CN115825556A - Method and device for calculating power frequency - Google Patents
Method and device for calculating power frequency Download PDFInfo
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- CN115825556A CN115825556A CN202211661091.4A CN202211661091A CN115825556A CN 115825556 A CN115825556 A CN 115825556A CN 202211661091 A CN202211661091 A CN 202211661091A CN 115825556 A CN115825556 A CN 115825556A
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Abstract
The invention provides a method and a device for calculating power frequency, wherein the method comprises the following steps: inputting a sine wave signal, wherein the sine wave signal is a three-phase alternating current voltage or a three-phase alternating current signal; sampling the input sine wave signal at a sampling frequency f Mining Is 2^ n times of 50Hz, and n is an integer more than 1; storing sampling values corresponding to 2^ (n + 1) continuous sampling points into an array; and carrying out linearization processing on the sampling points meeting the preset conditions in the array, and calculating the actual power frequency according to the linearization processing result. The method solves the problems of large error and inaccuracy in power frequency calculation of the existing method, can basically eliminate errors, and can more accurately measure the actual power frequency subjected to external interference.
Description
Technical Field
The invention belongs to the field of electrical engineering, and particularly relates to a method and a device for calculating power frequency.
Background
As is well known, the use of energy in China as a large population country is particularly huge on the scale of power consumption. With the development of economic technology, photovoltaic power generation gradually takes a leading position. The electric energy of photovoltaic power generation is processed by a transformer and an inverter and then transmitted to each household according to the power frequency specified by the state in a factory. The power generation, transmission, transformation, distribution and the like of the power system transmit electric energy according to the power frequency. In the long-distance power transmission process, frequency instability is inevitably caused by the influence of various environmental factors such as a magnetic field, and how to accurately obtain the actual frequency of the power transmitted by the power system is extremely important whether the actual frequency is within the specified range of the power industry department.
Disclosure of Invention
The embodiment of the application provides a method and a device for calculating power frequency, solves the problems of large error and inaccuracy in power frequency calculation of the existing method, can basically eliminate errors, and can more accurately measure the actual power frequency subjected to external interference.
In a first aspect, an embodiment of the present application provides a method for calculating a power frequency, including:
inputting a sine wave signal, wherein the sine wave signal is a three-phase alternating current voltage or a three-phase alternating current signal;
sampling the input sine wave signal at a sampling frequency f Mining Is 2^ n times of 50Hz, and n is an integer more than 1;
storing sampling values corresponding to 2^ (n + 1) continuous sampling points into an array;
and carrying out linearization processing on the sampling points meeting the preset conditions in the array, and calculating the actual power frequency according to the linearization processing result.
The method comprises the following steps of carrying out linear processing on sampling points meeting preset conditions in the array, and calculating actual power frequency according to linear processing results, wherein the method comprises the following steps:
and carrying out linearization processing on the sampling points intersected with the time axis or two adjacent sampling points nearest to the time axis in the array, and calculating the actual power frequency according to the linearization processing result.
The sampling points meeting the preset conditions in the array are subjected to linearization processing, and the actual power frequency is calculated according to the linearization processing result, wherein the method comprises the following steps:
traversing an arrayThe sampling points taken out comprise x1 and x2, the corresponding sampling values are y1 and y2, x1 is more than x2, x1 and x2 are adjacent sampling points, y1 is less than or equal to 0, y2 is more than or equal to 0, or y1 is more than or equal to 0, and y2 is less than or equal to 0; the taken sampling points also comprise x3 and x4, the corresponding sampling values are y3 and y4, x3 is more than x4, x3 and x4 are adjacent sampling points, y3 is more than or equal to 0, y4 is less than or equal to 0, or y3 is less than or equal to 0, and y4 is more than or equal to 0; the sampling points x1 and x2 differ by 1/f Mining X3 and x4 differ by 1/f Mining Calculating the actual power frequency by using the following formula:
wherein f is Mining ＝50×2^n Hz，n＝2,3,4……。
Where n =8, x1 and x2 differ by 78.125us, and x3 and x4 differ by 78.125us.
Where sample points x1 and x3 are separated by a zero crossing.
In a second aspect, the present application provides an apparatus for calculating power frequency, comprising:
the input unit is used for inputting sine wave signals, and the sine wave signals are three-phase alternating-current voltages or three-phase alternating-current signals;
the sampling unit is used for sampling an input sine wave signal, the sampling frequency f is 2^ n times of 50Hz, and n is an integer greater than 1;
the storage unit is used for storing sampling values corresponding to 2^ (n + 1) continuous sampling points into an array;
and the calculation unit is used for carrying out linearization processing on the sampling points meeting the preset conditions in the array and calculating the actual power frequency according to the linearization processing result.
