Control method and device for series multi-terminal DC transmission system of deep sea wind power

Abstract

The present application relates to a control method, device, and apparatus for a series multi-terminal DC transmission system for deep-sea wind power. The method comprises obtaining the rated DC voltage and DC current of an onshore converter station, as well as obtaining the rated operating voltage and output power based on maximum power point tracking of each offshore converter station; calculating the minimum allowable DC current based on the output power and the rated operating voltage, selecting the maximum value from n minimum allowable DC currents to obtain the optimal DC current reference value for the onshore converter station; obtaining the second DC voltage of the onshore converter station in real time and determining the DC bias value based on the rated DC voltage; and controlling the operation of the onshore converter station using the optimal DC current reference value and the DC bias value. By controlling the operation of the onshore converter station through this method, the operating loss of the series multi-terminal DC transmission system is reduced. At the same time, balanced control of the DC voltage is achieved without relying on communication between the converter stations, thereby reducing communication costs.

Description

Technical Field

[0001] The present application relates to the field of offshore wind power technology, and in particular to a control method, device and equipment for a series multi-terminal direct current transmission system for deep-sea wind power. Background Art

[0002] With global climate change, renewable energy has emerged to mitigate the over-exploitation of natural resources. The vigorous development of renewable energy is a key global approach to addressing climate change. As high-quality land resources are gradually developed and utilized, offshore wind power generation, with its larger area and richer resources, has become a focus of attention.

[0003] Offshore wind power resources are abundant and close to power load areas, and are expected to become the main direction of renewable energy development in the future. Based on this, a series multi-terminal transmission system suitable for large-scale and deep-sea wind power transmission has been proposed. Although compared with the traditional parallel multi-terminal transmission system, the series multi-terminal transmission system can significantly reduce the voltage level of offshore wind farms, thereby reducing the cost of wind farm construction. For the current series multi-terminal control method of the series multi-terminal transmission system, the DC current is controlled by the onshore converter station of the series multi-terminal transmission system, and the offshore station of the series multi-terminal transmission system achieves maximum wind power following control by adjusting the DC voltage. However, unlike the parallel multi-terminal transmission system that selects a fixed DC voltage reference value according to system conditions, the DC current of the series multi-terminal transmission system will affect the system loss, the DC voltage fluctuation range of each station, etc. Summary of the Invention

[0004] The embodiments of the present application provide a control method, device and equipment for a series multi-terminal direct current transmission system for deep-sea wind power, which is used to solve the technical problems of large transmission losses and high communication costs in the control strategy of the onshore converter station in the existing series multi-terminal transmission system for deep-sea wind power.

[0005] In order to achieve the above objectives, the embodiments of the present application provide the following technical solutions:

[0006] A control method for a series multi-terminal direct current (HVDC) transmission system for deep-sea wind power generation is disclosed. The control method is applied to the series multi-terminal direct current (HVDC) transmission system, wherein the series multi-terminal direct current (HVDC) transmission system includes an onshore converter station and n serially connected offshore converter stations. The control method comprises the following steps:

[0007] Obtaining the rated DC voltage and DC current of the onshore converter station and obtaining the rated operating voltage and maximum power point tracking-based output power of each offshore converter station;

[0008] Calculating, based on the output power and rated operating voltage of each offshore converter station, a minimum allowable DC current of the corresponding offshore converter station is obtained, and selecting the largest value from the n minimum allowable DC currents as the optimal DC current reference value of the onshore converter station;

[0009] acquiring in real time a second DC voltage of a DC line port of the onshore converter station, and determining a DC bias of the onshore converter station according to the second DC voltage and the rated DC voltage;

[0010] The operation of the onshore converter station is controlled using the optimal DC current reference value and the DC bias.

[0011] Preferably, the control method of the deep sea wind power series multi-terminal direct current transmission system includes: obtaining a first direct current voltage corresponding to the offshore converter station according to calculations based on the direct current and the output power of each offshore converter station.

[0012] Preferably, determining the DC bias of the onshore converter station according to the second DC voltage and the rated DC voltage includes: obtaining the DC bias of the onshore converter station using a bias calculation formula according to the second DC voltage and the rated DC voltage, wherein the bias calculation formula is:

[0013]

[0014] Where U dc is the second DC voltage, U dc_rate is the rated DC voltage, and A is the DC bias.

