Arbitrary harmonic detection method and device, and medium

Abstract

The invention belongs to the technical field of harmonic detection, and particularly relates to an arbitrary-order harmonic detection method and device and a medium. The method comprises the following steps: S1, acquiring an alpha-axis component and a beta-axis component of a to-be-detected electrical quantity under a two-phase static coordinate system; s2, inputting the alpha-axis component into a first SOGI of which the resonant frequency is a specified subharmonic frequency to obtain an in-phase component and an orthogonal component of the alpha-axis component of the specified subharmonic; inputting the beta-axis component into a second SOGI which is completely the same as the first SOGI to obtain an in-phase component and an orthogonal component of the beta-axis component of the specified subharmonic; and S3, performing positive and negative sequence component decoupling to obtain a positive sequence component and a negative sequence component of the alpha-axis component of the specified subharmonic and a positive sequence component and a negative sequence component of the beta-axis component of the specified subharmonic. The technical problem that in the prior art, when any subharmonic is detected, the positive sequence component and the negative sequence component of the specified subharmonic need to be detected independently, and consequently the system complexity is high is solved.

Description

Technical Field

[0001] This invention belongs to the field of harmonic detection technology, specifically relating to a method, apparatus, and medium for detecting arbitrary harmonics. Background Technology

[0002] With the development of electronic power systems, more and more nonlinear electronic loads are being connected to the power grid, leading to increasingly significant harmonic and reactive power problems. Currently, active power filters (APFs) are widely used in the field of power grid harmonic mitigation. Their basic principle is to detect the harmonic current of the target object and generate a compensation current with opposite phase and the same amplitude to cancel it out. Therefore, accurate detection of the harmonic current of the target object is a prerequisite for harmonic mitigation.

[0003] To improve the flexibility of harmonic compensation, the method of detecting specific harmonics of arbitrary order has been extensively studied. Using the method of detecting specific harmonics of arbitrary order, the specific harmonics with greater harm can be selected for compensation according to the APF capacity. In addition, when using a hybrid power filter that combines passive power filters and active power filters, the APF only needs to compensate for specific harmonic currents, which is not possible with the traditional method of detecting arbitrary order harmonics. Therefore, the method of detecting specific harmonics of arbitrary order must be adopted.

[0004] Currently, the detection method for specified arbitrary harmonics is mainly based on the instantaneous reactive power theory in the time domain. The positive and negative sequence components of the specified harmonics need to be detected separately, which increases the complexity of the system. Summary of the Invention

[0005] The purpose of this invention is to provide a method, apparatus, and medium for detecting arbitrary harmonics, in order to solve the technical problem in the prior art that it is necessary to separately detect the positive and negative sequence components of a specified harmonic when detecting arbitrary harmonics, which leads to high system complexity.

[0006] To solve the above-mentioned technical problems, the present invention provides a technical solution for an arbitrary harmonic detection method, which includes: an arbitrary harmonic detection method, comprising:

[0007] S1. Obtain the α-axis and β-axis components of the electrical quantity to be detected in a two-phase stationary coordinate system;

[0008] S2. Input the α-axis component into the first SOGI with a resonant frequency of a specified subharmonic frequency to obtain the in-phase and quadrature components of the α-axis component of the specified subharmonic.

[0009] The β-axis component is input into a second SOGI that is exactly the same as the first SOGI to obtain the in-phase and quadrature components of the β-axis component of the specified subharmonic.

[0010] S3. Based on S2, obtain the in-phase and quadrature components of the α-axis component of the specified harmonic, and the in-phase and quadrature components of the β-axis component of the specified harmonic. Decouple the positive and negative sequence components to obtain the positive and negative sequence components of the α-axis component of the specified harmonic, and the positive and negative sequence components of the β-axis component of the specified harmonic.

[0011] The beneficial effects of the above technical solution are as follows: Compared with the traditional method for detecting a specified harmonic based on instantaneous reactive power, this invention uses a dual second-order generalized integrator (DSOGI) for harmonic detection. The dual second-order generalized integrator not only achieves accurate detection of the specified harmonic, but also utilizes its two-phase orthogonality to decouple the positive and negative sequences of the specified harmonic, directly obtaining the positive and negative sequence components of the specified harmonic. The entire detection process only requires one Clark transform to achieve accurate detection of the specified harmonic and its positive and negative sequence decoupling, greatly reducing system complexity. This invention solves the technical problem in existing technologies where detecting any harmonic requires separate detection of the positive and negative sequence components of the specified harmonic, leading to high system complexity.

[0012] Further, S1 includes: processing the original three-phase electrical quantities through a cascaded notch filter and then performing Clark transformation to obtain the α-axis and β-axis components of the electrical quantities to be detected in a two-phase stationary coordinate system;

[0013] The center frequency of the notch filter in the cascaded structure is the frequency of the main subharmonic, excluding the specified subharmonic.

