AC / DC impedance modular characterization analysis method of grid-connected system

Abstract

The invention discloses an AC / DC impedance modular characterization analysis method for a grid-connected system, which is used for solving the problem that the stability analysis cannot be met when large-scale new energy is accessed to the network due to the fact that the modular characterization construction of a currently adopted new energy station equivalence method is not comprehensive and systematic. Acquiring a local three-port admittance model of a converter in a to-be-analyzed alternating current subsystem of the grid-connected system; performing rotation correction on the local three-port admittance model to obtain a global three-port admittance model; carrying out relation calculation based on node voltage and node current according to a global three-port admittance model to obtain converter element modular representation; and admittance derivation is carried out on the modular representation of the converter element, and the modular representation of the alternating current element and the modular representation of the direct current element of the alternating current subsystem to be analyzed are obtained. The modular representation of each element is obtained through a derivation mode, and a system-level extension block is formed, thereby facilitating the construction and extension of the network topology of a subsequent grid-connected system, and achieving the stability analysis of large-scale new energy network access.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy grid connection, and particularly to an AC-DC impedance modular characterization analysis method for a grid connection system, an AC-DC impedance modular characterization analysis device for a grid connection system, an electronic device, and a storage medium. Background Art

[0002] With the increasing scarcity of energy resources and the gradual deterioration of the climate environment, renewable energy power generation technologies represented by wind and solar power sources have developed rapidly due to their good economic prospects. However, with the continuous expansion of the scale of new energy power generation, the problem of its grid connection stability has become increasingly prominent, thus posing a huge challenge to the safe and stable operation of the power system.

[0003] Impedance analysis is widely used in the evaluation of new energy grid connection stability because it can compactly characterize the high-order and wide-frequency characteristics of the target system in the form of a transfer function, and has advantages such as strong scalability and easy measurement in circuits. Establishing accurate impedance models for new energy single units, power stations, and clusters is a prerequisite for large-scale new energy access safety and stability analysis.

[0004] Currently, the aggregation impedance modeling is mainly achieved based on dynamic equivalence. Its core lies in dynamically equivalent aggregation of new energy power stations or clusters. After obtaining the single-unit aggregation model, the mainstream impedance analysis and modeling methods can be applied to establish an aggregation impedance model that can characterize the port characteristics of the power station / cluster. Taking a wind farm as an example, with the large-scale and centralized construction of onshore wind farms in China, and the wide application of doubly-fed variable-speed wind turbines and permanent magnet direct-drive full-power units, the research on the equivalent model of variable-speed wind farms has gradually become a hot topic.

[0005] Most of the current new energy power station equivalent methods start from the electrical characteristics of the power station itself and perform equivalent aggregation on the unit parameters within the station. They do not fully consider the impact on the system safety and stability after the access of new energy power stations. At the same time, the topological structure of the new energy power stations used for equivalent research does not conform to the engineering reality. The scale of the equivalent examples is limited to several to more than a dozen wind turbines, which has a large gap from the large-scale wind farm equivalent model required in actual engineering and cannot meet the stability analysis when large-scale new energy is connected to the grid. Summary of the Invention

[0006] The present invention provides an AC-DC impedance modular characterization analysis method for a grid connection system, an AC-DC impedance modular characterization analysis device for a grid connection system, an electronic device, and a storage medium, which are used to solve or partially solve the problem that the modular characterization construction of the current new energy power station equivalent methods is not comprehensive and systematic enough, resulting in the inability to meet the stability analysis when large-scale new energy is connected to the grid.

[0007] The present invention provides a method for modular characterization and analysis of AC-DC impedance of a grid-connected system, where the grid-connected system includes multiple AC subsystems; the method includes:

[0008] Obtain the local three-port admittance model of the converter in the AC subsystem to be analyzed;

[0009] Perform rotation correction on the local three-port admittance model to obtain the global three-port admittance model;

[0010] Calculate based on the relationship between node voltage and node current according to the global three-port admittance model to obtain the modular characterization of the converter components;

[0011] Perform admittance derivation on the modular characterization of the converter components to obtain the modular characterization of the AC components and the modular characterization of the DC components of the AC subsystem to be analyzed.

