CN111521870A - Method, device, equipment and medium for identifying resonant frequency of grid-connected converter equipment - Google Patents

Method, device, equipment and medium for identifying resonant frequency of grid-connected converter equipment Download PDF

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Publication number
CN111521870A
CN111521870A CN202010484354.3A CN202010484354A CN111521870A CN 111521870 A CN111521870 A CN 111521870A CN 202010484354 A CN202010484354 A CN 202010484354A CN 111521870 A CN111521870 A CN 111521870A
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preset
identification
grid
resonant frequency
connected converter
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CN111521870B (en
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吴轩钦
董瑞勇
王国建
周志达
沈文
王二峰
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Shenzhen Invt Electric Co Ltd
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Shenzhen Invt Electric Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
    • G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/01—Frequency selective two-port networks
    • H03H7/0115—Frequency selective two-port networks comprising only inductors and capacitors
    • 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

Abstract

The application discloses a method and a device for identifying resonant frequency of grid-connected converter equipment, electronic equipment and a computer readable storage medium, wherein the method comprises the following steps: acquiring a capacitance voltage signal of the LCL filter; extracting a fluctuation component signal of the capacitance voltage signal; respectively sending the fluctuation component signals to two preset identification controllers with the same structure and different center frequencies to obtain two output identification variable values; performing PI control based on the difference value of the two identification variable values to adjust the center frequencies of the two preset identification controllers in real time until the closed loop stable state is reached; and determining the average value of the central frequencies of the two preset identification controllers in the closed loop steady state as the resonant frequency of the grid-connected converter equipment. The frequency characteristic of the identification result of two preset identification controllers with different center frequencies about the resonant frequency is utilized, the resonant frequency of the grid-connected converter equipment can be effectively tracked and identified by combining PI closed-loop control, and the identification rate, the accuracy and the real-time performance are effectively improved.

Description

Method, device, equipment and medium for identifying resonant frequency of grid-connected converter equipment
Technical Field
The present disclosure relates to the field of electrical technologies, and in particular, to a method and an apparatus for identifying a resonant frequency of a grid-connected converter device, an electronic device, and a computer-readable storage medium.
Background
Grid-connected converter equipment such as grid-connected inverters and reactive compensators are generally equipped with and use an LCL type filter. However, the LCL filter has an inherent resonance point, which is very susceptible to resonance phenomenon under harmonic excitation condition, and may cause system instability. Therefore, the resonance suppression of the LCL type filter can be further performed by identifying the resonance frequency.
When the resonant frequency is identified by methods based on Fourier analysis and the like in the related technology, the time consumption is long because Fourier transformation needs enough data volume to ensure the frequency precision, the method cannot adapt to the condition of frequent change of the resonant frequency in real time, and the requirements on the calculation and storage capacity of a chip are high.
In view of the above, it is an important need for those skilled in the art to provide a solution to the above technical problems.
Disclosure of Invention
The application aims to provide a method and a device for identifying the resonant frequency of a grid-connected converter device, an electronic device and a computer-readable storage medium, so that the resonant frequency can be accurately identified in real time on line to guarantee the resonance suppression effect.
In order to solve the above technical problem, in a first aspect, the present application discloses a method for identifying a resonant frequency of a grid-connected converter device, where the grid-connected converter device includes an LCL filter, and the method includes:
acquiring a capacitance voltage signal of the LCL filter;
extracting a fluctuation component signal of the capacitance voltage signal;
respectively sending the fluctuation component signals to two preset identification controllers with the same structure and different center frequencies to obtain two output identification variable values;
performing PI control based on the difference value of the two identification variable values to adjust the center frequencies of the two preset identification controllers in real time until the closed loop stable state is achieved;
and determining the average value of the central frequencies of the two preset identification controllers in the closed loop steady state as the resonant frequency of the grid-connected converter equipment.
Optionally, the extracting a fluctuation component signal of the capacitance voltage signal includes:
extracting a fundamental wave signal of the capacitance voltage signal;
and taking the difference value of the capacitance voltage signal and the fundamental wave signal as the fluctuation component signal.
Optionally, the extracting a fundamental wave signal of the capacitance voltage signal includes:
extracting the fundamental wave signal according to a preset fundamental wave signal extraction formula, wherein the preset fundamental wave signal extraction formula is as follows:
Figure BDA0002518563580000021
wherein u isc_fundIs the fundamental wave signal; u. ofcIs the capacitance voltage signal; k is a radical offundIs an extraction coefficient; omegafundIs the fundamental angular frequency.
