Offshore wind power flexible low-frequency power transmission system and multi-mode control method, control protection device and test method thereof

Abstract

The invention relates to an offshore wind power flexible low-frequency power transmission system and a multi-mode control method, a control protection device and a test method thereof, the multi-mode control method, the control protection device and the test method are applied to the offshore wind power flexible low-frequency power transmission system, and the multi-mode control method comprises the steps of obtaining an operation mode of the offshore wind power flexible low-frequency power transmission system; controlling the operation of the offshore wind power flexible low-frequency power transmission system according to the operation mode; the operation modes comprise a static synchronous compensator operation mode, a voltage source converter single-machine operation mode, a single-machine operation mode, a parallel operation mode and a shutdown mode. According to the multi-mode control method, the operation of the offshore wind power flexible low-frequency power transmission system is controlled according to the operation mode, so that the offshore wind power flexible low-frequency power transmission system is smoothly started between the first current conversion sub-module and the second current conversion sub-module, the power transfer and the operation mode are flexibly switched, and economical power transmission without an offshore current conversion platform is realized; the power transmission cost is reduced, and the economical efficiency and reliability of the offshore wind power flexible low-frequency power transmission system are improved.

Description

Technical Field

[0001] This application relates to the field of DC power transmission technology, and in particular to a flexible low-frequency power transmission system for offshore wind power and its multi-mode control method, control and protection device and test method. Background Technology

[0002] With the increasing global demand for clean energy, offshore wind power, with its abundant resources and high power generation efficiency, is gradually becoming an important direction for global energy transformation. However, as offshore wind power development continues, long-distance, large-capacity transmission of offshore wind power has become a critical issue that urgently needs to be addressed. Currently, offshore wind power is mainly integrated into onshore power frequency systems through three methods: high-voltage AC transmission, flexible DC transmission, and low-frequency AC transmission, forming offshore wind power transmission systems. Compared with high-frequency AC transmission systems, low-frequency transmission in offshore wind power transmission systems significantly reduces reactive power charging along submarine cables by lowering the transmission frequency, thereby significantly improving transmission capacity. DC transmission, on the other hand, has high construction costs and is difficult to operate and maintain. Compared with flexible DC transmission, the low-frequency wind energy output from the wind turbine converter is directly transmitted to the onshore converter station and then integrated into the grid through transmission lines, eliminating the need for additional offshore converter stations and platforms, saving initial investment and maintenance costs, and showing broad application prospects in the field of offshore wind power transmission.

[0003] Therefore, how to obtain a flexible low-frequency power transmission method for offshore wind power that overcomes the difficulties of long-distance transmission and the high cost of offshore converter platforms in traditional flexible DC and AC power transmission schemes is an issue that needs attention. Summary of the Invention

[0004] This application provides a flexible low-frequency power transmission system for offshore wind power and its multi-modal control method, control and protection device and test method, which are used to solve the technical problems of long-distance transmission difficulties and high cost of offshore converter platforms in traditional flexible DC and AC power transmission schemes.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] In a first aspect, a flexible low-frequency power transmission system for offshore wind power is provided, comprising a low-frequency power transmission module, a DC power transmission module, and a power frequency power transmission module connected in sequence. The low-frequency power transmission module includes a wind farm station with multiple wind turbines connected in parallel. The DC power transmission module includes a first converter submodule and a second converter submodule connected in parallel with the first converter submodule. The first converter submodule includes a converter valve composed of a diode rectifier and a modular multilevel converter. The second converter submodule includes a voltage source converter.

[0007] Secondly, a multi-modal control method for a flexible low-frequency transmission system for offshore wind power is provided, including the following steps:

[0008] Obtain the operating mode of the offshore wind power flexible low-frequency transmission system described above;

[0009] The operation of the offshore wind power flexible low-frequency power transmission system is controlled according to the operating mode.

[0010] The operating modes include static synchronous compensator operating mode, voltage source converter single-unit operating mode, single-unit operating mode, parallel operating mode, and shutdown mode.

[0011] Preferably, controlling the operation of the offshore wind power flexible low-frequency transmission system according to the operating mode includes:

[0012] If the operating mode is the static synchronous compensator operating mode, the wind farm station is stopped and the modular multilevel converter of the first converter submodule is unlocked to send reactive power to the power frequency transmission module in static synchronous compensator operating mode:

[0013] If the operating mode is the voltage source converter single-unit operating mode, the circuit between the wind farm station and the second converter submodule is connected, and power is transmitted to the power frequency transmission module only through the second converter submodule.

[0014] If the operating mode is a single-machine operating mode, the circuit between the wind farm station and the first converter submodule is connected, and power is transmitted to the power frequency transmission module only through the first converter submodule.

