CN117293901B - Grid-connected inverter control structure identification method, system, equipment and medium - Google Patents

Grid-connected inverter control structure identification method, system, equipment and medium Download PDF

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Publication number
CN117293901B
CN117293901B CN202311252961.7A CN202311252961A CN117293901B CN 117293901 B CN117293901 B CN 117293901B CN 202311252961 A CN202311252961 A CN 202311252961A CN 117293901 B CN117293901 B CN 117293901B
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fundamental frequency
negative sequence
impedance
grid
control
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CN117293901A (en
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王伟胜
黄勇
李光辉
张进
何国庆
吴福保
郭梓暄
刘可可
高丽萍
肖云涛
高彩云
雷雨
刘纯
甄妮
马俊华
王俊
余芳芳
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State Grid Henan Electric Power Co Zhengzhou Power Supply Co
State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
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State Grid Henan Electric Power Co Zhengzhou Power Supply Co
State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
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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
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/493—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode the static converters being arranged for operation in parallel
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention provides a grid-connected inverter control structure identification method, a system, equipment and a medium, comprising the following steps: after the grid-connected inverter is subjected to fundamental frequency negative sequence voltage disturbance, acquiring fundamental frequency negative sequence impedance of the grid-connected inverter; according to the fundamental frequency negative sequence impedance of the grid-connected inverter, calculating a difference value between the fundamental frequency negative sequence impedance and the acquired fundamental frequency positive sequence impedance, and calculating a ratio of the difference value to the fundamental frequency positive sequence impedance; determining the asymmetric control adoption condition of the grid-connected inverter according to the ratio of the difference value to the fundamental frequency positive sequence impedance; when the grid-connected inverter adopts an asymmetric control structure, based on the comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance, judging a control mode adopted by a negative sequence current control link in the asymmetric control structure.

Description

Grid-connected inverter control structure identification method, system, equipment and medium
Technical Field
The invention belongs to the technical field of new energy power generation, and particularly relates to a grid-connected inverter control structure identification method, a grid-connected inverter control structure identification system, grid-connected inverter control equipment and a grid-connected inverter control medium.
Background
At present, with the development and utilization of large-scale new energy, the stability problem of a new energy grid-connected system is increasingly raised, the problem of broadband oscillation frequently occurs, and the system safety and the efficient consumption of new energy are seriously affected. In recent years, an impedance analysis method becomes an important method for analyzing and solving the problem of large-scale new energy grid-connected oscillation, and the new energy power generation control characteristic has important influence on the impedance of a new energy port and the stability of a system.
The new energy converter manufacturer generally does not disclose the control adopted by the converter because of technical confidentiality, namely the black/gray box problem exists, which brings inconvenience to the accurate modeling of new energy power generation. There is a need to identify new energy power generation control modes, and construct a transparent structured electromagnetic transient model capable of accurately reflecting actual operation characteristics of new energy so as to facilitate system oscillation problem analysis, positioning and solving.
The grid-connected inverter is used as a grid-connected interface of the direct-drive/photovoltaic power generation unit, and the control characteristic of the grid-connected inverter determines the broadband stability of the grid-connected system. Aiming at the working condition of unbalanced power grid voltage or power grid fault, the grid-connected inverter can adopt asymmetric control, negative sequence current control is added on the basis of positive sequence current control, and unbalanced current of the grid-connected inverter is restrained or active power double frequency fluctuation is eliminated. Whether the grid-connected inverter adopts asymmetric control is important to the influence of port impedance characteristics and grid-connected system stability. For a black box model of the grid-connected inverter, control structure identification is a precondition and basis for control parameter identification. Because of the large number of direct drive/photovoltaic power generation manufacturers, various models and various control modes, how to identify the control structure of the black box model has great difficulty.
The existing direct-drive/photovoltaic power generation unit identifies control parameters of a grid-connected inverter black box model by adopting an optimization fitting algorithm based on grid-connected inverter port impedance data. The prior method has the following limitation problems: (1) The grid-connected inverter control structure is assumed to only consider positive sequence current control, control parameters are identified on the basis, and when the black box model control structure is inconsistent with the assumed control structure, insufficient identification precision of the control parameters is caused, and even the optimization fitting algorithm is not converged; (2) The direct-drive/photovoltaic power generation units have multiple models and complex control characteristics, and the control parameters based on a given control structure are identified, so that the control characteristics of the actual operation units are difficult to accurately reflect, and the electromagnetic transient modeling of the power generation units is inaccurate; (3) The black box model control structure identification research is less, and the grid-connected inverter control structure cannot be effectively identified.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a grid-connected inverter control structure identification method, which comprises the following steps:
after the grid-connected inverter is subjected to fundamental frequency negative sequence voltage disturbance, acquiring fundamental frequency negative sequence impedance of the grid-connected inverter;
according to the fundamental frequency negative sequence impedance of the grid-connected inverter, calculating a difference value between the fundamental frequency negative sequence impedance and the acquired fundamental frequency positive sequence impedance, and calculating a ratio of the difference value to the fundamental frequency positive sequence impedance;
Determining the asymmetric control adoption condition of the grid-connected inverter according to the ratio of the difference value to the fundamental frequency positive sequence impedance;
when the grid-connected inverter adopts an asymmetric control structure, judging a control mode adopted in a negative sequence current control link in the asymmetric control structure based on a comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance;
the fundamental frequency positive sequence impedance is the impedance of the grid-connected inverter in steady state operation.
Preferably, the determining the asymmetric control usage of the grid-connected inverter according to the ratio of the difference value to the fundamental frequency positive sequence impedance includes:
taking the ratio of the difference value to the fundamental frequency positive sequence impedance as the fundamental frequency negative sequence impedance amplitude ratio;
when the amplitude ratio of the fundamental frequency negative sequence impedance is larger than or equal to the negative sequence control sensitivity coefficient or the amplitude ratio of the fundamental frequency negative sequence impedance is smaller than or equal to the separation link sensitivity coefficient, the grid-connected inverter adopts an asymmetric control structure;
and when the amplitude ratio of the fundamental frequency negative sequence impedance is larger than the sensitivity coefficient of the separation link and the amplitude ratio of the fundamental frequency negative sequence impedance is smaller than the sensitivity coefficient of the negative sequence control, the grid-connected inverter does not adopt an asymmetric control structure.
Preferably, the expression corresponding to the fundamental frequency negative sequence impedance amplitude ratio is as follows:
wherein R represents the amplitude ratio of the negative sequence impedance of the fundamental frequency; z is Z n Representing the fundamental frequency negative sequence impedance; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant.
Preferably, the calculation formula corresponding to the negative sequence control sensitivity coefficient is as follows:
wherein a represents a negative sequence control sensitivity coefficient; v (V) n Representing the fundamental frequency negative sequence voltage; h is a n Representing the ratio of a maximum allowable negative sequence current control reference instruction of the grid-connected inverter to the fundamental frequency positive sequence current; v (V) p Representing the fundamental frequency positive sequence voltage; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant.
Preferably, the calculation formula corresponding to the sensitivity coefficient of the separation link is as follows:
wherein b represents a separation link sensitivity coefficient; v (V) n Representing the fundamental frequency negative sequence voltage; k (k) n Representing a margin coefficient; h is a n Representing the ratio of a maximum allowable negative sequence current control reference instruction of the grid-connected inverter to the fundamental frequency positive sequence current; v (V) p Representing the fundamental frequency positive sequence voltage; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant.
