CN112737388B - Common-mode active damping resonant circulating current suppression system and method for inverter parallel system - Google Patents

Common-mode active damping resonant circulating current suppression system and method for inverter parallel system Download PDF

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CN112737388B
CN112737388B CN202110205506.6A CN202110205506A CN112737388B CN 112737388 B CN112737388 B CN 112737388B CN 202110205506 A CN202110205506 A CN 202110205506A CN 112737388 B CN112737388 B CN 112737388B
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circulating current
inverter
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CN112737388A (en
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张承慧
刘浩
李晓艳
邢相洋
李同兴
张洪亮
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Siemens Electrical Drives Ltd
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Shandong University
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    • 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
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H02M1/126—Arrangements for reducing harmonics from ac input or output using passive filters
    • 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
    • H02M1/00—Details of apparatus for conversion
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Abstract

The invention provides a common-mode active damping resonance circulating current suppression system and a common-mode active damping resonance circulating current suppression method for an inverter parallel system, wherein the running state data of the resonance circulating current suppression system is obtained, the resonance circulating current suppression system comprises at least two parallel three-level inverters, and the common point of an alternating current side filter capacitor of each inverter is connected back to a direct current side neutral point through a lead; obtaining a control variable according to the obtained running state data, and adjusting the action time of a redundant small vector in three-level space vector modulation at the resonant frequency by using the control variable to adjust the resonant peak value so as to further realize the inhibition of resonant circulation; setting a reference value of zero-sequence circulating current on the inverter side to be zero, and sending an error between the reference value and an actual value to a PI (proportional integral) controller to obtain a control variable; the method realizes the resonance circulating current suppression of the novel LCL filter parallel three-level inverter, and effectively solves the problem of high system fault rate caused by overhigh zero-sequence circulating current of the modularized parallel three-level inverter.

Description

Common-mode active damping resonant circulating current suppression system and method for inverter parallel system
Technical Field
The disclosure relates to the technical field of inverter parallel system resonant circulation suppression, in particular to a common-mode active damping resonant circulation suppression system and method of an inverter parallel system.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
With the rapid development of renewable energy systems, the control of inverters has become one of the most challenging problems, and especially photovoltaic and wind power generation systems have received much attention in recent years. The inverter plays a very important role in a power generation system as an interface between renewable energy and a power grid. At present, the demand for high-power three-level converters has become a trend. Due to the limited current rating of the active switches, parallel inverters are an ideal solution to achieve high power ratings. However, in order to avoid overload of a single inverter, it is necessary to suppress the circulating current.
The inventor finds that the current novel LCL filter can effectively inhibit the high-frequency common-mode leakage current of a three-level inverter system, and when the parallel three-level inverter system adopts the filter in the form, the high-frequency zero-sequence circulating current can also be effectively inhibited, but the method can cause the problem that the parallel system generates internal and external resonant circulating currents, so that the zero-sequence circulating current is increased suddenly, and the safety and the stability of the system are obviously reduced.
Disclosure of Invention
In order to solve the defects of the prior art, the invention provides a common-mode active damping resonance circulating current suppression system and a common-mode active damping resonance circulating current suppression method for an inverter parallel system, the parameters of a closed-loop PI controller are designed, the resonance circulating current suppression of a novel LCL filter parallel three-level inverter can be realized, and the problem of high system fault rate caused by overhigh zero-sequence circulating current of a modularized parallel three-level inverter is effectively solved.
In order to achieve the purpose, the following technical scheme is adopted in the disclosure:
a first aspect of the present disclosure provides a common-mode active damped resonant circulating current suppression system for an inverter parallel system.
A common-mode active damping resonant circulation suppression system of an inverter parallel system comprises at least two parallel three-level inverters, and a common point of a filter capacitor at the alternating current side of each inverter is connected with a neutral point at the direct current side.
A second aspect of the present disclosure provides a common-mode active damping resonant circulating current suppression method for an inverter parallel system.
A common-mode active damping resonant circulating current suppression method of an inverter parallel system utilizes the resonant circulating current suppression system of the first aspect of the disclosure, and comprises the following steps:
acquiring running state data of the resonant circulation current suppression system;
obtaining a control variable according to the obtained running state data, and adjusting the action time of a redundant small vector in three-level space vector modulation at the resonant frequency by using the control variable to adjust the resonant peak value so as to further realize the inhibition of resonant circulation;
and setting a reference value of the zero-sequence circulating current on the inverter side to be zero, and sending an error between the reference value and an actual value to the PI controller to obtain a control variable.