Optionally, an output expression of a first preset identification controller of the two preset identification controllers is:
Figure BDA0002518563580000022
wherein x isiden1A first identification variable value output by the first preset identification controller; u. ofc_flucIs the fluctuating component signal; omegac1A preset bandwidth for the first preset identification controller; omegaf1Identifying the center frequency of the first preset identification controller; omegaf0Is the center frequency median; Δ ωfIs a preset frequency increment value;
the output expression of the second preset identification controller is as follows:
Figure BDA0002518563580000023
wherein x isiden2A second identification variable value output by the second preset identification controller; omegac2The preset bandwidth of the second preset identification controller; omegaf2The center frequency of the second preset identification controller.
Optionally, the performing PI control based on a difference between the two identification variable values to adjust the center frequencies of the two preset identification controllers in real time until entering a closed loop steady state includes:
calculating PI control quantity based on the difference value of the two identification variable values according to a preset PI control formula; the preset PI control formula is as follows:
Figure BDA0002518563580000031
wherein, Δ ωPIThe PI control quantity is the PI control quantity; kPIs a preset proportionality coefficient; kIIs a preset integral coefficient; e.g. of the typePIIs the difference between the two identifying variable values;
updating the center frequency intermediate value based on the PI control quantity according to a preset frequency adjustment formula so as to update the center frequencies of the two preset identification controllers based on the center frequency intermediate value; the preset frequency adjustment formula is as follows:
Figure BDA0002518563580000032
wherein the content of the first and second substances,
Figure BDA0002518563580000033
ωres_midpresetting a reference value for the resonant frequency;
Figure BDA0002518563580000034
L1the inductance value of the grid-connected converter equipment side of the LCL filter is obtained; l is2A grid side inductance value for the LCL filter; cfIs the capacitance value of the LCL filter; l isgIs the grid inductance.
Optionally, the determining an average value of center frequencies of the two preset identification controllers in a closed-loop steady state as the resonant frequency of the grid-connected converter device includes:
and approximately calculating the average value as the resonant frequency of the grid-connected converter equipment according to a preset calculation formula, wherein the preset calculation formula is as follows:
Figure BDA0002518563580000035
wherein, ω isresIs the resonance frequency.
In a second aspect, the present application further discloses a resonant frequency identification device for grid-connected converter equipment, where the grid-connected converter equipment includes an LCL filter, and the device includes:
the acquisition unit is used for acquiring a capacitance voltage signal of the LCL filter;
an extraction unit for extracting a fluctuation component signal of the capacitance voltage signal;
the identification unit is used for respectively sending the fluctuation component signals to two preset identification controllers with the same structure and different center frequencies so as to obtain two output identification variable values;
the adjusting unit is used for carrying out PI control on the basis of the difference value of the two identification variable values so as to adjust the central frequencies of the two preset identification controllers in real time until the closed loop stable state is achieved;
and the determining unit is used for determining the average value of the central frequencies of the two preset identification controllers in the closed loop steady state as the resonant frequency of the grid-connected converter equipment.
Optionally, the extracting unit is specifically configured to:
extracting a fundamental wave signal of the capacitance voltage signal; and taking the difference value of the capacitance voltage signal and the fundamental wave signal as the fluctuation component signal.
Optionally, the extracting unit is specifically configured to:
extracting the fundamental wave signal according to a preset fundamental wave signal extraction formula, wherein the preset fundamental wave signal extraction formula is as follows:
Figure BDA0002518563580000041
wherein u isc_fundIs the fundamental wave signal; u. ofcIs the capacitance voltage signal; k is a radical offundIs an extraction coefficient; omegafundIs the fundamental angular frequency.
Optionally, an output expression of a first preset identification controller of the two preset identification controllers is:
Figure BDA0002518563580000042
wherein x isiden1A first identification variable value output by the first preset identification controller; u. ofc_flucIs the fluctuating component signal; omegac1A preset bandwidth for the first preset identification controller; omegaf1Identifying the center frequency of the first preset identification controller; omegaf0Is the center frequency median; Δ ωfIs a preset frequency increment value;
the output expression of the second preset identification controller is as follows:
Figure BDA0002518563580000051
wherein x isiden2A second identification variable value output by the second preset identification controller; omegac2Is the second presetIdentifying a preset bandwidth of a controller; omegaf2The center frequency of the second preset identification controller.
Optionally, the adjusting unit is specifically configured to:
calculating PI control quantity based on the difference value of the two identification variable values according to a preset PI control formula; the preset PI control formula is as follows:
wherein, Δ ωPIThe PI control quantity is the PI control quantity; kPIs a preset proportionality coefficient; kIIs a preset integral coefficient; e.g. of the typePIIs the difference between the two identifying variable values;
updating the center frequency intermediate value based on the PI control quantity according to a preset frequency adjustment formula so as to update the center frequencies of the two preset identification controllers based on the center frequency intermediate value; the preset frequency adjustment formula is as follows:
Figure BDA0002518563580000053
wherein the content of the first and second substances,
Figure BDA0002518563580000054
ωres_midpresetting a reference value for the resonant frequency;
Figure BDA0002518563580000055
L1the inductance value of the grid-connected converter equipment side of the LCL filter is obtained; l is2A grid side inductance value for the LCL filter; cfIs the capacitance value of the LCL filter; l isgIs the grid inductance.