Preferably, the determining the control mode adopted by the negative sequence current control link in the asymmetric control structure based on the comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance includes:
When the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the inequality of active power balance control, an active power balance control mode is adopted in a negative sequence current control link in the asymmetric control structure;
when the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the reactive power balance control inequality, a negative sequence current control link in the asymmetric control structure adopts a reactive power balance control mode;
and when the active power balance control inequality and the reactive power balance control inequality are not satisfied between the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance, a negative sequence current control link in the asymmetric control structure adopts a current balance control mode.
Preferably, the active power balance control inequality is as follows:
|A log|Z n |-A log|Z np ||≤g·|A log|Z n ||
in the method, in the process of the invention,
wherein Z is n Representing the fundamental frequency negative sequence impedance; z is Z nP A theoretical impedance representing an active power balance control mode; g represents the accuracy tolerance; v (V) + Representing the magnitude of the fundamental frequency positive sequence voltage; v (V) - Representing the magnitude of the fundamental frequency negative sequence voltage; p (P) 0 Representing an active power stable value; j represents an imaginary unit; q (Q) 0 Representing a reactive power stable value; a represents a first association constant; b represents a second association constant; c represents a third association constant.
Preferably, the active power balance control inequality is as follows:
|A log|Z n |-A log|Z nQ ||≤g·|A log|Z n ||
in the method, in the process of the invention,
wherein Z is n Representing the fundamental frequency negativeA sequence impedance; z is Z nQ Representing the theoretical impedance of the reactive power balance control mode; g represents the accuracy tolerance; v (V) + Representing the magnitude of the fundamental frequency positive sequence voltage; v (V) - Representing the magnitude of the fundamental frequency negative sequence voltage; p (P) 0 Representing an active power stable value; j represents an imaginary unit; q (Q) 0 Representing a reactive power stable value; a represents a first association constant; b represents a second association constant; c represents a third association constant.
Preferably, the collecting the fundamental frequency negative sequence impedance of the grid-connected inverter includes:
collecting three-phase grid-connected voltage and three-phase grid-connected current after the grid-connected inverter is subjected to fundamental frequency negative sequence voltage disturbance;
performing information extraction on the three-phase grid-connected voltage by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency negative sequence voltage;
performing information extraction on the three-phase grid-connected current by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency negative sequence current;
and obtaining the fundamental frequency negative sequence impedance of the grid-connected inverter according to the fundamental frequency negative sequence voltage and the fundamental frequency negative sequence current.
Preferably, the fundamental frequency positive sequence impedance includes the following acquisition process:
When the grid-connected inverter runs in a steady state, collecting steady-state three-phase grid-connected voltage and steady-state three-phase grid-connected current of the grid-connected inverter;
performing information extraction on the steady-state three-phase grid-connected voltage by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency positive sequence voltage;
performing information extraction on the steady-state three-phase grid-connected current by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency positive sequence current;
and obtaining the fundamental frequency positive sequence impedance of the grid-connected inverter according to the fundamental frequency positive sequence voltage and the fundamental frequency positive sequence current.
Based on the same inventive concept, the invention further provides a grid-connected inverter control structure identification system, which comprises:
negative sequence impedance acquisition module: the method comprises the steps of after a grid-connected inverter is subjected to fundamental frequency negative sequence voltage disturbance, collecting fundamental frequency negative sequence impedance of the grid-connected inverter;
impedance duty ratio calculation module: the method comprises the steps of calculating a difference value between a fundamental frequency negative sequence impedance and an acquired fundamental frequency positive sequence impedance according to the fundamental frequency negative sequence impedance of the grid-connected inverter, and calculating a ratio of the difference value to the fundamental frequency positive sequence impedance;
and the control structure identification module is used for: the method is used for determining the asymmetric control adoption condition of the grid-connected inverter according to the ratio of the difference value to the fundamental frequency positive sequence impedance;
The control mode judging module: when the grid-connected inverter adopts an asymmetric control structure, judging a control mode adopted in a negative sequence current control link in the asymmetric control structure based on a comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance;
the fundamental frequency positive sequence impedance in the impedance duty ratio calculation module is the impedance of the grid-connected inverter in steady-state operation.
Preferably, the control structure identification module is specifically configured to:
taking the ratio of the difference value to the fundamental frequency positive sequence impedance as the fundamental frequency negative sequence impedance amplitude ratio;
when the amplitude ratio of the fundamental frequency negative sequence impedance is larger than or equal to the negative sequence control sensitivity coefficient or the amplitude ratio of the fundamental frequency negative sequence impedance is smaller than or equal to the separation link sensitivity coefficient, the grid-connected inverter adopts an asymmetric control structure;
and when the amplitude ratio of the fundamental frequency negative sequence impedance is larger than the sensitivity coefficient of the separation link and the amplitude ratio of the fundamental frequency negative sequence impedance is smaller than the sensitivity coefficient of the negative sequence control, the grid-connected inverter does not adopt an asymmetric control structure.
Preferably, the expression corresponding to the fundamental frequency negative sequence impedance amplitude ratio in the control structure identification module is as follows:
Wherein R represents the amplitude ratio of the negative sequence impedance of the fundamental frequency; z is Z n Representing the fundamental frequency negative sequence impedance; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant.
Preferably, the calculation formula corresponding to the negative sequence control sensitivity coefficient in the control structure identification module is as follows:
wherein a represents a negative sequence control sensitivity coefficient; v (V) n Representing the fundamental frequency negative sequence voltage; h is a n Representing the ratio of a maximum allowable negative sequence current control reference instruction of the grid-connected inverter to the fundamental frequency positive sequence current; v (V) p Representing the fundamental frequency positive sequence voltage; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant.
Preferably, the calculation formula corresponding to the sensitivity coefficient of the separation link in the control structure identification module is as follows:
wherein b represents a separation link sensitivity coefficient; v (V) n Representing the fundamental frequency negative sequence voltage; k (k) n Representing a margin coefficient; h is a n Representing the ratio of a maximum allowable negative sequence current control reference instruction of the grid-connected inverter to the fundamental frequency positive sequence current; v (V) p Representing the fundamental frequency positive sequence voltage; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant.
Preferably, the control mode judging module judges a control mode adopted by a negative sequence current control link in the asymmetric control structure based on a comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance, and includes:
When the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the inequality of active power balance control, an active power balance control mode is adopted in a negative sequence current control link in the asymmetric control structure;
when the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the reactive power balance control inequality, a negative sequence current control link in the asymmetric control structure adopts a reactive power balance control mode;
and when the active power balance control inequality and the reactive power balance control inequality are not satisfied between the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance, a negative sequence current control link in the asymmetric control structure adopts a current balance control mode.
Preferably, the active power balance control inequality in the control mode judging module is as follows:
|A log|Z n |-A log|Z np ||≤g·|A log|Z n ||
in the method, in the process of the invention,
wherein Z is n Representing the fundamental frequency negative sequence impedance; z is Z nP A theoretical impedance representing an active power balance control mode; g represents the accuracy tolerance; v (V) + Representing the magnitude of the fundamental frequency positive sequence voltage; v (V) - Representing the magnitude of the fundamental frequency negative sequence voltage; p (P) 0 Representing an active power stable value; j represents an imaginary unit; q (Q) 0 Representing a reactive power stable value; a represents a first association constant; b represents a second association constant; c represents a third association constant.
Preferably, the active power balance control inequality in the control mode judging module is as follows:
|A log|Z n |-A log|Z nQ ||≤g·|A log|Z n ||
in the method, in the process of the invention,
wherein Z is n Representing the fundamental frequency negative sequenceAn impedance; z is Z nQ Representing the theoretical impedance of the reactive power balance control mode; g represents the accuracy tolerance; v (V) + Representing the magnitude of the fundamental frequency positive sequence voltage; v (V) - Representing the magnitude of the fundamental frequency negative sequence voltage; p (P) 0 Representing an active power stable value; j represents an imaginary unit; q (Q) 0 Representing a reactive power stable value; a represents a first association constant; b represents a second association constant; c represents a third association constant.
