Specified cluster harmonic extraction method, system and device and storage medium

Abstract

The invention discloses a specified cluster harmonic extraction method, system and device, and a storage medium. The method comprises the steps of obtaining a three-phase to-be-measured discrete signal in a power system; converting the three-phase discrete signal to be measured into a signal to be measured under a two-phase static coordinate system; inputting the to-be-measured signal into a comb filter, and filtering each frequency harmonic component to obtain a processed signal; inputting the processed signal into an improved undamped vector digital oscillator, and restoring and extracting a harmonic signal corresponding to each frequency; inputting the corresponding parameters into the harmonic signal of each frequency, adjusting the amplitude and the phase of the comb filter in the filtering process, ensuring that the amplitude and the gain of the frequency spectrum of the harmonic signal are consistent, and completing harmonic extraction; according to the invention, the harmonic extraction speed is improved, and rapid harmonic extraction is realized.

Description

Technical Field

[0001] The present invention relates to a harmonic extraction method, system, device and storage medium, and in particular to a specified cluster harmonic extraction method, system, device and storage medium, belonging to the field of big data technology. Background Art

[0002] Active filter is an effective device for controlling harmonic disturbance and resonance in power transmission and distribution network. Its control link includes harmonic extraction. Industry requires that the dynamic response time of active filter should be as short as possible. As the first signal processing link of active filter, harmonic extraction should also improve its dynamic response capability as much as possible. There are several traditional harmonic extraction solutions:

[0003] Improved IP-IQ algorithm: This method is an algorithm for power quality analysis and harmonic detection, which is based on the theory of instantaneous reactive power. The improved IP-IQ algorithm can improve its accuracy and real-time performance in power quality monitoring, but the harmonic extraction speed of this method is slow.

[0004] Fast Fourier Transformation (FFT) and Discrete Fourier Transformation (DFT) algorithms: This type of method is based on frequency component calculation and has the advantages of high detection accuracy, selective harmonic extraction, and easy digital implementation.

[0005] Slide Discrete Fourier Transformation (SDFT) algorithm: Based on the DFT algorithm, SDFT reduces the amount of calculation while achieving the effect of the DFT algorithm.

[0006] The above harmonic extraction algorithm can theoretically accurately extract specific harmonics, but it is limited by problems such as poor dynamic response, large amount of calculation and poor frequency adaptability. It is not suitable for applications with frequently fluctuating harmonic currents and requires special digital implementation methods to ensure stability and real-time performance. Summary of the invention

[0007] Purpose of the invention: The purpose of the present invention is to provide a method, system, device and storage medium for extracting harmonics from a specified cluster that can increase the speed of harmonic extraction.

[0008] Technical solution: A method for extracting harmonics from a designated cluster according to the present invention comprises:

[0009] Obtain three-phase discrete signals to be measured in the power system;

[0010] Convert the three-phase discrete signal to be measured into the signal to be measured in a two-phase stationary coordinate system;

[0011] The signal to be tested is input into a comb filter to filter out the harmonic components of each frequency to obtain a processed signal;

[0012] The processed signal is input into an improved undamped vector digital oscillator to restore and extract the harmonic signals corresponding to each frequency;

[0013] The corresponding parameters are input into the harmonic signals of each frequency, and the amplitude and phase of the comb filter are adjusted during the filtering process to ensure that the amplitude and gain of the harmonic signal spectrum are consistent, thus completing the harmonic extraction.

[0014] Furthermore, the three-phase discrete signal to be measured in the power system is obtained by using voltage and current sensors at a frequency of N / T 0 Collect continuous voltage and current signals in the power system and obtain the abc three-phase discrete signal x to be measured at the nth frequency in the system abc (n), where N is the number of samples, T 0 is the fundamental period of the current sensor.