As an alternative embodiment, the zero-sequence loop transfer function is a third-order link.
As an optional implementation manner, the resonant frequency corresponding to the external resonant circulating current is obtained according to the inverter side inductor, the grid side inductor and the filter capacitor.
As an optional implementation manner, the resonance frequency corresponding to the internal resonant circulation current is obtained according to the inverter-side inductor and the filter capacitor.
As an alternative embodiment, the turning frequency of the PI controller is one seventh of the PWM switching frequency, and the cut-off frequency of the PI controller is one fifth of the PWM switching frequency.
As an optional implementation manner, the proportional coefficient of the PI controller is obtained according to the cut-off frequency of the PI controller, the inverter side inductor, the grid side inductor, the filter capacitor, the PWM switching period, and the equivalent gain and sampling delay time of the PI controller.
A third aspect of the present disclosure provides a common-mode active damped resonant circulating current suppression system for an inverter parallel system.
A common-mode active damping resonant circulating current suppression system for an inverter parallel system, comprising:
a data acquisition module configured to: acquiring running state data of the resonant circulation current suppression system; the resonant circulating current suppression system is a common-mode active damping resonant circulating current suppression system of an inverter parallel system, wherein the common point of an alternating current side filter capacitor of each inverter is connected to a direct current side neutral point through a lead;
a resonant circulating current suppression module configured to: obtaining a control variable according to the obtained running state data, and adjusting the action time of a redundant small vector in three-level space vector modulation at the resonant frequency by using the control variable to adjust the resonant peak value so as to further realize the inhibition of resonant circulation;
and setting a reference value of the zero-sequence circulating current on the inverter side to be zero, and sending an error between the reference value and an actual value to the PI controller to obtain a control variable.
A fourth aspect of the present disclosure provides a computer-readable storage medium, on which a program is stored, which when executed by a processor, implements the steps in the common-mode active damping resonant circulating current suppression method of the inverter parallel system according to the second aspect of the present disclosure.
A fifth aspect of the present disclosure provides an electronic device, including a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps in the method for suppressing common-mode active damping resonant circulating current of the inverter parallel system according to the second aspect of the present disclosure.
Compared with the prior art, the beneficial effect of this disclosure is:
1. according to the method, the system, the medium or the electronic equipment, parameters of the closed-loop PI controller are designed according to the stability of the system, the resonance circulating current suppression of the novel LCL filter parallel three-level inverter can be realized, and the problem of high system fault rate caused by overhigh zero-sequence circulating current of the modularized parallel three-level inverter is effectively solved.
2. The method, system, medium or electronic device of the present disclosure utilizes a parallel system to increase the rated power of a three-level inverter; by utilizing a novel LCL filter, high-frequency zero-sequence circulating current in a three-level parallel system is effectively inhibited; by controlling the zero-sequence loop current on the inverter side, the resonant loop current caused by a novel LCL filter in a three-level parallel system is effectively inhibited; the method is simple to implement, strong in expansibility of a parallel system, simple to apply and strong in practicability.
3. The method, the system, the medium or the electronic equipment adopt the PI regulator with the neutral point voltage balancing capability, and because the control target is not influenced by adjusting the redundant vector, the common-mode voltage can be changed by changing the duty ratio of the small vector, so that the resonance is inhibited, and the neutral point voltage is balanced.
Advantages of additional aspects of the disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the disclosure.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.
Fig. 1 is a structural diagram of an m parallel three-level inverter system based on a conventional LCL filter according to embodiment 1 of the present disclosure.
Fig. 2 is a zero sequence circulating current equivalent circuit of a three-level inverter parallel system based on a conventional LCL filter provided in embodiment 1 of the present disclosure.
Fig. 3 is a zero-sequence circulating current equivalent simplified circuit of the l < th > three-level inverter based on the conventional LCL filter provided in embodiment 1 of the present disclosure.
Fig. 4 is a structural diagram of a three-level inverter parallel system based on a novel LCL filter according to embodiment 1 of the present disclosure.
Fig. 5 is a zero sequence circulating current equivalent circuit of a three-level inverter parallel system based on a novel LCL filter provided in embodiment 1 of the present disclosure.
