Method and system for reducing the number of actions of the tap changer on the inverter side of a high voltage direct current transmission project

Abstract

This invention relates to a method and system for reducing the number of tap changer operations on the inverter side of a high-voltage direct current (HVDC) transmission project. The method includes: determining the sign of a characteristic factor of the HVDC transmission project; and selecting the actual value I of the following DC current, γ, on the inverter side, based on the sign of the characteristic factor and the requirements of the HVDC transmission project regarding the operating range of the arc extinction angle. d The relationship between the changes in the current is used to determine a new reference value for the extinction angle; the new reference value replaces the original reference value for the extinction angle, reducing the frequency of inverter-side tap changer operation during current rises and falls. This invention can significantly reduce the frequency of inverter-side tap changer operation, is simple to implement and requires no changes to the converter station configuration, and improves the operational reliability of the tap changer. This invention can be widely applied in the field of power transmission systems.

Description

Technical Field

[0001] This invention relates to the field of power transmission system technology, and in particular to a method and system for reducing the number of tap changer operations on the inverter side of a high-voltage direct current transmission project. Background Technology

[0002] In high-voltage direct current (HVDC) transmission projects, the converter transformer tap changer is a crucial piece of equipment for ensuring safe and economical operation. It primarily regulates the converter transformer's output voltage, coordinating with the trigger angle and DC voltage adjustments to mitigate changes in AC system voltage and DC power, thereby achieving stable power transmission and preventing excessive reactive power consumption and converter valve operating angles. On the rectifier side, the trigger angle is maintained within a set range through tap adjustment. On the inverter side, there are two main control strategies: constant extinction angle control and constant DC voltage control. In constant extinction angle control, the extinction angle reference value is constant, and the tap changer directly controls the DC voltage. In constant DC voltage control, the tap changer functions similarly to the rectifier-side tap changer, maintaining the extinction angle within a set range through tap adjustment.

[0003] Tap changers are an inherent component of converter transformer equipment in high-voltage direct current (HVDC) transmission projects and are a standard configuration for HVDC transmission projects both domestically and internationally. Unlike most conventional transformers, converter transformer tap changers are on-load tap-changing type. To meet the operational requirements of the DC system, converter transformer tap changers are designed with a large voltage regulation range, generally -5% to +30%, and a relatively small tap interval, typically 1% to 2%. According to statistics on the number of tap changer operations in State Grid Corporation of China's UHVDC transmission projects, the average number of operations per tap changer per year is approximately 4,000, and the cumulative number of tap changer operations per year for a single project is approximately 200,000.

[0004] In actual operation of DC systems, tap changer adjustments due to variations in DC power and AC system conditions are unavoidable. High-frequency tap changer operation places extremely high demands on reliability and is detrimental to the safe and stable operation of the tap changer. Therefore, research into control strategies to reduce the frequency of tap changer operations is essential. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide a method and system for reducing the number of tap changer operations on the inverter side of high-voltage direct current (HVDC) transmission projects. This method is applicable to DC systems where the inverter side uses constant extinction angle control. It can significantly reduce the frequency of tap changer operations on the inverter side, is simple to implement, requires no changes to the converter station configuration, and improves the operational reliability of the tap changer.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for reducing the number of tap changer operations on the inverter side of a high-voltage direct current (HVDC) transmission project, comprising: determining the sign of a characteristic factor of the HVDC transmission project; selecting, based on the sign of the characteristic factor and the requirements of the HVDC transmission project for the operating range of the arc extinction angle, the relationship between the change of the inverter side arc extinction angle γ and the actual value Id of the DC current, to determine a new arc extinction angle reference value; replacing the original arc extinction angle reference value with the new arc extinction angle reference value to reduce the frequency of inverter side tap changer operations during current rise and fall.

[0007] Further, determining the sign of the feature factor includes:

[0008] The expression for the characteristic factor is determined based on the expression for the DC voltage on the rectifier side of the high-voltage direct current transmission project;

[0009] Substitute the equipment parameters of the high-voltage direct current transmission project into the characteristic factor expression to calculate the sign of the characteristic factor.

