DC parameter calculation method, device and storage medium for multi-terminal DC power transmission system

Abstract

The present application discloses a method and device for calculating DC parameters of a multi-terminal DC power transmission system, a storage medium, and a computer device. The method includes: determining the operation connection mode and DC resistance level of the multi-terminal DC power transmission system, and obtaining the DC line resistance column vector of the multi-terminal DC power transmission system according to the operation connection mode and DC resistance level; generating a target node admittance matrix based on the DC line resistance column vector; generating a node voltage equation according to the target node admittance matrix; obtaining a control equation based on the control mode and control reference value of each converter station in the multi-terminal DC power transmission system; and solving the DC voltage and DC current corresponding to each converter station in the multi-terminal DC power transmission system according to the node voltage equation and the control equation. The present application can be applied to multi-terminal DC power transmission systems of different types, different topological structures, different control modes, and different operation modes, and has general applicability.

Description

Technical Field

[0001] The present application relates to the technical field of DC power transmission, and in particular, to a method and device for calculating DC parameters of a multi-terminal DC power transmission system, a storage medium, and a computer device. Background Technique

[0002] Multi-terminal DC power transmission systems have received extensive attention due to their advantages in long-distance large-capacity power transmission, renewable energy grid connection, AC grid interconnection, etc. DC parameter calculation is a basic link in the complete set design of multi-terminal DC power transmission systems and is the basis for system operation and control settings. Compared with two-terminal DC power transmission systems, the control strategies and DC network topologies of multi-terminal DC power transmission systems are more complex.

[0003] Currently, there is relatively little research on the calculation of DC parameters of multi-terminal DC power transmission systems. The existing calculation methods mainly target multi-terminal conventional DC power transmission systems, while multi-terminal flexible DC power transmission systems and multi-terminal hybrid DC power transmission systems are rarely mentioned. The existing calculation methods cannot be applied to different topologies, different control strategies, and different operation modes of multi-terminal DC power transmission systems, and it is difficult to be extended to more terminals and more complex DC networks. Summary of the Invention

[0004] In view of this, the present application provides a method and device for calculating DC parameters of a multi-terminal DC power transmission system, a storage medium, and a computer device, which can be applied to multi-terminal DC power transmission systems of different types, different topologies, different control methods, and different operation modes, and has general applicability.

[0005] According to one aspect of the present application, a method for calculating DC parameters of a multi-terminal DC power transmission system is provided, including:

[0006] Determine the operation connection mode and DC resistance level of the multi-terminal DC power transmission system, and obtain the DC line resistance column vector of the multi-terminal DC power transmission system according to the operation connection mode and the DC resistance level, where the dimension of the DC line resistance column vector is the same as the number of DC transmission lines included in the multi-terminal DC power transmission system;

[0007] Generate a target node admittance matrix based on the DC line resistance column vector, where the number of rows and columns of the target node admittance matrix is the same as the number of converter stations included in the multi-terminal DC power transmission system;

[0008] Generate a node voltage equation according to the target node admittance matrix, where the number of node voltage equations is the same as the number of converter stations included in the multi-terminal DC power transmission system;

[0009] Based on the control modes and control reference values of each converter station in the multi-terminal DC power transmission system, control equations are obtained, where the number of the control equations is the same as the number of converter stations included in the multi-terminal DC power transmission system;

[0010] According to the node voltage equation and the control equations, the DC voltages and DC currents corresponding to each converter station in the multi-terminal DC power transmission system are solved.

[0011] According to another aspect of the present application, there is provided a device for calculating DC parameters of a multi-terminal DC power transmission system, including:

[0012] A first determination module, configured to determine the operation connection mode and DC resistance level of the multi-terminal DC power transmission system, and obtain a DC line resistance column vector of the multi-terminal DC power transmission system according to the operation connection mode and the DC resistance level, where the dimension of the DC line resistance column vector is the same as the number of DC transmission lines included in the multi-terminal DC power transmission system;

[0013] A first generation module, configured to generate a target node admittance matrix based on the DC line resistance column vector, where the number of rows and columns of the target node admittance matrix is the same as the number of converter stations included in the multi-terminal DC power transmission system;

[0014] A second generation module, configured to generate a node voltage equation according to the target node admittance matrix, where the number of the node voltage equations is the same as the number of converter stations included in the multi-terminal DC power transmission system;

[0015] A second determination module, configured to obtain control equations based on the control modes and control reference values of each converter station in the multi-terminal DC power transmission system, where the number of the control equations is the same as the number of converter stations included in the multi-terminal DC power transmission system;

[0016] A calculation module, configured to solve the DC voltages and DC currents corresponding to each converter station in the multi-terminal DC power transmission system according to the node voltage equation and the control equations.

[0017] According to yet another aspect of the present application, there is provided a storage medium, on which a computer program is stored, and when the program is executed by a processor, the DC parameter calculation method of the above multi-terminal DC power transmission system is implemented.

[0018] According to still another aspect of the present application, there is provided a computer device, including a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, and when the processor executes the program, the DC parameter calculation method of the above multi-terminal DC power transmission system is implemented.

[0019] With the above technical solutions, a method and device for calculating DC parameters of a multi-terminal DC power transmission system, a storage medium, and a computer device provided by this application can, first, determine the operating connection mode and DC resistance level of the multi-terminal DC power transmission system, and can obtain the DC line resistance column vector of the multi-terminal DC power transmission system according to the operating connection mode and the DC resistance level. Next, the target node admittance matrix can be generated by using the DC line resistance column vector. After obtaining the target node admittance matrix, the node voltage equation can be generated by using the target node admittance matrix. In addition, the control mode and control reference value of each converter station in the multi-terminal DC power transmission system can be determined, and the control equation can be obtained according to the control mode and the control reference value. Finally, the DC voltage and DC current of each converter station in the multi-terminal DC power transmission system can be jointly solved according to the node voltage equation and the control equation. The method for calculating DC parameters of the multi-terminal DC power transmission system provided by the embodiments of this application can be applied to multi-terminal DC power transmission systems of different types, different topological structures, different control modes, and different operating modes, and has universal applicability.