Preferably, the collecting the fundamental frequency negative sequence impedance of the grid-connected inverter in the negative sequence impedance collecting module includes:
collecting three-phase grid-connected voltage and three-phase grid-connected current after the grid-connected inverter is subjected to fundamental frequency negative sequence voltage disturbance;
performing information extraction on the three-phase grid-connected voltage by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency negative sequence voltage;
performing information extraction on the three-phase grid-connected current by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency negative sequence current;
and obtaining the fundamental frequency negative sequence impedance of the grid-connected inverter according to the fundamental frequency negative sequence voltage and the fundamental frequency negative sequence current.
Preferably, the fundamental frequency positive sequence impedance in the impedance duty ratio calculation module includes the following acquisition process:
when the grid-connected inverter runs in a steady state, collecting steady-state three-phase grid-connected voltage and steady-state three-phase grid-connected current of the grid-connected inverter;
performing information extraction on the steady-state three-phase grid-connected voltage by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency positive sequence voltage;
performing information extraction on the steady-state three-phase grid-connected current by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency positive sequence current;
and obtaining the fundamental frequency positive sequence impedance of the grid-connected inverter according to the fundamental frequency positive sequence voltage and the fundamental frequency positive sequence current.
Based on the same inventive concept, the present invention further provides a computer device, comprising: one or more processors;
a memory for storing one or more programs;
when the one or more programs are executed by the one or more processors, a grid-connected inverter control structure identification method as described above is implemented.
Based on the same inventive concept, the present application further provides a computer readable storage medium, on which a computer program is stored, which when executed, implements a grid-connected inverter control structure identification method as described above.
Compared with the closest prior art, the invention has the following beneficial effects:
the invention provides a grid-connected inverter control structure identification method, a system, equipment and a medium, comprising the following steps: after the grid-connected inverter is subjected to fundamental frequency negative sequence voltage disturbance, acquiring fundamental frequency negative sequence impedance of the grid-connected inverter; according to the fundamental frequency negative sequence impedance of the grid-connected inverter, calculating a difference value between the fundamental frequency negative sequence impedance and the acquired fundamental frequency positive sequence impedance, and calculating a ratio of the difference value to the fundamental frequency positive sequence impedance; determining the asymmetric control adoption condition of the grid-connected inverter according to the ratio of the difference value to the fundamental frequency positive sequence impedance; when the grid-connected inverter adopts an asymmetric control structure, judging a control mode adopted in a negative sequence current control link in the asymmetric control structure based on a comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance; according to the invention, the control structure of the grid-connected inverter is identified by applying voltage disturbance to the grid-connected inverter and utilizing the internal relation between the fundamental frequency positive sequence impedance and the fundamental frequency negative sequence impedance, so that the identification accuracy of the control structure of the grid-connected inverter is improved; and according to the comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance, the control mode of the grid-connected inverter adopting the negative sequence current control link in the asymmetric control structure is further identified, and the identification integrity of the grid-connected inverter control structure is improved.
Drawings
FIG. 1 is a schematic flow chart of a method for identifying a control structure of a grid-connected inverter according to the present invention;
fig. 2 is a schematic diagram of a topology structure of a grid-connected inverter control structure identification method applied to a main circuit of a direct-drive/photovoltaic power generation unit according to the present invention;
FIG. 3 is a schematic diagram of a specific flow chart of a method for identifying a grid-connected inverter control structure applied to a direct-drive/photovoltaic power generation unit according to the present invention;
FIG. 4 is a schematic diagram of an asymmetric control structure of a grid-connected inverter control structure identification method applied to a positive and negative sequence separation link and a negative sequence current control link containing voltage and current in a direct-drive/photovoltaic power generation unit according to the present invention;
FIG. 5 is a schematic diagram of an asymmetric control structure of a grid-connected inverter control structure identification method applied to a direct-drive/photovoltaic power generation unit and only including a negative sequence current control link;
FIG. 6 is a schematic diagram of a control structure of a grid-connected inverter control structure identification method applied to a direct-drive/photovoltaic power generation unit without adopting asymmetric control according to the present invention;
FIG. 7 is a diagram of a negative sequence impedance plot of the fundamental frequency in an embodiment of the present invention;
FIG. 8 is a graph showing the amplitude of the negative sequence impedance of the fundamental frequency according to the embodiment of the present invention;
fig. 9 is a schematic structural diagram of a grid-connected inverter control structure identification system provided by the present invention.
Detailed Description
The following describes in further detail the embodiments of the present patent application with reference to the accompanying drawings.
Example 1:
the invention provides a grid-connected inverter control structure identification method, a flow diagram is shown in fig. 1, and the method comprises the following steps:
step 1: after the grid-connected inverter is subjected to fundamental frequency negative sequence voltage disturbance, acquiring fundamental frequency negative sequence impedance of the grid-connected inverter;
step 2: according to the fundamental frequency negative sequence impedance of the grid-connected inverter, calculating a difference value between the fundamental frequency negative sequence impedance and the acquired fundamental frequency positive sequence impedance, and calculating a ratio of the difference value to the fundamental frequency positive sequence impedance;
step 3: determining the asymmetric control adoption condition of the grid-connected inverter according to the ratio of the difference value to the fundamental frequency positive sequence impedance;
step 4: when the grid-connected inverter adopts an asymmetric control structure, judging a control mode adopted in a negative sequence current control link in the asymmetric control structure based on a comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance;
The fundamental frequency positive sequence impedance is the impedance of the grid-connected inverter in steady state operation.
Specifically, the collecting the fundamental frequency negative sequence impedance of the grid-connected inverter in the step 1 includes:
collecting three-phase grid-connected voltage and three-phase grid-connected current after the grid-connected inverter is subjected to fundamental frequency negative sequence voltage disturbance;
performing information extraction on the three-phase grid-connected voltage by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency negative sequence voltage;
performing information extraction on the three-phase grid-connected current by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency negative sequence current;
and obtaining the fundamental frequency negative sequence impedance of the grid-connected inverter according to the fundamental frequency negative sequence voltage and the fundamental frequency negative sequence current.
The fundamental frequency positive sequence impedance in the step 2 comprises the following acquisition processes:
when the grid-connected inverter runs in a steady state, collecting steady-state three-phase grid-connected voltage and steady-state three-phase grid-connected current of the grid-connected inverter;
performing information extraction on the steady-state three-phase grid-connected voltage by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency positive sequence voltage;
performing information extraction on the steady-state three-phase grid-connected current by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency positive sequence current;
And obtaining the fundamental frequency positive sequence impedance of the grid-connected inverter according to the fundamental frequency positive sequence voltage and the fundamental frequency positive sequence current.
Step 3, including:
taking the ratio of the difference value to the fundamental frequency positive sequence impedance as the fundamental frequency negative sequence impedance amplitude ratio;
when the amplitude ratio of the fundamental frequency negative sequence impedance is larger than or equal to the negative sequence control sensitivity coefficient or the amplitude ratio of the fundamental frequency negative sequence impedance is smaller than or equal to the separation link sensitivity coefficient, the grid-connected inverter adopts an asymmetric control structure;
and when the amplitude ratio of the fundamental frequency negative sequence impedance is larger than the sensitivity coefficient of the separation link and the amplitude ratio of the fundamental frequency negative sequence impedance is smaller than the sensitivity coefficient of the negative sequence control, the grid-connected inverter does not adopt an asymmetric control structure.