Fig. 6 is a zero sequence circulating current further simplified equivalent circuit of a three-level inverter parallel system based on a novel LCL filter provided in embodiment 1 of the present disclosure.
Fig. 7 is a bode diagram of zero sequence circulating transfer functions of three-level inverter parallel systems based on conventional and novel LCL filters according to embodiment 1 of the present disclosure.
Fig. 8 is an internal circulating current equivalent circuit of a three-level inverter parallel system based on a novel LCL filter provided in embodiment 1 of the present disclosure.
Fig. 9 is a bode diagram of a circulating current transfer function inside a three-level inverter parallel system based on a novel LCL filter provided in embodiment 1 of the present disclosure.
Fig. 10 is a block diagram of inverter-side zero-sequence circulating current control of a three-level inverter parallel system based on a novel LCL filter according to embodiment 1 of the present disclosure.
Fig. 11 shows the grid-side current, the zero-sequence circulating current and the THD simulation result of the novel LCL filter-based three-level inverter parallel system provided in embodiment 1 of the present disclosure (taking two inverters in parallel as an example).
Fig. 12 shows the inverter-side current, zero-sequence circulating current and THD simulation results (taking two inverters connected in parallel as an example) of the novel LCL filter-based three-level inverter parallel system provided in embodiment 1 of the present disclosure.
Detailed Description
The present disclosure is further described with reference to the following drawings and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The embodiments and features of the embodiments in the present disclosure may be combined with each other without conflict.
Example 1:
the embodiment 1 of the disclosure provides a common-mode active damping resonant circulating current suppression method for an inverter parallel system, which includes the following steps:
acquiring running state data of the resonant circulation current suppression system;
obtaining a control variable according to the obtained running state data, and adjusting the action time of a redundant small vector in three-level space vector modulation at the resonant frequency by using the control variable to adjust the resonant peak value so as to further realize the inhibition of resonant circulation;
and setting a reference value of the zero-sequence circulating current on the inverter side to be zero, and sending an error between the reference value and an actual value to the PI controller to obtain a control variable.
The resonant circulating current suppression system comprises at least two three-level inverters connected in parallel, and the common point of the filter capacitor at the alternating current side of each inverter is connected back to the neutral point at the direct current side through a lead.
Specifically, the method comprises the following steps:
fig. 1 shows a traditional LCL filter-based m parallel three-level grid-connected inverter system, in which positive and negative buses on the dc side are directly connected in parallel. In order to eliminate zero-sequence circulating current caused by different neutral point potentials among the inverters, the neutral points of the direct current sides of the inverters are connected together, and the alternating current sides of the inverters are connected with a power grid through an LCL filter. Wherein L is inverter side inductance, LgIs a grid side inductor, CfIs a filter capacitor.
And selecting the negative direct current bus voltage as a reference, and neglecting the equivalent series resistance of the filter for simplifying a system model and analyzing. According to kirchhoff voltage law, an average switch model of the ith three-level inverter is as follows:
Figure GDA0003475581090000071
wherein e isa、ebAnd ecFor three-phase mains voltage, VAl、VBlAnd VClFor the inverter output voltage, iAl、iBlAnd iClFor the current at the bridge arm side of the inverter, ial、iblAnd iclIs the net side current (l ═ 1,2, …, m), uNnThe voltage from the neutral point N of the power grid to the negative bus of the direct current side.
In the case of a balanced grid voltage, it is possible to obtain:
Figure GDA0003475581090000072
wherein, VZlIs the common mode voltage of the third inverter of the first stage. For transmissionIn the LCL filter, zero-sequence circulating current does not flow through a three-phase filter capacitor. Therefore, the zero-sequence circulating current on the inverter side is represented as:
Figure GDA0003475581090000073
fig. 2 is a zero sequence circulating current equivalent circuit diagram of a three-level inverter parallel system based on a traditional LCL filter. And obtaining the zero-sequence circulating current equivalent circuit of the parallel system of the three-level inverter according to the formula (2) and the formula (3).