[0015] Preferably, the control method of the series multi-terminal DC transmission system for deep-sea wind power includes: under the condition that the first DC voltage is not greater than the rated operating voltage of the corresponding offshore converter station, calculating the minimum allowable DC current of the corresponding offshore converter station according to the output power and rated operating voltage of each offshore converter station.

[0016] The present application also provides a control device for a series multi-terminal DC transmission system for deep-sea wind power, which is applied to the series multi-terminal DC transmission system. The series multi-terminal DC transmission system includes an onshore converter station and n serially connected offshore converter stations. The control device includes a data acquisition module, a first calculation module, a second calculation module, and a control module.

[0017] The data acquisition module is configured to acquire the rated DC voltage and DC current of the onshore converter station and the rated operating voltage and maximum power point tracking-based output power of each offshore converter station;

[0018] The first calculation module is configured to calculate, based on the output power and rated operating voltage of each offshore converter station, a minimum allowable DC current of the corresponding offshore converter station, and select the largest value from the n minimum allowable DC currents as the optimal DC current reference value of the onshore converter station;

[0019] The second calculation module is configured to obtain a second DC voltage of the DC line port of the onshore converter station in real time, and determine a DC bias of the onshore converter station according to the second DC voltage and the rated DC voltage;

[0020] The control module is used to control the operation of the onshore converter station by using the optimal DC current reference value and the DC bias.

[0021] Preferably, the control device of the deep-sea wind power series multi-terminal direct current transmission system includes a third calculation module, which is used to calculate the first DC voltage corresponding to the offshore converter station based on the DC current and the output power of each offshore converter station.

[0022] Preferably, the first calculation module is further configured to calculate the minimum allowable DC current of the corresponding offshore converter station according to the output power and rated operating voltage of each offshore converter station, based on the condition that the first DC voltage is not greater than the rated operating voltage of the corresponding offshore converter station.

[0023] Preferably, the second calculation module is further configured to obtain the DC offset of the onshore converter station using an offset calculation formula according to the second DC voltage and the rated DC voltage, wherein the offset calculation formula is:

[0024]

[0025] Where U dc is the second DC voltage, U dc_rate is the rated DC voltage, and A is the DC bias.

[0026] The present application also provides a computer-readable storage medium for storing computer instructions, which, when executed on a computer, enables the computer to execute the control method for the deep-sea wind power series multi-terminal direct current transmission system described above.

[0027] The present application also provides a terminal device, including a processor and a memory;

[0028] The memory is used to store program code and transmit the program code to the processor;

[0029] The processor is configured to execute the above-mentioned control method for the deep-sea wind power series multi-terminal direct current transmission system according to the instructions in the program code.

[0030] It can be seen from the above technical solution that the embodiments of the present application have the following advantages: the control method, device and equipment of the series multi-terminal DC transmission system of deep-sea wind power, the method comprising: obtaining the rated DC voltage and DC current of the onshore converter station and obtaining the rated operating voltage and the output power based on maximum power point tracking of each offshore converter station; calculating according to the output power and rated operating voltage of each offshore converter station, obtaining the minimum allowable DC current of the corresponding offshore converter station, selecting the largest data from n minimum allowable DC currents as the optimal DC current reference value of the onshore converter station; obtaining the second DC voltage of the DC line port of the onshore converter station in real time, and determining the DC bias of the onshore converter station according to the second DC voltage and the rated DC voltage; and controlling the operation of the onshore converter station using the optimal DC current reference value and DC bias. The control method of the series multi-terminal DC transmission system for deep-sea wind power can adjust and optimize the optimal DC current reference value of the onshore converter station in real time according to the operation status of the series multi-terminal DC transmission system, effectively reduce the operation loss of the series multi-terminal DC transmission system, and avoid overvoltage of the converter valve power module in the converter station; adopt the DC bias to automatically adjust the balancing node voltage based on the local voltage, and realize the balanced control of the DC voltage without relying on the communication between the converter stations, thereby reducing the communication cost; it also meets the requirement that the voltage sum of the series multi-terminal DC transmission system is 0, and solves the technical problems of large transmission loss and high communication cost in the control strategy of the onshore converter station in the existing series multi-terminal transmission system for deep-sea wind power. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0032] Figure 1 This is a flowchart of the steps of the control method of the deep-sea wind power series multi-terminal direct current transmission system according to the embodiment of the present application;