The expression corresponding to the fundamental frequency negative sequence impedance amplitude ratio is as follows:
wherein R represents the amplitude ratio of the negative sequence impedance of the fundamental frequency; z is Z n Representing the fundamental frequency negative sequence impedance; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant, preferably a=20.
The calculation formula corresponding to the negative sequence control sensitivity coefficient is as follows:
wherein a represents a negative sequence control sensitivity coefficient; v (V) n Representing the fundamental frequency negative sequence voltage; h is a n Representing the ratio of a maximum allowable negative sequence current control reference instruction of the grid-connected inverter to the fundamental frequency positive sequence current; v (V) p Representing the fundamental frequency positive sequence voltage; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant; preferably, a=20.
The calculation formula corresponding to the sensitivity coefficient of the separation link is as follows:
wherein b represents a separation link sensitivity coefficient; v (V) n Representing the fundamental frequency negative sequence voltage; k (k) n Representing a margin coefficient; h is a n Representing the ratio of a maximum allowable negative sequence current control reference instruction of the grid-connected inverter to the fundamental frequency positive sequence current; v (V) p Representing the fundamental frequency positive sequence voltage; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant, preferably a=20.
In step 4, based on the comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance, a control mode adopted by a negative sequence current control link in the asymmetric control structure is judged, including:
when the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the inequality of active power balance control, an active power balance control mode is adopted in a negative sequence current control link in the asymmetric control structure;
when the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the reactive power balance control inequality, a negative sequence current control link in the asymmetric control structure adopts a reactive power balance control mode;
When the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance do not meet the active power balance control inequality and the reactive power balance control inequality, a negative sequence current control link in the asymmetric control structure adopts a current balance control mode;
the active power balance control inequality is as follows:
|A log|Z n |-A log|Z np ||≤g·|A log|Z n ||
in the method, in the process of the invention,
wherein Z is n Representing the fundamental frequency negative sequence impedance; z is Z nP A theoretical impedance representing an active power balance control mode; g represents the accuracy tolerance; v (V) + Representing the magnitude of the fundamental frequency positive sequence voltage; v (V) - Representing the magnitude of the fundamental frequency negative sequence voltage; p (P) 0 Representing an active power stable value; j represents an imaginary unit; q (Q) 0 Representing a reactive power stable value; a represents a first association constant; b represents a second association constant; c represents a third association constant; preferably, a=20, b=3, c=2.
The active power balance control inequality is as follows:
|A log|Z n |-A log|Z nQ ||≤g·|A log|Z n ||
in the method, in the process of the invention,
wherein Z is n Representing the fundamental frequency negative sequence impedance; z is Z nQ Representing the theoretical impedance of the reactive power balance control mode; g represents the accuracy tolerance; v (V) + Representing the magnitude of the fundamental frequency positive sequence voltage; v (V) - Representing the magnitude of the fundamental frequency negative sequence voltage; p (P) 0 Representing an active power stable value; j represents an imaginary unit; q (Q) 0 Representing a reactive power stable value; a represents a first association constant; b represents a second association constant; c represents a third association constant; preferably, a=20, b=3, c=2.
According to the grid-connected inverter control structure identification method provided by the patent application, the fundamental frequency negative sequence impedance of the grid-connected inverter is measured by injecting the fundamental frequency negative sequence voltage disturbance small signal into the grid-connected inverter, the asymmetric control adoption condition of the grid-connected inverter is judged by checking whether the fundamental frequency negative sequence impedance amplitude ratio exceeds a set threshold value, and the control mode adopted by the negative sequence current control link is judged according to the comparison between the fundamental frequency negative sequence impedance amplitude and the theoretical impedance, so that the grid-connected inverter control structure identification is completed.
Example 2:
the grid-connected inverter control structure identification method provided by the invention is applied to a direct-drive/photovoltaic power generation unit in a specific embodiment, and as shown in fig. 2, the topology structure of the direct-drive/photovoltaic power generation unit comprises: an input current source 01, a direct current bus capacitor 02, a grid-connected inverter 03, a filter 04, a circuit breaker 05, a disturbance voltage source 06 and a power grid 07. The input current source 01 is connected to the direct current bus capacitor 02 and then connected with a direct current port of the grid-connected inverter 03. The ac port of the grid-connected inverter 03 is connected to the circuit breaker 05 via the filter 04, and then connected to the disturbance voltage source 06 and then connected to the grid 07. The grid-connected inverter 03 adopts a three-phase full-bridge circuit, and PWM signals control the grid-connected inverter 03 to operate, wherein i is as follows ga 、i gb 、i gc Is three-phase alternating current of grid-connected inverter, i a 、i b 、i c V is three-phase grid-connected current a 、v b 、v c Is three-phase grid-connected voltage.
As shown in fig. 3, the specific implementation steps include:
in step S1, the output of the disturbance voltage source 06 is set to zero, and the grid-connected inverter 03 is started after the circuit breaker 05 is closed, so that the active power is increased, and preferably, the grid-connected inverter operates at rated power.
Step S2, when the grid-connected inverter runs stably, three-phase grid-connected voltage v is collected a 、v b 、v c And three-phase grid-connected current i a 、i b 、i c Is recorded as a steady-state three-phase grid-connected voltage v a1 、v b1 、v c1 And steady-state three-phase grid-connected current i a1 、i b1 、i c1 The fundamental frequency positive sequence voltage V is obtained through extraction by fast Fourier transform analysis and a symmetrical component method p And fundamental frequency positive sequence current I p Determining fundamental frequency positive sequence impedance Z of grid-connected inverter p ＝-V p /I p Fundamental frequency positive sequence voltage amplitude V + ＝|V p |。
Step S3, continuously injecting a fundamental frequency negative sequence voltage disturbance small signal with the set time length T seconds into the disturbance voltage source 06, wherein the amplitude of the fundamental frequency negative sequence voltage disturbance small signal is the fundamental frequency positive sequence voltage V p Is k times the fundamental frequency negativeThe three-phase expression of the sequence voltage disturbance small signal is as follows:
wherein v is an Representing a phase a fundamental frequency negative sequence voltage disturbance small signal; v bn Representing b-phase fundamental frequency negative sequence voltage disturbance small signals; v cn Representing a c-phase fundamental frequency negative sequence voltage disturbance small signal; omega 1 Is the fundamental angular frequency;the phase of the disturbance signal of the fundamental frequency negative sequence voltage is set; k represents the multiple of the fundamental frequency positive sequence voltage of the fundamental frequency negative sequence voltage disturbance small signal; v (V) p Representing the fundamental frequency positive sequence voltage; step S4 is started while the disturbance voltage source 06 outputs a fundamental frequency negative sequence voltage disturbance small signal.
