CN113258555A - Harmonic resonance suppression method and system for flexible direct current transmission system - Google Patents

Harmonic resonance suppression method and system for flexible direct current transmission system Download PDF

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CN113258555A
CN113258555A CN202110634165.4A CN202110634165A CN113258555A CN 113258555 A CN113258555 A CN 113258555A CN 202110634165 A CN202110634165 A CN 202110634165A CN 113258555 A CN113258555 A CN 113258555A
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resonance
phase
information
current
harmonic
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CN113258555B (en
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伍双喜
杨银国
谢小荣
满方九
刘洋
向丽玲
陆秋瑜
于珍
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Guangdong Power Grid Co Ltd
Electric Power Dispatch Control Center of Guangdong Power Grid Co Ltd
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Guangdong Power Grid Co Ltd
Electric Power Dispatch Control Center of Guangdong Power Grid Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/02—Arrangements for reducing harmonics or ripples
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

The invention discloses a harmonic resonance suppression method and system for a flexible direct current transmission system, and relates to the technical field of power systems. The method comprises the following steps: acquiring three-phase current signals and sending the three-phase current signals to an analog-to-digital converter to obtain current digital signals; carrying out Hanning windowed Fourier transform processing on the current digital signal to obtain resonance information; constructing ideal same-frequency positive sequence three-phase voltage according to the resonance information; performing phase locking processing on the same-frequency positive sequence three-phase voltage to obtain a phase locking result; performing proportional integral control on specific harmonic components of the current digital signal based on a phase locking result to obtain a primary voltage reference value; and superposing the preliminary voltage reference value and a voltage reference value generated by the current inner ring to obtain a final voltage reference value. The method comprises the steps of firstly determining resonance mode information through broadband resonance detection, and then correcting harmonic current control according to the resonance mode information to form a set of complete closed-loop control strategy; the problem of inhibition failure caused by the change of the system operation mode in the existing inhibition method is solved.

Description

Harmonic resonance suppression method and system for flexible direct current transmission system
Technical Field
The invention relates to the technical field of power systems, in particular to a harmonic resonance suppression method and system for a flexible direct current transmission system.
Background
The modular multilevel converter is widely applied to remote transmission and asynchronous interconnection of a power grid by virtue of the advantages of modular structure, control flexibility, high power quality and the like; at present, the Luxi back-to-back asynchronous networking engineering, the Yubei DC back-to-back networking engineering and the like in China all adopt a flexible DC power transmission technology based on a modular multilevel converter. The stability problem in flexible dc systems has occurred mostly in the low frequency and sub/super synchronous bands, but in recent years, there have been many practical high frequency resonance events, with resonance frequencies up to several kilohertz. High frequency resonance events can cause accidents such as trip of the flexible straight unit, shutdown of the system and the like. The stability problem of the flexible direct current transmission system has been developed to be a broadband resonance problem involving several hertz to several kilohertz, and if the resonance is not suppressed in time, the power transmission is interrupted, which seriously threatens the safe and stable operation of the power system, and needs to be solved urgently.
The broadband resonance problem in the soft direct current converter is completely different from the high-frequency harmonic caused by the pulse width modulation of high switching frequency in the traditional two-level and three-level current converters; the high-frequency resonance of the soft direct current system is LC electric resonance formed by the ground capacitance of an alternating current circuit and the inductance characteristic of the soft direct current converter, and the negative resistance effect caused by the control of the soft direct current converter generates an amplification effect on the resonance mode. The existing research shows that the main influence link of the high-frequency impedance characteristic of the flexible-direct current converter is current inner loop control, and the delay link causes the phase-frequency characteristic of the MMC to intermittently exceed 90 degrees under high frequency, so that the MMC has a negative resistance characteristic.
In the prior art, system impedance changes continuously with changes of system operation modes (such as alternating current network topology, power grid strength and the like), so that the flexible direct current broadband resonance is wide in frequency range, the frequency difference of different resonance events in the same system can even reach hundreds of hertz, and a suppression method designed according to a specific resonance event is difficult to solve the problem of broadband resonance of an actual flexible direct current transmission system.
Disclosure of Invention
The invention aims to provide a harmonic resonance suppression method and a harmonic resonance suppression system for a flexible direct current transmission system, so as to achieve the effect of suppressing specific harmonic components on the basis of not influencing the original dynamic response of a power system.
In order to achieve the above object, an embodiment of the present invention provides a harmonic resonance suppression method for a flexible direct current transmission system, including:
acquiring a three-phase current signal at an outlet of the current converter and sending the three-phase current signal to the analog-to-digital converter to obtain a current digital signal;
carrying out Hanning windowed Fourier transform processing on the current digital signal to obtain resonance information; wherein the resonance information comprises frequency information, phase sequence information and amplitude information;
constructing ideal same-frequency positive sequence three-phase voltage according to the resonance information;
performing phase locking processing on the same-frequency positive sequence three-phase voltage to obtain a phase locking result;
performing proportional integral control on specific harmonic components of the current digital signal based on the phase locking result to obtain a preliminary voltage reference value;
and superposing the preliminary voltage reference value and a voltage reference value generated by the current inner ring to obtain a final voltage reference value.
Preferably, the performing hanning windowed fourier transform processing on the current digital signal to obtain resonance information includes:
carrying out Hanning windowed Fourier transform processing on the current digital signal to obtain preliminary resonance information;
and optimizing the initial resonance information through an interpolation algorithm to obtain more accurate resonance information.
Preferably, the performing hanning windowed fourier transform processing on the current digital signal to obtain resonance information includes:
performing Hanning windowing on the current digital signal and then performing discrete Fourier transform to obtain a frequency spectrum analysis result;
carrying out resonance mode division on the frequency spectrum analysis result by a symmetric component method; wherein the resonant modes include a positive sequence resonant mode and a negative sequence resonant mode;
screening a spectrum analysis result with the maximum amplitude value from spectrum analysis results divided into the positive sequence resonance modes as a potential resonance mode;
correcting resonance mode parameters according to the spectrum analysis result of the potential resonance mode and a plurality of spectrum analysis results at the front spectral line and the rear spectral line of the potential resonance mode to obtain more accurate resonance information; the resonant mode parameters include frequency and amplitude.
