CN113113933B - Active damping control method and system for LCL inverter of weak power grid - Google Patents

Active damping control method and system for LCL inverter of weak power grid Download PDF

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CN113113933B
CN113113933B CN202110651186.7A CN202110651186A CN113113933B CN 113113933 B CN113113933 B CN 113113933B CN 202110651186 A CN202110651186 A CN 202110651186A CN 113113933 B CN113113933 B CN 113113933B
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phase margin
active damping
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frequency
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CN113113933A (en
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曾成碧
王翰文
苗虹
段述江
李苏丹
童广
朱胤杰
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Sichuan University
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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
    • 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
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics

Abstract

The invention discloses a method and a system for controlling active damping of a weak grid LCL inverter, which relate to the technical field of grid-connected inverters and have the technical scheme key points that: taking the voltage signal as the input of a high-pass filtering compensation strategy to obtain an active damping parameter; taking the active damping parameter and the phase margin compensation coefficient sequence as the input of active damping control, and simulating to obtain a system open-loop Bode diagram; extracting the open loop cut-off frequency in the open loop bode diagram of the system and the distribution condition of the open loop cut-off frequency and the phase margin, and selecting an optimal phase margin compensation coefficient; fusing the optimal phase margin compensation coefficient and the active damping parameter to obtain a leading phase compensation signal; and superposing the leading phase compensation signal and the output signal of the multi-resonance controller to realize the active damping control of the LCL inverter. The invention improves the phase margin of the system during grid connection, reduces the use of high-precision sensors, and has good robustness and dynamic response capability.

Description

Active damping control method and system for LCL inverter of weak power grid
Technical Field
The invention relates to the technical field of grid-connected inverters, in particular to an active damping control method and system for a weak grid LCL inverter.
Background
With the increasing shortage of fossil energy, the development of renewable clean energy has become the focus of current energy development. The grid-connected inverter plays an important role as a connecting junction between the clean energy power generation system and a power grid. Compared with an L filter, the LCL filter has the advantages of small size and strong attenuation capability, so that the LCL filter is widely applied to a grid-connected inverter. However, the LCL filter is a third order system, which without some damping strategy would cause resonance problems in the system and even make the system unstable.
The damping method of the LCL filter can be divided into active damping and passive damping. Passive damping has excellent damping but causes large losses, especially under light load conditions. In active damping, feedback of certain variables is used to provide system damping, such as capacitive current feedback, inverter side current feedback (ICF), grid side current feedback, current predictive control, voltage of filter capacitors, and the like. At present, documents describe a method for controlling a common coupling voltage feedforward point (GVF) on a system, and the GVF can prevent a large surge current in a starting process, reduce power grid interference, and improve the dynamic performance of the system. Researches find that under the condition that a power grid is weak, the harmonic suppression capability can be improved by using a Point of Common Coupling (PCC) voltage feedforward scheme, and extra power grid side current positive feedback can be introduced through feedforward control, so that the harmonic suppression of an LCL filter is facilitated.
While in certain high order cycles, a High Pass Filtering (HPF) equivalent is often employed, thereby reducing the number of sensors. The literature has proposed HPF active damping techniques with a single grid current feedback loop, grid side current feedback active damping using HPF and GVF. But does not take into account the adverse effects of wide range of grid impedance variations. Furthermore, there is literature that adds a simple HPF in the capacitor voltage feed forward (CVF) loop, effectively reducing low frequency harmonic pollution of the grid voltage controlled by the ICF, but the parameter settings are complex. Therefore, research and design of an active damping control method and system for a low-voltage network LCL inverter are problems which need to be solved urgently at present.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide a method and a system for controlling the active damping of a weak power grid LCL inverter.
