CN115700956A - Photovoltaic cluster direct current outgoing oscillation analysis method and system based on multiport matrix - Google Patents

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

Oscillation analysis method and system for photovoltaic cluster DC output based on multi-port matrix

technical field

The invention belongs to the technical field of power system broadband oscillation analysis, and in particular relates to a multi-port matrix-based photovoltaic cluster DC external transmission oscillation analysis method and system.

Background technique

The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

Photovoltaics rely on power electronic inverters to connect to the grid, and DC transmission is based on power electronic conversion technology. Previous engineering and research experience have shown that there is a risk of wide-frequency oscillation between multiple power electronic equipment, which is an important factor for the safe operation of new power systems. bring challenges.

The eigenvalue analysis based on the state-space model is a classic research tool for the small disturbance dynamic process, which can provide all the model information of the dynamic process, so it can be used as a verification method for offline analysis. However, with the large-scale power electronics of power systems, it is not convenient to use eigenvalue analysis for broadband oscillation analysis. Broadband oscillation only needs to analyze the mode with a damping ratio of zero or very small, while the impedance analysis method only establishes the input or output impedance model of the research object, and analyzes the system oscillation frequency according to the relationship between impedances, which fully meets the analysis requirements of broadband oscillation. In recent years, it has been widely used in power electronic equipment systems. However, the traditional impedance analysis method is proposed based on a single-input single-output system, and its applicability to multiple-input multiple-output systems is obviously limited.

In some studies, the MIMO system is equivalently transformed into a single-input-single-output system and then the traditional impedance analysis method is applied. However, this method may lose some oscillation modes during the conversion process, resulting in inconsistent analysis conclusions.

Contents of the invention

In order to solve the above problems, the present invention proposes a multi-port matrix-based photovoltaic cluster DC external transmission oscillation analysis method and system. When the traditional impedance analysis method is applied to a multiple-input multiple-output system, the present invention is based on an equivalent single-input single-output The method of "source-load" subsystem has problems such as strict assumptions and indistinct unstable poles. The present invention proposes an impedance analysis method based on multi-port impedance matrix and generalized Nyquist criterion without multi-input Equivalent transformation from multi-output to single-input and single-output system, directly analyze the multi-input and multi-output system in the form of matrix, which is used for the oscillation stability analysis of the grid-connected photovoltaic cluster through the DC output system. The invention utilizes the block node voltage equation of the system to construct a closed-loop expression form that can include all unstable poles, and judges the stability of the system according to the characteristic track of the return-ratio matrix of the closed-loop transfer function. The method improves the applicability of the impedance analysis method while ensuring the accuracy of the stability analysis.

According to some embodiments, the first solution of the present invention provides a multi-port matrix-based method for analyzing oscillations of photovoltaic cluster direct current transmission, which adopts the following technical solution:

An analysis method for photovoltaic cluster DC external transmission oscillation based on multi-port matrix, including:

Based on the topological structure of the photovoltaic cluster DC external transmission system, an equivalent multi-input and multi-output port network is constructed, and the nodes and branches are classified according to the type;

Based on the node classification results and branch classification results, the block node admittance matrix is formed, and the node voltage equation in the form of block matrix is constructed;

Select photovoltaic and DC access nodes as the research nodes, and construct the closed-loop transfer function matrix of the photovoltaic cluster DC output system including the return ratio matrix between the node current and voltage;

According to the generalized Nyquist criterion, the oscillation stability of the system is judged by using the characteristic trajectory of the return ratio matrix of the closed-loop transfer function matrix.

Further, based on the topological structure of the photovoltaic cluster DC external transmission system, an equivalent multi-input and multi-output port network is constructed, and nodes and branches are classified according to types, specifically:

The nodes in the multi-port network are divided into photovoltaic or DC access nodes and other nodes, and the branches are divided into grounding branches and node connection branches.

Further, the block node admittance matrix is formed according to the node classification result and the branch classification result, and a node voltage equation in the form of a block matrix is constructed, including:

According to the branch classification results, the branch admittance matrix is converted into the form of block matrix, and the block branch admittance matrix is obtained;

According to the node classification results and branch classification results, the association matrix is converted into the form of block matrix, and the block association matrix is obtained;

Based on the block branch admittance matrix and the block correlation matrix, determine the block node admittance matrix;

Using the determined block node admittance matrix, the node voltage equation in block matrix form is constructed.

