CN110518581B - Inverter impedance optimization method considering sampling filtering phase-locked loop - Google Patents

Inverter impedance optimization method considering sampling filtering phase-locked loop Download PDF

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CN110518581B
CN110518581B CN201910766079.1A CN201910766079A CN110518581B CN 110518581 B CN110518581 B CN 110518581B CN 201910766079 A CN201910766079 A CN 201910766079A CN 110518581 B CN110518581 B CN 110518581B
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inverter
phase
impedance
voltage
locked loop
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CN110518581A (en
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朱淼
侯川川
徐莉婷
李铮钊
李渝
孙谊媊
张锋
王衡
亢朋朋
蔡旭
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Shanghai Jiaotong University
State Grid Xinjiang Electric Power Co Ltd
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State Grid Xinjiang Electric Power 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
    • H02J3/00—Circuit arrangements for ac mains or ac 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • 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
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    • 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 invention provides an inverter impedance optimization method considering a sampling filter phase-locked loop, which comprises the following steps of: according to the actual operation mode of the renewable energy grid-connected system, considering the influence of a voltage sampling filtering link on a phase-locked loop input signal, and establishing an impedance model of the inverter; and (3) optimizing an impedance model: and by combining the impedance model of the inverter and optimizing the parameters of the sampling filter, the filtering characteristic of voltage sampling is changed, the effectiveness of the input signal of the phase-locked loop is improved, and the impedance optimization of the output of the inverter is realized. According to the method, the influence of voltage sampling filtering on an original signal is considered for the operation characteristic of an actual inverter, and a grid-connected inverter impedance model containing a sampling filtering link is deduced by combining the parameter characteristic of a control loop; the component components of the original signal entering the phase-locked loop are changed by optimizing the parameters of sampling filtering, so that the impedance optimization is realized, the control parameters of the inverter multi-loop do not need to be modified, and the existing impedance optimization approach is widened.

Description

Inverter impedance optimization method considering sampling filtering phase-locked loop
Technical Field
The invention relates to the field of alternating current power transmission and distribution, in particular to an inverter impedance optimization method considering a sampling filter phase-locked loop.
Background
The direct current delivery system of the renewable energy power generation base comprises diversified equipment such as wind-solar power generation, reactive compensation, direct current transmission, a synchronous generator and the like, and the capacity of power electronic equipment is far larger than that of the synchronous generator. Due to the low effective inertia of the system, the small short circuit ratio and the weakened leading characteristic of the synchronous machine, the problems of frequent oscillation of a wide frequency band (several hertz to several hundred hertz) and the deterioration of transient stability during alternating current/direct current faults are caused. At present, nearly hundreds times/super-synchronous oscillation occurs in an already-put-into-operation Hami-Zheng State direct current sending end wind power base, and 3 660MW matched thermal power generating units are caused to trip in serious conditions, so that part of wind fields have to be operated in a power-down mode or shut down, and the maximum utilization of renewable energy is limited.
Aiming at the oscillation problem caused by renewable energy, a characteristic root analysis method, an impedance analysis method and a frequency domain relative gain matrix method are generally adopted, wherein the impedance analysis method is widely used, and the impedance of the grid-connected inverter near the oscillation frequency is optimized by controlling the output impedance characteristic of the renewable energy grid-connected device, so that the oscillation point is avoided and the aim of stably connecting the grid is fulfilled. The existing impedance optimization method mainly comprises phase-locked loop bandwidth optimization, current loop bandwidth optimization, voltage loop bandwidth optimization and voltage feedforward optimization, the optimization is based on an ideal model of an inverter, the output impedance of the inverter is obtained through a mathematical analytic expression, voltage sampling and filtering links in an actual system are not considered in the impedance modeling process, and the effect of the optimized theoretical impedance in actual operation cannot be completely reflected. In addition, the control optimization relates to the self stability of the grid-connected system, and in order to achieve the self stability and multiple control targets in the design process of the inverter, the parameter range which can be adjusted by the impedance optimization is limited.