Preferably, the current digital signal is subjected to hanning windowed fourier transform processing, using the expression:
Figure RE-GDA0003150177510000031
Hann[n]＝0.5-0.5cos[2nπ/(N-1)]，n＝0，1，...，N-1
wherein j is a, b, c; i is a current digital signal; n is the window length, and N is the current data number in the window length; i isjIs the result of the frequency spectrum analysis; k is a spectral line number corresponding to the spectral analysis; frequency of kfs/N； fsThe sampling frequency at the time of measurement, N is the window length.
Preferably, the spectrum analysis result is divided into resonance modes by a symmetric component method, and the used expression is as follows:
Figure RE-GDA0003150177510000032
Figure RE-GDA0003150177510000033
wherein j is a, b, c; i isjIs the result of the frequency spectrum analysis; k is the number of the spectral line corresponding to the spectral analysis, and the frequency is kfsN; p is a positive sequence component; n is a negative sequence component.
Preferably, the resonance mode parameters are corrected according to the spectrum analysis results of the potential resonance mode and a plurality of spectrum analysis results at the spectral lines before and after the potential resonance mode, and the expression used is as follows:
Figure RE-GDA0003150177510000034
Figure RE-GDA0003150177510000035
wherein A isHFRThe amplitude of the resonant mode; f. ofHFRA frequency that is a resonant mode; INT is an integer function; m is a spectral line number corresponding to the spectral analysis result with the maximum amplitude; fm]Is the frequency of the result of the spectral analysis; am (A m)]Is the amplitude of the spectral analysis result; delta is a correction factor。
Preferably, the resonance information needs to satisfy that the amplitude information of the resonance mode is greater than 2% -5% of the amplitude information of the positive-sequence fundamental wave.
Preferably, the phase-locking processing the same-frequency positive-sequence three-phase voltage to obtain a phase-locked result includes:
performing phase locking operation on the components of the same-frequency positive-sequence three-phase voltage by using a phase-locked loop to obtain a phase angle;
according to the phase sequence of the resonance information, determining whether to perform an inversion operation on the phase angle to obtain the actually required phase angle of park transformation, wherein the used expression is as follows:
Figure RE-GDA0003150177510000041
wherein S isHFR1 represents that the phase sequence is positive; sHFR-1 represents a negative sequence;
and obtaining a phase locking result according to the phase angle of the park transformation.
Preferably, the performing proportional integral control on a specific harmonic component of the current digital signal based on the phase locking result to obtain a preliminary voltage reference value includes:
performing park transformation on the current digital signal based on the phase locking result, and converting a resonance component of the current digital signal into a first component and a second component;
and performing proportional integral control on the first component and the second component, and performing inverse park transformation to obtain a preliminary voltage reference value.
The embodiment of the invention also provides a harmonic resonance suppression system of the flexible direct-current power transmission system, which comprises a broadband resonance detection module, a resonance component phase-locking module and a harmonic current control module;
the broadband resonance detection module comprises:
the signal acquisition module is used for acquiring a three-phase current signal at the outlet of the current converter and sending the three-phase current signal to the analog-to-digital converter to obtain a current digital signal;
the resonance information acquisition module is used for carrying out Hanning windowed Fourier transform processing on the current digital signal to obtain resonance information; wherein the resonance information comprises frequency information, phase sequence information and amplitude information;
the screening correction module is used for constructing ideal same-frequency positive sequence three-phase voltage according to the resonance information;
the resonant component phase-locking module is used for performing phase-locking processing on the same-frequency positive sequence three-phase voltage to obtain a phase-locking result;
the harmonic current control module includes:
the proportional integral module is used for carrying out proportional integral control on the specific harmonic component of the current digital signal based on the phase locking result to obtain a preliminary voltage reference value;
and the superposition module is used for superposing the preliminary voltage reference value and a voltage reference value generated by the current inner ring to obtain a final voltage reference value.
Preferably, the resonance information acquisition module includes:
the primary processing unit is used for carrying out Hanning windowed Fourier transform processing on the current digital signal to obtain primary resonance information;
and the optimization processing unit is used for optimizing the initial resonance information through an interpolation algorithm to obtain more accurate resonance information.
Preferably, the resonance information acquisition module includes:
the windowing unit is used for performing Hanning windowing on the current digital signal and then performing discrete Fourier transform to obtain a frequency spectrum analysis result;
the mode screening unit is used for carrying out resonance mode division on the frequency spectrum analysis result through a symmetric component method; wherein the resonant modes include a positive sequence resonant mode and a negative sequence resonant mode;
the mode screening unit is further used for screening a spectrum analysis result with the largest amplitude value from the spectrum analysis results divided into the positive sequence resonance modes as a potential resonance mode;
the correction unit corrects the resonance mode parameters according to the spectrum analysis result of the potential resonance mode and a plurality of spectrum analysis results at the front spectral line and the rear spectral line of the potential resonance mode to obtain more accurate resonance information; the resonant mode parameters include frequency and amplitude.
Preferably, the resonance component phase-locked module includes:
the phase angle acquisition module is used for carrying out phase locking operation on the components of the same-frequency positive sequence three-phase voltage by using a phase-locked loop to obtain a phase angle;
the negation module is used for determining whether to perform negation operation on the phase angle according to the phase sequence of the resonance information so as to obtain the actually required phase angle of park transformation, and the used expression is as follows:
Figure RE-GDA0003150177510000061
wherein S isHFR1 represents that the phase sequence is positive; sHFR-1 represents a negative sequence;
and the phase locking result acquisition module is used for acquiring a phase locking result according to the phase angle of the park transformation.
Preferably, the proportional-integral module comprises:
the park transformation unit is used for carrying out park transformation on the current digital signal based on the phase locking result and converting a resonance component of the current digital signal into a first component and a second component;
and the park inverse transformation unit is used for carrying out proportional integral control on the first component and the second component and then carrying out park inverse transformation to obtain a preliminary voltage reference value.