The technical purpose of the invention is realized by the following technical scheme:
in a first aspect, an active damping control method for a weak grid LCL inverter is provided, which includes the following steps:
collecting voltage signals of grid-connected points;
taking the voltage signal as the input of a high-pass filtering compensation strategy to obtain an active damping parameter;
taking the active damping parameter and the phase margin compensation coefficient sequence as the input of active damping control, and simulating to obtain a system open-loop Bode diagram under the control of different phase margin compensation coefficients;
extracting the open-loop cut-off frequency in the open-loop Bode diagram of the system and the distribution condition of the open-loop cut-off frequency and the phase margin, and taking a corresponding phase margin compensation coefficient under the condition that the stability performance and the dynamic response of the weak power grid reflected by the distribution condition are optimal as an optimal phase margin compensation coefficient;
fusing the optimal phase margin compensation coefficient and the active damping parameter to obtain a leading phase compensation signal;
and superposing the leading phase compensation signal and the output signal of the multi-resonance controller to realize the active damping control of the LCL inverter.
Further, the optimal phase margin compensation coefficient analysis process specifically includes:
transforming the ring cut-off frequency and the phase margin through transforming the mapping relation;
establishing a first fitting curve by taking the phase margin compensation coefficient sequence as an abscissa and the transformed open-loop cut-off frequency as an ordinate;
establishing a second fitting curve by taking the phase margin compensation coefficient sequence as a horizontal coordinate and the transformed phase margin as a vertical coordinate;
and selecting the intersection point of the first fitting curve and the second fitting curve as an optimal phase margin compensation coefficient.
Further, the processing process of the distribution of the open-loop cut-off frequency and the phase margin specifically includes:
extracting open-loop cut-off frequencies corresponding to different phase margin compensation coefficients in an open-loop Bode diagram of the system to obtain an open-loop cut-off frequency set, and establishing an open-loop cut-off frequency range according to the maximum value and the minimum value in the open-loop cut-off frequency set;
and selecting a phase margin compensation coefficient which simultaneously accords with a standard phase margin range and an open loop cut-off frequency range to obtain the distribution condition.
Further, the standard phase margin ranges from 20 degrees to 55 degrees.
Further, the active damping parameter calculation process specifically includes:
Figure 1191DEST_PATH_IMAGE001
wherein the content of the first and second substances,
Figure 627344DEST_PATH_IMAGE002
active damping parameters;
Figure 280042DEST_PATH_IMAGE003
is the gain factor of the high-pass filter;
Figure 181002DEST_PATH_IMAGE004
is the cut-off bandwidth of the high-pass filter; s is a time domain.
Further, the calculation process of the lead phase compensation signal specifically includes:
Figure 337177DEST_PATH_IMAGE005
wherein the content of the first and second substances,
Figure 416123DEST_PATH_IMAGE006
is a leading phase compensation signal;
Figure 290538DEST_PATH_IMAGE007
the coefficients are compensated for an optimal phase margin.
Further, the specific calculation process of the gain coefficient of the high-pass filter is as follows:
Figure 729609DEST_PATH_IMAGE008
wherein m is normalNumber, value of [0.6,6]；L1A filter inductor on the inverter side; l is2A filter inductor on the power grid side; l isgIs the grid impedance; kPWMIs the transfer function of the PWM inverter and is expressed as Udc/Utri，UtriIs a triangular carrier amplitude, UdcAnd the direct current bus voltage is used for generating power for new energy.
Further, the calculation process of the cut-off bandwidth of the high-pass filter specifically includes:
Figure 5870DEST_PATH_IMAGE009
wherein C is a filter capacitor;
Figure 504984DEST_PATH_IMAGE010
is the damping factor.
In a second aspect, an active damping control system for a weak grid LCL inverter is provided, including:
the data acquisition module is used for acquiring voltage signals of the grid-connected point;
the parameter calculation module is used for taking the voltage signal as the input of a high-pass filtering compensation strategy to obtain an active damping parameter;
the simulation calculation module is used for taking the active damping parameters and the phase margin compensation coefficient sequence as the input of active damping control, and simulating to obtain a system open-loop Bode diagram under the control of different phase margin compensation coefficients;
the coefficient analysis module is used for extracting the open-loop cut-off frequency in the open-loop Bode diagram of the system and the distribution condition of the open-loop cut-off frequency and the phase margin, and taking a corresponding phase margin compensation coefficient under the condition that the stability performance and the dynamic response of the weak power grid reflected by the distribution condition are optimal as an optimal phase margin compensation coefficient;
the data fusion module is used for fusing the optimal phase margin compensation coefficient with the active damping parameter to obtain a leading phase compensation signal;
and the signal superposition module is used for superposing the lead phase compensation signal and the output signal of the multi-resonance controller to realize the active damping control of the LCL inverter.