Step S4, collecting three-phase grid-connected voltage v a 、v b 、v c And three-phase grid-connected current i a 、i b 、i c Recorded as disturbance three-phase grid-connected voltage v a2 、v b2 、v c2 And disturbance three-phase grid-connected current i a2 、i b2 、i c2 。
Step S5, the disturbance three-phase grid-connected voltage v acquired in the step S4 is subjected to a2 、v b2 、v c2 And disturbance three-phase grid-connected current i a2 、i b2 、i c2 Performing fast Fourier transform analysis and symmetrical component method to obtain fundamental frequency negative sequence voltage V n And fundamental frequency negative sequence current I n Determining fundamental frequency negative sequence impedance Z of grid-connected inverter n ＝-V n /I n And the amplitude V of the fundamental frequency negative sequence voltage - ＝|V n |；
Step S6, according to the disturbance three-phase grid-connected voltage v acquired in the step S4 a2 、v b2 、v c2 And disturbance three-phase grid-connected current i a2 、i b2 、i c2 Calculating to obtain active power P and reactive power q, and filtering by a sliding window filter to obtain an active power stable value P 0 And reactive power stabilization value Q 0 。
S7, checking whether the amplitude ratio of the negative sequence impedance of the fundamental frequency exceeds a threshold value, and judging whether the grid-connected inverter adopts an asymmetric control structure; in order to eliminate the influence of impedance change on a threshold value under different power operation points of the grid-connected inverter, a fundamental frequency negative sequence impedance amplitude ratio expression is defined as follows:
Wherein R represents the amplitude ratio of the negative sequence impedance of the fundamental frequency; z n I represents the magnitude of the negative sequence impedance of the fundamental frequency, Z p I is the magnitude of the fundamental positive sequence impedance;
identifying a control structure of the grid-connected inverter by judging the meeting condition of the amplitude ratio of the negative sequence impedance of the fundamental frequency:
(1) Condition 1: when R is more than or equal to a, judging that the grid-connected inverter adopts asymmetric control, wherein the asymmetric control comprises a voltage-current positive-negative sequence separation link and a negative sequence current control link; a is a negative sequence control sensitivity coefficient, and the calculation formula is as follows:
wherein V is n Representing the fundamental frequency negative sequence voltage; h is a n Controlling the ratio of a reference instruction and fundamental frequency positive sequence current for the maximum allowable negative sequence current of the grid-connected inverter; v (V) p Representing the fundamental frequency positive sequence voltage; z is Z p Representing the magnitude of the fundamental positive sequence impedance.
(2) Condition 2: when R is less than or equal to b, judging that the grid-connected inverter adopts asymmetric control, wherein the grid-connected inverter comprises a voltage and current positive and negative sequence separation link, but does not comprise a negative sequence current control link; b is a sensitivity coefficient of the separation link, and the calculation formula is as follows:
wherein k is n Is of a marginCoefficient of degree, preferably, k n ＞1；V n Representing the fundamental frequency negative sequence voltage; h is a n Controlling the ratio of a reference instruction and fundamental frequency positive sequence current for the maximum allowable negative sequence current of the grid-connected inverter; v (V) p Representing the fundamental frequency positive sequence voltage; z is Z p Representing the fundamental positive sequence impedance.
(3) Condition 3: and when b is less than R and less than a, judging that the grid-connected inverter does not adopt asymmetric control.
Step S8, when the identification result in step S7 meets the condition 1, the control mode adopted in the negative sequence current control link is further judged according to the comparison between the fundamental frequency negative sequence impedance amplitude and the theoretical impedance calculation result:
when the theoretical impedance calculation result under the fundamental frequency negative sequence impedance and the active power balance control meets the following relation of the active power balance control inequality, the negative sequence current control link is judged to adopt an active power balance control mode, namely the secondary fluctuation of active power under the unbalance of the power grid voltage is eliminated, and the active power balance control inequality is as follows:
|20log|Z n |-20log|Z np ||≤g·|20log|Z n ||
wherein, |Z n I represents the magnitude of the negative sequence impedance of the fundamental frequency; z np I represents the magnitude of theoretical impedance under active power balance control; g is an accuracy allowance deviation set in consideration of the influence of measurement errors;
wherein Z is nP Representing theoretical impedance under active power balance control; v (V) + Representing the magnitude of the fundamental frequency positive sequence voltage; v (V) - Representing the magnitude of the fundamental frequency negative sequence voltage;to the fourth power of the fundamental positive sequence voltage; />To the fourth power of the fundamental negative sequence voltage; />Is the square of the fundamental positive sequence voltage; / >Is the square of the fundamental negative sequence voltage; j is an imaginary unit; p (P) 0 Representing an active power stable value; q (Q) 0 Representing reactive power stable values.
When the fundamental frequency negative sequence impedance and the theoretical impedance under reactive power balance control meet the relation of the following reactive power balance control inequality, judging that a reactive power balance control mode is adopted in the negative sequence current control link, namely, eliminating the secondary fluctuation of reactive power under unbalanced power grid voltage; the reactive power balance control inequality is as follows:
|20log|Z n |-20log|Z nQ ||≤g·|20log|Z n ||
wherein, |Z n I represents the magnitude of the negative sequence impedance of the fundamental frequency; z nQ The I represents the amplitude of theoretical impedance under reactive power balance control; g is an accuracy allowance deviation set in consideration of the influence of measurement errors;
in the reactive power balance control, theoretical impedance Z nQ The expression is as follows:
wherein Z is nQ Representing theoretical impedance under reactive power balance control; v (V) + Representing the magnitude of the fundamental frequency positive sequence voltage; v (V) - Representing the magnitude of the fundamental frequency negative sequence voltage;to the fourth power of the fundamental positive sequence voltage; />To the fourth power of the fundamental negative sequence voltage; />Is the square of the fundamental positive sequence voltage; />Is the square of the fundamental negative sequence voltage; j is an imaginary unit; p (P) 0 Representing an active power stable value; q (Q) 0 Representing reactive power stable values.
When the active power balance control inequality and the reactive power balance control inequality are not satisfied, judging that the grid-connected inverter adopts a current balance control mode in a negative sequence current control link, namely, maintaining three-phase current balance under unbalanced grid voltage.
In step S7, the asymmetric control structure including the step of separating the positive sequence from the negative sequence of the voltage and the current is shown in fig. 4; the voltage and current positive and negative sequence separation link is realized by receiving three-phase grid-connected voltage v a 、v b 、v c And grid-connected inverter three-phase alternating current i ga 、i gb 、i gc After sampling the signal, separating to obtain three-phase positive sequence voltage v a+ 、v b+ 、v c+ Three-phase negative sequence voltage v a- 、v b- 、v c- Three-phase positive sequence current i ga+ 、i gb+ 、i gc+ Three-phase negative sequence current i ga- 、i gb- 、i gc- The method comprises the steps of carrying out a first treatment on the surface of the Three-phase positive sequence voltage v a+ 、v b+ 、v c+ Inputting the synchronous rotation reference angle theta into a phase-locked loop; three-phase positive sequence current i ga+ 、i gb+ 、i gc+ The synchronous rotation reference angle theta is input to a positive sequence current control link, and a positive sequence d-axis current reference instruction i is generated by a direct current voltage ring dref+ The reactive power loop generates a positive sequence q-axis current reference command i qref+ The method comprises the steps of carrying out a first treatment on the surface of the Three-phase negative sequence current i ga- 、i gb- 、i gc- Three-phase negative sequence voltage v a- 、v b- 、v c- And reversely synchronously rotating the reference angle-theta, and inputting the reference angle-theta into a negative sequence current control link; the positive sequence current control link and the negative sequence current control link jointly generate modulation waves, and PWM signals of the grid-connected inverter are generated through the modulation module. Negative sequence current control The control modes of the links comprise an active power balance control mode, a reactive power balance control mode and a current balance control mode.
In the active power balance control mode, a negative sequence d-axis current reference instruction i dref- Negative sequence q-axis current reference command i qref- The following respectively satisfy:
in reactive power balance control mode, negative sequence d-axis current reference instruction i dref- Negative sequence q-axis current reference command i qref- The following respectively satisfy:
wherein i is dref- Representing a negative sequence d-axis current reference command; i.e qref- Representing a negative sequence q-axis current reference command; p (P) ref Representing an active power reference command; q (Q) ref Is a reactive power reference command;is negative sequence d-axis voltage; v q - Is a negative sequence q-axis voltage; v (V) + Representing the magnitude of the fundamental frequency positive sequence voltage; v (V) - Representing the magnitude of the fundamental negative sequence voltage.