Wherein the calculation unit is configured to: and carrying out linearization processing on the sampling points intersected with the time axis or two adjacent sampling points nearest to the time axis in the array, and calculating the actual power frequency according to the linearization processing result.
Wherein the computing unit is configured to:
traversing the array, taking out sampling points including x1 and x2, and correspondingly samplingThe sample values are y1 and y2, x1 is more than x2, x1 and x2 are adjacent sampling points, y1 is less than or equal to 0, y2 is more than or equal to 0, or y1 is more than or equal to 0, and y2 is less than or equal to 0; the taken sampling points also comprise x3 and x4, the corresponding sampling values are y3 and y4, x3 is more than x4, x3 and x4 are adjacent sampling points, y3 is more than or equal to 0, y4 is less than or equal to 0, or y3 is less than or equal to 0, and y4 is more than or equal to 0; the sampling points x1 and x2 differ by 1/f Mining X3 and x4 differ by 1/f Mining Calculating the actual power frequency by using the following equation:
wherein f is Mining ＝50×2^n Hz，n＝2,3,4……。
In a third aspect, the present application provides a computer-readable storage medium, on which a computer program is stored, and the computer program is used for implementing the steps of any one of the above methods when executed by a processor.
In a fourth aspect, the present application provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, where the processor implements the steps of any one of the above methods when executing the program.
The method and the device for calculating the power frequency have the following beneficial effects:
the method solves the problems that the power frequency calculated by the existing method is large in error and inaccurate, can basically eliminate errors, and can more accurately measure the actual power frequency after being interfered by the outside world.
Drawings
FIG. 1 is a schematic flow chart of a method for calculating power frequency according to an embodiment of the present application;
fig. 2 is another schematic flow chart of a method for calculating power frequency in the embodiment of the present application;
FIG. 3 is a schematic diagram of a sine wave signal in an embodiment of the present application;
FIG. 4 is a schematic diagram illustrating a sampling point is subjected to linearization processing to calculate an actual power frequency in the embodiment of the present application;
fig. 5 is a schematic structural diagram of a device for calculating power frequency according to an embodiment of the present application.
Detailed Description
The present application is further described with reference to the following figures and examples.
The following description provides embodiments of the invention, which may be combined or substituted for various embodiments, and this application is therefore intended to cover all possible combinations of the same and/or different embodiments described. Thus, if one embodiment includes features a, B, C and another embodiment includes features B, D, then this application should also be construed to include embodiments that include all other possible combinations of one or more of a, B, C, D, although such embodiments may not be explicitly recited in the following text.
No matter three-phase alternating voltage or three-phase alternating current exists in the power system, the most basic waveform is a sine wave waveform, so that the accuracy of measuring the actual frequency after the interference of the outside on the power frequency is easier to improve by analyzing the sine wave waveform. In the existing power frequency calculation, software finds two zero-crossing points in one period and calculates an intermediate time period, power frequency precision is often influenced by the number of sampling points and sampling interval time, single calculation error range is large, and multi-period averaging is performed, so that sensitivity is limited. Therefore, the method is based on the traditional calculation method, the zero crossing point data are subjected to linear processing, and the relatively accurate zero crossing point position is obtained, so that the purpose of accurately calculating the power frequency in real time is achieved.
As shown in fig. 1, the method for calculating power frequency of the present application includes: s101, inputting a sine wave signal, wherein the sine wave signal is a three-phase alternating current voltage or a three-phase alternating current signal; s103, sampling the input sine wave signal with a sampling frequency f Mining Is 2^ n times of 50Hz, and n is an integer more than 1; s105, storing sampling values corresponding to 2^ n continuous sampling points into an array; and S107, carrying out linearization processing on the sampling points meeting the preset conditions in the array, and calculating the actual power frequency according to the linearization processing result.