[0012] Optionally, the performing rotation correction on the local three-port admittance model to obtain the global three-port admittance model includes:

[0013] Obtain the offset phase angle of the converter in the global dq reference frame compared with the reference converter;

[0014] Construct a rotation matrix based on the offset phase angle;

[0015] Correct the AC voltage and AC current of the converter respectively according to the rotation matrix to obtain the corrected voltage and corrected current;

[0016] Substitute the corrected voltage and the corrected current into the local three-port admittance model to obtain the global three-port admittance model of the converter in the global reference frame.

[0017] Optionally, the obtaining the offset phase angle of the converter in the global dq reference frame compared with the reference converter includes:

[0018] Select any converter in the AC subsystem to be analyzed as the reference converter in the global dq reference frame;

[0019] Extract the offset phase angle of the currently analyzed converter relative to the reference converter according to the power flow calculation result.

[0020] Optionally, the calculating based on the relationship between node voltage and node current according to the global three-port admittance model to obtain the modular characterization of the converter components includes:

[0021] Express the AC-DC coupling term represented by the controlled current source in the global three-port admittance model as the mutual inductance between the AC branch and the DC branch;

[0022] Obtain the equivalent circuit of the global three-port admittance model;

[0023] Construct a branch voltage equivalent matrix using the node voltages of the equivalent circuit in the global reference frame, and construct a branch current equivalent matrix using the node currents of the equivalent circuit in the global reference frame;

[0024] Substitute the branch voltage equivalent matrix and the branch current equivalent matrix into the global three-port admittance model to obtain a node voltage-node current relationship matrix;

[0025] Expand the node voltage-node current relationship matrix to obtain a modular representation of the converter components.

[0026] Optionally, the method further includes:

[0027] When the AC side and / or the DC side of the converter is grounded, substitute the grounding boundary conditions into the node voltage-node current relationship matrix for matrix row and column addition and subtraction operations to obtain a simplified modular representation of the converter components.

[0028] Optionally, the deriving the modular representation of the converter components to obtain the modular representation of the AC components and the modular representation of the DC components of the AC subsystem to be analyzed includes:

[0029] Obtain the AC branch admittance of any AC branch and the DC branch admittance of any DC branch in the AC subsystem to be analyzed;

[0030] Derive based on the modular representation of the converter components and in combination with the AC branch admittance to obtain the modular representation of the AC components corresponding to the AC branch;

[0031] Derive based on the modular representation of the converter components and in combination with the DC branch admittance to obtain the modular representation of the DC components corresponding to the DC branch.

[0032] Optionally, the modular representation of the converter components is used to represent a three-port impedance; the modular representation of the AC components is used to represent a two-dimensional impedance; the modular representation of the DC components is used to represent a one-dimensional impedance.

[0033] The present invention also provides an AC-DC impedance modular representation analysis device for a grid-connected system, the grid-connected system includes a plurality of AC subsystems; the device includes:

[0034] An admittance model acquisition module, configured to acquire the local three-port admittance model of the converter in the AC subsystem to be analyzed;

[0035] A rotation correction module, configured to perform rotation correction on the local three-port admittance model to obtain a global three-port admittance model;

[0036] The modular representation first calculation module is used to perform calculations based on the relationship between node voltage and node current according to the global three-port admittance model, and obtain the modular representation of the converter components;

[0037] The modular representation second calculation module is used to perform admittance derivation on the modular representation of the converter components, and obtain the modular representation of the AC components and the modular representation of the DC components of the AC subsystem to be analyzed.

[0038] The present invention also provides an electronic device, which includes a processor and a memory:

[0039] The memory is used to store program codes and transmit the program codes to the processor;

[0040] The processor is used to execute the AC-DC impedance modular representation analysis method of the grid-connected system as described in any one of the above according to the instructions in the program codes.

