A static voltage stability evaluation method and system for a multi-station grid-connected system

Abstract

The present invention belongs to the technical field of static voltage stability of multi-station grid-connected systems, and provides a method and system for evaluating static voltage stability of multi-station grid-connected systems. According to the multi-station grid-connected system model, a corresponding power flow equation group is established, and a Jacobian matrix is ​​written according to the power flow equation group; the Jacobian matrix is ​​transformed to obtain a conversion matrix, and the conversion matrix is ​​optimized; according to the optimized conversion matrix, the critical conditions for static voltage stability are converted and converted into the minimum eigenvalue of the solution matrix; the minimum eigenvalue of the solution matrix is ​​used as a static voltage stability evaluation index, and the static voltage stability is evaluated according to the range of the index value. The present invention takes into account the influence of phase differences and line resistance between stations, constructs a conversion matrix based on the Jacobian matrix, and proposes a new evaluation index based on this, providing a new idea for static stability evaluation of multi-station grid-connected systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of static voltage stability of a multi-station grid-connected system, and in particular relates to a static voltage stability evaluation method and system for a multi-station grid-connected system. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] With the incorporation of a large number of new energy sources such as wind power and photovoltaic power into the power grid, the support capacity of the power system has been reduced, and the risk of system voltage stability has increased. In order to prevent problems such as voltage instability in the system, it is of great significance to correctly analyze the static voltage stability of the multi-station grid-connected system.

[0004] At present, the main methods for analyzing system static voltage stability include analytical methods, Jacobian matrix singular analysis methods, etc., and stability evaluation indicators such as short-circuit ratio and eigenvalue have been proposed. However, the above indicators have problems such as low linearization and insufficient consideration of the injection of multiple renewable energy stations. In addition, most traditional analysis methods ignore the influence of phase differences between stations, resulting in inaccurate analysis and other problems, which have certain limitations. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a static voltage stability evaluation method and system for a multi-station grid-connected system. The present invention takes into account the influence of phase differences and line resistance between stations, constructs a conversion matrix based on the Jacobian matrix, and proposes new evaluation indicators based on the conversion matrix, which provides a new idea for the static stability evaluation of a multi-station grid-connected system.

[0006] According to some embodiments, the present invention adopts the following technical solutions:

[0007] A method for evaluating static voltage stability of a multi-station grid-connected system comprises the following steps:

[0008] According to the multi-station grid-connected system model, a corresponding power flow equation group is established, and a Jacobian matrix is ​​written according to the power flow equation group;

[0009] The Jacobian matrix is ​​transformed to obtain a transformation matrix, and the transformation matrix is ​​optimized;

[0010] According to the optimized conversion matrix, the critical condition of static voltage stability is converted into the minimum eigenvalue of the solution matrix;

[0011] The minimum eigenvalue of the solution matrix is ​​used as a static voltage stability evaluation index, and static voltage stability evaluation is performed according to a range of the index value.

[0012] As an optional implementation method, based on the multi-station grid-connected system model, the process of establishing the corresponding power flow equation group includes: treating all new energy stations as PQ nodes, the external power grid is equivalent to an infinite power grid through the Thevenin method, regarded as a balance node, and constructing the power equation corresponding to the PQ node.

[0013] As an optional implementation, the process of writing the Jacobian matrix according to the power flow equations includes calculating the value of each element of the Jacobian matrix according to the power equation corresponding to the PQ node to form the Jacobian matrix.

[0014] As an optional implementation, the process of converting the Jacobian matrix to obtain the conversion matrix includes obtaining the Jacobian matrix J, converting the Jacobian matrix to obtain the matrix A ,make:

[0015] .

[0016] As an optional implementation, the process of optimizing the conversion matrix includes re-dividing the conversion matrix, and ignoring elements or taking the average value of elements according to the characteristics of the diagonal and non-main diagonal elements, and approximating the conversion matrix as follows:

[0017] ;

[0018] in, , ;

[0019] For Node i The active power, For Node i The voltage amplitude, is the corresponding susceptance value, For Node i, j The phase angle difference between them.

[0020] As an optional implementation, the static voltage stability critical condition is converted into the minimum eigenvalue of the solution matrix, and the process includes: converting the static voltage stability evaluation into the solution matrix The minimum eigenvalue of ,make .

[0021] As an optional implementation, according to the range of the index value, the process of evaluating the static voltage stability includes: , it indicates that the system static voltage is stable; if , it indicates that the system static voltage is unstable; When , it indicates that the system is in the critical state of static voltage stability.