[0010] Furthermore, the inverter-side arc extinction angle γ follows the actual value I of the DC current. d The relationship of change is determined by the sign of the characteristic factor.

[0011] Furthermore, the inverter-side arc extinction angle γ follows the actual value I of the DC current. d The relationships of change include:

[0012] When the eigenfactor is zero, γ needs to remain constant;

[0013] When the eigenfactor is positive, γ needs to change with I. d It increases with the increase of;

[0014] When the eigenfactor is negative, γ needs to change with I. d It decreases as it increases.

[0015] Furthermore, the new reference value for the arc extinction angle is:

[0016] γ=K·I d +γ0

[0017] Where K is the proportionality coefficient, and its sign is the same as that of the characteristic factor, and γ0 is a constant.

[0018] A system for reducing the number of tap changer operations on the inverter side of a high-voltage direct current (HVDC) transmission project includes: a first processing module for determining the sign of a characteristic factor of the HVDC transmission project; and a second processing module for selecting the actual value I of the inverter-side arc extinction angle γ following the DC current, based on the sign of the characteristic factor and the requirements of the HVDC transmission project for the arc extinction angle operating range. dThe relationship between the changes is used to determine the new arc extinction angle reference value; the parameter replacement module replaces the original arc extinction angle reference value with the new arc extinction angle reference value, reducing the frequency of inverter side tap changer operation during current rise and fall.

[0019] Furthermore, the inverter-side arc extinction angle γ follows the actual value I of the DC current. d The relationships of change include:

[0020] When the eigenfactor is zero, γ needs to remain constant;

[0021] When the eigenfactor is positive, γ needs to change with I. d It increases with the increase of;

[0022] When the eigenfactor is negative, γ needs to change with I. d It decreases as it increases.

[0023] Furthermore, the new reference value for the arc extinction angle is:

[0024] γ=K·I d +γ0

[0025] Where K is the proportionality coefficient, and its sign is the same as that of the characteristic factor, and γ0 is a constant.

[0026] A computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform any of the methods described above.

[0027] A computing device includes: one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include instructions for performing any of the methods described above.

[0028] The present invention has the following advantages due to the adoption of the above technical solutions:

[0029] 1. This invention can effectively reduce the number of inverter-side tap changer operations caused by DC current fluctuations, greatly reduce the risk of tap changer failure, and improve the operational reliability of the converter station.

[0030] 2. This invention can be widely applied to various operating modes of high voltage direct current transmission projects, and will not affect the maximum power transmission capacity of the project.

[0031] 3. This invention only requires modification to the DC control system software, is simple and easy to implement, and can be applied to existing and newly built high-voltage DC transmission projects. Attached Figure Description

[0032] Figure 1This is a flowchart of a method for reducing the number of tap changer operations on the inverter side of a high-voltage direct current transmission project, according to an embodiment of the present invention.

[0033] Figure 2a In one embodiment of the present invention, when K is 0, the inverter-side arc extinction angle γ follows the DC current I. d Diagram illustrating the relationship of change;

[0034] Figure 2b In one embodiment of the present invention, when K is a positive number, the inverter-side arc extinction angle γ follows the DC current I. d Diagram illustrating the relationship of change;

[0035] Figure 2c In one embodiment of the present invention, when K is negative, the inverter-side arc extinction angle γ follows the DC current I. d Diagram illustrating the relationship of change;

[0036] Figure 3a This is a simulation curve of the main electrical parameters of the DC system when the characteristic factor is positive, during the process of simulating the DC current increasing from 0.1pu to 1.0pu, using the existing strategy in one embodiment of the present invention;

[0037] Figure 3b This is a simulation curve of the main electrical parameters of the DC system when the feature factor is positive, during the process of simulating the DC current increasing from 0.1 pu to 1.0 pu, when the strategy of the present invention is adopted in one embodiment of the present invention.

