CN107085133A - Method and device for calculating single-phase virtual value - Google Patents
Method and device for calculating single-phase virtual value Download PDFInfo
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- CN107085133A CN107085133A CN201610085497.0A CN201610085497A CN107085133A CN 107085133 A CN107085133 A CN 107085133A CN 201610085497 A CN201610085497 A CN 201610085497A CN 107085133 A CN107085133 A CN 107085133A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/02—Measuring effective values, i.e. root-mean-square values
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Abstract
The invention discloses a kind of method and device for being used to calculate single-phase virtual value, this method includes：Signal acquisition step, gathers AC signal；Absolute value shift step, absolute value conversion is carried out by the AC signal of collection；DC component extraction step, the AC signal after absolute value is converted carries out first and converted, and extracts DC component therein；Transformation of scale step, DC component is carried out transformation of scale to obtain the single-phase virtual value of AC signal.The present invention can improve the arithmetic speed and precision of the single-phase virtual value of AC signal.
Description
Technical Field
The invention relates to the technical field of electric power, in particular to a method and a device for calculating a single-phase effective value.
Background
The effective value (RMS) represents the amplitude of the alternating current signal, is one of the measurement indexes of the thermal effect of the load object, has important instructive significance for the protection of the system and the judgment of the actual operation condition, and has strong practical significance. The effective value is specifically defined as: the alternating current and the direct current are respectively passed through the resistors with the same resistance value, and if the heat generated by the resistors in the same time is equal, the direct current value is called as the effective value of the alternating current.
The hardware protection threshold value of the high-power current conversion system is set according to an alternating current instantaneous value, and the software protection is based on an effective value, particularly a single-phase effective value in three-phase intersection flow needs to be calculated aiming at three-phase unbalance and open-phase protection. The accuracy of the effective value therefore determines the accuracy of the protection system. If the effective value has a large error, the system protection can be disabled, and the machine can be damaged and the people can be killed seriously.
In the conventional method for calculating an effective value, the calculation of a single-phase effective value and the calculation of a single-phase effective value under a variable frequency are methods for obtaining a root mean square by taking multiple points, and certain limitations and complexity exist. The method has higher requirements on the number and the period of the point taking, occupies a large amount of storage space and consumes time for calculation, and simultaneously causes inaccurate calculation when the frequency changes.
Disclosure of Invention
In order to solve the above problems, the present invention provides a method and an apparatus for calculating a single-phase effective value, so as to improve the operation speed and accuracy of the single-phase effective value of an ac signal.
According to an aspect of the present invention, there is provided a method for calculating a single-phase effective value, including:
a signal acquisition step of acquiring an alternating current signal;
an absolute value conversion step of performing absolute value conversion on the acquired alternating current signal;
a direct current component extraction step, wherein the alternating current signal after absolute value conversion is subjected to first conversion, and a direct current component in the alternating current signal is extracted;
and a scaling step of scaling the direct current component to obtain a single-phase effective value of the alternating current signal.
According to one embodiment of the invention, the first transform comprises a fourier transform.
According to one embodiment of the invention, the scaling step uses scaling factors of
According to one embodiment of the invention, the alternating current signal is a voltage signal.
According to one embodiment of the invention, the alternating current signal is a current signal.
According to another aspect of the present invention, there is also provided an apparatus for calculating a single-phase effective value, including:
the acquisition module is used for acquiring alternating current signals;
the absolute value conversion module is used for carrying out absolute value conversion on the acquired alternating current signals;
the direct current component extraction module is used for carrying out first conversion on the alternating current signal after the absolute value conversion and extracting a direct current component in the alternating current signal;
and the proportion conversion module is used for carrying out proportion conversion on the direct-current component so as to obtain a single-phase effective value of the alternating-current signal.
According to an embodiment of the invention, the first transform employed by the direct current component extraction module comprises a fourier transform.
According to one embodiment of the present invention, the scaling module uses scaling factors of
According to one embodiment of the invention, the alternating current signal collected by the collection module is a voltage signal.
According to one embodiment of the invention, the alternating current signal collected by the collection module is a current signal.
The invention has the beneficial effects that:
the invention sets three operation links of absolute value transformation, Fourier transformation and proportion operation in sequence, only needs to complete addition and multiplication operation in the process of calculating the effective value of the alternating current signal, and does not have evolution operation which usually needs to consume a large number of clock cycles, thereby greatly improving the operation speed of the method. In addition, the interface of the invention is simple, the periodic equal sampling processing is not needed, the connection between the software and the sampling can be separated, and a large amount of storage space can not be occupied. Meanwhile, the invention adopts a frequency domain analysis method to convert the time domain signal into the frequency domain signal for processing, thereby avoiding the interference of frequency transformation on the sampling signal and improving the operation precision.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required in the description of the embodiments or the prior art:
FIG. 1 is a flow diagram of a method according to one embodiment of the invention;
FIG. 2a is a schematic representation of an AC signal before absolute value transformation according to one embodiment of the present invention;
FIG. 2b is a schematic diagram of an AC signal after absolute value transformation according to one embodiment of the present invention; and
fig. 3 is a diagram of a device structure according to an embodiment of the present invention.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.