[0014] The beneficial effect is that by using a notch filter to filter out the main subharmonics other than the specified subharmonics, the subsequent dual second-order generalized integrator can use a higher bandwidth to achieve a faster response speed, thereby accelerating the response speed while ensuring detection accuracy.

[0015] Further, S1 includes: performing Clark transformation on the original three-phase electrical quantities, and then processing them through a cascaded notch filter to obtain the α-axis component and β-axis component of the electrical quantities to be detected in a two-phase stationary coordinate system;

[0016] The center frequency of the notch filter in the cascaded structure is the frequency of the main subharmonic, excluding the specified subharmonic.

[0017] The beneficial effect is that by using a notch filter to filter out the main subharmonics other than the specified subharmonics, the subsequent dual second-order generalized integrator can use a higher bandwidth to achieve a faster response speed, thereby accelerating the response speed while ensuring detection accuracy.

[0018] Furthermore, in S3, the positive-sequence and negative-sequence components of the α-axis component of the specified subharmonic, and the positive-sequence and negative-sequence components of the β-axis component of the specified subharmonic are obtained in the following manner:

[0019]

[0020] in, The positive sequence component of the α-axis component of a specified subharmonic; The positive sequence component of the β-axis component of the specified subharmonic; The negative-sequence component of the α-axis component of the specified subharmonic; The negative-order component of the β-axis component of the specified subharmonic; The in-phase component of the α-axis component of a specified subharmonic; The orthogonal component of the α-axis component of a specified subharmonic; The in-phase component of the β-axis component of the specified subharmonic; The orthogonal component of the β-axis component of the specified subharmonic.

[0021] Furthermore, the electrical quantity to be detected is current.

[0022] The present invention also provides a technical solution for an arbitrary harmonic detection device: an arbitrary harmonic detection device includes a processor, the processor being used to execute a computer program to implement the steps of the arbitrary harmonic detection method described below:

[0023] S1. Obtain the α-axis and β-axis components of the electrical quantity to be detected in a two-phase stationary coordinate system;

[0024] S2. Input the α-axis component into the first SOGI with a resonant frequency of a specified subharmonic frequency to obtain the in-phase and quadrature components of the α-axis component of the specified subharmonic.

[0025] The β-axis component is input into a second SOGI that is exactly the same as the first SOGI to obtain the in-phase and quadrature components of the β-axis component of the specified subharmonic.

[0026] S3. Based on S2, obtain the in-phase and quadrature components of the α-axis component of the specified harmonic, and the in-phase and quadrature components of the β-axis component of the specified harmonic. Decouple the positive and negative sequence components to obtain the positive and negative sequence components of the α-axis component of the specified harmonic, and the positive and negative sequence components of the β-axis component of the specified harmonic.

[0027] The beneficial effects of the above technical solution are as follows: The detection device of the present invention performs harmonic detection using a dual second-order generalized integrator (DSOGI). The dual second-order generalized integrator not only enables accurate detection of a specified harmonic, but also, utilizing its orthogonal two-phase characteristic, achieves positive and negative sequence decoupling of the specified harmonic, directly obtaining the positive and negative sequence components of the specified harmonic. The entire detection process only requires one Clark transform to achieve accurate detection of the specified harmonic and its positive and negative sequence decoupling, greatly reducing system complexity. The present invention solves the technical problem in the prior art where, when detecting any harmonic, it is necessary to separately detect the positive and negative sequence components of the specified harmonic, leading to high system complexity.

[0028] Further, S1 includes: processing the original three-phase electrical quantities through a cascaded notch filter and then performing Clark transformation to obtain the α-axis and β-axis components of the electrical quantities to be detected in a two-phase stationary coordinate system;

[0029] The center frequency of the notch filter in the cascaded structure is the frequency of the main subharmonic, excluding the specified subharmonic.

[0030] The beneficial effect is that by using a notch filter to filter out the main subharmonics other than the specified subharmonics, the subsequent dual second-order generalized integrator can use a higher bandwidth to achieve a faster response speed, thereby accelerating the response speed while ensuring detection accuracy.

[0031] Further, S1 includes: performing Clark transformation on the original three-phase electrical quantities, and then processing them through a cascaded notch filter to obtain the α-axis component and β-axis component of the electrical quantities to be detected in a two-phase stationary coordinate system;

[0032] The center frequency of the notch filter in the cascaded structure is the frequency of the main subharmonic, excluding the specified subharmonic.