In summary, although the existing impedance optimization method has a certain effect, the optimization strategy is limited to only part of control links, and the optimization effect is limited by multiple factors, so that the optimization method has a certain limitation. In order to be closer to an actual grid-connected system, the inverter output impedance model needs to consider a sampling filtering link, the influence of voltage sampling filtering on a phase-locked loop and an inverter is measured in impedance modeling, the inverter impedance is optimized by using the characteristic of a filter in optimization, and the adjustment of control parameters of each loop of the inverter is avoided.
In the prior art, the documents of direct-drive wind power plant subsynchronous oscillation analysis and phase-locked loop parameter optimization design based on sequence impedance disclose the following schemes: in recent years, the phenomenon of subsynchronous oscillation of a direct-drive wind power plant merged into an alternating current power grid occurs in northwest areas of China. In order to deeply research the problem, a harmonic linearization method is adopted in the text to establish a positive sequence impedance model and a negative sequence impedance model of a typical direct-drive wind turbine generator grid-side converter. Secondly, the impedance of the direct-drive wind turbine generator is measured by a hardware control in-loop method, the generation mechanism of subsynchronous oscillation of the direct-drive wind turbine generator and an alternating current power grid is analyzed by utilizing the Nyquist criterion, and a phase-locked loop control parameter optimization design method is provided, so that the risk of the subsynchronous oscillation of the system is reduced. And finally, establishing a wind power plant electromagnetic transient real-time simulation model consisting of 110 1.5MW direct-drive wind turbines based on an RT-lab real-time simulation platform, and verifying the correctness of theoretical analysis by using a simulation result.
The document establishes an impedance model of the inverter by using a harmonic linearization method, and compares an analytical model with an actual model by using a scanning impedance method, although the influence of a phase-locked loop and a current loop control parameter on the impedance model is considered. However, the impedance modeling of the document omits a sampling filtering link in the operation process of the inverter, and the correlation between the impedance model of the inverter and the filter characteristics is not completely reflected. Meanwhile, the document proposes to change the phase-locked loop bandwidth and current loop parameters on the basis of an impedance optimization method, so as to achieve the effect of oscillation suppression, the optimization is based on an ideal model of the inverter, the output impedance of the inverter is obtained through a mathematical analytic expression, the voltage sampling and filtering links in an actual system are not considered in the impedance modeling process, and the effect of the optimized theoretical impedance in actual operation cannot be completely reflected. In addition, the corresponding control parameter optimization relates to the self stability of the grid-connected system, and in order to achieve multiple control targets such as self stability and the like in the design process of the inverter, the parameter range which can be adjusted by impedance optimization is limited. The method firstly establishes an inverter impedance model containing a sampling filtering link, is close to the real operation scene of the inverter, provides an impedance optimization measure from the angle of a sampling filtering phase-locked loop, and widens the approach of impedance optimization.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide an inverter impedance optimization method considering a sampling filter phase-locked loop.
The invention provides an inverter impedance optimization method considering a sampling filter phase-locked loop, which comprises the following steps:
establishing an impedance model: according to the actual operation mode of the renewable energy grid-connected system, considering the influence of a voltage sampling filtering link on a phase-locked loop input signal, and establishing an impedance model of the inverter;
and (3) optimizing an impedance model: and by combining the impedance model of the inverter and optimizing the parameters of the sampling filter, the filtering characteristic of voltage sampling is changed, the effectiveness of the input signal of the phase-locked loop is improved, and the impedance optimization of the output of the inverter is realized.
Preferably, the impedance model establishing step includes:
carrying out harmonic linearization on a plurality of control loops in a frequency domain according to the topological characteristic of the inverter and the conditioning effect of sampling filtering on the input signal;
obtaining current response caused by power grid harmonic voltage disturbance in the inverter operation state by using the linearization result;
and deducing an inverter impedance model taking the sampling filter phase-locked loop into account.