In the current balance control mode, a negative sequence d-axis current reference command i dref- Negative sequence q-axis current reference command i qref- The following respectively satisfy:
the asymmetric control structure including the step of separating the positive sequence from the negative sequence of the voltage and the current in the step S5 is shown in fig. 5. The voltage and current positive and negative sequence separation link is realized by receiving three-phase grid-connected voltage v a 、v b 、v c And grid-connected inverter three-phase alternating currentStream i ga 、i gb 、i gc After sampling the signal, separating to obtain three-phase positive sequence voltage v a+ 、v b+ 、v c+ And three-phase positive sequence current i ga+ 、i gb+ 、i gc+ The method comprises the steps of carrying out a first treatment on the surface of the Three-phase positive sequence voltage v a+ 、v b+ 、v c+ Inputting the synchronous rotation reference angle theta into a phase-locked loop; three-phase positive sequence current i ga+ 、i gb+ 、i gc+ The synchronous rotation reference angle theta is input to a positive sequence current control link, and a positive sequence d-axis current reference instruction i is generated by a direct current voltage ring dref+ The reactive power loop generates a positive sequence q-axis current reference command i qref+ The method comprises the steps of carrying out a first treatment on the surface of the And generating a modulation wave by a positive sequence current control link, and generating a PWM signal of the grid-connected inverter through a modulation module.
In step S5, the control structure without asymmetric control is shown in FIG. 6, and the three-phase grid-connected voltage v a 、v b 、v c Inputting the synchronous rotation reference angle theta into a phase-locked loop; three-phase alternating current i of grid-connected inverter ga 、i gb 、i gc Input to the positive sequence current control link, and simultaneously generate a positive sequence d-axis current reference instruction i by the direct current voltage ring dref+ The reactive power loop generates a positive sequence q-axis current reference command i qref+ The method comprises the steps of carrying out a first treatment on the surface of the And generating a modulation wave by a positive sequence current control link, and generating a PWM signal of the grid-connected inverter through a modulation module.
In the example, the control structure of the grid-connected inverter of three 3MW direct-driven wind turbines is identified, and as shown in FIG. 7, a negative sequence impedance curve of 1-100 Hz and a magnitude ratio curve of the negative sequence impedance relative to the fundamental frequency positive sequence impedance are provided, wherein the magnitude of the fundamental frequency positive sequence impedance is-15.99 dB, and the magnitude of the fundamental frequency positive sequence voltage is V + 563.4V, the amplitude of the fundamental frequency negative sequence voltage V - Active power stable value P of 28.2V 0 3MW, reactive power stable value Q 0 The accuracy allowable deviation g was 0.1, which was 0.3 Mvar. Maximum allowable negative sequence current control reference instruction of grid-connected inverter and ratio h of fundamental frequency positive sequence current n Is 0.1, margin coefficient k n Taking 4, the negative sequence control sensitivity coefficient a is calculated to be-0.38, and the separation link is sensitiveThe inductance b is-1.13. According to the fundamental frequency negative sequence impedance amplitude ratio calculation type, the fundamental frequency negative sequence impedance amplitude ratio of a graph containing circles is 1.167 under 50Hz, the condition 1 is satisfied, the model 1 direct-drive wind turbine generator is identified to adopt asymmetric control, and an asymmetric control link comprises a voltage current positive and negative sequence separation link and a negative sequence current control link. And the calculated active power balance control inequality and reactive power balance control inequality are not satisfied, and the current balance control mode can be adopted in the negative sequence current control link.
In FIG. 8, the amplitude ratio of the fundamental frequency negative sequence impedance of the triangle-containing curve at 50Hz is-1.943, the condition 2 is satisfied, the model 2 direct-drive wind turbine generator system is identified to adopt asymmetric control, and the asymmetric control link only comprises a voltage-current positive-negative sequence separation link. In fig. 8, the amplitude ratio of the fundamental frequency negative sequence impedance of the dotted line at 50Hz is-0.815, and the condition 3 is satisfied, so that the model 3 direct-drive wind turbine generator system is identified to not adopt asymmetric control, and therefore, the identification result of the grid-connected inverter control structure in the actual direct-drive/photovoltaic power generation unit conforms to the control structure of the actual controller by adopting the identification result of the grid-connected inverter control structure provided by the invention, and the grid-connected inverter control structure can be effectively identified.
Example 3:
based on the same inventive concept, the present invention further provides a grid-connected inverter control structure identification system, the structural composition schematic diagram is shown in fig. 9, and the system comprises:
negative sequence impedance acquisition module: the method comprises the steps of after a grid-connected inverter is subjected to fundamental frequency negative sequence voltage disturbance, collecting fundamental frequency negative sequence impedance of the grid-connected inverter;
impedance duty ratio calculation module: the method comprises the steps of calculating a difference value between a fundamental frequency negative sequence impedance and an acquired fundamental frequency positive sequence impedance according to the fundamental frequency negative sequence impedance of the grid-connected inverter, and calculating a ratio of the difference value to the fundamental frequency positive sequence impedance;
and the control structure identification module is used for: the method is used for determining the asymmetric control adoption condition of the grid-connected inverter according to the ratio of the difference value to the fundamental frequency positive sequence impedance;
the control mode judging module: when the grid-connected inverter adopts an asymmetric control structure, judging a control mode adopted in a negative sequence current control link in the asymmetric control structure based on a comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance;
the fundamental frequency positive sequence impedance in the impedance duty ratio calculation module is the impedance of the grid-connected inverter in steady-state operation.
The negative sequence impedance acquisition module acquires the fundamental frequency negative sequence impedance of the grid-connected inverter, and comprises the following steps:
collecting three-phase grid-connected voltage and three-phase grid-connected current after the grid-connected inverter is subjected to fundamental frequency negative sequence voltage disturbance;
performing information extraction on the three-phase grid-connected voltage by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency negative sequence voltage;
performing information extraction on the three-phase grid-connected current by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency negative sequence current;
and obtaining the fundamental frequency negative sequence impedance of the grid-connected inverter according to the fundamental frequency negative sequence voltage and the fundamental frequency negative sequence current.
The fundamental frequency positive sequence impedance in the impedance duty ratio calculation module comprises the following acquisition processes:
when the grid-connected inverter runs in a steady state, collecting steady-state three-phase grid-connected voltage and steady-state three-phase grid-connected current of the grid-connected inverter;
performing information extraction on the steady-state three-phase grid-connected voltage by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency positive sequence voltage;
performing information extraction on the steady-state three-phase grid-connected current by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency positive sequence current;
And obtaining the fundamental frequency positive sequence impedance of the grid-connected inverter according to the fundamental frequency positive sequence voltage and the fundamental frequency positive sequence current.
The control structure identification module is specifically configured to:
taking the ratio of the difference value to the fundamental frequency positive sequence impedance as the fundamental frequency negative sequence impedance amplitude ratio;
when the amplitude ratio of the fundamental frequency negative sequence impedance is larger than or equal to the negative sequence control sensitivity coefficient or the amplitude ratio of the fundamental frequency negative sequence impedance is smaller than or equal to the separation link sensitivity coefficient, the grid-connected inverter adopts an asymmetric control structure;
and when the amplitude ratio of the fundamental frequency negative sequence impedance is larger than the sensitivity coefficient of the separation link and the amplitude ratio of the fundamental frequency negative sequence impedance is smaller than the sensitivity coefficient of the negative sequence control, the grid-connected inverter does not adopt an asymmetric control structure.