The embodiment of the invention also provides computer terminal equipment which comprises one or more processors and a memory. A memory coupled to the processor for storing one or more programs; when executed by the one or more processors, the one or more programs cause the one or more processors to implement the harmonic resonance suppression method for a flexible direct current transmission system according to any of the embodiments.
Embodiments of the present invention further provide a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements the harmonic resonance suppression method for a flexible direct current power transmission system according to any of the above embodiments.
Compared with the prior art, the invention has the following beneficial effects:
the invention combines the broadband resonance detection and the harmonic current control to form a set of complete closed-loop control strategy. The broadband resonance detection takes three-phase current signals at the outlet of the current converter as input, finally outputs frequency, phase sequence and amplitude information of the resonance mode, and combines a symmetric component method and Hanning windowed interpolation to realize quick and accurate detection of the positive and negative sequence resonance mode.
The invention constructs ideal same-frequency positive sequence three-phase voltage according to the detected resonant frequency, and realizes the phase locking of the resonant mode under different conditions by locking the voltage.
The invention carries out proportional integral control on specific harmonic components based on phase locking results through harmonic current control, and the obtained voltage reference value is superposed with the voltage reference value generated by the original current inner loop to form the final voltage reference value. The harmonic current control can achieve the effect of inhibiting specific harmonic components on the basis of not influencing the original dynamic response of the system.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a harmonic resonance suppression method of a flexible direct current transmission system according to a first embodiment of the present invention;
fig. 2 is a schematic flow chart of a harmonic resonance suppression method of a flexible direct current transmission system according to a second embodiment of the present invention;
fig. 3 is a schematic flow chart of a harmonic resonance suppression method of a flexible direct current transmission system according to a third embodiment of the present invention;
fig. 4 is a schematic flow chart of a harmonic resonance suppression method of a flexible direct current transmission system according to a fourth embodiment of the present invention;
fig. 5 is a schematic flow chart of a harmonic resonance suppression method of a flexible direct current transmission system according to a fifth embodiment of the present invention;
fig. 6 is a schematic structural diagram of a harmonic resonance suppression system of a flexible direct current transmission system according to a sixth embodiment of the present invention;
fig. 7 is a schematic structural diagram of a harmonic resonance suppression system of a flexible direct current transmission system according to a seventh embodiment of the present invention;
fig. 8 is a schematic structural diagram of a harmonic resonance suppression system of a flexible direct current transmission system according to an eighth embodiment of the present invention;
fig. 9 is a schematic diagram of a harmonic resonance suppression method and system for a flexible dc power transmission system according to a ninth embodiment of the present invention;
fig. 10 is a schematic structural diagram of a computer terminal device according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be understood that the step numbers used herein are for convenience of description only and are not intended as limitations on the order in which the steps are performed.
It is to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The terms "comprises" and "comprising" indicate the presence of the described features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
The term "and/or" refers to and includes any and all possible combinations of one or more of the associated listed items.
The invention aims to research the stability of a power system, particularly inhibit the resonance of a flexible direct-current transmission system, firstly, determining resonance mode information through broadband resonance detection, and then correcting harmonic current control according to the resonance mode information to form a set of complete closed-loop control strategy; the inhibition failure caused by the change of the system operation mode in the existing inhibition method is avoided.
Referring to fig. 1, fig. 1 is a schematic flow chart illustrating a harmonic resonance suppression method of a flexible direct current transmission system according to a first embodiment of the present invention. The harmonic resonance suppression method for the flexible direct current transmission system provided by the embodiment comprises the following steps:
s110, acquiring a three-phase current signal at an outlet of the current converter and sending the three-phase current signal to the analog-to-digital converter to obtain a current digital signal;
s120, carrying out Hanning windowed Fourier transform processing on the current digital signal to obtain resonance information; the resonance information comprises frequency information, phase sequence information and amplitude information;
s130, constructing ideal same-frequency positive sequence three-phase voltage according to the resonance information;
s140, performing phase locking processing on the same-frequency positive sequence three-phase voltage to obtain a phase locking result;
s150, performing proportional integral control on the specific harmonic component of the current digital signal based on the phase locking result to obtain a primary voltage reference value;
and S160, superposing the preliminary voltage reference value and the voltage reference value generated by the current inner ring to obtain a final voltage reference value.
Referring to fig. 2, fig. 2 is a flowchart illustrating a harmonic resonance suppression method for a flexible dc power transmission system according to a second embodiment of the present invention. In this embodiment, the step S120 of performing hanning windowed fourier transform processing on the current digital signal to obtain resonance information includes the following steps:
s1210, carrying out Hanning windowed Fourier transform processing on the current digital signal to obtain preliminary resonance information;
and S1211, optimizing the preliminary resonance information through an interpolation algorithm to obtain more accurate resonance information.
Referring to fig. 3, fig. 3 is a flowchart illustrating a harmonic resonance suppression method for a flexible dc power transmission system according to a third embodiment of the present invention. In this embodiment, step S120, performing hanning windowed fourier transform processing on the current digital signal to obtain resonance information, includes:
s1220, performing Hanning windowing on the current digital signal and performing discrete Fourier transform to obtain a frequency spectrum analysis result;
s1221, carrying out resonance mode division on the frequency spectrum analysis result by a symmetric component method; wherein the resonant modes include a positive sequence resonant mode and a negative sequence resonant mode;
s1222, screening the spectrum analysis result with the maximum amplitude value from the spectrum analysis results divided into the positive sequence resonance modes as a potential resonance mode;
s1223, correcting the resonance mode parameters according to the spectrum analysis result of the potential resonance mode and a plurality of spectrum analysis results at the front and rear spectral lines of the spectrum analysis result of the potential resonance mode to obtain more accurate resonance information; the resonant mode parameters include frequency and amplitude.
In the embodiment of the invention, Hanning windowed Fourier transform processing is carried out on the current digital signal, and the used expression is as follows:
Figure RE-GDA0003150177510000091
Hann[n]＝0.5-0.5cos[2nπ/(N-1)]，n＝0，1，...，N-1
wherein j is a, b, c; i is a current digital signal; n is the window length, and N is the current data number in the window length; i isjIs the result of the frequency spectrum analysis; k is a spectral line number corresponding to the spectral analysis; frequency of kfs/N； fsThe sampling frequency at the time of measurement, N is the window length.