[0041] The present invention also provides a computer-readable storage medium, which is used to store program codes, and the program codes are used to execute the AC-DC impedance modular representation analysis method of the grid-connected system as described in any one of the above.

[0042] It can be seen from the above technical solutions that the present invention has the following advantages:

[0043] An AC-DC impedance modular representation analysis method for a grid-connected system is provided. First, obtain the local three-port admittance model of the converter in the AC subsystem to be analyzed in the grid-connected system; then perform rotation correction on the local three-port admittance model to obtain the global three-port admittance model; then perform calculations based on the relationship between node voltage and node current according to the global three-port admittance model to obtain the modular representation of the converter components; finally, perform admittance derivation on the modular representation of the converter components to obtain the modular representation of the AC components and the modular representation of the DC components of the AC subsystem to be analyzed. Thus, based on the three-port admittance model of the converter, the modular representations of the converter components, AC components, and DC components are gradually obtained through derivation, forming a system-level expansion block, which is convenient for the subsequent construction and expansion of the grid-connected system network topology and convenient for computer-aided analysis. When the system changes subsequently, only need to superimpose or eliminate the modular representation matrices of the corresponding network components at the nodes where changes occur according to the topology change situation, and then the new system node matrix can be obtained, so that the stability analysis of large-scale new energy grid connection can be realized. Description of the Drawings

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0045] Figure 1 It is a step flowchart of a method for modular characterization and analysis of AC-DC impedance of a grid-connected system;

[0046] Figure 2 It is a schematic diagram of a three-port admittance model of a converter in a local dq coordinate system;

[0047] Figure 3 It is a structural block diagram of a device for modular characterization and analysis of AC-DC impedance of a grid-connected system. Detailed implementation manners

[0048] The embodiments of the present invention provide a method for modular characterization and analysis of AC-DC impedance of a grid-connected system, a device for modular characterization and analysis of AC-DC impedance of a grid-connected system, an electronic device, and a storage medium, which are used to solve or partially solve the problem that the modular characterization construction of the current equivalent method for new energy power stations is not comprehensive and systematic enough to meet the stability analysis requirements when a large amount of new energy is connected to the grid.

[0049] To make the invention purpose, features, and advantages of the present invention more obvious and understandable, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0050] To enable those skilled in the art to better understand the technical solutions provided by the embodiments of the present invention, some technical features involved in the solutions are briefly described first:

[0051] Modular Characterization of Converter Components: The process of decomposing each functional component or subsystem in a converter into independent and interchangeable modules, and performing standardized description and evaluation on these modules.

[0052] As an example, most of the current new energy power station equivalent methods start from the electrical characteristics of the power station itself and perform equivalent aggregation on the unit parameters within the station. They do not fully consider the impact on the system safety and stability after the access of new energy power stations. At the same time, the topological structure of the new energy power station used for equivalent research does not conform to the engineering practice. The scale of the equivalent calculation example is limited to several to more than a dozen wind turbines, which has a large gap with the large-scale wind farm equivalent model required in actual engineering and cannot meet the stability analysis when a large amount of new energy is connected to the grid.

[0053] Therefore, the core inventive point of the embodiments of the present invention is to provide a method for modular characterization and analysis of AC-DC impedance of a grid-connected system. By derivation, modular characterizations of converter components, AC components, and DC components are obtained to form system-level expansion blocks, which facilitate the construction and expansion of the network topology of the subsequent wind-solar power grid-connected system and facilitate computer-aided analysis. When the wind-solar power grid-connected system needs to be expanded or modified, only according to the change situation of the system network topology, the modular characterization matrices of the corresponding network components are superimposed or eliminated at the changed nodes, and the system node matrix under the new system and new network topology can be obtained. Thus, based on the original system model, the system node matrix of the new system can be calculated without reconstruction, and the stability analysis of large-scale new energy access can be realized.

