CN114564821B - Grid-connected inverter impedance modeling method based on single-phase disturbance injection - Google Patents

Grid-connected inverter impedance modeling method based on single-phase disturbance injection Download PDF

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CN114564821B
CN114564821B CN202210091536.3A CN202210091536A CN114564821B CN 114564821 B CN114564821 B CN 114564821B CN 202210091536 A CN202210091536 A CN 202210091536A CN 114564821 B CN114564821 B CN 114564821B
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CN114564821A (en
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赵静波
马俊鹏
王顺亮
刘天琪
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Sichuan University
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • 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
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/493—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode the static converters being arranged for operation in parallel
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2113/00—Details relating to the application field
    • G06F2113/04—Power grid distribution networks
    • 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
    • H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
    • 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]
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    • 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

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Abstract

The invention discloses a grid-connected inverter impedance modeling method based on single-phase disturbance injection, which specifically comprises the following steps: analyzing harmonic response frequency generated after single-phase disturbance is injected into an alternating current power grid by considering phase-locked loop frequency coupling response; representing positive and negative order harmonic responses at the PCC using a fast Fourier transform and an alpha beta coordinate system; and optimizing the frequency point selection value and the number of the single-phase disturbance injection according to different coupling harmonic conditions. The invention provides the impedance modeling method based on single-phase disturbance injection, which reduces the complexity and the required capacity of impedance measurement equipment, reduces the volume of the equipment and improves the accuracy of impedance modeling.

Description

Grid-connected inverter impedance modeling method based on single-phase disturbance injection
Technical Field
The invention belongs to the field of converter modeling, and particularly relates to a grid-connected inverter impedance modeling method based on single-phase disturbance injection.
Background
Impedance modeling has become an important tool for stability analysis of converter-grid interconnection systems. The impedance model is built by measuring the impedance values of the grid-connected inverter under different frequencies through a mathematical method, however, the traditional three-phase impedance measurement method requires that the impedance measurement transpose has large capacity and volume, which brings about higher cost and energy consumption. The single-phase disturbance injection method only needs to carry out one-time frequency sweep, frequency sweep times are reduced, and the single-phase disturbance injection method only needs to inject harmonic waves through the single-phase inverter, so that the complexity of the harmonic generation device is reduced, single-time energy consumption is reduced, and the economical efficiency and the practicability are improved. The existing impedance calculation method considering frequency coupling needs to change the impedance of a power grid, and the operation is likely to change the operating point of the system, and is complex in operation and unfavorable for practical use.
Disclosure of Invention
In order to reduce the volume and energy consumption of the grid-connected inverter impedance measurement device and ensure the accuracy of measurement results, the invention provides a grid-connected inverter impedance modeling method based on single-phase disturbance injection.
The invention discloses a grid-connected inverter impedance modeling method based on single-phase disturbance injection, which comprises the following steps of:
step 1: and calculating the harmonic frequency generated by three phases after disturbance is injected into the alternating-current side single phase of the grid-connected inverter.
After the A-phase injection voltage disturbance at the alternating current side of the grid-connected inverter, the three-phase alternating current voltage signal is expressed as:
Wherein, V 1 is the power grid voltage amplitude, V p is the disturbance voltage amplitude, omega 0 is the power grid voltage angular frequency, omega p is the disturbance voltage angular frequency, and theta p is the disturbance voltage initial phase.
The three-phase alternating voltage signal is converted into dq:
wherein θ s is the phase of the phase locked loop output.