Optionally, the determining unit is specifically configured to:
and approximately calculating the average value as the resonant frequency of the grid-connected converter equipment according to a preset calculation formula, wherein the preset calculation formula is as follows:
Figure BDA0002518563580000056
wherein, ω isresIs the resonance frequency.
In a third aspect, the present application also discloses an electronic device, including:
a memory for storing a computer program;
a processor for executing the computer program to implement the steps of any one of the above-mentioned methods for identifying a resonant frequency of a grid-connected inverter device.
In a fourth aspect, the present application further discloses a computer-readable storage medium, in which a computer program is stored, where the computer program is used to implement the steps of any one of the methods for identifying a resonant frequency of a grid-connected converter device as described above when the computer program is executed by a processor.
The method for identifying the resonant frequency of the grid-connected converter equipment is applied to the grid-connected converter equipment comprising an LCL filter, and comprises the following steps: acquiring a capacitance voltage signal of the LCL filter; extracting a fluctuation component signal of the capacitance voltage signal; respectively sending the fluctuation component signals to two preset identification controllers with the same structure and different center frequencies to obtain two output identification variable values; performing PI control based on the difference value of the two identification variable values to adjust the center frequencies of the two preset identification controllers in real time until the closed loop stable state is achieved; and determining the average value of the central frequencies of the two preset identification controllers in the closed loop steady state as the resonant frequency of the grid-connected converter equipment.
Therefore, the frequency characteristics of the identification results of the two preset identification controllers with the same structure and different center frequencies about the resonant frequency are utilized, the PI closed-loop control is combined, the resonant frequency of the grid-connected converter equipment can be effectively tracked and identified, the whole processing process does not need a large amount of data calculation, the identification accuracy is guaranteed, the identification rate and the real-time performance are effectively improved, and the resonant frequency can be accurately identified on line in real time to guarantee the resonance inhibition effect. The resonant frequency identification device of the grid-connected converter equipment, the electronic equipment and the computer-readable storage medium have the same beneficial effects.
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In order to more clearly illustrate the technical solutions in the prior art and the embodiments of the present application, the drawings that are needed to be used in the description of the prior art and the embodiments of the present application will be briefly described below. Of course, the following description of the drawings related to the embodiments of the present application is only a part of the embodiments of the present application, and it will be obvious to those skilled in the art that other drawings can be obtained from the provided drawings without any creative effort, and the obtained other drawings also belong to the protection scope of the present application.
Fig. 1 is a schematic circuit connection diagram of a grid-connected converter device disclosed in an embodiment of the present application;
fig. 2 is a flowchart of a resonant frequency identification method for grid-connected converter equipment disclosed in the embodiment of the present application;
fig. 3 is a schematic diagram of a method for identifying a resonant frequency of a grid-connected converter device disclosed in the embodiment of the present application;
fig. 4 is a block diagram of a resonant frequency identification device of a grid-connected converter apparatus according to an embodiment of the present disclosure;
fig. 5 is a block diagram of an electronic device according to an embodiment of the present disclosure.
Detailed Description
The core of the application is to provide a method and a device for identifying the resonant frequency of the grid-connected converter equipment, the electronic equipment and a computer-readable storage medium, so that the resonant frequency can be accurately identified in real time on line to guarantee the resonance suppression effect.
In order to more clearly and completely describe the technical solutions in the embodiments of the present application, the technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. It is to be understood that the embodiments described are only a few embodiments of the present application and not all 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 application.
Currently, grid-connected converter devices such as grid-connected inverters and reactive compensators are generally equipped with LCL filters. However, the LCL filter has an inherent resonance point, which is liable to cause a resonance phenomenon under harmonic excitation conditions, and may cause system instability. Therefore, the resonance suppression of the LCL type filter can be further performed by identifying the resonance frequency.
When the resonant frequency is identified by methods based on Fourier analysis and the like in the related technology, the time consumption is long because Fourier transformation needs enough data volume to ensure the frequency precision, the method cannot adapt to the condition of frequent change of the resonant frequency in real time, and the requirements on the calculation and storage capacity of a chip are high. In view of this, the present application provides a resonant frequency identification scheme for grid-connected converter equipment, which can effectively solve the above problems.
Referring to fig. 1, fig. 1 is a schematic circuit connection diagram of a grid-connected converter device disclosed in an embodiment of the present application.
