CN115700956A - Photovoltaic cluster direct current outgoing oscillation analysis method and system based on multiport matrix - Google Patents
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Abstract
The invention belongs to the field of broadband oscillation analysis of a power system, and provides a photovoltaic cluster direct current outgoing oscillation analysis method and system based on a multi-port matrix, which comprises the steps of constructing an equivalent multi-input multi-output port network based on a topological structure of a photovoltaic cluster direct current outgoing system, and classifying nodes and branches respectively according to types; forming a block node admittance matrix according to the node classification result and the branch classification result, and constructing a node voltage equation in the form of a block matrix; selecting photovoltaic and direct current access nodes as research nodes, and constructing a photovoltaic cluster direct current outgoing system closed-loop transfer matrix containing a comparison matrix between node current and voltage; and judging the oscillation stability of the system by utilizing the characteristic track of the closed-loop transfer return ratio matrix according to the generalized Nyquist criterion. The impedance analysis method is expanded to the stability analysis of a multi-input multi-output system, all poles of the system are comprehensively considered, the phenomenon that the traditional equivalent is simplified into the pole hiding in the single-input single-output process is avoided, and the oscillation stability of the system is reflected.
Description
Technical Field
The invention belongs to the technical field of broadband oscillation analysis of power systems, and particularly relates to a photovoltaic cluster direct current outgoing oscillation analysis method and system based on a multiport matrix.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
Photovoltaic is connected to a power grid by means of a power electronic inverter, direct current transmission is based on a power electronic conversion technology, and past engineering and research experiences show that the risk of wide-frequency-domain oscillation exists among multiple power electronic devices, so that the safe operation of a novel power system is challenged.
The characteristic value analysis based on the state space model is used as a classical research tool of a small-interference dynamic process, can provide all mode information of the dynamic process, and can be used as a verification means of off-line analysis. Then, with the large-scale power electronics of the power system, it is inconvenient to use the eigenvalue analysis for the wide-band oscillation analysis. The broadband oscillation only needs to analyze a mode with zero or very small damping ratio, and the impedance analysis method only establishes an input or output impedance model of a research object, analyzes the system oscillation frequency according to the relation between impedances, and completely meets the analysis requirement of the broadband oscillation, so the method is widely applied to power electronic equipment systems in recent years. However, the conventional impedance analysis method is proposed based on a single-input single-output system, and the applicability of the impedance analysis method for a multi-input multi-output system is obviously limited.
There are studies to equivalently convert a multi-input multi-output system into a single-input single-output system and then apply a traditional impedance analysis method, but some oscillation modes may be lost in the conversion process by the method, and an analysis conclusion inconsistent with the reality is generated.
Disclosure of Invention
In order to solve the problems, the invention provides a photovoltaic cluster direct current outgoing oscillation analysis method and a photovoltaic cluster direct current outgoing oscillation analysis system based on a multiport matrix, and aims at solving the problems that when the traditional impedance analysis method is applied to a multi-input multi-output system, the method based on an equivalent single-input single-output source-load subsystem has harsh assumed conditions, no unstable poles and the like. The method utilizes a system block node voltage equation to construct a closed-loop representation form which can contain all unstable poles, and judges the stability of the system according to the characteristic track of a closed-loop transfer function comparison matrix. The method improves the applicability of the impedance analysis method while ensuring the accuracy of stability analysis.
According to some embodiments, a first aspect of the present invention provides a photovoltaic cluster direct current outgoing oscillation analysis method based on a multi-port matrix, which adopts the following technical solutions:
a photovoltaic cluster direct current outgoing oscillation analysis method based on a multi-port matrix comprises the following steps:
constructing an equivalent multi-input multi-output port network based on a topological structure of a photovoltaic cluster direct-current delivery system, and classifying nodes and branches respectively according to types;
forming a block node admittance matrix according to the node classification result and the branch classification result, and constructing a node voltage equation in the form of a block matrix;
selecting photovoltaic and direct current access nodes as research nodes, and constructing a photovoltaic cluster direct current outgoing system closed loop transfer function matrix containing a comparison matrix between node current and voltage;
and judging the oscillation stability of the system by utilizing the characteristic locus of a return ratio matrix of the closed-loop transfer function matrix according to the generalized Nyquist criterion.
