CN104155509A - Method of acquiring power signal phase difference of power system - Google Patents

Abstract

The invention relates to a method for acquiring the phasor difference of electric quantity signals in a power system. In the calculation of electric quantity phasor difference in the prior art, the angular frequencies of the involved phasors must be the same. When the sampling frequency of the hardware is fixed, the Fourier transform is usually used to fulfill the above requirements, but the Fourier transform is complex and takes a long time for hardware calculation, so it has not been widely used. The calculation process of the electric quantity phasor difference in the present invention includes an analog electric quantity acquisition link, an A/D conversion and sampling link, an electric quantity parameter calculation and a correction link. In the present invention, the above-mentioned problem is solved by using a concise cycle algorithm to calculate the electric quantity phasor difference, and at the same time, the requirement of engineering precision is met. This method reduces the operational burden of the digital signal processor, enabling it to perform signal processing efficiently; it does not need to increase hardware overhead and change hardware design; at the same time, the proposed method can be generally applied to other power system occasions.

Description

A Method for Acquiring Phasor Difference of Electricity Signal in Power System

technical field

The invention relates to a method for acquiring a phasor difference, in particular to a method for acquiring a phasor difference of an electric quantity signal of a power system.

Background technique

The magnitude of the phasor in the power system is an important observation quantity: in the force system of the power system, the emergency control device of frequency and voltage needs to measure the change of the magnitude of its phasor in real time and take corresponding control measures; the energy storage system needs to monitor the phase The amplitude of the phasor is used to determine the power type and its flow direction; the grid-connected phase verification device can accurately ensure the range of the phasor amplitude to be connected to the grid, etc.

At present, the most widely used phasor amplitude calculation methods in the power system field are the root mean square method and the Fourier transform algorithm, but both the root mean square method and the Fourier transform algorithm require the sampling interval T _s and the number of sampling points per cycle N, period T satisfy strict calculation relationship Otherwise, the calculated amplitude will have a large error, and even in some occasions, the error is too large to be acceptable. When the frequency of the power system changes, the solution to the above problems is usually to adjust the sampling pulse of the A/D to satisfy the relation Simultaneous sampling is carried out so that it meets the error requirements. This calculation process is relatively cumbersome and the scope of application is limited by frequency. Therefore, it is urgent to propose a calculation method for power system phasor difference that is generally applicable to engineering and has high measurement accuracy, so as to solve the above-mentioned problems in current engineering implementation.

Contents of the invention

The purpose of the present invention is to provide a simple method for acquiring the phasor difference of electric quantity signal of electric power system.

The present invention adopts the following schemes to realize: a method for obtaining the phasor difference of electric quantity signals in a power system, which is characterized in that it includes providing analog electric quantity acquisition links, A/D conversion and sampling links, and electric quantity parameter calculation and correction links; the specific steps are as follows: : Step S01: Transform the high voltage and high current in the power system into the voltage level accepted by the measurement system through the transformer, low-pass filter circuit and shaping circuit, for the subsequent circuit to use; Step S02: Convert the continuous analog signal provided by the analog power collection link Converted into discrete digital signals that can be utilized by the digital modules in the measurement system; Step S03: Using the discrete digital signals, calculate the effective value of electricity and the phasor difference of electricity, and use the calculated effective value of electricity to verify the entire calculation method rationality.

The specific steps of step S03 described therein include: S031: According to the required calculation accuracy, set the number of input sampling points N, and generate m empty arrays Sample_i[N] by the computer program, where m is the electrical circuit input by the A/D sampling link number, i is the serial number of the sampling voltage, i=1, 2, 3...; S032: the counter in the measurement system starts counting, sets the sampling count as SAM_CNT, and saves the input N discrete points as Sample_i[n], Sample_i[n] is the nth sampling value of the i-th discrete quantity;