The grid-connected converter equipment comprises a power circuit module, a control processing module and an LCL filter. The power circuit module is connected to the power grid through the LCL filter. The control processing module is used for controlling the operation of the power circuit module and can be used for identifying the resonant frequency so as to carry out resonance suppression based on the identified resonant frequency.
In the LCL filter, the inductance at one side of the grid-connected converter equipment is marked as L1(the size of the grid-connected equipment side inductance in each phase circuit is L1) (ii) a The inductance on the grid side is denoted as L2(the size of the grid side inductance in each phase circuit is L2) (ii) a The capacitance in each phase circuit is Cf. Accordingly, the magnitude of the capacitor voltage is recorded as uc. The equivalent inductance of each phase circuit in the power grid is marked as Lg。
It should be added that, in the present application, the grid-connected converter device may be specifically a grid-connected inverter, a PWM rectifier, a reactive compensator, and the like, and the power circuit module in fig. 1 is only schematically represented, and its specific circuit structure depends on the grid-connected converter device itself.
Referring to fig. 2, an embodiment of the application discloses a method for identifying a resonant frequency of a grid-connected converter device. The grid-connected converter equipment comprises an LCL filter, the method can be particularly applied to a control processing module of the grid-connected converter equipment, and mainly comprises the following steps:
s101: obtaining a capacitance voltage signal u of an LCL filterc。
Specifically, a sampling unit is disposed in each of the general grid-connected inverter devices to collect a capacitance voltage signal u of the LCL filtercAnd the capacitor voltage signal u generated by acquisition can be directly acquiredcFor identifying the resonant frequency.
S102: extracting a capacitor voltage signal ucIs measured on the wave component signal uc_fluc。
S103: will fluctuate the component signal uc_flucThe two identification variables are respectively sent to two preset identification controllers with the same structure and different center frequencies to obtain two output identification variable values.
S104: and performing PI control based on the difference value of the two identification variable values to adjust the central frequencies of the two preset identification controllers in real time until the closed loop stable state is reached.
Specifically, the method for identifying the resonant frequency provided by the application is realized based on closed-loop control. This application is provided with two structures in advance the same, the different predetermine identification control ware of central frequency, and two predetermine identification control ware respectively output respective identification variable value. Simultaneously, this application still is provided with the PI controller, can distinguish the difference of variable value based on two and carry out PI control, and then in turn adjusts the central frequency of two predetermine discernment controllers according to PI controlled variable.
It is easily understood by those skilled in the art that when the difference between the two identification variable values is zero (close to zero), the PI control amount is close to zero, so that the adjustment amount for the center frequencies of the two preset identification controllers is also close to zero, and further, the two output identification variable values tend to be stable, and the difference between the two identification variable values is continuously maintained to zero, at this time, the system reaches the closed loop steady state.
It should be noted that, since the difference between the two identification variable values has no actual meaning, the "difference between the two identification variable values" in the present application may be specifically "difference between absolute values of the two identification variable values".
According to the characteristics of the resonant frequency, for two preset identification controllers with different center frequencies, when the center frequencies of the two preset identification controllers are symmetrical about the resonant frequency, two identification variable values output by the two preset identification controllers are stable and equal, and then the system reaches a closed loop steady state.
Therefore, after the system is judged to reach the closed-loop steady state, the resonant frequency can be identified according to the central frequencies of the two preset identification controllers in the closed-loop steady state. It is easy to understand that when the center frequencies of the two preset identification controllers are symmetrical about the resonant frequency, the average value of the two center frequencies is the resonant frequency.
S105: and determining the average value of the central frequencies of the two preset identification controllers in the closed loop steady state as the resonant frequency of the grid-connected converter equipment.
Further, after the identification result of the resonant frequency is obtained, the identified resonant frequency can be used for resonance suppression processing, for example, for the grid-connected inverter, the active damping parameter, the current regulator parameter, the voltage feedforward filter parameter, and the like in the notch filter of the grid-connected inverter can be adjusted on line according to the resonant frequency, so as to improve the operation performance of the LCL type grid-connected inverter.
The method for identifying the resonant frequency of the grid-connected converter equipment provided by the embodiment of the application comprises the following steps: acquiring a capacitance voltage signal of the LCL filter; extracting a fluctuation component signal of the capacitance voltage signal; respectively sending the fluctuation component signals to two preset identification controllers with the same structure and different center frequencies to obtain two output identification variable values; performing PI control based on the difference value of the two identification variable values to adjust the center frequencies of the two preset identification controllers in real time until the closed loop stable state is reached; and determining the average value of the central frequencies of the two preset identification controllers in the closed loop steady state as the resonant frequency of the grid-connected converter equipment.
