CN108957132A - A kind of Measurement of Harmonics in Power System device and its detection method based on synchronized sampling complete cycle - Google Patents

Abstract

The present invention provides a power system harmonic detection device and detection method based on synchronous sampling of the whole cycle. The harmonic detection device includes a current transformer, a voltage transformer, a signal conditioning circuit, an A/D conversion module, and a phase-locked loop. frequency multiplication circuit and signal acquisition and processing module; the harmonic detection device obtains current and voltage information through the current transformer and the voltage transformer, and the detected current and voltage information are conditioned by the conditioning circuit and then passed The A/D conversion module converts digital signals into the signal acquisition and processing module, and the signal acquisition and processing module can monitor, analyze and calculate the voltage fundamental frequency and the current fundamental frequency, and then realize the harmonic detection function, and Store and display the test results. The invention provides a power system harmonic detection device and a detection method based on full cycle synchronous sampling, which effectively improves the accuracy of power harmonic detection.

Description

A power system harmonic detection device based on full cycle synchronous sampling and its detection method

technical field

The invention belongs to the technical field of power detection, and in particular relates to a power system harmonic detection device and a detection method based on full-period synchronous sampling.

Background technique

Since entering the electrical age, electricity has become an indispensable and important energy source in the 21st century. With the continuous progress of society and the rapid development of economy, human production and living standards have been greatly improved. Various models in the power system Non-linear loads such as electric motors, rectifiers, electric arc furnaces, and AC/DC converters, as well as impact loads continue to increase, resulting in more serious power harmonic problems in public power grids. The direct manifestation of the impact of these nonlinear loads on the power system is the serious distortion of the current and voltage waveforms. Not only the sinusoidal quantity with the same frequency as the power supply, called the fundamental wave component, but also the frequency is an integer of the frequency of the fundamental wave component. times a series of sinusoidal components, this series of components is the power harmonics.

For the power system, the seriousness of harmonic pollution cannot be ignored, it will reduce the efficiency of production, transmission and utilization of electric energy; it will cause some failures without warning, which may cause the machine to be burned; Seriously interfere with the normal work of communication equipment in the power system. In the electric power and electronics industry, the harmfulness of harmonic pollution in the power grid has become increasingly serious. It is necessary to effectively analyze the harmonic content in the power grid, and select the corresponding necessary suppression methods according to the data in the content. In order to ensure the safety of power grid operation, it is necessary to control the harmonics within the safe range to avoid the generation and expansion of harmonic hazards. Therefore, it is of great significance for the safe and economic operation of the power supply system, the protection of the power system and the safe operation of electrical equipment to study the harmonic problem of the power system in depth, eliminate the harmonic pollution, and control the harmonic content within the allowable range. At present, the frequency resolution of power harmonic detection technology is not high, and it is easily affected by spectrum leakage. How to improve and optimize it has become one of the tasks of power harmonic detection technology.

Contents of the invention

The invention provides a power system harmonic detection device and a detection method based on full cycle synchronous sampling, which effectively improves the accuracy of power harmonic detection.

The present invention is specifically a power system harmonic detection device based on full cycle synchronous sampling. The harmonic detection device includes a current transformer, a voltage transformer, a signal conditioning circuit, an A/D conversion module, and a phase-locked loop frequency multiplication circuit. and a signal acquisition and processing module, the input terminals of the current transformer and the voltage transformer are connected to the power grid, the output terminals of the current transformer and the voltage transformer are connected with the input terminals of the signal conditioning circuit, and the signal The output end of the conditioning circuit is connected with the input end of the A/D conversion module, the output end of the A/D conversion module is connected with the input end of the signal acquisition and processing module, and the phase-locked loop frequency multiplier circuit The input terminal is connected to the output terminal of the voltage transformer, and the output terminal of the phase-locked loop frequency multiplier circuit is connected to the signal acquisition and processing module; the harmonic detection device passes the current transformer and the voltage transformer The transformer acquires current and voltage information, and the detected current and voltage information are conditioned by the signal conditioning circuit, and then converted into digital signals by the A/D conversion module and transmitted to the signal acquisition and processing module, and the signal acquisition The processing module can monitor, analyze and calculate the voltage fundamental frequency and current fundamental frequency, and then realize the harmonic detection function, and store and display the detection results.