[0033] The beneficial effect is that by using a notch filter to filter out the main subharmonics other than the specified subharmonics, the subsequent dual second-order generalized integrator can use a higher bandwidth to achieve a faster response speed, thereby accelerating the response speed while ensuring detection accuracy.

[0034] Furthermore, in S3, the positive-sequence and negative-sequence components of the α-axis component of the specified subharmonic, and the positive-sequence and negative-sequence components of the β-axis component of the specified subharmonic are obtained in the following manner:

[0035]

[0036] in, The positive sequence component of the α-axis component of a specified subharmonic; The positive sequence component of the β-axis component of the specified subharmonic; The negative-sequence component of the α-axis component of the specified subharmonic; The negative-order component of the β-axis component of the specified subharmonic; The in-phase component of the α-axis component of a specified subharmonic; The orthogonal component of the α-axis component of a specified subharmonic; The in-phase component of the β-axis component of the specified subharmonic; The orthogonal component of the β-axis component of the specified subharmonic.

[0037] Furthermore, the electrical quantity to be detected is current.

[0038] The present invention also provides a technical solution for a computer-readable storage medium: a computer-readable storage medium having a computer program stored internally, the computer program being executed by a processor to implement the steps of the arbitrary harmonic detection method described below:

[0039] S1. Obtain the α-axis and β-axis components of the electrical quantity to be detected in a two-phase stationary coordinate system;

[0040] S2. Input the α-axis component into the first SOGI with a resonant frequency of a specified subharmonic frequency to obtain the in-phase and quadrature components of the α-axis component of the specified subharmonic.

[0041] The β-axis component is input into a second SOGI that is exactly the same as the first SOGI to obtain the in-phase and quadrature components of the β-axis component of the specified subharmonic.

[0042] S3. Based on S2, obtain the in-phase and quadrature components of the α-axis component of the specified harmonic, and the in-phase and quadrature components of the β-axis component of the specified harmonic. Decouple the positive and negative sequence components to obtain the positive and negative sequence components of the α-axis component of the specified harmonic, and the positive and negative sequence components of the β-axis component of the specified harmonic.

[0043] The beneficial effects of the above technical solution are as follows: The computer within the storage medium of this invention implements a specified harmonic detection method that differs from the traditional method based on instantaneous reactive power. Harmonic detection is performed using a dual second-order generalized integrator (DSOGI). The dual second-order generalized integrator not only achieves accurate specified harmonic detection but also, utilizing its two-phase orthogonal characteristic, decouples the positive and negative sequences of the specified harmonic, directly obtaining the positive and negative sequence components of the specified harmonic. The entire detection process requires only one Clark transform to achieve accurate detection of the specified harmonic and its positive and negative sequence decoupling, greatly reducing system complexity. This invention solves the technical problem in existing technologies where detecting arbitrary harmonics requires separate detection of the positive and negative sequence components of the specified harmonic, leading to high system complexity.

[0044] Further, S1 includes: processing the original three-phase electrical quantities through a cascaded notch filter and then performing Clark transformation to obtain the α-axis and β-axis components of the electrical quantities to be detected in a two-phase stationary coordinate system;

[0045] The center frequency of the notch filter in the cascaded structure is the frequency of the main subharmonic, excluding the specified subharmonic.

[0046] The beneficial effect is that by using a notch filter to filter out the main subharmonics other than the specified subharmonics, the subsequent dual second-order generalized integrator can use a higher bandwidth to achieve a faster response speed, thereby accelerating the response speed while ensuring detection accuracy.

[0047] Further, S1 includes: performing Clark transformation on the original three-phase electrical quantities, and then processing them through a cascaded notch filter to obtain the α-axis component and β-axis component of the electrical quantities to be detected in a two-phase stationary coordinate system;

[0048] The center frequency of the notch filter in the cascaded structure is the frequency of the main subharmonic, excluding the specified subharmonic.

[0049] The beneficial effect is that by using a notch filter to filter out the main subharmonics other than the specified subharmonics, the subsequent dual second-order generalized integrator can use a higher bandwidth to achieve a faster response speed, thereby accelerating the response speed while ensuring detection accuracy.

[0050] Furthermore, in S3, the positive-sequence and negative-sequence components of the α-axis component of the specified subharmonic, and the positive-sequence and negative-sequence components of the β-axis component of the specified subharmonic are obtained in the following manner:

[0051]

[0052] in, The positive sequence component of the α-axis component of a specified subharmonic; The positive sequence component of the β-axis component of the specified subharmonic; The negative-sequence component of the α-axis component of the specified subharmonic; The negative-order component of the β-axis component of the specified subharmonic; The in-phase component of the α-axis component of a specified subharmonic; The orthogonal component of the α-axis component of a specified subharmonic; The in-phase component of the β-axis component of the specified subharmonic; The orthogonal component of the β-axis component of the specified subharmonic.

