Active power filter control method, system, device and medium based on double-cascaded time delay filter

Abstract

The application discloses a method, system, device and medium for controlling an active power filter based on a double-cascaded time delay filter, and belongs to the technical field of power quality treatment, which comprises the following steps: performing cascaded time delay filtering on grid-connected point voltage to obtain a voltage positive sequence component, and estimating a grid frequency according to the voltage positive sequence component; updating a time delay parameter of the cascaded time delay filtering according to the grid frequency, performing cascaded time delay filtering on a nonlinear load current to obtain a quadrature signal, and synthesizing the positive sequence component; removing the positive sequence component from the nonlinear load current to obtain a reference current, and controlling an active power filter to inject a compensation current. The application realizes frequency self-adaptation by inversely updating the filtering time delay parameter according to the grid frequency, and corrects the phase and the amplitude by means of a parallel running digital twin when the time delay parameter is tampered with, so that the extraction of the harmonic reference current remains accurate when the frequency fluctuates in a wide range and the parameter is tampered with.

Description

Technical Field

[0001] This invention relates to the field of power quality management technology, specifically to an active power filter control method, system, device, and medium based on a dual-cascaded time delay filter. Background Technology

[0002] Active power filters are devices used to mitigate harmonic pollution in power grids. They inject compensating current into the grid connection point to counteract harmonic currents injected into the grid by nonlinear loads, thus making the grid current more sinusoidal. The generation of the compensating current depends on the extraction of the harmonic reference current, that is, separating the fundamental positive-sequence component from the nonlinear load current and using the remaining part as the harmonic reference current.

[0003] In the process of extracting the harmonic reference current, it is necessary to estimate the frequency and phase of the grid connection point voltage, and based on this, perform coordinate transformation and determine the injection phase of the compensation current. The filtering stage for extracting the harmonic reference current, as well as the stage for estimating the frequency and phase, are usually implemented in discrete form in a digital processor, and their filtering characteristics are determined by a set of time delay parameters. Summary of the Invention

[0004] In view of the above-mentioned problems, the present invention provides an active power filter control method, system, device and medium based on a dual-cascaded time delay filter.

[0005] Therefore, the technical problem solved by this invention is: how to solve the problem that in scenarios with wide fluctuations in power grid frequency, the extraction method of harmonic reference current with fixed parameters is inaccurate due to the filter frequency point deviating from the drifted harmonic frequency, and that the filter delay parameter on which the harmonic reference current extraction depends cannot be detected or corrected when it is tampered with in the digital implementation.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an active power filter control method based on a dual-cascaded time delay filter, comprising, The grid connection point voltage is subjected to cascaded time-delay filtering to obtain the positive sequence voltage component, and the grid frequency is estimated from the positive sequence voltage component. The time delay parameters of the cascaded time delay filter are updated with the grid frequency. The nonlinear load current is then subjected to cascaded time delay filtering under the updated time delay parameters to obtain an orthogonal signal. The positive sequence component of the nonlinear load current is then synthesized from the orthogonal signal. The positive sequence component is removed from the nonlinear load current to obtain a reference current, and the active power filter is controlled to inject compensation current into the grid connection point according to the reference current.

[0007] As a preferred embodiment of the active power filter control method based on a dual-cascaded time delay filter described in this invention, wherein: the cascaded time delay filtering of the nonlinear load current includes: The nonlinear load current is subjected to two-stage time-delay notch processing, with the two-stage time-delay notch processing targeting different harmonic orders; The delay time of each stage of time-delay notch processing is determined according to the harmonic number it targets, and a notch is formed on the nonlinear load current at the target harmonic number.

[0008] As a preferred embodiment of the active power filter control method based on a dual-cascaded time delay filter described in this invention, the step of obtaining orthogonal signals and synthesizing the positive-sequence component of the nonlinear load current from the orthogonal signals includes: The orthogonal signal is formed by taking the signal after harmonic trapping by the cascaded time-delay filter and the delayed signal after harmonic trapping is delayed and has orthogonal phase. The orthogonal signal is subjected to a symmetric component transformation, and the component along the positive rotation direction is extracted from the orthogonal signal to obtain the positive sequence component.