Further, the photovoltaic cluster direct current delivery system-based topology structure constructs an equivalent multi-input multi-output port network, and classifies nodes and branches according to types, specifically:
the method comprises the steps of dividing nodes in the multiport network into photovoltaic or direct current access nodes and other nodes, and dividing branches into grounding branches and node connection branches.
Further, the forming a block node admittance matrix according to the node classification result and the branch classification result, and constructing a node voltage equation in a block matrix form includes:
converting the branch admittance matrix into a form of a block matrix according to branch classification results to obtain a block branch admittance matrix;
converting the incidence matrix into a form of a block matrix according to the node classification result and the branch classification result to obtain a block incidence matrix;
determining a block node admittance matrix based on the block branch admittance matrix and the block incidence matrix;
and constructing a node voltage equation in the form of a block matrix by using the determined block node admittance matrix.
Further, the node voltage equation in the form of the blocking matrix is
In the formula of U A And I A Voltage and injection current, U, of photovoltaic or DC access nodes, respectively L And I L Voltages and injection currents, Y, of the remaining nodes, respectively 11 And Y 22 Self-admittance, Y, of the remaining nodes and of the photovoltaic or DC access node, respectively 12 And Y 21 Respectively the mutual admittance of the other nodes and the photovoltaic or direct current access node.
Further, the photovoltaic cluster direct current outgoing system closed-loop transfer function matrix including the comparison matrix between the node current and the node voltage specifically includes:
wherein E is an identity matrix and Y is d11 Is a diagonal array of ground branch admittances; y is d22 Is a diagonal array of series branch admittances;
an impedance matrix for an ac system;
is the admittance matrix of photovoltaic and DC systems.
Further, the closed loop transfer contrast matrix specifically includes:
L(s)＝Z L Y A
wherein,
an impedance matrix for an ac system;
is the admittance matrix of photovoltaic and DC systems.
Further, the method for judging the system oscillation stability by using the characteristic track of the closed loop transfer return ratio matrix according to the generalized nyquist criterion specifically comprises the following steps:
according to the generalized Nyquist criterion, when the number of net turns of the characteristic track around the critical point (-1, j 0) in the anticlockwise direction is equal to the number of poles of the right half-plane of the contrast matrix L(s), the system is stable; conversely, the system is unstable.
According to some embodiments, a second aspect of the present invention provides a photovoltaic cluster direct current outgoing oscillation analysis system based on a multi-port matrix, which adopts the following technical solutions:
photovoltaic cluster direct current outgoing oscillation analysis system based on multiport matrix includes:
the node branch classification module is used for constructing an equivalent multi-input multi-output port network based on a topological structure of the photovoltaic cluster direct-current delivery system, and classifying the nodes and the branches respectively according to types;
the block node voltage equation building module is used for forming a block node admittance matrix according to the node classification result and the branch classification result and building a node voltage equation in the form of a block matrix;
the closed-loop transfer function matrix construction module is configured to select photovoltaic and direct-current access nodes as research nodes and construct a photovoltaic cluster direct-current delivery system closed-loop transfer function matrix containing a return matrix between the current and the voltage of the nodes;
and the system oscillation analysis module is used for judging the system oscillation stability by utilizing the characteristic track of the return ratio matrix of the closed-loop transfer function matrix according to the generalized Nyquist criterion.
According to some embodiments, a third aspect of the invention provides a computer-readable storage medium.
A computer-readable storage medium, on which a computer program is stored, which program, when being executed by a processor, carries out the steps of the method for dc-fed oscillation analysis of a photovoltaic cluster based on a multiport matrix as described above in relation to the first aspect.
According to some embodiments, a fourth aspect of the invention provides a computer apparatus.
A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the steps in the multiport matrix based photovoltaic cluster dc outgoing oscillation analysis method as described in the first aspect above when executing the program.