[0033] Figure 2 This is a framework diagram of the onshore converter station control strategy in the series multi-terminal DC transmission system for deep-sea wind power according to an embodiment of the present application;

[0034] Figure 3 This is a framework diagram of the control device of the deep sea wind power series multi-terminal direct current transmission system described in an embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, features, and advantages of the invention of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described below are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0036] The embodiments of the present application provide a control method, device and equipment for a series multi-terminal DC transmission system for deep-sea wind power, which is used to solve the technical problems of large transmission losses and high communication costs in the control strategy of the onshore converter station in the existing series multi-terminal transmission system for deep-sea wind power.

[0037] Example 1:

[0038] Figure 1 This is a flowchart of the steps of the control method of the deep sea wind power series multi-terminal direct current transmission system described in an embodiment of the present application.

[0039] like Figure 1 As shown, an embodiment of the present application provides a control method for a series multi-terminal DC transmission system for deep-sea wind power, which is applied to a series multi-terminal DC transmission system comprising an onshore converter station and n serially connected offshore converter stations. The control method comprises the following steps:

[0040] S1. Obtain the rated DC voltage and DC current of the onshore converter station and the rated operating voltage and maximum power point tracking-based output power of each offshore converter station.

[0041] It should be noted that in step S1, the rated DC voltage U dc_rate and DC current I dc ; Also obtain the rated operating voltage of each offshore converter station And the power delivered by offshore wind power in MPPT (maximum power point tracking) mode is recorded as the delivered power i is the i-th offshore converter station, i∈n, and n is a natural number greater than 2. is the rated operating voltage of the i-th offshore converter station.

[0042] S2. Calculate the minimum allowable DC current for each offshore converter station based on the output power and rated operating voltage of each offshore converter station. Select the largest value from the n minimum allowable DC currents as the optimal DC current reference value for the onshore converter station.

[0043] It should be noted that in step S2, the first step is to calculate the output power of each offshore converter station. and rated operating voltage Calculate the minimum allowable DC current of the corresponding offshore converter station The second is to obtain the optimal DC current reference value of the onshore converter station from the minimum allowable DC current of n offshore converter stations. In this embodiment, the small DC current is calculated

[0044] Furthermore, selecting the largest value from the n minimum allowable DC currents as the optimal DC current reference value of the onshore converter station includes selecting the largest value from the n minimum allowable DC currents as the optimal DC current reference value of the onshore converter station.

[0045] It should be noted that in a TMDC system, the optimal DC current reference value of the onshore converter station in the TMDC system is limited by comprehensively considering the DC voltage limit and minimum loss of the converter station in the TMDC system.

[0046] S3. Acquire a second DC voltage at the DC line port of the onshore converter station in real time, and determine a DC bias of the onshore converter station based on the second DC voltage and the rated DC voltage.

[0047] It should be noted that in step S3, the first step is to obtain the second DC voltage U of the DC line port of the onshore converter station in real time. dc ; The second is to obtain the second DC voltage U of the shore converter station dc and rated DC voltage U dc_rate Obtain the DC bias of the onshore converter station.

[0048] Furthermore, determining the DC bias of the onshore converter station according to the second DC voltage and the rated DC voltage includes: obtaining the DC bias of the onshore converter station according to the second DC voltage and the rated DC voltage using a bias calculation formula, where the bias calculation formula is:

[0049]

[0050] Where U dc is the second DC voltage, U dc_rate is the rated DC voltage, and A is the DC bias.

[0051] It should be noted that in a series multi-terminal DC transmission system, the DC current stability of the offshore converter station is controlled by the onshore converter station, and the offshore converter station realizes power tracking by controlling its own DC voltage. Since the DC voltage of other offshore converter stations changes in real time with the wind power output, in addition to the DC current, the control parameters of the onshore converter station in the series multi-terminal DC transmission system should also be controlled as a balancing node to ensure that the sum of the voltages of the multi-terminal transmission system is 0. In this embodiment, for controlling the operation of the onshore converter station of the series multi-terminal DC transmission system, the dq axis is used to control the DC current and reactive power to obtain the control voltage u of the onshore converter station. cabc_ref (like Figure 2 As shown), and the DC bias and control voltage u cabc_ref Automatically adjust the balanced node voltage without relying on communication between converter stations to achieve balanced control of DC voltage.