The signal conditioning circuit includes an adding circuit and a filter circuit to adjust the input signal to meet the working requirements of the A/D conversion module.

The phase-locked loop frequency multiplication circuit adopts a method of uniformly sampling the measured signal at equal intervals within one cycle, which can realize synchronous sampling throughout the cycle and avoid the phenomenon of spectrum leakage in the signal acquisition link; the phase-locked loop frequency multiplication circuit The CD4046 chip is used as the phase-locked loop, the power supply voltage range is 3-18V, the input impedance is 100MΩ, and the sampling frequency in a whole cycle is 128.

The signal acquisition and processing module can calculate the three-phase current, three-phase voltage, active power, reactive power and harmonic distortion rate of the grid, and the signal acquisition and processing module includes an ARM processor, a storage module, a display module and a communication module, the ARM processor is respectively connected to the storage module, the display module and the communication module; the ARM processor uses the minimum mode multiple signal classification algorithm to analyze and process the collected signal to obtain each harmonic Amplitude and frequency and their parameter characteristic curves, the required parameters can be obtained through relevant mathematical calculations, and the harmonic detection function can be realized, and then stored through the storage module, displayed through the display module, and through the communication The module realizes remote communication.

The harmonic detection device adopts the minimum mode multiple signal classification algorithm to detect harmonics, and the detection method includes the following steps:

Step 1: List the discrete-time functions according to the input signal of the signal acquisition and processing module

Said x(n) is a sampling signal, said M is a harmonic order, said b _i is the amplitude of the i-th harmonic, said fi is the _i -th harmonic frequency, and said Δt is a sampling time interval, Described v (n) is white noise;

Step 2, establish an autocorrelation function according to the discrete time function, form an autocorrelation matrix by the autocorrelation function, calculate and obtain an autocorrelation matrix including an eigenvalue matrix of signal frequency information and a corresponding space vector matrix, and the autocorrelation function for The N is the number of sampling points; the autocorrelation matrix composed of (p+1) r _x (m) Calculate the eigenvalues of the autocorrelation matrix through the signal vector matrix e _i =[1,exp(j2πf _i ),···,exp(j2πf _i p)] ^T ,i=1,2,···,M matrix and the corresponding space vector matrix;

Step 3, using the minimum description length criterion to determine the number of signal sources according to the eigenvalue matrix, the minimum description length criterion The C is the number of the eigenvalues, the said said The λ _i is the i-th eigenvalue; the M is the number of signal sources sought;

Step 4: Use the minimum modulus method to separate and transform the noise space vector of the multiple signal classification algorithm to obtain the power spectrum analysis curve The e(ω)=[1,exp(j2πf _i ),···,exp(j2πf _i p)] ^T , the The E _N is the remaining rows of the noise subspace except m, and the m is the first row of the noise vector space; the power spectrum analysis curve is relatively gentle, and there is a peak at ω= _ωi , and the corresponding Frequency is the frequency of the harmonic signal.

Description of drawings

FIG. 1 is a schematic structural diagram of a power system harmonic detection device based on full-period synchronous sampling according to the present invention.

Detailed ways

A specific implementation of a power system harmonic detection device and detection method based on full-period synchronous sampling according to the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, the harmonic detection device of the present invention comprises a current transformer, a voltage transformer, a signal conditioning circuit, an A/D conversion module, a phase-locked loop frequency multiplication circuit and a signal acquisition and processing module, the current transformer and The input end of the voltage transformer is connected to the grid, the output ends of the current transformer and the voltage transformer are connected to the input end of the signal conditioning circuit, and the output end of the signal conditioning circuit is connected to the A/D conversion The input end of the module is connected, the output end of the A/D conversion module is connected with the input end of the signal acquisition and processing module, and the input end of the phase-locked loop frequency multiplication circuit is connected with the output end of the voltage transformer , the output end of the phase-locked loop frequency multiplier circuit is connected to the signal acquisition and processing module; the harmonic detection device obtains current and voltage information through the current transformer and the voltage transformer, and passes the signal The conditioning circuit adjusts the detected current and voltage information, and then converts it into a digital signal through the A/D conversion module and transmits it to the signal acquisition and processing module. The frequency is monitored, analyzed and calculated, and then the harmonic detection function is realized, and the detection results are stored and displayed.