Compared with the prior art, the invention has the beneficial effects that:
1. the impedance analysis method is expanded from a single-input single-output system to a multi-input multi-output system in a matrix form, and the defect that a multi-port system is equivalent and simplified into a hidden mode in the case of a single-input single-output system is overcome. The assumed conditions are stable only when the subsystems run independently, and compared with an impedance analysis method based on a source-load subsystem, the assumed conditions are weaker and reasonable, and the method is wider in application range.
2. The closed-loop transfer function matrix of the multi-input multi-output system is constructed by utilizing the voltage matrix of the system block nodes, all poles of the multi-input multi-output system can be correctly reflected, and the condition that the unstable poles of the system are not obvious due to zero-pole cancellation is avoided. The method can accurately reflect the system stability even if an unstable pole exists in the 'source-load' subsystem.
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The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are included to illustrate an exemplary embodiment of the invention and not to limit the invention.
FIG. 1 is a flow chart of a photovoltaic cluster direct current outgoing oscillation analysis method based on a multiport impedance matrix in an embodiment of the invention;
FIG. 2 is a schematic diagram of a simulation model structure of a multi-grid-connected photovoltaic system via a DC delivery system according to an embodiment of the present invention;
FIG. 3 is a Bus5 voltage response curve in an embodiment of the present invention;
FIG. 4 is a fast Fourier transform analysis result of Bus5 Bus voltage in the embodiment of the present invention;
FIG. 5 illustrates the active power output by the PV2 system according to an embodiment of the present invention;
FIG. 6 is an equivalent circuit diagram of a multi-grid photovoltaic system through DC delivery in the embodiment of the present invention;
FIG. 7 is a diagram illustrating the analysis results of a conventional impedance analysis method based on a "source-load" system according to an embodiment of the present invention;
FIG. 8 is a characteristic trace of a contrast matrix in an embodiment of the present invention.
Detailed Description
The invention is further described with reference to the following figures and examples.
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The embodiments and features of the embodiments of the invention may be combined with each other without conflict.
Example one
The embodiment provides a photovoltaic cluster direct current outgoing oscillation analysis method based on a multi-port matrix, and the embodiment is exemplified by applying the method to a server. The server may be an independent physical server, a server cluster or a distributed system formed by a plurality of physical servers, or a cloud server providing basic cloud computing services such as a cloud service, a cloud database, cloud computing, a cloud function, cloud storage, a network server, cloud communication, middleware service, a domain name service, a security service CDN, a big data and artificial intelligence platform, and the like. The terminal may be, but is not limited to, a smart phone, a tablet computer, a laptop computer, a desktop computer, a smart speaker, a smart watch, and the like. The terminal and the server may be directly or indirectly connected through wired or wireless communication, and the application is not limited herein. In this embodiment, the method includes the steps of:
constructing an equivalent multi-input multi-output port network based on a topological structure of a photovoltaic cluster direct-current delivery system, and classifying nodes and branches respectively according to types;
forming a block node admittance matrix according to the node classification result and the branch classification result, and constructing a node voltage equation in the form of a block matrix;
selecting photovoltaic and direct current access nodes as research nodes, and constructing a photovoltaic cluster direct current outgoing system closed loop transfer function matrix containing a comparison matrix between node current and voltage;
and judging the oscillation stability of the system by utilizing the characteristic locus of a return ratio matrix of the closed-loop transfer function matrix according to the generalized Nyquist criterion.
Specifically, as shown in fig. 1, the present embodiment provides a photovoltaic cluster direct-current outgoing oscillation analysis method based on a multi-port impedance matrix, which specifically includes:
1. based on the topological structure of the photovoltaic cluster direct current delivery system, an equivalent multi-input multi-output port network is constructed, and nodes and branches are classified according to types
Dividing the photovoltaic grid connection into photovoltaic/direct current access nodes and other nodes through nodes in a direct current delivery system; the branches are divided into a grounding branch and a series branch.
2. Forming a block node admittance matrix according to the node and branch classification results, and constructing a node voltage equation in the form of a block matrix
Depending on the classification of the branches, the branch admittance matrix may be represented in the form of a block matrix:
in the formula: y is d Is a branch admittance matrix, Y d11 Is an admittance diagonal array formed by grounding branches; y is d22 Is an admittance diagonal array formed by node connecting branches.