[0009] As a preferred embodiment of the active power filter control method based on a dual-cascaded time delay filter described in this invention, the step of performing symmetrical component transformation on the orthogonal signal includes: In the symmetric component transformation, the two signals of the orthogonal signal are cross-coupled; The cross-coupling causes the components of the orthogonal signal along the positive rotation direction to be superimposed in phase and the components along the negative rotation direction to be canceled out of phase, thereby suppressing the negative component from the positive component.

[0010] As a preferred embodiment of the active power filter control method based on a dual-cascaded time delay filter described in this invention, wherein: the estimation of the grid frequency from the positive sequence voltage component includes: The grid frequency is estimated based on the positive sequence voltage component, and the phase angle of the positive sequence voltage component is determined. The compensation current is injected into the grid connection point according to the phase angle.

[0011] As a preferred embodiment of the active power filter control method based on a dual-cascaded time delay filter described in this invention, wherein: injecting the compensation current into the grid connection point according to the phase angle includes: Using a digital twin that operates in parallel with the cascaded time-delay filter applied to the nonlinear load current, the theoretical phase of the cascaded time-delay filter at the grid frequency is given based on the time delay parameters of the cascaded time-delay filter and the grid frequency. The phase angle is corrected by the phase deviation between the actual phase and the theoretical phase of the cascaded time-delay filter, and the compensation current is injected into the grid connection point according to the corrected phase angle.

[0012] As a preferred embodiment of the active power filter control method based on a dual-cascaded time delay filter described in this invention, the step of removing the positive-sequence component from the nonlinear load current to obtain the reference current includes: Using a digital twin that operates in parallel with the cascaded time-delay filter applied to the nonlinear load current, the theoretical gain of the cascaded time-delay filter at the grid frequency is given based on the time delay parameters of the cascaded time-delay filter and the grid frequency. The amplitude of the positive-sequence component is corrected using the theoretical gain, and the amplitude-corrected positive-sequence component is removed from the nonlinear load current to obtain the reference current.

[0013] This invention provides an active power filter control system based on a dual-cascaded time delay filter.

[0014] To solve the above technical problems, the present invention provides the following technical solution: an active power filter control system based on a dual-cascaded time delay filter, comprising: a frequency estimation unit, used to perform cascaded time delay filtering on the grid connection point voltage to obtain a positive sequence voltage component, estimate the grid frequency based on the positive sequence voltage component, determine the phase angle of the positive sequence voltage component, and update the time delay parameters of the cascaded time delay filter based on the grid frequency; A digital twin unit is used to provide the theoretical phase and theoretical gain of the cascaded time-delay filter applied to the nonlinear load current at the grid frequency, based on the updated time delay parameters and the grid frequency. A reference current generation unit is used to perform cascaded time-delay filtering on the nonlinear load current under the updated time delay parameters to obtain an orthogonal signal, synthesize the positive sequence component of the nonlinear load current from the orthogonal signal, correct the amplitude of the positive sequence component with the theoretical gain, and remove the amplitude-corrected positive sequence component from the nonlinear load current to obtain a reference current. The compensation control unit is used to correct the phase angle with the theoretical phase, receive the reference current, and control the active power filter to inject compensation current into the grid connection point according to the corrected phase angle.

[0015] The present invention provides a computer device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the active power filter control method based on a dual-cascaded time delay filter.

[0016] The present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the active power filter control method based on a dual-cascaded time delay filter.

[0017] The beneficial effects of the present invention are as follows: The present invention adopts a cascaded time-delay filter composed of basic building blocks in two cascades, so that the cascaded time-delay filter can remain stable under any delay and will not become unstable due to power grid frequency drift, thus avoiding the degradation of filtering performance in scenarios with wide fluctuations in power grid frequency.

[0018] This invention updates the filter delay parameters with the power grid frequency, so that the extraction of harmonic reference current can be adaptively adjusted with the fluctuation of the power grid frequency, the notch filter frequency follows the drifted harmonic frequency, and the extraction of harmonic reference current remains accurate when the power grid frequency fluctuates over a wide range.