As shown in fig. 1-4, the algorithm principle implemented by the solution of the present invention is illustrated:
in normal single chip microcomputer and DSP chip programs, because of power frequency, the value is about 50Hz, according to the Nyquist theorem: during the conversion of analog/digital signals, when the sampling frequency f Mining Greater than the highest frequency f in the signal max Twice (f) Mining ＞2f max ) The digital signal after sampling completely retains the information in the original signal, so the sampling frequency f in the chip is normal Mining Is 2 < Lambda > n times 50Hz, i.e. 2 < Lambda > n points are sampled in one period, wherein n is larger than 1. Here we assume that n takes 8, then 256 points can be sampled, i.e. every 1/f Mining (78.125 us) a sample is taken and an array of size 512 is initialized in the algorithm program for recording the sample value. Secondly, according to the power supply regulation of the ministry of electric power industry in China, the installed capacity of a power grid is 300 thousands KW or more, the allowable error of the power supply frequency is +/-0.2 Hz, namely the frequency resolution of adjacent sampling points is below 0.2Hz, and the actual power frequency fluctuation can be accurately measured. When the frequency fluctuation causes more sampling or less sampling of one point, the measured frequencies are 49.6124Hz and 50.3937Hz, which obviously exceeds the allowable error.
The invention is developed aiming at the linearization processing of sine wave waveform sampling values. Firstly, sampling is carried out on an input sine wave signal, and sampling values corresponding to 2^ n sampling points are stored in an array, wherein n =8 is taken as an example. Then, the sampling point intersecting the time axis, i.e. the zero point, or two adjacent sampling points not intersecting the time axis are taken out. The log array is traversed by a for loop, where the sample points to be extracted are assumed to be x1, x2, and the corresponding sample values are y1, y2. According to the condition that x1 is less than x2, x1 and x2 are adjacent sampling points, and the condition that y1 is less than or equal to 0, y2 is greater than or equal to 0 or y1 is greater than or equal to 0, and y2 is less than or equal to 0 is met, the sampling points x1 and x2 are points to be taken out. Similarly, sampling points x3 and x4 may be set correspondingly, and the corresponding sampling values are y3 and y4. And according to the condition that x3 is less than x4, x3 and x4 are adjacent sampling points, and the condition that y3 is more than or equal to 0, y4 is less than or equal to 0 or y3 is less than or equal to 0 and y4 is more than or equal to 0 is met, the sampling points x3 and x4 can be taken out. Here x1 and x2 differ by 78.125us and x3 and x4 differ by 78.125us. In the present application, as shown in fig. 3, a zero-crossing point is spaced between sampling points x1 and x3, and the zero-crossing point is an intersection point of a sine wave and an x-axis. In the linearization process in the present application, assuming that the slope of the line segment between the two points x1 and x2 is constant, the slope of the line segment between the two points x3 and x4 is constant, the area between x1 and the zero point is removed according to the ratio of y1 to y2, and the area between x4 and the zero point is removed according to the ratio of y3 to y4, leaving only the middle part of the waveform. Calculating the actual power frequency by using the following formula:
note: wherein f is Mining ＝50×2^n Hz(n＝2,3,4...)。
As shown in FIGS. 3-4, x1 and x2 differ by 1/f Mining X3 and x4 differ by 1/f Mining When n =8, x1 and x2 differ by 78.125us, and x3 and x4 differ by 78.125us. According to the similar triangle theorem:
the time T = (x 4-x 1)/f represented by L5 is calculated Mining And L1-L4, obtaining the frequency by calculating the reciprocal of the time T, and finally obtaining a calculation formula of the actual power frequency:
the traditional sampling method comprises the steps of sampling 2^ n points or sampling 2^ (n-1) points, directly subtracting sampling points at the head and the tail, multiplying the sampling points by interval time to calculate the time of one period or half period difference, and finally obtaining the power frequency by obtaining the reciprocal or obtaining the reciprocal after multiplying by 2. Taking n =8 as an example, the calculation shows that when the frequency fluctuates, the resolution error of the traditional method to the frequency is approximately 0.3937Hz, which is not in accordance with the power supply regulation of the power industry department and has a large difference with the actual power frequency.
The algorithm for improving the precision of the calculated power frequency provided by the invention can basically eliminate the error of the frequency measurement of the traditional method after the linearization processing is carried out between two adjacent sampling points which are intersected with the time axis or are closest to the time axis after sampling, and obtain more accurate actual power frequency on the basis of not increasing the time complexity and the space complexity of the original program.
In the application, firstly, a sine wave signal is input, and the sine wave signal is sampled and valued. Ideally, 2^ (n + 1) samples need to be sampled continuously for one cycle. Now, whether the period is one period in an ideal state or not, only 2^ (n + 1) continuous sampling points are taken and stored in an array for analysis and processing.
Then, traversing the array by using the for-loop condition statement, and taking out four sampling points meeting the following conditions and corresponding sampling values.