Also according to the classification of branches and nodes, the correlation matrix can also be expressed in the form of a block matrix:
in the formula: a is the correlation matrix, A 21 Is an incidence matrix between a direct current or photovoltaic access node and a grounding branch; a. The 22 And the incidence matrix is arranged between the direct current or photovoltaic access node and the node connecting branch. A. The 11 Is the incidence matrix between the rest nodes and the grounding branch; a. The 12 Is the incidence matrix between the rest nodes and the node connecting branches.
According to the branch admittance matrix and the incidence matrix, the node admittance matrix Y in the form of the blocking matrix can be expressed as:
the node voltage equation in the form of a block matrix is
In the formula of U A And I A Voltage and injection current, U, of photovoltaic or DC access nodes, respectively L And I L Voltages and injection currents, Y, of the remaining nodes, respectively 11 And Y 22 Self-admittance, Y, of the remaining nodes and of the photovoltaic or DC access node, respectively 12 And Y 21 Respectively the mutual admittance of the other nodes and the photovoltaic or direct current access node.
3. Photovoltaic and direct current access nodes are selected as research nodes, a photovoltaic cluster direct current delivery system closed loop transfer function matrix containing a comparison matrix between node current and node voltage is constructed
Subsynchronous oscillation of the new energy grid-connected system is caused by a power electronic converter, so that photovoltaic and direct-current access nodes are selected as research nodes, and a photovoltaic cluster direct-current outgoing system closed-loop transfer function matrix containing a return ratio matrix between current and voltage of the nodes is constructed.
Wherein E is an identity matrix and Y is d11 Is a diagonal array of ground branch admittances; y is d22 Is a diagonal array of series branch admittances;
an impedance matrix for an ac system;
is the admittance matrix of the photovoltaic and direct current system.
According to the definition of the contrast matrix, the contrast matrix of the closed-loop transfer function matrix of the system is as follows:
L(s)＝Z L Y A (6)
4. judging the system oscillation stability by utilizing the characteristic track of a closed loop transfer return ratio matrix according to a generalized Nyquist criterion
According to the generalized Nyquist criterion, the system is stable when the net number of turns of the feature trajectory around the critical point (-1, j 0) counterclockwise is equal to the number of poles of the right half-plane of the contrast matrix L(s).
In the contrast matrix of the closed-loop system, the impedance matrix Z of the AC system L Is formed by the impedance of the system and has no right half-plane pole. Photovoltaic and DC systems assuming each subsystem is stable when operating independentlyAdmittance matrix Y A There is also no right half-plane pole. Therefore, the requirements for the system to be stable are: the characteristic locus of the contrast matrix L(s) does not enclose the critical point (-1, j 0).
It should be noted that, in the method, it is assumed that each subsystem operates stably independently, which means that each photovoltaic, dc, or ac system in the system operates stably independently, and is not an equivalent power subsystem or load subsystem.
5. Example analysis
Based on an IEEE 9 node standard calculation example and a CIGRE standard direct current test system, a simulation scene of multi-photovoltaic grid connection and direct current transmission is established in PSCAD. Firstly, a coherent unit of each generator node synchronous generator in the IEEE 9 node standard calculation example is set to be 4, and the load level of the system is adjusted to enable the capacity of the system to be matched with the transmission capacity of the CIGRE direct current standard system. The rectification side of the CIGRE direct-current standard system is connected with a Bus8, the parallel reactive power compensation device on the rectification side is increased to 37.342uF, the alternating-current system on the inversion side is replaced by an ideal power supply, and the filtering and reactive power compensation device on the inversion side is disconnected. The two-stage photovoltaic systems PV1 and PV2 are respectively connected to the grid at Bus5 and Bus8, and the parameters are shown in table 1.
TABLE 1 two-stage photovoltaic systems PV1 and PV2 parameters
At 25s, the proportional coefficient of the inner loop current control PI link of the photovoltaic system PV2 is reduced from 0.2 to 0.02, and the integral coefficient is increased from 20 to 53.