In the embodiment of the invention, the spectrum analysis result is divided into the resonance modes by a symmetric component method, and the used expression is as follows:
Figure RE-GDA0003150177510000101
Figure RE-GDA0003150177510000102
wherein j is a, b, c; i isjIs the result of the frequency spectrum analysis; k is the number of the spectral line corresponding to the spectral analysis, and the frequency is kfsN; p is a positive sequence component; n is a negative sequence component.
In the embodiment of the invention, the resonance mode parameters are corrected according to the spectrum analysis result of the potential resonance mode and a plurality of spectrum analysis results at the front and rear spectral lines of the spectrum analysis result of the potential resonance mode, and the used expression is as follows:
Figure RE-GDA0003150177510000103
Figure RE-GDA0003150177510000104
wherein A isHFRThe amplitude of the resonant mode; f. ofHFRA frequency that is a resonant mode; INT is an integer function; m is a spectral line number corresponding to the spectral analysis result with the maximum amplitude; fm]Frequency which is the result of the spectral analysis; am (A m)]Amplitude which is the result of the spectral analysis; Δ is a correction factor.
In the embodiment of the invention, the resonance information needs to satisfy that the amplitude information of the resonance mode is 2-5% larger than that of the positive sequence fundamental wave.
Referring to fig. 4, fig. 4 is a flowchart illustrating a harmonic resonance suppression method for a flexible dc power transmission system according to a fourth embodiment of the present invention. Step 130, performing phase locking processing on the same-frequency positive sequence three-phase voltage to obtain a phase locking result, and the method comprises the following steps:
s131, performing phase locking operation on the components of the same-frequency positive sequence three-phase voltage by using a phase-locked loop to obtain a phase angle;
s132, determining whether to perform an inverting operation on the phase angle according to the phase sequence of the resonance information to obtain an actually required phase angle of the park transformation, where an expression used by the phase angle of the park transformation is:
Figure RE-GDA0003150177510000111
wherein S isHFR1 represents that the phase sequence is positive; sHFR-1 represents a negative sequence;
s133, obtaining a phase locking result according to the phase angle of park transformation.
Referring to fig. 5, fig. 5 is a flowchart illustrating a harmonic resonance suppression method for a flexible dc power transmission system according to a fifth embodiment of the present invention. Step S150, performing proportional-integral control on the specific harmonic component of the current digital signal based on the phase-locked result to obtain a preliminary voltage reference value, including the following steps: s151, carrying out park transformation on the current digital signal based on the phase locking result, and converting the resonance component of the current digital signal into a first component and a second component; and S152, performing proportional integral control on the first component and the second component, and performing inverse park transformation to obtain a preliminary voltage reference value.
Referring to fig. 6, fig. 6 is a schematic structural diagram of a harmonic resonance suppression system of a flexible direct current transmission system according to a sixth embodiment of the present invention. The harmonic resonance suppression system of the flexible dc power transmission system provided in this embodiment includes a broadband resonance detection module 210, a resonance component phase-locked module 220, and a harmonic current control module 230;
the broadband resonance detection module 210 includes:
the signal acquisition module 211 is configured to acquire a three-phase current signal at an outlet of the converter and send the three-phase current signal to the analog-to-digital converter to obtain a current digital signal;
a resonance information obtaining module 212, configured to perform hanning windowed fourier transform processing on the current digital signal to obtain resonance information; the resonance information comprises frequency information, phase sequence information and amplitude information;
the screening and correcting module 213 is used for constructing ideal same-frequency positive sequence three-phase voltage according to the resonance information;
the resonant component phase-locking module 220 is used for performing phase-locking processing on the same-frequency positive-sequence three-phase voltage to obtain a phase-locking result;
the harmonic current control module 230 includes:
a proportional-integral module 231, configured to perform proportional-integral control on a specific harmonic component of the current digital signal based on a phase-locked result to obtain a preliminary voltage reference value;
and the superposition module 232 is configured to superpose the preliminary voltage reference value and the voltage reference value generated by the current inner loop to obtain a final voltage reference value.
In an embodiment of the present invention, the resonance information obtaining module 212 includes:
the initial processing unit is used for carrying out Hanning windowed Fourier transform processing on the current digital signal to obtain initial resonance information;
and the optimization processing unit is used for optimizing the preliminary resonance information through an interpolation algorithm to obtain more accurate resonance information.
Referring to fig. 7, fig. 7 is a schematic structural diagram of a harmonic resonance suppression system of a flexible direct current transmission system according to a seventh embodiment of the present invention. In the present embodiment, the resonance information acquisition module 212 includes:
a windowing unit 2121, configured to perform hanning windowing on the current digital signal and then perform discrete fourier transform on the current digital signal to obtain a spectral analysis result;
the mode screening unit 2122 is configured to perform resonance mode division on the spectrum analysis result by a symmetric component method; wherein the resonant modes include a positive sequence resonant mode and a negative sequence resonant mode;
the mode screening unit 2122 is further configured to screen a spectrum analysis result with the largest amplitude value from the spectrum analysis results divided into the positive-sequence resonance modes as a potential resonance mode;
the correction unit 2123 corrects the resonance mode parameters according to the spectrum analysis result of the potential resonance mode and a plurality of spectrum analysis results at the front and rear spectral lines of the spectrum analysis result of the potential resonance mode, so as to obtain more accurate resonance information; the resonant mode parameters include frequency and amplitude.
Referring to fig. 8, fig. 8 is a schematic structural diagram of a harmonic resonance suppression system of a flexible direct current transmission system according to an eighth embodiment of the present invention. In the present embodiment, the resonant component phase-locked module 220 includes:
the phase angle obtaining module 221 is configured to perform phase-locking operation on the components of the same-frequency positive-sequence three-phase voltage by using a phase-locked loop to obtain a phase angle;
the negation module 222 is configured to determine whether to perform negation on the phase angle according to the phase sequence of the resonance information to obtain an actually required phase angle of park transformation, where the expression used is:
Figure RE-GDA0003150177510000131
wherein S isHFR1 represents that the phase sequence is positive; sHFR-1 represents a negative sequence;
the phase-locked result obtaining module 223 obtains a phase-locked result according to the phase angle of park transformation.
