JP3417536B2 - Harmonic signal processor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-accuracy harmonic signal processing device having a small gain error.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram of a conventional example which has been generally used in the past, and is a block diagram for obtaining a distortion factor, for example, Japanese Patent Laid-Open No. 8-201444, entitled "Harmonic Signal Processing Device". ], As shown in FIG.

In the figure, A is a distribution line of a commercial frequency AC power supply whose harmonics are measured. PT is a power transformer that takes out voltage from the distribution line A. CT is a current transformer that takes out current from the distribution line A.

Reference numeral 1 is an A / D converter for converting the voltage from the power transformer PT or the current from the current transformer CT from an analog value to a digital value. 2 is A /
It is a bandpass filter for fundamental wave extraction which extracts the fundamental wave component contained in the voltage or current converted by the D converter 1.

Reference numeral 3 is a high-pass filter for removing the fundamental wave from the voltage or current converted by the A / D converter 1 for removing the fundamental wave component. Reference numeral 4 denotes an effective value calculating means for calculating an effective value of the fundamental wave component extracted by the fundamental wave extracting bandpass filter 2.

Reference numeral 5 is an effective value calculating means for calculating the effective value of the harmonic component excluding the fundamental wave component that has passed through the fundamental wave removing high-pass filter 3. Reference numeral 6 is a dividing means for calculating the distortion rate by dividing the effective value calculated by the effective value calculating means 5 by the effective value calculated by the effective value calculating means 4. That is, the distortion is the percentage of the value obtained by dividing the effective value of the harmonic by the effective value of the fundamental wave.

FIG. 8 is a block diagram of a conventional example that has been generally used in the past, and is a block diagram for obtaining the total distortion rate. For example, Japanese Patent Application Laid-Open No. 8-201444, entitled "Harmonic Signal Processing Device" , Shown in FIG.

In the figure, A is a distribution line of a commercial frequency AC power supply whose harmonics are measured. PT is a power transformer that takes out voltage from the distribution line A. CT is a current transformer that takes out current from the distribution line A.

Reference numeral 1 is an A / D converter for converting a voltage from the power transformer PT or a current from the current transformer CT from an analog value to a digital value. 11 is A
It is a high-pass filter for removing a DC component that removes the DC component contained in the voltage or current converted by the / D converter 1 and extracts all harmonic components.

Reference numeral 12 is a high-pass filter for removing the fundamental wave from the voltage or current converted by the A / D converter 1 to remove the fundamental wave component. Reference numeral 13 is an effective value calculation means for calculating the effective values of the fundamental wave and all harmonic components that have passed through the DC component removing high-pass filter 11.

Reference numeral 14 is a high-pass filter 1 for removing the fundamental wave.
It is an effective value calculation means for calculating the effective value of the harmonic component excluding the fundamental wave component that has passed through 2. Reference numeral 15 denotes a dividing unit that divides the effective value calculated by the effective value calculating unit 14 by the effective value calculated by the effective value calculating unit 13 to calculate the total distortion rate. That is, the distortion factor is the percentage of the value obtained by dividing the effective value of the harmonic by the effective value of the fundamental wave and the harmonic.

[0012]

However, in such a device, when a voltage or a current is passed through the A / D converter, the gain may be increased with respect to the frequency of the input signal depending on the type of the A / D converter. Changes.

For example, the ΣΔ A / D converter has a frequency characteristic of the moving average filter because it is converted into a digital signal of several bits by the moving average filter. When the effective value calculation is performed on one frequency component, a correct calculation can be performed by applying a constant for correcting the gain error.

However, when a plurality of frequency components are simultaneously calculated as an effective value, such as an effective value of a harmonic wave and an effective value of a fundamental wave and a harmonic wave, only the gain error of each frequency component is converted into an effective value. There will be an error.

The present invention solves this problem. An object of the present invention is to provide a highly accurate harmonic signal processing device with a small gain error.