[0019] This invention utilizes a digital twin that operates in parallel with a cascaded time-delay filter to detect deviations in phase and amplitude when the filter delay parameters are tampered with. It then corrects the phase and amplitude, ensuring that the phase and amplitude of the compensation current injected into the grid remain accurate even when tampered with, thus improving control security.

[0020] This invention uses a double-cascaded time-delay filter and symmetrical component transformation to suppress negative sequence components when there is an imbalance in the nonlinear load, so that the injected compensation current is opposite to the harmonic current, the grid current tends to be sinusoidal, and the unity power factor is maintained. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The above is a flowchart of an active power filter control method based on a dual-cascaded time delay filter, provided as an embodiment of the present invention.

[0023] Figure 2 This diagram illustrates an application scenario of an active power filter control method based on a dual-cascaded time delay filter, as provided in an embodiment of the present invention.

[0024] Figure 3 The diagram shows the positive-sequence component synthesis structure of an active power filter control method based on a dual-cascaded time delay filter, as provided in an embodiment of the present invention.

[0025] Figure 4The discrete structure diagram of the time-delay notch processing of the active power filter control method based on a dual-cascaded time delay filter provided in an embodiment of the present invention is shown.

[0026] Figure 5 The diagram shows a digital twin of an active power filter control method based on a dual-cascaded time delay filter, as provided in an embodiment of the present invention.

[0027] Figure 6 This is a controller structure diagram of an active power filter control method based on a dual-cascaded time delay filter, provided in an embodiment of the present invention. Detailed Implementation

[0028] To make the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0029] Example 1, referring to Figures 1-6 The following is an embodiment of the present invention, which provides an active power filter control method based on a dual-cascaded time delay filter, including: S1, perform cascaded time-delay filtering on the grid connection point voltage to obtain the positive sequence voltage component, and estimate the grid frequency from the positive sequence voltage component.

[0030] like Figure 2 As shown, the active power filter is connected in parallel to the grid connection point, which is connected to the power grid and the nonlinear load. The active power filter injects compensation current into the grid connection point.

[0031] In some embodiments, the cascaded time-delay filter is constructed by two cascaded basic building blocks, and the transfer function of the basic building blocks is: in, For harmonic elimination delay parameters, For phase shaping parameters, For amplitude compensation gain, These are variables in the complex frequency domain.

[0032] It should be noted that the basic building block achieves complete attenuation of specific harmonics by introducing a positive feedback loop and a delay term, and employs... The non-moving average filter uses This avoids the pole being located at the origin.

[0033] It is understood that the cascaded time-delay filter possesses delay-independent stability, which is obtained by analyzing the characteristic quasi-polynomial, which is: Furthermore, in When it is 0, Pick , The poles are located in the left half-plane; for all angular frequencies greater than 0... ,satisfy: because and All values ​​are greater than 0, the condition is always true, the cascaded time-delay filter is stable under any delay, and avoids performance degradation caused by frequency drift when the power grid frequency fluctuates from 400Hz to 800Hz in the multi-electric aircraft power grid.

[0034] Further, the cascaded time-delay filtering is applied to the grid connection point voltage to obtain the positive-sequence voltage component, which is represented in the αβ coordinate system as follows: in, , These are the two components of the positive-sequence voltage component in the αβ coordinate system. The magnitude of the positive sequence component of the voltage. The power grid frequency, Let t be the phase of the positive sequence component of the voltage, and t be time.

[0035] Further, the estimation of the power grid frequency from the positive sequence voltage component includes steps S11-S12.

[0036] S11, the grid frequency is estimated based on the positive sequence voltage component, and the phase angle of the positive sequence voltage component is determined.

[0037] In some embodiments, the grid frequency is estimated based on the positive sequence voltage component and its rate of change, and the estimated value of the grid frequency is: in, This is an estimated value for the power grid frequency. , They are respectively , Rate of change over time This is the estimated amplitude value of the positive sequence component of the voltage.

[0038] Further, the phase angle of the positive-sequence voltage component is determined based on the positive-sequence voltage component, and the estimated value of the phase angle is: in, This is an estimated value for the phase angle.