Further, the node voltage equation in the block matrix form is

In the formula, U _A and I _A are the voltage and injection current of photovoltaic or DC access nodes, U _L and I _L are the voltage and injection current of other nodes, respectively, Y ₁₁ and Y ₂₂ are the remaining nodes and photovoltaic or DC The self-admittance of the access node, Y ₁₂ and Y ₂₁ are the mutual admittance of the remaining nodes and the photovoltaic or DC access node, respectively.

Further, the closed-loop transfer function matrix of the photovoltaic cluster DC external transmission system including the return ratio matrix between the node current and the voltage is specifically:

为交流系统的阻抗矩阵；

为光伏与直流系统的导纳矩阵。In the formula, E is the unit matrix, Y _d11 is the diagonal matrix of the grounding branch admittance; Y _d22 is the diagonal matrix of the series branch admittance;

is the impedance matrix of the AC system;

is the admittance matrix of photovoltaic and DC systems.

Further, the closed loop transfers back the ratio matrix, specifically:

L(s)=Z _L Y _A

为交流系统的阻抗矩阵；

为光伏与直流系统的导纳矩阵。in,

is the impedance matrix of the AC system;

is the admittance matrix of photovoltaic and DC systems.

Further, according to the generalized Nyquist criterion, the characteristic trajectory of the closed-loop transfer-back ratio matrix is used to judge the oscillation stability of the system, specifically:

According to the generalized Nyquist criterion, the system is stable when the number of net circles surrounding the critical point (-1, j0) in the counterclockwise direction of the characteristic trajectory is equal to the number of poles in the right half plane of the return ratio matrix L(s); Otherwise, the system is unstable.

According to some embodiments, the second solution of the present invention provides a multi-port matrix-based photovoltaic cluster DC external transmission oscillation analysis system, which adopts the following technical solution:

A photovoltaic cluster DC output oscillation analysis system based on a multi-port matrix, including:

The node branch classification module is used to construct an equivalent multi-input multi-output port network based on the topology structure of the photovoltaic cluster DC output system, and classify the nodes and branches according to the type;

The block node voltage equation building module is used to form a block node admittance matrix according to the node classification result and the branch classification result, and construct a block node voltage equation in the form of a block matrix;

The closed-loop transfer function matrix construction module is configured to select the photovoltaic and DC access nodes as the research nodes, and construct the closed-loop transfer function matrix of the photovoltaic cluster DC output system including the return ratio matrix between the node current and voltage;

The system oscillation analysis module is used for judging the system oscillation stability by using 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 present invention provides a computer-readable storage medium.

A computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the steps in the multi-port matrix-based photovoltaic cluster DC external transmission oscillation analysis method described in the first aspect above are implemented.

According to some embodiments, a fourth aspect of the present invention provides a computer device.

A computer device, comprising a memory, a processor, and a computer program stored on the memory and operable on the processor, when the processor executes the program, the multi-port matrix-based Steps in the analysis method of photovoltaic cluster direct current transmission oscillation.

Compared with prior art, the beneficial effect of the present invention is:

1. The present invention expands the impedance analysis method from a single-input-single-output system to a multiple-input-multiple-output system in the form of a matrix, avoiding the disadvantages of hidden modes when the multi-port system is equivalently simplified to a single-input single-output system. The assumption conditions only need to satisfy that each subsystem is stable when it operates independently. Compared with the impedance analysis method based on the "source-charge" subsystem, the assumption conditions are weaker and reasonable, and the method has a wider application range.

2. The present invention uses the system block node voltage matrix to construct the closed-loop transfer function matrix of the MIMO system, which can correctly reflect all the poles of the MIMO system, and avoids the situation that the poles and zeros of the system are not displayed due to the cancellation of the poles and zeros . This method can correctly reflect the system stability even when there are unstable poles inside the "source-load" subsystem.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention.

Fig. 1 is a flow chart of a photovoltaic cluster DC external transmission oscillation analysis method based on a multi-port impedance matrix in an embodiment of the present invention;

Fig. 2 is a schematic structural diagram of a simulation model of a multi-grid-connected photovoltaic external transmission system via DC in an embodiment of the present invention;

Fig. 3 is the busbar Bus5 voltage response curve in the embodiment of the present invention;

Fig. 4 is the fast Fourier transform analysis result of Bus5 busbar voltage in the embodiment of the present invention;

Fig. 5 is the active power that photovoltaic system PV2 exports in the embodiment of the present invention;

Fig. 6 is an equivalent circuit diagram of a multi-grid-connected photovoltaic transmission system via DC in an embodiment of the present invention;

Fig. 7 is the analysis result of the traditional impedance analysis method based on the "source-charge" system in the embodiment of the present invention;

Fig. 8 is the characteristic trajectory of the echo ratio matrix in the embodiment of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present invention. 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 should be noted that the terminology used here is only for describing specific embodiments, and is not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

In the case of no conflict, the embodiments and the features in the embodiments of the present invention can be combined with each other.

