AC fault control method and device for coordinated converter and flexible DC system

Abstract

The present disclosure proposes an AC fault control method and device for the coordination of a converter and a flexible DC system, comprising: in the case of surplus power in the flexible DC transmission system, monitoring the DC voltage value of an onshore converter station of the flexible DC transmission system, and in response to the DC voltage value reaching a voltage threshold, controlling the offshore converter station of the flexible DC transmission system to execute a low-voltage voltage limiting control strategy to reduce the AC bus voltage amplitude of the offshore converter station, and in response to the voltage amplitude dropping to an amplitude lower limit, controlling the grid-side converter of a wind turbine converter system to execute a low-voltage current limiting control strategy to reduce the input power of the flexible DC transmission system. When a minor fault occurs in the system, the reactive power support and overvoltage regulation capabilities of the flexible DC system can be fully utilized without the need for investment in energy-consuming devices, thereby improving the control effect of AC faults.

Description

Technical Field

[0001] The present disclosure relates to the technical field of wind power grid connection, and in particular to an AC fault control method, device and storage medium for coordinated AC power converter and flexible DC system. Background Art

[0002] At present, the grid connection methods for offshore wind power transmission are mainly divided into two categories: high-voltage AC transmission and high-voltage DC transmission. Among them, high-voltage DC transmission adopts flexible DC transmission technology based on voltage source converter. In practical applications, after an onshore AC fault occurs, the AC side active power delivery capacity of the onshore converter station of the flexible DC system decreases. Since the power of the offshore wind farm cannot be fully delivered, a large amount of surplus power appears in the DC system, causing the converter station submodule voltage and inter-pole DC voltage to rise rapidly, which can trigger overvoltage protection in a few milliseconds to tens of milliseconds, causing the system to stop operating.

[0003] In the related technology, AC fault control methods include adopting energy-consuming resistor devices, reducing the power of wind turbines, or adjusting the AC bus voltage amplitude of the offshore sending-end converter station by using the fast adjustment capability of the flexible DC transmission system. However, although the use of energy-consuming resistor devices can effectively consume excess power, the requirements for their resistance parameters are high, and the economy is not high. The demand for fast response speed also makes the investment cost of energy-consuming resistor devices high; and the use of wind turbines to reduce power can also balance the power to a certain extent, but the response speed is too slow; and the adjustment method of the flexible DC transmission system has no obvious effect on serious faults and is very likely to cause wind turbines to be disconnected from the grid. Therefore, the AC fault control method needs to be optimized. Summary of the invention

[0004] The present disclosure proposes an AC fault control method, device and storage medium for coordinated AC converter and flexible DC system, aiming to solve one of the technical problems in the related art at least to a certain extent.

[0005] The first aspect of the present disclosure discloses an AC fault control method for a converter and a flexible DC system in coordination, comprising: in the case of surplus power in the flexible DC transmission system, monitoring the DC voltage value of an onshore converter station of the flexible DC transmission system; in response to the DC voltage value reaching a voltage threshold, controlling the offshore converter station of the flexible DC transmission system to execute a low-voltage voltage limiting control strategy to reduce the AC bus voltage amplitude of the offshore converter station; in response to the voltage amplitude dropping to an amplitude lower limit, controlling the grid-side converter of a wind turbine converter system to execute a low-voltage current limiting control strategy to reduce the input power of the flexible DC transmission system.

[0006] The second aspect of the present disclosure proposes an AC fault control device for cooperating a converter and a flexible DC system, including: a first monitoring module, used to monitor the DC voltage value of an onshore converter station of the flexible DC transmission system when there is surplus power in the flexible DC transmission system; a first control module, used to control the offshore converter station of the flexible DC transmission system to execute a low-voltage limiting control strategy in response to the DC voltage value reaching a voltage threshold, so as to reduce the AC bus voltage amplitude of the offshore converter station; and a second control module, used to control the grid-side converter of the wind turbine converter system to execute a low-voltage current limiting control strategy in response to the voltage amplitude dropping to the lower limit of the amplitude, so as to reduce the input power of the flexible DC transmission system.

[0007] The third aspect of the present disclosure proposes a computer device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the AC fault control method for the coordinated operation of the converter and the flexible DC system of the embodiment of the present disclosure.