[0039] It is understood that the estimated value of the power grid frequency and the estimated value of the phase angle are smoothed by a low-pass filter to remain stable when the power grid frequency drifts.

[0040] It should be noted that, in the multi-electric aircraft power grid, when the power grid frequency switches from 400Hz to 800Hz, the process of estimating the power grid frequency and the phase angle based on the positive sequence voltage component tracks the change in the power grid frequency.

[0041] S12, inject the compensation current into the grid connection point according to the phase angle.

[0042] like Figure 6 As shown, it can be understood that the phase angle is the angle of coordinate transformation, and the compensation current is injected into the grid connection point according to the phase angle.

[0043] Further, injecting the compensation current into the grid connection point according to the phase angle includes steps S121-S122.

[0044] S121, using a digital twin that operates in parallel with the cascaded time-delay filter applied to the nonlinear load current, provides the theoretical phase of the cascaded time-delay filter at the grid frequency based on the time delay parameters of the cascaded time-delay filter and the grid frequency.

[0045] like Figure 5 As shown, in some embodiments, to prevent malicious manipulation of the delay parameters of the cascaded time-delay filter, a digital twin is set up to run in parallel with the cascaded time-delay filter applied to the nonlinear load current. The digital twin calculates the phase angle of the transfer function of the cascaded time-delay filter at the grid frequency based on the delay parameters of the cascaded time-delay filter and the grid frequency, thereby obtaining the theoretical phase.

[0046] Furthermore, the theoretical phase is expressed as ,in, The transfer function in the digital twin. The imaginary unit, This is an estimated value for the power grid frequency.

[0047] S122, the phase angle is corrected by the phase deviation between the actual phase and the theoretical phase of the cascaded time-delay filter, and the compensation current is injected into the grid connection point according to the corrected phase angle.

[0048] In some embodiments, the delay parameter includes a phase shaping parameter for adjusting the phase of the cascaded time-delay filter at the fundamental frequency. When the phase shaping parameter is maliciously manipulated and altered, the cascaded time-delay filter generates a phase shift, and the actual phase of the cascaded time-delay filter deviates from the theoretical phase.

[0049] Furthermore, the actual phase is represented as ,in, Let be the transfer function for the cascaded time-delay filter applied to the nonlinear load current. The phase deviation between the actual phase and the theoretical phase is expressed as: in, The phase deviation is used to correct the phase angle, and the corrected phase angle is: in, The phase angle is the one after correction. When the phase shaping parameters are not tampered with, the actual phase is consistent with the theoretical phase, and the phase deviation is 0; when the phase shaping parameters are tampered with, the phase deviation is not 0, and the phase angle is corrected.

[0050] It is understandable that the compensation current is injected into the grid connection point according to the phase angle after calibration, so that the phase of the compensation current injected into the grid connection point remains accurate when the phase shaping parameters are tampered with.

[0051] It should be noted that the digital twin output is a logic signal used to indicate whether the phase shaping parameters have been tampered with. When the actual phase is inconsistent with the theoretical phase, the logic signal This indicates that the phase shaping parameters have been tampered with.

[0052] It is understood that, through step S1, the grid frequency and the phase angle are estimated from the positive sequence component of the voltage, and the cascaded time-delay filter remains stable when the grid frequency fluctuates from 400Hz to 800Hz in the multi-electric aircraft grid.

[0053] S2, update the delay parameters of the cascaded time-delay filter with the grid frequency, perform cascaded time-delay filtering on the nonlinear load current under the updated delay parameters to obtain an orthogonal signal, and synthesize the positive sequence component of the nonlinear load current from the orthogonal signal.

[0054] In some embodiments, the basic building blocks are cascaded to form a cascaded time-delay filter for the nonlinear load current. The harmonic cancellation delay parameters, phase shaping parameters, and amplitude compensation gain of the basic building blocks are expanded in two stages. The harmonic cancellation delay parameters and phase shaping parameters of the first stage are as follows: , The second-stage harmonic cancellation delay parameters and phase shaping parameters are as follows: , The amplitude compensation gain shared by the two stages is .

[0055] Furthermore, the transfer function of the cascaded time-delay filter applied to the nonlinear load current is: Furthermore, the cascaded time-delay filtering of the nonlinear load current includes steps S21-S24.