[0016]

In order to achieve this object, the present invention provides (1) a digital voltage or current of an analog signal which is connected to a distribution line supplying power from a power source and supplied from the distribution line. A / D converter for converting to a signal and this A / D
A high-pass filter for removing a fundamental wave through which the voltage or current converted by the converter passes, a predetermined filter through which the voltage or current converted by the A / D converter passes, and a measurement signal passing through the high-pass filter for removing a fundamental wave From the signals of the two effective value calculating means, the first effective value calculating means for calculating the effective value of the second effective value calculating means, the second effective value calculating means for calculating the effective value of the measurement signal passing through the predetermined filter, respectively. A harmonic signal processing device, comprising: a dividing unit for calculating a distortion factor, which is provided between the A / D converter and the filter and is adapted to a frequency generated by the A / D converter.
A harmonic signal processing device comprising a gain correction filter for correcting the gain error . (2) The harmonic signal processing device according to (1) , wherein a bandpass filter for extracting a fundamental wave is used as the predetermined filter. (3) The harmonic signal processing device according to (1) , wherein the predetermined filter is a high-pass filter for removing a DC component. Is configured.

[0017]

In the above configuration, in the invention of (1), the voltage or current of the analog signal generated by the power supply is converted into a digital signal, and the gain frequency characteristic is corrected by the gain correction filter.

This digital signal passes through a high-pass filter for removing the fundamental wave and a predetermined filter, respectively. The effective values of the measurement signals that have passed through the high-pass filter for removing the fundamental wave and the predetermined filter are calculated by the first and second effective value calculating means, and the distortion rate is calculated by the dividing means from these two effective values. .

In the invention of (2), the fundamental wave component is extracted and the effective value is obtained. In addition, the harmonic component excluding the fundamental wave component is extracted and the effective value is obtained. Then, the distortion factor is obtained by dividing the latter effective value by the former effective value.

In the invention of (3), the direct current component is removed to extract the fundamental wave component and the harmonic component, and the effective value is obtained. In addition, the harmonic component excluding the fundamental wave component is extracted and the effective value is obtained. Then, the latter effective value is divided by the former effective value to obtain the total distortion rate. Hereinafter, detailed description will be given based on examples.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram for obtaining a distortion rate, which is an explanatory view of the essential parts of an embodiment of the present invention. In the figure, the same symbols as those in FIG. 7 represent the same functions. Only parts different from FIG. 7 will be described below.

In the figure, 21 is an A / D converter 1,
It is a gain correction filter provided between the fundamental wave extracting band pass filter 2 and the fundamental wave removing high pass filter 3.

FIG. 2 is an explanatory view of the essential parts of another embodiment of the present invention, which is a block diagram for obtaining the total distortion rate. In the figure,
The same symbols as those in FIG. 8 represent the same functions. Below, FIG.
Only the differences will be explained.

In the figure, 31 is the A / D converter 1,
It is a gain correction filter provided between the DC component removing high-pass filter 11 and the fundamental wave removing high-pass filter 12.

In the above structure, the gain correction filters 21 and 31 correct the gain error with respect to the frequency generated by the A / D converter 1. Gain correction filter 2
1 and 31 filter the discrete (discrete value) signal.

That is, since it is a digital filter, it can be generally expressed by the equation (1). However, assuming that the coefficients that determine the characteristics of the filter are An and Bn and the input and output values before n sampling periods are Xn and Yn, the output value Y0 of the current sampling period of the digital band pass filter is expressed by the equation (1). . In the equation (1), the degree N and An, Bn (n: 0 to N)
The gain correction filter 2 by properly setting
1, 31 can be configured.

Specifically, an example of the gain correction filters 21 and 31 when N = 2 is shown. The A / D converter uses a second-order moving average filter in the ΣΔ method. The frequency characteristic of the gain of the second-order moving average filter is as shown in FIG.