The expression corresponding to the fundamental frequency negative sequence impedance amplitude ratio in the control structure identification module is as follows:
wherein R represents the amplitude ratio of the negative sequence impedance of the fundamental frequency; z is Z n Representing the fundamental frequency negative sequence impedance; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant.
The calculation formula corresponding to the negative sequence control sensitivity coefficient in the control structure identification module is as follows:
wherein a represents a negative sequence control sensitivity coefficient; v (V) n Representing the fundamental frequency negative sequence voltage; h is a n Representing the ratio of a maximum allowable negative sequence current control reference instruction of the grid-connected inverter to the fundamental frequency positive sequence current; v (V) p Representing the fundamental frequency positive sequence voltage; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant.
The calculation formula corresponding to the separation link sensitivity coefficient in the control structure identification module is as follows:
wherein b represents a separation link sensitivity coefficient; v (V) n Representing the fundamental frequency negative sequence voltage; k (k) n Representing a margin coefficient; h is a n Representing the ratio of a maximum allowable negative sequence current control reference instruction of the grid-connected inverter to the fundamental frequency positive sequence current; v (V) p Representing the fundamental frequency positive sequence voltage; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant.
The control mode judging module judges a control mode adopted by a negative sequence current control link in the asymmetric control structure based on a comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance, and comprises the following steps:
when the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the inequality of active power balance control, an active power balance control mode is adopted in a negative sequence current control link in the asymmetric control structure;
when the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the reactive power balance control inequality, a negative sequence current control link in the asymmetric control structure adopts a reactive power balance control mode;
And when the active power balance control inequality and the reactive power balance control inequality are not satisfied between the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance, a negative sequence current control link in the asymmetric control structure adopts a current balance control mode.
The active power balance control inequality in the control mode judging module is as follows:
|A log|Z n |-A log|Z np ||≤g·|A log|Z n ||
in the method, in the process of the invention,
wherein Z is n Representing the fundamental frequency negative sequence impedance; z is Z nP A theoretical impedance representing an active power balance control mode; g represents the accuracy tolerance; v (V) + Representing fundamental frequency positive sequence electricityThe magnitude of the pressure; v (V) - Representing the magnitude of the fundamental frequency negative sequence voltage; p (P) 0 Representing an active power stable value; j represents an imaginary unit; q (Q) 0 Representing a reactive power stable value; a represents a first association constant; b represents a second association constant; c represents a third association constant.
The active power balance control inequality in the control mode judging module is as follows:
|A log|Z n |-A log|Z nQ ||≤g·|A log|Z n ||
in the method, in the process of the invention,
wherein Z is n Representing the fundamental frequency negative sequence impedance; z is Z nQ Representing the theoretical impedance of the reactive power balance control mode; g represents the accuracy tolerance; v (V) + Representing the magnitude of the fundamental frequency positive sequence voltage; v (V) - Representing the magnitude of the fundamental frequency negative sequence voltage; p (P) 0 Representing an active power stable value; j represents an imaginary unit; q (Q) 0 Representing a reactive power stable value; a represents a first association constant; b represents a second association constant; c represents a third association constant.
Example 4:
based on the same inventive concept, the present application also provides a computer device comprising a processor and a memory for storing a computer program comprising program instructions, the processor being adapted to execute the program instructions stored by the computer storage medium. The processor may be a central processing unit (Central Processing Unit, CPU), but may also be other general purpose processor, digital signal processor (Digital Signal Processor, DSP), application specific integrated circuit (Application SpecificIntegrated Circuit, ASIC), off-the-shelf Programmable gate array (FPGA) or other Programmable logic device, discrete gate or transistor logic device, discrete hardware components, etc., which are the computing core and control core of the terminal adapted to implement one or more instructions, in particular to load and execute one or more instructions in a computer storage medium to implement the corresponding method flow or corresponding functions, to implement the steps of a grid-tie inverter control structure identification method in the above embodiments.
Example 5:
based on the same inventive concept, the present application also provides a storage medium, in particular a computer readable storage medium (Memory), which is a Memory device in a computer device, for storing programs and data. It is understood that the computer readable storage medium herein may include both built-in storage media in a computer device and extended storage media supported by the computer device. The computer-readable storage medium provides a storage space storing an operating system of the terminal. Also stored in the memory space are one or more instructions, which may be one or more computer programs (including program code), adapted to be loaded and executed by the processor. The computer readable storage medium herein may be a high-speed RAM memory or a non-volatile memory (non-volatile memory), such as at least one magnetic disk memory. One or more instructions stored in a computer-readable storage medium may be loaded and executed by a processor to implement the steps of a grid-tie inverter control structure identification method in the above embodiments.
It will be appreciated by those skilled in the art that embodiments of the present patent application may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present patent application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, magnetic disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.
The present patent 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 invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations 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 should be noted that the above embodiments are only used for illustrating the technical solution of the present application and not limiting the scope of protection of the present application, and although the detailed description of the present application is given with reference to the above embodiments, it should be understood that those skilled in the art may make various changes, modifications or equivalents to the specific embodiments of the application after reading the present application, and these changes, modifications or equivalents are within the scope of protection of the claims filed herewith.

Claims (11)

1. The grid-connected inverter control structure identification method is characterized by comprising the following steps of:
after the grid-connected inverter is subjected to fundamental frequency negative sequence voltage disturbance, acquiring fundamental frequency negative sequence impedance of the grid-connected inverter;
according to the fundamental frequency negative sequence impedance of the grid-connected inverter, calculating a difference value between the fundamental frequency negative sequence impedance and the acquired fundamental frequency positive sequence impedance, and calculating a ratio of the difference value to the fundamental frequency positive sequence impedance;
determining the asymmetric control adoption condition of the grid-connected inverter according to the ratio of the difference value to the fundamental frequency positive sequence impedance;
when the grid-connected inverter adopts an asymmetric control structure, judging a control mode adopted in a negative sequence current control link in the asymmetric control structure based on a comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance;
the fundamental frequency positive sequence impedance is the impedance of the grid-connected inverter in steady state operation;
and determining an asymmetric control adoption condition of the grid-connected inverter according to the ratio of the difference value to the fundamental frequency positive sequence impedance, wherein the asymmetric control adoption condition comprises the following steps:
taking the ratio of the difference value to the fundamental frequency positive sequence impedance as the fundamental frequency negative sequence impedance amplitude ratio;
when the amplitude ratio of the fundamental frequency negative sequence impedance is larger than or equal to the negative sequence control sensitivity coefficient or the amplitude ratio of the fundamental frequency negative sequence impedance is smaller than or equal to the separation link sensitivity coefficient, the grid-connected inverter adopts an asymmetric control structure;
When the amplitude ratio of the fundamental frequency negative sequence impedance is larger than the sensitivity coefficient of the separation link and the amplitude ratio of the fundamental frequency negative sequence impedance is smaller than the sensitivity coefficient of the negative sequence control, the grid-connected inverter does not adopt an asymmetric control structure;
the expression corresponding to the fundamental frequency negative sequence impedance amplitude ratio is as follows:
wherein R represents the amplitude ratio of the negative sequence impedance of the fundamental frequency; z is Z n Representing the fundamental frequency negative sequence impedance; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant;
the judging the control mode adopted by the negative sequence current control link in the asymmetric control structure based on the comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance comprises the following steps:
when the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the inequality of active power balance control, an active power balance control mode is adopted in a negative sequence current control link in the asymmetric control structure;
when the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the reactive power balance control inequality, a negative sequence current control link in the asymmetric control structure adopts a reactive power balance control mode;
and when the active power balance control inequality and the reactive power balance control inequality are not satisfied between the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance, a negative sequence current control link in the asymmetric control structure adopts a current balance control mode.