In the conventional method for calculating an ac effective value, there are certain limitations and complexities in the calculation of a single-phase effective value and the calculation of a single-phase effective value under a varying frequency by taking a multi-point root mean square. The method has higher requirements on the number and the period of the point taking, occupies a large amount of storage space and consumes time for calculation, and simultaneously, the calculation is inaccurate when the frequency changes.
Therefore, the present invention provides a method for calculating a single-phase effective value, which is illustrated in fig. 1 as a flowchart of the method according to an embodiment of the present invention, and the present invention is described in detail below with reference to fig. 1.
First, step S110 is a signal collection step, i.e., collecting ac signals. Specifically, in this step, the collected ac signal may be a voltage signal or a current signal. An ac signal is a signal in which the direction of current flow changes, and can be represented by a sinusoidal function as follows:
x(t)＝Amsinωt (1)
wherein A ismRepresents the maximum amplitude of the ac signal, ω represents the angular frequency of the ac signal, and t represents time.
And setting a sampling frequency, and sampling the original analog alternating current signal to obtain a discrete digital alternating current signal.
Next, step S120 is an absolute value transformation step, i.e. absolute value transformation is performed on the acquired ac signal. Specifically, in this step, the ac signal represented by the formula (1) is converted into:
y(t)＝Am|sinωt| (2)
that is, the sampled negative value signal is converted into a positive value signal, the original sampled positive value signal is not changed, and the specific signal conversion is shown in fig. 2a (before absolute value conversion) and fig. 2b (after absolute value conversion).
Next, in step S130, an absolute value conversion step of performing a first conversion on the ac signal after the absolute value conversion, and extracting a dc component therein. Specifically, in this step, the ac signal after the absolute value conversion is converted into a constant dc signal by using a constant conversion method.
In one embodiment of the invention, the transform method is a fourier transform. Fourier transform is a method of analyzing a signal, which analyzes components of the signal, and also synthesizes a signal using these components, and uses a sine wave as a component of the signal. Therefore, an alternating current signal represented by a sine function can be analyzed by fourier transform.
The ac signal after absolute value transformation, i.e. fourier series f (t) obtained by fourier transformation of equation (2), is:
wherein,is the dc component of the ac signal.
Due to the fact that the effective value of the alternating current signal is between the maximum value of the amplitude of the alternating current signalThe relationship of the multiple, namely: effective valueTherefore, the effective value of the alternating current signal can be calculated based on the direct current component.
Finally, in step S140, a scaling step, i.e. scaling the dc component to obtain a single-phase effective value of the ac signal, is performed.
Specifically, in this step, a proportional element is added to process the dc component obtained in step S130, so as to obtain a single-phase effective value of the ac signal. The direct current component obtained by Fourier transform isThen, the DC component is multiplied by a scaling factorThat is, the effective value of the AC signal can be obtained
From the above analysis, in the process of calculating the effective value of the alternating current signal, the invention only needs to complete addition and multiplication operations, but does not have evolution operations which usually need to consume a large number of clock cycles, thereby greatly improving the operation speed of the method. In addition, the interface of the invention is simple, the periodic equal sampling processing is not needed, the connection between the software and the sampling can be separated, and a large amount of storage space can not be occupied. Meanwhile, the invention adopts a frequency domain analysis method to convert the time domain signal into the frequency domain signal for processing, thereby avoiding the interference of frequency transformation on the sampling signal and improving the operation precision.
In the invention, when the first transformation adopts Fourier transformation to obtain direct current component, the corresponding proportionality coefficient isWhen the first transformation adopts other transformation methods to obtain the direct current component, the corresponding proportionality coefficient needs to be adjusted correspondingly.
According to another aspect of the invention, an apparatus for calculating a single-phase effective value is also provided. Fig. 3 is a schematic structural diagram of an apparatus according to an embodiment of the present invention, and the present invention will be described in detail with reference to fig. 3.
As shown in fig. 3, the apparatus for calculating a single-phase effective value includes an acquisition module, an absolute value transformation module, a dc component extraction module, and a scaling module.