[0054] Refer to Figure 1 , which shows a flowchart of the steps of a method for modular characterization and analysis of AC-DC impedance of a grid-connected system provided by an embodiment of the present invention, and specifically may include the following steps:

[0055] Step 101, obtain the local three-port admittance model of the converter in the AC subsystem to be analyzed;

[0056] The grid-connected system proposed in the embodiments of the present invention is a wind-solar power grid-connected system, which may include multiple AC subsystems or multiple DC subsystems. Taking a certain AC subsystem as an example (i.e., the AC subsystem to be analyzed). Figure 2 shows a schematic diagram of the three-port admittance model of the converter in the local dq coordinate system. Since Figure 2 the three-port admittance model of the converter shown is established based on the local dq coordinate system, it needs to be rotated to the global reference system for subsequent analysis processes.

[0057] Step 102, perform rotation correction on the local three-port admittance model to obtain the global three-port admittance model;

[0058] In some embodiments, the implementation process of performing rotation correction on the local three-port admittance model to obtain the global three-port admittance model may include the following sub-steps S01 to S04:

[0059] Step S01: Obtain the offset phase angle of the converter in the global dq reference frame compared with the reference converter;

[0060] Select any converter in the AC subsystem to be analyzed as the global dq reference frame (i.e., as the reference converter), and extract the offset phase angle of the currently analyzed converter relative to this reference converter according to the power flow calculation results.

[0061] Step S02: Construct a rotation matrix based on the offset phase angle;

[0062] According to the offset phase angle, the rotation matrix of the current converter can be constructed. For example, if the offset phase angle of the current converter relative to the reference converter is , then the rotation matrix can be constructed as follows:

[0063] (1)

[0064] Step S03: Correct the AC voltage and AC current of the converter respectively according to the rotation matrix to obtain the corrected voltage and corrected current;

[0065] Based on the rotation matrix shown in Equation (1), the AC voltage and current of the converter can be corrected in the following way:

[0066] (2)

[0067] In the formula, the superscript represents the variable in the global dq coordinate system; represents the AC current before correction; represents the AC current after correction (corrected current); represents the AC voltage before correction; represents the AC voltage after correction (corrected voltage).

[0068] Step S04: Substitute the corrected voltage and corrected current into the local three-port admittance model to obtain the global three-port admittance model of the converter in the global reference frame.

[0069] Substitute the corrected AC voltage and AC current into the three-port admittance model of the converter in the local dq reference frame to obtain the three-port admittance model of the converter in the global reference frame:

[0070] (3)

[0071] Among them, , respectively represent the DC current and DC voltage of the converter ; , All are converters The AC-DC coupling term characterized by the controlled current source; Denote the converter The admittance of the DC side; Denote the converter The admittance of the AC side term.

[0072] It can be seen from the above formula that the impedance terms related to the AC dynamics in the converter need to be rotated, while the DC terms do not need to be rotated. This is because the power balance eliminates the influence of the AC side phase angle offset on the DC side.

[0073] Step 103: Calculate based on the relationship between the node voltage and the node current according to the global three-port admittance model to obtain the modular representation of the converter components;

[0074] In some embodiments, the implementation process of calculating based on the relationship between the node voltage and the node current according to the global three-port admittance model to obtain the modular representation of the converter components may include the following sub-steps S11 to S15:

[0075] Step S11: Represent the AC-DC coupling term characterized by the controlled current source in the global three-port admittance model as the mutual inductance between the AC branch and the DC branch;

[0076] Analogous to the passive mutual inductance element, the AC-DC coupling term characterized by the controlled current source (i.e., ) and (i.e., ) are represented as the mutual inductance between the AC branch and the DC branch.

[0077] Step S12: Obtain the equivalent circuit of the global three-port admittance model;

[0078] Step S13: Construct the branch voltage equivalent matrix using the node voltages of the equivalent circuit in the global reference frame, and construct the branch current equivalent matrix using the node currents of the equivalent circuit in the global reference frame;

[0079] Based on the equivalent circuit of the three-port admittance model of the converter in the global reference frame, using its node voltages , , , to represent the branch voltages , , the branch voltage equivalent matrix can be constructed as shown below:

[0080] (4)

[0081] In the formula, is the second-order identity matrix; is the AC-DC incidence matrix, i.e., the branch-node incidence matrix.