Fig. 3 is a zero-sequence circulating current equivalent circuit of the l-th three-level inverter based on a traditional LCL filter. According to thevenin's theorem, the parallel inverter model is simplified into the form of a series voltage source with impedance. Therefore, the equivalent common-mode voltage of the other inverters except the first inverter is VZeIts equivalent series inductance is (L + L)g)/(n-1)。
VZeCan be expressed as:
Figure GDA0003475581090000074
zero-sequence circulating current i of the I-th inverter shown in FIG. 3zlA transfer function of
Figure GDA0003475581090000075
It can be seen that the transfer function of the zero-sequence loop current of the first inverter is a first-order system, and the excitation source of the first inverter is the difference V between the common-mode voltagesZl(s)-VZe(s)。
In a parallel system, because each inverter adopts an independent controller, the carrier waves among the inverters are difficult to realize complete synchronization, and the asynchronous carrier waves are VZl(s)-VZeThe high-frequency component is generated in(s), and the first-order system has limited inhibition capability on the high-frequency component, which is a main reason for generating high-frequency zero-sequence circulating current in the parallel system. Therefore, in order to reduce the high-frequency zero-sequence circulating current, the embodiment appliesA novel LCL filter (MLCL) and a corresponding control method are proposed.
Fig. 4 is a diagram of a parallel three-level inverter parallel system based on a novel LCL filter (MLCL). Different from a parallel system based on a traditional LCL filter, the common point of the filter capacitors on the alternating current side of each inverter in the figure 4 is connected back to the neutral point on the direct current side through a wire, the zero-sequence circulating current transfer function is high, the high-frequency zero-sequence circulating current problem can be effectively solved, and the resonant circulating current is also caused. The novel LCL filter enables a current circulation path to be added to a parallel system, and according to kirchhoff voltage law, an average model of a three-level inverter of the novel LCL filter is expressed as follows:
Figure GDA0003475581090000081
wherein ifal、ifblAnd ifclFor three-phase current, V, flowing through filter capacitorsNIs the voltage of the capacitor at the lower side of the direct current bus. Adding the three formulae in formula (6) to obtain:
Figure GDA0003475581090000082
inverter side zero sequence circulating current iZlNet side zero sequence circulation izlZero-sequence circulating current i flowing through capacitorfzlIs defined as:
Figure GDA0003475581090000083
fig. 5 is a zero sequence circulating current equivalent circuit of a three-level inverter parallel system based on a novel LCL filter. According to the formulas (7) and (8), it is possible to obtain:
Figure GDA0003475581090000091
according to the formulas (2) and (8), it is possible to obtain:
Figure GDA0003475581090000092
therefore, according to equations (9) and (10), an equivalent model of the three-level inverter of the novel LCL filter connected in parallel in fig. 5 can be obtained.
Fig. 6 is a zero sequence circulating current further simplified equivalent circuit of a three-level inverter parallel system based on a novel LCL filter. According to Thevenin's theorem, the equivalent common-mode voltages of the other inverters except the first inverter are VzeHaving a series impedance of Ze。Vze，ZeRespectively as follows:
Figure GDA0003475581090000093
Figure GDA0003475581090000094
fig. 6 shows the net side zero sequence circulating current i of the first new LCL filter inverterzlThe transfer function of (a) is:
Figure GDA0003475581090000095
FIG. 7 is a zero sequence loop transfer function G of a parallel system of three-level inverters based on a conventional LCL filter and based on a novel LCL filter1(s) and G2Bode diagram of(s). Compared with the conventional LCL filter, the capacitor CfIs introduced into the equivalent model to provide a low impedance path for the high frequency harmonics.
Zero sequence circulating transfer function (namely G) of three-level inverter parallel system when novel LCL filter is adopted2(s)) is a third-order link, and is based on the zero-sequence loop transfer function (namely G) of the parallel system of the traditional LCL filter1(s)) is a first order element. Therefore, the new LCL filter has a higher high frequency ringing cancellation capability than the conventional LCL filter, as shown in fig. 7.
However, the new LCL filter is at the resonant frequency fr1A resonance peak is generated, and the resonant circulating current caused by the resonance peak is defined as an External Resonant Circulating Current (ERCC).
Resonant frequency fr1Is defined as follows:
Figure GDA0003475581090000101
the resonant frequency is represented by filter parameter L, LgAnd CfAnd (4) jointly determining.
Fig. 8 is an internal circulating current equivalent circuit of a three-level inverter parallel system based on a novel LCL filter. Inverter side inductor L and filter capacitor CfIn series, forming an LC loop, a series resonance occurs. Internal circulating current i of the first invertercmclHas an excitation source of only VZlAt this time:
icmcl＝izfl (15)
for capacitive elements, VNNeglectably, the equivalent circuit is shown in fig. 8. To obtain an internal circulation icmclFor common mode voltage VZlThe transfer function of (a) is:
Figure GDA0003475581090000102
fig. 9 is a bode diagram of the internal circulating current transfer function of the novel LCL filter-based three-level inverter parallel system. It can be seen that at the resonant frequency fr2A resonance peak is generated, thereby generating an Internal Resonant Circulating Current (IRCC).