[0015] If the operating mode is a parallel operating mode, the circuit between the wind farm station and the first converter submodule and the circuit between the wind farm station and the second converter submodule are connected, and electrical energy is transmitted to the power frequency transmission module through both the first converter submodule and the second converter submodule.

[0016] If the operating mode is the shutdown mode, the wind farm station, the first converter submodule and the second converter submodule are controlled to stop working and not transmit power to the power frequency transmission module.

[0017] Secondly, a control and protection device for a flexible low-frequency transmission system for offshore wind power is provided, which is applied to the flexible low-frequency transmission system for offshore wind power as described in claim 1. The control and protection system includes: a real-time simulation module and an interface module.

[0018] The interface module is used to connect the real-time simulation module with the offshore wind power flexible low-frequency transmission system.

[0019] The real-time simulation module is used to simulate various faults of the offshore wind power flexible low-frequency transmission system, and to control the operation of the offshore wind power flexible low-frequency transmission system according to the multi-modal control method of the offshore wind power flexible low-frequency transmission system described above.

[0020] Preferably, the real-time simulation module includes a real-time digital simulator and a control submodule;

[0021] The real-time digital simulator is used to simulate various faults of various power equipment in the offshore wind power flexible low-frequency transmission system and obtain simulation data.

[0022] The control submodule is used to control the operation of the offshore wind power flexible low-frequency transmission system and protect it according to the multi-modal control method of the offshore wind power flexible low-frequency transmission system described above.

[0023] The control submodule includes a first protection controller, a second protection controller, a third protection controller, a fourth protection controller, and a fifth protection controller.

[0024] The first protection controller is used to control and protect the converter in the wind farm station;

[0025] The second protection controller is used for coordinated control of the converter valve, low-frequency protection, and valve control protection of the energy-consuming valve;

[0026] The third protection controller is used to provide valve-controlled protection for the diode rectifier;

[0027] The fourth protection controller is used for valve-controlled protection of the modular multilevel converter;

[0028] The fifth protection controller is used to control and protect the monitoring equipment, recording equipment, and interface equipment of the offshore wind power flexible low-frequency transmission system.

[0029] Preferably, the interface module includes: an optical fiber communication interface and an Ethernet electrical interface;

[0030] The optical fiber communication interface is used to transmit the control signal output by the real-time simulation module to the offshore wind power flexible low-frequency transmission system via optical signal;

[0031] The Ethernet interface is used to connect the real-time digital simulator of the real-time simulation module to the first protection controller of the offshore wind power flexible low-frequency transmission system via electrical signals.

[0032] Fourthly, a real-time test method for the control and protection of an offshore wind power flexible low-frequency transmission system is provided, applied to the control and protection device of the aforementioned offshore wind power flexible low-frequency transmission system. This real-time test method includes the following steps:

[0033] To determine the test type of the control and protection device of the offshore wind power flexible low-frequency transmission system;

[0034] The control and protection device of the offshore wind power flexible low-frequency transmission system was tested according to the test type, and the test results were obtained.

[0035] Preferably, the test types include sequential control and interlocking tests, power frequency / low frequency side equipment charging tests, no-load / load pressurization tests, power control and regulation tests, fault ride-through tests, and protection function tests.

[0036] Preferably, the sequential control and interlocking test is used to verify whether the start-up, stop, and isolation operation sequence and interlocking relationship of each part of the offshore wind power flexible low-frequency transmission system are normal; the power frequency / low-frequency side equipment charging test is used to verify whether the voltage, current, and power of the offshore wind power flexible low-frequency transmission system meet the requirements during the charging process; the no-load / load pressurization test is used to verify whether the offshore wind power flexible low-frequency transmission system operates stably under no-load and load conditions, and obtains the required voltage, frequency, and power; the power control and regulation test is used to verify the control and regulation capabilities of the offshore wind power flexible low-frequency transmission system for active and reactive power; the fault ride-through test is used to simulate various types of faults on the power frequency and low-frequency sides, and verify whether the control and protection devices controlling the offshore wind power flexible low-frequency transmission system can quickly detect and isolate faults; the protection function test is used to test the various protection functions of the control and protection devices of the offshore wind power flexible low-frequency transmission system.

[0037] Fifthly, a terminal device is provided, including a processor and a memory;

[0038] The memory is used to store program code and transmit the program code to the processor;

[0039] The processor is used to execute the multi-modal control method of the offshore wind power flexible low-frequency transmission system described above according to the instructions in the program code.

[0040] The offshore wind power flexible low-frequency transmission system and its multi-mode control method, control and protection device and test method include obtaining the above-mentioned operating modes of the offshore wind power flexible low-frequency transmission system; controlling the operation of the offshore wind power flexible low-frequency transmission system according to the operating modes; wherein, the operating modes include static synchronous compensator operating mode, voltage source converter single unit operating mode, single unit operating mode, parallel operation mode and shutdown mode.