As shown in fig. 3, as a simulation result of the multi-photovoltaic grid-connected dc delivery system, it can be seen from the voltage waveform of the Bus5 that the multi-photovoltaic grid-connected dc delivery system maintains a stable operation state before 25s, and after the disturbance occurs, the Bus voltage of the Bus5 oscillates, and the system cannot maintain the stable operation state. As shown in the result of the Bus5 Bus voltage fast Fourier transform analysis shown in FIG. 4, the Bus5 voltage after 25s contains not only a 50Hz power frequency component but also a 61Hz oscillation frequency component. As shown in fig. 5, after the parameters of the 25s photovoltaic system PV2 are changed, the active power output by the photovoltaic system PV2 oscillates in constant amplitude.
Next, stability analysis is performed on the multi-photovoltaic grid-connected direct-current outgoing system by a traditional impedance analysis method based on a 'source-load' system. First, the multi-photovoltaic grid connection shown in fig. 2 is equivalent to a single-input single-output system composed of a power supply subsystem and a load subsystem via a dc delivery system, as shown in fig. 6. According to the power flow direction of the system, the direct current system in the virtual frame is equivalent to a load subsystem, and the part outside the virtual frame is equivalent to a power subsystem. The input/output impedance of the power subsystem and the load subsystem is calculated by methods of series connection, parallel connection and the like. In the figure, I Pi 、Z Pi (i =1, 2) is the current source current and the parallel impedance of the norton equivalent model of the photovoltaic systems PV1 and PV 2; i is D 、Z D The current source current and the parallel impedance of a direct current system Noton equivalent model; z is a linear or branched member F Equivalent impedance of a filtering device and a reactive power compensation device is connected in parallel on a rectification side current conversion bus of the direct current system; u shape S 、Z S Voltage source voltage and series impedance of the equivalent model of thevenin of the alternating current system; z j (j =1,2, \8230;, 5) is the equivalent impedance of the ac line and the transformer.
In the simulation model, the applied disturbance is located in the photovoltaic system PV2, with the point of intersection being the center of oscillation. According to the equivalence principle, the equivalent power subsystem comprises a photovoltaic system PV2, so that the equivalent power subsystem internally contains an unstable pole.
According to the traditional impedance analysis method based on the 'source-load' system, the stability criterion of the multi-photovoltaic grid-connected direct-current outgoing system shown in fig. 2 is the ratio of the impedances of the power subsystem and the load subsystem, as shown in the following formula:
FIG. 7 is a Nyquist plot of the "source-to-charge" subsystem impedance ratio as shown in the above equation. As can be seen, the Nyquist curve does not encompass the critical point (-1, j 0). Thus, the system is stable as seen from conventional impedance analysis based on a "source-to-charge" system. As can be seen from fig. 3, the system cannot maintain stable operation after 25 s. Therefore, the stability analysis result obtained by the traditional impedance analysis method based on the source-load system is inconsistent with the simulation result of the PSCAD simulation model. Therefore, in a multi-photovoltaic grid-connected direct current outgoing system, when the equivalent subsystem does not meet the independent and stable condition, the traditional impedance analysis method based on the source-load system can obtain an incorrect stability analysis result.
According to the impedance analysis method of the multi-input multi-output system, a contrast matrix of the system can be written, and the formula is shown as follows:
contrast matrix L 2 And(s) is a three-dimensional full-rank square matrix, so that the photovoltaic decentralized access direct-current sending end system shown in fig. 2 has three characteristic functions l 1(s), l 2(s) and l 3(s) corresponding to three characteristic tracks l1, l2 and l3. The nyquist curve is plotted according to the feature functions l 1(s), l 2(s), and l 3(s), as shown in fig. 8.
As can be seen from fig. 8, the characteristic locus l1 is concentrated near the origin and to the right of the imaginary axis of the complex plane, and all poles represented by the characteristic locus are stable; the characteristic track l2 surrounds the critical point (-1, j 0) for one circle anticlockwise, and the crossing frequency is 63.8Hz; the characteristic trace l3 surrounds the critical point (-1, j 0) by one turn counterclockwise and the critical point (-1, j 0) by one turn clockwise, and the net surrounding turns are 0. According to the impedance analysis result, after the parameters of the photovoltaic system PV2 are changed, the multi-photovoltaic grid connection cannot keep stable operation through the direct current sending system, the voltage of a grid connection point of the PV2 oscillates, and the oscillation frequency is about 63.8 Hz.