In the embodiment of the present invention, the proportional-integral module 231 includes:
the park conversion unit is used for carrying out park conversion on the current digital signal based on the phase locking result and converting the resonance component of the current digital signal into a first component and a second component;
and the park inverse transformation unit is used for carrying out proportional integral control on the first component and the second component and then carrying out park inverse transformation to obtain a preliminary voltage reference value.
Referring to fig. 1 and 9, in an embodiment, a method for suppressing harmonic resonance of a flexible dc power transmission system includes the following steps:
(1) signal sampling: three-phase current signal i at outlet of current converter through current sensor and analog-to-digital conversionabc(t) conversion into a processable digital signal iabc[n]。
(2) Hanning windowed DFT: for the acquired digital signal iabc[n]A hanning windowed fourier transform process is performed followed by a discrete fourier transform.
(3) Calculating sequence components: the DFT result I is obtained by a symmetrical component methodj[k]Divided into positive-sequence resonant modes Ip[k]And negative sequence resonance mode In[k]。
(4) And (3) screening resonance modes: according to the DFT results of the positive and negative sequence resonance modes, one of the positive and negative sequence resonance modes with the largest amplitude is selected as a potential resonance mode Ip/n[m]。
(5) And (3) correcting a resonance mode: correcting the frequency f of a resonant mode according to the DFT result of the potential resonant mode and the DFT results at the front and rear spectral lines thereofHFRAmplitude AHFRAnd the like, so that the resonance frequency is closer to the actual resonance result.
(6) If the corrected amplitude A of the resonant modeHFRGreater than positive sequence fundamental amplitude A fP2% -5%, starting harmonic current control, and continuing to execute the next step; otherwise, the window is slid to the next window interval, and the step (2) is returned again to carry out Hanning windowing DFT.
(7) Resonant mode phase angle locking: according to the detected resonant frequency fHFRConstructing common-frequency positive sequence three-phase voltage, and performing phase locking on the voltage component by using a phase-locked loop; if the phase angle component is a positive sequence component, the phase angle component is directly used for park transformation in harmonic current control; if the negative sequence component is the negative sequence component, the negative sequence component is inverted and then used for park transformation.
(8) Resonance component park transformation: basing the converter station outlet current on the locking phase angle thetaHFRCarrying out park transformation, and then obtaining dq coordinates through a low-pass filtering linkDirect current component i under systemd-hfrAnd iq-hfr。
(9) Proportional Integral (PI) control: for the above dq component id-hfrAnd iq-hfrPerforming proportional integral control id-hfrAnd iq-hfrReference value i ofdref-hfrAnd iqref-hfrAre all taken as 0 to achieve the effect of suppressing the harmonic components of the specific frequency.
(10) Generating a reference voltage: outputting u from proportional-integral controllerdref-hfrAnd uqref-hfrCarrying out park inverse transformation to obtain a voltage reference value u controlled by harmonic currentref-hfrAnd the voltage reference value is superposed with a voltage reference value generated by an original current inner ring to form a final voltage reference value uref。
The embodiment of the invention mainly comprises two aspects of resonance component detection and additional harmonic current control.
Firstly, measuring a three-phase current signal at an outlet of a current converter by using a current sensor, primarily acquiring resonance information through Hanning windowing DFT, and then optimizing the resonance information through an interpolation algorithm to obtain accurate resonance information;
secondly, the phase locking is carried out on the electric signals with the same frequency based on the acquired resonant frequency, the resonant component is converted into direct current quantity through park transformation, and then the reference voltage for inhibiting the resonant component is obtained through a PI controller, so that the aim of inhibiting resonance is fulfilled.
The method can be used for inhibiting the broadband resonance in the practical engineering, can detect the harmonic component in a short time, starts the harmonic current control, can solve the problem of the broadband resonance with different resonance frequencies, and avoids the failure of the existing inhibiting method caused by the change of the system operation mode.
The harmonic current control can change the harmonic impedance under specific frequency without adding extra equipment and only by improving the original control strategy, and the effect of inhibiting specific harmonic components can be achieved on the basis of not influencing the original dynamic response of the system.
Referring to fig. 6 and 9, in an embodiment, the harmonic resonance suppression system of the flexible dc power transmission system includes a broadband resonance detection module 210, a resonant component phase-locked module 220, and a harmonic current control module 230.
The broadband resonance detection module 210 is used for performing broadband resonance detection:
the premise of the broadband resonance suppression of the flexible direct-current system is that a resonance mode needs to be quickly and accurately identified, and the invention takes three-phase current signals at the outlet of the current converter as input and finally outputs the frequency f of the resonance modeHFRPhase sequence SHFRAnd amplitude AHFRAnd (4) information. The main links comprise: signal sampling, Hanning windowed Discrete Fourier Transform (DFT), sequence component calculation, resonant mode screening, resonant mode correction, and harmonic current control start criterion.
(1) Signal sampling
Firstly, measuring three-phase current signals at an outlet of the current converter by using a current sensor; although the broadband resonance is related to higher frequency, the current sensor based on the giant magnetic damping effect has proved to have good performance under high-frequency and high-voltage conditions, so that the measurement of high-frequency components in three-phase current signals can be realized. Subsequently, the measured current signal i needs to be converted into an analog-to-digital signalabc(t) conversion to a digital signal i which can be further processedabc[n]。
(2) Hanning windowed DFT
For broadband resonance suppression, resonance information needs to be acquired in a short time, which requires that the window length of the DFT algorithm should be as short as possible. However, signal truncation due to a shorter window length can result in spectral leakage. Thus, the present invention employs a Hanning window to reduce leakage, whose function can be expressed as:
Hann[n]＝0.5-0.5cos[2nπ/(N-1)]，n＝0，1，...，N-1 (1)
where N represents the window length.