Resonant frequency fr2Expressed as:
Figure GDA0003475581090000103
fig. 10 is an inverter-side zero-sequence circulating current control block diagram of a three-level inverter parallel system based on a novel LCL filter. From the above analysis, a novel LCL filter based triple capacitorThe parallel inverter system can effectively inhibit high-frequency zero-sequence circulating current, but external resonant circulating current and internal resonant circulating current are introduced at the same time, so that the system is unstable. The internal and external resonant circulation currents are both caused by adding a capacitance branch circuit in the circulation loop. The excitation source of the internal and external resonant circulation currents is a common mode voltage, both of which are connected to VZl(s) are related, therefore, by controlling the quantity yzflAnd adjusting the action time of the redundant small vector in the three-level space vector modulation method, changing the amplitude of the common-mode voltage at the resonant frequency, and realizing the resonance circulating current suppression.
Therefore, the inverter-side zero-sequence current can be employed as a control target to suppress the resonant circulation current.
By adopting inversion side zero-sequence circulating current iZlThe closed-loop control of the inverter is used for inhibiting resonant circulation, and the excitation source of the zero-sequence circulation at the side of the inverter is VZe(s)-VZl(s)。
Therefore, the inverter-side zero-sequence circulating current model shown in fig. 6 is expressed as follows:
Figure GDA0003475581090000111
inverter side zero sequence circulating current iZlIs set to 0, the error between the reference value and the actual value is sent to the PI controller to obtain the control variable yZl：
Figure GDA0003475581090000112
From the equation (18), the excitation source of the inverter-side zero-sequence circulating current is VZe(s)-VZl(s). As can be seen from the control block diagram, the control variable y can be usedZlAnd adjusting the action time of the redundant small vector in the three-level space vector modulation at the resonance frequency to adjust the resonance peak value, thereby realizing the inhibition of resonance circulation.
The open loop transfer function of fig. 10 is represented as:
Figure GDA0003475581090000113
in the formula, a controller Gc(s) is a proportional controller, kpFor controlling the parameters, TsFor PWM switching period, KPWMFor its equivalent gain, TdIs the sample delay time. Time constant TsAnd TdAre small enough that they can be combined as:
Figure GDA0003475581090000114
thus, the open loop transfer function equation (20) may be expressed as:
Figure GDA0003475581090000115
the closed loop transfer function can be expressed as:
Figure GDA0003475581090000116
the characteristic equation can be expressed as:
Figure GDA0003475581090000126
according to the Laos-Helverz stability criterion, the sufficient requirements for system stability are as follows: k is a radical ofp>0 and τ>Tm。
In order to make the system achieve good response speed, the turning frequency of the PI controller is designed as follows:
Figure GDA0003475581090000121
it is possible to obtain:
Figure GDA0003475581090000122
in order to inhibit harmonic waves at the switching frequency introduced by the PWM module, the design rule of an engineering controller is combined, and the cut-off frequency f of the system iscThe following settings are set:
Figure GDA0003475581090000123
at the cut-off frequency, the magnitude of the open-loop transfer function is expressed as:
Figure GDA0003475581090000124
finally, the parameters of the controller can be found as follows:
Figure GDA0003475581090000125
example 2:
the embodiment 2 of the present disclosure provides a common-mode active damping resonant circulating current suppression system of an inverter parallel system, including:
a data acquisition module configured to: acquiring running state data of the resonant circulation current suppression system; the resonant circulating current suppression system is a common-mode active damping resonant circulating current suppression system of an inverter parallel system, wherein the common point of an alternating current side filter capacitor of each inverter is connected to a direct current side neutral point through a lead;
a resonant circulating current suppression module configured to: obtaining a control variable according to the obtained running state data, and adjusting the action time of a redundant small vector in three-level space vector modulation at the resonant frequency by using the control variable to adjust the resonant peak value so as to further realize the inhibition of resonant circulation;
and setting a reference value of the zero-sequence circulating current on the inverter side to be zero, and sending an error between the reference value and an actual value to the PI controller to obtain a control variable.