[0020] The above description is only an overview of the technical solutions of this application. In order to be able to understand the technical means of this application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features, and advantages of this application more obvious and understandable, the specific embodiments of this application are specifically given below. Brief Description of the Drawings

[0021] The drawings described herein are used to provide a further understanding of this application, and constitute a part of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation of this application. In the drawings:

[0022] Figure 1 A flowchart showing a method for calculating DC parameters of a multi-terminal DC power transmission system provided by an embodiment of this application is shown;

[0023] Figure 2 A schematic diagram showing the composition of a multi-terminal DC power transmission system provided by an embodiment of this application is shown;

[0024] Figure 3 A flowchart showing another method for calculating DC parameters of a multi-terminal DC power transmission system provided by an embodiment of this application is shown;

[0025] Figure 4 A schematic diagram showing the structure of a device for calculating DC parameters of a multi-terminal DC power transmission system provided by an embodiment of this application is shown;

[0026] Figure 5 A schematic diagram showing the device structure of a computer device provided by an embodiment of this application is shown. Detailed Description of the Embodiments

[0027] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0028] In this embodiment, a method for calculating DC parameters of a multi-terminal DC power transmission system is provided. As Figure 1 shown, the method includes:

[0029] Step 101: Determine the operating connection mode and DC resistance level of the multi-terminal DC power transmission system, and obtain the DC line resistance column vector of the multi-terminal DC power transmission system according to the operating connection mode and the DC resistance level, where the dimension of the DC line resistance column vector is consistent with the number of DC transmission lines included in the multi-terminal DC power transmission system;

[0030] The calculation of DC parameters of a multi-terminal DC power transmission system is the basis and an important part of the steady-state operating parameters of the main circuit. After calculating the DC voltages and DC currents of each converter station, these DC voltages and DC currents are respectively provided to each converter station for subsequent calculation of the steady-state operating parameters of the converter station. The multi-terminal DC power transmission system in the embodiments of the present application may include three or more converter stations, where there may be LCC converter stations and / or MMC converter stations. The method for calculating DC parameters of the multi-terminal DC power transmission system provided in the embodiments of the present application can be applied to multi-terminal DC power transmission systems of different types, different topological structures, different control modes, and different operating modes, and has general applicability. Among them, the types of multi-terminal DC power transmission systems may include multi-terminal conventional DC power transmission systems based on LCC, multi-terminal flexible DC power transmission systems based on MMC, and multi-terminal hybrid DC power transmission systems; the multi-terminal DC power transmission system may include multiple converter stations and multiple DC transmission lines, and any two converter stations can be connected by a DC transmission line to form different topological structures.

[0031] First, the operating connection mode and DC resistance level of the multi-terminal DC power transmission system can be determined. Among them, for the current multi-terminal DC power transmission system, the operating connection mode may include bipolar operation, single-pole metal return line operation, single-pole ground return line operation, etc., and the DC resistance level may include rated, high resistance, low resistance, etc. Different combinations of operating connection modes and DC resistance levels may correspond to different DC line resistance column vectors. Then, the DC line resistance column vector of the multi-terminal DC power transmission system can be obtained according to the operating connection mode and the DC resistance level. Specifically, the dimension of the DC line resistance column vector is consistent with the number of DC transmission lines in the multi-terminal DC power transmission system. For example, as Figure 2As shown in the figure, the multi-terminal DC power transmission system includes n converter stations, where the first to the l-th converter stations are LCC converter stations, and the (l + 1)-th to the n-th converter stations are MMC converter stations. Different converter stations in the system can be represented in the form of LCC or MMC with subscripts, such as LCC 1 . The two return lines of the DC power transmission line between two converter stations can be equivalent to one line in the above figure. Any two converter stations in the figure can be connected by a DC power transmission line. Assuming there are m DC power transmission lines among these n converter stations, the dimension of the obtained DC line resistance column vector is also m, that is, the DC line resistance column vector includes m constituent elements in total.

[0032] Step 102: Generate a target nodal admittance matrix based on the DC line resistance column vector, where the number of rows and columns of the target nodal admittance matrix is the same as the number of converter stations included in the multi-terminal DC power transmission system;

[0033] In this embodiment, then, a target nodal admittance matrix can be generated using the DC line resistance column vector. Specifically, a nodal admittance matrix can be initialized, and each element in the initialized nodal admittance matrix can be 0. Then, according to the elements in the DC line resistance column vector, the elements in the nodal admittance matrix are updated and replaced, and thus the target nodal admittance matrix can be obtained. Here, the target nodal admittance matrix can be a square matrix, where the number of rows and columns is the same as the number of converter stations included in the multi-terminal DC power transmission system. For example, if there are n converter stations in the multi-terminal DC power transmission system, then the target nodal admittance matrix is an n-order matrix.

[0034] Step 103: Generate nodal voltage equations according to the target nodal admittance matrix, where the number of nodal voltage equations is the same as the number of converter stations included in the multi-terminal DC power transmission system;

[0035] In this embodiment, after obtaining the target nodal admittance matrix, nodal voltage equations can be generated using the target nodal admittance matrix. Assuming the target nodal admittance matrix is represented by Y, then the generated nodal voltage equations can be expressed as YU = I, where U = [U 1 , U 2 ... U n T is the DC voltage of each converter station and the grounding electrode resistance (if any) in the multi-terminal DC power transmission system; I = [I 1 , I 2 ... I n T ​​The DC current injected into each node represents the DC current of each converter station. The current injected into the DC bus node of the rectifier station is positive, and the current injected into the DC bus node of the inverter station is negative. If the admittance matrix of the target node is an n-order matrix, the generated node voltage equation can be an n-order equation, that is, the node voltage equation includes n equations.