[0052] S4. Use the optimal DC current reference value and DC bias to control the operation of the onshore converter station.

[0053] It should be noted that in this embodiment, the control strategy of the series multi-terminal direct current transmission system is a relatively mature technology in this field, such as the "Control Method and Device for a Series Multi-Terminal Direct Current System Suitable for Offshore Wind Farms" disclosed in Publication No. CN113285478A. The details of the control strategy of the series multi-terminal direct current transmission system are not described in this embodiment. In the embodiment of the present application, the parameters of the control strategy of the existing series multi-terminal direct current transmission system are optimized. Specifically, the DC bias is used to optimize the control voltage u of the control strategy of the series multi-terminal direct current transmission system. cabc_ref The optimized voltage and optimal DC current reference value are used together to control the operation of the onshore converter station. This achieves a significant reduction in losses in the series multi-terminal DC transmission system by using the optimal DC current reference value optimized in real time using DC current, while also preventing overvoltage or undervoltage in the converter valve power modules in each converter station of the system. By utilizing the negative voltage output capability of the full-bridge power modules at the onshore converter station, decoupling control of the DC and AC side voltages of the converter station is achieved, achieving dq axis control of DC current and reactive power. The DC bias automatically adjusts the balanced node voltage without relying on communication between the converter stations, achieving the goal of balanced DC voltage control of the series multi-terminal DC transmission system.

[0054] The present application provides a control method for a series multi-terminal DC transmission system for deep-sea wind power, the method comprising obtaining the rated DC voltage and DC current of an onshore converter station and obtaining the rated operating voltage and the output power based on maximum power point tracking of each offshore converter station; calculating based on the output power and rated operating voltage of each offshore converter station to obtain the minimum allowable DC current of the corresponding offshore converter station, selecting the largest data from n minimum allowable DC currents as the optimal DC current reference value of the onshore converter station; obtaining in real time a second DC voltage at a DC line port of the onshore converter station, determining a DC bias of the onshore converter station based on the second DC voltage and the rated DC voltage; and controlling the operation of the onshore converter station using the optimal DC current reference value and the DC bias. The control method of the series multi-terminal DC transmission system for deep-sea wind power can adjust and optimize the optimal DC current reference value of the onshore converter station in real time according to the operation status of the series multi-terminal DC transmission system, effectively reduce the operation loss of the series multi-terminal DC transmission system, and avoid overvoltage of the converter valve power module in the converter station; the DC bias is used to automatically adjust the balancing node voltage based on the local voltage, and the DC voltage balance control can be achieved without relying on the communication between the converter stations. It also meets the requirement of the series multi-terminal DC transmission system that the voltage sum is 0, and solves the technical problems of large transmission loss and high communication cost in the control strategy of the onshore converter station in the existing series multi-terminal transmission system for deep-sea wind power.

[0055] It should be noted that the control method of the deep-sea wind power series multi-terminal DC transmission system is also suitable for complex working conditions in which the DC voltage of the series multi-terminal DC transmission system is greatly and frequently adjusted for wind turbine processing.

[0056] In one embodiment of the present application, a first DC voltage for each offshore converter station is calculated based on the DC current and the output power of each offshore converter station. Furthermore, under the condition that the first DC voltage is no greater than the rated operating voltage of the corresponding offshore converter station, a minimum allowable DC current for each offshore converter station is calculated based on the output power and rated operating voltage of each offshore converter station.

[0057] It should be noted that, first, the first DC voltage of each offshore converter station is calculated. Second, according to the first DC voltage of each offshore converter station Determine the rated operating voltage for each offshore converter station In this embodiment, the first DC voltage In order to reduce the operating loss of the series multi-terminal DC transmission system, the optimal DC current reference value of the onshore converter station should be as small as possible, and the corresponding first DC voltage of the offshore converter station should be as large as possible. However, considering the number of converter valve power modules in the offshore converter station, the range of the first DC voltage value is

[0058] Example 2:

[0059] Figure 3 This is a framework diagram of a control device for a series multi-terminal direct current transmission system for deep-sea wind power according to an embodiment of the present application.