DFT result I of three-phase current signalj[k]The digital signal is obtained by subjecting the acquired digital signal to Hanning windowing DFT, and the formula is as follows:
Figure RE-GDA0003150177510000151
wherein j is a, b, c; i is a current digital signal; n is the window length, and N is the current data number in the window length; i isjWindowing the DFT results for hanning; k is a spectral line number corresponding to the spectral analysis; corresponding to a frequency of kfs/N，fsIs the sampling frequency at the time of measurement.
(3) Sequence component calculation
Resonant modes with different phase sequences may occur in broadband resonance, such as positive resonant mode Ip[k]Or negative-sequence resonance mode In[k]. Therefore, to further obtain accurate resonant mode information, the obtained DFT result needs to be further distinguished by a symmetric component method:
Figure RE-GDA0003150177510000161
wherein the content of the first and second substances,
Figure RE-GDA0003150177510000162
the subscripts p and n denote the positive and negative sequence components, respectively.
(4) Resonant mode screening
Due to the nonlinearity of the controller and the like, a plurality of harmonics appear at the initial stage of the system failure, and in order to avoid the interference of harmonic disturbance on the resonant mode acquisition, a component I with the maximum amplitude is screened from the DFT result of the positive and negative sequence components according to a sorting method such as a bubbling method and the likep/n[m]As a potential resonance mode, where m represents the spectral line position where the component is located in the DFT result.
(5) Resonant mode correction
Considering the barrier effect of DFT, the frequency resolution of hanning windowed DFT results is related to its window length; that is, the presently acquired resonance mode information may not be accurate. For example, when the window length is 0.04s, the frequency resolution is 25 Hz; if the frequency of the resonant mode is not a multiple of 25Hz, the frequency and amplitude of the resonant mode are obtained with a large error.
Therefore, hanning windowed DFT results need to be corrected, and accurate detection results of the resonance mode are obtained according to the potential resonance mode and three DFT results at the front and rear spectral lines, and the calculation formula is as follows:
Figure RE-GDA0003150177510000163
wherein INT is an integer function; fm]And A [ m ]]Is represented byp/n[m]Frequency and amplitude of (d); Δ is a correction factor, which can be given by:
Figure RE-GDA0003150177510000164
(6) harmonic current control start criterion
If the amplitude of the corrected resonance mode is larger than the positive sequence fundamental wave amplitude A fP2% -5%, starting harmonic current control, and continuing to execute the related steps downwards; otherwise, the window is slid to the next window interval, and the step (2) is returned again to carry out Hanning windowing DFT. Wherein, the positive sequence fundamental wave amplitude AfPCan be obtained from hanning windowed DFT results.
The second resonant component phase-locking module 220 is used for realizing resonant component phase-locking:
the resonance frequency of the broadband resonance of the flexible direct current system is uncertain, and the resonance component to be processed is difficult to be converted into direct current through a fixed phase angle for processing. According to the detection result of the resonance mode, the phase locking result is corrected on line, so that the resonance components in different events are converted into direct current components, and the implementation of a subsequent control strategy is facilitated.
First, according to the detected resonance frequency fHFRConstructing ideal same-frequency positive-sequence three-phase voltage uabcThe voltage component varies according to the variation of the resonant mode frequency.
Secondly, the voltage component u is phase-locked loopabcPerforming phase-locked operationTo a phase angle theta.
Finally, according to the phase sequence of the resonance mode, whether to invert theta is determined to obtain the actually required park transformation phase angle thetaHFRIt can be expressed as:
Figure RE-GDA0003150177510000171
wherein S isHFR1 indicates that the resonance mode is positive; sHFR-1 indicates that the resonant mode is negative.
The (iii) harmonic current control module 230 is configured to perform harmonic current control:
the harmonic current control can change the harmonic impedance under specific frequency without adding extra equipment and only by improving the original control strategy, and the effect of inhibiting specific harmonic components can be achieved on the basis of not influencing the original dynamic response of the system.
The basic structure of harmonic current control is shown in fig. 1, and comprises four parts, namely park transformation, low-pass filtering, PI control and park inverse transformation; and the finally generated voltage reference value is superposed with the voltage reference value generated by the original current inner ring to obtain a final reference value.
Firstly, the outlet current i of the converter station is measuredabc(t) is carried out based on the phase angle thetaHFRPark transformation of converting the resonance component into dq component idAnd iq；
Subsequently, i isdAnd iqRespectively avoiding the influence of other frequency harmonics through a low-pass filter to obtain id-hfrAnd iq-hfrThis component corresponds to the resonance component in the abc coordinate system.
Further, for id-hfrAnd iq-hfrPerforming PI control id-hfrAnd iq-hfrReference value i ofdref-hfrAnd iqref-hfrAre all set to 0, the formula can be expressed as:
Figure RE-GDA0003150177510000181
finally, the obtained dq axis voltage reference value u is compareddref-hfrAnd uqref-hfrCarrying out park inverse transformation to obtain a voltage reference value u under the abc coordinateref-hfr。
Reference value u of voltageref-hfrAnd superposing the voltage reference value with the voltage reference value generated by the original current inner ring to form a final voltage reference value. And determining reference voltages of an upper bridge arm and a lower bridge arm according to the voltage reference value, forming switching signals of each switching tube in a modulation mode such as carrier phase shift PWM (pulse width modulation), determining the output voltage of the converter, and finishing the suppression of harmonic components.
In the embodiment of the invention, (1) resonance mode screening: other common sorting methods besides bubble sorting may be used to sort the magnitudes of the positive and negative sequence component DFT results. (2) The starting criterion of the harmonic current control is as follows: the threshold of 2% -5% is a variable and can be selected according to actual conditions. (3) In the implementation of the resonance component phase locking, the amplitude and the phase of the constructed three-phase voltage can be selected within a reasonable range. (4) In the implementation of the resonant component phase-locked loop, the structure of the phase-locked loop should include all the common structures at present, such as a traditional three-phase-locked loop, a phase-locked loop based on a synchronous reference frame (SRF-PLL), a phase-locked loop based on a biquad generalized integrator (DSOGI-PLL), and the like. (5) In the harmonic current control, the implementation of the low-pass filtering should include all the common structures at present, such as a first-order filter, a second-order filter, a digital filter, and so on.