Further, the coefficient analysis module includes:
the mapping unit is used for carrying out transformation processing on the ring cut-off frequency and the phase margin through transforming the mapping relation;
the first fitting unit is used for establishing a first fitting curve by taking the phase margin compensation coefficient sequence as an abscissa and the transformed open-loop cut-off frequency as an ordinate;
the second fitting unit is used for establishing a second fitting curve by taking the phase margin compensation coefficient sequence as a horizontal coordinate and the transformed phase margin as a vertical coordinate;
and the curve processing unit is used for selecting the intersection point of the first fitting curve and the second fitting curve as an optimal phase margin compensation coefficient.
Compared with the prior art, the invention has the following beneficial effects: the invention provides an active damping method based on grid-connected point voltage feedback aiming at a grid-connected LCL filter inverter under a weak power grid environment; compared with the traditional control method, the control method has the advantages that the common high-pass filter is improved to improve the phase margin of the system during grid connection, the use of high-precision sensors is reduced, and simulation and experiment results based on a grid-connected inverter prototype prove that the control method has good robustness and dynamic response capability.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 is a flow chart in an embodiment of the invention;
FIG. 2 is a block diagram of active damping control for H(s) control strategy in an embodiment of the present invention;
fig. 3 is a block diagram of active damping control for H x(s) control strategy in an embodiment of the present invention;
FIG. 4 is an open loop Bode diagram of the system at different kcs in an embodiment of the present invention;
FIG. 5 is an open loop Bode plot of the system at different Lg in an embodiment of the invention;
FIG. 6 is a graph of a fit determination for an optimal phase margin compensation coefficient in an embodiment of the invention;
FIG. 7 is a system open loop Bode diagram when the H(s) control strategy is adopted in the embodiment of the present invention;
fig. 8 is an open loop bode plot of the system when H × s control strategy is employed in an embodiment of the present invention;
FIG. 9 is a grid-connected current simulation waveform of two control strategies when Lg is 0.6mH in the embodiment of the invention;
FIG. 10 is a grid-connected current simulation waveform of two control strategies when Lg is 2mH in the embodiment of the invention;
FIG. 11 is a grid-connected current simulation waveform of two control strategies when Lg is 4mH in the embodiment of the invention;
FIG. 12 is a grid-connected current harmonic analysis diagram of two control strategies in the embodiment of the present invention when Lg is 4 mH;
FIG. 13 is a grid-connected current experimental waveform of two control strategies when Lg is 0.6mH in the embodiment of the invention;
FIG. 14 is grid-connected current experimental waveforms of two control strategies when Lg is 2mH in the embodiment of the invention;
FIG. 15 shows experimental waveforms of grid-connected currents of two control strategies when Lg is 4mH in the embodiment of the present invention;
FIG. 16 is an FFT analysis chart of two control strategies for an embodiment of the present invention with Lg at 4 mH;
fig. 17 is a block diagram of a system in an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
Example 1: an active damping control method for a low-voltage network LCL inverter, as shown in FIGS. 1-3, comprises the following steps:
s1: collecting voltage signals of grid-connected points;
s2: taking the voltage signal as the input of a high-pass filtering compensation strategy to obtain an active damping parameter;
s3: taking the active damping parameter and the phase margin compensation coefficient sequence as the input of active damping control, and simulating to obtain a system open-loop Bode diagram under the control of different phase margin compensation coefficients;
s4: extracting the open-loop cut-off frequency in the open-loop Bode diagram of the system and the distribution condition of the open-loop cut-off frequency and the phase margin, and taking a corresponding phase margin compensation coefficient under the condition that the stability performance and the dynamic response of the weak power grid reflected by the distribution condition are optimal as an optimal phase margin compensation coefficient;
s5: fusing the optimal phase margin compensation coefficient and the active damping parameter to obtain a leading phase compensation signal;
s6: and superposing the leading phase compensation signal and the output signal of the multi-resonance controller to realize the active damping control of the LCL inverter.