[0022] A static voltage stability assessment system for a multi-station grid-connected system, comprising:

[0023] A matrix writing module is configured to establish a corresponding power flow equation group according to a multi-station grid-connected system model, and write a Jacobian matrix according to the power flow equation group;

[0024] A matrix conversion module is configured to convert the Jacobian matrix to obtain a conversion matrix and optimize the conversion matrix;

[0025] An indicator conversion module is configured to convert the static voltage stability critical condition according to the optimized conversion matrix and convert it into the minimum eigenvalue of the solution matrix;

[0026] The stability evaluation module is configured to use the minimum eigenvalue of the solution matrix as a static voltage stability evaluation index and perform static voltage stability evaluation according to a range of the index value.

[0027] A computer-readable storage medium is used to store computer instructions, and when the computer instructions are executed by a processor, the steps in the above method are completed.

[0028] An electronic device comprises a memory and a processor, and computer instructions stored in the memory and executed on the processor. When the computer instructions are executed by the processor, the steps in the above method are completed.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention constructs a practical multi-station static voltage stability evaluation index, and transforms the original static voltage stability evaluation method into a comparison between the proposed evaluation index and the set value, which not only simplifies the evaluation method, but also makes the index more linear, realizes the static voltage stability evaluation of the multi-station grid-connected system, and improves the reliability of the voltage stability evaluation.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0033] Figure 1 is a simplified topology diagram of a multi-station grid-connected system of an embodiment;

[0034] Figure 2 The present invention is a schematic diagram of a flow chart of static voltage stability determination according to an embodiment. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0036] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0037] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0038] In the absence of conflict, the embodiments in this application and the features in the embodiments may be combined with each other.

[0039] Embodiment 1

[0040] A static voltage stability assessment method for a multi-station grid-connected system, such as Figure 2 As shown, the following steps are included:

[0041] According to the multi-station grid-connected system model, a corresponding power flow equation group is established, and a Jacobian matrix is ​​written according to the power flow equation group;

[0042] The Jacobian matrix is ​​transformed to obtain a transformation matrix, and the transformation matrix is ​​optimized;

[0043] According to the optimized conversion matrix, the critical condition of static voltage stability is converted into the minimum eigenvalue of the solution matrix;

[0044] The minimum eigenvalue of the solution matrix is ​​used as a static voltage stability evaluation index, and static voltage stability evaluation is performed according to a range of the index value.

[0045] The following describes the details of each step.

[0046] The first step is to establish the Jacobian matrix of the multi-station grid-connected system.

[0047] like Figure 1 As shown in the figure, the multi-station grid-connected system simplifies the topology structure, and photovoltaic, wind power and other new energy stations are regarded as PQ nodes; the external power grid is equivalent to an infinite power grid through the Thevenin equation and is regarded as a balanced node. The power equation corresponding to the PQ node is:

[0048] (1)

[0049] In the formula, For Node i The active power, For Node i The reactive power, For Node i The voltage amplitude, For Node j The voltage amplitude, is the corresponding conductance value, is the corresponding susceptance value, For Node i, j The phase difference between n is the number of system nodes.

[0050] Then, the values ​​of each element of the Jacobian matrix are calculated by equations (3) and (4), and then the Jacobian matrix is ​​constructed. J , whose structure is shown in formula (2).

[0051] (2)

[0052] 1) When When , the calculation method of the non-main diagonal elements of each matrix is ​​as follows:

[0053] (3)

[0054] 2) When , the calculation method of the main diagonal elements of each matrix is ​​as follows:

[0055] (4)

[0056] In the subsequent introduction and specific examples, in order to simplify the analysis process, a simple 3-node system is used, where nodes 1 and 2 are PQ nodes on the station side, and node 3 is a balancing node on the infinite grid side. The resulting Jacobian matrix is:

[0057] (5)

[0058] Next, transform the Jacobian matrix to obtain the matrix A ,make:

[0059] (6)

[0060] After substituting the specific element values ​​of Jacobi in the example, the matrix A is obtained as follows:

[0061] (7)

[0062] The matrix A Re-block, get:

[0063] (8)

[0064] Analyzing the matrix, we can see that the matrix and The non-main diagonal elements are relatively small, so they are ignored, forming a diagonal matrix D , its specific elements are as follows:

[0065] (9)

[0066] P i Refers to the node i The active power.

[0067] For the matrix and , the non-main diagonal elements are the same, and the elements in the main diagonal positions of the two matrices are The existence of leads to inequality, but considering The value is relatively small, so the values ​​of the corresponding elements are not much different, so the average value of the elements at the corresponding positions of the main diagonal is taken to form a new matrix C The corresponding elements in are calculated as shown in formula (10).