[0036] Step 104: Obtain control equations based on the control mode and control reference value of each converter station in the multi-terminal DC power transmission system, where the number of the control equations is the same as the number of converter stations included in the multi-terminal DC power transmission system.

[0037] In this embodiment, since the above node voltage equation only includes n equations, and the unknowns to be solved include n DC voltage unknowns and n DC current unknowns, that is, a total of 2n unknowns, n additional control equations can be added, and then these 2n unknowns can be solved. The following method can be used to add control equations: Determine the control mode and control reference value of each converter station in the multi-terminal DC power transmission system, and obtain the control equations according to the control mode and control reference value. For example, if the control mode of the converter station in the multi-terminal DC power transmission system is constant current control, then the DC current reference value corresponding to each converter station can be obtained at this time, that is, the above control reference value. After that, taking these DC current reference values as known values, the DC voltage of each converter station can be calculated. Assume the DC current reference value is I dcref , then the added control equation can be expressed as I = I dcref .

[0038] Step 105: Solve the DC voltage and DC current corresponding to each converter station in the multi-terminal DC power transmission system according to the node voltage equation and the control equation.

[0039] In this embodiment, finally, the DC voltage and DC current of each converter station in the multi-terminal DC power transmission system can be jointly solved by using the Newton method according to the node voltage equation and the control equation.

[0040] By applying the technical solution of this embodiment, first, the operating connection mode and the DC resistance level of the multi-terminal DC transmission system can be determined, and according to the operating connection mode and the DC resistance level, the DC line resistance column vector of the multi-terminal DC transmission system can be obtained. Then, the target node admittance matrix can be generated by using the DC line resistance column vector. After obtaining the target node admittance matrix, the node voltage equation can be generated by using the target node admittance matrix. In addition, the control mode and the control reference value of each converter station in the multi-terminal DC transmission system can be determined, and the control equation can be obtained according to the control mode and the control reference value. Finally, the DC voltage and DC current of each converter station in the multi-terminal DC transmission system can be jointly solved according to the node voltage equation and the control equation. The DC parameter calculation method for the multi-terminal DC transmission system provided by the embodiments of the present application can be applied to multi-terminal DC transmission systems of different types, different topological structures, different control modes, and different operating modes, and has general applicability.

[0041] Further, as a refinement and extension of the specific implementation manner of the above embodiment, in order to completely illustrate the specific implementation process of this embodiment, another DC parameter calculation method for the multi-terminal DC transmission system is provided, as Figure 3 shown, the method includes:

[0042] Step 201, determine the operating connection mode and the DC resistance level of the multi-terminal DC transmission system, and according to the operating connection mode and the DC resistance level, obtain the DC line resistance column vector of the multi-terminal DC transmission system, where the dimension of the DC line resistance column vector is the same as the number of DC transmission lines included in the multi-terminal DC transmission system;

[0043] Step 202, generate a target node admittance matrix based on the DC line resistance column vector, where the number of rows and columns of the target node admittance matrix is the same as the number of converter stations included in the multi-terminal DC transmission system;

[0044] In the embodiments of the present application, optionally, step 202 includes:

[0045] Step 202-1, identify any DC transmission line in the multi-terminal DC transmission system, and determine the two converter station identifiers corresponding to the any DC transmission line;

[0046] Step 202-2, based on the DC transmission line identifier corresponding to the any DC transmission line, look up the DC line resistance corresponding to the DC transmission line identifier in the DC line resistance column vector;

[0047] Step 202-3: According to each converter station identifier, respectively determine the first position to be updated and the second position to be updated in the initial nodal admittance matrix, and update the elements at the first position to be updated and the elements at the second position to be updated based on the DC line resistance, where the first position to be updated and the second position to be updated are the diagonal positions of the initial nodal admittance matrix; and, according to the two converter station identifiers, determine the third position to be updated and the fourth position to be updated in the initial nodal admittance matrix, and update the elements at the third position to be updated and the elements at the fourth position to be updated based on the DC line resistance, where the third position to be updated and the fourth position to be updated are the non-diagonal positions of the initial nodal admittance matrix.

[0048] In this embodiment, the multi-terminal DC power transmission system may include multiple DC power transmission lines, and each DC power transmission line is composed of two connected converter stations. When generating the target nodal admittance matrix based on the DC line resistance column vector, the following operations can be performed on each DC power transmission line:

[0049] On the one hand, the elements on the diagonal of the initial nodal admittance matrix can be updated according to this DC power transmission line. Specifically, first, determine the converter station identifiers of the two converter stations corresponding to this DC power transmission line. Then, the DC line resistance corresponding to this DC power transmission line identifier can be found from the DC line resistance column vector according to the DC power transmission line identifier corresponding to this DC power transmission line. At the same time, according to the converter station identifiers of the two converter stations corresponding to this DC power transmission line, the first position to be updated and the second position to be updated can be respectively determined in the initial nodal admittance matrix, and each converter station identifier can determine a position to be updated. After that, based on the DC line resistance, the elements at the first position to be updated and the elements at the second position to be updated can be updated respectively. Here, both the first position to be updated and the second position to be updated are the diagonal positions of the initial nodal admittance matrix.

[0050] For example, assume that there are m DC transmission lines in a multi-terminal DC transmission system. These m DC transmission lines are numbered, and the numbers can range from 1 to m. The DC transmission line identifier can also be the corresponding number of the DC transmission line. Assume that the DC transmission line identifier of the k-th DC transmission line is Line k, the converter station identifier at one end is Converter Station i, and the converter station identifier at the other end is Converter Station j. According to Line k, the DC line resistance corresponding to Line k can be found from the DC line resistance column vector. Specifically, the k-th element can be found from the DC line resistance column vector, and this element is also the DC line resistance of the k-th DC transmission line. In addition, the position of the i-th row and i-th column in the initial nodal admittance matrix is taken as the first position to be updated, and the position of the j-th row and j-th column is taken as the second position to be updated. Assume that the initial nodal admittance matrix is A, then the first position to be updated is A(i, i), and the second position to be updated is A(j, j). After that, the elements at these two positions can be updated using the DC line resistance. The update formulas can be as shown in Equations (1) and (2):

[0051]

[0052]

[0053] where R d (k,:) is the DC line resistance of the k-th DC transmission line. It should be noted that each converter station may correspond to multiple DC transmission lines. When the number of DC transmission lines corresponding to any converter station is more than one, the positions to be updated corresponding to this converter station in the initial nodal admittance matrix can be updated multiple times, and the number of updates is the same as the number of corresponding DC transmission lines.