Preferably, the impedance model establishing step includes:
calculating the total voltage of an outlet of the inverter:
when the inverter outlet voltage contains harmonic disturbance, (taking phase a as an example) the total outlet voltage is:
Figure BDA0002171977430000031
wherein: v. ofaIs a mouth A phase voltage instantaneous value, V1For the fundamental voltage amplitude, omega, at the outlet of the converter1At fundamental voltage angular frequency, VpIs the harmonic voltage amplitude, omegapIn order to be at the harmonic voltage angular frequency,
Figure BDA0002171977430000032
is the initial phase of the harmonic voltage;
calculating the phase angle output by the phase-locked loop:
θPLL＝θ0+Δθ
wherein: thetaPLLFor phase-locked loop output phase angle, theta0Is a fundamental voltage phase angle, and delta theta is a perturbation phase angle caused by harmonic voltage;
and a step of calculating a transfer function:
Figure BDA0002171977430000033
wherein: hPLLRepresenting a phase-locked loop transfer function;
a signal adjustment characteristic calculation step: the signal conditioning characteristics of the sampling filtering element can be represented by a filter as
Figure BDA0002171977430000034
Where m is the pass-band amplification factor,
Figure BDA0002171977430000035
is the center frequency;
calculating the dq axis current of the line: when the d axis of the inverter current is coincident with the positive sequence component of the fundamental wave of the grid voltage, the active current I at the outlet of the inverterdReactive current IqThe line dq axis current of which can be written as
Figure BDA0002171977430000036
In the formula: vpIs a harmonic voltage, IpIs harmonic current of the line, where D(s) ± jFp(s)，B(s±j2πf1) As a function of the filter characteristics at frequency offset;
calculating the voltage of the inverter port: the output quantity of the fundamental current of the converter is equal to the current reference value under the stable working state, and H in the current control loopi(s) constant value with Cd、CqVoltage E at inverter port representing the steady state value of the dq axis output, e.g. phase aaCan be written as
Figure BDA0002171977430000041
In the formula KdqIs a decoupling coefficient;
calculating an impedance model:
when the outlet voltage of the inverter is injected into the disturbance frequency, the impedance model analytic value Z between the harmonic voltage and the harmonic current output by the inverter is determined as
Figure BDA0002171977430000042
Preferably, the center frequency
Figure BDA0002171977430000043
The ratio of b to a of (a) is constant.
Preferably, the pass band amplification factor m is slightly varied and finely adjusted between 0.9 and 1.1.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the method, the influence of voltage sampling filtering on an original signal is considered for the operation characteristic of an actual inverter, and a grid-connected inverter impedance model containing a sampling filtering link is deduced by combining the parameter characteristic of a control loop;
2. the invention changes the component of each component of the original signal entering the phase-locked loop by optimizing the parameters of sampling filtering, thereby realizing impedance optimization, and the used impedance optimization method does not need to modify the control parameters of the inverter multi-loop, thereby widening the existing impedance optimization approach.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic diagram of a grid-connected system that takes into account a sampling filter phase-locked loop;
FIG. 2 is a graph of a frequency characteristic of a prior art inverter impedance model;
FIG. 3 is a graph of inverter impedance model frequency characteristics, accounting for a sampling filter phase locked loop;
fig. 4 is a graph of an inverter impedance optimized frequency characteristic that accounts for a sampling filter phase locked loop.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
In order to reduce potential oscillation risk caused by renewable energy grid connection, impedance optimization for a grid-connected inverter is an effective measure, but the existing inverter impedance model and impedance optimization method do not relate to a sampling filtering link. Firstly, according to the actual operation mode of a renewable energy grid-connected system, considering the influence of a voltage sampling filtering link on a phase-locked loop input signal, and establishing an impedance model of an inverter; and secondly, combining the impedance model, changing the filtering characteristic of voltage sampling by optimizing the parameters of the sampling filter, improving the effectiveness of the input signal of the phase-locked loop, and further realizing the impedance optimization of the output of the inverter.