[0008] The fourth aspect of the present disclosure provides a non-transitory computer-readable storage medium storing computer instructions, wherein the computer instructions are used to enable the computer to execute the AC fault control method for the coordinated operation of the converter and the flexible DC system disclosed in the embodiment of the present disclosure.

[0009] In this embodiment, when there is surplus power in the flexible DC transmission system, the DC voltage value of the onshore converter station of the flexible DC transmission system is monitored, and in response to the DC voltage value reaching the voltage threshold, the offshore converter station of the flexible DC transmission system is controlled to execute a low-voltage voltage limiting control strategy to reduce the AC bus voltage amplitude of the offshore converter station, and in response to the voltage amplitude dropping to the lower limit of the amplitude, the grid-side converter of the wind turbine converter system is controlled to execute a low-voltage current limiting control strategy to reduce the input power of the flexible DC transmission system. When there is a minor system fault, the reactive power support and overvoltage regulation capabilities of the flexible DC system can be fully utilized without the investment of energy-consuming devices. When there is a serious system fault, sufficient response time is reserved for the investment of energy-consuming devices, which greatly reduces the parameter design requirements and investment costs of energy-consuming devices, thereby improving the control effect of AC faults.

[0010] Additional aspects and advantages of the present disclosure will be given in part in the following description and in part will be obvious from the following description or learned through practice of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above and / or additional aspects and advantages of the present disclosure will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0012] Figure 1 It is a flow chart of an AC fault control method for a converter and a flexible DC system in coordination according to an embodiment of the present disclosure;

[0013] Figure 2 is a schematic diagram of the structure of a wind power generation grid-connected system provided according to an embodiment of the present disclosure;

[0014] Figure 3 is a schematic diagram of an AC fault control device for a converter and a flexible DC system in cooperation according to another embodiment of the present disclosure;

[0015] Figure 4 A block diagram of an exemplary computer device suitable for implementing embodiments of the present disclosure is shown. DETAILED DESCRIPTION

[0016] Embodiments of the present disclosure are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present disclosure, and are not to be construed as limitations of the present disclosure. On the contrary, the embodiments of the present disclosure include all changes, modifications, and equivalents that fall within the spirit and connotation of the appended claims.

[0017] Among them, it should be noted that the executor of the AC fault control method for the converter and the flexible DC system in this embodiment can be an AC fault control device for the converter and the flexible DC system. The device can be implemented by software and / or hardware. The device can be configured in an electronic device, and the electronic device can include but is not limited to a terminal, a server, etc.

[0018] Figure 1 FIG. 1 is a flow chart of an AC fault control method for a converter and a flexible DC system in coordination according to an embodiment of the present disclosure. Figure 1 As shown, the method includes:

[0019] S101: When there is surplus power in the flexible DC transmission system, monitor the DC voltage value of an onshore converter station of the flexible DC transmission system.

[0020] Specifically, Figure 2 is a schematic diagram of the structure of a wind power grid-connected system according to an embodiment of the present disclosure, such as Figure 2As shown, the wind power grid-connected system of this embodiment includes a flexible direct current transmission system (flexible direct current system), a wind turbine converter system (wind turbine converter) and any other possible devices, without limitation. Among them, the flexible direct current transmission system includes an offshore converter station and an onshore converter station, the onshore converter station is connected to the onshore power grid system, and the offshore converter station is connected to the offshore power grid; and the wind turbine converter system includes a machine-side converter and a grid-side converter, the machine-side converter is connected to the wind turbine generator, and the grid-measured converter is connected to the offshore power grid. Regarding the specific structure of the wind power grid-connected system, this embodiment does not limit it.

[0021] In practical applications, the mechanical power generated by a wind farm can be represented by Pm, for example; the input power of a wind power grid-connected system, i.e., the electrical power converted from mechanical power (also called electromagnetic power), can be represented by Pin; the output power of a wind power grid-connected system, i.e., the power connected to the onshore power grid, can be represented by Pout; and the surplus power generated by a wind power grid-connected system (more specifically, a flexible DC transmission system) can be represented by Pec, with the relationship Pin = Pout + Pec. When the system is in steady-state operation without an AC fault on land, Pm = Pin = Pout, and Pec = 0.