[0053] Furthermore, the electrical quantity to be detected is current. Attached Figure Description

[0054] Figure 1This is a block diagram of the principle of a second-order generalized integrator in an embodiment of the arbitrary harmonic detection method of the present invention.

[0055] Figure 2 Bode plot of a second-order generalized integrator in an embodiment of the arbitrary harmonic detection method of the present invention;

[0056] Figure 3 This invention provides an implementation of the arbitrary harmonic detection method based on the separation of positive and negative order of specified harmonic currents using DSOGI.

[0057] Figure 4 Bode diagram of a cascaded notch filter in an embodiment of the arbitrary harmonic detection method of the present invention;

[0058] Figure 5 This is a block diagram illustrating the separation of positive and negative sequence of specified harmonic currents based on NF-DSOGI in an embodiment of the arbitrary harmonic detection method of the present invention.

[0059] Figure 6a The load current waveform is shown in the embodiment of the arbitrary harmonic detection method of the present invention.

[0060] Figure 6b Spectral analysis of the load current waveform in an embodiment of the arbitrary harmonic detection method of the present invention;

[0061] Figure 7a The waveform of the fifth harmonic current detected by the DSOGI method when k=0.5 is shown in the embodiment of the arbitrary harmonic detection method of the present invention.

[0062] Figure 7b This is a spectral analysis of the fifth harmonic current waveform detected by the DSOGI method when k=0.5 in an embodiment of the arbitrary harmonic detection method of the present invention.

[0063] Figure 8a The waveform of the seventh harmonic current detected by the DSOGI method when k=0.5 is shown in the embodiment of the arbitrary harmonic detection method of the present invention.

[0064] Figure 8b This is a spectral analysis of the seventh harmonic current waveform detected by the DSOGI method when k=0.5 in an embodiment of the arbitrary harmonic detection method of the present invention.

[0065] Figure 9a The waveform of the fifth harmonic current detected by the DSOGI method when k=0.1 is shown in the embodiment of the arbitrary harmonic detection method of the present invention.

[0066] Figure 9b This is a spectral analysis of the fifth harmonic current waveform detected by the DSOGI method when k=0.1 in an embodiment of the arbitrary harmonic detection method of the present invention.

[0067] Figure 10a The waveform of the seventh harmonic current detected by the DSOGI method is shown when k=0.1 in the embodiment of the arbitrary harmonic detection method of the present invention.

[0068] Figure 10b This is a spectral analysis of the seventh harmonic current waveform detected by the DSOGI method when k=0.1 in an embodiment of the arbitrary harmonic detection method of the present invention.

[0069] Figure 11a The waveform of the fifth harmonic current detected by the NF-DSOGI method when k=0.5 is shown in the embodiment of the arbitrary harmonic detection method of the present invention.

[0070] Figure 11b Spectral analysis of the fifth harmonic current waveform detected by the NF-DSOGI method when k=0.5 in the embodiment of the arbitrary harmonic detection method of the present invention;

[0071] Figure 12a The waveform of the seventh harmonic current detected by the NF-DSOGI method when k=0.5 is shown in the embodiment of the arbitrary harmonic detection method of the present invention.

[0072] Figure 12b This is a spectral analysis of the seventh harmonic current waveform detected by the NF-DSOGI method when k=0.5 in the embodiment of the arbitrary harmonic detection method of the present invention. Detailed Implementation

[0073] Compared to traditional methods for detecting specified harmonics based on instantaneous reactive power, this invention utilizes dual second-order generalized integrators for harmonic detection. These integrators not only achieve accurate detection of specified harmonics but also, by leveraging their orthogonal two-phase characteristics, decouple the positive and negative sequences of the specified harmonic, directly obtaining the positive and negative sequence components. The entire detection process requires only one Clark transform to achieve accurate detection of the specified harmonic and its positive and negative sequence decoupling, significantly reducing system complexity. This invention solves the technical problem in existing technologies where detecting arbitrary harmonics requires separate detection of the positive and negative sequence components of the specified harmonic, leading to high system complexity.

[0074] Implementation method of arbitrary harmonic detection:

[0075] This embodiment uses current harmonic detection to describe the arbitrary harmonic detection method of the present invention in detail. In other embodiments, the arbitrary harmonic detection method of the present invention can be used to detect a specified harmonic voltage.

[0076] Precise harmonic compensation requires accurate detection of the specified harmonics. However, these specified harmonics may contain both positive and negative sequence components, necessitating separation of the positive and negative sequence harmonic currents for individual control to achieve better compensation. The three-phase unbalanced harmonic current can be expressed as:

[0077]

[0078] in, This refers to three-phase harmonic currents; and These are the positive-sequence and negative-sequence components of the harmonic current, respectively. and The transformation matrices are shown in the following equations:

[0079]

[0080] in, .