(1) x1 is adjacent to x2, x1 is less than x2, y1 is less than or equal to 0, y2 is greater than or equal to 0 or y1 is greater than or equal to 0, and y2 is less than or equal to 0, then x1, x2, y1 and y2 are taken out.
(2) x3 is adjacent to x4, x3 is less than x4, y3 is more than or equal to 0, y4 is less than or equal to 0, or y3 is less than or equal to 0, and y4 is more than or equal to 0, then x3, x4, y3 and y4 are taken out.
And finally, according to a calculation formula, solving the time difference between the two points x1 and x2, subtracting the error value after linearization processing, and solving the reciprocal to obtain the actual power frequency.
In the present application, a sine wave signal is input and sampled (similarly, taking n =8 as an example, an array with a size of 512 is initialized, and 512 sampled points are stored in the array); taking out sampling points which meet the conditions and corresponding sampling values by adopting a proper program rule (comparing the sampling values with zero points by using a for loop and an if judgment statement); carrying out linearization processing on the obtained sampling values (the slope of a line segment between adjacent sampling points is regarded as constant); and calculating the time interval between sampling points, and substituting the obtained sampling values and the sampling points into a formula to calculate the frequency.
The method solves the problems that the power frequency calculated by the existing method is large in error and inaccurate, can basically eliminate errors, and can more accurately measure the actual power frequency after being interfered by the outside world.
As shown in fig. 5, the apparatus for calculating power frequency of the present application includes: an input unit 201 for inputting a sine wave signal, the sine wave signal being a three-phase alternating current voltage or a three-phase alternating current signal; the sampling unit 202 is used for sampling an input sine wave signal, wherein the sampling frequency f is 2^ n times of 50Hz, and n is an integer greater than 1; the storage unit 203 is used for storing sampling values corresponding to 2^ (n + 1) continuous sampling points into an array; and the calculating unit 204 is configured to perform linearization processing on the sampling points in the array that satisfy the preset condition, and calculate the actual power frequency according to the result of the linearization processing.
Wherein the calculation unit is configured to: and carrying out linearization processing on the sampling points intersected with the time axis or two adjacent sampling points nearest to the time axis in the array, and calculating the actual power frequency according to the linearization processing result.
Wherein the calculation unit is configured to:
traversing the array, wherein sampling points to be taken out comprise x1 and x2, the corresponding sampling values are y1 and y2, x1 is more than x2, y1 is less than or equal to 0, y2 is more than or equal to 0 or y1 is more than or equal to 0, and y2 is less than or equal to 0; the sampling points to be taken out also comprise x3 and x4, the corresponding sampling values are y3 and y4, x3 is more than x4, y3 is more than or equal to 0, y4 is less than or equal to 0 or y3 is less than or equal to 0, and y4 is more than or equal to 0; x1 and x2 differ by 1/f Mining X3 and x4 differ by 1/f Mining Calculating the actual power frequency by using the following equation:
wherein f is Mining ＝50×2^n Hz，n＝2,3,4……。
In the present application, the embodiment of the apparatus for calculating power frequency is basically similar to the embodiment of the method for calculating power frequency, and please refer to the introduction of the embodiment of the method for calculating power frequency for relevant places.
The present application further provides a computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the steps of any of the above methods when executing the program.
Embodiments of the present invention further provide a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements the method steps for calculating power frequency. The computer-readable storage medium may include, but is not limited to, any type of disk including floppy disks, optical disks, DVD, CD-ROMs, microdrive, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic or optical cards, nanosystems (including molecular memory ICs), or any type of media or device suitable for storing instructions and/or data.
All functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may be separately used as one unit, or two or more units may be integrated into one unit; the integrated unit can be realized in a form of hardware, or in a form of hardware plus a software functional unit.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method of calculating power frequency, comprising:
inputting a sine wave signal, wherein the sine wave signal is a three-phase alternating current voltage or a three-phase alternating current signal;
sampling the input sine wave signal at a sampling frequency f Mining Is 2^ n times of 50Hz, and n is an integer more than 1;
storing sampling values corresponding to 2^ (n + 1) continuous sampling points into an array;
and carrying out linearization processing on the sampling points meeting the preset conditions in the array, and calculating the actual power frequency according to the linearization processing result.
2. The method for calculating power frequency according to claim 1, wherein the step of linearizing the sampling points in the array that satisfy the preset condition and calculating the actual power frequency according to the result of the linearization comprises:
and carrying out linearization processing on the sampling points intersected with the time axis or two adjacent sampling points nearest to the time axis in the array, and calculating the actual power frequency according to the linearization processing result.