The formula (2) is expressed as a complex variable form:
Form e jx =cos x+ jsin x is euler transformation, the small disturbance voltage signal is subjected to dq transformation, only q-axis component causes the disturbance quantity of delta theta generated by the output phase theta s of the phase-locked loop, and the transfer function of the phase-locked loop is as follows:
Wherein k pp is a phase-locked loop proportional coefficient, k pi is a phase-locked loop integral coefficient, and after phase angle disturbance is introduced due to the influence of phase-locked loop and Park conversion:
θ＝ω0t+Δθ (5)
substituting the formula (5) into the formula (3) and performing linearization to obtain the following components:
Equation (6) is converted into:
wherein, The imaginary part of (a) is-jV 1 Deltaθ, complex variable/>Combining equation (4) and equation (5) yields:
obtained according to formulas (6), (7) and (8):
As can be seen from equation (9), due to the effect of the phase-locked loop, a single-phase voltage disturbance with frequency ω p is input, four frequency responses (ω p-ω0)、(ω0-ωp)、(ω0+ωp) and (- ω 0-ωp) are generated in the dq coordinate system, and converted into three-phase coordinate systems, and the four frequencies become ω p、(2ω0-ωp)、(2ω0+ωp) and- ω p, which are the single-input multiple-output phenomenon generated by frequency coupling caused by the phase-locked loop.
Step 2: and injecting voltage (or current) disturbance with different frequencies into any one phase of the alternating current side of the grid-connected inverter, extracting voltage and current at a common point (point of common coupling, PCC), and obtaining three-phase positive and negative sequence subharmonic amplitude values by adopting fast Fourier transform (fast fourier transform, FFT).
After single-phase injection voltage disturbance, extracting three-phase voltage and current signals at PCC, obtaining voltage and current signals v α、vβ,iα、iβ under an alpha beta coordinate system through Clark conversion, and obtaining positive and negative sequence harmonic waves of the voltage and the current through FFT analysis:
Wherein v p、ip is positive sequence voltage and current harmonic, v n、in is negative sequence voltage and current harmonic, Representing the component with angular frequency ω after fourier transformation.
Step 3: according to the obtained amplitude of each subharmonic, obtaining self-impedance and transimpedance which consider frequency coupling;
the self-impedance expression of the grid-connected inverter is as follows:
Wherein Z s is the self-impedance of the grid-connected inverter, Z a is the mutual impedance of the grid-connected inverter, Y s is the self-admittance of the grid-connected inverter, and Y a is the mutual admittance of the grid-connected inverter.
Y s and Y a are calculated from formula (12):
Wherein Y s(ωp) represents the self-admittance of the grid-connected inverter at the frequency of the injection disturbance frequency omega p, Y a(ωc) represents the mutual admittance of the grid-connected inverter at the coupling frequency omega c at the frequency of the injection disturbance frequency, Y a(ωp)* represents the conjugation of the mutual admittance of the grid-connected inverter at the frequency of the injection disturbance frequency omega p, Y s(ωc)* represents the self-admittance of the grid-connected inverter at the coupling frequency omega c at the frequency of the injection disturbance frequency, Component of response current at omega p of grid-connected inverter port after single-phase disturbance representing injection frequency omega p,/>Component of response current at omega p of grid-connected inverter port after single-phase disturbance representing coupling frequency with injection frequency of omega p,/>Conjugation of coupling frequency omega c component of response current of grid-connected inverter port after single-phase disturbance representing injection frequency omega p at omega p,/>Component of response current at omega c of grid-connected inverter port after single-phase disturbance representing coupling frequency with injection frequency of omega p,/>Component of response voltage of grid-connected inverter port at omega p after single-phase disturbance representing injection frequency omega p,/>Component of response voltage of grid-connected inverter port at omega p after single-phase disturbance representing coupling frequency with injection frequency of omega p,/>Conjugation of coupling frequency omega c component of response voltage of grid-connected inverter port after single-phase disturbance representing injection frequency omega p at omega p,/>A component of the response voltage at ω c of the grid-tie inverter port after single-phase disturbance representing the coupling frequency at ω p is injected.
When the injection disturbance frequency ω p is less than 2ω 0, the coupling frequency harmonic should be 2ω 0-ωp component of the positive sequence component; when the injection disturbance frequency ω p is greater than 2ω 0, the coupling frequency harmonic should be a 2ω 0-ωp component of the negative sequence component;
in impedance scanning, small disturbance signals with the frequency omega p and the coupling frequency |2ω 0-ωp | are required to be respectively injected, and harmonic components with the frequency omega p and the corresponding coupling frequency are extracted from the obtained voltage and current at the PCC.