[0081] For three-phase harmonic current i Lhabc The harmonic current i in the α-β coordinate system can be obtained by performing the Clark transformation. αβ :

[0082]

[0083] in, , where represents the transformation matrix of the Clark transformation.

[0084] Therefore, the positive sequence component of the specified harmonic current in the two-phase stationary coordinate system can be obtained. and negative order components They are represented as follows:

[0085]

[0086] Where q represents a 90° phase lag in the time domain on the original signal; ; .

[0087] As can be seen from the above formula, in order to obtain the positive sequence component and the negative sequence component in the unbalanced specified harmonic current, it is necessary to obtain the correlation component that lags the input signal by 90°, so as to obtain the two-phase orthogonal current signal.

[0088] A second-order generalized integrator (SOGI), also known as a quadrature signal generator, can achieve a 90° phase shift in the input signal and also has adaptive filtering capabilities. Its system block diagram is shown below. Figure 1 As shown, by Figure 1 It can be seen that the closed-loop transfer function of SOGI is:

[0089]

[0090] in, k is the resonant frequency; k is the system gain; ; In phase with i(s), The lag i(s) is 90°; s is the Laplace operator.

[0091] Figure 2 Represents the resonant frequency The Bode plots of SOGI with different system gain k values ​​show that a larger k value results in a wider bandwidth but a worse filtering effect, although the response time is faster. Conversely, a smaller k value results in a narrower bandpass and a better filtering effect, but a slower response time. Therefore, for harmonics of different frequencies, a trade-off between filtering effect and response time needs to be considered.

[0092] The control block diagram for separating the positive and negative sequences of specified subharmonic currents based on DSOGI (Double-SOGI) is as follows: Figure 3 As shown, the original three-phase current i abc After Clark transformation to a two-phase stationary coordinate system, the α-axis component i is obtained. α and β-axis component i β Then, by utilizing the orthogonal characteristic of SOGI, two identical SOGIs (the first SOGI and the second SOGI) can be used to orthogonally split the input current signal, thus obtaining the in-phase component of the specified subharmonic. and Orthogonal components and The SOGI was designed to have a narrow bandwidth at a specified subharmonic frequency, enabling the extraction of harmonics at that frequency. This was achieved using the aforementioned... and The calculation formula can then be used to obtain the positive and negative sequence components of the specified harmonic current in a two-phase stationary coordinate system; that is:

[0093]

[0094] in, The positive sequence component of the α-axis component of a specified subharmonic; The positive sequence component of the β-axis component of the specified subharmonic; The negative-sequence component of the α-axis component of the specified subharmonic; The negative-order component of the β-axis component of the specified subharmonic; The in-phase component of the α-axis component of a specified subharmonic; The orthogonal component of the α-axis component of a specified subharmonic; The in-phase component of the β-axis component of the specified subharmonic; The orthogonal component of the β-axis component of the specified subharmonic.

[0095] However, while the arbitrary harmonic detection method based solely on DSOGI (hereinafter referred to as DSOGI) can achieve accurate detection of arbitrary harmonics, it is greatly affected by the bandwidth. When the k value is small, more accurate harmonic detection can be achieved, but it will significantly affect the response speed of harmonic detection, which in turn will affect the speed of harmonic compensation. When the k value is large, the bandwidth is large and the response speed of harmonic detection is fast, but the accuracy of harmonic detection is low, which will affect the effectiveness of harmonic compensation.

[0096] Based on the above problems, this embodiment proposes an arbitrary harmonic detection method based on notch filters and DSOGI, such as... Figure 5 As shown, a notch filter selectively removes the major subharmonics in the load current, retaining the harmonic components to be detected. Then, a harmonic detection method based on DSOGI is used to detect the specified subharmonics. The notch filter only affects specific subharmonics and does not affect the bandwidth selection of DSOGI, allowing DSOGI to select a higher bandwidth for faster response speed. Furthermore, the accuracy of harmonic detection is guaranteed, unaffected by interference from other subharmonics.

[0097] The transfer function NF(s) of the notch filter is:

[0098]

[0099] in, The damping coefficient is... The larger the value, the stronger the attenuation capability for a specific harmonic signal, and the smaller the impact on other harmonics; ω n The center frequency is the frequency of the specified subharmonic that needs to be filtered out.

[0100] This embodiment uses a cascaded notch filter. The test object in this embodiment is a three-phase uncontrolled rectifier load, whose main harmonic components are the 5th, 7th, 11th, and 13th harmonics. Therefore, the harmonic frequencies to be detected are removed, and the other three frequencies are used as the center frequencies of the cascaded notch filter.