[0041] As can be seen from the above technical solutions, this application has the following advantages: The multi-mode control method of the offshore wind power flexible low-frequency transmission system obtains the operating mode of the offshore wind power flexible low-frequency transmission system and controls the operation of the offshore wind power flexible low-frequency transmission system according to the operating mode, so that the offshore wind power flexible low-frequency transmission system can smoothly start up, transfer power and flexibly switch operating modes between the first converter submodule and the second converter submodule, realize economical power transmission without offshore converter platform, reduce power transmission cost, improve the economy and reliability of offshore wind power flexible low-frequency transmission system, and solve the technical problems of long-distance transmission difficulty and high cost of offshore converter platform in traditional flexible DC and AC transmission schemes.

[0042] This offshore wind power flexible low-frequency power transmission system achieves economical power transmission without an offshore converter platform by sequentially connecting a low-frequency power transmission module, a DC power transmission module, and a power frequency power transmission module. It solves the technical problems of long-distance transmission difficulties and high costs of offshore converter platforms that exist in traditional flexible DC and AC power transmission schemes.

[0043] The multi-modal control device of the offshore wind power flexible low-frequency transmission system realizes long-distance power transmission of the system through real-time simulation module and interface module.

[0044] The real-time test method for the control and protection of the offshore wind power flexible low-frequency transmission system verifies the various functions and performance standards of the control and protection device for protecting the offshore wind power flexible low-frequency transmission system according to the test type. This ensures the feasibility of the control and protection device for the offshore wind power flexible low-frequency transmission system and provides technical support for the application of the offshore wind power flexible low-frequency transmission system in the field of large-capacity offshore wind power transmission. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1This is a framework diagram of the offshore wind power flexible low-frequency transmission system described in the embodiments of this application;

[0047] Figure 2 This is a topology diagram of the offshore wind power flexible low-frequency transmission system described in the embodiments of this application;

[0048] Figure 3 This is a flowchart illustrating the steps of the multi-modal control method for the flexible low-frequency transmission system for offshore wind power described in this application embodiment;

[0049] Figure 4 This is a schematic diagram of the control and protection device of the offshore wind power flexible low-frequency transmission system described in the embodiments of this application;

[0050] Figure 5 This is a topology diagram of the control and protection device for the offshore wind power flexible low-frequency transmission system described in the embodiments of this application;

[0051] Figure 6 This is a flowchart illustrating the steps of the real-time test method for control and protection of the offshore wind power flexible low-frequency transmission system described in the embodiments of this application;

[0052] Figure 7 This is a schematic diagram of the terminal device described in an embodiment of this application. Detailed Implementation

[0053] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0054] In the description of the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0055] In the embodiments of this application, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0056] This application provides a flexible low-frequency power transmission system for offshore wind power, along with its multi-modal control method, control and protection device, and testing method. It solves the technical problems of long-distance transmission difficulties and high costs of offshore converter platforms in traditional flexible DC and AC power transmission schemes.

[0057] Example 1:

[0058] Figure 1 This is a framework diagram of the offshore wind power flexible low-frequency transmission system described in the embodiments of this application. Figure 2 This is a topology diagram of the offshore wind power flexible low-frequency transmission system described in the embodiments of this application.

[0059] like Figure 1 and Figure 2 As shown in the figure, this application provides a flexible low-frequency power transmission system for offshore wind power, including a low-frequency power transmission module 10, a DC power transmission module 20 and a power frequency power transmission module 30 connected in sequence. The low-frequency power transmission module 10 includes a wind farm station with multiple wind turbines connected in parallel. The DC power transmission module 20 includes a first converter submodule 21 and a second converter submodule 22 connected in parallel with the first converter submodule 21. The first converter submodule 21 includes a converter valve composed of a diode rectifier and a modular multilevel converter. The second converter submodule 22 includes a voltage source converter (VSC).

[0060] It should be noted that, as Figure 2 As shown, the low-frequency transmission module 10 includes multiple wind turbines connected in parallel and equipped with energy storage. The wind turbines convert the current into medium-voltage, low-frequency current via a 20Hz low-frequency transformer, and then transmit it to the DC transmission module 20 via a transmission line (which also includes an AC filter and AC energy dissipation device). The DC transmission module 20 converts the AC voltage and current transmitted from the low-frequency transmission module 10 into DC voltage and DC current output, and then transmits the DC voltage and DC current to the power frequency transmission module 30. The power frequency transmission module 30 transmits the electrical energy containing DC voltage and DC current to the power grid via a medium-voltage / 50Hz transmission line.

