JPH07325117A - Digital flicker meter - Google Patents

Abstract

PURPOSE:To enhance accuracy in the measurement without prolonging the data processing time by differentiating the sampling time for effective voltage value from that for subjecting the flicker fluctuation voltage to frequency analysis. CONSTITUTION:The digital flicker meter comprising an A/D converter 1 and a personal computor 2 samples voltage effective values from a power system and analyzes the frequency thereof to determine a flicker fluctuation voltage DELTAVn which is then employed, along with a flicker sensitivity coefficient an, in the measurement of a flicker management index DELTAV10 as shown by a formula. In this regard, the sampling time for effective voltage value is differentiated from that for frequency analyzing the flicker fluctuation voltage DELTAVn. Consequently, the sampling point for frequency analyzing the flicker fluctuation voltage DELTAVn can be superposed on the sampling point of effective voltage value and when the effective voltage value lowers in a high flicker frequency region, it can be corrected using a predetermined correction coefficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital flicker meter including an A / D converter and a data processing device.

[0002]

2. Description of the Related Art Conventionally, a voltage effective value Ve in a voltage system is used.
The flicker of the illumination due to the fluctuation of the so-called flicker is an important problem in the power quality, and ΔV10 as shown in the following equation (2) is one of the management indexes thereof.

[Equation 2]

In the equation (2), ΔVn represents the fluctuation (effective value) of the voltage fluctuation component of the fluctuation frequency fn obtained as a result of frequency analysis of the voltage fluctuation, as shown in FIG. 3, for example.
As shown in FIG. 4, an represents a luminosity factor corresponding to the fluctuating frequency fn. It can be said that ΔV10 indicates the time variation of electric energy, but as a meter for measuring the control index ΔV10, an analog or analog / digital type has been widely used conventionally. Also, the measured ΔV10
Is compared with a predetermined set value, and if it is less than a predetermined value, it is judged to be good, and if it is more than the predetermined value, it is judged to be bad.

[0004]

Since the conventional analog type is a meter for exclusive use of flicker, it has a problem that it is not versatile and cannot be used for various purposes. Further, the digital type has an advantage that it can be used as a multipurpose meter by one device, but on the other hand, if it is attempted to improve the measurement accuracy, the data processing time becomes long and the practicality becomes poor.
Therefore, an object of the present invention is to improve the measurement accuracy without prolonging the data processing time while being digital.

[0005]

In order to solve such a problem, according to the present invention, an A / D converter and a digital processing device are provided, a voltage effective value is sampled from an electric power system, and this is subjected to a frequency analysis process. The flicker fluctuation voltage ΔV
The flicker management index ΔV1 represented by the following equation (3) is obtained from n and the flicker flicker visibility coefficient an.
In a digital flicker meter for measuring 0, the sampling time of the voltage effective value and the sampling time when the flicker fluctuation voltage ΔVn are subjected to frequency analysis processing are different from each other.

[Equation 3]

In the present invention, the sampling point when the flicker fluctuation voltage ΔVn is subjected to the frequency analysis processing can be made to overlap the sampling point of the voltage effective value, or the voltage effective value can be the flicker frequency. When it decreases in a high region, it can be corrected using a predetermined correction coefficient.

[0007]

As shown in FIG. 4, the flicker flicker luminosity factor an is 0.01 to 30H of the flicker frequency fn.
Although defined as z, the region is narrow between 0.01 and 0.1 Hz, and the coefficient an is as small as about 2.6%.
The n region is ignored here and fn = 0.1 to 30 Hz is assumed. Now, to obtain the flicker fluctuation voltage ΔVn,
First, it is necessary to calculate the voltage effective value Ve, and then apply well-known frequency analysis processing such as fast Fourier transform processing (hereinafter, also simply referred to as FFT processing) to the Ve data string. .

By the way, since fn is set to a range of 0.1 to 30 Hz, if the fundamental wave is 0.1 Hz, it is sufficient to obtain up to the 300th order, and the number N of points of the FFT processing is 2 even if the folding error is taken into consideration. ^{About 11 is} enough. At this time, the sampling interval ΔT has a basic period of 0.1 Hz of 10
Since it is (s), it is given by the following equation (4). ΔT = 10 / N (4)

Assuming that the time interval for calculating Ve coincides with ΔT, the number M of sampling points per cycle required for calculating Ve is the commercial frequency f0, and the following formula (5) is used. Given in. M = 1 / (f0 · ΔT) (5) If N = 1024, M becomes 2.048 points at f0 = 50 Hz, and Ve accuracy cannot be obtained.
In order to obtain the accuracy of Ve, M ≧ 30 is empirically required in consideration of the waveform distortion due to harmonics and the like. Therefore,
In the 50 Hz system, N ≧ 2 ¹⁴ .