[0082] Using the node currents in the global reference frame 、 、 、 to represent the branch currents 、 , the equivalent matrix of branch currents can be constructed as follows:

[0083] (5)

[0084] Step S14: Substitute the equivalent matrix of branch voltages and the equivalent matrix of branch currents into the global three-port admittance model to obtain the node voltage-node current relationship matrix;

[0085] Substituting the equivalent matrix of branch voltages in Equation (4) and the equivalent matrix of branch currents in Equation (5) into the converter three-port admittance model in the global reference frame in Equation (3), the relationship between the node voltage and the node current can be obtained, which is defined as the node voltage-node current relationship matrix:

[0086] (6)

[0087] Step S15: Expand the node voltage-node current relationship matrix to obtain the modular representation of the converter components.

[0088] Expanding Equation (6), the modular representation of the converter components can be obtained as shown in Equation (7) below:

[0089] (7)

[0090] In the formula, is used for branch-node expansion of the AC terms and the coupling terms; is used for branch-node expansion of the DC terms; 、 、 、 are all nodes; is the DC-side admittance; is the AC-port admittance after rotation in the global-local reference frame; is the DC-side to AC-side coupling admittance element after rotation in the global-local reference frame; is the AC-side to DC-side coupling admittance element after rotation in the global-local reference frame.

[0091] In some possible situations, the AC and DC sides of the converter may be grounded (reference nodes). When the AC side and / or the DC side of the converter is grounded, substituting the grounding boundary conditions into the node voltage-node current relationship matrix of Equation (6) for matrix row and column addition and subtraction operations can obtain a simplified modular representation of the converter components to simplify the modular representation of the converter components in Equation (7). Specifically, the grounding of the AC and DC sides mainly includes the following three situations:

[0092] Situation 1: The DC side of the converter component is not grounded, and the AC side is grounded.

[0093] For example Figure 2 the node in is grounded, and its grounding boundary conditions are: , . Substituting this grounding boundary condition into Equation (6) and performing matrix row and column addition and subtraction operations, the following Equation (8) can be obtained:

[0094] (8)

[0095] Situation 2: The DC side of the converter component is grounded, and the AC side is not grounded.

[0096] For example Figure 2 the node in is grounded, and its grounding boundary conditions are: , . Substituting this grounding boundary condition into Equation (6) and performing matrix row and column addition and subtraction operations, the following Equation (9) can be obtained:

[0097] (9)

[0098] Situation 3: Both the DC side and the AC side of the converter component are grounded.

[0099] For example Figure 2 the nodes in , are grounded, and its grounding boundary conditions are: , , , . Substituting this grounding boundary condition into Equation (6) and performing matrix row and column addition and subtraction operations, the following Equation (10) can be obtained:

[0100] (10)

[0101] Step 104: Perform admittance derivation on the modular representation of the converter components to obtain the modular representation of the AC components and the modular representation of the DC components of the AC subsystem to be analyzed.

[0102] This step mainly derives the modular representations of AC components and DC components based on the modular representation of converter components.

[0103] In some embodiments, the implementation process of obtaining the modular representations of AC components and DC components of the AC subsystem to be analyzed by performing admittance derivation on the modular representation of converter components may include the following sub-steps S21 to S23:

[0104] Step S21: Obtain the AC branch admittance of any AC branch and the DC branch admittance of any DC branch in the AC subsystem to be analyzed;

[0105] Step S22: Derive based on the modular representation of converter components and in combination with the AC branch admittance to obtain the modular representation of the AC component corresponding to the AC branch;

[0106] Let the admittance magnitude of the AC branch be . According to Equation (7), the modular representation of the AC component can be derived as:

[0107] (11)

[0108] Step S23: Derive based on the modular representation of converter components and in combination with the DC branch admittance to obtain the modular representation of the DC component corresponding to the DC branch.