[0054] For example, Converter Station i corresponds to a total of 2 DC transmission lines, namely Line k and Line c. Then the positions to be updated corresponding to this converter station are updated twice, and the update formulas can be as shown in Equations (3) and (4):

[0055] First update:

[0056] Second update:

[0057] On the other hand, the elements on the non-diagonal of the initial nodal admittance matrix can also be updated according to this DC transmission line. Specifically, according to the converter station identifiers of the two converter stations corresponding to this DC transmission line, the third position to be updated and the fourth position to be updated can be determined from the initial nodal admittance matrix, and the determined DC line resistance is used to update the elements at the third position to be updated and the elements at the fourth position to be updated. Here, both the third position to be updated and the fourth position to be updated are positions on the non-diagonal of the initial nodal admittance matrix.

[0058] For example, the converter station identifiers of the two converter stations corresponding to line k are converter station i and converter station j respectively. The position of the i-th row and j-th column in the initial nodal admittance matrix is used as the third position to be updated, and the position of the j-th row and i-th column is used as the fourth position to be updated. Assuming the initial nodal admittance matrix is A, then the third position to be updated is A(i, j), and the fourth position to be updated is A(j, i). Subsequently, the elements at these two positions can be updated respectively using the DC line resistance. The update formulas can be as shown in Equations (5) and (6):

[0059]

[0060]

[0061] where R d (k,:) is the DC line resistance of the k-th DC transmission line. The element at each non-diagonal position is updated only once.

[0062] After each DC transmission line in the multi-terminal DC transmission system has been identified, that is, after the above two operations have been performed on each line, the initial nodal admittance matrix is updated, and then the n-order target nodal admittance matrix Y is obtained accordingly.

[0063] Step 203: Generate nodal voltage equations according to the target nodal admittance matrix, where the number of the nodal voltage equations is the same as the number of converter stations included in the multi-terminal DC transmission system;

[0064] Step 204: Obtain control equations based on the control mode and control reference value of each converter station in the multi-terminal DC transmission system, where the number of the control equations is the same as the number of converter stations included in the multi-terminal DC transmission system;

[0065] In an embodiment of the present application, optionally, the control mode includes constant current control, constant voltage control, and constant DC power control; Step 204 includes:

[0066] When the control mode is constant current control, obtain the DC current reference value of each converter station in the multi-terminal DC transmission system, and obtain the control equations based on the DC current reference value;

[0067] When the control mode is constant voltage control, according to the operating connection mode and the DC resistance level, obtain the column vector of the grounding electrode resistance of the multi-terminal DC transmission system, and obtain the DC voltage reference value of each converter station in the multi-terminal DC transmission system. Based on the DC voltage reference value and the column vector of the grounding electrode resistance, obtain the control equation, where the dimension of the column vector of the grounding electrode resistance is the same as the number of converter stations included in the multi-terminal DC transmission system;

[0068] When the control mode is constant DC power control, according to the operating connection mode and the DC resistance level, obtain the column vector of the grounding electrode resistance of the multi-terminal DC transmission system, and obtain the DC power reference value of each converter station in the multi-terminal DC transmission system. Based on the DC power reference value and the column vector of the grounding electrode resistance, obtain the control equation.

[0069] In this embodiment, the control modes of the multi-terminal DC transmission system may specifically include three types: constant current control, constant voltage control, and constant DC power control.

[0070] If the control mode of the multi-terminal DC transmission system is constant current control, then at this time, the DC current reference value of each converter station can be obtained, and then the control equation is generated according to these DC current reference values. The form of the control equation can be as shown in Equation (7):

[0071] I i =I dcref (7)

[0072] Where, I dcref is the DC current reference value of the converter station, which is the expected DC current value during the operation of the converter station and can be set artificially; I i is the DC current of converter station i. When the number of converter stations is n, i = 1 to n.

[0073] If the control mode of the multi-terminal DC transmission system is constant voltage control, then at this time, according to the operating connection mode and the DC resistance level of the multi-terminal DC transmission system, the column vector of the grounding electrode resistance of the multi-terminal DC transmission system can be obtained. It should be noted that different combinations of the operating connection mode and the DC resistance level may correspond to different column vectors of the grounding electrode resistance. Then, the DC voltage reference value of each converter station in the multi-terminal DC transmission system can be obtained, and the control equation is obtained according to the DC voltage reference value and the column vector of the grounding electrode resistance. Here, the dimension of the column vector of the grounding electrode resistance is the same as the number of converter stations included in the multi-terminal DC transmission system. The form of the control equation is as shown in Equation (8):

[0074] U i =U dcref -I i Rgi (8)

[0075] Among them, U dcref is the DC voltage reference value of the converter station, which is the expected DC voltage during the operation of the converter station and can be set artificially; I i is the DC current of converter station i, and U i is the DC voltage of converter station i, and R gi is the grounding electrode resistance of converter station i, which can be determined according to the grounding electrode resistance column vector. When the number of converter stations is n, i = 1 to n.