[0056] S21, perform two-stage time-delay notch processing on the nonlinear load current, the two-stage time-delay notch processing are respectively for different harmonic orders.

[0057] In some embodiments, the first stage of the two-stage time-delay notch processing corresponds to the transfer function containing , The bracketed terms, the second-level time-delay notch processing corresponds to the transfer function containing... , The parenthetical items.

[0058] Furthermore, the two harmonic orders targeted by the two-stage time-delay notch processing can be designed. By designing the harmonic orders targeted by each of the two stages, the harmonics at the two targeted harmonic orders and their odd harmonics can be selectively suppressed.

[0059] For example, the two-stage time-delay notch processing is designed for different harmonic orders, such as the 3rd and 11th harmonics.

[0060] S22, the delay time of each stage of time-delay notch processing is determined according to the harmonic number it targets, and a notch is formed on the nonlinear load current at the target harmonic number.

[0061] In some embodiments, the delay duration of each stage of time-delay notch processing is determined by the harmonic cancellation delay parameter, wherein the harmonic cancellation delay parameter of the first stage of time-delay notch processing is... Harmonic cancellation delay parameters of the second-stage time-delay notch processing All are determined by the following formula: in, For each stage of time-delay notch processing, the harmonic elimination time delay parameter is provided. For each stage of time-delay notch processing, the harmonic order it targets. This is the fundamental frequency period.

[0062] For example, the harmonic cancellation delay parameter for the third harmonic. for .

[0063] Furthermore, the phase shaping parameter and the amplitude compensation gain are used to adjust the amplitude and phase of the cascaded time-delay filter at the fundamental frequency.

[0064] Understandably, using the third-order Padé approximation, the transfer function of the basic building block is: in, , , , , .

[0065] Furthermore, the phase shaping parameter causes the phase shift of the cascaded time-delay filter at the fundamental frequency to be... rad, the phase shaping parameter of the first-stage time-delay notch processing Phase shaping parameters of the second-stage time-delay notch processing All are determined by the following formula: in, For each stage of time-delay notch processing, the phase shaping parameters are... The power grid frequency, The cascaded time-delay filter causes the phase shift at the fundamental frequency to be... The phase-shaping target angle in rad.

[0066] Furthermore, the amplitude compensation gain ensures that the cascaded time-delay filter satisfies the following at the fundamental frequency: The amplitude compensation gain Determine by the following formula: in, The amplitude compensation gain is given.

[0067] S23, the signal after harmonic trapping by the cascaded time-delay filter and the delayed signal after the harmonic trapping signal are delayed and have orthogonal phases are taken together to form the orthogonal signal.

[0068] In some embodiments, the delayed signal is obtained by the harmonic-caught signal after... The delay was obtained, the The delay is represented as ,in, for The delay This is the fundamental frequency period.

[0069] Furthermore, the signal after harmonic trapping is processed by the... After the delay, the corresponding transfer function is: It is understandable that the signal after harmonic trapping corresponds to The delayed signal corresponds to The signal after harmonic removal and the delayed signal together constitute the orthogonal signal.

[0070] S24, perform symmetric component transformation on the orthogonal signal, extract the component along the positive rotation direction from the orthogonal signal, and obtain the positive sequence component.

[0071] like Figure 3 As shown, in some embodiments, the orthogonal signals are subjected to Clarke transform and symmetrical component transform to convert the three-phase currents into an αβ coordinate system. The positive sequence component is: in, , These are the two components of the positive-order component in the αβ coordinate system. , These are the two components of the nonlinear load current in the αβ coordinate system.

[0072] Furthermore, the extraction of the positive-order component is expressed by the following formula: in, The transfer function for extracting the positive-order components. for and A general term.

[0073] Furthermore, the symmetric component transformation of the orthogonal signal includes steps S241-S242.

[0074] S241, in the symmetric component transformation, the two signals of the orthogonal signal are cross-coupled.

[0075] In some embodiments, in the symmetric component transform, the two orthogonal signals are cross-coupled via a matrix of the symmetric component transform, wherein the diagonal elements of the matrix are... The off-diagonal elements of the matrix are and .