The signal conditioning circuit includes an adding circuit and a filter circuit to adjust the input signal to meet the working requirements of the A/D conversion module.

The phase-locked loop frequency multiplication circuit adopts a method of uniformly sampling the measured signal at equal intervals within one cycle, which can realize synchronous sampling throughout the cycle and avoid the phenomenon of spectrum leakage in the signal acquisition link; the phase-locked loop frequency multiplication circuit The CD4046 chip is used as the phase-locked loop, the power supply voltage range is 3-18V, the input impedance is 100MΩ, and the sampling frequency in a whole cycle is 128.

The signal acquisition and processing module can calculate the three-phase current, three-phase voltage, active power, reactive power and harmonic distortion rate of the grid, and the signal acquisition and processing module includes an ARM processor, a storage module, a display module and a communication module, the ARM processor is respectively connected to the storage module, the display module and the communication module; the ARM processor uses the minimum mode multiple signal classification algorithm to analyze and process the collected signal to obtain each harmonic Amplitude and frequency and their parameter characteristic curves, the required parameters can be obtained through relevant mathematical calculations, and the harmonic detection function can be realized, and then stored through the storage module, displayed through the display module, and through the communication The module realizes remote communication.

The harmonic detection device adopts the minimum mode multiple signal classification algorithm to detect harmonics, and the detection method includes the following steps:

Step 1: List the discrete-time functions according to the input signal of the signal acquisition and processing module

Said x(n) is a sampling signal, said M is a harmonic order, said b _i is the amplitude of the i-th harmonic, said fi is the _i -th harmonic frequency, and said Δt is a sampling time interval, Described v (n) is white noise;

Step 2, establish an autocorrelation function according to the discrete time function, form an autocorrelation matrix by the autocorrelation function, calculate and obtain an autocorrelation matrix including an eigenvalue matrix of signal frequency information and a corresponding space vector matrix, and the autocorrelation function for The N is the number of sampling points; the autocorrelation matrix composed of (p+1) r _x (m) Calculate the eigenvalues of the autocorrelation matrix through the signal vector matrix e _i =[1,exp(j2πf _i ),···,exp(j2πf _i p)] ^T ,i=1,2,···,M matrix and the corresponding space vector matrix;

Step 3, using the minimum description length criterion to determine the number of signal sources according to the eigenvalue matrix, the minimum description length criterion The C is the number of the eigenvalues, the said said The λ _i is the i-th eigenvalue; the M is the number of signal sources sought;

Step 4, use the minimum modulus method to separate and transform the noise space vector of the multiple signal classification algorithm, and obtain the power spectrum analysis curve The e(ω)=[1,exp(j2πf _i ),···,exp(j2πf _i p)] ^T , the The E _N is the remaining rows of the noise subspace except m, and the m is the first row of the noise vector space; the power spectrum analysis curve is relatively gentle, and there is a peak at ω= _ωi , and the corresponding Frequency is the frequency of the harmonic signal.

Finally, it should be noted that the combination of the above embodiments only illustrates the technical solution of the present invention rather than limiting it. Those of ordinary skill in the art should understand that those skilled in the art can modify or equivalently replace the specific embodiments of the present invention, but these modifications or changes are within the protection scope of the pending claims.

Claims (5)

1. a kind of Measurement of Harmonics in Power System device based on synchronized sampling complete cycle, which is characterized in that the harmonic detecting dress It sets including current transformer, voltage transformer, signal conditioning circuit, A/D conversion module, frequency multiplication of phase locked loop circuit and signal acquisition The input terminal of processing module, the current transformer and voltage transformer is connect with power grid, and the current transformer and voltage are mutual The output end of sensor is connected with the input terminal of the signal conditioning circuit, the output end of the signal conditioning circuit with it is described The input terminal of A/D conversion module is connected, the output end of the A/D conversion module and the signal acquisition process module input terminal It is connected, the input terminal of the frequency multiplication of phase locked loop circuit is connect with the output end of the voltage transformer, the frequency multiplication of phase locked loop The output end of circuit is connected with the signal acquisition process module；The harmonic measurement device by the current transformer and The voltage transformer obtains electric current, information of voltage, by the signal conditioning circuit to detect electric current, information of voltage into Row conditioning is converted into digital data transmission to the signal acquisition process module, the signal by the A/D conversion module again Acquisition processing module can be monitored, analyze and calculate to voltage fundamental frequency and current first harmonics frequency, and then realize humorous Wave detection function, and will test result and carry out storage and show.