[0060] like Figure 3 As shown, an embodiment of the present application further provides a control device for a series multi-terminal DC transmission system for deep-sea wind power, which is applied to the series multi-terminal DC transmission system. The series multi-terminal DC transmission system includes an onshore converter station and n serially connected offshore converter stations. The control device includes a data acquisition module 10, a first calculation module 20, a second calculation module 30, and a control module 50.

[0061] A data acquisition module 10 is configured to acquire the rated DC voltage and DC current of the onshore converter station and the rated operating voltage and maximum power point tracking-based output power of each offshore converter station;

[0062] A first calculation module 20 is configured to calculate, based on the output power and rated operating voltage of each offshore converter station, a minimum allowable DC current for the corresponding offshore converter station, and select the largest value from among the n minimum allowable DC currents as an optimal DC current reference value for the onshore converter station;

[0063] The calculation module 30 is used to obtain the second DC voltage of the DC line port of the onshore converter station in real time, and determine the DC bias of the onshore converter station according to the second DC voltage and the rated DC voltage;

[0064] The control module 40 is used to control the operation of the onshore converter station using the optimal DC current reference value and DC offset.

[0065] In an embodiment of the present application, the control device of the deep-sea wind power series multi-terminal direct current transmission system includes a third calculation module, which is used to calculate the first DC voltage corresponding to the offshore converter station based on the DC current and the output power of each offshore converter station.

[0066] In the embodiment of the present application, the second calculation module 30 is further configured to obtain the DC offset of the onshore converter station using an offset calculation formula according to the second DC voltage and the rated DC voltage. The offset calculation formula is:

[0067]

[0068] Where U dc is the second DC voltage, U dc_rate is the rated DC voltage, and A is the DC bias.

[0069] Preferably, the first calculation module 20 is further configured to calculate the minimum allowable DC current of the corresponding offshore converter station according to the output power and rated operating voltage of each offshore converter station, under the condition that the first DC voltage is not greater than the rated operating voltage of the corresponding offshore converter station.

[0070] It should be noted that the modules in the device of Example 2 correspond to the steps in the method of Example 1. The content of the control method of the series multi-terminal DC transmission system of deep-sea wind power has been explained in detail in Example 1. The content of the modules in the device will not be explained in detail in this Example 2.

[0071] Example 3:

[0072] An embodiment of the present application provides a computer-readable storage medium for storing computer instructions, which, when executed on a computer, enables the computer to execute the above-mentioned control method for the series multi-terminal direct current transmission system for deep-sea wind power.

[0073] Example 4:

[0074] An embodiment of the present application provides a terminal device, including a processor and a memory;

[0075] A memory, configured to store program codes and transmit the program codes to a processor;

[0076] The processor is configured to execute the control method of the deep-sea wind power series multi-terminal direct current transmission system according to the instructions in the program code.

[0077] It should be noted that the processor is configured to execute the steps of the aforementioned embodiment of a control method for a deep-sea wind power series multi-terminal direct current transmission system according to the instructions in the program code. Alternatively, the processor implements the functions of the modules / units in the aforementioned system / device embodiments when executing the computer program.

[0078] For example, a computer program may be divided into one or more modules / units, one or more of which are stored in a memory and executed by a processor to complete the present application. One or more modules / units may be a series of computer program instruction segments capable of performing specific functions, and the instruction segments are used to describe the execution process of the computer program in a terminal device.

[0079] Terminal devices can be computing devices such as desktop computers, laptops, PDAs, and cloud servers. Terminal devices may include, but are not limited to, processors and memory. Those skilled in the art will appreciate that this does not constitute a limitation on terminal devices and may include more or fewer components than shown, or a combination of certain components, or different components. For example, terminal devices may also include input / output devices, network access devices, buses, and the like.

[0080] The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0081] Memory can be an internal storage unit of a terminal device, such as a hard drive or memory. It can also be an external storage device, such as a plug-in hard drive, a SmartMedia Card (SMC), a Secure Digital (SD) card, or a flash memory card. Furthermore, memory can include both internal and external storage units. Memory is used to store computer programs and other programs and data required by the terminal device. Memory can also be used to temporarily store data that has been output or is about to be output.