[0022] Among them, the offshore converter station of this embodiment adopts a fixed AC voltage and fixed frequency control strategy (also called a control mode), that is, the offshore converter station has a fixed AC voltage and a fixed frequency during steady-state operation, and can also be equipped with a low-voltage voltage limiting and low-voltage frequency regulation control strategy; and the onshore converter station adopts a fixed DC voltage and a fixed reactive power control strategy, that is, the offshore converter station has a fixed AC voltage and a fixed reactive power during steady-state operation, and is also equipped with a low-voltage reactive control strategy; and the machine-side converter adopts a fixed DC voltage and a fixed reactive power control strategy, and the grid-side converter adopts a fixed electromagnetic power and a fixed reactive power control strategy. In addition, the grid-side converter is also equipped with a low-voltage current limiting control strategy.

[0023] In actual applications, after an onshore AC fault occurs, the onshore AC bus voltage will decrease, and the active power delivery capacity of the AC side of the onshore converter station of the flexible DC system will decrease. Since the power of the offshore wind farm cannot be fully delivered, a large amount of surplus power will appear in the DC system, and this surplus power will charge the sub-module capacitors of the flexible DC system, thereby causing the onshore converter station voltage and the inter-pole DC voltage to rise rapidly.

[0024] In view of this, this embodiment can monitor the change of the AC bus voltage of the onshore converter station. After monitoring the decrease of the AC bus voltage, it can be determined whether there is surplus power in the flexible DC transmission system. When it is determined that there is surplus power in the flexible DC transmission system, the DC voltage value of the onshore converter station of the flexible DC transmission system is monitored. The DC voltage value can be expressed as U dcexpress.

[0025] In some embodiments, after monitoring the reduction of the onshore AC bus voltage, the present embodiment can also control the onshore converter station to execute a low-voltage reactive control strategy to increase the reactive power setting value of the onshore converter station, so that the flexible DC transmission system can increase reactive power and maintain the onshore AC bus voltage amplitude, and can give full play to the reactive support of the flexible DC system under AC faults, thereby improving the control effect under fault conditions to a certain extent.

[0026] S102: In response to the DC voltage value reaching a voltage threshold, controlling the offshore converter station of the flexible DC transmission system to execute a low voltage limiting control strategy to reduce the AC bus voltage amplitude of the offshore converter station.

[0027] Furthermore, in this embodiment, the increased DC voltage value U dc Compared with the voltage threshold, if the DC voltage value U dc If the voltage threshold is reached, this embodiment can control the offshore converter station of the flexible DC transmission system to execute the low voltage limiting control strategy to reduce the AC bus voltage amplitude of the offshore converter station.

[0028] In some embodiments, the voltage threshold is, for example, 1.1 times the voltage rating. The voltage rating can be, for example, U dcN In other words, at the DC voltage value U dc =1.1U dcN When the voltage rises to 1.1 times the rated value, the offshore converter station implements the low voltage limiting control strategy to reduce the voltage amplitude of the AC busbar of the offshore converter station. The voltage threshold can be flexibly set according to the actual application scenario and there is no restriction on this.

[0029] In other embodiments, while controlling the offshore converter station of the flexible DC transmission system to execute the low-voltage limiting control strategy, the present embodiment can also control the offshore converter station of the flexible DC transmission system to execute the low-voltage frequency regulation control strategy to increase the system frequency of the offshore converter station. That is to say, the low-voltage limiting and low-voltage frequency regulation control strategies of the offshore converter station act simultaneously to reduce the voltage amplitude of the AC busbar of the offshore station and increase the system frequency.

[0030] S103: In response to the voltage amplitude dropping to the lower amplitude limit, controlling the grid-side converter of the wind turbine converter system to execute a low-voltage current limiting control strategy to reduce the input power of the flexible DC transmission system.

[0031] Furthermore, the present embodiment can compare the voltage amplitude with a preset lower amplitude limit (i.e., the minimum amplitude limit value). When the voltage amplitude drops to the lower amplitude limit, the present embodiment can control the grid-side converter of the wind turbine converter system to execute a low-voltage current limiting control strategy to reduce the DC current of the grid-side converter, thereby reducing the input power Pin of the flexible DC transmission system. That is to say, when the voltage amplitude drops to the lower amplitude limit, the low-voltage current limiting control of the grid-side converter begins to work, limiting the electromagnetic power Pin. Since the mechanical power Pm of the wind farm remains unchanged, Pm>Pin at this time, and the excess energy can be converted into the generator rotor speed ω, which increases from the rated value, thereby absorbing the excess mechanical power, thereby reducing the surplus power Pec of the flexible DC transmission system.