[0076] S242, the cross-coupling causes the components of the orthogonal signal along the positive rotation direction to be superimposed in phase and the components along the negative rotation direction to cancel each other out of phase, thereby suppressing the negative component from the positive component.

[0077] In some embodiments, when the nonlinear load current is unbalanced and contains a negative sequence component, the cross coupling causes the components of the orthogonal signal along the positive sequence rotation direction to be superimposed in phase and the components along the negative sequence rotation direction to cancel each other out of phase, thereby suppressing the negative sequence component from the positive sequence component.

[0078] Furthermore, the two-stage time-delay notch processing provides second-order attenuation for higher harmonics.

[0079] Furthermore, when the nonlinear load current is balanced, the symmetrical component transformation completely eliminates the zero-sequence harmonic and attenuates the non-third harmonic.

[0080] Furthermore, through the symmetrical component transformation, the negative-sequence component is suppressed from the positive-sequence component. The negative-sequence 5th harmonic is suppressed by the cross-coupling anti-phase cancellation, and the positive-sequence 7th harmonic is also suppressed, ensuring the sinusoidal nature of the grid current.

[0081] like Figure 4 As shown, in some embodiments, the cascaded time-delay filter is achieved through... The delay term in the cascaded time-delay filter is represented by the transformation and trapezoidal method approximation discretization. ,in, for Transformation operator, , The number of samples per cycle, The sampling period.

[0082] Furthermore, the discrete form of the basic building block is as follows: Furthermore, the aforementioned The delay discretization is ,in, .

[0083] It is understood that the delay parameter is updated based on an estimated value of the power grid frequency.

[0084] It is understood that, through step S2, the nonlinear load current is subjected to the cascaded time-delay filtering under the updated time delay parameters. The two-stage time-delay notch processing makes the notch frequency follow the changed harmonic frequency when the grid frequency fluctuates. The synthesized positive sequence component suppresses the negative sequence component when the nonlinear load current is unbalanced. The frequency adaptive response time of the grid frequency updating the time delay parameters is 8ms.

[0085] S3, remove the positive sequence component from the nonlinear load current to obtain a reference current, and control the active power filter to inject compensation current into the grid connection point according to the reference current.

[0086] In some embodiments, the positive-sequence component is removed from the nonlinear load current to obtain the reference current, wherein the reference current is: in, The reference current is... Let be the value of the nonlinear load current in the dq coordinate system. Let be the value of the positive-order component in the dq coordinate system.

[0087] Furthermore, the active power filter is controlled to inject the compensation current into the grid connection point according to the reference current. The compensation current is opposite to the harmonic current in the nonlinear load current, so that the grid current at the grid connection point is sinusoidal.

[0088] Further, the step of removing the positive sequence component from the nonlinear load current to obtain the reference current includes steps S31-S32.

[0089] S31, using a digital twin that operates in parallel with the cascaded time-delay filter applied to the nonlinear load current, provides the theoretical gain of the cascaded time-delay filter at the grid frequency based on the time delay parameters of the cascaded time-delay filter and the grid frequency.

[0090] In some embodiments, the digital twin calculates the transfer function amplitude of the cascaded time-delay filter at the power grid frequency based on the time delay parameters of the cascaded time-delay filter and the power grid frequency, thereby obtaining the theoretical gain.

[0091] Furthermore, the theoretical gain is expressed as ,in, Let be the transfer function of the cascaded time-delay filter applied to the nonlinear load current. This is an estimated value for the power grid frequency.

[0092] S32, the amplitude of the positive sequence component is corrected using the theoretical gain, and the amplitude-corrected positive sequence component is removed from the nonlinear load current to obtain the reference current.

[0093] In some embodiments, the time delay parameter includes the amplitude compensation gain, and when the amplitude compensation gain is maliciously manipulated and tampered with, the transfer function amplitude of the cascaded time delay filter deviates, causing the amplitude of the positive sequence component to deviate.

[0094] Furthermore, the amplitude of the positive-sequence component is corrected using the theoretical gain, and the amplitude-corrected positive-sequence component is: in, The positive-sequence component after amplitude correction. Let be the value of the positive-order component in the dq coordinate system.