The acquisition module is used for acquiring alternating current signals; the absolute value conversion module carries out absolute value conversion on the acquired alternating current signal; the direct current component extraction module carries out first conversion on the alternating current signal after the absolute value conversion and extracts a direct current component in the alternating current signal; the proportion conversion module is used for carrying out proportion conversion on the direct current component so as to obtain a single-phase effective value of the alternating current signal.
The alternating current signal collected by the collection module can be a voltage signal or a current signal. The alternating current signal is a signal in which the direction of current changes, and may be represented by a sine function of equation (1).
In one embodiment of the invention, the first transform employed by the dc component extraction module comprises a fourier transform. Fourier transform is a method of analyzing a signal, which analyzes components of the signal, and also synthesizes a signal using these components, and uses a sine wave as a component of the signal. Therefore, an alternating current signal represented by a sine function can be analyzed by fourier transform. The ac signal after absolute value transformation, i.e. the fourier series f (t) obtained by fourier transformation of equation (2), i.e. equation (3).
Due to the fact that the effective value of the alternating current signal is between the maximum value of the amplitude of the alternating current signalThe relationship of the multiple, namely: effective valueTherefore, the effective value of the alternating current signal can be calculated based on the direct current component.
In one embodiment of the invention, the scaling module uses scaling factors ofAnd (4) processing the direct current component in the formula (3) to obtain the single-phase effective value of the alternating current signal. The direct current component obtained by Fourier transform isThen, the DC component is multiplied by a scaling factorThat is, the effective value of the AC signal can be obtained
When the first transformation in the direct current component extraction module adopts other transformation methods to obtain the direct current component, the scale coefficient in the scale transformation module needs to be correspondingly adjusted.
Although the embodiments of the present invention have been described above, the above description is only for the convenience of understanding the present invention, and is not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A method for computing a single-phase effective value, comprising:
a signal acquisition step of acquiring an alternating current signal;
an absolute value conversion step of performing absolute value conversion on the acquired alternating current signal;
a direct current component extraction step, wherein the alternating current signal after absolute value conversion is subjected to first conversion, and a direct current component in the alternating current signal is extracted;
and a scaling step of scaling the direct current component to obtain a single-phase effective value of the alternating current signal.
2. The method of claim 1, wherein the first transform comprises a fourier transform.
3. The method of claim 2, wherein the scaling step uses scaling factors of
4. The method of claim 1, wherein the ac signal is a voltage signal.
5. The method of claim 1, wherein the alternating current signal is a current signal.
6. An apparatus for calculating a single-phase effective value, comprising:
the acquisition module is used for acquiring alternating current signals;
the absolute value conversion module is used for carrying out absolute value conversion on the acquired alternating current signals;
the direct current component extraction module is used for carrying out first conversion on the alternating current signal after the absolute value conversion and extracting a direct current component in the alternating current signal;
and the proportion conversion module is used for carrying out proportion conversion on the direct-current component so as to obtain a single-phase effective value of the alternating-current signal.
7. The apparatus of claim 6, wherein the first transform employed by the direct current component extraction module comprises a Fourier transform.
8. The apparatus of claim 7, wherein the scaling module employs scaling coefficients of
9. The apparatus of claim 6, wherein the AC signal collected by the collection module is a voltage signal.
10. The apparatus of claim 6, wherein the alternating current signal collected by the collection module is a current signal.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113740592A (en) * | 2021-09-13 | 2021-12-03 | 温州大学 | Periodic signal effective value optimal measurement circuit |
| CN113740594A (en) * | 2021-09-10 | 2021-12-03 | 温州大学 | Alternating voltage effective value high accuracy measurement circuit |
| CN113740591A (en) * | 2021-09-10 | 2021-12-03 | 温州大学 | Periodic signal effective value optimal estimation method |
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| CN102565524A (en) * | 2012-03-15 | 2012-07-11 | 江苏省电力公司常州供电公司 | Real-time monitoring method for short-circuit current of near zone of transformer |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113740594A (en) * | 2021-09-10 | 2021-12-03 | 温州大学 | Alternating voltage effective value high accuracy measurement circuit |
| CN113740591A (en) * | 2021-09-10 | 2021-12-03 | 温州大学 | Periodic signal effective value optimal estimation method |
| CN113740591B (en) * | 2021-09-10 | 2023-10-13 | 温州大学 | An optimal estimation method for the effective value of periodic signals |
| CN113740594B (en) * | 2021-09-10 | 2023-10-17 | 温州大学 | A high-precision measurement circuit for the effective value of AC voltage |
| CN113740592A (en) * | 2021-09-13 | 2021-12-03 | 温州大学 | Periodic signal effective value optimal measurement circuit |
| CN113740592B (en) * | 2021-09-13 | 2023-10-13 | 温州大学 | Optimal measurement circuit for effective value of periodic signal |
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Application publication date: 20170822 |