As shown in fig. 2, the active damping parameter calculation process specifically includes:
Figure 866696DEST_PATH_IMAGE001
wherein the content of the first and second substances,
Figure 116584DEST_PATH_IMAGE002
active damping parameters;
Figure 247351DEST_PATH_IMAGE003
is the gain factor of the high-pass filter;
Figure 917367DEST_PATH_IMAGE004
is the cut-off bandwidth of the high-pass filter; s is a time domain.
As shown in fig. 3, the calculation process of the lead phase compensation signal specifically includes:
Figure 766374DEST_PATH_IMAGE005
wherein the content of the first and second substances,
Figure 281669DEST_PATH_IMAGE006
is a leading phase compensation signal;
Figure 798101DEST_PATH_IMAGE007
the coefficients are compensated for an optimal phase margin.
The specific calculation process of the gain coefficient of the high-pass filter is as follows:
Figure 124171DEST_PATH_IMAGE008
wherein m is a constant with a value of [0.6,6]；L1A filter inductor on the inverter side; l is2A filter inductor on the power grid side; l isgIs the grid impedance; kPWMIs the transfer function of the PWM inverter and is expressed as Udc/Utri，UtriIs a triangular carrier amplitude, UdcAnd the direct current bus voltage is used for generating power for new energy.
The calculation process of the cut-off bandwidth of the high-pass filter is specifically as follows:
Figure 460475DEST_PATH_IMAGE009
wherein C is a filter capacitor;
Figure 779461DEST_PATH_IMAGE010
the value of the damping factor is 0.707.
The distribution situation processing process of the open loop cut-off frequency and the phase margin specifically comprises the following steps: extracting open-loop cut-off frequencies corresponding to different phase margin compensation coefficients in an open-loop Bode diagram of the system to obtain an open-loop cut-off frequency set, and establishing an open-loop cut-off frequency range according to the maximum value and the minimum value in the open-loop cut-off frequency set; and selecting a phase margin compensation coefficient which simultaneously accords with a standard phase margin range and an open loop cut-off frequency range to obtain the distribution condition.
In step S4, the optimal phase margin compensation coefficient analysis process specifically includes: transforming the ring cut-off frequency and the phase margin through transforming the mapping relation; establishing a first fitting curve by taking the phase margin compensation coefficient sequence as an abscissa and the transformed open-loop cut-off frequency as an ordinate; establishing a second fitting curve by taking the phase margin compensation coefficient sequence as a horizontal coordinate and the transformed phase margin as a vertical coordinate; and selecting the intersection point of the first fitting curve and the second fitting curve as an optimal phase margin compensation coefficient.
In the present embodiment, the sequence of the phase margin compensation coefficients is {125, 250, 500, 1000}, and the obtained open loop bode plot of the system at different kc is shown in fig. 4. Obviously, with kcIncreasing, the open loop phase margin of the system increases, but the amplitude of the open loop amplitude curve decreases, causing the open loop cutoff frequency to move backwards. The selected open loop cutoff frequency is 844HZ-985HZ, the standard phase margin range is 20-55 degrees, and the distribution conditions under 125, 250, 500 and 1000 meet the requirements. Wherein k iscIs 125, open loop cutoff frequency fopenAt 985HZ, the phase margin is 21 °. When k iscWhen the value of (d) is taken to be 250, the open loop cut-off frequency f of the systemopenAt 961HZ, the phase margin is 32 °. When k iscWhen the value of (d) is 500, the open loop cut-off frequency f of the systemopenAt 922HZ, the phase margin is 42.5 °. When k iscWhen the value of (d) is 1000, the open loop cut-off frequency f of the systemopenAt 851HZ, the phase margin is 53 °. The graph after the fitting process is shown in FIG. 6, where k corresponds to the intersection pointcThe value is 450, so that the optimal phase margin compensation coefficient k is obtainedcThe value is 450. It should be noted that the mapping relationship is transformed so that the corresponding ordinate spacing and value are adjusted according to the open-loop cut-off frequency and the phase margin in order to establish the open-loop cut-off frequency and the phase margin in the same two-dimensional coordinate system, and the mapping relationships are different under the influence of the system.