[0095] It is understood that the reference current is obtained by removing the positive sequence component after amplitude correction from the nonlinear load current, so that the amplitude of the reference current remains accurate when the amplitude compensation gain is tampered with.

[0096] In some embodiments, for the purposes of the The delay parameter corresponding to the delay The digital twin, which has been tampered with, provides the following information: The theoretical orthogonal phase corresponding to the delay, in the delay parameter When the orthogonality of the orthogonal signal is tampered with, the orthogonal signal is corrected using the theoretical orthogonal phase.

[0097] Furthermore, the digital twin provides the following information based on the power grid frequency: The theoretical orthogonal phase corresponding to the delay, the theoretical orthogonal phase is expressed as... .

[0098] Furthermore, the orthogonal signal is corrected using the theoretically orthogonal phase, and the corrected orthogonal signal is: in, , The corrected orthogonal signal, , The orthogonal signal before correction. The delay parameter The orthogonal phase deviation caused by the alteration.

[0099] It is understood that the positive-sequence component is synthesized from the corrected orthogonal signals, such that the positive-sequence component is within the delay parameter. It maintains orthogonality when tampered with.

[0100] It should be noted that the digital twin output is used to indicate the delay parameter. Logic signal indicating whether it has been tampered with .

[0101] It is understood that by removing the positive sequence component from the nonlinear load current in step S3 to obtain the reference current, the compensation current injected by the active power filter is opposite to the harmonic current in the nonlinear load current, so that the total harmonic distortion rate of the grid current at the grid connection point is reduced to 1.01% in steady state, and the active power filter maintains unity power factor and reduces losses.

[0102] Example 2 is an embodiment of the present invention, which provides an active power filter control system based on a dual-cascaded time delay filter, including: The frequency estimation unit is used to perform cascaded time-delay filtering on the grid connection point voltage to obtain the positive sequence voltage component, estimate the grid frequency based on the positive sequence voltage component, determine the phase angle of the positive sequence voltage component, and update the time delay parameters of the cascaded time-delay filtering based on the grid frequency. A digital twin unit is used to provide the theoretical phase and theoretical gain of the cascaded time-delay filter applied to the nonlinear load current at the grid frequency, based on the updated time delay parameters and the grid frequency. A reference current generation unit is used to perform cascaded time-delay filtering on the nonlinear load current under the updated time delay parameters to obtain an orthogonal signal, synthesize the positive sequence component of the nonlinear load current from the orthogonal signal, correct the amplitude of the positive sequence component with the theoretical gain, and remove the amplitude-corrected positive sequence component from the nonlinear load current to obtain a reference current. The compensation control unit is used to correct the phase angle with the theoretical phase, receive the reference current, and control the active power filter to inject compensation current into the grid connection point according to the corrected phase angle.

[0103] This embodiment also provides an electronic device applicable to the active power filter control method based on a dual-cascaded time delay filter, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the active power filter control method based on a dual-cascaded time delay filter as proposed in the above embodiment.

[0104] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements the active power filter control method based on a dual-cascaded time delay filter as proposed in the above embodiments.

[0105] The storage medium proposed in this embodiment and the active power filter control method based on dual-cascaded time delay filters proposed in the above embodiments belong to the same inventive concept. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0106] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0107] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An active power filter control method based on a dual-cascaded time delay filter, characterized in that, include: The grid connection point voltage is subjected to cascaded time-delay filtering to obtain the positive sequence voltage component, and the grid frequency is estimated from the positive sequence voltage component. The time delay parameters of the cascaded time delay filter are updated with the grid frequency. The nonlinear load current is then subjected to cascaded time delay filtering under the updated time delay parameters to obtain an orthogonal signal. The positive sequence component of the nonlinear load current is then synthesized from the orthogonal signal. The positive sequence component is removed from the nonlinear load current to obtain a reference current, and the active power filter is controlled to inject compensation current into the grid connection point according to the reference current.