[0109] Let the admittance magnitude of the DC branch be . According to Equation (7), the modular representation of the DC component can be derived as:

[0110] (12)

[0111] Wherein, , are the endpoints of the AC branch ; , are the endpoints of the DC branch .

[0112] According to the above method, the modular representations of each converter component, AC component, and DC component in the wind-solar power grid-connected system can be obtained respectively. The modular representation of the converter component is used to represent the three-port impedance. The modular representation of the AC component is used to represent the two-dimensional impedance. The modular representation of the DC component is used to represent the one-dimensional impedance.

[0113] The above-mentioned modular representations of the converter component, AC component, and DC component can be used for the network topology construction of the wind-solar power grid-connected system to accurately analyze the stability of large-scale new energy grid connection.

[0114] In an embodiment of the present invention, a method for modular characterization analysis of AC-DC impedance of a grid-connected system is provided. By derivation, the modular characterizations of converter components, AC components, and DC components are obtained, forming a system-level expansion block, which is convenient for the construction and expansion of the network topology of a wind-solar power grid-connected system and for computer-aided analysis. When the wind-solar power grid-connected system needs to be expanded or modified, only according to the change of the system network topology, the modular characterization matrix of the corresponding network components is superimposed or eliminated at the changed nodes, and the system node matrix under the new network topology of the new system can be obtained. Thus, the system node matrix of the new system can be calculated without reconstructing the original model, without having to reconstruct the system model, and the stability analysis of large-scale new energy grid connection can be realized.

[0115] Referring to Figure 3 , a structural block diagram of an apparatus for modular characterization analysis of AC-DC impedance of a grid-connected system provided by an embodiment of the present invention is shown. The grid-connected system includes a plurality of AC subsystems; the apparatus may specifically include:

[0116] An admittance model acquisition module 301, configured to acquire a local three-port admittance model of a converter in an AC subsystem to be analyzed;

[0117] A rotation correction module 302, configured to perform rotation correction on the local three-port admittance model to obtain a global three-port admittance model;

[0118] A modular characterization first calculation module 303, configured to perform a calculation based on the relationship between node voltage and node current according to the global three-port admittance model to obtain a modular characterization of a converter component;

[0119] A modular characterization second calculation module 304, configured to perform admittance derivation on the modular characterization of the converter component to obtain a modular characterization of an AC component and a modular characterization of a DC component of the AC subsystem to be analyzed.

[0120] In an optional embodiment, the rotation correction module 302 includes:

[0121] An offset phase angle acquisition module, configured to acquire an offset phase angle of the converter in a global dq reference system compared with a reference converter;

[0122] A rotation matrix construction module, configured to construct a rotation matrix based on the offset phase angle;

[0123] A current and voltage correction module, configured to respectively correct the AC voltage and AC current of the converter according to the rotation matrix to obtain a corrected voltage and a corrected current;

[0124] A global three-port admittance model obtaining module, which is configured to substitute the corrected voltage and the corrected current into the local three-port admittance model to obtain the global three-port admittance model of the converter in the global reference frame.

[0125] In an alternative embodiment, the offset phase angle obtaining module is specifically configured to:

[0126] Select any one converter in the AC subsystem to be analyzed as the reference converter in the global dq reference frame;

[0127] Extract the offset phase angle of the currently analyzed converter relative to the reference converter according to the power flow calculation result.

[0128] In an alternative embodiment, the modular characterization first calculation module 303 includes:

[0129] A mutual inductance representation module, which is configured to represent the AC-DC coupling term characterized by the controlled current source in the global three-port admittance model as the mutual inductance between the AC branch and the DC branch;

[0130] An equivalent circuit obtaining module, which is configured to obtain the equivalent circuit of the global three-port admittance model;

[0131] An equivalent matrix construction module, which is configured to construct a branch voltage equivalent matrix using the node voltages in the global reference frame of the equivalent circuit and construct a branch current equivalent matrix using the node currents in the global reference frame of the equivalent circuit;

[0132] A relationship matrix obtaining module, which is configured to substitute the branch voltage equivalent matrix and the branch current equivalent matrix into the global three-port admittance model to obtain a node voltage-node current relationship matrix;

[0133] A relationship matrix expansion module, which is configured to expand the node voltage-node current relationship matrix to obtain a modular characterization of the converter components.