The working method of the system is the same as the common-mode active damping resonant circulating current suppression method of the inverter parallel system provided in embodiment 1, and details are not repeated here.
Example 3:
the embodiment 3 of the present disclosure provides a computer-readable storage medium, on which a program is stored, which when executed by a processor, implements the steps in the common mode active damping resonant circulating current suppression method of the inverter parallel system according to the embodiment 1 of the present disclosure.
Example 4:
the embodiment 4 of the present disclosure provides an electronic device, which includes a memory, a processor, and a program stored in the memory and executable on the processor, and when the processor executes the program, the processor implements the steps in the method for suppressing common-mode active damping resonant circulating current of the inverter parallel system according to the embodiment 1 of the present disclosure.
As will be appreciated by one skilled in the art, embodiments of the present disclosure may be provided as a method, system, or computer program product. Accordingly, the present disclosure may take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present disclosure 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, optical storage, and the like) having computer-usable program code embodied therein.
The present disclosure is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the disclosure. 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.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.
The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.

Claims (9)

1. A common-mode active damping resonance circulating current suppression method of an inverter parallel system utilizes a resonance circulating current suppression system, the resonance circulating current suppression system comprises at least two three-level inverters which are connected in parallel, and a common point of a filter capacitor at an alternating current side of each inverter is connected with a neutral point at a direct current side, and the common-mode active damping resonance circulating current suppression method is characterized in that: the method comprises the following steps:
acquiring running state data of the resonant circulation current suppression system;
obtaining a control variable according to the obtained running state data, and adjusting the action time of a redundant small vector in three-level space vector modulation at the resonant frequency by using the control variable to adjust the resonant peak value so as to further realize the inhibition of resonant circulation;
and setting a reference value of the zero-sequence circulating current on the inverter side to be zero, and sending an error between the reference value and an actual value to the PI controller to obtain a control variable.
2. The method of common-mode active damping resonant circulating current suppression for an inverter parallel system of claim 1, wherein:
the zero sequence circulation transfer function is a third-order link.
3. The method of common-mode active damping resonant circulating current suppression for an inverter parallel system of claim 1, wherein:
and obtaining the resonant frequency corresponding to the external resonant circulation according to the inverter side inductor, the power grid side inductor and the filter capacitor.
4. The method of common-mode active damping resonant circulating current suppression for an inverter parallel system of claim 1, wherein:
and obtaining the resonance frequency corresponding to the internal resonance circulating current according to the side inductor and the filter capacitor of the inverter.
5. The method of common-mode active damping resonant circulating current suppression for an inverter parallel system of claim 1, wherein:
the turning frequency of the PI controller is one seventh of the PWM switching frequency, and the cut-off frequency of the PI controller is one fifth of the PWM switching frequency.
6. The method of common-mode active damping resonant circulating current suppression for an inverter parallel system of claim 1, wherein:
and obtaining the proportional coefficient of the PI controller according to the cut-off frequency of the PI controller, the inverter side inductor, the grid side inductor, the filter capacitor, the PWM switching period, the equivalent gain of the PI controller and the sampling delay time.
7. A common mode active damping resonance circulating current suppression system of an inverter parallel system is characterized in that: the method comprises the following steps:
a data acquisition module configured to: acquiring running state data of the resonant circulation current suppression system; the resonance circulating current suppression system comprises at least two three-level inverters connected in parallel, and a common point of a filter capacitor at the alternating current side of each inverter is connected with a neutral point at the direct current side;
a resonant circulating current suppression module configured to: obtaining a control variable according to the obtained running state data, and adjusting the action time of a redundant small vector in three-level space vector modulation at the resonant frequency by using the control variable to adjust the resonant peak value so as to further realize the inhibition of resonant circulation;
and setting a reference value of the zero-sequence circulating current on the inverter side to be zero, and sending an error between the reference value and an actual value to the PI controller to obtain a control variable.
8. A computer readable storage medium having a program stored thereon, wherein the program when executed by a processor implements the steps in the method for common mode active damped resonant circulating current suppression of an inverter parallel system according to any one of claims 1 to 6.
9. An electronic device comprising a memory, a processor and a program stored on the memory and executable on the processor, wherein the processor implements the steps of the method for common mode active damped resonant circulating current suppression of inverter parallel system according to any one of claims 1 to 6 when executing the program.
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