[0032] In some embodiments, an energy dissipation device (e.g., an energy dissipation resistor) may be configured in the flexible direct current transmission system to absorb surplus power, wherein the energy dissipation device may be configured, for example, on the DC side of the onshore converter station. Specifically, this embodiment may monitor the current speed value of the generator rotor in real time; further, the current speed value ω is compared with the speed threshold (the upper limit of the generator rotor speed). If the current speed value ω reaches the speed threshold, it is further determined whether there is still surplus power in the flexible direct current transmission system. If the current speed value reaches the speed threshold and there is surplus power Pec, it indicates that the system is seriously faulty and the surplus power Pec cannot be reduced by the reactive support of the flexible direct current system and the control method provided by the above embodiment. In this case, this embodiment may also control the start-up of the energy dissipation device to absorb the surplus power. Thus, when the system fails seriously, this embodiment may reserve sufficient response time for the energy dissipation device to be put into use, greatly reducing the design requirements and investment costs of the energy dissipation resistor parameters.

[0033] In this embodiment, when there is surplus power in the flexible DC transmission system, the DC voltage value of the onshore converter station of the flexible DC transmission system is monitored, and in response to the DC voltage value reaching the voltage threshold, the offshore converter station of the flexible DC transmission system is controlled to execute a low-voltage voltage limiting control strategy to reduce the AC bus voltage amplitude of the offshore converter station, and in response to the voltage amplitude dropping to the lower limit of the amplitude, the grid-side converter of the wind turbine converter system is controlled to execute a low-voltage current limiting control strategy to reduce the input power of the flexible DC transmission system. When there is a minor system fault, the reactive power support and overvoltage regulation capabilities of the flexible DC system can be fully utilized without the investment of energy-consuming devices. When there is a serious system fault, sufficient response time is reserved for the investment of energy-consuming devices, which greatly reduces the parameter design requirements and investment costs of energy-consuming devices, thereby improving the control effect of AC faults.

[0034] In a specific example, the AC fault control process of the converter and the flexible DC system is as follows:

[0035] Real-time monitoring of the AC voltage changes at the onshore receiving converter station. When the bus voltage drops due to an AC fault, the reactive power control strategy of the onshore receiving converter station immediately adjusts the reactive power setting value, and the flexible DC transmission system generates additional reactive power to maintain the AC bus voltage amplitude. If the onshore AC bus voltage drops, the system generates surplus power of Pec, which charges the capacitors of the flexible DC system submodules, and the DC voltage U dc Rising, when U dc =1.1U dcN (rising to 1.1 times the rated value), the low-voltage limiting and low-voltage limiting frequency control strategies of the offshore station act simultaneously to reduce the voltage amplitude of the AC busbar of the offshore station and increase the system frequency; when the AC busbar voltage of the offshore station drops to the minimum limiting value, the grid-side low-voltage current limiting control of the wind power converter begins to act to limit the electromagnetic power Pin, and the input power of the wind farm remains unchanged. At this time, Pm>Pin, and the excess energy is converted into the generator rotor speed ω, which increases from the rated value to absorb the excess mechanical power. When ω reaches its upper limit, if there is still a large amount of surplus power in the system, the energy-consuming device is put into operation to absorb the remaining power.

[0036] Figure 3 FIG. 1 is a schematic diagram of an AC fault control device for a converter and a flexible DC system in cooperation with each other according to another embodiment of the present disclosure. Figure 3 As shown, the AC fault control device 50 for the converter and the flexible DC system comprises:

[0037] The first monitoring module 301 is used to monitor the DC voltage value of the onshore converter station of the flexible DC power transmission system when there is surplus power in the flexible DC power transmission system;

[0038] The first control module 302 is used to control the offshore converter station of the flexible DC power transmission system to execute a low voltage limiting control strategy in response to the DC voltage value reaching a voltage threshold, so as to reduce the AC bus voltage amplitude of the offshore converter station;

[0039] The second control module 303 is used to control the grid-side converter of the wind turbine converter system to execute a low-voltage current limiting control strategy in response to the voltage amplitude dropping to the lower amplitude limit, so as to reduce the input power of the flexible DC power transmission system.

[0040] In some embodiments, the device 30 further includes: a third control module, configured to control the onshore converter station to execute a low-voltage reactive power control strategy to increase the reactive power setting value of the onshore converter station.