[0015] Furthermore, the three-phase discrete signal to be measured is converted into the signal to be measured in the two-phase stationary coordinate system, specifically, the abc three-phase voltage and current signals are converted into the α-β coordinate system to obtain the signal to be measured x αβ (n), where the expression for converting the abc axis to the dq axis is:

[0016]

[0017] Furthermore, the method of inputting the signal to be tested into a comb filter to filter out the harmonic components of each frequency to obtain a processed signal specifically includes: αβ (n) Transfer function H of the input to the comb filter c (z), H c (z) introducing a cluster of zero points to filter out the harmonics in the input signal to be measured to obtain a processed signal;

[0018] Let x αβ (n) has a cluster of harmonic components h=mk+l, where m, l are integers, and m>0, k=0,±1,±2,…; H c (z) is expressed as:

[0019]

[0020] Where z is the complex variable in the z-transform, e j represents the rotation factor, e is a constant, j is a complex variable, and N is the number of samples.

[0021] Furthermore, the processed signal is input into the improved undamped vector digital oscillator to restore and extract the harmonic signal of the corresponding frequency. Specifically, the processed signal is input into the transfer function of the undamped vector digital oscillator. In the process, the poles at the harmonic frequencies of the corresponding frequencies are constructed, the zeros at the harmonic frequencies of the corresponding frequencies are eliminated, and the harmonic signals of the corresponding frequencies are extracted. The transfer function of the undamped vector digital oscillator is It is expressed as:

[0022]

[0023] Furthermore, the corresponding parameters are input into the harmonic signals of each frequency, and the amplitude and phase in the comb filter filtering process are adjusted to ensure that the amplitude and gain of the harmonic signal spectrum are consistent. Specifically, the harmonic signal is input into the gain and phase adjustment coefficient γ k In the embodiment, the amplitude and phase of the comb filter output signal are adjusted to achieve unity gain and zero phase shift of the harmonic signal;

[0024] The gamma k The solution is:

[0025]

[0026] Among them, []′ is the derivative of the filter transfer function, e -j is the negative rotation factor.

[0027] Based on the same inventive concept, the present invention also provides a specified cluster harmonic extraction system, comprising:

[0028] An acquisition module is used to obtain three-phase discrete signals to be measured in the power system;

[0029] A conversion module, used for converting a three-phase discrete signal to be measured into a signal to be measured in a two-phase stationary coordinate system;

[0030] The filtering module is used to input the signal to be tested into a comb filter, filter out the harmonic components of each frequency, and obtain a processed signal;

[0031] A restoration module, used for inputting the processed signal into the improved undamped vector digital oscillator, restoring and extracting the harmonic signal corresponding to each frequency;

[0032] The extraction module is used to input the corresponding parameters into the harmonic signals of each frequency, adjust the amplitude and phase during the filtering process of the comb filter, ensure that the amplitude and gain of the harmonic signal spectrum are consistent, and complete the harmonic extraction.

[0033] Furthermore, the filtering module specifically includes: αβ(n) Transfer function H of the input to the comb filter c (z), H c (z) introducing a cluster of zero points to filter out the harmonics in the input signal to be measured;

[0034] The transfer function H c (z), let x αβ (n) has a cluster of harmonic components h=mk+l, where m, l are integers, and m>0, k=0,±1,±2,…; H c (z) is expressed as:

[0035]

[0036] Where z is the complex variable in the z-transform, e j represents the rotation factor, e is a constant, j is a complex variable, and N is the number of samples.

[0037] Based on the same inventive concept, the present invention also provides a computing device, comprising: one or more processors, one or more memories, and one or more programs, wherein the programs are stored in the memories and configured to be executed by the processors, and when the programs are loaded into the processors, the steps of the specified cluster harmonic extraction method according to any one of the above items are implemented.

[0038] Based on the same inventive concept, the present invention also provides a computer-readable storage medium, which stores a computer program, and the computer program includes program instructions. When the program instructions are executed by a processor, the processor executes the steps of the specified cluster harmonic extraction method described in any one of the above items.

