感应电能表,随着多功能电子式电能表技术的大面积运用,由于电能表电压回路内部结构原理的不同,在失压时对计量的影响与感应式电能表有很大区别。通过多年工作经验总结出了三相三线多功能电子式电能表在各种失压状态下的运行情况及如何正确进行有功、无功退补电量的K值计算方法。 相似文献
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The sensitivity of television sets, induction watthour meters and universal motors to harmonics and fractional harmonics, as they occur in home appliances, is derived analytically and experimentally. This study shows that television sets are very sensitive to fractional harmonics. Calculations and measurements performed with single-phase watthour meters show that the harmonic torques within the aluminum disk are always positive and accelerate the disk. Universal machines are not as sensitive to voltage harmonics as compared with induction machines. The work described has been supported by the U.S. Department of Energy. 相似文献
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电压型逆变器输出的电压和电流波形中含有大量谐波,导致异步电动机低速时的转矩脉动和转速波动。文章在分析高次时间谐波产生的谐波脉动转矩基础上,介绍了用虚位移原理计算感应电动机谐波脉动转矩的方法。编制了感应电动机转矩的计算机程序,并用一计算实例对电动机谐波转矩进行了分析和计算。 相似文献
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A dc motor drive is controlled by varying the armature current and field current. The field is a measure of flux, and the armature current times field current is a measure of torque. Various approximate means of estimating the flux and torque levels in an induction motor exist. Most of these methods are sensitive to motor parameter value changes and do not work well near zero speed. Also, the harmonics in the motor voltage and current due to the nonsinusoidal inverter waveform cause errors in the estimated torque. A practical method has been developed to measure the flux level in an induction motor in the actual operating environment. Using the flux signals and stator current, the actual electromagnetic torque can be obtained. This torque signal responds correctly to motor saturation and inverter voltage waveform harmonics. The motor can be designed to operate without the customarily required flux margin, since the flux level is accurately controlled. The control strategy for use with these feedback signals does not require the use of a tachometer. 相似文献
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针对电网背景低次谐波引起的双馈风电机组定子电流畸变、功率及电磁转矩脉动,建立了能够反映电网5、7次谐波电压下双馈发电机的特征谐波模型,揭示了电网背景谐波电压对双馈发电机功率与电磁转矩脉动的影响机理。通过双馈发电机控制目标分析,提出了基于比例-积分-谐振(PIR)调节转子电流内环的双馈发电机双闭环控制策略,有效地消除了双馈风力发电机定子输出电流中的5、7次谐波和电磁转矩脉动。在Matlab/Simulink中建立了1.5 MW双馈风电机组仿真模型,实现了风电机组谐波运行与抑制的全过程仿真。利用电网谐波发生模拟装置,进行了双馈机组谐波运行与抑制现场试验,仿真与现场试验证明了理论分析的正确性与谐波抑制策略的有效性。 相似文献
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谐波对感应式电能表计量影响与对策 总被引:2,自引:0,他引:2
非线性负荷产生的大量谐波注入电网后会使得电力系统中的电压和电流波形产生严重畸变,从而对计量仪表等产生不同程度的影响。文章介绍了谐波产生的原因及其对感应式电能表的影响,分析了由于谐波存在对感应式电能表计量误差的影响情况,并提出了减少感应式电能表电能计量误差的方法和对策。 相似文献
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This paper is concerned with the accuracy of registration of induction watthour meters when metering non-sinusoidal currents. Expressions are given for the meter registration errors for three cases of nonsinusoidal current wave forms: (1) full wave, phase triggered sinusoid (2) full wave, phase delayed square wave (3) full wave, battery charger wave errots in registration are found to be a function of the harmonic distortion of the impressed current and the ratio of impressed rms current to rated or class current. A generalization of this study is made, relating error to these two variables. It is suggested that a bound on the product PH?k will similarly bound registration error. PH is the per unit harmonic distortion of the current and k is the per unit rms current in the watthour meter. 相似文献
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Abbas Mohamed A. Christen Roland Jahns Thomas M. 《Industry Applications, IEEE Transactions on》1984,(5):1251-1259