[0038] Figure 4a This is a simulation curve of the main electrical parameters of the DC system when the characteristic factor is negative, during the process of simulating the DC current increasing from 0.1pu to 1.0pu, using the existing strategy in one embodiment of the present invention;

[0039] Figure 4b This is a simulation curve of the main electrical parameters of the DC system when the feature factor is negative, during the process of simulating the DC current increasing from 0.1pu to 1.0pu, using the strategy of the present invention in one embodiment of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0041] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0042] The present invention provides a method and system for reducing the number of tap changer operations on the inverter side of a high-voltage direct current (HVDC) transmission project, comprising: calculating the sign of the characteristic factor of the HVDC transmission project; γ following I d The selection and parameter configuration of the changing relationship. This invention can significantly reduce the number of inverter-side tap changer operations, and the implementation of the method does not require additional hardware equipment or modification of existing hardware designs.

[0043] In one embodiment of the present invention, a method for reducing the number of tap changer operations on the inverter side of a high-voltage direct current transmission project is provided. In this embodiment, as shown... Figure 1 As shown, the method includes the following steps:

[0044] 1) Determine the symbols for the characteristic factors of high-voltage direct current transmission projects;

[0045] 2) Based on the sign of the characteristic factor and the requirements of the high-voltage direct current transmission project for the operating range of the arc extinction angle, select the actual value I of the inverter-side arc extinction angle γ following the DC current. d The relationship between the changes is used to determine the new reference value for the arc extinguishing angle;

[0046] 3) Replace the original arc extinction angle reference value with the new arc extinction angle reference value to reduce the frequency of inverter side tap changer operation during current rise and fall.

[0047] In step 1) above, determining the sign of the characteristic factor includes the following steps:

[0048] 1.1) Determine the expression for the characteristic factor based on the expression for the DC voltage on the rectifier side of the high-voltage direct current transmission project;

[0049] For example, the DC voltage U on the rectifier side of a high-voltage direct current transmission project. dR It can be calculated using the following formula:

[0050]

[0051] Among them, U di0I U represents the actual value of the ideal no-load DC voltage of a 6-pulse converter on the inverter side. di0NI U represents the ideal no-load DC voltage rating for a 6-pulse converter on the inverter side. T For the inherent voltage drop of a 6-pulse converter, Id I is the actual value of the DC current. dN The rated value of DC current, d xI For the inverter-side inductor voltage drop, d rI R is the inverter-side voltage drop across the inverter side, γ is the inverter-side extinction angle (for constant extinction angle control projects, i.e., the extinction angle reference value), n is the number of 6-pulse converters per pole, and R is the inverter-side voltage drop across the inverter side. d This refers to the resistance of a DC line. That is, the expression for the characteristic factor.

[0052] As can be seen from equation (1), due to n and U in the equation T and Both are constants. In order to keep the DC voltage on the rectifier side at its rated value, when I d When changes occur, U di0I cosγ should also change. Ignoring the effects of voltage variations in the AC system, then U di0I It only relates to the tap position on the inverter side. Therefore, in order to keep both the DC voltage and the inverter-side tap position constant during changes in DC current, it is necessary to find a way to make γ follow I. d The relationship of change. And this relationship of change is affected by characteristic factors. The impact.

[0053] 1.2) Substitute the equipment parameters of the high-voltage direct current transmission project into the characteristic factor expression. The sign of the characteristic factor is calculated.

[0054] In this embodiment, when calculating the sign of the characteristic factor, various combinations of different operating modes such as bipolar / single-polar, single converter / dual converter, and earth / metal can be considered to calculate and obtain the matching characteristic factor; alternatively, only one or a few of the most commonly used operating modes can be selected to calculate and obtain the matching characteristic factor.

[0055] In step 2) above, the inverter-side arc extinction angle γ follows the actual value I of the DC current. d The relationship of change is determined by the sign of the characteristic factor.