Embodiment one

This embodiment provides a multi-port matrix-based DC output oscillation analysis method for photovoltaic clusters. In this embodiment, this method is applied to servers for illustration. It can be understood that this method can also be applied to terminals, and can also be applied to It includes terminals, servers and systems, and is realized through the interaction between terminals and servers. The server can be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or it can provide cloud services, cloud database, cloud computing, cloud function, cloud storage, network server, cloud communication, intermediate Cloud servers for basic cloud computing services such as software services, domain name services, security service CDN, and big data and artificial intelligence platforms. The terminal may be a smart phone, a tablet computer, a laptop computer, a desktop computer, a smart speaker, a smart watch, etc., but is not limited thereto. The terminal and the server may be connected directly or indirectly through wired or wireless communication, which is not limited in this application. In this embodiment, the method includes the following steps:

Based on the topological structure of the photovoltaic cluster DC external transmission system, an equivalent multi-input and multi-output port network is constructed, and the nodes and branches are classified according to the type;

Based on the node classification results and branch classification results, the block node admittance matrix is formed, and the node voltage equation in the form of block matrix is constructed;

Select photovoltaic and DC access nodes as the research nodes, and construct the closed-loop transfer function matrix of the photovoltaic cluster DC output system including the return ratio matrix between the node current and voltage;

According to the generalized Nyquist criterion, the oscillation stability of the system is judged by using the characteristic trajectory of the return ratio matrix of the closed-loop transfer function matrix.

Specifically, as shown in FIG. 1 , this embodiment provides a multi-port impedance matrix-based method for analyzing oscillation of photovoltaic cluster direct current transmission, which specifically includes:

1. Based on the topological structure of the photovoltaic cluster DC transmission system, construct an equivalent multi-input and multi-output port network, and classify nodes and branches according to types

The nodes in the photovoltaic grid-connected DC transmission system are divided into photovoltaic/DC access nodes and other nodes; the branches are divided into grounding branches and series branches.

2. According to the classification results of nodes and branches, a block node admittance matrix is formed, and a node voltage equation in the form of a block matrix is constructed

According to the classification of branches, the branch admittance matrix can be expressed in the form of block matrix:

In the formula: Y _d is the branch admittance matrix, Y _d11 is the admittance diagonal matrix formed by the grounded branch; Y _d22 is the admittance diagonal matrix formed by the node connection branch.

Also according to the classification of branches and nodes, the incidence matrix can also be expressed in the form of a block matrix:

In the formula: A is the correlation matrix, A ₂₁ is the correlation matrix between the DC or photovoltaic access node and the grounding branch; A ₂₂ is the correlation matrix between the DC or photovoltaic access node and the node connection branch. A ₁₁ is an association matrix between other nodes and grounding branches; A ₁₂ is an association matrix between other nodes and node connecting branches.

According to the branch admittance matrix and incidence matrix, the node admittance matrix Y in block matrix form can be expressed as:

The node voltage equation in block matrix form is

In the formula, U _A and I _A are the voltage and injection current of photovoltaic or DC access nodes, U _L and I _L are the voltage and injection current of other nodes, respectively, Y ₁₁ and Y ₂₂ are the remaining nodes and photovoltaic or DC The self-admittance of the access node, Y ₁₂ and Y ₂₁ are the mutual admittance of the remaining nodes and the photovoltaic or DC access node, respectively.

3. Select photovoltaic and DC access nodes as research nodes, and construct the closed-loop transfer function matrix of the photovoltaic cluster DC output system including the return ratio matrix between the node current and voltage

The subsynchronous oscillation of the new energy grid-connected system is caused by the power electronic converter. Therefore, the photovoltaic and DC access nodes are selected as the research nodes, and the closed-loop transfer of the photovoltaic cluster DC output system with a return ratio matrix between the node current and voltage is constructed. function matrix.

为交流系统的阻抗矩阵；

为光伏与直流系统的导纳矩阵。In the formula, E is the unit matrix, Y _d11 is the diagonal matrix of the grounding branch admittance; Y _d22 is the diagonal matrix of the series branch admittance;

is the impedance matrix of the AC system;

is the admittance matrix of photovoltaic and DC systems.