The specific classification is as follows:
when the preset frequency is omega p less than 2 omega 0:
(1) Injecting a small disturbance signal with the frequency of omega p into any one phase of the alternating current side of the grid-connected inverter;
(2) Extracting positive sequence voltage and current harmonic components with frequencies of omega p and 2 omega 0-ωp at PCC;
(3) Injecting a small disturbance signal with the frequency of 2ω 0-ωp into any one phase of the alternating current side of the grid-connected inverter;
(4) Positive sequence voltage and current harmonic components at PCC frequency omega p and 2 omega 0-ωp are extracted.
When the preset frequency is omega p greater than 2 omega 0:
(1) Injecting a small disturbance signal with the frequency of omega p into any one phase of the alternating current side of the grid-connected inverter;
(2) Extracting positive sequence voltage and current harmonic components with the frequency of omega p and negative sequence voltage and current harmonic components with the frequency of omega p-2ω0 at the PCC;
(3) Injecting a small disturbance signal with the frequency of omega p-2ω0 into any one phase of the alternating current side of the grid-connected inverter;
(4) Positive sequence voltage and current harmonic components with the frequency omega p and negative sequence voltage and current harmonic components with the frequency omega p-2ω0 at the PCC are extracted.
The beneficial technical effects of the invention are as follows:
According to the invention, under the condition of considering frequency coupling of the phase-locked loop, the modeling method capable of reducing the volume of the impedance measuring device and not changing the impedance of the power grid is provided, response harmonic conditions generated by single-phase injection disturbance in a three-phase system are analyzed, the harmonic component extraction method when injection disturbance frequencies are different is illustrated, disturbance injection times are reduced, energy consumption during impedance measurement is reduced, and modeling precision is improved.
Drawings
FIG. 1 is a block diagram of a grid-connected inverter impedance measurement system according to the present invention;
FIG. 2 is a graph comparing the modeling results of the self-impedance and the transadmittance of the grid-connected inverter with the sweep frequency results.
Detailed Description
The invention will be described in further detail with reference to the drawings and the detailed description.
In the figure 1, an impedance and an ideal three-phase power supply are used for simulating an alternating current power grid, a direct current side is equivalent to a direct current voltage source, three-phase voltage and current responses are extracted from a PCC, three-phase voltage and current information of harmonic components with required frequency is obtained through a data preprocessing module, and a grid-connected inverter impedance model is obtained through a data computing module.
The invention discloses a grid-connected inverter impedance modeling method based on single-phase disturbance injection, which comprises the following steps of:
step 1: and calculating the harmonic frequency generated by three phases after disturbance is injected into the alternating-current side single phase of the grid-connected inverter.
After the A-phase injection voltage disturbance at the alternating current side of the grid-connected inverter, the three-phase alternating current voltage signal is expressed as:
Wherein, V 1 is the power grid voltage amplitude, V p is the disturbance voltage amplitude, omega 0 is the power grid voltage angular frequency, omega p is the disturbance voltage angular frequency, and theta p is the disturbance voltage initial phase.
The three-phase alternating voltage signal is converted into dq:
wherein θ s is the phase of the phase locked loop output.
The formula (2) is expressed as a complex variable form:
The form e jx =cos x+ jsin x is euler transformation, the small disturbance voltage signal is subjected to dq transformation, only q-axis component causes the output phase θ s of the phase-locked loop to generate the disturbance quantity of Δθ, and the transfer function of the phase-locked loop is as follows:
Wherein k pp is a phase-locked loop proportional coefficient, k pi is a phase-locked loop integral coefficient, and after phase angle disturbance is introduced due to the influence of phase-locked loop and Park conversion:
θ＝ω0t+Δθ (5)
substituting the formula (5) into the formula (3) and performing linearization to obtain the following components:
Equation (6) is converted into:
wherein, The imaginary part of (a) is-jV 1 Deltaθ, complex variable/>Combining equation (4) and equation (5) yields:
obtained according to formulas (6), (7) and (8):
As can be seen from equation (9), due to the effect of the phase-locked loop, a single-phase voltage disturbance with frequency ω p is input, four frequency responses (ω p-ω0)、(ω0-ωp)、(ω0+ωp) and (- ω 0-ωp) are generated in the dq coordinate system, and converted into three-phase coordinate systems, and the four frequencies become ω p、(2ω0-ωp)、(2ω0+ωp) and- ω p, which are the single-input multiple-output phenomenon generated by frequency coupling caused by the phase-locked loop.