[0039] Beneficial effects: Compared with the prior art, the present invention achieves the effect of compensating for the cumulative error by designing a rotation factor in an improved undamped vector digital oscillator, and can achieve the effect of reducing the harmonic delay of a specified cluster by designing its transfer function, thereby improving the harmonic extraction speed, realizing rapid extraction of harmonics, and reducing the detection time from 1 fundamental wave period to 1 / n fundamental wave period. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a flow chart of a method according to an embodiment of the present invention;

[0041] Figure 2 It is a schematic diagram of the principle of extracting harmonic signals of a designated cluster according to an embodiment of the present invention;

[0042] Figure 3 A schematic diagram of a comb filter corresponding to N zero points according to an embodiment of the present invention;

[0043] Figure 4A schematic diagram of a comb filter corresponding to N / 3 zero points according to an embodiment of the present invention;

[0044] Figure 5 A schematic diagram of an undamped vector digital oscillator improved according to an embodiment of the present invention;

[0045] Figure 6 A schematic diagram of the input and output relationship of each frequency in an embodiment of the present invention;

[0046] Figure 7 It is a schematic diagram of a harmonic current extraction waveform according to an embodiment of the present invention. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0048] As attached Figure 1 As shown, the specified cluster harmonic extraction method of this embodiment includes:

[0049] S1: Acquire the three-phase discrete signal to be measured in the power system;

[0050] S2: convert the three-phase discrete signal to be measured into the signal to be measured in a two-phase stationary coordinate system;

[0051] S3: Input the signal to be tested into a comb filter to filter out the harmonic components of each frequency to obtain a processed signal;

[0052] S4: inputting the processed signal into the improved undamped vector digital oscillator to restore and extract the harmonic signals corresponding to each frequency;

[0053] S5: Input corresponding parameters into the harmonic signals of each frequency, adjust the amplitude and phase in the comb filter filtering process, ensure that the amplitude and gain of the harmonic signal spectrum are consistent, and complete the harmonic extraction.

[0054] Specifically, Figure 2 The following is the principle of extracting the harmonic signal of a specified cluster. abc (n) represents the abc three-phase discrete signal to be measured. αβ (n) represents the measured signal converted to the Alpha-Beta coordinate system, H c (z) represents the transfer function of the comb filter in the discrete domain, represents the transfer function of the damped vector digital oscillator in the discrete domain, γ k Represents the gain of the filter stage. Represents the kth harmonic component of the signal to be measured converted to the Alpha-Beta coordinate system.

[0055] In step S1, the voltage and current sensors are used to generate the current at a frequency of N / T. 0 Collect the continuous voltage u(s) and current signal i(s) in the power system and obtain the three-phase discrete signal x to be measured in the system abc (n), the number of samples is N;

[0056] In step S2, the abc three-phase voltage and current signals are converted to the α-β coordinate system to obtain x αβ (n), the expression for converting the abc axis to the dq axis is:

[0057]

[0058] In step S3, x αβ (n) Input to H c (z), H c (z) can introduce a cluster of zeros to completely filter out the harmonics in the input signal α. αβ A cluster of harmonic components of (n) is h = mk + l, where m, l are integers, and m>0, k = 0, ±1, ±2, ..., H c (z) The transfer function can be expressed as,

[0059]

[0060] z is the complex variable in the z-transform, e j represents the rotation factor.

[0061] The comb filter is a typical finite impulse response filter. The traditional comb filter will introduce N zero points to filter out the corresponding frequency components. This method will introduce N-beat delays. In the power system, generally N sampling points correspond to one fundamental wave period, so a delay of one fundamental wave period will be introduced, and the speed of harmonic detection is slow. The process can be simplified for characteristic subharmonic extraction, and the harmonic frequency zero point of h=6k+1 and the harmonic frequency zero point of h=6k-1 can be extracted. At this time, the sampling point changes from N to N / 6+N / 6, corresponding to 1 / 3 of the fundamental wave period. For example Figure 3 , Figure 4 The zero point conditions of two comb filters are shown in Figure 2. The comb filter can be used with an undamped vector digital oscillator to introduce a harmonic frequency pole to achieve zero-pole cancellation and thus extract harmonics.