2. The method of claim 1, wherein the negative sequence control sensitivity coefficient corresponds to the following formula:
wherein a represents a negative sequence control sensitivity coefficient; v (V) n Representing the fundamental frequency negative sequence voltage; h is a n Representing the ratio of a maximum allowable negative sequence current control reference instruction of the grid-connected inverter to the fundamental frequency positive sequence current; v (V) p Representing the fundamental frequency positive sequence voltage; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant.
3. The method of claim 1, wherein the separation element sensitivity coefficient corresponds to the following formula:
wherein b represents a separation link sensitivity coefficient; v (V) n Representing the fundamental frequency negative sequence voltage; k (k) n Representing a margin coefficient; h is a n Representing the ratio of a maximum allowable negative sequence current control reference instruction of the grid-connected inverter to the fundamental frequency positive sequence current; v (V) p Representing the fundamental frequency positive sequence voltage; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant.
4. The method of claim 1, wherein the active power balance control inequality is as follows:
wherein Z is n Representing the fundamental frequency negative sequence impedance; z is Z nP A theoretical impedance representing an active power balance control mode; g represents the accuracy tolerance; v (V) + Representing the magnitude of the fundamental frequency positive sequence voltage; v (V) - Representing the magnitude of the fundamental frequency negative sequence voltage; p (P) 0 Representing an active power stable value; j represents an imaginary unit; q (Q) 0 Representing a reactive power stable value; a represents a first association constant; b represents a second association constant; c represents a third association constant.
5. The method of claim 1, wherein the active power balance control inequality is as follows:
wherein Z is n Representing the fundamental frequency negative sequence impedance; z is Z nQ Representing the theoretical impedance of the reactive power balance control mode; g represents the accuracy tolerance; v (V) + Representing the magnitude of the fundamental frequency positive sequence voltage; v (V) - Representation ofAmplitude of the fundamental frequency negative sequence voltage; p (P) 0 Representing an active power stable value; j represents an imaginary unit; q (Q) 0 Representing a reactive power stable value; a represents a first association constant; b represents a second association constant; c represents a third association constant.
6. The method of claim 1, wherein the acquiring the fundamental negative sequence impedance of the grid-tie inverter comprises:
collecting three-phase grid-connected voltage and three-phase grid-connected current after the grid-connected inverter is subjected to fundamental frequency negative sequence voltage disturbance;
performing information extraction on the three-phase grid-connected voltage by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency negative sequence voltage;
Performing information extraction on the three-phase grid-connected current by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency negative sequence current;
and obtaining the fundamental frequency negative sequence impedance of the grid-connected inverter according to the fundamental frequency negative sequence voltage and the fundamental frequency negative sequence current.
7. The method of claim 1, wherein the fundamental positive sequence impedance comprises an acquisition process of:
when the grid-connected inverter runs in a steady state, collecting steady-state three-phase grid-connected voltage and steady-state three-phase grid-connected current of the grid-connected inverter;
performing information extraction on the steady-state three-phase grid-connected voltage by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency positive sequence voltage;
performing information extraction on the steady-state three-phase grid-connected current by adopting a fast Fourier transform and a symmetrical component method to obtain a corresponding fundamental frequency positive sequence current;
and obtaining the fundamental frequency positive sequence impedance of the grid-connected inverter according to the fundamental frequency positive sequence voltage and the fundamental frequency positive sequence current.
8. A grid-connected inverter control structure identification system, comprising:
negative sequence impedance acquisition module: the method comprises the steps of after a grid-connected inverter is subjected to fundamental frequency negative sequence voltage disturbance, collecting fundamental frequency negative sequence impedance of the grid-connected inverter;
Impedance duty ratio calculation module: the method comprises the steps of calculating a difference value between a fundamental frequency negative sequence impedance and an acquired fundamental frequency positive sequence impedance according to the fundamental frequency negative sequence impedance of the grid-connected inverter, and calculating a ratio of the difference value to the fundamental frequency positive sequence impedance;
and the control structure identification module is used for: the method is used for determining the asymmetric control adoption condition of the grid-connected inverter according to the ratio of the difference value to the fundamental frequency positive sequence impedance;
the control mode judging module: when the grid-connected inverter adopts an asymmetric control structure, judging a control mode adopted in a negative sequence current control link in the asymmetric control structure based on a comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance;
the impedance of the fundamental frequency positive sequence in the impedance duty ratio calculation module is the impedance of the grid-connected inverter in steady-state operation;
the control structure identification module is specifically configured to:
taking the ratio of the difference value to the fundamental frequency positive sequence impedance as the fundamental frequency negative sequence impedance amplitude ratio;
when the amplitude ratio of the fundamental frequency negative sequence impedance is larger than or equal to the negative sequence control sensitivity coefficient or the amplitude ratio of the fundamental frequency negative sequence impedance is smaller than or equal to the separation link sensitivity coefficient, the grid-connected inverter adopts an asymmetric control structure;
When the amplitude ratio of the fundamental frequency negative sequence impedance is larger than the sensitivity coefficient of the separation link and the amplitude ratio of the fundamental frequency negative sequence impedance is smaller than the sensitivity coefficient of the negative sequence control, the grid-connected inverter does not adopt an asymmetric control structure;
the expression corresponding to the fundamental frequency negative sequence impedance amplitude ratio in the control structure identification module is as follows:
wherein R represents the amplitude ratio of the negative sequence impedance of the fundamental frequency; z is Z n Representing the fundamental frequency negative sequence impedance; z is Z p Representing the fundamental frequency positive sequence impedance; a represents a first association constant;
the control mode judging module judges a control mode adopted by a negative sequence current control link in the asymmetric control structure based on a comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance, and comprises the following steps:
when the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the inequality of active power balance control, an active power balance control mode is adopted in a negative sequence current control link in the asymmetric control structure;
when the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the reactive power balance control inequality, a negative sequence current control link in the asymmetric control structure adopts a reactive power balance control mode;
And when the active power balance control inequality and the reactive power balance control inequality are not satisfied between the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance, a negative sequence current control link in the asymmetric control structure adopts a current balance control mode.
9. The system of claim 8, wherein the control mode determining module determines the control mode adopted by the negative sequence current control link in the asymmetric control structure based on a comparison result of the fundamental frequency negative sequence impedance and the theoretical impedance, including:
when the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the inequality of active power balance control, an active power balance control mode is adopted in a negative sequence current control link in the asymmetric control structure;
when the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance meet the reactive power balance control inequality, a negative sequence current control link in the asymmetric control structure adopts a reactive power balance control mode;
and when the active power balance control inequality and the reactive power balance control inequality are not satisfied between the amplitude of the fundamental frequency negative sequence impedance and the amplitude of the theoretical impedance, a negative sequence current control link in the asymmetric control structure adopts a current balance control mode.
10. A computer device, comprising: one or more processors;
a memory for storing one or more programs;
the grid-connected inverter control structure identification method according to any one of claims 1 to 7 is implemented when the one or more programs are executed by the one or more processors.
11. A computer-readable storage medium, on which a computer program is stored, which, when executed, implements the grid-connected inverter control structure identification method according to any one of claims 1 to 7.
CN202311252961.7A 2023-09-26 2023-09-26 Grid-connected inverter control structure identification method, system, equipment and medium Active CN117293901B (en)

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JPH07322505A (en) * 1994-05-24 1995-12-08 Toshiba Corp Control device for system linking inverter
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JPH07322505A (en) * 1994-05-24 1995-12-08 Toshiba Corp Control device for system linking inverter
CN105071405A (en) * 2015-08-26 2015-11-18 电子科技大学 Microgrid system with asymmetric non-linear load and power balancing control method
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