[0056] Specifically, the inverter-side arc extinction angle γ follows the actual value of the DC current I. d The relationship of change is as follows:

[0057] like Figure 2a As shown, γ needs to remain constant when the eigenfactor is zero;

[0058] like Figure 2b As shown, when the eigenfactor is positive, γ needs to increase with I. d It increases with the increase of;

[0059] like Figure 2c As shown, when the eigenfactor is negative, γ needs to change with I. d It decreases as it increases.

[0060] In step 2) above, the new reference value for the arc extinguishing angle is:

[0061] γ=K·I d +γ0

[0062] Where K is the proportionality coefficient, with the same sign as the characteristic factor, and γ0 is a constant. K and γ0 should be selected such that when the DC current varies between 0.1 pu and 1.0 pu, the maximum value of the arc extinction angle γ should not exceed the γ limit imposed by the equipment's permissible operating capacity. MAX The minimum value should not be lower than the γ required for reliable commutation. MIN And take into account a certain margin.

[0063] Example 1: Taking a high-voltage direct current transmission project with a characteristic factor of +10.85 as an example, the total number of tap changer operations, main circuit operating characteristics, and simulation waveforms during the change of DC current from minimum (250A) to rated (2500A) are compared between the original strategy and the new strategy through electromagnetic transient simulation results. Tables 1 and 2 show these results.

[0064] Table 1. Main circuit operating characteristics using the original strategy in bipolar operation mode.

[0065]

[0066] Table 2. Main circuit operating characteristics using the new strategy in bipolar operation mode.

[0067]

[0068] like Figure 3a , Figure 3b As shown in the above comparison, it can be found that for high-voltage direct current transmission projects with positive characteristic factors, adopting the strategy of increasing the arc extinction angle on the inverter side with the increase of DC current can significantly reduce the number of tap changer operations on the inverter side caused by changes in transmission power, while the number of tap changer operations on the rectifier side remains unaffected.

[0069] Example 2: Taking a high-voltage direct current transmission project with a characteristic factor of -6.58 as an example, the total number of tap changer operations, main circuit operating characteristics, and simulation waveforms during the change of DC current from minimum (250A) to rated (2500A) are compared between the original strategy and the new strategy through electromagnetic transient simulation results. Tables 3 and 4 show these results.

[0070] Table 3 shows the main circuit operating characteristics using the original strategy in the bipolar operation mode.

[0071]

[0072] Table 4. Main circuit operating characteristics using the new strategy in bipolar operation mode.

[0073]

[0074] like Figure 4a , Figure 4b As shown in the above comparison, it can be found that for high-voltage direct current transmission projects with negative characteristic factors, adopting the strategy of decreasing the arc extinction angle on the inverter side as the DC current increases can significantly reduce the number of tap changer operations on the inverter side caused by changes in transmission power, while the number of tap changer operations on the rectifier side remains unaffected.

[0075] In high-voltage direct current (HVDC) transmission projects, there are various combinations of operating modes, including bipolar / monopolar, single-converter / dual-converter, and earth / metal. For different operating modes, when calculating the characteristic factors, only d needs to be considered. xI , d rI The parameters R and n are changed accordingly, but the expression of the characteristic factor remains unchanged. Therefore, the new strategy can be considered to be effective and universally applicable to high voltage direct current transmission projects.

[0076] In summary, the method of reducing the number of tap changer operations on the inverter side of a high-voltage direct current transmission project according to the present invention is applicable to DC systems where the inverter side is controlled by the arc extinction angle. It does not require adding new hardware devices to the original project, nor does it require changing any hardware design in the original project. It can be achieved simply by modifying the software of the DC control system.

[0077] In one embodiment of the present invention, a system for reducing the number of tap changer operations on the inverter side of a high-voltage direct current transmission project is provided, comprising:

[0078] The first processing module determines the symbols of the characteristic factors of the high-voltage direct current transmission project;

[0079] The second processing module, based on the sign of the characteristic factor and the requirements of the high-voltage direct current transmission project for the arc extinction angle operating range, selects the actual value I of the inverter-side arc extinction angle γ following the DC current. d The relationship between the changes is used to determine the new reference value for the arc extinction angle;

[0080] The parameter replacement module replaces the original arc extinction angle reference value with a new one, reducing the frequency of inverter-side tap changer operation during current rise and fall.