[0061] This application provides a flexible low-frequency power transmission system for offshore wind power, comprising a low-frequency transmission module, a DC transmission module, and a power frequency transmission module connected in sequence. The low-frequency transmission module includes a wind farm station with multiple wind turbines connected in parallel. The DC transmission module includes a first converter submodule and a second converter submodule connected in parallel with the first converter submodule. The first converter submodule includes a converter valve composed of a diode rectifier and a modular multilevel converter. The second converter submodule includes a voltage source converter. This flexible low-frequency power transmission system for offshore wind power achieves economical power transmission without an offshore converter platform by connecting the low-frequency transmission module, DC transmission module, and power frequency transmission module in sequence, solving the technical problems of long-distance transmission difficulties and high costs of offshore converter platforms in traditional flexible DC and AC power transmission schemes.

[0062] Example 2:

[0063] Figure 3 This is a flowchart illustrating the steps of the multimodal control method for the offshore wind power flexible low-frequency transmission system described in this application embodiment.

[0064] like Figure 3 As shown in the figure, this application provides a multi-mode control method for a flexible low-frequency transmission system for offshore wind power, including the following steps:

[0065] S1. Obtain the operating mode of the above-mentioned offshore wind power flexible low-frequency transmission system.

[0066] It should be noted that the content of the offshore wind power flexible low-frequency transmission system has been described in Embodiment 1, and will not be described again in this embodiment. In step S1, the operating mode of the offshore wind power flexible low-frequency transmission system is obtained to provide data for subsequent steps. In this embodiment, the operating modes include static synchronous compensator operating mode, voltage source converter single-unit operating mode, single-unit operating mode, parallel operating mode, and shutdown mode.

[0067] S2. Control the operation of the offshore wind power flexible low-frequency transmission system according to the operating mode.

[0068] It should be noted that in step S2, the operation of the offshore wind power flexible low-frequency transmission system is controlled according to the operating mode obtained in step S1. This allows the offshore wind power flexible low-frequency transmission system to overcome the difficulties of long-distance transmission and the high cost of offshore converter platforms that exist in traditional flexible DC and AC transmission schemes, achieving economical power transmission without an offshore converter platform. The multi-mode control method of this offshore wind power flexible low-frequency transmission system can support both grid-connected and grid-following wind turbine control modes, realizing smooth start-up, power transfer, and flexible switching of operating modes between the first and second converter submodules, greatly improving the economy and reliability of the offshore wind power flexible low-frequency transmission system.

[0069] This application provides a multi-modal control method for an offshore wind power flexible low-frequency transmission system, comprising acquiring the operating modes of the offshore wind power flexible low-frequency transmission system; and controlling the operation of the offshore wind power flexible low-frequency transmission system according to the operating modes. The operating modes include a static synchronous compensator operating mode, a voltage source converter single-unit operating mode, a single-unit operating mode, a parallel operating mode, and a shutdown mode. This multi-modal control method for the offshore wind power flexible low-frequency transmission system, by acquiring the operating modes of the offshore wind power flexible low-frequency transmission system and controlling its operation according to the operating modes, enables smooth start-up, power transfer, and flexible switching of operating modes between the first and second converter submodules. This achieves economical power transmission without an offshore converter platform, reduces transmission costs, improves the economy and reliability of the offshore wind power flexible low-frequency transmission system, and solves the technical problems of long-distance transmission difficulties and high costs of offshore converter platforms in traditional flexible DC and AC transmission schemes.

[0070] In one embodiment of this application, controlling the operation of an offshore wind power flexible low-frequency transmission system according to an operating mode includes:

[0071] If the operating mode is the static synchronous compensator operating mode, the control wind farm station stops operating and the control of the modular multilevel converter of the first converter submodule unlocks the power frequency transmission module to send reactive power to the power frequency transmission module in static synchronous compensator operating mode:

[0072] If the operating mode is the voltage source converter single-unit operation mode, the circuit between the control wind farm station and the second converter submodule is connected, and power is transmitted to the power frequency transmission module only through the second converter submodule;

[0073] If the operating mode is single-unit operation mode, the circuit between the control wind farm station and the first converter submodule is connected, and power is transmitted to the power frequency transmission module only through the first converter submodule.

[0074] If the operating mode is parallel operation mode, the circuit between the control wind farm station and the first converter submodule and the circuit between the control wind farm station and the second converter submodule are connected, and power is transmitted to the power frequency transmission module through both the first converter submodule and the second converter submodule;

[0075] If the operating mode is shutdown mode, the control wind power station, the first converter submodule and the second converter submodule will stop working and will not transmit power to the power frequency transmission module.