According to the definition of the return ratio matrix, the return ratio matrix of the closed-loop transfer function matrix of the system is:

L(s)＝Z _L Y _A (6)

4. According to the generalized Nyquist criterion, the characteristic trajectory of the closed-loop transfer-back ratio matrix is used to judge the oscillation stability of the system

According to the generalized Nyquist criterion, the system is stable when the number of net turns surrounding the critical point (-1, j0) in the counterclockwise direction of the characteristic trajectory is equal to the number of poles of the return ratio matrix L(s) in the right half plane.

In the return ratio matrix of the closed-loop system, the impedance matrix Z _L of the AC system is composed of the impedance of the system, and there is no right-half-plane pole. Assuming that each subsystem is stable when operating independently, the admittance matrix Y _A of the photovoltaic and DC systems also has no right-half-plane poles. Therefore, the necessary and sufficient condition for the stability of the system is: the characteristic trajectory of the echo ratio matrix L(s) does not surround the critical point (-1, j0).

It should be noted that this method assumes that each subsystem is stable when it operates independently, which means that each photovoltaic, DC or AC system in the system operates independently and is stable, not the equivalent power supply subsystem or load subsystem.

5. Case analysis

Based on the IEEE 9-node standard calculation example and the CIGRE standard DC test system, a simulation scene of multi-photovoltaic grid-connected grid-connected through DC output is built in PSCAD. First, set the coherent unit of synchronous generators of each generator node in the IEEE 9 node standard calculation example to "4", and adjust the system load level to match the system capacity with the CIGRE DC standard system transmission capacity. The rectification side of the CIGRE DC standard system is connected to bus Bus 8, and the parallel reactive power compensation device on the rectification side is increased to 37.342uF. The AC system on the inverter side is replaced by an ideal power supply, and the filter and reactive power compensation device on the inverter side are disconnected. The two-stage photovoltaic system PV1 and PV2 are connected to the grid at the busbar Bus5 and Bus8 respectively, and its parameters are shown in Table 1.

Table 1 Two-stage photovoltaic system PV1 and PV2 parameters

At 25s, the proportional coefficient of the inner loop current control PI link of the photovoltaic system PV2 decreases from 0.2 to 0.02, and the integral coefficient increases from 20 to 53.

As shown in Figure 3, it is the simulation result of the multi-photovoltaic grid-connected DC external transmission system. From the voltage waveform of bus Bus5, it can be seen that the multi-photovoltaic grid-connected DC external transmission system maintains a stable operating state before 25s. After the disturbance occurs, Bus5 The bus voltage oscillates, and the system cannot maintain a stable operation state. As shown in Figure 4, it can be seen from the fast Fourier transform analysis results of Bus5 bus voltage that after 25s, the bus Bus5 voltage not only contains a power frequency component of 50Hz, but also a component with an oscillation frequency of 61Hz. As shown in Figure 5, after 25s the parameters of the photovoltaic system PV2 are changed, the active power output by the photovoltaic system PV2 oscillates with equal amplitude.

Next, based on the traditional impedance analysis method of the "source-load" system, the stability analysis of the multi-photovoltaic grid-connected DC external transmission system is carried out. First, the multi-photovoltaic grid-connected system shown in Figure 2 is equivalent to a single-input single-output system composed of a power supply subsystem and a load subsystem, as shown in Figure 6. According to the power flow direction of the system, the DC system inside the virtual frame is equivalent to the load subsystem, and the part outside the virtual frame is equivalent to the power subsystem. The input/output impedance of the power supply subsystem and the load subsystem is calculated by methods such as series connection and parallel connection. In the figure, I _Pi and Z _Pi (i=1,2) are the current source current and parallel impedance of the Norton equivalent model of photovoltaic system PV1 and PV2; I _D and Z _D are the current source current of the Norton equivalent model of the DC system and parallel impedance; Z _F is the equivalent impedance of the parallel filter device and reactive power compensation device on the commutation bus on the rectification side of the DC system; U _S and Z _S are the voltage source voltage and series impedance of the Thevenin equivalent model of the AC system; Z _j (j=1,2,...,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, and its grid-connected point is the oscillation center. According to the principle of equivalence, the equivalent power subsystem contains the photovoltaic system PV2, so the equivalent power subsystem contains unstable poles.