[0076] If the control mode of the multi-terminal DC power transmission system is constant DC power control, then at this time, the grounding electrode resistance column vector of the multi-terminal DC power transmission system can also be obtained according to the operation connection mode and the DC resistance level of the multi-terminal DC power transmission system. Then, the DC power reference value of each converter station in the multi-terminal DC power transmission system can be obtained, and according to the DC power reference value and the grounding electrode resistance column vector, the control equation can be obtained. The form of the control equation is as shown in Equation (9):

[0077] (U i +I i R gi )I i =P dcref (9)

[0078] Among them, P dcref is the DC power reference value of the converter station, which is the expected DC power during the operation of the converter station and can be set artificially; I i is the DC current of converter station i, and U i is the DC voltage of converter station i, and R gi is the grounding electrode resistance of converter station i, which can be determined according to the grounding electrode resistance column vector. When the number of converter stations is n, i = 1 to n.

[0079] In an embodiment of the present application, optionally, the "obtaining the DC line resistance column vector of the multi-terminal DC power transmission system according to the operation connection mode and the DC resistance level" includes: determining a first calculation formula for the DC line resistance column vector according to the operation connection mode and the DC resistance level, and determining the DC line resistance column vector according to the first calculation formula; the "obtaining the grounding electrode resistance column vector of the multi-terminal DC power transmission system according to the operation connection mode and the DC resistance level" includes: determining a second calculation formula for the grounding electrode resistance column vector according to the operation connection mode and the DC resistance level, and determining the grounding electrode resistance column vector according to the second calculation formula.

[0080] In this embodiment, different calculation formulas can be preset for the DC line resistance column vector and the grounding electrode resistance column vector according to different operation connection modes and DC resistance levels. Then, the DC line resistance column vector and the grounding electrode resistance column vector can be calculated respectively according to the corresponding calculation formulas. Specifically, the preset formulas are shown in the following table:

[0081] Table 1 Calculation Formulas for DC Line Resistance Column Vector and Grounding Electrode Resistance Column Vector

[0082]

[0083] where, R d is the DC line resistance column vector, and R g is the grounding electrode resistance column vector. R dN , R dmax , R dmin are three m (m is the number of DC transmission lines) - dimensional column vectors corresponding to the rated DC resistance, maximum DC resistance, and minimum DC resistance of each DC transmission line numbered in sequence, and the rated DC resistance, maximum DC resistance, and minimum DC resistance are all known. R gN , R lN , R lmax , R lmin are four n (n is the number of converter stations) - dimensional column vectors corresponding to the grounding resistance, rated value of grounding electrode lead resistance, maximum value of grounding electrode lead resistance, and minimum value of grounding electrode lead resistance of each converter station numbered in sequence, and the grounding resistance, rated value of grounding electrode lead resistance, maximum value of grounding electrode lead resistance, and minimum value of grounding electrode lead resistance are all known.

[0084] Here, R dN , R dmax , R dmin , R gN , R lN , R lmax , R lmin can all be determined in advance. Then, according to the operation connection mode and DC resistance level, the first calculation formula for the DC line resistance column vector and the second calculation formula for the grounding electrode resistance column vector are further determined from Table 1; it is also possible to first determine the calculation formula according to Table 1, and then determine R dN , R dmax , R dmin , R gN , R lN , R lmax , R lmin as required by the calculation formula.

[0085] In an embodiment of the present application, optionally, when the operating connection mode is bipolar operation or monopolar metal return operation, each element in the column vector of the grounding electrode resistance is zero; correspondingly, when the control mode is constant voltage control, the DC voltage reference value of each converter station in the multi-terminal DC power transmission system is obtained, and based on the DC voltage reference value, the control equation is obtained; when the control mode is constant DC power control, the DC power reference value of each converter station in the multi-terminal DC power transmission system is obtained, and based on the DC power reference value, the control equation is obtained.

[0086] In this embodiment, the operating connection mode may include bipolar operation, monopolar metal return operation, and monopolar ground return operation. For bipolar operation and monopolar metal return operation, no DC current passes through the grounding electrode, so the influence of the grounding electrode resistance is not considered, and R g can be equivalently regarded as a zero vector. At this time, the node voltage is the DC voltage of the converter station, so equations (8) and (9) can be simplified as:

[0087] U i = U dcref (10)

[0088] U i I i = P dcref (11)

[0089] Step 205: Solve the DC voltage and DC current corresponding to each converter station in the multi-terminal DC power transmission system according to the node voltage equation and the control equation;

[0090] Step 206: Record the DC voltage and DC current corresponding to each converter station, and monitor the operating conditions of each converter station;

[0091] In this embodiment, after obtaining the DC voltage and DC current of each converter station, further, these DC voltages and DC currents can be recorded. Specifically, when recording, a mapping relationship can be established between the DC voltage and DC current of each converter station and the identifier of the converter station, so that it can be known which converter station each DC voltage belongs to and which converter station each DC current belongs to. After that, the operating conditions of each converter station can also be monitored in real time.

[0092] Step 207: When it is monitored that the operating voltage of any converter station exceeds the allowable fluctuation range of the DC voltage and / or the operating current exceeds the allowable fluctuation range of the DC current, an abnormal reminder is output.

[0093] In this embodiment, if during the monitoring process, it is found that the actual operating voltage of a certain converter station is greater than the allowable fluctuation range of the DC voltage calculated for this converter station, or the actual operating current of a certain converter station is greater than the allowable fluctuation range of the DC current calculated for this converter station, it indicates that the operating condition of this converter station is abnormal at this time. Therefore, an abnormality reminder can be output. By recording the calculated DC voltage and DC current of each converter station and monitoring the operating condition of the converter station, and giving a reminder in case of abnormality, the safe and stable operation of the converter station can be guaranteed to a certain extent.