The result of the impedance analysis of the multi-photovoltaic grid-connected direct-current transmission system is basically consistent with the simulation result of the PSCAD simulation model, which shows that the impedance analysis method based on the generalized Nyquist criterion can accurately analyze the stability of the multi-input multi-output system.
Example two
The embodiment provides a photovoltaic cluster direct current outgoing oscillation analysis system based on a multi-port matrix, which comprises:
the node branch classification module is used for constructing an equivalent multi-input multi-output port network based on a topological structure of the photovoltaic cluster direct-current delivery system, and classifying the nodes and the branches respectively according to types;
the node voltage equation building module is used for forming a node admittance matrix according to the node classification result and the branch classification result and building a node voltage equation in the form of a block matrix;
the closed-loop transfer function matrix construction module is configured to select photovoltaic and direct-current access nodes as research nodes and construct a photovoltaic cluster direct-current outgoing system closed-loop transfer function matrix containing a comparison matrix between current and voltage of the nodes;
and the system oscillation analysis module is used for judging the system oscillation stability by utilizing the characteristic locus of the return ratio matrix of the closed-loop transfer function matrix according to the generalized Nyquist criterion.
The modules are the same as the corresponding steps in the implementation examples and application scenarios, but are not limited to the disclosure of the first embodiment. It should be noted that the modules described above as part of a system may be implemented in a computer system such as a set of computer-executable instructions.
In the foregoing embodiments, the description of each embodiment has an emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions in other embodiments.
The proposed system can be implemented in other ways. For example, the above-described system embodiments are merely illustrative, and for example, the division of the above-described modules is merely a logical division, and in actual implementation, there may be other divisions, for example, multiple modules may be combined or integrated into another system, or some features may be omitted, or not executed.
EXAMPLE III
The present embodiment provides a computer-readable storage medium, on which a computer program is stored, which when executed by a processor implements the steps in the method for analyzing dc outgoing oscillations of a photovoltaic cluster based on a multiport matrix as described in the first embodiment above.
Example four
The embodiment provides a computer device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and when the processor executes the computer program, the processor implements the steps in the method for analyzing dc outgoing oscillation of a photovoltaic cluster based on a multiport matrix as described in the first embodiment.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, and the like) having computer-usable program code embodied therein.
The present invention has been 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 flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive changes in the technical solutions of the present invention.
Claims (10)
1. A photovoltaic cluster direct current outgoing oscillation analysis method based on a multi-port matrix is characterized by comprising the following steps:
constructing an equivalent multi-input multi-output port network based on a topological structure of a photovoltaic cluster direct-current delivery system, and classifying nodes and branches respectively according to types;
forming a block node admittance matrix according to the node classification result and the branch classification result, and constructing a node voltage equation in the form of a block matrix;
selecting photovoltaic and direct current access nodes as research nodes, and constructing a photovoltaic cluster direct current outgoing system closed loop transfer function matrix containing a comparison matrix between node current and voltage;
and judging the oscillation stability of the system by utilizing the characteristic locus of a return ratio matrix of the closed-loop transfer function matrix according to the generalized Nyquist criterion.
2. The photovoltaic cluster direct current outgoing oscillation analysis method based on the multiport matrix according to claim 1, wherein an equivalent multiple-input multiple-output port network is constructed based on a topological structure of the photovoltaic cluster direct current outgoing system, and nodes and branches are respectively classified according to types, specifically:
the method comprises the steps of dividing nodes in the multiport network into photovoltaic or direct current access nodes and other nodes, and dividing branches into grounding branches and node connection branches.
3. The method according to claim 1, wherein the step of forming a block node admittance matrix according to the node classification result and the branch classification result to construct a node voltage equation in the form of a block matrix comprises:
converting the branch admittance matrix into a form of a block matrix according to branch classification results to obtain a block branch admittance matrix;
converting the incidence matrix into a form of a block matrix according to the node classification result and the branch classification result to obtain a block incidence matrix;
determining a block node admittance matrix based on the block branch admittance matrix and the block incidence matrix;
and constructing a node voltage equation in the form of a block matrix by using the determined block node admittance matrix.