Step 2: and injecting voltage (or current) disturbance with different frequencies into any one phase of the alternating current side of the grid-connected inverter, extracting voltage and current at a common point (point of common coupling, PCC), and obtaining three-phase positive and negative sequence subharmonic amplitude values by adopting fast Fourier transform (fast fourier transform, FFT).
After single-phase injection voltage disturbance, extracting three-phase voltage and current signals at PCC, obtaining voltage and current signals v α、vβ,iα、iβ under an alpha beta coordinate system through Clark conversion, and obtaining positive and negative sequence harmonic waves of the voltage and the current through FFT analysis:
Wherein v p、ip is positive sequence voltage and current harmonic, and v n、in is negative sequence voltage and current harmonic.
Step 3: according to the obtained amplitude of each subharmonic, obtaining self-impedance and transimpedance which consider frequency coupling;
the self-impedance expression of the grid-connected inverter is as follows:
Wherein Z s is the self-impedance of the grid-connected inverter, Z a is the mutual impedance of the grid-connected inverter, Y s is the self-admittance of the grid-connected inverter, and Y a is the mutual admittance of the grid-connected inverter.
Y s and Y a are calculated from formula (12):
Wherein Y s(ωp) represents the self-admittance of the grid-connected inverter at the frequency of the injection disturbance frequency omega p, Y a(ωc) represents the mutual admittance of the grid-connected inverter at the coupling frequency omega c at the frequency of the injection disturbance frequency, Y a(ωp)* represents the conjugation of the mutual admittance of the grid-connected inverter at the frequency of the injection disturbance frequency omega p, Y s(ωc)* represents the self-admittance of the grid-connected inverter at the coupling frequency omega c at the frequency of the injection disturbance frequency, Component of response current at omega p of grid-connected inverter port after single-phase disturbance representing injection frequency omega p,/>Component of response current at omega p of grid-connected inverter port after single-phase disturbance representing coupling frequency with injection frequency of omega p,/>Conjugation of coupling frequency omega c component of response current of grid-connected inverter port after single-phase disturbance representing injection frequency omega p at omega p,/>Component of response current at omega c of grid-connected inverter port after single-phase disturbance representing coupling frequency with injection frequency of omega p,/>Component of response voltage of grid-connected inverter port at omega p after single-phase disturbance representing injection frequency omega p,/>Component of response voltage of grid-connected inverter port at omega p after single-phase disturbance representing coupling frequency with injection frequency of omega p,/>Conjugation of coupling frequency omega c component of response voltage of grid-connected inverter port after single-phase disturbance representing injection frequency omega p at omega p,/>A component of the response voltage at ω c of the grid-tie inverter port after single-phase disturbance representing the coupling frequency at ω p is injected.
When the injection disturbance frequency ω p is less than 2ω 0, the coupling frequency harmonic should be 2ω 0-ωp component of the positive sequence component; when the injection disturbance frequency ω p is greater than 2ω 0, the coupling frequency harmonic should be a 2ω 0-ωp component of the negative sequence component;
in impedance scanning, small disturbance signals with the frequency omega p and the coupling frequency |2ω 0-ωp | are required to be respectively injected, and harmonic components with the frequency omega p and the corresponding coupling frequency are extracted from the obtained voltage and current at the PCC.
The specific classification is as follows:
when the preset frequency is omega p less than 2 omega 0:
(1) Injecting a small disturbance signal with the frequency of omega p into any one phase of the alternating current side of the grid-connected inverter;
(2) Extracting positive sequence voltage and current harmonic components with frequencies of omega p and 2 omega 0-ωp at PCC;
(3) Injecting a small disturbance signal with the frequency of 2ω 0-ωp into any one phase of the alternating current side of the grid-connected inverter;
(4) Positive sequence voltage and current harmonic components at PCC frequency omega p and 2 omega 0-ωp are extracted.