S033: According to $u_{\mathrm{ei}}=\frac{1}{N}\sqrt{\underset{\mathrm{no}=1}{\overset{N}{\mathrm{\Σ}}}{(\mathrm{Sample}\_i[\mathrm{no}\left]\right)}^2}---\left(1\right)$ and $u_{\mathrm{eij}}=\frac{1}{N}\sqrt{\underset{\mathrm{no}=1}{\overset{N}{\mathrm{\Σ}}}{(\mathrm{Sample}\_i[\mathrm{no}]-\mathrm{Sample}\_j[\mathrm{no}\left]\right)}^2}---\left(2\right)$ Calculate the power parameters, where i and j are the sampling voltage numbers, i=1, 2, 3..., U _ei is the effective value of the i-th voltage, and U _eij is the phasor difference between the i-th power and the j-th power Effective values, U _ei and U _eij are displayed through the display screen of the measurement system;

S034: Use a multimeter or other precision measuring instruments to determine the exact value of the electricity to be tested, denoted as _Xi , input the exact value into the measurement system, and calculate the correction parameter K: Then according to the formula X _ij =K×U _eij (4), the phasor difference X _ij of the input electric quantity i and j is obtained; S035: add 1 to the sampling count SAM_CNT, and return to step S031, and each calculation needs to refresh the output display value until SAM_CNT equal to N.

The method for obtaining the phasor difference of the power signal of the power system can calculate the power system at different frequencies through a simple cycle algorithm, and the power phasor difference that meets the requirements of engineering applications. The invention avoids the tedious Fourier conversion process, sets the calculation accuracy according to the engineering needs, and then performs a correction. During the use process, the parameters can be verified and corrected, so that it can be truly applied in engineering practice, and at the same time, it is not affected by frequency. Further improve its engineering applicability. The proposed phasor difference calculation method can also be easily applied to other power system occasions.

Description of drawings

Fig. 1 is a flow chart of the present invention for obtaining the phasor difference of electric quantity parameters of a power system.

Fig. 2 is a flow chart of calculation and correction of power parameters in the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a specific flow chart of the present invention. The calculation process of the electric quantity phasor difference in the present invention includes an analog electric quantity acquisition link, an A/D conversion and sampling link, an electric quantity parameter calculation and a correction link.

The analog power acquisition link is to convert high voltage and high current in the power system into voltage and current levels acceptable to the measurement system through transformers, low-pass filter circuits, and shaping circuits for use in subsequent circuits. The high voltage and high current of the power system first pass through the transformer, then pass through the low-pass filter to filter out the high-order harmonics, and finally convert the high voltage and high current into acceptable voltage and current levels for the measurement system through the shaping circuit . In a specific embodiment, the input terminal of the analog power collection link is a voltage or current signal with a higher voltage level, and the output is a voltage signal with a voltage level of -5 to 5V.

The A/D conversion and sampling link realizes the conversion of analog signal to digital signal, and converts the continuous analog signal provided by the analog power collection link into a discrete digital signal that can be used by the digital system, and the output discrete digital signal can be used to calculate power supply parameters In this link, the power related parameters and phasor difference calculations are carried out.

The parameter calculation in the power parameter calculation and calibration link includes the calculation of the effective value of the electric quantity and the effective value of the phasor difference of the electric quantity, wherein the calculation result of the effective electric quantity can be used to check the rationality of the entire calculation method.

Fig. 2 is a specific flow chart of parameter calculation in the power parameter calculation and calibration link. Include the following specific steps:

(1): According to the required calculation accuracy, the number of input sampling points N is manually or automatically set by the staff, and m empty arrays Sample_i[N] are generated by the computer program, where m is the number of power circuits input by the A/D sampling link, i is the serial number of the sampling voltage, i=1,2,3...; (2): the counter in the measurement system starts counting, the sampling count is set as SAM_CNT, and the input N discrete points are saved as Sample_i[n], Sample_i[n] is the nth sampling value of the i-th discrete quantity; (3): According to $u_{\mathrm{ei}}=\frac{1}{N}\sqrt{\underset{\mathrm{no}=1}{\overset{N}{\mathrm{\Σ}}}{(\mathrm{Sample}\_i[\mathrm{no}\left]\right)}^2}---\left(1\right)$ and $u_{\mathrm{eij}}=\frac{1}{N}\sqrt{\underset{\mathrm{no}=1}{\overset{N}{\mathrm{\Σ}}}{(\mathrm{Sample}\_i[\mathrm{no}]-\mathrm{Sample}\_j[\mathrm{no}\left]\right)}^2}---\left(2\right)$ Calculate the power parameters, where i and j are the sampling voltage numbers, i=1, 2, 3..., U _ei is the effective value of the i-th voltage, and U _eij is the phasor difference between the i-th power and the j-th power Effective value, U _ei and U _eij are displayed through the display screen of the measurement system; (4): use a multimeter or other precision measuring instruments to determine the exact value of the electric power to be tested, denoted as _Xi , and input this value to the measurement system Accurate value, the calculation can get the correction parameter K: Then according to the formula X _ij =K×U _eij (4) to get the phasor difference X _ij of the input electric quantity i, j; (5): add 1 to the sampling count SAM_CNT, return to step 1, each calculation needs to refresh the output display value, Until SAM_CNT is equal to N.