As shown in fig. 5, in the open-loop bode diagram of the h(s) control strategy at different Lg times in fig. 5, as the impedance of the power grid increases, the stability margin of the system decreases, and the open-loop cutoff frequency of the system greatly decreases, so that the harmonic peak of the multi-resonance controller is closer to the-180 ° line. If the influence of control delay and discretization on the system is considered, the open-loop phase margin of the system can be further reduced, a resonance peak is intersected with a-180-degree line, and the electric energy quality of grid-connected current output by the system is deteriorated. Fig. 5 b is an open-loop bode plot of H × s control strategy at different Lg, and comparing b in fig. 5 with a in fig. 5, it can be seen that when Lg =4m, the phase at the maximum resonance peak of the multi-resonance controller is increased, and premature crossing of the-180 ° line is avoided. Therefore, the optimized control method H(s) not only keeps the original damping effect, but also has better phase margin and improves the stability of the system.
When the grid impedance Lg varies within the range of [0.6mH, 4mH ], system open-loop bode plots of the two control strategies are plotted, as shown in fig. 7 and 8. As can be seen from fig. 7, when the h(s) control strategy is adopted, the PM variation range of the open loop system is 2 ° -38 °, the GM variation range is 3.3-15.6 dB, the phase margin is greatly reduced, and the 7 th and 9 th formants intersect the-180 ° line in advance, which results in that the harmonics near the formants are greatly amplified.
In contrast, as shown in FIG. 8, when the grid impedance Lg varies within the range of [0.6mH, 4mH ], the variation range of PM is 16-39 °, and the variation range of GM is 2.1-15.8 dB. Obviously, there is a large increase in PM for H x(s) control strategy, and the larger Lg, the more PM is increased, which solves the problem of premature intersection of the resonance peak with-180 ° line.
Therefore, the AD control method designed by the invention can effectively improve the system adaptability when the impedance of the power grid changes in a large range, and the method is very simple to implement.
First, simulation verification effect
It should be noted that (a) in fig. 9-12 is simulation performed under H(s) control strategy, and (b) in fig. 9-12 is simulation performed under H(s) control strategy.
As can be seen from fig. 9 (a) and 9 (b), both AD control strategies can keep the system stable when Lg =0.6 mH. This is consistent with theoretical analysis. However, as Lg increases, the grid-connected current using the h(s) active damping control strategy begins to be distorted, as shown in fig. 10 (a) and 10 (b), and the Total Harmonic Distortion (THD) increases to 5.10%. Likewise, as shown in fig. 11 (a), when the grid inductance lg =4mH, the current waveform using the h(s) active damping control strategy is severely distorted, and THD increases to 15.79%. The reason for the grid side current distortion is that the 9 th harmonic peak crosses the-180 ° line in advance, resulting in the 9 th harmonic being heavily amplified as shown in fig. 12 (a). When the H × s active damping control strategy is adopted, the grid-connected current is kept stable, and the corresponding THD is 1.64%, as shown in fig. 11 (b) and fig. 12 (b). Similarly, when the grid inductance lg =4mH, the THD of the grid-side current is greatly reduced by using the H × s method. Therefore, H(s) control strategy has good stability when Lg varies over a large range.
Second, experiment verification effect
According to the invention, a 9.1kW three-phase grid-connected inverter control platform is constructed according to a simulation model and theoretical analysis so as to verify the practicability and effectiveness of the proposed method. The direct current side of the inverter is connected with an adjustable transformer, and the working voltage of the inverter is output through a knob of the adjustable transformer. The output side of the LCL inverter is connected to a power grid through a relay (SSR-3D 4830A), grid connection time is judged through a program written in C language, and a grid connection signal is sent to open the relay to realize grid connection.
Note that (a) in fig. 13 to 16 is an experiment performed under the H(s) control strategy, and (b) in fig. 13 to 16 is an experiment performed under the H(s) control strategy.
Fig. 13-15 are experimental waveforms for two control strategies at different grid impedances. As can be seen from fig. 13 (a), when Lg =0.6mH, the grid-connected current using the active damping feedback strategy of h(s) is stable, and the THD is only 1.53%. However, as Lg increases, the grid-side current is slightly distorted as shown in fig. 14 (a), and THD increases to 4.91%. This is because the phase margin of the system is reduced resulting in a resonance peak close to the-180 line. As shown in fig. 15 (a), when Lg is increased to 4mH, the phase margin of the system is already seriously insufficient at this time, the 9 th harmonic in the grid-side current is greatly amplified, and THD is increased to 10.51%. This is also demonstrated by the FFT analysis as in (a) of fig. 16. Therefore, using the h(s) active damping feedback strategy can only maintain stability over a small range of grid impedances, consistent with theoretical analysis and simulations.