[0082] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0083] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0084] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0085] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0086] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0087] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A control method for a series multi-terminal direct current (HVDC) transmission system for deep-sea wind power, applied to a series multi-terminal direct current (HVDC) transmission system, characterized in that: The series multi-terminal direct current transmission system includes an onshore converter station and n serially connected offshore converter stations. The control method includes the following steps: Obtaining the rated DC voltage and DC current of the onshore converter station and obtaining the rated operating voltage and maximum power point tracking-based output power of each offshore converter station; Calculating, based on the output power and rated operating voltage of each offshore converter station, a minimum allowable DC current of the corresponding offshore converter station is obtained, and selecting the largest value from the n minimum allowable DC currents as the optimal DC current reference value of the onshore converter station; acquiring in real time a second DC voltage of a DC line port of the onshore converter station, and determining a DC bias of the onshore converter station according to the second DC voltage and the rated DC voltage; The operation of the onshore converter station is controlled using the optimal DC current reference value and the DC bias.

2. The control method of the deep sea wind power series multi-terminal direct current transmission system according to claim 1, characterized in that: Determining the DC offset of the onshore converter station according to the second DC voltage and the rated DC voltage includes: obtaining the DC offset of the onshore converter station using an offset calculation formula according to the second DC voltage and the rated DC voltage, wherein the offset calculation formula is: Where U dc is the second DC voltage, U dc_rate is the rated DC voltage, and A is the DC bias.

3. The control method of the deep sea wind power series multi-terminal direct current transmission system according to claim 1, characterized in that: include: The first DC voltage corresponding to the offshore converter station is obtained by calculation based on the DC current and the output power of each offshore converter station.

4. The control method of the deep sea wind power series multi-terminal direct current transmission system according to claim 3, characterized in that: include: Under the condition that the first DC voltage is not greater than the rated operating voltage of the corresponding offshore converter station, the minimum allowable DC current of the corresponding offshore converter station is obtained by calculating according to the output power and the rated operating voltage of each offshore converter station.

5. A control device for a series multi-terminal DC transmission system for deep-sea wind power, applied to a series multi-terminal DC transmission system, characterized in that: The series multi-terminal direct current transmission system includes an onshore converter station and n serially connected offshore converter stations, and the control device includes a data acquisition module, a first calculation module, a second calculation module and a control module; The data acquisition module is configured to acquire the rated DC voltage and DC current of the onshore converter station and the rated operating voltage and maximum power point tracking-based output power of each offshore converter station; The first calculation module is configured to calculate, based on the output power and rated operating voltage of each offshore converter station, a minimum allowable DC current of the corresponding offshore converter station, and select the largest value from the n minimum allowable DC currents as the optimal DC current reference value of the onshore converter station; The second calculation module is configured to obtain a second DC voltage of the DC line port of the onshore converter station in real time, and determine a DC bias of the onshore converter station according to the second DC voltage and the rated DC voltage; The control module is used to control the operation of the onshore converter station by using the optimal DC current reference value and the DC bias.

6. The control device for a deep sea wind power series multi-terminal direct current transmission system according to claim 5, characterized in that: A third calculation module is included, and the third calculation module is used to calculate according to the direct current and the output power of each offshore converter station to obtain the first direct current voltage corresponding to the offshore converter station.

7. The control device for a deep sea wind power series multi-terminal direct current transmission system according to claim 6, characterized in that: The first calculation module is further configured to calculate the minimum allowable DC current of the corresponding offshore converter station according to the output power and rated operating voltage of each offshore converter station, based on the condition that the first DC voltage is not greater than the rated operating voltage of the corresponding offshore converter station.

8. The control device for a deep sea wind power series multi-terminal direct current transmission system according to claim 5, characterized in that: The second calculation module is further configured to obtain a DC offset of the onshore converter station using an offset calculation formula according to the second DC voltage and the rated DC voltage, wherein the offset calculation formula is: Where U dc is the second DC voltage, U dc_rate is the rated DC voltage, and A is the DC bias.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium is used to store computer instructions, which, when executed on a computer, enable the computer to execute the control method for a deep-sea wind power series multi-terminal direct current transmission system according to any one of claims 1 to 4.

10. A terminal device, characterized in that: including a processor and a memory; The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the control method for the deep-sea wind power series multi-terminal direct current transmission system according to any one of claims 1 to 4 according to the instructions in the program code.

Images