[0062] In step S4, the signal obtained in S3 is input to In the oscillator, a pole at a certain harmonic frequency is constructed, the zero at the harmonic frequency is eliminated, and then the harmonic signal of the frequency is extracted. The transfer function can be expressed as

[0063]

[0064] There is a peak from Figure 3 It can be seen from the figure that the detection system is in a critical stable state. Ideally, the selected poles and zeros can cancel each other to maintain system stability. However, when implementing multi-beat delay in the discrete domain, multiple errors will accumulate, which is the finite word length effect of the digital system. In order to avoid instability caused by error accumulation, Figure 5 The control block diagram shown is equivalent to function.

[0065] In step S5, the signal obtained in S4 is input into the gain / phase adjustment coefficient γ k In the filter, the amplitude and phase of the filter output signal are adjusted to achieve unity gain and zero phase shift for the harmonic signal. k The solution method is

[0066]

[0067] After designing the transfer functions under the kth harmonic, proceed to the design of the next frequency until the γ of each frequency is solved. The input-output relationship of each frequency is as follows: Figure 6 shown.

[0068] The waveform of the 6k±1 harmonic component in the system obtained by this method is as follows Figure 7 shown.

[0069] Based on the same inventive concept, this embodiment also provides a specified cluster harmonic extraction system, including:

[0070] An acquisition module is used to obtain three-phase discrete signals to be measured in the power system;

[0071] A conversion module, used for converting a three-phase discrete signal to be measured into a signal to be measured in a two-phase stationary coordinate system;

[0072] The filtering module is used to input the signal to be tested into a comb filter, filter out the harmonic components of each frequency, and obtain a processed signal;

[0073] A restoration module, used for inputting the processed signal into the improved undamped vector digital oscillator, restoring and extracting the harmonic signal corresponding to each frequency;

[0074] The extraction module is used to input the corresponding parameters into the harmonic signals of each frequency, adjust the amplitude and phase during the filtering process of the comb filter, ensure that the amplitude and gain of the harmonic signal spectrum are consistent, and complete the harmonic extraction.

[0075] Furthermore, the filtering module is specifically implemented by converting the signal to be measured x αβ(n) Transfer function H of the input to the comb filter c (z), H c (z) introducing a cluster of zero points to filter out the harmonics in the input signal α;

[0076] The transfer function H c (z), let x αβ (n) has a cluster of harmonic components h=mk+l, where m, l are integers, and m>0, k=0,±1,±2,…; H c (z) is expressed as:

[0077]

[0078] Where z is the complex variable in the z-transform, e j represents the rotation factor, e is a constant, j is a complex variable, and N is the number of samples.

[0079] Based on the same inventive concept, this embodiment also provides a computing device, including: one or more processors, one or more memories, and one or more programs, wherein the programs are stored in the memories and configured to be executed by the processors, and when the programs are loaded into the processors, the steps of the specified cluster harmonic extraction method described in any one of the above items are implemented.

[0080] Based on the same inventive concept, this embodiment also provides a computer-readable storage medium, which stores a computer program. The computer program includes program instructions, and when the program instructions are executed by a processor, the processor executes the steps of the specified cluster harmonic extraction method described in any one of the above items.

Claims

1. A method for extracting harmonics from a specified cluster, characterized in that: include: Obtain three-phase discrete signals to be measured in the power system; Convert the three-phase discrete signal to be measured into the signal to be measured in a two-phase stationary coordinate system; The signal to be tested is input into a comb filter to filter out the harmonic components of each frequency to obtain a processed signal; The processed signal is input into an improved undamped vector digital oscillator to restore and extract the harmonic signals corresponding to each frequency; The corresponding parameters are input into the harmonic signals of each frequency, and the amplitude and phase of the comb filter are adjusted during the filtering process to ensure that the amplitude and gain of the harmonic signal spectrum are consistent, thus completing the harmonic extraction.

2. The method for extracting harmonics from a designated cluster according to claim 1, characterized in that: The method of obtaining the three-phase discrete signal to be measured in the power system is specifically to use the voltage and current sensors to collect the continuous voltage and current signals in the power system at a frequency of N / T0, and obtain the abc three-phase discrete signal to be measured at the nth frequency in the system. abc (n), where N is the number of samples and T0 is the basic period of the current sensor.