Fig. 13 (b), fig. 14 (b), and fig. 15 (b) are experimental waveforms of grid-connected current when using H × s active damping feedback strategy at Lg =0.6, 2, 4mH, respectively. It can be seen that the grid-connected current I is no matter Lg =0.6mH, 2mH or 4mH2Can keep good fundamental frequency sine wave I2The THD of (1.88%, 2.04% and 2.77%) is also much lower than when H(s) is used. The FFT analysis as in (b) of fig. 16 also shows that the higher harmonics originally present are largely suppressed.
In conclusion, the improved active damping method based on the common point voltage feedback of the grid-connected LCL inverter in the weak grid environment not only improves the phase margin of the system during grid connection and reduces high-precision sensors, but also fully considers the change of the grid impedance and has good stability.
Example 2: an active damping control system of a low-voltage network LCL inverter is shown in FIG. 17 and comprises a data acquisition module, a parameter calculation module, a simulation calculation module, a coefficient analysis module, a data fusion module and a signal superposition module. The data acquisition module is used for acquiring voltage signals of the grid-connected point; the parameter calculation module is used for taking the voltage signal as the input of a high-pass filtering compensation strategy to obtain an active damping parameter; the simulation calculation module is used for taking the active damping parameters and the phase margin compensation coefficient sequence as the input of active damping control, and simulating to obtain a system open-loop Bode diagram under the control of different phase margin compensation coefficients; the coefficient analysis module is used for extracting the open-loop cut-off frequency in the open-loop Bode diagram of the system and the distribution condition of the open-loop cut-off frequency and the phase margin, and taking a corresponding phase margin compensation coefficient under the condition that the stability performance and the dynamic response of the weak power grid reflected by the distribution condition are optimal as an optimal phase margin compensation coefficient; the data fusion module is used for fusing the optimal phase margin compensation coefficient with the active damping parameter to obtain a leading phase compensation signal; and the signal superposition module is used for superposing the lead phase compensation signal and the output signal of the multi-resonance controller to realize the active damping control of the LCL inverter.
The coefficient analysis module comprises a mapping unit, a first fitting unit, a second fitting unit and a curve processing unit. The mapping unit is used for carrying out transformation processing on the ring cut-off frequency and the phase margin through transforming the mapping relation; the first fitting unit is used for establishing a first fitting curve by taking the phase margin compensation coefficient sequence as an abscissa and the transformed open-loop cut-off frequency as an ordinate; the second fitting unit is used for establishing a second fitting curve by taking the phase margin compensation coefficient sequence as a horizontal coordinate and the transformed phase margin as a vertical coordinate; and the curve processing unit is used for selecting the intersection point of the first fitting curve and the second fitting curve as an optimal phase margin compensation coefficient.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above embodiments are provided to further explain the objects, technical solutions and advantages of the present invention in detail, it should be understood that the above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (8)

1. An active damping control method for a weak grid LCL inverter is characterized by comprising the following steps:
collecting voltage signals of grid-connected points;
taking the voltage signal as the input of a high-pass filtering compensation strategy to obtain an active damping parameter;
taking the active damping parameter and the phase margin compensation coefficient sequence as the input of active damping control, and simulating to obtain a system open-loop Bode diagram under the control of different phase margin compensation coefficients;
extracting the open-loop cut-off frequency in the open-loop Bode diagram of the system and the distribution condition of the open-loop cut-off frequency and the phase margin, and taking a corresponding phase margin compensation coefficient under the condition that the stability performance and the dynamic response of the weak power grid reflected by the distribution condition are optimal as an optimal phase margin compensation coefficient;
fusing the optimal phase margin compensation coefficient and the active damping parameter to obtain a leading phase compensation signal;
superposing the leading phase compensation signal and the output signal of the multi-resonance controller to realize the active damping control of the LCL inverter;
the optimal phase margin compensation coefficient analysis process specifically comprises the following steps:
transforming the ring cut-off frequency and the phase margin through transforming the mapping relation;
establishing a first fitting curve by taking the phase margin compensation coefficient sequence as an abscissa and the transformed open-loop cut-off frequency as an ordinate;
establishing a second fitting curve by taking the phase margin compensation coefficient sequence as a horizontal coordinate and the transformed phase margin as a vertical coordinate;
and selecting the intersection point of the first fitting curve and the second fitting curve as an optimal phase margin compensation coefficient.