The embodiment of the invention combines the broadband resonance detection and the harmonic current control to form a set of complete closed-loop control strategy. The broadband resonance detection takes three-phase current signals at the outlet of the current converter as input, finally outputs frequency, phase sequence and amplitude information of the resonance mode, and combines a symmetric component method and Hanning windowed interpolation to realize quick and accurate detection of the positive and negative sequence resonance mode.
According to the embodiment of the invention, the ideal same-frequency positive sequence three-phase voltage is constructed according to the detected resonant frequency, and the phase locking of the resonant mode under different conditions is realized by performing the phase locking on the voltage.
According to the embodiment of the invention, proportional integral control is carried out on specific harmonic components based on a phase locking result through harmonic current control, and an obtained voltage reference value is superposed with a voltage reference value generated by an original current inner loop to form a final voltage reference value. The harmonic current control can achieve the effect of inhibiting specific harmonic components on the basis of not influencing the original dynamic response of the system.
Referring to fig. 10, an embodiment of the invention provides a computer terminal device, which includes one or more processors and a memory. A memory is coupled to the processor for storing one or more programs which, when executed by the one or more processors, cause the one or more processors to implement the method of harmonic resonance suppression for a flexible direct current power transmission system as in any one of the embodiments above.
The processor is used for controlling the overall operation of the computer terminal equipment so as to complete all or part of the steps of the harmonic resonance suppression method of the flexible direct current transmission system. The memory is used to store various types of data to support the operation at the computer terminal device, which data may include, for example, instructions for any application or method operating on the computer terminal device, as well as application-related data. The Memory may be implemented by any type of volatile or non-volatile Memory device or combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read-Only Memory (EPROM), Programmable Read-Only Memory (PROM), Read-Only Memory (ROM), magnetic Memory, flash Memory, magnetic disk, or optical disk.
In an exemplary embodiment, the computer terminal Device may be implemented by one or more Application Specific 1 integrated circuits (AS 1C), a Digital Signal Processor (DSP), a Digital Signal Processing Device (DSPD), a Programmable Logic Device (PLD), a Field Programmable Gate Array (FPGA), a controller, a microcontroller, a microprocessor or other electronic components, and is configured to perform the harmonic resonance suppression method of the flexible dc power transmission system and achieve technical effects consistent with the above method.
In another exemplary embodiment, a computer readable storage medium comprising program instructions for implementing the steps of the harmonic resonance suppression method of the flexible direct current transmission system in any of the above embodiments when executed by a processor is also provided. For example, the computer readable storage medium may be the above memory including program instructions executable by a processor of a computer terminal device to perform the above harmonic resonance suppression method of the flexible direct current transmission system, and achieve technical effects consistent with the above method.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims (16)

1. A harmonic resonance suppression method of a flexible direct current transmission system is characterized by comprising the following steps:
acquiring a three-phase current signal at an outlet of the current converter and sending the three-phase current signal to the analog-to-digital converter to obtain a current digital signal;
carrying out Hanning windowed Fourier transform processing on the current digital signal to obtain resonance information; wherein the resonance information comprises frequency information, phase sequence information and amplitude information;
constructing ideal same-frequency positive sequence three-phase voltage according to the resonance information;
performing phase locking processing on the same-frequency positive sequence three-phase voltage to obtain a phase locking result;
performing proportional integral control on specific harmonic components of the current digital signal based on the phase locking result to obtain a preliminary voltage reference value;
and superposing the preliminary voltage reference value and a voltage reference value generated by the current inner ring to obtain a final voltage reference value.
2. The harmonic resonance suppression method of the flexible direct current transmission system according to claim 1, wherein the performing hanning windowed fourier transform processing on the current digital signal to obtain resonance information comprises:
carrying out Hanning windowed Fourier transform processing on the current digital signal to obtain preliminary resonance information;
and optimizing the initial resonance information through an interpolation algorithm to obtain more accurate resonance information.
3. The harmonic resonance suppression method of the flexible direct current transmission system according to claim 1, wherein the performing hanning windowed fourier transform processing on the current digital signal to obtain resonance information comprises:
performing Hanning windowing on the current digital signal and then performing discrete Fourier transform to obtain a frequency spectrum analysis result;
carrying out resonance mode division on the frequency spectrum analysis result by a symmetric component method; wherein the resonant modes include a positive sequence resonant mode and a negative sequence resonant mode;
screening a spectrum analysis result with the maximum amplitude value from spectrum analysis results divided into the positive sequence resonance modes as a potential resonance mode;
correcting resonance mode parameters according to the spectrum analysis result of the potential resonance mode and the spectrum analysis results of the spectral lines before and after the potential resonance mode to obtain more accurate resonance information; the resonant mode parameters include frequency and amplitude.
4. The harmonic resonance suppression method of a flexible direct current transmission system according to claim 3, characterized in that the current digital signal is subjected to Hanning windowed Fourier transform processing using the expression:
Figure FDA0003104746020000021
Hann[n]＝0.5-0.5cos[2nπ/(N-1)]，n＝0，1，...，N-1
wherein j is a, b, c; i is a current digital signal; n is the window length, and N is the current data number in the window length; i isjIs the result of the frequency spectrum analysis; k is a spectral line number corresponding to the spectral analysis; frequency of kfs/N；fsIs the sampling frequency at the time of measurement.
5. The harmonic resonance suppression method of the flexible direct current transmission system according to claim 3, wherein the results of the spectrum analysis are divided into the resonance modes by a symmetric component method, and the formula is as follows:
Figure FDA0003104746020000022
Figure FDA0003104746020000023
wherein j is a, b, c; i isjIs the result of the frequency spectrum analysis; k is the number of the spectral line corresponding to the spectral analysis, and the frequency is kfsN; p is a positive sequence component; n is a negative sequence component.