The technical scheme applied by the patent is an inverter impedance optimization method considering a sampling filtering phase-locked loop. A grid-connected system schematic diagram considering sampling filtering is shown in FIG. 1, wherein U isgIs the grid voltage; l isgIs a grid inductance; l isfIs an inverter filter inductor; u shapedcIs the dc side voltage.
Compared with the existing inverter impedance model, fig. 1 shows that the inverter impedance optimization method considering the sampling filter phase-locked loop increases a sampling filter link compared with the traditional inverter impedance model, considers the conditioning effect of the sampling filter on the original signal in the actual operation working condition of grid connection, enables the impedance model of the grid-connected inverter to be close to the real impedance, improves the capacity of the phase-locked loop for inhibiting the disturbance signal by optimizing the parameters of the sampling filter, realizes the impedance optimization, and achieves the purpose of oscillation inhibition. The concrete implementation means is as follows:
step A: calculating an inverter impedance model of a sampling filter phase-locked loop, and generating:
the system is in a stable working state in the process of modeling the impedance of the inverter. The method comprises the steps of firstly carrying out harmonic linearization on a plurality of control loops in a frequency domain according to the topological characteristics of an inverter and the conditioning effect of sampling filtering on input signals, then obtaining current response caused by power grid harmonic voltage disturbance in the operating state of the inverter by utilizing the linearization result, and finally deducing an inverter impedance model taking the sampling filtering phase-locked loop into account.
When the inverter outlet voltage contains harmonic disturbance, the total outlet voltage (taking phase A as an example) is
Figure BDA0002171977430000051
Wherein v isaIs a mouth A phase voltage instantaneous value, V1For the fundamental voltage amplitude, omega, at the outlet of the converter1At fundamental voltage angular frequency, VpIs the harmonic voltage amplitude, omegapIn order to be at the harmonic voltage angular frequency,
Figure BDA0002171977430000052
is the initial phase of the harmonic voltage. The phase angle of the output of the phase-locked loop is thetaPLLIncluding the fundamental voltage phase angle theta0Perturbation phase angle delta theta, theta caused by harmonic voltagePLLCan be expressed as
θPLL＝θ0+Δθ
The perturbation phase angle Delta theta and the fundamental wave phase angle theta are compared0Separating, neglecting the influence of high-order infinitesimal nonlinear components, and obtaining the transfer function F between harmonic voltage disturbance and perturbation phase angle delta thetap(s), then Fp(s) can be written as
Figure BDA0002171977430000053
In the formula HPLLRepresenting the phase-locked loop transfer function. The signal conditioning characteristics of the sampling filtering element can be represented by a filter as
Figure BDA0002171977430000054
Where m is the pass-band amplification factor,
Figure BDA0002171977430000061
is the center frequency. When the d axis of the inverter current is coincident with the positive sequence component of the fundamental wave of the grid voltage, the active current I at the outlet of the inverterdReactive current IqThe line dq axis current of which can be written as
Figure BDA0002171977430000062
In the formula VpIs a harmonic voltage, IpIs harmonic current of the line, where D(s) ± jFp(s)，B(s±j2πf1) As a function of the filter characteristics at frequency offset. The output quantity of the fundamental current of the converter is equal to the current reference value under the stable working state, and H in the current control loopiConstant value of(s) outputUsing C as catalystd、CqRepresenting the dq axis output steady state value. Taking phase A as an example, the voltage E of the inverter portaCan be written as
Figure BDA0002171977430000063
In the formula KdqIs a decoupling factor. When the outlet voltage of the inverter is injected into the disturbance frequency, the impedance model analytic value Z between the harmonic voltage and the harmonic current output by the inverter can be written as
Figure BDA0002171977430000064
Therefore, an inverter impedance model considering the sampling filtering phase-locked loop can be obtained, the model considers the signal adjustment characteristic of the sampling filtering link, the steady-state operation value of the inverter, the loop control parameter, the voltage and the current harmonic component, and the frequency characteristic analysis of the inverter impedance model considering the sampling filtering phase-locked loop is shown in the embodiment example 1.