[0068] (10)

[0069] Keep Matrix and The non-main diagonal elements of remain unchanged, and the main diagonal elements are calculated by formula (10), thus forming a new matrix C :

[0070] (11)

[0071] Finally, the matrix A Approximately:

[0072] (12)

[0073] Then, the original static voltage stability critical condition is converted:

[0074] (13)

[0075] From the above formula, we can see that the static voltage stability evaluation is converted into solving the matrix The minimum eigenvalue of , so let:

[0076] (14)

[0077] in, is the eigenvalue of matrix J, For the matrix The characteristic value of .

[0078] The Newton-Raphson method is used to solve the power flow of the multi-station grid-connected system and obtain the construction matrix Required elements .

[0079] Eventually As a new type of static voltage stability evaluation index, the static voltage stability evaluation method is as follows: , it indicates that the system static voltage is stable; if , it indicates that the system static voltage is unstable; When , it indicates that the system is in the critical state of static voltage stability.

[0080] Embodiment 2

[0081] Based on the first embodiment, the voltage and phase initial values ​​of the PQ nodes corresponding to each station and the given P and Q values ​​are shown in the following formula, where for power, a positive value represents the emitted power and a negative value represents the absorbed power.

[0082] (15)

[0083] The voltage and phase of the corresponding balancing node on the infinite grid side are:

[0084] (16)

[0085] The system admittance matrix is ​​shown below:

[0086] (17)

[0087] After setting the corresponding parameters, change the active power emitted by node 1 , observe the changes of the proposed evaluation indicators, and the results are shown in Table 1.

[0088] Table 1 Index results obtained by changing P1

[0089]

[0090] It can be seen that when other parameters remain unchanged, as the active power emitted by node 1 increases, the matrix J The minimum value of the real part of the eigenvalue of gets smaller and smaller, and the proposed evaluation index also gets smaller and smaller until the system power flow diverges. In the case of number 4, the proposed index value is 1.0057, and the matrix JThe minimum value of the real part of the eigenvalue is also close to 0, which can be used as the critical equilibrium point. When P1 continues to increase, the system will experience power flow divergence, which proves the effectiveness of the method proposed in this invention. The proposed index value can be compared with 1. When it is greater than 1, the static voltage of the output system is stable, and when it is less than 1, the static voltage of the output system is unstable.

[0091] Embodiment 3

[0092] A static voltage stability assessment system for a multi-station grid-connected system, comprising:

[0093] A matrix writing module is configured to establish a corresponding power flow equation group according to a multi-station grid-connected system model, and write a Jacobian matrix according to the power flow equation group;

[0094] A matrix conversion module is configured to convert the Jacobian matrix to obtain a conversion matrix and optimize the conversion matrix;

[0095] An indicator conversion module is configured to convert the static voltage stability critical condition according to the optimized conversion matrix and convert it into the minimum eigenvalue of the solution matrix;

[0096] The stability evaluation module is configured to use the minimum eigenvalue of the solution matrix as a static voltage stability evaluation index and perform static voltage stability evaluation according to a range of the index value.

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention without creative labor shall be included in the protection scope of the present invention.

Claims

1. A method for evaluating static voltage stability of a multi-station grid-connected system, characterized in that: The following steps are involved: According to the multi-station grid-connected system model, a corresponding power flow equation group is established, and a Jacobian matrix is ​​written according to the power flow equation group; The Jacobian matrix is ​​transformed to obtain a transformation matrix, and the transformation matrix is ​​optimized, specifically: The Jacobian matrix is ​​constructed by calculating the values ​​of each element of the Jacobian matrix using equations (2) and (3). J , whose structure is shown in formula (1); （1） when When , the calculation method of the non-main diagonal elements of each matrix is ​​as follows: （2） In the formula, For Node i The active power, For Node i The reactive power, For Node i The voltage amplitude, For Node j The voltage amplitude, is the corresponding conductance value, is the corresponding susceptance value, For Node i, j The phase angle difference between when , the calculation method of the main diagonal elements of each matrix is ​​as follows: （3） Where n is the number of system nodes; Using a simple 3-node system, nodes 1 and 2 are PQ nodes on the station side, and node 3 is a balancing node on the infinite grid side. The resulting Jacobian matrix is: （4） Transform the Jacobian matrix to get the matrix A ,make: （5） After substituting the specific element values ​​of Jacobi in the example, the matrix A is obtained as follows: （6） The matrix A Re-block, get: （7） matrix and The non-main diagonal elements are relatively small and can be ignored, thus forming a diagonal matrix D , its specific elements are as follows: （8） P i Refers to the node i Active power of Take the average value of the elements at the corresponding positions of the main diagonal to form a new matrix C The corresponding elements in are calculated as shown in formula (9); （9） Keep Matrix and The non-main diagonal elements of remain unchanged, and the main diagonal elements are calculated by formula (9), thus forming a new matrix C : （10） Finally, the matrix A Approximately: （11）； According to the optimized conversion matrix, the critical condition of static voltage stability is converted into the minimum eigenvalue of the solution matrix; The minimum eigenvalue of the solution matrix is ​​used as a static voltage stability evaluation index, and static voltage stability evaluation is performed according to a range of the index value.