[0101] Bode diagram of cascaded notch filter structure as shown in Figure Figure 4 As shown in the figure, different f0 values ​​represent the center frequencies of different notch filters. It can be seen that notch filters with a cascaded structure can achieve significant amplitude attenuation at specific harmonics, completely eliminating other major harmonics in the load current. Since the notch filter only operates at specific harmonic frequencies, it does not affect the system bandwidth.

[0102] The following example demonstrates the detection effect of the notch filter and DSOGI arbitrary harmonic detection method (hereinafter referred to as NF-DSOGI) provided in this embodiment by taking the detection of harmonic current of a three-phase uncontrolled rectifier load as an example.

[0103] like Figure 6a The diagram shows the three-phase current waveforms of the load when it is switched on. The switching on of the nonlinear R-type three-phase uncontrolled rectifier circuit causes distortion of the grid current. The spectrum analysis diagram of the load current is shown below. Figure 6b As shown, the harmonic current generated by a three-phase uncontrolled rectifier load theoretically only has fifth-order and seventh-order negative-sequence components. This is based on the load current spectrum analysis diagram (i.e., Figure 6b We can see that the amplitude of the fifth harmonic (frequency 250Hz) is 4.55 and the amplitude of the seventh harmonic (frequency 350Hz) is 2.27.

[0104] When k=0.5, the waveforms of the 5th negative sequence harmonic current and the 7th positive sequence harmonic current extracted using the DSOGI method are as follows: Figure 7a and Figure 8a As shown in the waveform diagram, the extracted harmonic current is severely distorted. Figure 7a and Figure 8a The corresponding spectrum analysis diagram is as follows Figure 7b and Figure 8b As shown, due to the large bandwidth, the amplitude of the fifth negative sequence harmonic current detected by the DSOGI method is 4.56 (4.55 in the original load current), and the amplitude of the seventh positive sequence harmonic current is 2.28 (2.27 in the original load current). The corresponding harmonic content is almost the same as the harmonic content in the original load current, indicating that the DSOGI method can achieve accurate detection of the specified harmonic. However, other harmonics still exist. This is because the bandwidth of DSOGI is large and cannot completely filter out other harmonics. Using this current waveform as the command value for the specified harmonic compensation will affect the effectiveness of the harmonic compensation.

[0105] When the bandwidth of DSOGI is reduced, harmonics of other frequencies can be almost completely filtered out, but this will significantly affect the response speed of harmonic detection, and thus affect the speed of the harmonic compensation device.

[0106] When k=0.1, the simulation results of the DSOGI method are as follows: Figure 9a , Figure 9b , Figure 10a and Figure 10b As shown, the harmonics of other frequencies in the extracted specified harmonic current are significantly suppressed, but the detection time (i.e. the time it takes for the current waveform in the figure to converge to a stable value) is significantly increased, as can be seen from the waveform of the specified harmonic current.

[0107] When k=0.5, the waveforms of the 5th negative sequence harmonic current and the 7th positive sequence harmonic current extracted using the NF-DSOGI method are as follows: Figure 11a and Figure 12a As shown, the amplitude of the fifth negative harmonic current is 4.55, and the amplitude of the seventh positive harmonic current is 2.27. The corresponding harmonic content is almost identical to the harmonic content in the original load current. Furthermore, this is consistent with the corresponding spectrum analysis diagram (…). Figure 11b and Figure 12b As can be seen, the NF-DSOGI method accurately extracts the specified harmonic current without including other harmonics, while ensuring the speed of harmonic detection.

[0108] Implementation method of arbitrary harmonic detection device:

[0109] An arbitrary harmonic detection device includes a processor, which executes a computer program to implement the steps of the arbitrary harmonic detection method described below. The specific arbitrary harmonic detection method has been described in sufficient detail in the above-described embodiments and will not be repeated here.

[0110] The control block diagram for separating the positive and negative sequences of specified subharmonic currents based on DSOGI (Double-SOGI) is as follows: Figure 3 As shown, the original three-phase current i abc After Clark transformation to a two-phase stationary coordinate system, the α-axis component i is obtained. α and β-axis component i β Then, by utilizing the orthogonal characteristic of SOGI, two identical SOGIs (the first SOGI and the second SOGI) can be used to orthogonally split the input current signal, thus obtaining the in-phase component of the specified subharmonic. and Orthogonal components and The SOGI was designed to have a narrow bandwidth at a specified subharmonic frequency, enabling the extraction of harmonics at that frequency. This was achieved using the aforementioned... and The calculation formula can be used to obtain the positive and negative sequence components of the specified harmonic current in a two-phase stationary coordinate system.