According to the traditional impedance analysis method based on the "source-load" system, the stability criterion of the multi-photovoltaic grid-connected system shown in Figure 2 is the impedance ratio of the above-mentioned power supply subsystem and load subsystem, as shown in the following formula:

Figure 7 shows the Nyquist curve of the impedance ratio of the "source-to-charge" subsystem shown in the above formula. It can be seen from the figure that the Nyquist curve does not surround the critical point (-1, j0). Therefore, the system is stable according to the traditional impedance analysis method based on the "source-charge" system. However, it can be seen from Figure 3 that the system cannot maintain stable operation after 25s. It can be seen that the stability analysis results obtained by the traditional impedance analysis method based on the "source-load" system do not match the simulation results of the PSCAD simulation model. Therefore, in the multi-PV grid-connected DC transmission system, when the equivalent subsystem does not meet the independent stability conditions, the traditional impedance analysis method based on the "source-load" system will get wrong stability analysis results.

According to the impedance analysis method of the multiple-input multiple-output system, the return ratio matrix of the system can be written, as shown in the following formula:

The return ratio matrix L ₂ (s) is a three-dimensional full-rank square matrix, so the photovoltaic decentralized access DC sending end system shown in Figure 2 has three characteristic functions l1(s), l2(s) and l3(s), corresponding to three characteristics Tracks l1, l2 and l3. Draw the Nyquist curve according to the characteristic functions l1(s), l2(s) and l3(s), as shown in Figure 8.

It can be seen from Fig. 8 that the characteristic trajectory l1 is concentrated near the origin and on the right side of the imaginary axis of the complex plane, and all the poles represented by the characteristic trajectory are stable; the characteristic trajectory l2 surrounds the critical point (-1, j0) in a circle counterclockwise, and The crossing frequency is 63.8 Hz; the characteristic trajectory l3 surrounds the critical point (-1, j0) counterclockwise and surrounds the critical point (-1, j0) clockwise, and the net number of encircling circles is 0. According to the impedance analysis results, after the PV2 parameters are changed, the multi-PV grid-connected system cannot maintain stable operation through the DC output system, and the PV2 grid-connected point voltage oscillates, and the oscillation frequency is about 63.8Hz.

The results of the impedance analysis of the multi-photovoltaic grid-connected DC external transmission system are basically consistent with the simulation results of the PSCAD simulation model, which shows that the impedance analysis method based on the generalized Nyquist criterion proposed in this paper can accurately analyze the stability of the multi-input and multi-output system. sex.

Embodiment two

This embodiment provides a photovoltaic cluster DC external transmission oscillation analysis system based on a multi-port matrix, including:

The node branch classification module is used to construct an equivalent multi-input multi-output port network based on the topology structure of the photovoltaic cluster DC output system, and classify the nodes and branches according to the type;

The block node voltage equation building module is used to form a block node admittance matrix according to the node classification result and the branch classification result, and construct a block node voltage equation in the form of a block matrix;

The closed-loop transfer function matrix construction module is configured to select the photovoltaic and DC access nodes as the research nodes, and construct the closed-loop transfer function matrix of the photovoltaic cluster DC output system including the return ratio matrix between the node current and voltage;

The system oscillation analysis module is used for judging the system oscillation stability by using the characteristic track of the return ratio matrix of the closed-loop transfer function matrix according to the generalized Nyquist criterion.

The examples and application scenarios implemented by the above modules and corresponding steps are the same, but are not limited to the content disclosed in the first embodiment above. It should be noted that, as a part of the system, the above-mentioned modules can be executed in a computer system such as a set of computer-executable instructions.

The description of each embodiment in the foregoing embodiments has its own emphases, and for parts not described in detail in a certain embodiment, reference may be made to relevant descriptions of other embodiments.

The proposed system can be implemented in other ways. For example, the above-described system embodiments are only illustrative. For example, the division of the above modules is only a logical function division. In actual implementation, there may be other division methods, for example, multiple modules can be combined or integrated into another A system, or some feature, can be ignored, or not implemented.

Embodiment three

This embodiment provides a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, the multi-port matrix-based photovoltaic cluster DC output oscillation analysis method described in the first embodiment is implemented. A step of.

Embodiment four

This embodiment provides a computer device, which includes a memory, a processor, and a computer program stored in the memory and operable on the processor. When the processor executes the program, the above-mentioned first embodiment based on Steps in the analysis method for DC external transmission oscillation of photovoltaic cluster with multi-port matrix.

Those skilled in the art should understand that the embodiments of the present invention may be provided as methods, systems, or computer program products. Accordingly, the present invention can 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 and optical storage, etc.) having computer-usable program code embodied therein.

The present invention 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 should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be implemented through computer programs to instruct related hardware, and the programs can be stored in a computer-readable storage medium. During execution, it may include the processes of the embodiments of the above-mentioned methods. Wherein, the storage medium may be a magnetic disk, an optical disk, a read-only memory (Read-Only Memory, ROM) or a random access memory (Random Access Memory, RAM) and the like.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope 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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