On the other hand, the number of multiplications L required for the FFT processing is
It is expressed by the following equation. _{L = (1/2) Nlog 2 N} ... (6) the latter approximately 10 fold in the cases of the (log ₂ N is N of showing the logarithm base 2) N = 2 ¹¹ and N = 2 ¹⁴ Therefore, the calculation amount will increase dramatically.

On the other hand, the calculation of Ve is as shown by the following equation (7):

[Equation 4] Therefore, the number of multiplications becomes M, which is significantly smaller than that in the case of FFT processing. From this, if the number of points N of the FFT processing and the number of sampling points M per cycle required for calculating Ve are made large irrespective of the relationship of the equation (5), the calculation accuracy of Ve does not deteriorate, and The amount of calculation does not increase.

[0012]

1 is a schematic view showing an apparatus to which the present invention is applied, 1 is an analog / digital (A / D) converter, and 2 is
Is a personal computer (also called a personal computer) having a CRT display or the like. By the way, as mentioned above, Ve
In order not to decrease the calculation accuracy of the FFT processing and to increase the calculation amount,
If M for e calculation is arbitrarily set, the time of the Ve column necessary for the FFT processing does not match the time when Ve is calculated, and the data of Ve for FFT processing is linearly interpolated between Ve calculated values. It becomes necessary to create columns, which increases the amount of calculation.

Therefore, in the present invention, the value of M is set so that the time for calculating Ve coincides with the time for Ve for FFT processing. That is, since the Ve calculation sampling time Δt is Δt = 1 / (M · f0) (8) from the above equation (5), a value X obtained by dividing ΔT for FFT by this Δt.
, X = M · f0 (10 / N) (9) Find M that is closest to the integer value between 30 and 45 and adopt it.

In this case, the relationship between Δt and ΔT is approximately represented by the following equation (10). ΔT = KΔt (where K = [X]. [X]: Rounded value of X) (10) By the way, in the case of N = 2048 and f0 = 50 Hz, M
= 41, K = 10.

By the way, when N is not sufficiently large, ΔV
n becomes smaller than the true value as fn becomes higher.
FIG. 2 shows flicker fluctuation voltage characteristics when N = 2048. In addition, gn shown in the figure indicates (ΔVn measured value / ΔVn true value). Here, from the relation of the calculation time,
By using n, ΔVn is corrected as described below to ensure accuracy. New ΔVn = ΔVn measured value / gn (11)

[0016]

According to the present invention, when the FFT process is performed on the voltage effective value Ve to obtain the flicker fluctuation voltage ΔVn, M for Ve calculation is arbitrarily set with respect to the point number N of the FFT process. Therefore, there is an advantage that it is possible to prevent the calculation accuracy of Ve from being lowered without increasing the calculation amount.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an apparatus to which the present invention is applied.

FIG. 2 is a graph showing frequency characteristics of flicker fluctuating voltage.

FIG. 3 is an explanatory diagram for explaining a flicker fluctuation voltage.

FIG. 4 is an explanatory diagram for explaining a flicker visibility coefficient.

[Explanation of symbols]

1 ... Analog / digital (A / D) converter, 2 ... Personal computer (personal computer).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Mr. Naito, No. 1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd.

Claims (3)

[Claims] 1. An A / D converter and a digital processing device are provided, a voltage effective value is sampled from a power system, frequency analysis processing is performed on this, and a flicker fluctuating voltage ΔVn is obtained. In a digital flicker meter that measures a flicker management index ΔV10 represented by the following equation (1) using a coefficient an, the sampling time of the voltage effective value and the sampling time when performing frequency analysis processing on the flicker fluctuation voltage ΔVn are mutually A digital flicker meter characterized by being different. [Equation 1] 2. On the sampling point of the voltage effective value,
2. The digital flicker meter according to claim 1, wherein sampling points when frequency-analyzing the flicker fluctuating voltage ΔVn are overlapped with each other. 3. The digital flicker meter according to claim 1, wherein when the effective voltage value decreases in a region where the flicker frequency is high, it is corrected using a predetermined correction coefficient.