Therefore, the method for identifying the resonant frequency of the grid-connected converter equipment, provided by the application, can effectively track and identify the resonant frequency of the grid-connected converter equipment by utilizing the frequency characteristics of the identification results of the two preset identification controllers with the same structure and different center frequencies and combining PI closed-loop control, and the whole processing process does not need a large amount of data calculation, so that the identification accuracy is guaranteed, the identification rate and the real-time performance are effectively improved, and the resonant frequency can be accurately identified on line in real time to guarantee the resonance inhibition effect.
As a specific embodiment, the method for identifying the resonant frequency of the grid-connected converter device provided in the embodiment of the present application extracts the capacitor voltage signal u on the basis of the above contentscIs measured on the wave component signal uc_flucThe method can specifically comprise the following steps:
extracting a capacitor voltage signal ucFundamental wave signal u ofc_fund；
Converting the capacitor voltage signal ucAnd fundamental wave signal uc_fundAs the fluctuation component signal uc_fluc。
Wherein further, as an embodiment, the capacitance voltage signal u is extractedcFundamental wave signal u ofc_fundThe method can specifically comprise the following steps:
extracting fundamental wave signal u according to a preset fundamental wave signal extraction formulac_fundThe preset fundamental wave signal extraction formula is as follows:
Figure BDA0002518563580000101
wherein u isc_fundIs a fundamental wave signal; u. ofcIs a capacitance voltage signal; k is a radical offundIs an extraction coefficient; omegafundIs the fundamental angular frequency. Furthermore, it is understood by those skilled in the art that s represents a differential operator in the time domain, and the present application will not be described in detail hereinafter.
Specifically, the embodiment of the present application can convert the capacitor voltage signal ucFed into a predetermined fundamental wave signal extractor, GfundAnd(s) is the time domain transfer function of the fundamental wave signal extractor.
As a specific embodiment, in the method for identifying a resonant frequency of a grid-connected converter device provided in the embodiment of the present application, on the basis of the above contents, an output expression of a first preset identification controller of two preset identification controllers is as follows:
Figure BDA0002518563580000102
wherein x isiden1A first identification variable value output by the first preset identification controller; u. ofc_flucIs a fluctuation component signal, is inputted to the first predetermined identification controller.
Giden1(s) is the time domain transfer function of the first predetermined identification controller, with two important parameters: the preset bandwidth omega of the first preset identification controllerc1(ii) a Center frequency omega of first preset identification controllerf1。
Wherein, ω isf1For variable parameters, adjustments may be made specifically based on two other parameters: center frequency mean value omegaf0(ii) a Presetting a frequency increment value delta omegaf。
The output expression of the second preset identification controller is as follows:
Figure BDA0002518563580000103
wherein x isiden2A second identification variable value output by a second preset identification controller; based on the fluctuation component signal u input to the second predetermined recognition controllerc_flucAnd the acquisition is calculated.
Giden2(s) is the time domain transfer function of the second predetermined identification controller, and Giden1(s) are structurally identical, again with two important parameters: the preset bandwidth ω of the second preset identification controllerc2(ii) a Center frequency omega of second preset identification controllerf2。
Wherein, ω isf2For variable parameters, adjustments may be made specifically based on two other parameters: center frequency mean value omegaf0(ii) a Presetting a frequency increment value delta omegaf。
The preset bandwidths of the two preset identification controllers are taken to be the same value, namely omegac1＝ωc2＝ωcThus, the two predetermined identification controllers differ only in the center frequency.
Specifically, in order to facilitate determining the average value of the center frequencies of two preset identification controllers, the present embodiment introduces a parameter ω when calculating the adjustment center frequencyf0And Δ ωfAnd the difference sum of the two parameters is respectively used as the center frequency of two preset identification controllers. From this, it can be found that (ω)f2+ωf2)/2＝ωf0I.e. the center frequency mean value omega during the entire adjustment processf0The average of the two center frequencies is shown. Thus, in step S105, the center frequency intermediate value ω is directly obtainedf0The average of the two center frequencies can be determined.
As a specific embodiment, the method for identifying a resonant frequency of a grid-connected converter device provided in the embodiment of the present application, based on the above contents, performs PI control based on a difference between two identification variable values to adjust center frequencies of two preset identification controllers in real time until a closed loop steady state is entered, including:
calculating PI control quantity based on the difference value of the two identification variable values according to a preset PI control formula; the preset PI control formula is as follows:
Figure BDA0002518563580000111
wherein, Δ ωPIIs PI controlled variable; kPIs a preset proportionality coefficient; kIIs a preset integral coefficient; e.g. of the typePIIs the difference between the two identification variable values;
according to a preset frequency adjustment formula, based on a PI control quantity delta omegaPIUpdating center frequency median value omegaf0So as to be based on the center frequency median value ωf0Updating the center frequencies of two preset identification controllers; the preset frequency adjustment formula is as follows:
Figure BDA0002518563580000112
wherein the content of the first and second substances,
Figure BDA0002518563580000113
L1the inductance value is the inductance value of the grid-connected converter equipment side of the LCL filter;
Figure BDA0002518563580000121
ωres_midpresetting a reference value for the resonant frequency; l is2A grid side inductance value of the LCL filter; cfIs the capacitance value of the LCL filter; l isgIs the grid inductance.