2. The active damping control method for the low-power-grid LCL inverter according to claim 1, wherein the distribution processing procedure of the open-loop cut-off frequency and the phase margin is specifically as follows:
extracting open-loop cut-off frequencies corresponding to different phase margin compensation coefficients in an open-loop Bode diagram of the system to obtain an open-loop cut-off frequency set, and establishing an open-loop cut-off frequency range according to the maximum value and the minimum value in the open-loop cut-off frequency set;
and selecting a phase margin compensation coefficient which simultaneously accords with a standard phase margin range and an open loop cut-off frequency range to obtain the distribution condition.
3. The active damping control method of the weak grid LCL inverter according to claim 2, wherein the standard phase margin ranges from 20 ° to 55 °.
4. The method for controlling the active damping of the low-voltage network LCL inverter according to any one of claims 1 to 3, wherein the calculation process of the active damping parameters is specifically as follows:
Figure DEST_PATH_IMAGE001
wherein the content of the first and second substances,
Figure 974133DEST_PATH_IMAGE002
active damping parameters;
Figure DEST_PATH_IMAGE003
is the gain factor of the high-pass filter;
Figure 625694DEST_PATH_IMAGE004
is the cut-off bandwidth of the high-pass filter;Sis a time domain.
5. The active damping control method of the low-voltage network LCL inverter according to claim 4, wherein the calculation process of the lead phase compensation signal is specifically as follows:
Figure DEST_PATH_IMAGE005
wherein the content of the first and second substances,
Figure 202169DEST_PATH_IMAGE006
is a leading phase compensation signal;
Figure DEST_PATH_IMAGE007
the coefficients are compensated for an optimal phase margin.
6. The active damping control method of the weak grid LCL inverter as claimed in claim 4, wherein the specific calculation process of the gain coefficient of the high-pass filter is as follows:
Figure 456433DEST_PATH_IMAGE008
wherein m is a constant with a value of [0.6,6]；L1A filter inductor on the inverter side; l is2A filter inductor on the power grid side; l isgIs the grid impedance; kPWMIs the transfer function of the PWM inverter and is expressed as Udc/Utri，UtriIs a triangular carrier amplitude, UdcAnd the direct current bus voltage is used for generating power for new energy.
7. The active damping control method of the low-power-grid LCL inverter as claimed in claim 4, wherein the calculation process of the cut-off bandwidth of the high-pass filter is specifically as follows:
Figure DEST_PATH_IMAGE009
wherein C is a filter capacitor;
Figure 739646DEST_PATH_IMAGE010
is a damping factor; m is constant and takes the value of [0.6,6]；L1A filter inductor on the inverter side; l is2A filter inductor on the power grid side; l isgIs the grid impedance.
8. An active damping control system of a weak current network LCL inverter is characterized by comprising:
the data acquisition module is used for acquiring voltage signals of the grid-connected point;
the parameter calculation module is used for taking the voltage signal as the input of a high-pass filtering compensation strategy to obtain an active damping parameter;
the simulation calculation module is used for taking the active damping parameters and the phase margin compensation coefficient sequence as the input of active damping control, and simulating to obtain a system open-loop Bode diagram under the control of different phase margin compensation coefficients;
the coefficient analysis module is used for extracting the open-loop cut-off frequency in the open-loop Bode diagram of the system and the distribution condition of the open-loop cut-off frequency and the phase margin, and taking a corresponding phase margin compensation coefficient under the condition that the stability performance and the dynamic response of the weak power grid reflected by the distribution condition are optimal as an optimal phase margin compensation coefficient;
the data fusion module is used for fusing the optimal phase margin compensation coefficient with the active damping parameter to obtain a leading phase compensation signal;
the signal superposition module is used for superposing the lead phase compensation signal and the output signal of the multi-resonance controller to realize the active damping control of the LCL inverter;
the coefficient analysis module includes:
the mapping unit is used for carrying out transformation processing on the ring cut-off frequency and the phase margin through transforming the mapping relation;
the first fitting unit is used for establishing a first fitting curve by taking the phase margin compensation coefficient sequence as an abscissa and the transformed open-loop cut-off frequency as an ordinate;
the second fitting unit is used for establishing a second fitting curve by taking the phase margin compensation coefficient sequence as a horizontal coordinate and the transformed phase margin as a vertical coordinate;
and the curve processing unit is used for selecting the intersection point of the first fitting curve and the second fitting curve as an optimal phase margin compensation coefficient.