6. The harmonic resonance suppression method of the flexible direct current transmission system according to claim 3, wherein the resonance mode parameters are corrected according to the results of the spectrum analysis of the potential resonance mode and the results of the spectrum analysis at the spectral lines before and after the potential resonance mode, and the following expressions are used:
Figure FDA0003104746020000031
Figure FDA0003104746020000032
wherein A isHFRThe amplitude of the resonant mode; f. ofHFRA frequency that is a resonant mode; INT is an integer function; m is a spectral line number corresponding to the spectral analysis result with the maximum amplitude; fm]Is the frequency of the result of the spectral analysis; am (A m)]Is the amplitude of the spectral analysis result; Δ is a correction factor.
7. The harmonic resonance suppression method of the flexible direct current transmission system according to claim 1, wherein the resonance information is required to satisfy that the amplitude information of the resonance mode is greater than 2% -5% of the amplitude information of the positive-sequence fundamental wave.
8. The harmonic resonance suppression method of the flexible direct current transmission system according to claim 1, wherein the phase-locking processing of the same-frequency positive-sequence three-phase voltage to obtain a phase-locked result comprises:
performing phase locking operation on the components of the same-frequency positive-sequence three-phase voltage by using a phase-locked loop to obtain a phase angle;
according to the phase sequence of the resonance information, determining whether to perform an inversion operation on the phase angle to obtain the actually required phase angle of park transformation, wherein the used expression is as follows:
Figure FDA0003104746020000033
wherein, thetaHFRFor the phase angle of the park transformation actually required, theta is the phase-locked operation to obtain the phase angle, SHFR1 represents that the phase sequence is positive; sHFR-1 represents a negative sequence;
and obtaining a phase locking result according to the phase angle of the park transformation.
9. The harmonic resonance suppression method of the flexible direct current transmission system according to claim 1, wherein the proportional-integral controlling of the specific harmonic component of the current digital signal based on the phase locking result to obtain a preliminary voltage reference value comprises:
performing park transformation on the current digital signal based on the phase locking result, and converting a resonance component of the current digital signal into a first component and a second component;
and performing proportional integral control on the first component and the second component, and performing inverse park transformation to obtain a preliminary voltage reference value.
10. A harmonic resonance suppression system of a flexible direct current transmission system is characterized by comprising a broadband resonance detection module, a resonance component phase-locking module and a harmonic current control module;
the broadband resonance detection module comprises:
the signal acquisition module is used for acquiring a three-phase current signal at the outlet of the current converter and sending the three-phase current signal to the analog-to-digital converter to obtain a current digital signal;
the resonance information acquisition module is used for carrying out Hanning windowed Fourier transform processing on the current digital signal to obtain resonance information; wherein the resonance information comprises frequency information, phase sequence information and amplitude information;
the screening correction module is used for constructing ideal same-frequency positive sequence three-phase voltage according to the resonance information;
the resonant component phase-locking module is used for performing phase-locking processing on the same-frequency positive sequence three-phase voltage to obtain a phase-locking result;
the harmonic current control module includes:
the proportional integral module is used for carrying out proportional integral control on the specific harmonic component of the current digital signal based on the phase locking result to obtain a preliminary voltage reference value;
and the superposition module is used for superposing the preliminary voltage reference value and a voltage reference value generated by the current inner ring to obtain a final voltage reference value.
11. The harmonic resonance suppression system of a flexible direct current transmission system according to claim 10, characterized in that the resonance information acquisition module comprises:
the primary processing unit is used for carrying out Hanning windowed Fourier transform processing on the current digital signal to obtain primary resonance information;
and the optimization processing unit is used for optimizing the initial resonance information through an interpolation algorithm to obtain more accurate resonance information.
12. The harmonic resonance suppression system of a flexible direct current transmission system according to claim 10, characterized in that the resonance information acquisition module comprises:
the windowing unit is used for performing Hanning windowing on the current digital signal and then performing discrete Fourier transform to obtain a frequency spectrum analysis result;
the mode screening unit is used for carrying out resonance mode division on the frequency spectrum analysis result through a symmetric component method; wherein the resonant modes include a positive sequence resonant mode and a negative sequence resonant mode;
the mode screening unit is further used for screening a spectrum analysis result with the largest amplitude value from the spectrum analysis results divided into the positive sequence resonance modes as a potential resonance mode;
the correction unit corrects the resonance mode parameters according to the spectrum analysis result of the potential resonance mode and a plurality of spectrum analysis results at the front spectral line and the rear spectral line of the spectrum analysis result of the potential resonance mode to obtain more accurate resonance information; the resonant mode parameters include frequency and amplitude.
13. The harmonic resonance suppression system of a flexible direct current transmission system according to claim 10, wherein the resonant component phase-locked module comprises:
the phase angle acquisition module is used for carrying out phase locking operation on the components of the same-frequency positive sequence three-phase voltage by using a phase-locked loop to obtain a phase angle;
the negation module is used for determining whether to perform negation operation on the phase angle according to the phase sequence of the resonance information so as to obtain the actually required phase angle of park transformation, and the used expression is as follows:
Figure FDA0003104746020000051
wherein, thetaHFRFor the phase angle of the park transformation actually required, theta is the phase-locked operation to obtain the phase angle, SHFR1 represents that the phase sequence is positive; sHFR-1 represents a negative sequence;
and the phase locking result acquisition module is used for acquiring a phase locking result according to the phase angle of the park transformation.
14. The harmonic resonance suppression system of a flexible direct current transmission system according to claim 10, characterized in that the proportional-integral module comprises:
the park transformation unit is used for carrying out park transformation on the current digital signal based on the phase locking result and converting a resonance component of the current digital signal into a first component and a second component;
and the park inverse transformation unit is used for carrying out proportional integral control on the first component and the second component and then carrying out park inverse transformation to obtain a preliminary voltage reference value.
15. A computer terminal device, comprising:
one or more processors;
a memory coupled to the processor for storing one or more programs;
when executed by the one or more processors, cause the one or more processors to implement a method of harmonic resonance suppression for a flexible direct current power transmission system according to any one of claims 1 to 9.
16. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out a method of harmonic resonance suppression of a flexible direct current power transmission system according to any one of claims 1 to 9.
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