And B: and (3) considering the inverter impedance optimization step of the sampling filter phase-locked loop:
from the analytical expression of the inverter impedance model Z, the value of Z is changed while taking into account the effects of the sampling filtering and the phase-locked loop. The dynamic performance of the integral output phase angle of the phase-locked loop is changed by utilizing the adjustment effect of the sampling filtering on the original signal, so that the expected impedance range is obtained, and the purpose of optimizing the impedance of the inverter is achieved.
Center frequency in optimizing the relevant parameters of the sampling filter
Figure BDA0002171977430000065
The ratio of b to a is not changed, and a and b need to be scaled by equal times; the pass band amplification factor m changes slightly within 0.9-1.1, and the sampling filtering frequency characteristic can be optimized by adjusting the parameters. From the analytic expression of the inverter impedance model Z, it can be seen that the medium molecules do not change with the sampling filteringThe parent contains the frequency characteristic function of the sampling filter, so that the impedance is optimized in the process of optimizing the frequency characteristic of the filter.
The frequency characteristics of the existing inverter-side impedance model, the frequency characteristics of the inverter impedance model considering the sampling filter phase-locked loop, and the impedance optimization comparison analysis are shown in the embodiment example 1.
Example 1:
the existing impedance modeling only considers the parameter influence of an inverter control loop, and in a sampling link containing filtering, because the sampling filtering link can adjust each signal component in a power grid, the impedance characteristic introduced by the sampling filtering link is ignored by the existing inverter impedance model. In order to verify the effect of the invention, firstly, the frequency characteristic curve of the existing traditional inverter impedance model is drawn, then the frequency characteristic curve of the inverter impedance model taking the sampling filtering phase-locked loop into account is drawn according to the scheme of the invention, and finally the frequency characteristic curve of the inverter impedance model taking the sampling filtering phase-locked loop into account after optimization is drawn. Through comparative analysis of the three frequency characteristic curves, the correction and optimization of the scheme of the invention on the existing inverter impedance model are verified. The invention aims to provide a more reliable and effective scheme for the impedance optimization of the renewable energy grid connection so as to improve the stability of the renewable energy grid connection. At present, renewable energy grid connection stability optimization focuses on subsynchronous/supersynchronous frequency, so in the implementation example, comparison of impedance models before and after optimization is mainly performed aiming at a subsynchronous/supersynchronous frequency range (0-110 Hz).
The frequency characteristic curve obtained from the existing inverter impedance model is shown in fig. 2. The abscissa in the figure adopts a logarithmic coordinate axis, and it can be seen from the figure that the amplitude-frequency characteristic curve changes obviously with the frequency near the fundamental wave 50Hz, and the phase-frequency characteristic curve also changes accordingly. By utilizing the inverter impedance model analytical expression of the invention, the frequency characteristic curve of the inverter impedance model of the sampling filtering phase-locked loop is drawn, as shown in fig. 3, wherein the amplitude frequency characteristic curve and the phase frequency characteristic curve have obvious change along with the frequency in the range of 0 Hz-150 Hz, and the curve has difference with the inverter impedance model without considering the sampling filter. When the parameters of the sampling filter are optimized, the inverter impedance model considering the sampling filter phase-locked loop is shown in fig. 4, the amplitude and phase curves in the graph are close to the main trends presented by the inverter impedance in fig. 2 and 3, but the impedance of the part on the amplitude curve is improved under the influence of the sampling filter parameters, and the impedance optimization is generated after the sampling filter parameters are considered. The optimized impedance can enable the inverter to avoid the original oscillation interval in the grid connection process, so that the grid connection stability of the inverter is improved. The frequency characteristic curve of the inverter with the sampling filter phase-locked loop taken into account after the impedance is optimized shows that: the optimization of the impedance of the inverter considering the sampling filtering phase-locked loop can be realized by optimizing the sampling filtering parameters, the impedance optimization method of the scheme of the invention does not change the original parameters of the control loop, the impedance of the inverter is optimized from the aspect of sampling filtering, and the approaches of impedance optimization are widened.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims (4)