[0081] In the first processing module mentioned above, the inverter-side arc extinction angle γ follows the actual value I of the DC current. d The relationships of change include:

[0082] When the eigenfactor is zero, γ needs to remain constant;

[0083] When the eigenfactor is positive, γ needs to change with I. d It increases with the increase of;

[0084] When the eigenfactor is negative, γ needs to change with I. d It decreases as it increases.

[0085] In the second processing module mentioned above, the new arc extinction angle reference value is:

[0086] γ=K·I d +γ0

[0087] Where K is the proportionality coefficient, and its sign is the same as that of the characteristic factor, and γ0 is a constant.

[0088] The system provided in this embodiment is used to execute the above-described method embodiments. For specific processes and details, please refer to the above embodiments, which will not be repeated here.

[0089] In one embodiment of the present invention, a computing device structure is provided. This computing device can be a terminal, which may include: a processor, a communication interface, memory, a display screen, and an input device. The processor, communication interface, and memory communicate with each other via a communication bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system and a computer program. When executed by the processor, the computer program implements a method for reducing the number of tap changer operations on the inverter side of a high-voltage direct current transmission project. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The communication interface is used for wired or wireless communication with external terminals. Wireless communication can be achieved through Wi-Fi, a management network, NFC (Near Field Communication), or other technologies. The display screen can be a liquid crystal display or an e-ink display. The input device can be a touch layer covering the display screen, or buttons, a trackball, or a touchpad mounted on the casing of the computing device, or an external keyboard, touchpad, or mouse, etc. The processor can call logical instructions from memory to execute the following methods: determine the sign of the characteristic factor of the HVDC transmission project; and select the actual value I of the inverter-side arc extinction angle γ following the DC current, based on the sign of the characteristic factor and the requirements of the HVDC transmission project for the arc extinction angle operating range. d The relationship between the changes is used to determine the new arc extinction angle reference value; the new arc extinction angle reference value replaces the original arc extinction angle reference value, reducing the frequency of inverter side tap changer operation during current rise and fall.

[0090] Furthermore, the logical instructions in the aforementioned memory can be implemented as software functional units and sold or used as independent products, and can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0091] Those skilled in the art will understand that the structure of the above-described computing device is only a partial structure related to the solution of this application and does not constitute a limitation on the computing device to which the solution of this application is applied. A specific computing device may include more or fewer components, or combine certain components, or have different component arrangements.

[0092] In one embodiment of the present invention, a computer program product is provided, the computer program product comprising a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions, which, when executed by a computer, enable the computer to perform the methods provided in the above-described method embodiments, for example including: determining the sign of a characteristic factor of a high-voltage direct current transmission project; and selecting the actual value I of the inverter-side arc extinction angle γ following the DC current, based on the sign of the characteristic factor and the requirements of the high-voltage direct current transmission project for the arc extinction angle operating range. d The relationship between the changes is used to determine the new arc extinction angle reference value; the new arc extinction angle reference value replaces the original arc extinction angle reference value, reducing the frequency of inverter side tap changer operation during current rise and fall.

[0093] In one embodiment of the present invention, a non-transitory computer-readable storage medium is provided, which stores server instructions that cause a computer to execute the methods provided in the above embodiments, including, for example,: determining the sign of a characteristic factor of a high-voltage direct current (HVDC) transmission project; and selecting the actual value I of the inverter-side arc extinction angle γ following the DC current, based on the sign of the characteristic factor and the requirements of the HVDC transmission project for the arc extinction angle operating range. d The relationship between the changes is used to determine the new arc extinction angle reference value; the new arc extinction angle reference value replaces the original arc extinction angle reference value, reducing the frequency of inverter side tap changer operation during current rise and fall.

[0094] The computer-readable storage medium provided in the above embodiments has a similar implementation principle and technical effect to the above method embodiments, and will not be described again here.