[0134] In an alternative embodiment, the device further includes:

[0135] A modular characterization simplification module, which is configured to substitute the grounding boundary condition into the node voltage-node current relationship matrix for matrix row and column addition and subtraction operations when the AC side and / or the DC side of the converter is grounded, so as to obtain a simplified modular characterization of the converter components.

[0136] In an alternative embodiment, the modular characterization second calculation module 304 includes:

[0137] A branch admittance obtaining module, which is configured to obtain the AC branch admittance of any AC branch and the DC branch admittance of any DC branch in the AC subsystem to be analyzed;

[0138] An AC branch admittance derivation module, configured to perform derivation based on the modular characterization of the converter components and in combination with the AC branch admittance, so as to obtain the modular characterization of the AC components corresponding to the AC branch;

[0139] A DC branch admittance derivation module, configured to perform derivation based on the modular characterization of the converter components and in combination with the DC branch admittance, so as to obtain the modular characterization of the DC components corresponding to the DC branch.

[0140] In an alternative embodiment, the modular characterization of the converter components is used to characterize a three-port impedance; the modular characterization of the AC components is used to characterize a two-dimensional impedance; and the modular characterization of the DC components is used to characterize a one-dimensional impedance.

[0141] For the apparatus embodiment, since it is basically similar to the method embodiment, the description is relatively simple. For related parts, reference may be made to the partial description of the foregoing method embodiment.

[0142] It should be noted that, to enable those skilled in the art to better distinguish data of the same type but with different actual pointing meanings, in the embodiments of the present invention, some technical features are distinguished and described using first and second. First and second are only used for data distinction and have no other special meanings. It can be understood that the present invention places no restrictions thereon.

[0143] The embodiments of the present invention further provide an electronic device, which includes a processor and a memory:

[0144] The memory is used to store program code and transmit the program code to the processor;

[0145] The processor is configured to execute the AC-DC impedance modular characterization analysis method of the grid-connected system according to any embodiment of the present invention based on the instructions in the program code.

[0146] The embodiments of the present invention further provide a computer-readable storage medium, which is used to store program code, and the program code is used to execute the AC-DC impedance modular characterization analysis method of the grid-connected system according to any embodiment of the present invention.

[0147] Those skilled in the art can clearly understand that for the sake of convenience and brevity of description, the specific working processes of the above-described system, apparatus, and unit can refer to the corresponding processes in the foregoing method embodiments, and will not be described herein again.

[0148] In several embodiments provided by the present invention, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there can be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections between each other can be through some interfaces, and the indirect couplings or communication connections of devices or units can be in electrical, mechanical, or other forms.

[0149] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0150] In addition, in each embodiment of the present invention, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

[0151] If the above-mentioned integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present invention. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical discs that can store program codes.

[0152] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of the present invention.

Claims

1. A modular characterization and analysis method for AC and DC impedance of a grid-connected system, characterized in that: The grid-connected system includes a plurality of AC subsystems; the method includes: Obtain a local three-port admittance model of a converter in the AC subsystem to be analyzed; Performing rotation correction on the local three-port admittance model to obtain a global three-port admittance model; Perform calculation based on the relationship between node voltage and node current according to the global three-port admittance model to obtain a modular representation of the converter element; Admittance derivation is performed on the modular representation of the converter element to obtain the modular representation of the AC element and the modular representation of the DC element of the AC subsystem to be analyzed.