[0076] It should be noted that in the STATCOM (Static Synchronous Compensator) operation mode, the wind farm station in the offshore wind power flexible low-frequency transmission system is shut down, and the modular multilevel converter is unlocked in STATCOM operation mode, sending reactive power to the onshore power frequency transmission module 30. In the VSC (Voltage Source Converter) single-unit operation mode, the primary circuit of the wind farm station is only connected to the second converter submodule containing the VSC, and transmits power to the onshore power frequency transmission module 30 through the second converter submodule of the VSC. In the single-unit operation mode, the primary circuit of the wind farm station is only connected to the first converter submodule containing the converter valve, and transmits power to the onshore power frequency transmission module 30 through the first converter submodule containing the converter valve. In the parallel operation mode, the primary circuit of the wind farm station is connected to both the first converter submodule containing the converter valve and the second converter submodule containing the VSC, and can transmit power to the onshore power frequency transmission module 30 through both. In the shutdown mode, the control wind turbine station, converter valve, and voltage source converter (VSC) are all shut down, and no power is transmitted to the onshore power frequency transmission module 30. In this embodiment, the multi-mode control method of the offshore wind power flexible low-frequency transmission system controls the operation of the offshore wind power flexible low-frequency transmission system through different operating modes, realizing the long-distance power transmission of the offshore wind power flexible low-frequency transmission system.

[0077] Example 3:

[0078] Figure 4 This is a schematic diagram of the control and protection device of the offshore wind power flexible low-frequency transmission system described in the embodiments of this application.

[0079] like Figure 4 As shown in the figure, this application provides a control and protection device for a flexible low-frequency transmission system for offshore wind power, which is applied to the above-mentioned flexible low-frequency transmission system for offshore wind power. The control and protection system includes a real-time simulation module 100 and an interface module 200.

[0080] It should be noted that the content of the offshore wind power flexible low-frequency transmission system has been described in Embodiment 1, and will not be described again in this embodiment.

[0081] like Figure 4 As shown in the embodiments of this application, the interface module 200 is used to establish a communication connection between the real-time simulation module 100 and the offshore wind power flexible low-frequency transmission system. The control and protection device of the offshore wind power flexible low-frequency transmission system realizes the communication connection between the simulation equipment and the offshore wind power flexible low-frequency transmission system through the interface module 200.

[0082] like Figure 4As shown in the embodiments of this application, the real-time simulation module 100 is used to simulate various faults of the offshore wind power flexible low-frequency transmission system, and to control the operation of the offshore wind power flexible low-frequency transmission system according to the multi-modal control method of the offshore wind power flexible low-frequency transmission system described above.

[0083] It should be noted that the multimodal control method for the offshore wind power flexible low-frequency transmission system has already been described in Embodiment 2, and will not be described again in this embodiment. In this embodiment, the real-time simulation module 1001 simulates various faults of the offshore wind power flexible low-frequency transmission system, obtains simulation data, and provides protection data for the control of the offshore wind power flexible low-frequency transmission system based on the simulation data. The real-time simulation module 1002 controls the operation of the offshore wind power flexible low-frequency transmission system according to the multimodal control method, realizing long-distance power transmission of the offshore wind power flexible low-frequency transmission system at low cost.

[0084] Figure 5 This is a topology diagram of the control and protection device for the offshore wind power flexible low-frequency transmission system described in the embodiments of this application.

[0085] like Figure 5 As shown, in one embodiment of this application, the real-time simulation module 100 includes a real-time digital simulator and a control submodule;

[0086] A real-time digital simulator is used to simulate various faults of various power equipment in offshore wind power flexible low-frequency transmission systems and obtain simulation data.

[0087] The control submodule is used to control the operation of the offshore wind power flexible low-frequency transmission system and protect it according to the multi-mode control method of the offshore wind power flexible low-frequency transmission system described above.

[0088] The control submodule includes a first protection controller, a second protection controller, a third protection controller, a fourth protection controller, and a fifth protection controller.

[0089] The first protection controller is used to control and protect the converter in the wind farm station;

[0090] The second protection controller is used for coordinated control of the converter valve, low-frequency protection, and valve control protection of the energy-consuming valve.

[0091] The third protection controller is used for valve-controlled protection of the diode rectifier;

[0092] The fourth protection controller is used for valve-controlled protection of the modular multilevel converter;

[0093] The fifth protection controller is used to control and protect the monitoring equipment, recording equipment, and interface equipment of the offshore wind power flexible low-frequency transmission system.