1. An inverter impedance optimization method considering a sampling filter phase-locked loop is characterized by comprising the following steps:
establishing an impedance model: according to the actual operation mode of the renewable energy grid-connected system, considering the influence of a voltage sampling filtering link on a phase-locked loop input signal, and establishing an impedance model of the inverter;
and (3) optimizing an impedance model: by combining the impedance model of the inverter and optimizing the parameters of the sampling filter, the filtering characteristic of voltage sampling is changed, the effectiveness of the input signal of the phase-locked loop is improved, and the impedance optimization of the output of the inverter is realized;
the impedance model establishing step comprises:
calculating the total voltage of an outlet of the inverter:
when the inverter outlet voltage contains harmonic disturbance, the total A-phase outlet voltage is as follows:
Figure FDA0003010338670000011
wherein: v. ofaIs a mouth A phase voltage instantaneous value, V1For the fundamental voltage amplitude, omega, at the outlet of the converter1At fundamental voltage angular frequency, VpIs the harmonic voltage amplitude, omegapIn order to be at the harmonic voltage angular frequency,
Figure FDA0003010338670000012
is the initial phase of the harmonic voltage;
calculating the phase angle output by the phase-locked loop:
θPLL＝θ0+Δθ
wherein: thetaPLLFor phase-locked loop output phase angle, theta0Is a fundamental voltage phase angle, and delta theta is a perturbation phase angle caused by harmonic voltage;
and a step of calculating a transfer function:
Figure FDA0003010338670000013
wherein: hPLLRepresenting a phase-locked loop transfer function;
a signal adjustment characteristic calculation step: the signal conditioning characteristics of the sampling filtering element can be represented by a filter as
Figure FDA0003010338670000014
Where m is the pass-band amplification factor,
Figure FDA0003010338670000015
is the center frequency;
calculating the dq axis current of the line: when the d axis of the inverter current is coincident with the positive sequence component of the fundamental wave of the grid voltage, invertingActive current I at the outlet of the devicedReactive current IqLine dq-axis current can be written as in the frequency domain
Figure FDA0003010338670000016
In the formula: vpIs the harmonic voltage amplitude, IpIs the harmonic current amplitude of the line, f1Is the fundamental frequency, I1For the amplitude of the fundamental current of the grid, fpFor positive sequence disturbance voltage frequency, where D(s) ± jFp(s)，B(s±j2πf1) As a function of the filter characteristics at frequency offset;
calculating the voltage of the inverter port: the output quantity of the fundamental current of the converter is equal to the current reference value under the stable working state, and H in the current control loopiThe value of(s) being constant, with Cd、CqRepresenting the steady state value of the dq-axis output, phase A, the voltage E at the inverter portaCan be written as
Figure FDA0003010338670000021
In the formula KdqIs a decoupling coefficient;
calculating an impedance model:
when the outlet voltage of the inverter is injected into the disturbance frequency, the impedance model analytic value Z between the harmonic voltage and the harmonic current output by the inverter is determined as
Figure FDA0003010338670000022
2. The method of optimizing the impedance of an inverter taking into account a sampling filter phase-locked loop of claim 1, wherein the impedance modeling step comprises:
carrying out harmonic linearization on a plurality of control loops in a frequency domain according to the topological characteristic of the inverter and the conditioning effect of sampling filtering on the input signal;
obtaining current response caused by power grid harmonic voltage disturbance in the inverter operation state by using the linearization result;
and deducing an inverter impedance model taking the sampling filter phase-locked loop into account.
3. The method of claim 1, wherein the center frequency is optimized according to the inverter impedance, and wherein the center frequency is calculated according to the method
Figure FDA0003010338670000023
The ratio of b to a of (a) is constant.
4. The method for optimizing the impedance of the inverter considering the sampling filter phase-locked loop according to claim 1, wherein the passband amplification factor m varies slightly and is finely adjusted between 0.9 and 1.1.
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