2. a kind of Measurement of Harmonics in Power System device based on synchronized sampling complete cycle according to claim 1, feature It is, the signal conditioning circuit includes add circuit and filter circuit, realizes the adjustment to input signal to reach the A/D The job requirement of conversion module.

3. a kind of Measurement of Harmonics in Power System device based on synchronized sampling complete cycle according to claim 1, feature It is, the method that the frequency multiplication of phase locked loop circuit takes in one cycle measured signal uniform sampling at equal intervals, Neng Goushi Existing synchronized sampling complete cycle, avoiding the acquisition link of signal, there is a phenomenon where spectral leakages；The frequency multiplication of phase locked loop circuit uses CD4046 chip realizes adopting in a complete cycle as phaselocked loop, 3~18V of supply voltage range, input impedance 100M Ω Sample frequency is 128.

4. a kind of Measurement of Harmonics in Power System device based on synchronized sampling complete cycle according to claim 1, feature It is, the signal acquisition process module can calculate three-phase current, three-phase voltage, active power, the idle function of the power grid Rate and percent harmonic distortion, the signal acquisition process module include arm processor, memory module, display module and communication mould Block, the arm processor are connected respectively to the memory module, the display module and the communication module；The ARM processing Device is analyzed and processed the signal of acquisition using minimum modulus multiple signal classification algorithm, obtains the amplitude and frequency of each harmonic And their parameter characteristic, required parameter can be obtained by relevant mathematical computations, realizes harmonic detection function, into And stored by the memory module, it is shown, is realized by the communication module long-range by the display module Communication.

5. a kind of Measurement of Harmonics in Power System dress described in any one of -4 based on synchronized sampling complete cycle according to claim 1 The detection method set, which is characterized in that the harmonic measurement device carries out harmonic wave inspection using minimum modulus multiple signal classification algorithm It surveys, detection method includes the following steps:

Step 1 lists discrete time function according to signal acquisition process module input signal N=0,1, N-1, the x (n) is sampled signal, and the M is overtone order, the b_iFor the amplitude of i-th harmonic wave, The f_iI-th harmonic frequency, the Δ t are sampling time interval, and the v (n) is white noise；

Step 2, establishes auto-correlation function according to the discrete time function, forms autocorrelation matrix by the auto-correlation function, The eigenvalue matrix and corresponding space vector matrix that autocorrelation matrix includes signal frequency information, the auto-correlation is calculated Function isThe N is sampling number；By (p+1) a r_x(m) the auto-correlation square formed Battle arrayPass through signal vector matrix e_i=[1, exp (j2 π f_i),···,exp(j2πf_ip)]^T, i=1,2, M calculates the eigenvalue matrix and correspondence of the autocorrelation matrix Space vector matrix；

Step 3 determines number of sources, the minimum description length according to eigenvalue matrix using Minimum description length criterion CriterionThe C is the number of the characteristic value, institute It statesIt is describedIt is describedThe λ_iFor i-th of characteristic value；Institute Stating M is exactly required number of sources；

Step 4 is separated and is converted amendment using spatial noise vector of the minimum modulus method to multiple signal classification algorithm, Obtain power spectrumanalysis curveK=M+1, p+1, the e (ω)=[1, exp(j2πf_i),···,exp(j2πf_ip)]^T, describedThe E_NIt is noise subspace in addition to m Remaining row, the m be noise vector space the first row；The power spectrumanalysis curve is relatively gentle, in ω=ω_iPlace is in Show spike, corresponding frequency is the frequency of harmonic signal at peak point.