[0094] It should be noted that the real-time digital simulator is used to simulate various possible faults in the offshore wind power flexible low-frequency transmission system, including the power frequency transmission module, the starting circuit model of the modular multilevel converter, the modular multilevel converter connecting transformer model, the equivalent model of the modular multilevel converter, the equivalent model of the diode rectifier, the equivalent model of the diode rectifier connecting transformer, the equivalent model of the voltage source converter, the low-frequency filter branch model, the energy consumption device model, the low-frequency cable model, the equivalent model of the grid-type wind turbine, and all primary equipment such as switches and disconnectors. The control submodule is used to control the actual operation of the offshore wind power flexible low-frequency transmission system. The control submodule includes a first protection controller for implementing the grid-type wind turbine converter control and protection system, a second protection controller for implementing the low-frequency station control system, a third protection controller for implementing the diode rectifier-based valve control and protection system, a fourth protection controller for implementing the modular multilevel converter control and protection system, and a fifth protection controller for implementing the monitoring system and fault recording system. The first protection controller includes the wind turbine converter control and protection equipment. The second protection controller includes converter valve coordination control equipment, low-frequency protection equipment, and energy-consuming valve control equipment. The fourth protection controller includes the unit controller of the modular multilevel converter and the valve control equipment of the modular multilevel converter. The monitoring system includes a single monitoring system server, a single monitoring network interface device, and synchronization time synchronization equipment. The fault recording system includes low-frequency AC field recording equipment, DC transmission unit recording equipment, wind turbine converter recording equipment, and VSC recording equipment.

[0095] like Figure 5 As shown, in one embodiment of this application, the interface module 200 includes: an optical fiber communication interface and an Ethernet electrical interface;

[0096] The fiber optic communication interface is used to transmit the control signals output by the real-time simulation module to the offshore wind power flexible low-frequency transmission system via optical signals.

[0097] An Ethernet electrical interface is used to connect the real-time digital simulator of the real-time simulation module to the first protection controller of the offshore wind power flexible low-frequency transmission system via electrical signals.

[0098] It should be noted that optical signals are used for data transmission between the real-time digital simulator and the second protection controller. Through the fiber optic communication interface, the real-time digital simulator outputs the status, capacitor voltage, and arm current of all power submodules in the modular multilevel converter, and obtains control signals for the power submodules from the valve control equipment. Electrical signals are used to establish the communication connection between the real-time digital simulator and the first protection controller in the offshore wind power flexible low-frequency transmission system.

[0099] Example 4:

[0100] Figure 6 This is a flowchart illustrating the steps of the real-time test method for the control and protection of the offshore wind power flexible low-frequency transmission system described in this application embodiment.

[0101] This application provides a real-time test method for the control and protection of a flexible low-frequency transmission system for offshore wind power, which is applied to the control and protection device of the aforementioned flexible low-frequency transmission system for offshore wind power.

[0102] It should be noted that the control and protection device of the offshore wind power flexible low-frequency transmission system has been described in Embodiment 3, and the content of the control and protection device of the offshore wind power flexible low-frequency transmission system will not be described in this embodiment.

[0103] like Figure 6 As shown, the real-time test method for the control and protection of the offshore wind power flexible low-frequency transmission system includes the following steps:

[0104] S01. Test type of control and protection device for offshore wind power flexible low-frequency transmission system.

[0105] It should be noted that step S01 involves obtaining the test type to provide data for subsequent steps. Test types include sequential control and interlocking tests, power frequency / low frequency side equipment charging tests, no-load / load pressurization tests, power control and regulation tests, fault ride-through tests, and protection function tests.

[0106] S02. Test the control and protection devices of the offshore wind power flexible low-frequency transmission system according to the test type, and obtain the test results.

[0107] It should be noted that step S02 verifies the various functions and performance standards of the control and protection device for the offshore wind power flexible low-frequency transmission system according to the test type, ensuring the feasibility of the control and protection device for the offshore wind power flexible low-frequency transmission system and providing technical support for the application of the offshore wind power flexible low-frequency transmission system in the field of large-capacity offshore wind power transmission.

[0108] In the embodiments of this application, the sequential control and interlocking test is used to verify whether the start-up, stop, and isolation operation sequence and interlocking relationship of each part of the offshore wind power flexible low-frequency transmission system are normal; the power frequency / low-frequency side equipment charging test is used to verify whether the voltage, current, and power of the offshore wind power flexible low-frequency transmission system meet the requirements during the charging process; the no-load / load pressurization test is used to verify whether the offshore wind power flexible low-frequency transmission system operates stably under no-load and load conditions, and obtains the required voltage, frequency, and power; the power control and regulation test is used to verify the control and regulation capabilities of the offshore wind power flexible low-frequency transmission system for active and reactive power; the fault ride-through test is used to simulate various types of faults on the power frequency and low-frequency sides to verify whether the control and protection devices controlling the offshore wind power flexible low-frequency transmission system can quickly detect and isolate faults; the protection function test is used to test the various protection functions of the control and protection devices of the offshore wind power flexible low-frequency transmission system. In this embodiment,