[0041] In some embodiments, the first control module 302 is further used to: control the offshore converter station of the flexible DC transmission system to execute a low voltage frequency regulation control strategy to increase the system frequency of the offshore converter station.

[0042] In some embodiments, the device 30 further includes: a second monitoring module, used to monitor the current speed value of the generator rotor; and a fourth control module, used to control the start-up of an energy-consuming device configured in the flexible direct current transmission system in response to the current speed value reaching a speed threshold and the existence of surplus power.

[0043] In some embodiments, the voltage threshold is 1.1 times the voltage rating.

[0044] In this embodiment, when there is surplus power in the flexible DC transmission system, the DC voltage value of the onshore converter station of the flexible DC transmission system is monitored, and in response to the DC voltage value reaching the voltage threshold, the offshore converter station of the flexible DC transmission system is controlled to execute a low-voltage limiting control strategy to reduce the AC bus voltage amplitude of the offshore converter station, and in response to the voltage amplitude dropping to the lower limit of the amplitude, the grid-side converter of the wind turbine converter system is controlled to execute a low-voltage limiting control strategy to reduce the input power of the flexible DC transmission system. In this way, when there is a minor fault in the system, the reactive power support and overvoltage regulation capabilities of the flexible DC system can be fully utilized without the need for investment in energy-consuming devices, thereby improving the control effect of AC faults.

[0045] According to an embodiment of the present disclosure, the present disclosure also provides a computer device, a readable storage medium, and a computer program product.

[0046] In order to implement the above embodiments, the present disclosure further proposes a computer program product. When the instruction processor in the computer program product is executed, the AC fault control method for the coordinated converter and flexible DC system proposed in the above embodiments of the present disclosure is executed.

[0047] Figure 4 A block diagram of an exemplary computer device suitable for implementing embodiments of the present disclosure is shown. Figure 4 The computer device 12 shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present disclosure.

[0048] like Figure 4 As shown, the computer device 12 is in the form of a general-purpose computing device. The components of the computer device 12 may include, but are not limited to: one or more processors or processing units 16, a system memory 28, and a bus 18 that connects various system components (including the system memory 28 and the processing unit 16).

[0049] The bus 18 represents one or more of several types of bus structures, including a memory bus or memory controller, a peripheral bus, a graphics acceleration port, a processor or a local bus using any of a variety of bus structures. For example, these architectures include but are not limited to Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MAC) bus, Enhanced ISA bus, Video Electronics Standards Association (VESA) local bus and Peripheral Component Interconnection (PCI) bus.

[0050] The computer device 12 typically includes a variety of computer system readable media. These media can be any available media that can be accessed by the computer device 12, including volatile and non-volatile media, removable and non-removable media.

[0051] The memory 28 may include computer system readable media in the form of volatile memory, such as random access memory (RAM) 30 and / or cache memory 32. The computer device 12 may further include other removable / non-removable, volatile / non-volatile computer system storage media. By way of example only, the storage system 34 may be used to read and write non-removable, non-volatile magnetic media ( Figure 4 Not shown, often called a "hard drive").

[0052] although Figure 4 Not shown in the figure, a disk drive for reading and writing a removable non-volatile disk (e.g., a "floppy disk"), and an optical disk drive for reading and writing a removable non-volatile optical disk (e.g., a compact disc read only memory (CD-ROM), a digital versatile disc read only memory (DVD-ROM), or other optical media) may be provided. In these cases, each drive may be connected to the bus 18 via one or more data medium interfaces. The memory 28 may include at least one program product having a set (e.g., at least one) of program modules configured to perform the functions of the various embodiments of the present disclosure.

[0053] A program / utility 40 having a set (at least one) of program modules 42 may be stored, for example, in the memory 28, such program modules 42 including but not limited to an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment. The program modules 42 generally perform the functions and / or methods of the embodiments described in the present disclosure.

[0054] The computer device 12 may also communicate with one or more external devices 14 (e.g., keyboard, pointing device, display 24, etc.), one or more devices that enable a user to interact with the computer device 12, and / or any device that enables the computer device 12 to communicate with one or more other computing devices (e.g., network card, modem, etc.). Such communication may be performed via an input / output (I / O) interface 22. In addition, the computer device 12 may also communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network, such as the Internet) via a network adapter 20. As shown, the network adapter 20 communicates with other modules of the computer device 12 via a bus 18. It should be understood that, although not shown in the figure, other hardware and / or software modules may be used in conjunction with the computer device 12, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage systems.