4. The method according to claim 3, wherein the nodal voltage equation in the form of a block matrix is
In the formula of U A And I A Voltage and injection current, U, of photovoltaic or DC access nodes, respectively L And I L Voltages and injection currents, Y, of the remaining nodes, respectively 11 And Y 22 Self-admittance, Y, of the remaining nodes and of the photovoltaic or DC access node, respectively 12 And Y 21 Respectively the mutual admittance of the other nodes and the photovoltaic or direct current access node.
5. The method according to claim 1, wherein the closed-loop transfer function matrix of the photovoltaic trunking dc delivery system, which includes a return-to-reference matrix between the node current and the node voltage, specifically comprises:
wherein E is a unit matrix and Y is d11 Is a diagonal array of ground branch admittances; y is d22 Is a diagonal array of series branch admittances;
an impedance matrix for an ac system;
is the admittance matrix of the photovoltaic and direct current system.
6. The photovoltaic cluster direct-current outgoing oscillation analysis method based on the multiport matrix as claimed in claim 1, wherein the closed-loop transfer-back ratio matrix is specifically:
L(s)＝Z L Y A
wherein,
an impedance matrix for an ac system;
is the admittance matrix of photovoltaic and DC systems.
7. The photovoltaic cluster direct-current outgoing oscillation analysis method based on the multiport matrix as claimed in claim 1, wherein the system oscillation stability is judged by using a characteristic trajectory of a closed loop transfer return ratio matrix according to a generalized nyquist criterion, specifically:
according to the generalized Nyquist criterion, when the number of net turns of the characteristic track around the critical point (-1, j 0) in the anticlockwise direction is equal to the number of poles of the right half-plane of the contrast matrix L(s), the system is stable; conversely, the system is unstable.
8. Photovoltaic cluster direct current outgoing oscillation analysis system based on multiport matrix, its characterized in that includes:
the node branch classification module is used for constructing an equivalent multi-input multi-output port network based on a topological structure of the photovoltaic cluster direct-current delivery system, and classifying the nodes and the branches respectively according to types;
the block node voltage equation building module is used for forming a block node admittance matrix according to the node classification result and the branch classification result and building a node voltage equation in the form of a block matrix;
the closed-loop transfer function matrix construction module is configured to select photovoltaic and direct-current access nodes as research nodes and construct a photovoltaic cluster direct-current delivery system closed-loop transfer function matrix containing a return matrix between the current and the voltage of the nodes;
and the system oscillation analysis module is used for judging the system oscillation stability by utilizing the characteristic track of the return ratio matrix of the closed-loop transfer function matrix according to the generalized Nyquist criterion.
9. A computer-readable storage medium, on which a computer program is stored, which program, when being executed by a processor, carries out the steps of the multiport matrix based pv cluster dc outgoing oscillation analysis method according to any of claims 1 to 7.
10. A computer arrangement comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor when executing the program carries out the steps in the multiport matrix based pv cluster dc outgoing oscillation analyzing method as claimed in any of the claims 1 to 7.
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| CN116505520A (en) * | 2023-06-26 | 2023-07-28 | 国网江西省电力有限公司电力科学研究院 | Oscillation suppression method and system for photovoltaic grid-connected power generation system |
| CN117996712A (en) * | 2024-04-07 | 2024-05-07 | 广东电网有限责任公司珠海供电局 | Method and device for determining stability of direct current power distribution system |
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| CN116505520A (en) * | 2023-06-26 | 2023-07-28 | 国网江西省电力有限公司电力科学研究院 | Oscillation suppression method and system for photovoltaic grid-connected power generation system |
| CN116505520B (en) * | 2023-06-26 | 2023-11-07 | 国网江西省电力有限公司电力科学研究院 | Oscillation suppression method and system for photovoltaic grid-connected power generation system |
| CN117996712A (en) * | 2024-04-07 | 2024-05-07 | 广东电网有限责任公司珠海供电局 | Method and device for determining stability of direct current power distribution system |
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