In particular, due to the grid impedance LgDifferent impedance values appear along with different power grid strengths, and the value range is Lg∈ [0, ∞) ] and accordingly, the range of the resonant frequency can be obtained, and in order to improve the identification efficiency, the embodiment selects the predetermined reference value ω for the resonant frequency in advanceres_midSo as to be at a preset reference value omegares_midOn the basis of the central frequency, calculating the adjusted central frequency intermediate value omegaf0Accelerating to enter a closed loop steady state.
Referring to fig. 3, fig. 3 is a schematic diagram of a resonant frequency identification method of a grid-connected converter device according to an embodiment of the present disclosure.
As shown in fig. 3, the capacitor voltage signal ucAfter acquisition, the signal is sent to a fundamental wave signal extractor to extract a fundamental wave signal uc_fund. Converting the capacitor voltage signal ucSubtracting the fundamental signal uc_fundObtaining a fluctuation component signal uc_fluc. Utilizing a first preset identification controller and a second preset identification controller respectively according to the fluctuation component signal uc_flucRecognizing and generating first recognition variable value xiden1And a second identification variable value xiden2Then, the difference between the two identification variable values is sent to a PI controller to calculate the PI control quantity delta omegaPIAnd further control quantity Δ ω according to PIPIAdjusting the center frequency mean value omegaf0And feeding back the adjusted center frequency intermediate value to two preset identification controllers to adjust two preset identificationsAnd identifying the respective central frequencies of the controllers until a closed loop steady state is reached.
Theoretically, the resonant frequency to be identified is an average value of two center frequencies in a closed loop steady state, i.e. a center frequency median:
Figure BDA0002518563580000122
wherein, ω isresIs the resonant frequency.
As a specific embodiment, on the basis of the above, an average value of the center frequencies of the two preset identification controllers in the closed loop steady state is determined to be used as the resonant frequency ω of the grid-connected converter deviceresIn addition, appropriate optimization processing can be performed:
approximately calculating the average value according to a preset calculation formula to serve as the resonant frequency omega of the grid-connected converter equipmentresThe preset calculation formula is as follows:
Figure BDA0002518563580000123
specifically, the embodiment considers the requirements of practical engineering application, K in closed loop steady statePePIThe value of (A) is very small, close to zero, and the influence on the identification precision can be ignored, but the value is usually a slightly jittered value in practical engineering application, and the stability of the result is easily influenced. Therefore, in the present embodiment, when the identified resonant frequency is finally outputted, the proportional term, i.e. K, can be usedPePIRemoved and only the integral term remains.
Referring to fig. 4, an embodiment of the present application discloses a resonant frequency identification device for a grid-connected converter device, where the grid-connected converter device includes an LCL filter, and the device mainly includes:
an obtaining unit 201, configured to obtain a capacitance voltage signal of the LCL filter;
an extracting unit 202 for extracting a fluctuation component signal of the capacitance voltage signal;
the identification unit 203 is used for respectively sending the fluctuation component signals to two preset identification controllers with the same structure and different center frequencies to obtain two output identification variable values;
the adjusting unit 204 is used for performing PI control based on the difference value of the two identification variable values so as to adjust the central frequencies of the two preset identification controllers in real time until the closed loop stable state is reached;
the determining unit 205 is configured to determine an average value of center frequencies of the two preset identification controllers in a closed-loop steady state, as a resonant frequency of the grid-connected converter device.
Therefore, the resonant frequency identification device for the grid-connected converter equipment, disclosed by the embodiment of the application, can effectively track and identify the resonant frequency of the grid-connected converter equipment by utilizing the frequency characteristics of the identification results of the two preset identification controllers with the same structure and different center frequencies and combining PI closed-loop control, and the whole processing process does not need a large amount of data calculation, so that the identification accuracy is guaranteed, the identification rate and the real-time performance are effectively improved, and the resonant frequency can be accurately identified on line in real time to guarantee the resonance inhibition effect.
For specific content of the resonant frequency identification device of the grid-connected converter device, reference may be made to the foregoing detailed description of the resonant frequency identification method of the grid-connected converter device, and details thereof are not repeated here.
As a specific embodiment, on the basis of the foregoing content, the extraction unit 202 of the resonant frequency identification device of a grid-connected converter device disclosed in the embodiment of the present application is specifically configured to:
extracting a fundamental wave signal of the capacitor voltage signal; converting the capacitor voltage signal ucThe difference from the fundamental wave signal is taken as a fluctuation component signal.