3. The method for extracting harmonics from a designated cluster according to claim 1, characterized in that: The three-phase discrete signal to be measured is converted into the signal to be measured in the two-phase stationary coordinate system, specifically, the abc three-phase voltage and current signals are converted into the α-β coordinate system to obtain the signal to be measured x αβ (n), where the expression for converting the abc axis to the dq axis is:

4. The method for extracting harmonics from a designated cluster according to claim 1, characterized in that: The method of inputting the signal to be tested into a comb filter to filter out the harmonic components of each frequency to obtain a processed signal specifically includes: αβ (n) Transfer function H of the input to the comb filter c (z), H c (z) introducing a cluster of zero points to filter out the harmonics in the input signal to be measured to obtain a processed signal; Let x αβ (n) has a cluster of harmonic components h=mk+l, where m, l are integers, and m>0, k=0,±1,±2,…; H c (z) is expressed as: Where z is the complex variable in the z-transform, e j represents the rotation factor, e is a constant, j is a complex variable, and N is the number of samples.

5. The method for extracting harmonics from a designated cluster according to claim 4, characterized in that: The processed signal is input into the improved undamped vector digital oscillator to restore and extract the harmonic signal of the corresponding frequency. Specifically, the processed signal is input into the transfer function of the undamped vector digital oscillator. In the process, the poles at the harmonic frequencies of the corresponding frequencies are constructed, the zeros at the harmonic frequencies of the corresponding frequencies are eliminated, and the harmonic signals of the corresponding frequencies are extracted. The transfer function of the undamped vector digital oscillator is It is expressed as:

6. The method for extracting harmonics from a designated cluster according to claim 5, characterized in that: The corresponding parameters are input into the harmonic signals of each frequency, and the amplitude and phase of the comb filter are adjusted during the filtering process to ensure that the amplitude and gain of the harmonic signal spectrum are consistent. Specifically, the harmonic signal is input into the gain and phase adjustment coefficient γ k In the embodiment, the amplitude and phase of the comb filter output signal are adjusted to achieve unity gain and zero phase shift of the harmonic signal; The gamma k The solution is: Among them, []′ is the derivative of the filter transfer function, e -j is the negative rotation factor.

7. A specified cluster harmonic extraction system, characterized in that: include: An acquisition module is used to obtain three-phase discrete signals to be measured in the power system; A conversion module, used for converting a three-phase discrete signal to be measured into a signal to be measured in a two-phase stationary coordinate system; The filtering module is used to input the signal to be tested into a comb filter, filter out the harmonic components of each frequency, and obtain a processed signal; A restoration module, used for inputting the processed signal into the improved undamped vector digital oscillator, restoring and extracting the harmonic signal corresponding to each frequency; The extraction module is used to input the corresponding parameters into the harmonic signals of each frequency, adjust the amplitude and phase during the filtering process of the comb filter, ensure that the amplitude and gain of the harmonic signal spectrum are consistent, and complete the harmonic extraction.

8. The designated cluster harmonic extraction system according to claim 1, characterized in that: The filtering module specifically includes: αβ (n) Transfer function H of the input to the comb filter c (z), H c (z) introducing a cluster of zero points to filter out the harmonics in the input signal to be measured; The transfer function H c (z), let x αβ (n) has a cluster of harmonic components h=mk+l, where m, l are integers, and m>0, k=0,±1,±2,…; H c (z) is expressed as: Where z is the complex variable in the z-transform, e j represents the rotation factor, e is a constant, j is a complex variable, and N is the number of samples.

9. A computing device, characterized in that include: One or more processors, one or more memories, and one or more programs, wherein the programs are stored in the memories and configured to be executed by the processors, and when the programs are loaded into the processors, the steps of the designated cluster harmonic extraction method according to any one of claims 1 to 6 are implemented.

10. A storage medium, characterized in that: The storage medium stores a computer program, wherein the computer program includes program instructions, and when the program instructions are executed by a processor, the processor executes the steps of the designated cluster harmonic extraction method according to any one of claims 1 to 6.

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