[0095] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0096] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0097] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for reducing the number of tap changer operations on the inverter side of a high-voltage direct current transmission project, characterized in that, include: Determine the symbols for the characteristic factors of high-voltage direct current transmission projects; Based on the sign of the characteristic factor and the requirements of the high-voltage direct current transmission project for the operating range of the arc extinction angle, the actual value I of the inverter-side arc extinction angle γ following the DC current is selected. d The relationship between the changes is used to determine the new reference value for the arc extinction angle; Replace the original arc extinction angle reference value with the new arc extinction angle reference value to reduce the frequency of inverter side tap changer operation during current rise and fall. Determining the sign of the feature factor includes: The expression for the characteristic factor is determined based on the expression for the DC voltage on the rectifier side of the high-voltage direct current transmission project; The expression for the characteristic factor is: R d U is the resistance of the DC line. di0NI I represents the ideal no-load DC voltage rating of a 6-pulse converter on the inverter side, where n is the number of 6-pulse converters per pole. dN The rated value of DC current, d xI For the inverter-side inductor voltage drop, d rI This is the voltage drop across the inverter side resistor; Substitute the equipment parameters of the high-voltage direct current transmission project into the characteristic factor expression to calculate the sign of the characteristic factor; Inverter-side arc extinction angle γ follows the actual value of DC current I d The relationship of change is determined by the sign of the characteristic factor; Inverter-side arc extinction angle γ follows the actual value of DC current I d The relationships of change include: When the eigenfactor is zero, γ needs to remain constant; When the eigenfactor is positive, γ needs to change with I. d It increases with the increase of; When the eigenfactor is negative, γ needs to change with I. d It decreases as it increases.

2. The method for reducing the number of tap changer operations on the inverter side of a high-voltage direct current transmission project as described in claim 1, characterized in that, The new arc extinction angle reference value is: γ=K·I d +γ0 Where K is the proportionality coefficient, and its sign is the same as that of the characteristic factor, and γ0 is a constant.

3. A system for reducing the number of tap changer operations on the inverter side of a high-voltage direct current transmission project, characterized in that, include: The first processing module determines the symbols of the characteristic factors of the high-voltage direct current transmission project; The second processing module, based on the sign of the characteristic factor and the requirements of the high-voltage direct current transmission project for the arc extinction angle operating range, selects the actual value I of the inverter-side arc extinction angle γ following the DC current. d The relationship between the changes is used to determine the new reference value for the arc extinction angle; The parameter replacement module replaces the original arc extinction angle reference value with the new arc extinction angle reference value, thereby reducing the frequency of inverter side tap changer operation during current rise and fall. Determining the sign of the feature factor includes: The expression for the characteristic factor is determined based on the expression for the DC voltage on the rectifier side of the high-voltage direct current transmission project; The expression for the characteristic factor is: R d U is the resistance of the DC line. di0NI I represents the ideal no-load DC voltage rating of a 6-pulse converter on the inverter side, where n is the number of 6-pulse converters per pole. dN The rated value of DC current, d xI For the inverter-side inductor voltage drop, d rI This is the voltage drop across the inverter side resistor; Substitute the equipment parameters of the high-voltage direct current transmission project into the characteristic factor expression to calculate the sign of the characteristic factor; Inverter-side arc extinction angle γ follows the actual value of DC current I d The relationships of change include: When the eigenfactor is zero, γ needs to remain constant; When the eigenfactor is positive, γ needs to change with I. d It increases with the increase of; When the eigenfactor is negative, γ needs to change with I. d It decreases as it increases.

4. The system for reducing the number of tap changer operations on the inverter side of a high-voltage direct current transmission project as described in claim 3, characterized in that, The new arc extinction angle reference value is: γ=K·I d +γ0 Where K is the proportionality coefficient, and its sign is the same as that of the characteristic factor, and γ0 is a constant.

5. A computer-readable storage medium for storing one or more programs, characterized in that, The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform any of the methods described in claims 1 to 2.

6. A computing device, characterized in that, include: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for performing any of the methods described in claims 1 to 2.

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