3. The method for calculating power frequency according to claim 1 or 2, wherein the step of linearizing the sampling points in the array that satisfy the preset condition and calculating the actual power frequency according to the result of the linearization comprises:
traversing the array, wherein the sampling points taken out comprise x1 and x2, the corresponding sampling values are y1 and y2, x1 is more than x2, x1 and x2 are adjacent sampling points, y1 is less than or equal to 0, y2 is more than or equal to 0 or y1 is more than or equal to 0, and y2 is less than or equal to 0; the taken sampling points also comprise x3 and x4, the corresponding sampling values are y3 and y4, x3 is more than x4, x3 and x4 are adjacent sampling points, y3 is more than or equal to 0, y4 is less than or equal to 0, or y3 is less than or equal to 0, and y4 is more than or equal to 0; the sampling points x1 and x2 differ by 1/f Mining X3 and x4 differ by 1/f Mining Calculating the actual power frequency by using the following equation:
wherein f is Mining ＝50×2^n Hz，n＝2,3,4……。
4. The method of claim 3, wherein n =8, x1 and x2 differ by 78.125us, and x3 and x4 differ by 78.125us.
5. The method of claim 3, wherein the sampling points x1 and x3 are separated by a zero crossing.
6. An apparatus for calculating power frequency, comprising:
the input unit is used for inputting sine wave signals, and the sine wave signals are three-phase alternating-current voltages or three-phase alternating-current signals;
the sampling unit is used for sampling an input sine wave signal, wherein the sampling frequency f is 2^ n times of 50Hz, and n is an integer greater than 1;
the storage unit is used for storing sampling values corresponding to 2^ (n + 1) continuous sampling points into an array;
and the calculation unit is used for carrying out linearization processing on the sampling points meeting the preset conditions in the array and calculating the actual power frequency according to the linearization processing result.
7. The apparatus for calculating power frequency of claim 6, wherein the calculating unit is configured to:
and carrying out linearization processing on the sampling points intersected with the time axis or two adjacent sampling points nearest to the time axis in the array, and calculating the actual power frequency according to the linearization processing result.
8. The apparatus for calculating power frequency according to claim 6 or 7, wherein the calculation unit is configured to:
traversing the array, wherein the sampling points taken out comprise x1 and x2, the corresponding sampling values are y1 and y2, x1 is more than x2, x1 and x2 are adjacent sampling points, y1 is less than or equal to 0, y2 is more than or equal to 0 or y1 is more than or equal to 0, and y2 is less than or equal to 0; the taken sampling points also comprise x3 and x4, the corresponding sampling values are y3 and y4, x3 is more than x4, x3 and x4 are adjacent sampling points, y3 is more than or equal to 0, y4 is less than or equal to 0, or y3 is less than or equal to 0, and y4 is more than or equal to 0; the sampling points x1 and x2 differ by 1/f Mining X3 and x4 differ by 1/f Mining Calculating the actual power frequency by using the following equation:
wherein f is Mining ＝50×2^n Hz，n＝2,3,4……。
9. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 5.
10. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the steps of the method of any of claims 1-5 are implemented when the program is executed by the processor.
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| CN102116798A (en) * | 2011-03-07 | 2011-07-06 | 深圳市锐能微科技有限公司 | Power grid frequency measurement method and device |
| CN102809687A (en) * | 2012-07-26 | 2012-12-05 | 南京邮电大学 | Digital measurement method for alternating-current frequency |
| CN103235177A (en) * | 2013-03-12 | 2013-08-07 | 中北大学 | Three-phase alternating current frequency sampling method realized by software algorithm |
| CN114384312A (en) * | 2021-12-31 | 2022-04-22 | 北京四方继保工程技术有限公司 | Method for calculating protective phasor of variable frequency motor |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102116798A (en) * | 2011-03-07 | 2011-07-06 | 深圳市锐能微科技有限公司 | Power grid frequency measurement method and device |
| CN102809687A (en) * | 2012-07-26 | 2012-12-05 | 南京邮电大学 | Digital measurement method for alternating-current frequency |
| CN103235177A (en) * | 2013-03-12 | 2013-08-07 | 中北大学 | Three-phase alternating current frequency sampling method realized by software algorithm |
| CN114384312A (en) * | 2021-12-31 | 2022-04-22 | 北京四方继保工程技术有限公司 | Method for calculating protective phasor of variable frequency motor |
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