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103354359A (en) * 2013-08-02 2013-10-16 南京航空航天大学 Phase angle margin compensation-based system impedance active control method of grid -connected inverter
CN107332281A (en) * 2017-05-26 2017-11-07 合肥工业大学 The light current control method of grid-connected inverter off the net with voltage feed-forward control lag compensation
CN109193792A (en) * 2018-11-16 2019-01-11 燕山大学 The SOCVF feedforward of gird-connected inverter and phase compensating factor method for handover control under weak grid
CN110148943A (en) * 2019-06-18 2019-08-20 福州大学 A kind of LCL gird-connected inverter impedance remodeling procedure for inhibiting power grid background harmonics to influence
CN112532096A (en) * 2020-12-03 2021-03-19 南京理工大学 LCL inverter grid-connected device and method suitable for weak power grid

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103248259B (en) * 2013-04-16 2014-03-19 湖南大学 Single-current feedback control method of three-phase LCL (lower control limit) filtering type PWM (pulse-width modulation) rectifier
CN104600703B (en) * 2015-02-05 2017-01-11 重庆大学 Grid-connected inverter harmonic resonance suppression method based on phase margin compensation
US9800134B2 (en) * 2015-02-25 2017-10-24 Rockwell Automation Technologies, Inc. Motor drive with LCL filter inductor with built-in passive damping resistor for AFE rectifier
CN106099971B (en) * 2016-05-18 2018-08-07 艾思玛新能源技术（江苏）有限公司 Improve control method and system of the single-phase photovoltaic inverter to the adaptability of light current net
CN106532701B (en) * 2016-11-16 2019-01-18 西安交通大学 LCL type Active Power Filter-APF and its control method
CN108258726A (en) * 2018-01-24 2018-07-06 长沙理工大学 A kind of LCL gird-connected inverters active damping strategy
CN108448583A (en) * 2018-05-02 2018-08-24 燕山大学 A kind of modified adjuster applied to light current gird-connected inverter off the net
CN109361218B (en) * 2018-12-08 2022-05-10 南京理工大学 LCL type converter active damping optimal delay compensation method
CN110445143B (en) * 2019-09-06 2021-06-29 集美大学 Active damping method of LCL type grid-connected inverter
CN112600450B (en) * 2020-12-15 2021-12-24 北京航空航天大学 Single-phase grid-connected inverter control method, system, equipment and medium
CN112886847B (en) * 2021-04-02 2022-05-13 四川大学 Three-phase LCL type grid-connected inverter design method based on impedance analysis method

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103354359A (en) * 2013-08-02 2013-10-16 南京航空航天大学 Phase angle margin compensation-based system impedance active control method of grid -connected inverter
CN107332281A (en) * 2017-05-26 2017-11-07 合肥工业大学 The light current control method of grid-connected inverter off the net with voltage feed-forward control lag compensation
CN109193792A (en) * 2018-11-16 2019-01-11 燕山大学 The SOCVF feedforward of gird-connected inverter and phase compensating factor method for handover control under weak grid
CN110148943A (en) * 2019-06-18 2019-08-20 福州大学 A kind of LCL gird-connected inverter impedance remodeling procedure for inhibiting power grid background harmonics to influence
CN112532096A (en) * 2020-12-03 2021-03-19 南京理工大学 LCL inverter grid-connected device and method suitable for weak power grid

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