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1、Measurement of a power system nominal voltage, frequency and voltage flicker parametersA.M. Alkandari a, S.A. Soliman b,* a b s t r a c t:We present, in this paper, an approach for identifying the frequency and amplitude of voltage flicker signal that imposed on the nominal voltage signal, as well a
2、s the amplitude and frequency of the nominal signal itself. The proposed algorithm performs the estimation in two steps; in the first step the original voltage signal is shifted forward and backward by an integer number of sample, one sample in this paper.The new generated signals from such a shift
3、together with the original one is used to estimate the amplitude of the original signal voltage that composed of the nominal voltage and flicker voltage. The average of this amplitude gives the amplitude of the nominal voltage; this amplitude is subtracted from the original identified signal amplitu
4、de to obtain the samples of the flicker voltage. In the second step, the argument of the signal is calculated by simply dividing the magnitude of signal sample with the estimated amplitude in the first step. Calculating the arccosine of the argument, the frequency of the nominal signal as well as th
5、e phase angle can be computing using the least error square estimation algorithm. Simulation examples are given within the text to show the features of the proposed approach.Keywords: Power quality Nominal frequency and amplitude measurements Voltage flicker Frequency and amplitude estimation Forwar
6、d and backward difference1. IntroductionVoltage flicker and harmonics are introduced to power system as a result of arc furnace operation, and power utilities are concern about their effects. As such an accurate model for the voltage flicker is needed. The definition of voltage flicker in IEEE stand
7、ards is the impression of fluctuating brightness or color, when the frequency observed variation lies between a few hertz and the fusion frequency of image” 1. The flicker phenomenon may be divided into two general categories, cyclic flicker and non-cyclic flicker. Cyclic flicker is repetitive one a
8、nd is caused by periodic voltage fluctuations due to the operation of loads such as spot welders, compressors, or arc welders. Non-cyclic flicker corresponds to occasional voltage fluctuations, such as starting of large motors, some of loads will cause both cyclic and non-cyclic flicker, such as arc
9、 furnace, welder, and ac choppers.Over the past three decades, many digital algorithms have been developed and tested to measure power system frequency and rate of change of frequency. Ref. 2 presents the application of the continuous Wavelet transform for power quality analysis. The transform appea
10、rs to be reliable for detecting and measuring voltage sags, flicker and transients in power quality analysis. Ref. 3 pays attention to the fast Fourier transform and its pitfalls. A low pass.digital filter is used, and the effects of system voltage deviation on the voltage - flicker measurements by
11、direct FFT are studied. The DC component leakage effect on the flicker components in the spectrum analysis of the effective value of the voltage and the windowing effect on the data acquisition of the voltage signal are discussed as well.A digital flicker meter is proposed in Ref. 6 based on forward
12、 and inverse FFT and on filtering, in the frequency domain, for the implementation of the functional blocks of simulation of lampeyebrain response. Refs. 57 propose a method based on Kalman filtering algorithms to measure the low frequency modulation of the 50/60 Hz signal. The method used, in these
13、 references, allows for random and deterministic variation of the modulation. The approach utilizes a combination of linear and non-linear Kalman filter modes.Ref. 8 presents a method for direct calculation of flicker level from digital measurements of voltage waveforms. The direct digital implement
14、ation uses Fast Fourier transform (FFT) as the first step in computation. A pruned FFT, customized for the flicker level computation, is also proposed. Presented in Ref. 9 is a static state estimation algorithm based on least absolute value error (LAV) for measurement of voltage flicker level. The w
15、aveform for the voltage signal is assumed to have, for simplicity, one flicker component. This algorithm estimates accurately the nominal voltage waveform and the voltage flicker component. An application of continuous wavelet transform (CWT) for analysis of voltage flicker-generated signals is prop
16、osed in Ref. 10 With the time-frequency localization characteristics embedded in the wavelets, the time and frequency information of a waveform can be integrally presentedRef. 11 presents an arc furnace model that implemented in the Simulink environment by using chaotic and deterministic elements. This model is obtained by solving the corresponding differential equation, which yields dynamic and multi valued v i characteristics of the arc furnace load. In order to evalu