2. The active power filter control method based on a dual-cascaded time delay filter as described in claim 1, characterized in that, The cascaded time-delay filtering of the nonlinear load current includes: The nonlinear load current is subjected to two-stage time-delay notch processing, with the two-stage time-delay notch processing targeting different harmonic orders; The delay time of each stage of time-delay notch processing is determined according to the harmonic number it targets, and a notch is formed on the nonlinear load current at the target harmonic number.

3. The active power filter control method based on a dual-cascaded time delay filter as described in claim 2, characterized in that, The process of obtaining orthogonal signals and synthesizing the positive-sequence component of the nonlinear load current from the orthogonal signals includes: The orthogonal signal is formed by taking the signal after harmonic trapping by the cascaded time-delay filter and the delayed signal after harmonic trapping is delayed and has orthogonal phase. The orthogonal signal is subjected to a symmetric component transformation, and the component along the positive rotation direction is extracted from the orthogonal signal to obtain the positive sequence component.

4. The active power filter control method based on a dual-cascaded time delay filter as described in claim 3, characterized in that, The symmetric component transformation of the orthogonal signals includes: In the symmetric component transformation, the two signals of the orthogonal signal are cross-coupled; The cross-coupling causes the components of the orthogonal signal along the positive rotation direction to be superimposed in phase and the components along the negative rotation direction to be canceled out of phase, thereby suppressing the negative component from the positive component.

5. The active power filter control method based on a dual-cascaded time delay filter as described in claim 4, characterized in that, The estimation of the power grid frequency from the positive sequence voltage component includes: The grid frequency is estimated based on the positive sequence voltage component, and the phase angle of the positive sequence voltage component is determined. The compensation current is injected into the grid connection point according to the phase angle.

6. The active power filter control method based on a dual-cascaded time delay filter as described in claim 5, characterized in that, Injecting the compensation current into the grid connection point according to the phase angle includes: Using a digital twin that operates in parallel with the cascaded time-delay filter applied to the nonlinear load current, the theoretical phase of the cascaded time-delay filter at the grid frequency is given based on the time delay parameters of the cascaded time-delay filter and the grid frequency. The phase angle is corrected by the phase deviation between the actual phase and the theoretical phase of the cascaded time-delay filter, and the compensation current is injected into the grid connection point according to the corrected phase angle.

7. The active power filter control method based on a dual-cascaded time delay filter as described in claim 5, characterized in that, The step of removing the positive-sequence component from the nonlinear load current to obtain the reference current includes: Using a digital twin that operates in parallel with the cascaded time-delay filter applied to the nonlinear load current, the theoretical gain of the cascaded time-delay filter at the grid frequency is given based on the time delay parameters of the cascaded time-delay filter and the grid frequency. The amplitude of the positive-sequence component is corrected using the theoretical gain, and the amplitude-corrected positive-sequence component is removed from the nonlinear load current to obtain the reference current.

8. An active power filter control system based on a dual-cascaded time delay filter, employing the active power filter control method based on a dual-cascaded time delay filter as described in any one of claims 1 to 7, characterized in that, include: The frequency estimation unit is used to perform cascaded time-delay filtering on the grid connection point voltage to obtain the positive sequence voltage component, estimate the grid frequency based on the positive sequence voltage component, determine the phase angle of the positive sequence voltage component, and update the time delay parameters of the cascaded time-delay filtering based on the grid frequency. A digital twin unit is used to provide the theoretical phase and theoretical gain of the cascaded time-delay filter applied to the nonlinear load current at the grid frequency, based on the updated time delay parameters and the grid frequency. A reference current generation unit is used to perform cascaded time-delay filtering on the nonlinear load current under the updated time delay parameters to obtain an orthogonal signal, synthesize the positive sequence component of the nonlinear load current from the orthogonal signal, correct the amplitude of the positive sequence component with the theoretical gain, and remove the amplitude-corrected positive sequence component from the nonlinear load current to obtain a reference current. The compensation control unit is used to correct the phase angle with the theoretical phase, receive the reference current, and control the active power filter to inject compensation current into the grid connection point according to the corrected phase angle.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the active power filter control method based on a dual-cascaded time delay filter as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the active power filter control method based on a dual-cascaded time delay filter as described in any one of claims 1 to 7.

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