[0109] It should be noted that the sequence control and interlocking tests are used to verify whether the start-up, shutdown, isolation, and other operational sequences and interlocking relationships of various parts of the offshore wind power flexible low-frequency transmission system are normal. The power frequency / low-frequency side equipment charging test is used to verify whether the voltage, current, power, and other parameters of the offshore wind power flexible low-frequency transmission system meet the requirements during the charging process. The no-load / load pressurization test is used to verify whether the offshore wind power flexible low-frequency transmission system can operate stably under no-load and load conditions, and whether the output voltage, frequency, power, and other parameters meet the requirements under stable operation. The power control and regulation test verifies the offshore wind power flexible low-frequency transmission system's ability to control and regulate active and reactive power, thereby verifying its ability to support the grid voltage and frequency. In the fault ride-through test, various types of faults occur on the power frequency and low frequency sides to verify whether the control and protection devices of the offshore wind power flexible low-frequency transmission system can quickly detect and isolate faults, and ensure that the offshore wind power flexible low-frequency transmission system can quickly resume normal operation after the fault is cleared. In the protection function test, various protection functions of the control and protection devices of the offshore wind power flexible low-frequency transmission system are tested, such as overcurrent protection, overvoltage protection, undervoltage ride-through, and oscillation suppression.

[0110] Example 5:

[0111] Figure 7 This is a schematic diagram of the terminal device described in an embodiment of this application.

[0112] like Figure 7 As shown, this application provides a terminal device, including a processor and a memory;

[0113] Memory is used to store program code and transfer the program code to the processor;

[0114] The processor is used to execute the multi-modal control method of the offshore wind power flexible low-frequency transmission system according to the instructions in the program code.

[0115] It should be noted that the processor is used to execute the steps in the above-described embodiment of a multimodal control method for a flexible low-frequency transmission system for offshore wind power, according to the instructions in the program code. Alternatively, when the processor executes the computer program, it implements the functions of each module / unit in the above-described system / device embodiments.

[0116] For example, a computer program can be divided into one or more modules / units, one or more of which are stored in memory and executed by a processor to complete this application. One or more modules / units can be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in a terminal device.

[0117] Terminal devices can be computing devices such as desktop computers, laptops, handheld computers, and cloud servers. Terminal devices may include, but are not limited to, processors and memory. Those skilled in the art will understand that this does not constitute a limitation on the terminal device, which may include more or fewer components than illustrated, or combinations of certain components, or different components. For example, a terminal device may also include input / output devices, network access devices, buses, etc.

[0118] The processor referred to can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0119] Memory can be an internal storage unit of a terminal device, such as a hard drive or RAM. Memory can also be an external storage device, such as a plug-in hard drive, SmartMedia Card (SMC), Secure Digital (SD) card, or Flash 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 will be output.

[0120] 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.

[0121] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between apparatuses or units through some interfaces, and may be electrical, mechanical, or other forms.

[0122] The units described as separate components may or may not be physically separate. 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 the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0123] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0124] If the integrated unit is implemented as 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 invention, in essence, 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. 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.

[0125] 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 flexible low-frequency power transmission system for offshore wind power, characterized in that, The system includes a low-frequency power transmission module, a DC power transmission module, and a power frequency power transmission module connected in sequence. The low-frequency power transmission module includes a wind farm station with multiple wind turbines connected in parallel. The DC power transmission module includes a first converter submodule and a second converter submodule connected in parallel with the first converter submodule. The first converter submodule includes a converter valve composed of a diode rectifier and a modular multilevel converter. The second converter submodule includes a voltage source converter.

2. A multi-modal control method for a flexible low-frequency transmission system for offshore wind power, characterized in that, Includes the following steps: Obtain the operating mode of the offshore wind power flexible low-frequency transmission system as described in claim 1; The operation of the offshore wind power flexible low-frequency power transmission system is controlled according to the operating mode. The operating modes include static synchronous compensator operating mode, voltage source converter single-unit operating mode, single-unit operating mode, parallel operating mode, and shutdown mode.

3. The multi-mode control method for a flexible low-frequency transmission system for offshore wind power according to claim 2, characterized in that, Controlling the operation of the offshore wind power flexible low-frequency transmission system according to the aforementioned operating mode includes: If the operating mode is the static synchronous compensator operating mode, the wind farm station is stopped and the modular multilevel converter of the first converter submodule is unlocked to send reactive power to the power frequency transmission module in static synchronous compensator operating mode: If the operating mode is the voltage source converter single-unit operating mode, the circuit between the wind farm station and the second converter submodule is connected, and power is transmitted to the power frequency transmission module only through the second converter submodule. If the operating mode is a single-machine operating mode, the circuit between the wind farm station and the first converter submodule is connected, and power is transmitted to the power frequency transmission module only through the first converter submodule. If the operating mode is a parallel operating mode, the circuit between the wind farm station and the first converter submodule and the circuit between the wind farm station and the second converter submodule are connected, and electrical energy is transmitted to the power frequency transmission module through both the first converter submodule and the second converter submodule. If the operating mode is the shutdown mode, the wind farm station, the first converter submodule and the second converter submodule are controlled to stop working and not transmit power to the power frequency transmission module.