[0094] In the embodiment of the present application, optionally, when the DC voltage of any one of the converter stations included in the multi-terminal DC power transmission system is known, and the DC currents of the remaining converter stations except the any one converter station are known, after step 203, the method further includes:

[0095] Determine the converter station identifier of the any one converter station, and remove the row elements and column elements corresponding to the converter station identifier of the any one converter station from the target node admittance matrix to obtain an updated target node admittance matrix;

[0096] Perform an inverse transformation process on the updated target node admittance matrix to obtain a node impedance matrix;

[0097] According to Kirchhoff's current law, use the DC currents of the remaining converter stations except the any one converter station to calculate the DC current of the any one converter station;

[0098] According to the operating connection mode and the DC resistance level, obtain the grounding electrode resistance column vector of the multi-terminal DC power transmission system;

[0099] According to the node impedance matrix, the grounding electrode resistance column vector, the DC voltage of the any one converter station, and the DC currents of the remaining converter stations, calculate the DC voltages of the remaining converter stations.

[0100] In this embodiment, assume that the column vector representing the DC voltages of each converter station is U dc =[U dc1 ,U dc2 ……U dcn T , where the DC voltage of converter station i is known, and the DC currents of the remaining n - 1 converter stations are known. Then, the following method can be used to solve the DC current of converter station i and the DC voltages of the remaining n - 1 converter stations:

[0101] First, based on the n - order target node admittance matrix Y of the multi-terminal DC power transmission system, remove the i-th row and the i-th column to obtain an updated (n - 1)-order target node admittance matrix. ​

[0102] Next, perform an inverse transformation on the updated target node admittance matrix of order n - 1 to obtain the node impedance matrix Z.

[0103] After that, according to Kirchhoff's current law, calculate the DC current I of converter station i by using the DC currents of the remaining n - 1 converter stations. i .

[0104] Finally, according to the node impedance matrix Z, the column vector R of grounding electrode resistances g , the DC voltage U of converter station i dci , and the DC currents I of the remaining n - 1 converter stations 1 ~I n , calculate the DC voltages U of the remaining n - 1 converter stations dc1 ~U dc(i-1) , U dc(i+1) ~U dcn , as shown in Equation (12).

[0105]

[0106] Furthermore, as a Figure 1 specific implementation of the method, an embodiment of the present application provides a DC parameter calculation device for a multi - terminal DC power transmission system, as Figure 4 shown, the device includes:

[0107] A first determination module, configured to determine the operation connection mode and the DC resistance level of the multi - terminal DC power transmission system, and obtain the column vector of DC line resistances of the multi - terminal DC power transmission system according to the operation connection mode and the DC resistance level, wherein the dimension of the column vector of DC line resistances is consistent with the number of DC transmission lines included in the multi - terminal DC power transmission system;

[0108] A first generation module, configured to generate a target node admittance matrix based on the column vector of DC line resistances, wherein the number of rows and columns of the target node admittance matrix is both consistent with the number of converter stations included in the multi - terminal DC power transmission system;

[0109] A second generation module, configured to generate a node voltage equation according to the target node admittance matrix, wherein the number of node voltage equations is consistent with the number of converter stations included in the multi - terminal DC power transmission system;

[0110] A second determination module, configured to obtain a control equation based on the control mode and the control reference value of each converter station in the multi - terminal DC power transmission system, wherein the number of control equations is consistent with the number of converter stations included in the multi - terminal DC power transmission system;

[0111] A calculation module, configured to solve for the DC voltage and DC current corresponding to each converter station in the multi-terminal DC power transmission system according to the node voltage equation and the control equation.

[0112] Optionally, the first generation module is configured to:

[0113] Identify any DC transmission line in the multi-terminal DC power transmission system, and determine the two converter station identifiers corresponding to the DC transmission line;

[0114] Based on the DC transmission line identifier corresponding to the DC transmission line, look up the DC line resistance corresponding to the DC transmission line identifier from the DC line resistance column vector;

[0115] According to each converter station identifier, respectively determine a first position to be updated and a second position to be updated in the initial node admittance matrix, and update the elements at the first position to be updated and the elements at the second position to be updated based on the DC line resistance, where the first position to be updated and the second position to be updated are diagonal positions of the initial node admittance matrix; and,

[0116] According to the two converter station identifiers, determine a third position to be updated and a fourth position to be updated in the initial node admittance matrix, and update the elements at the third position to be updated and the elements at the fourth position to be updated based on the DC line resistance, where the third position to be updated and the fourth position to be updated are non-diagonal positions of the initial node admittance matrix.

[0117] Optionally, the control mode includes constant current control, constant voltage control, and constant DC power control; the second determination module is configured to:

[0118] When the control mode is constant current control, obtain the DC current reference value of each converter station in the multi-terminal DC power transmission system, and based on the DC current reference value, obtain the control equation;

[0119] When the control mode is constant voltage control, obtain the grounding electrode resistance column vector of the multi-terminal DC power transmission system according to the operation connection mode and the DC resistance level, and obtain the DC voltage reference value of each converter station in the multi-terminal DC power transmission system. Based on the DC voltage reference value and the grounding electrode resistance column vector, obtain the control equation, where the dimension of the grounding electrode resistance column vector is the same as the number of converter stations included in the multi-terminal DC power transmission system;

[0120] When the control mode is constant DC power control, according to the operation connection mode and the DC resistance level, obtain the column vector of the grounding electrode resistance of the multi-terminal DC power transmission system, and obtain the DC power reference value of each converter station in the multi-terminal DC power transmission system. Based on the DC power reference value and the column vector of the grounding electrode resistance, obtain the control equation.

[0121] Optionally, the first determination module is configured to:

[0122] Determine the first calculation formula of the DC line resistance column vector according to the operation connection mode and the DC resistance level, and determine the DC line resistance column vector according to the first calculation formula;

[0123] The second determination module is further configured to:

[0124] Determine the second calculation formula of the grounding electrode resistance column vector according to the operation connection mode and the DC resistance level, and determine the grounding electrode resistance column vector according to the second calculation formula.