As a specific embodiment, on the basis of the foregoing content, the extraction unit 202 of the resonant frequency identification device of a grid-connected converter device disclosed in the embodiment of the present application is specifically configured to:
extracting a fundamental wave signal according to a preset fundamental wave signal extraction formula, wherein the preset fundamental wave signal extraction formula is as follows:
Figure BDA0002518563580000131
wherein u isc_fundIs a fundamental wave signal; u. ofcIs a capacitance voltage signal; k is a radical offundIs an extraction coefficient; omegafundIs the fundamental angular frequency.
As a specific embodiment, in the resonant frequency identification device of a grid-connected converter device disclosed in the embodiment of the present application, on the basis of the above contents, an output expression of a first preset identification controller of two preset identification controllers is as follows:
Figure BDA0002518563580000141
wherein x isiden1A first identification variable value output by the first preset identification controller; u. ofc_flucIs a fluctuating component signal; omegac1A preset bandwidth for the first preset identification controller; omegaf1Identifying the center frequency of the controller for the first preset; omegaf0Is the center frequency median; Δ ωfIs a preset frequency increment value;
the output expression of the second preset identification controller is as follows:
Figure BDA0002518563580000142
wherein x isiden2A second identification variable value output by a second preset identification controller; omegac2A preset bandwidth for a second preset identification controller; omegaf2The center frequency of the second predetermined identification controller.
As a specific embodiment, on the basis of the foregoing content, the adjusting unit 204 of the resonant frequency identification device of a grid-connected converter device disclosed in the embodiment of the present application is specifically configured to:
calculating PI control quantity based on the difference value of the two identification variable values according to a preset PI control formula; the preset PI control formula is as follows:
Figure BDA0002518563580000143
wherein, Δ ωPIIs PI controlled variable; kPIs a preset proportionality coefficient; kIIs a preset integral coefficient; e.g. of the typePIIs the difference between the two identification variable values;
updating a center frequency intermediate value based on the PI control quantity according to a preset frequency adjustment formula so as to update the center frequencies of two preset identification controllers based on the center frequency intermediate value; the preset frequency adjustment formula is as follows:
Figure BDA0002518563580000144
wherein the content of the first and second substances,
Figure BDA0002518563580000151
ωres_midpresetting a reference value for the resonant frequency;
Figure BDA0002518563580000152
L1the inductance value is the inductance value of the grid-connected converter equipment side of the LCL filter; l is2A grid side inductance value of the LCL filter; cfIs the capacitance value of the LCL filter; l isgIs the grid inductance.
As a specific embodiment, the resonant frequency identification apparatus of a grid-connected converter device disclosed in the embodiment of the present application is based on the above contents, and the determining unit 205 is specifically configured to:
and (3) approximately calculating the average value according to a preset calculation formula as the resonant frequency of the grid-connected converter equipment, wherein the preset calculation formula is as follows:
Figure BDA0002518563580000153
wherein, ω isresIs the resonant frequency.
Referring to fig. 5, an embodiment of the present application discloses an electronic device, including:
a memory 301 for storing a computer program;
a processor 302 for executing the computer program to implement the steps of any one of the above-mentioned methods for identifying a resonant frequency of a grid-connected inverter device.
Further, the embodiment of the present application also discloses a computer-readable storage medium, in which a computer program is stored, and the computer program is used for implementing the steps of any one of the above-mentioned methods for identifying a resonant frequency of a grid-connected converter device when being executed by a processor.
For the specific content of the electronic device and the computer-readable storage medium, reference may be made to the foregoing detailed description of the method for identifying a resonant frequency of a grid-connected converter device, and details thereof are not repeated here.
The embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the equipment disclosed by the embodiment, the description is relatively simple because the equipment corresponds to the method disclosed by the embodiment, and the relevant parts can be referred to the method part for description.
It is further noted that, throughout this document, relational terms such as "first" and "second" are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Furthermore, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The technical solutions provided by the present application are described in detail above. The principles and embodiments of the present application are explained herein using specific examples, which are provided only to help understand the method and the core idea of the present application. It should be noted that, for those skilled in the art, without departing from the principle of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall into the protection scope of the present application.

Claims (10)

1. A method for identifying resonant frequency of grid-connected converter equipment is characterized in that the grid-connected converter equipment comprises an LCL filter, and the method comprises the following steps:
acquiring a capacitance voltage signal of the LCL filter;
extracting a fluctuation component signal of the capacitance voltage signal;
respectively sending the fluctuation component signals to two preset identification controllers with the same structure and different center frequencies to obtain two output identification variable values;
performing PI control based on the difference value of the two identification variable values to adjust the center frequencies of the two preset identification controllers in real time until the closed loop stable state is achieved;
and determining the average value of the central frequencies of the two preset identification controllers in the closed loop steady state as the resonant frequency of the grid-connected converter equipment.