A six-phase six-step voltage-fed induction motor is presented. The inverter is a transistorized six-step voltage source inverter, while the motor is a modified standard three-phase squirrel-cage motor. The stator is rewound with two three-phase winding sets displaced from each other by 30 electrical degrees. A model for the system is developed to simulate the drive and predict its performance. The simulation results for steady-state conditions and experimental measurements show very good correlation. It is shown that this winding configuration results in the elimination of all air-gap flux time harmonics of the order (6v ±1, v = 1,3,5,...). Consequently, all rotor copper losses produced by these harmonics as well as all torque harmonics of the order (6v, v = 1,3,5,...) are eliminated. A comparison between-the measured instantaneous torque of both three-phase and six-phase six-step voltage-fed induction machines shows the advantage of the six-phase system over the three-phase system in eliminating the sixth harmonic dominant torque ripple. 相似文献
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ABSTRACT This paper gives a study of line harmonics generated by three-phase half controlled bridge converters feeding separately excited D.C. motor. Analytical expressions for line current are given and dominant current and voltage harmonics have been computed for a typical system. The study shows that current has predominant low order harmonics, the second harmonic being significantly large as compared to other harmonics. The line voltage, however, has significant higher order harmonic components as well Line current harmonics are dependent on motor operating speed, whereas the voltage distortion factor is nearly independent of speed. On the other hand, percent current harmonics are nearly independent of torque, but the voltage harmonics and voltage distortion factor are dependent on load torque. 相似文献
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The ANSI Standard equation for overall accuracy places a small amount of emphasis on light load accuracy for watthour meters. Results from a recent load research study indicated a significant amount of energy is accumulated at lighter loads where watthour meter accuracy is poorer. Perhaps the standard equation for overall accuracy is a consensus of opinions prior to utilities performing load research studies. Although small inaccuracies of watthour meters at lighter loads may seem insignificant, they become large when applied to an entire meter population. ANSI C12.1-1982 may be interpreted to mean that 20% of all energy registration occurs at light load. The results of a load research study show that watthour meters spend a great deal of time at light loads. A method was developed to establish at which loads watthour meters register energy consumption. Watthour meters spent 85% of the time and registered more than 40% of the total energy for a one year period at light loads. 相似文献
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扭矩扳子自动化检定装置用低速永磁同步电机通常工作于300 r/min以下,由于电机本体气隙磁场畸变、逆变器死区时间、开关管压降等非线性因素,电机在运行过程中会产生高次谐波,引起转矩脉动,导致加载过程中输出扭矩波动,影响检定过程。针对上述问题,提出了一种针对低速永磁电机的谐波抑制控制策略,建立了低速永磁电机的谐波数学模型,采用电压补偿的方法,根据谐波数学模型计算谐波电压补偿量,并采用PI控制,对电机运行过程中的相电流谐波进行抑制,从而减小扭矩扳子自动化检定装置的转矩脉动。通过仿真表明,该方法可以显著降低谐波,从而减小电机输出转矩脉动。 相似文献
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针对主动配电网,构建了考虑谐波影响的量测系统模型,并分析了其对配电网状态估计影响。首先,介绍了主动配电网谐波源的电流源模型,并阐述了在MATLAB/Simulink仿真环境下构建谐波源模型的步骤。其次,建立了电压量测回路和电流量测回路的模型,详细介绍了各自电缆的频率特性,并根据现有的电子式电能表工作原理给出了功率量测的计算公式,建立了完整的量测系统,对量测误差进行了分析。最后,通过仿真并利用IEEE 13节点配电网络从电缆长度、谐波次数、非线性负荷等多个方面详细分析了各因素对配电网量测及状态估计的影响。 相似文献
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A steady-state analysis is presented of a permanent magnet (PM) synchronous motor drive with a current source inverter (CSI). The torque-speed profile required of the drive is a constant torque region from zero to base speed and a constant power region above base speed. The analysis assumes position feedback control. Optimum control strategies are obtained for the two regions of the torque-speed profile. Using these optimum strategies, performance curves of the drive are predicted and experimentally verified. The time harmonics in the motor are a function of the presence and configuration of the dampers in the motor. An expression is obtained for the equivalent inductance seen by the harmonics for different damper configurations. A Fourier series approach is used to predict the line-to-line voltage waveforms. Even though the presence of the dampers is not essential to the operation of the drive, their presence reduces the voltage spikes present in the line-to-line voltage. 相似文献