[0125] Optionally, when the operation connection mode is bipolar operation or single-stage metal return line operation, each element in the column vector of the grounding electrode resistance is zero;

[0126] Correspondingly, the second determination module is further configured to:

[0127] When the control mode is constant voltage control, obtain the DC voltage reference value of each converter station in the multi-terminal DC power transmission system, and based on the DC voltage reference value, obtain the control equation;

[0128] When the control mode is constant DC power control, obtain the DC power reference value of each converter station in the multi-terminal DC power transmission system, and based on the DC power reference value, obtain the control equation.

[0129] Optionally, when in the multi-terminal DC power transmission system, the DC voltage of any one converter station is known, and the DC currents of the remaining converter stations except the any one converter station are known, the device further includes:

[0130] A matrix update module, configured to, after generating the nodal voltage equation, determine the converter station identifier of the any one converter station, and remove the row elements and column elements corresponding to the converter station identifier of the any one converter station from the target nodal admittance matrix to obtain an updated target nodal admittance matrix;

[0131] An inverse transformation module, configured to perform an inverse transformation process on the updated target nodal admittance matrix to obtain a nodal impedance matrix;

[0132] A current calculation module, configured to calculate the DC current of any one of the converter stations according to Kirchhoff's current law by using the DC currents of the remaining converter stations except the said any one converter station;

[0133] The second determination module is further configured to obtain a column vector of grounding resistance of the multi-terminal HVDC transmission system according to the operation connection mode and the DC resistance level;

[0134] A voltage calculation module, configured to calculate the DC voltages of the remaining converter stations according to the node impedance matrix, the column vector of grounding resistance, the DC voltage of any one of the converter stations, and the DC currents of the remaining converter stations.

[0135] Optionally, the device further includes:

[0136] A recording module, configured to record the DC voltage and DC current corresponding to each converter station after solving the DC voltage and DC current corresponding to each converter station in the multi-terminal HVDC transmission system, and monitor the operation conditions of each converter station;

[0137] A reminder module, configured to output an abnormality reminder when it is monitored that the operating voltage of any one of the converter stations exceeds the allowable fluctuation range of the DC voltage and / or the operating current exceeds the allowable fluctuation range of the DC current.

[0138] It should be noted that for other corresponding descriptions of each functional unit involved in the DC parameter calculation device of the multi-terminal HVDC transmission system provided in the embodiments of the present application, reference can be made to Figures 1 to 3 the corresponding descriptions in the method, which will not be elaborated here.

[0139] Embodiments of the present application further provide a computer device, specifically a personal computer, a server, a network device, etc. As Figure 5 shown, the computer device includes a bus, a processor, a memory, and a communication interface, and may further include an input / output interface and a display device. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store location information. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, the steps in the method embodiments are implemented.

[0140] Those skilled in the art can understand, Figure 5The structure shown is only a block diagram of some structures related to the solution of this application, and does not constitute a limitation on the computer device to which the solution of this application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

[0141] In one embodiment, a computer-readable storage medium is provided. The computer-readable storage medium may be non-volatile or volatile, and has a computer program stored thereon. When the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0142] In one embodiment, a computer program product is provided, including a computer program. When the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0143] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0144] 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 completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, database, or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memories. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The databases involved in the embodiments provided in the present application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., without limitation. The processors involved in the embodiments provided in the present application can be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, data processing logics based on quantum computing, etc., without limitation.

[0145] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0146] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A method for calculating direct current parameters of a multi-terminal direct current transmission system, characterized in that: include: Determine an operation wiring mode and a DC resistance level of a multi-terminal DC power transmission system, and obtain a DC line resistance column vector of the multi-terminal DC power transmission system according to the operation wiring mode, the DC resistance level, and three m-dimensional column vectors corresponding to a DC resistance rated value, a DC resistance maximum value, and a DC resistance minimum value of each DC power transmission line numbered in sequence, wherein the dimension of the DC line resistance column vector is consistent with the number of DC power transmission lines included in the multi-terminal DC power transmission system, and m is the number of DC power transmission lines in the multi-terminal DC power transmission system; Based on the DC line resistance column vector, a target node admittance matrix is ​​generated, wherein the number of rows and the number of columns of the target node admittance matrix are consistent with the number of converter stations included in the multi-terminal DC power transmission system; Generate a node voltage equation according to the target node admittance matrix, wherein the number of the node voltage equations is consistent with the number of converter stations included in the multi-terminal direct current transmission system; Based on the control mode and control reference value of each converter station in the multi-terminal direct current power transmission system, a control equation is obtained, wherein the number of the control equations is consistent with the number of converter stations included in the multi-terminal direct current power transmission system; Solving the DC voltage and DC current corresponding to each converter station in the multi-terminal DC transmission system according to the node voltage equation and the control equation; The control mode includes constant DC power control; the control mode and control reference value of each converter station in the multi-terminal DC power transmission system are used to obtain a control equation, including: When the control mode is constant DC power control, the grounding electrode resistance column vector of the multi-terminal DC transmission system is obtained according to the operating wiring mode, the DC resistance level, and four n-dimensional column vectors corresponding to the grounding resistance, the rated value of the grounding electrode lead resistance, the maximum value of the grounding electrode lead resistance, and the minimum value of the grounding electrode lead resistance of each converter station numbered in sequence, and the DC power reference value of each converter station in the multi-terminal DC transmission system is obtained. Based on the DC power reference value and the grounding electrode resistance column vector, the control equation is obtained, wherein n is the number of converter stations in the multi-terminal DC transmission system.

2. The method according to claim 1, characterized in that: The generating a target node admittance matrix based on the DC line resistance column vector comprises: Identify any DC transmission line in the multi-terminal DC power transmission system, and determine two converter station identifiers corresponding to the any DC transmission line; Based on the DC transmission line identifier corresponding to any DC transmission line, searching the DC line resistance corresponding to the DC transmission line identifier from the DC line resistance column vector; According to each converter station identifier, a first position to be updated and a second position to be updated are respectively determined in the initial node admittance matrix, and elements of the first position to be updated and elements of the second position to be updated are respectively updated based on the DC line resistance, wherein the first position to be updated and the second position to be updated are diagonal positions of the initial node admittance matrix; and, A third position to be updated and a fourth position to be updated are determined in the initial node admittance matrix according to the two converter station identifiers, and elements of the third position to be updated and elements of the fourth position to be updated are respectively updated based on the DC line resistance, wherein the third position to be updated and the fourth position to be updated are non-diagonal positions of the initial node admittance matrix.