[0055] The processing unit 16 executes various functional applications by running the programs stored in the system memory 28, such as implementing the AC fault control method for the coordinated operation of the converter and the flexible DC system mentioned in the above-mentioned embodiment.

[0056] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. The present disclosure is intended to cover any variations, uses or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The description and examples are to be considered exemplary only, and the true scope and spirit of the present disclosure are indicated by the following claims.

[0057] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

[0058] It should be noted that, in the description of the present disclosure, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present disclosure, unless otherwise specified, the meaning of "plurality" is two or more.

[0059] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present disclosure includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present disclosure belong.

[0060] It should be understood that the various parts of the present disclosure can be implemented in hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0061] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0062] In addition, each functional unit in each embodiment of the present disclosure may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0063] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0064] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0065] Although the embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present disclosure. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present disclosure.

Claims

1. A method for controlling AC faults in cooperation between a converter and a flexible DC system. It is characterized in that include: In the case where there is surplus power in the flexible direct current transmission system, monitoring the direct current voltage value of the onshore converter station of the flexible direct current transmission system; In response to the DC voltage value reaching a voltage threshold, controlling the offshore converter station of the flexible DC power transmission system to execute a low voltage limiting control strategy to reduce the AC bus voltage amplitude of the offshore converter station; In response to the voltage amplitude dropping to the lower amplitude limit, controlling the grid-side converter of the wind turbine converter system to execute a low-voltage current limiting control strategy to reduce the input power of the flexible direct current transmission system; After the grid-side converter of the wind turbine converter system is controlled to execute the low-voltage current limiting control strategy to reduce the input power of the flexible direct current transmission system, the method further includes: Monitor the current speed value of the generator rotor; as well as In response to the current rotational speed value reaching the rotational speed threshold and the existence of the surplus power, controlling to start an energy consumption device configured in the flexible direct current power transmission system.

2. The method according to claim 1, It is characterized in that Before monitoring the DC voltage value of the onshore converter station, the method further includes: The onshore converter station is controlled to execute a low-voltage reactive power control strategy to increase the reactive power setting value of the onshore converter station.

3. The method according to claim 1, It is characterized in that Before the control of the grid-side converter of the wind turbine converter system to execute the low-voltage current limiting control strategy in response to the voltage amplitude dropping to the lower amplitude limit, the method further includes: The offshore converter station of the flexible direct current transmission system is controlled to execute a low voltage frequency regulation control strategy to increase the system frequency of the offshore converter station.

4. The method according to claim 1, It is characterized in that in, The voltage threshold is 1.1 times the voltage rating.

5. An AC fault control device in which a converter and a flexible DC system cooperate, It is characterized in that include: A first monitoring module is used to monitor the DC voltage value of an onshore converter station of the flexible DC power transmission system when there is surplus power in the flexible DC power transmission system; A first control module is configured to control the offshore converter station of the flexible DC power transmission system to execute a low voltage limiting control strategy in response to the DC voltage value reaching a voltage threshold, so as to reduce the AC bus voltage amplitude of the offshore converter station; A second control module is used for controlling the grid-side converter of the wind turbine converter system to execute a low-voltage current limiting control strategy in response to the voltage amplitude dropping to the lower amplitude limit, so as to reduce the input power of the flexible direct current transmission system; The device also includes: The second monitoring module is used to monitor the current rotation speed value of the generator rotor; as well as The fourth control module is configured to control starting of an energy consumption device configured in the flexible direct current power transmission system in response to the current speed value reaching the speed threshold and the existence of the surplus power.

6. The device as claimed in claim 5, It is characterized in that The device also includes: The third control module is used to control the onshore converter station to execute a low-voltage reactive power control strategy to increase the reactive power setting value of the onshore converter station.

7. The device according to claim 5, It is characterized in that The first control module is further configured to: The offshore converter station of the flexible direct current transmission system is controlled to execute a low voltage frequency regulation control strategy to increase the system frequency of the offshore converter station.

8. A non-transitory computer-readable storage medium storing computer instructions, in, The computer instructions are used to cause the computer to execute the method according to any one of claims 1-4.

Images