The coefficients of the gain correction filters 21 and 31 designed for the secondary moving average filter are as follows. A0 = 1.2946923 A1 = 1.3183402 B1 = 1.3183402 A2 = 0.0646722 B2 = 0.3593645

The frequency characteristics of the gain correction filters 21 and 31 are shown in FIG. Results through a gain correction filter 21 and 31, until 1140H _Z of 19-order component of 60H _Z, the gain error is within 0.5 percent up to 40 percent. FIG. 5 shows the frequency characteristic after gain correction, and FIG. 6 shows the gain error after gain correction.

3 to 6, fnk represents the Nyquist frequency, in this case 1465H _Z , and fs represents the sampling frequency, in this case 2930H _Z.

As a result, since the gain correction filters 21 and 31 for correcting the gain error with respect to the frequency generated by the A / D converter 1 are provided, the total distortion rate by the FFT calculation (high-speed Fourier transform) using an expensive system. , Comparing with the measurement of the distortion factor, the calculation of the digital filter method, which is cheaper, enables the highly accurate measurement within 0.5% of the gain error for the practically sufficient frequency band (fundamental wave to 19th order). It is possible to obtain a high-accuracy harmonic signal processing device that has a small gain error.

[0032]

As described in detail above, according to the first aspect of the present invention, the gain correction filter for correcting the gain error with respect to the frequency generated by the A / D converter is provided.

Therefore, in comparison with the measurement of the total distortion and the distortion by the FFT operation (high-speed Fourier transform) using an expensive system, the operation of the digital filter method, which is inexpensive, can be used in a frequency band (fundamental wave) practically sufficient. The gain error is small for up to 19th order), and a harmonic signal processing device capable of performing highly accurate measurement can be obtained.

According to the second aspect of the present invention, the distortion factor of the harmonic can be measured by an inexpensive and simple circuit without using an expensive system for performing the FFT operation.

According to the third aspect of the present invention, the total distortion of harmonics can be measured by an inexpensive and simple circuit without using an expensive system for performing FFT calculation.

Therefore, according to the present invention, it is possible to realize a highly accurate harmonic signal processing device with a small gain error.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of FIGS. 1 and 2;

FIG. 4 is an operation explanatory diagram of FIGS. 1 and 2;

5 is an operation explanatory diagram of FIGS. 1 and 2. FIG.

FIG. 6 is an operation explanatory diagram of FIGS. 1 and 2;

FIG. 7 is an explanatory diagram of a configuration of a conventional example that is generally used in the past.

FIG. 8 is a structural explanatory view of another conventional example that is generally used in the past.

[Explanation of symbols]

A distribution line. PT power transformer CT current transformer 1 A / D converter 2 Bandpass filter for fundamental wave extraction 3 High-pass filter for fundamental wave removal 4 Effective value calculation means 5 Effective value calculation means 6 division means 11 High-pass filter for DC component removal 12 High-pass filter for fundamental wave removal 13 Effective value calculation means 14 Effective value calculation means 15 Division means 21 Gain correction filter 31 Gain correction filter

Claims (3)

(57) [Claims] 1. An A / D converter that is connected to a distribution line that supplies power from a power source and that converts the voltage or current of an analog signal supplied from the distribution line into a digital signal, and the A / D converter A high-pass filter for removing a fundamental wave through which the voltage or current passes, a predetermined filter through which the voltage or current converted by the A / D converter passes, and an effective value of the measurement signal passed through the high-pass filter for removing a fundamental wave. A first effective value calculating means for calculating, a second effective value calculating means for calculating an effective value of the measurement signal that has passed through the predetermined filter, and a distortion rate from the signals of the two effective value calculating means. in harmonic signal processing apparatus comprising a dividing means for, provided between said a / D converter filter the
Gain error with respect to frequency generated by A / D converter
A harmonic signal processing device comprising a gain correction filter for correcting 2. The harmonic signal processing device according to claim 1 , wherein a bandpass filter for extracting a fundamental wave is used as the predetermined filter. 3. The harmonic signal processing device according to claim 1 , wherein a high-pass filter for removing a DC component is used as the predetermined filter.