3. The method according to claim 1, characterized in that The control mode also includes constant current control and constant voltage control; the control mode and control reference value of each converter station in the multi-terminal DC power transmission system are used to obtain a control equation, including: When the control mode is constant current control, obtaining a DC current reference value of each converter station in the multi-terminal DC power transmission system, and obtaining the control equation based on the DC current reference value; When the control mode is constant voltage control, the grounding electrode resistance column vector of the multi-terminal DC transmission system is obtained according to the operating wiring mode and the DC resistance level, and the DC voltage reference value of each converter station in the multi-terminal DC transmission system is obtained, and the control equation is obtained based on the DC voltage reference value and the grounding electrode resistance column vector, wherein the dimension of the grounding electrode resistance column vector is consistent with the number of converter stations included in the multi-terminal DC transmission system.

4. The method according to claim 3, characterized in that The step of obtaining a DC line resistance column vector of the multi-terminal DC power transmission system according to the operation wiring mode and the DC resistance level includes: Determine a first calculation formula for the DC line resistance column vector according to the operation wiring mode and the DC resistance level, and determine the DC line resistance column vector according to the first calculation formula; The step of obtaining the grounding electrode resistance column vector of the multi-terminal DC power transmission system according to the operation wiring mode and the DC resistance level includes: A second calculation formula for the grounding electrode resistance column vector is determined according to the operation wiring mode and the DC resistance level, and the grounding electrode resistance column vector is determined according to the second calculation formula.

5. The method according to claim 3 or 4, characterized in that: When the operation wiring mode is bipolar operation or single-pole metal loop operation, each element in the grounding electrode resistance column vector is zero; Correspondingly, when the control mode is constant voltage control, a DC voltage reference value of each converter station in the multi-terminal DC power transmission system is obtained, and based on the DC voltage reference value, the control equation is obtained; When the control mode is constant DC power control, a DC power reference value of each converter station in the multi-terminal DC power transmission system is obtained, and the control equation is obtained based on the DC power reference value.

6. The method according to claim 1, characterized in that When the DC voltage of any converter station included in the multi-terminal DC power transmission system is known, and the DC currents of the remaining converter stations except the converter station are known, after generating the node voltage equation, the method further includes: Determine a converter station identifier of any converter station, remove row elements and column elements corresponding to the converter station identifier of any converter station from the target node admittance matrix, and obtain an updated target node admittance matrix; Perform inverse transformation on the updated target node admittance matrix to obtain the node impedance matrix; According to Kirchhoff's current law, the DC current of any converter station is calculated by using the DC currents of the remaining converter stations except the any converter station; According to the operation wiring mode and the DC resistance level, a grounding electrode resistance column vector of the multi-terminal DC power transmission system is obtained; The DC voltages of the remaining converter stations are calculated according to the node impedance matrix, the grounding electrode resistance column vector, the DC voltage of any one converter station, and the DC currents of the remaining converter stations.

7. The method according to claim 1, characterized in that After solving the DC voltage and DC current corresponding to each converter station in the multi-terminal DC power transmission system, the method further includes: Record the DC voltage and DC current corresponding to each converter station, and monitor the operation status of each converter station; When monitoring finds that the operating voltage of any converter station exceeds the fluctuation range of the DC voltage and / or the operating current exceeds the fluctuation range of the DC current, an abnormal reminder is output.

8. A DC parameter calculation device for a multi-terminal DC transmission system, characterized in that: include: a first determining module, configured to determine an operation wiring mode and a DC resistance level of a multi-terminal DC power transmission system, and obtain a DC line resistance column vector of the multi-terminal DC power transmission system according to the operation wiring mode, the DC resistance level, and three m-dimensional column vectors corresponding to a DC resistance rated value, a DC resistance maximum value, and a DC resistance minimum value of each DC power transmission line numbered in sequence, wherein the dimension of the DC line resistance column vector is consistent with the number of DC power transmission lines included in the multi-terminal DC power transmission system, and m is the number of DC power transmission lines in the multi-terminal DC power transmission system; A first generating module is used to generate a target node admittance matrix based on the DC line resistance column vector, wherein the number of rows and the number of columns of the target node admittance matrix are consistent with the number of converter stations included in the multi-terminal DC power transmission system; A second generating module is used to generate a node voltage equation according to the target node admittance matrix, wherein the number of the node voltage equations is consistent with the number of converter stations included in the multi-terminal direct current transmission system; a second determining module, configured to obtain a control equation based on a control mode and a control reference value of each converter station in the multi-terminal DC power transmission system, wherein the number of the control equations is consistent with the number of converter stations included in the multi-terminal DC power transmission system; A calculation module, used for solving the DC voltage and DC current corresponding to each converter station in the multi-terminal DC transmission system according to the node voltage equation and the control equation; The control mode includes constant DC power control; the second determination module is used to: When the control mode is constant DC power control, the grounding electrode resistance column vector of the multi-terminal DC transmission system is obtained according to the operating wiring mode, the DC resistance level, and four n-dimensional column vectors corresponding to the grounding resistance, the rated value of the grounding electrode lead resistance, the maximum value of the grounding electrode lead resistance, and the minimum value of the grounding electrode lead resistance of each converter station numbered in sequence, and the DC power reference value of each converter station in the multi-terminal DC transmission system is obtained. Based on the DC power reference value and the grounding electrode resistance column vector, the control equation is obtained, wherein n is the number of converter stations in the multi-terminal DC transmission system.

9. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

10. A computer device comprising a storage medium, a processor, and a computer program stored in the storage medium and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 7 is implemented.

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