[0111] While the arbitrary harmonic detection method based solely on DSOGI (hereinafter referred to as DSOGI) can achieve accurate detection of arbitrary harmonics, it is greatly affected by bandwidth. When the value of k is small, more accurate harmonic detection can be achieved, but it will significantly affect the response speed of harmonic detection, which in turn will affect the speed of harmonic compensation. When the value of k is large, the bandwidth is large and the response speed of harmonic detection is fast, but the accuracy of harmonic detection is low, which will affect the effectiveness of harmonic compensation.

[0112] Therefore, as Figure 5 As shown, this invention selectively filters out the major subharmonics in the load current using a notch filter, retaining the harmonic components to be detected. Then, a harmonic detection method based on DSOGI is used to detect the specified subharmonics. The notch filter only affects specific subharmonics and does not affect the bandwidth selection of DSOGI, allowing DSOGI to select a higher bandwidth for faster response speed. Furthermore, the accuracy of harmonic detection is guaranteed and it is not affected by interference from other subharmonics.

[0113] Specifically, the processor can be a CPU, or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor can also be a processor supporting the Advanced Reduced Instruction Set Machine (ARM) architecture.

[0114] Implementation of computer-readable storage media:

[0115] A computer-readable storage medium stores a computer program internally, the computer program being executed by a processor to implement the steps of the arbitrary harmonic detection method as described above. The specific arbitrary harmonic detection method has been described in sufficient detail in the above-described embodiments and will not be repeated here.

[0116] The control block diagram for separating the positive and negative sequences of specified subharmonic currents based on DSOGI (Double-SOGI) is as follows: Figure 3 As shown, the original three-phase current i abc After Clark transformation to a two-phase stationary coordinate system, the α-axis component i is obtained. α and β-axis component i β Then, by utilizing the orthogonal characteristic of SOGI, two identical SOGIs (the first SOGI and the second SOGI) can be used to orthogonally split the input current signal, thus obtaining the in-phase component of the specified subharmonic. and Orthogonal components and The SOGI was designed to have a narrow bandwidth at a specified subharmonic frequency, enabling the extraction of harmonics at that frequency. This was achieved using the aforementioned... and The calculation formula can be used to obtain the positive and negative sequence components of the specified harmonic current in a two-phase stationary coordinate system.

[0117] While the arbitrary harmonic detection method based solely on DSOGI (hereinafter referred to as DSOGI) can achieve accurate detection of arbitrary harmonics, it is greatly affected by bandwidth. When the value of k is small, more accurate harmonic detection can be achieved, but it will significantly affect the response speed of harmonic detection, which in turn will affect the speed of harmonic compensation. When the value of k is large, the bandwidth is large and the response speed of harmonic detection is fast, but the accuracy of harmonic detection is low, which will affect the effectiveness of harmonic compensation.

[0118] Therefore, as Figure 5 As shown, this invention selectively filters out the major subharmonics in the load current using a notch filter, retaining the harmonic components to be detected. Then, a harmonic detection method based on DSOGI is used to detect the specified subharmonics. The notch filter only affects specific subharmonics and does not affect the bandwidth selection of DSOGI, allowing DSOGI to select a higher bandwidth for faster response speed. Furthermore, the accuracy of harmonic detection is guaranteed and it is not affected by interference from other subharmonics.

[0119] Specifically, the computer-readable storage medium can be volatile memory or non-volatile memory, or may include both. Non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. Volatile memory can be random access memory (RAM), which serves as an external cache. For example, Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDR SDRAM), Enhanced Synchronous DRAM (ESDRAM), SynchLink DRAM (SLDRAM), or Direct Rambus RAM (DRRAM).

[0120] This invention has the following characteristics:

[0121] This paper proposes a method for detecting specified harmonics based on a notch filter and a double second-order generalized integrator (DSOGI). When detecting specified harmonics, this method only requires Clark transformation of the detection current and processing of its α-β components to accurately detect the positive and negative sequence components of the specified harmonic. This method can automatically adapt to changes in the power grid frequency and has advantages such as high detection accuracy, strong robustness, and ease of implementation.

[0122] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make modifications to the technical solutions described in the foregoing embodiments without creative effort, or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An arbitrary sub-harmonic detection method, characterized by, The method comprises: S1, obtaining an α-axis component and a β-axis component of the to-be-detected electrical quantity in a two-phase stationary coordinate system; S2, inputting the α-axis component into a first SOGI with a resonant frequency of a specified harmonic frequency to obtain in-phase and quadrature components of the α-axis component of the specified harmonic; inputting the β-axis component into a second SOGI identical to the first SOGI to obtain in-phase and quadrature components of the β-axis component of the specified harmonic; S3, performing positive and negative sequence component decoupling on the in-phase and quadrature components of the α-axis component of the specified harmonic and the in-phase and quadrature components of the β-axis component of the specified harmonic obtained in S2 to obtain positive and negative sequence components of the α-axis component of the specified harmonic and positive and negative sequence components of the β-axis component of the specified harmonic.