4. A control and protection device for an offshore wind power flexible low-frequency transmission system, applied to the offshore wind power flexible low-frequency transmission system as described in claim 1, characterized in that, The control and protection system includes: a real-time simulation module and an interface module; The interface module is used to connect the real-time simulation module with the offshore wind power flexible low-frequency transmission system. The real-time simulation module is used to simulate various faults of the offshore wind power flexible low-frequency transmission system, and to control the operation of the offshore wind power flexible low-frequency transmission system according to the multi-modal control method of the offshore wind power flexible low-frequency transmission system as described in claim 2 or 3.

5. The control and protection device for the offshore wind power flexible low-frequency transmission system according to claim 4, characterized in that, The real-time simulation module includes a real-time digital simulator and a control submodule; The real-time digital simulator is used to simulate various faults of various power equipment in the offshore wind power flexible low-frequency transmission system and obtain simulation data. The control submodule is used to control the operation of the offshore wind power flexible low-frequency transmission system for protection according to the multi-modal control method of the offshore wind power flexible low-frequency transmission system as described in claim 2 or 3. The control submodule includes a first protection controller, a second protection controller, a third protection controller, a fourth protection controller, and a fifth protection controller. The first protection controller is used to control and protect the converter in the wind farm station; The second protection controller is used for coordinated control of the converter valve, low-frequency protection, and valve control protection of the energy-consuming valve; The third protection controller is used to provide valve-controlled protection for the diode rectifier; The fourth protection controller is used for valve-controlled protection of the modular multilevel converter; The fifth protection controller is used to control and protect the monitoring equipment, recording equipment, and interface equipment of the offshore wind power flexible low-frequency transmission system.

6. The control and protection device for the offshore wind power flexible low-frequency transmission system according to claim 4, characterized in that, The interface module includes: an optical fiber communication interface and an Ethernet electrical interface; The optical fiber communication interface is used to transmit the control signal output by the real-time simulation module to the offshore wind power flexible low-frequency transmission system via optical signal; The Ethernet interface is used to connect the real-time digital simulator of the real-time simulation module to the first protection controller of the offshore wind power flexible low-frequency transmission system via electrical signals.

7. A real-time test method for the control and protection of an offshore wind power flexible low-frequency transmission system, applied to the control and protection device of the offshore wind power flexible low-frequency transmission system as described in claim 4, characterized in that, The real-time test method for control and protection includes the following steps: To determine the test type of the control and protection device of the offshore wind power flexible low-frequency transmission system; The control and protection device of the offshore wind power flexible low-frequency transmission system was tested according to the test type, and the test results were obtained.

8. The real-time test method for control and protection of the offshore wind power flexible low-frequency transmission system according to claim 7, characterized in that, The test types include sequential control and interlocking tests, power frequency / low frequency side equipment charging tests, no-load / load pressurization tests, power control and regulation tests, fault ride-through tests, and protection function tests.

9. The real-time test method for control and protection of the offshore wind power flexible low-frequency transmission system according to claim 8, characterized in that, The sequential control and interlocking test is used to verify whether the start-up, stop, and isolation operation sequence and interlocking relationship of each part of the offshore wind power flexible low-frequency transmission system are normal; the power frequency / low-frequency side equipment charging test is used to verify whether the voltage, current, and power of the offshore wind power flexible low-frequency transmission system meet the requirements during the charging process; the no-load / load pressurization test is used to verify whether the offshore wind power flexible low-frequency transmission system operates stably under no-load and load conditions, and obtains the required voltage, frequency, and power; the power control and regulation test is used to verify the control and regulation capabilities of the offshore wind power flexible low-frequency transmission system for active and reactive power; the fault ride-through test is used to simulate various types of faults on the power frequency and low-frequency sides to verify whether the control and protection devices controlling the offshore wind power flexible low-frequency transmission system can quickly detect and isolate faults; the protection function test is used to test the various protection functions of the control and protection devices of the offshore wind power flexible low-frequency transmission system.

10. A terminal device, characterized in that, Including the processor and memory; The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the multimodal control method for the offshore wind power flexible low-frequency transmission system as described in claim 2 or 3, according to the instructions in the program code.

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