2. The AC / DC impedance modular characterization and analysis method according to claim 1, characterized in that: The step of performing rotation correction on the local three-port admittance model to obtain a global three-port admittance model includes: Obtaining an offset phase angle of the converter compared to a reference converter in a global dq reference system; constructing a rotation matrix based on the offset phase angle; Correcting the AC voltage and the AC current of the converter according to the rotation matrix to obtain a corrected voltage and a corrected current; Substituting the corrected voltage and the corrected current into the local three-port admittance model, a global three-port admittance model of the converter in a global reference system is obtained.

3. The AC / DC impedance modular characterization and analysis method according to claim 2, characterized in that: The obtaining of the offset phase angle of the converter compared to the reference converter in the global dq reference system includes: Selecting any converter in the AC subsystem to be analyzed as a reference converter in a global dq reference system; The offset phase angle of the converter currently being analyzed relative to the reference converter is extracted according to the power flow calculation result.

4. The AC / DC impedance modular characterization and analysis method according to claim 1, characterized in that: The step of performing calculation based on the relationship between node voltage and node current according to the global three-port admittance model to obtain a modular representation of converter components includes: The AC / DC coupling term represented by the controlled current source in the global three-port admittance model is expressed as the mutual inductance between the AC branch and the DC branch; Obtaining an equivalent circuit of the global three-port admittance model; A branch voltage equivalent matrix is ​​constructed by using the node voltages of the equivalent circuit in a global reference system, and a branch current equivalent matrix is ​​constructed by using the node currents of the equivalent circuit in a global reference system; Substituting the branch voltage equivalent matrix and the branch current equivalent matrix into the global three-port admittance model to obtain a node voltage-node current relationship matrix; The node voltage-node current relationship matrix is ​​expanded to obtain a modular representation of converter components.

5. The AC / DC impedance modular characterization and analysis method according to claim 4, characterized in that: Also includes: When the AC side and / or the DC side of the converter is grounded, the grounding boundary condition is substituted into the node voltage-node current relationship matrix to perform matrix row and column addition and subtraction operations to obtain a simplified modular representation of the converter elements.

6. The AC / DC impedance modular characterization and analysis method according to claim 1, characterized in that: The step of performing admittance derivation on the modular representation of the converter element to obtain the modular representation of the AC element and the modular representation of the DC element of the AC subsystem to be analyzed includes: Obtaining the AC branch admittance of any AC branch and the DC branch admittance of any DC branch in the AC subsystem to be analyzed; Derivation is performed based on the modular representation of the converter element and in combination with the admittance of the AC branch to obtain a modular representation of the AC element corresponding to the AC branch; According to the modular representation of the converter element, in combination with the DC branch admittance, deduction is performed to obtain a modular representation of the DC element corresponding to the DC branch.

7. The AC / DC impedance modular characterization and analysis method according to claim 6, characterized in that: The modular representation of the converter element is used to represent the three-port impedance; the modular representation of the AC element is used to represent the two-dimensional impedance; and the modular representation of the DC element is used to represent the one-dimensional impedance.

8. A modular characterization and analysis device for AC and DC impedance of a grid-connected system, characterized in that: The grid-connected system includes a plurality of AC subsystems; the device includes: An admittance model acquisition module, used to acquire a local three-port admittance model of a converter in an AC subsystem to be analyzed; A rotation correction module, used for performing rotation correction on the local three-port admittance model to obtain a global three-port admittance model; A modular characterization first calculation module is used to perform calculations based on the relationship between node voltage and node current according to the global three-port admittance model to obtain a modular characterization of the converter element; The second calculation module of modular characterization is used to perform admittance derivation on the modular characterization of the converter element to obtain the modular characterization of the AC element and the modular characterization of the DC element of the AC subsystem to be analyzed.

9. An electronic device, characterized in that: The device comprises a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the AC and DC impedance modular characterization and analysis method of the grid-connected system according to any one of claims 1 to 7 according to the instructions in the program code.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store program codes, and the program codes are used to execute the AC and DC impedance modular characterization and analysis method of the grid-connected system according to any one of claims 1 to 7.

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