2. The method of any harmonic detection according to claim 1, characterized in that, S1 comprises: After the original three-phase electrical quantity is processed by the notch filter with the cascade structure, Clark transformation is performed to obtain the α-axis component and the β-axis component of the to-be-detected electrical quantity in the two-phase stationary coordinate system; The center frequency of the notch filter with the cascade structure is the frequency of the main harmonic other than the specified harmonic.

3. The method of any harmonic detection according to claim 1, characterized in that, S1 comprises: After the original three-phase electrical quantity is processed by the notch filter with the cascade structure, Clark transformation is performed to obtain the α-axis component and the β-axis component of the to-be-detected electrical quantity in the two-phase stationary coordinate system; The center frequency of the notch filter with the cascade structure is the frequency of the main harmonic other than the specified harmonic.

4. The method of any one of claims 1 to 3, wherein, In S3, the positive and negative sequence components of the α-axis component of the specified harmonic and the positive and negative sequence components of the β-axis component of the specified harmonic are obtained in the following manner: ； wherein, is a positive sequence component of the alpha-axis component of the specified sub-harmonic; is a positive sequence component of the beta-axis component of the specified sub-harmonic; is a negative sequence component of the alpha-axis component of the specified sub-harmonic; is a negative sequence component of the beta-axis component of the specified sub-harmonic; is a positive component of the alpha-axis component of the specified sub-harmonic; is a positive component of the alpha-axis component of the specified sub-harmonic; is a positive component of the beta-axis component of the specified sub-harmonic; is a positive component of the beta-axis component of the specified sub-harmonic.

5. The method of any one of claims 1 to 3, wherein, The to-be-detected electrical quantity is current.

6. An arbitrary sub-harmonic detection apparatus comprising a processor, characterized in that, The processor is configured to execute a computer program to implement the steps of any harmonic detection method described as follows: S1, obtaining an α-axis component and a β-axis component of the to-be-detected electrical quantity in a two-phase stationary coordinate system; S2, inputting the α-axis component into a first SOGI with a resonant frequency of a specified harmonic frequency to obtain in-phase and quadrature components of the α-axis component of the specified harmonic; inputting the β-axis component into a second SOGI identical to the first SOGI to obtain in-phase and quadrature components of the β-axis component of the specified harmonic; S3, performing positive and negative sequence component decoupling on the in-phase and quadrature components of the α-axis component of the specified harmonic and the in-phase and quadrature components of the β-axis component of the specified harmonic obtained in S2 to obtain positive and negative sequence components of the α-axis component of the specified harmonic and positive and negative sequence components of the β-axis component of the specified harmonic.

7. The apparatus of claim 6, wherein, S1 comprises: After the original three-phase electrical quantity is processed by the notch filter with the cascade structure, Clark transformation is performed to obtain the α-axis component and the β-axis component of the to-be-detected electrical quantity in the two-phase stationary coordinate system; The center frequency of the notch filter with the cascade structure is the frequency of the main harmonic other than the specified harmonic.

8. The apparatus for any harmonic detection according to claim 6, wherein S1 comprises: After the original three-phase electrical quantity is processed by the notch filter with the cascade structure, Clark transformation is performed to obtain the α-axis component and the β-axis component of the to-be-detected electrical quantity in the two-phase stationary coordinate system; The center frequency of the notch filter with the cascade structure is the frequency of the main harmonic other than the specified harmonic.

9. The device of any one of claims 6 to 8, wherein the device is configured to detect the presence of the second harmonic signal by detecting the presence of the third harmonic signal. In S3, the positive-sequence component and the negative-sequence component of the α-axis component of the specified harmonic, and the positive-sequence component and the negative-sequence component of the β-axis component of the specified harmonic are obtained according to the following manner: ； wherein, is a positive sequence component of the alpha-axis component of the specified harmonic; is a positive sequence component of the beta-axis component of the specified harmonic; is a negative sequence component of the alpha-axis component of the specified harmonic; is a negative sequence component of the beta-axis component of the specified harmonic; is a positive sequence component of the alpha-axis component of the specified harmonic; is a positive sequence component of the alpha-axis component of the specified harmonic; is a positive sequence component of the beta-axis component of the specified harmonic; is a positive sequence component of the beta-axis component of the specified harmonic.

10. A computer readable storage medium, internally storing a computer program, characterized in that, The computer program is used for being executed by a processor to realize the steps of the arbitrary harmonic detection method as claimed in any one of claims 1~5.

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