2. The method for identifying resonant frequency according to claim 1, wherein said extracting a fluctuation component signal of the capacitance voltage signal comprises:
extracting a fundamental wave signal of the capacitance voltage signal;
and taking the difference value of the capacitance voltage signal and the fundamental wave signal as the fluctuation component signal.
3. The method according to claim 2, wherein the extracting a fundamental wave signal of the capacitance voltage signal comprises:
extracting the fundamental wave signal according to a preset fundamental wave signal extraction formula, wherein the preset fundamental wave signal extraction formula is as follows:
Figure FDA0002518563570000011
wherein u isc_fundIs the fundamental wave signal; u. ofcIs the capacitance voltage signal; k is a radical offundIs an extraction coefficient; omegafundIs the fundamental angular frequency.
4. The method according to any one of claims 1 to 3, wherein the output expression of the first one of the two predetermined identification controllers is:
Figure FDA0002518563570000012
wherein x isiden1A first identification variable value output by the first preset identification controller; u. ofc_flucIs the fluctuating component signal; omegac1A preset bandwidth for the first preset identification controller; omegaf1Identifying the center frequency of the first preset identification controller; omegaf0Is the center frequency median; Δ ωfIs a preset frequency increment value;
the output expression of the second preset identification controller is as follows:
Figure FDA0002518563570000021
wherein x isiden2A second identification variable value output by the second preset identification controller; omegac2The preset bandwidth of the second preset identification controller; omegaf2The center frequency of the second preset identification controller.
5. The method for identifying resonant frequency according to claim 4, wherein the PI controlling based on the difference between the two identification variable values to adjust the center frequencies of the two preset identification controllers in real time until a closed loop steady state is entered comprises:
calculating PI control quantity based on the difference value of the two identification variable values according to a preset PI control formula; the preset PI control formula is as follows:
Figure FDA0002518563570000022
wherein, Δ ωPIThe PI control quantity is the PI control quantity; kPIs a preset proportionality coefficient; kIIs a preset integral coefficient; e.g. of the typePIIs the difference between the two identifying variable values;
updating the center frequency intermediate value based on the PI control quantity according to a preset frequency adjustment formula so as to update the center frequencies of the two preset identification controllers based on the center frequency intermediate value; the preset frequency adjustment formula is as follows:
Figure FDA0002518563570000023
wherein the content of the first and second substances,
Figure FDA0002518563570000024
ωres_midpresetting a reference value for the resonant frequency;
Figure FDA0002518563570000025
L1the inductance value of the grid-connected converter equipment side of the LCL filter is obtained; l is2A grid side inductance value for the LCL filter; cfIs the capacitance value of the LCL filter; l isgIs the grid inductance.
6. The method for identifying the resonant frequency of claim 5, wherein the determining an average value of the center frequencies of the two preset identification controllers in the closed-loop steady state as the resonant frequency of the grid-connected converter device includes:
and approximately calculating the average value as the resonant frequency of the grid-connected converter equipment according to a preset calculation formula, wherein the preset calculation formula is as follows:
Figure FDA0002518563570000031
wherein, ω isresIs the resonance frequency.
7. The resonant frequency identification device of the grid-connected converter equipment is characterized in that the grid-connected converter equipment comprises an LCL filter, and the device comprises:
the acquisition unit is used for acquiring a capacitance voltage signal of the LCL filter;
an extraction unit for extracting a fluctuation component signal of the capacitance voltage signal;
the identification unit is used for respectively sending the fluctuation component signals to two preset identification controllers with the same structure and different center frequencies so as to obtain two output identification variable values;
the adjusting unit is used for carrying out PI control on the basis of the difference value of the two identification variable values so as to adjust the central frequencies of the two preset identification controllers in real time until the closed loop stable state is achieved;
and the determining unit is used for determining the average value of the central frequencies of the two preset identification controllers in the closed loop steady state as the resonant frequency of the grid-connected converter equipment.
8. The apparatus for identifying a resonant frequency of claim 7, wherein the extracting unit is specifically configured to:
extracting a fundamental wave signal of the capacitance voltage signal; and taking the difference value of the capacitance voltage signal and the fundamental wave signal as the fluctuation component signal.
9. An electronic device, comprising:
a memory for storing a computer program;
a processor for executing the computer program to implement the steps of the method for identifying a resonant frequency of a grid-connected inverter device as claimed in any one of claims 1 to 6.
10. A computer-readable storage medium, in which a computer program is stored, which, when being executed by a processor, is configured to implement the steps of the method for identifying a resonant frequency of a grid-connected converter device according to any one of claims 1 to 6.
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