2. A method for evaluating static voltage stability of a multi-station grid-connected system as claimed in claim 1, characterized in that: According to the multi-station grid-connected system model, the process of establishing the corresponding power flow equation group includes: treating all new energy stations as PQ nodes, the external power grid is equivalent to an infinite power grid through the Thevenin method, regarded as a balance node, and constructing the power equation corresponding to the PQ node.

3. A method for evaluating static voltage stability of a multi-station grid-connected system as claimed in claim 1, characterized in that: The process of writing the Jacobian matrix according to the power flow equation group includes calculating the value of each element of the Jacobian matrix according to the power equation corresponding to the PQ node to form the Jacobian matrix.

4. A method for evaluating static voltage stability of a multi-station grid-connected system as claimed in claim 1, characterized in that: The process of converting the critical condition of static voltage stability into the minimum eigenvalue of the solution matrix includes: converting the static voltage stability evaluation into the solution matrix The minimum eigenvalue of ,make .

5. The method for evaluating static voltage stability of a multi-station grid-connected system according to claim 1, characterized in that: According to the range of index values, the process of static voltage stability assessment includes the following steps: , it indicates that the system static voltage is stable; if , it indicates that the system static voltage is unstable; When , it indicates that the system is in the critical state of static voltage stability.

6. A static voltage stability assessment system for a multi-station grid-connected system, characterized in that: include: A matrix writing module is configured to establish a corresponding power flow equation group according to a multi-station grid-connected system model, and write a Jacobian matrix according to the power flow equation group; The matrix conversion module is configured to convert the Jacobian matrix to obtain a conversion matrix and optimize the conversion matrix, specifically: The Jacobian matrix is ​​constructed by calculating the values ​​of each element of the Jacobian matrix using equations (2) and (3). J , whose structure is shown in formula (1); （1） when When , the calculation method of the non-main diagonal elements of each matrix is ​​as follows: （2） In the formula, For Node i The active power, For Node i The reactive power, For Node i The voltage amplitude, For Node j The voltage amplitude, is the corresponding conductance value, is the corresponding susceptance value, For Node i, j The phase angle difference between when , the calculation method of the main diagonal elements of each matrix is ​​as follows: （3） Where n is the number of system nodes; Using a simple 3-node system, nodes 1 and 2 are PQ nodes on the station side, and node 3 is a balancing node on the infinite grid side. The resulting Jacobian matrix is: （4） Transform the Jacobian matrix to get the matrix A ,make: （5） After substituting the specific element values ​​of Jacobi in the example, the matrix A is obtained as follows: （6） The matrix A Re-block, get: （7） matrix and The non-main diagonal elements are relatively small and can be ignored, thus forming a diagonal matrix D , its specific elements are as follows: （8） P i Refers to the node i Active power of Take the average value of the elements at the corresponding positions of the main diagonal to form a new matrix C The corresponding elements in are calculated as shown in formula (9); （9） Keep Matrix and The non-main diagonal elements of remain unchanged, and the main diagonal elements are calculated by formula (9), thus forming a new matrix C : （10） Finally, the matrix A Approximately: （11）； An indicator conversion module is configured to convert the static voltage stability critical condition according to the optimized conversion matrix and convert it into the minimum eigenvalue of the solution matrix; The stability evaluation module is configured to use the minimum eigenvalue of the solution matrix as a static voltage stability evaluation index and perform static voltage stability evaluation according to a range of the index value.

7. A computer-readable storage medium, characterized in that: Used to store computer instructions, which, when executed by a processor, complete the steps of a method for evaluating static voltage stability of a multi-station grid-connected system according to any one of claims 1-5.

8. An electronic device, characterized in that: The method comprises a memory and a processor and computer instructions stored in the memory and executed on the processor. When the computer instructions are executed by the processor, the steps in the static voltage stability assessment method for a multi-station grid-connected system described in any one of claims 1 to 5 are completed.

Images