When the preset frequency is omega p greater than 2 omega 0:
(1) Injecting a small disturbance signal with the frequency of omega p into any one phase of the alternating current side of the grid-connected inverter;
(2) Extracting positive sequence voltage and current harmonic components with the frequency of omega p and negative sequence voltage and current harmonic components with the frequency of omega p-2ω0 at the PCC;
(3) Injecting a small disturbance signal with the frequency of omega p-2ω0 into any one phase of the alternating current side of the grid-connected inverter;
(4) Positive sequence voltage and current harmonic components with the frequency omega p and negative sequence voltage and current harmonic components with the frequency omega p-2ω0 at the PCC are extracted.
Fig. 2 is a graph of comparing calculated values and measured values of the amplitude and the phase of the self-admittance and the mutual admittance of the grid-connected inverter, the graph (a) and the graph (d) are graphs of the amplitude and the phase of the self-admittance, the graph (b) and the graph (c) are graphs of the amplitude and the phase of the mutual admittance, the solid line is a theoretical value admittance curve calculated according to an admittance expression, the scattered point is an admittance value corresponding to each frequency obtained through actual measurement, and it can be seen that the measured values and the calculated values of the admittance of the grid-connected inverter are consistent, and the accuracy of the method is higher.

Claims (2)

1. A grid-connected inverter impedance modeling method based on single-phase disturbance injection is characterized by comprising the following steps:
step 1: calculating harmonic frequency generated by three phases after disturbance is injected into a single phase at an alternating current side of the grid-connected inverter;
After the A-phase injection voltage disturbance at the alternating current side of the grid-connected inverter, the three-phase alternating current voltage signal is expressed as:
Wherein, V 1 is the power grid voltage amplitude, V p is the disturbance voltage amplitude, omega 0 is the power grid voltage angular frequency, omega p is the disturbance voltage angular frequency, theta p is the disturbance voltage initial phase, and t is time;
the three-phase alternating voltage signal is converted into dq:
Wherein θ s is the phase of the phase locked loop output;
The formula (2) is expressed as a complex variable form:
The form e jx = cosx + jsinx is euler transformation, the small disturbance voltage signal is subjected to dq transformation, only q-axis component causes the output phase θ s of the phase-locked loop to generate the disturbance quantity of Δθ, and the transfer function of the phase-locked loop is as follows:
Wherein k pp is a phase-locked loop proportional coefficient, k pi is a phase-locked loop integral coefficient, and after phase angle disturbance is introduced due to the influence of phase-locked loop and Park conversion:
θ＝ω0t+Δθ (5)
substituting the formula (5) into the formula (3) and performing linearization to obtain the following components:
Equation (6) is converted into:
wherein, The imaginary part of (a) is-jV 1 Deltaθ, complex variable/>Combining equation (4) and equation (5) yields:
obtained according to formulas (6), (7) and (8):
As can be seen from equation (9), due to the effect of the phase-locked loop, a single-phase voltage disturbance with frequency ω p is input, four frequency responses (ω p-ω0)、(ω0-ωp)、(ω0+ωp) and (- ω 0-ωp) are generated in the dq coordinate system, and converted into three-phase coordinate systems, and the four frequencies become ω p、(2ω0-ωp)、(2ω0+ωp) and- ω p;
Step 2: injecting voltage disturbance with different frequencies into any one phase of the alternating current side of the grid-connected inverter, extracting voltage and current at a common point PCC, and obtaining the amplitude of each subharmonic of the positive and negative sequences of the three phases by adopting fast Fourier transformation;
After single-phase injection voltage disturbance, extracting three-phase voltage and current signals at PCC, obtaining voltage and current signals v α、vβ,iα、iβ under an alpha beta coordinate system through Clark conversion, and obtaining positive and negative sequence harmonic waves of the voltage and the current through FFT analysis:
Wherein v p、ip is positive sequence voltage and current harmonic, v n、in is negative sequence voltage and current harmonic, A component representing angular frequency ω after fourier transform;
Step 3: according to the obtained amplitude of each subharmonic, obtaining self-impedance and transimpedance which consider frequency coupling;
the self-impedance expression of the grid-connected inverter is as follows:
Wherein Z s is the self-impedance of the grid-connected inverter, Z a is the mutual impedance of the grid-connected inverter, Y s is the self-admittance of the grid-connected inverter, and Y a is the mutual admittance of the grid-connected inverter;
Y s and Y a are calculated from formula (12):
Wherein Y s(ωp) represents the self-admittance of the grid-connected inverter at the frequency of the injection disturbance frequency omega p, Y a(ωc) represents the mutual admittance of the grid-connected inverter at the coupling frequency omega c at the frequency of the injection disturbance frequency, Y a(ωp)* represents the conjugation of the mutual admittance of the grid-connected inverter at the frequency of the injection disturbance frequency omega p, Y s(ωc)* represents the self-admittance of the grid-connected inverter at the coupling frequency omega c at the frequency of the injection disturbance frequency, Component of response current at omega p of grid-connected inverter port after single-phase disturbance representing injection frequency omega p,/>Component of response current at omega p of grid-connected inverter port after single-phase disturbance representing coupling frequency with injection frequency of omega p,/>Conjugation of coupling frequency omega c component of response current of grid-connected inverter port after single-phase disturbance representing injection frequency omega p at omega p,/>Component of response current at omega c of grid-connected inverter port after single-phase disturbance representing coupling frequency with injection frequency of omega p,/>Component of response voltage of grid-connected inverter port at omega p after single-phase disturbance representing injection frequency omega p,/>Component of response voltage of grid-connected inverter port at omega p after single-phase disturbance representing coupling frequency with injection frequency of omega p,/>Conjugation of coupling frequency omega c component of response voltage of grid-connected inverter port after single-phase disturbance representing injection frequency omega p at omega p,/>A component representing the response voltage of the grid-connected inverter port at omega c after single-phase disturbance of the coupling frequency with the injection frequency of omega p;
When the injection disturbance frequency ω p is less than 2ω 0, the coupling frequency harmonic should be 2ω 0-ωp component of the positive sequence component; when the injection disturbance frequency ω p is greater than 2ω 0, the coupling frequency harmonic should be a 2ω 0-ωp component of the negative sequence component;
in impedance scanning, small disturbance signals with the frequency omega p and the coupling frequency |2ω 0-ωp | are required to be respectively injected, and harmonic components with the frequency omega p and the corresponding coupling frequency are extracted from the obtained voltage and current at the PCC.
2. The method for modeling impedance of a grid-connected inverter based on single-phase disturbance injection according to claim 1, wherein different signals are required to be injected and extracted according to the magnitude relation between 2 ω 0 and ω p, and the method is classified as follows:
when the preset frequency is omega p less than 2 omega 0:
(1) Injecting a small disturbance signal with the frequency of omega p into any one phase of the alternating current side of the grid-connected inverter;
(2) Extracting positive sequence voltage and current harmonic components with frequencies of omega p and 2 omega 0-ωp at PCC;
(3) Injecting a small disturbance signal with the frequency of 2ω 0-ωp into any one phase of the alternating current side of the grid-connected inverter;
(4) Extracting positive sequence voltage and current harmonic components with frequencies of omega p and 2 omega 0-ωp at PCC;
when the preset frequency is omega p greater than 2 omega 0:
(1) Injecting a small disturbance signal with the frequency of omega p into any one phase of the alternating current side of the grid-connected inverter;
(2) Extracting positive sequence voltage and current harmonic components with the frequency of omega p and negative sequence voltage and current harmonic components with the frequency of omega p-2ω0 at the PCC;
(3) Injecting a small disturbance signal with the frequency of omega p-2ω0 into any one phase of the alternating current side of the grid-connected inverter;
(4) Positive sequence voltage and current harmonic components with the frequency omega p and negative sequence voltage and current harmonic components with the frequency omega p-2ω0 at the PCC are extracted.
CN202210091536.3A 2022-01-26 2022-01-26 Grid-connected inverter impedance modeling method based on single-phase disturbance injection Active CN114564821B (en)

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