In a specific embodiment of the present invention:

To measure the phasor difference of the input power of a transformer, the staff manually or automatically set the number of input sampling points N, and according to the actual engineering calculation accuracy, N needs to be obtained as 256 sampling points per cycle; the calculation program generates m (m=2) empty The array Sample_i[256], that is, the 2-way input of the A/D sampling link, the measurement system counter starts counting, and saves the 256 discrete points input by the A/D sampling link as Sample_i[n] (i=1, 2; n=1 ,2,3...256). Sample_i[n] is the nth sampling value of the i-th discrete quantity.

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; ei</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 256</span>}}\sqrt{\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 256</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Sample</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 256</span>}}\sqrt{\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 256</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Sample</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Sample</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Use a multimeter or other precision measuring instruments to measure the precise value of the electric quantity at the input end of the transformer, denoted as X _i , input the precise value through the human-computer interaction interface of the measurement system, and obtain the correction parameter K through formula (3), which will be specifically Values are substituted into the formula (4) to get X ₁₂ =K×U _e12 (7), thus obtaining the phasor difference X ₁₂ of the input electric quantities X ₁ and X ₂ . The sampling count SAM_CNT is increased by 1, and the calculation is restarted. Each calculation needs to refresh the displayed value until SAM_CNT is N.

The above-mentioned embodiments do not limit the present invention in any way, and all changes made according to the technical solution of the present invention, when the functional effect produced does not exceed the scope of the technical solution of the present invention, all belong to the protection scope of the present invention.

Claims (2)

1. A method for obtaining the phasor difference of electric quantity signals in a power system, characterized in that: it includes providing an analog electric quantity acquisition link, an A/D conversion and sampling link, and an electric quantity parameter calculation and correction link; The specific steps are: Step S01: Transform the high voltage and high current in the power system into a voltage level accepted by the measurement system through a transformer, a low-pass filter circuit and a shaping circuit for use in subsequent circuits; Step S02: Converting the continuous analog signal provided by the analog power collection link into a discrete digital signal that can be utilized by the digital module in the measurement system; Step S03: Using the discrete digital signal, calculate the effective value of electricity and the phasor difference of electricity, and at the same time use the calculated effective value of electricity to check the rationality of the entire calculation method. 2. The method for obtaining the phasor difference of the power system electrical quantity signal according to claim 1, characterized in that: the specific steps of the step S03 include: S031: According to the required calculation accuracy, set the number of input sampling points N , and generate m empty arrays Sample_i [ N ] by the computer program, where m is the number of power circuits input by the A/D sampling link, i is the serial number of the sampling voltage, i =1,2,3...; S032: The counter in the measurement system starts counting, sets the sampling count as SAM_CNT, saves the input N discrete points as Sample_i [ n ], and Sample_i [ n ] is the nth sampling of the i- th discrete quantity value; S033: According to (1) and (2) Calculate the power parameters, where i and j are the serial numbers of the sampling voltage, i =1,2,3..., is the effective value of the i -th road voltage, is the effective value of the phasor difference between the i- th electric quantity and the j- th electric quantity, and , display through the display screen of the measuring system; S034: Use a multimeter or other precision measuring instruments to determine the exact value of the electricity to be tested, recorded as , input the precise value to the measurement system, and the calculation can obtain the correction parameter K : (3), then according to the formula (4) Obtain the phasor difference of input electric quantity i , j ; S035: Add 1 to the sampling count SAM_CNT, return to step S031, and refresh the output display value for each calculation until SAM_CNT is equal to N.