CN116054227A - AC Fault Control Method and Device Based on Coordination of Converter and Flexible DC System - Google Patents

Abstract

The disclosure provides an alternating current fault control method and device for cooperation of a converter and a soft direct current system, comprising the following steps: under the condition that surplus power exists in the flexible direct current transmission system, the direct current voltage value of a land converter station of the flexible direct current transmission system is monitored, the marine converter station of the flexible direct current transmission system is controlled to execute a low-voltage limiting control strategy in response to the fact that the direct current voltage value reaches a voltage threshold value, the alternating current bus voltage amplitude of the marine converter station is reduced, the grid-side converter of the fan converter system is controlled to execute the low-voltage limiting control strategy in response to the fact that the voltage amplitude is reduced to the lower amplitude limit, the input power of the flexible direct current transmission system is reduced, reactive support and overvoltage regulation capability of the flexible direct current transmission system can be fully exerted when the system is slightly faulty, input of energy consumption devices is not needed, and accordingly the control effect of alternating current faults is improved.

Description

AC Fault Control Method and Device Based on Coordination of Converter and Flexible DC System

technical field

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 in which a converter and a flexible DC system are coordinated.

Background technique

At present, the grid connection methods of offshore wind power transmission are mainly divided into two categories: high-voltage AC transmission and high-voltage direct current transmission. Among them, high-voltage direct current transmission adopts flexible direct current transmission technology based on voltage source converters. In practical applications, after the onshore AC fault occurs, the active power sending capacity of the AC side of the onshore converter station of the flexible DC system decreases. Since the power of the offshore wind farm cannot be sent out completely, a large amount of surplus power appears in the DC system, resulting in a The voltage of the sub-module of the station and the DC voltage between the poles rise rapidly, and the overvoltage protection can be triggered within a few milliseconds to tens of milliseconds, causing the system to stop running.

In related technologies, AC fault control methods include adopting energy-dissipating resistor devices, reducing power of wind turbines, or adjusting the AC bus voltage amplitude of the offshore sending-end converter station with the rapid adjustment capability of the flexible direct current transmission system. However, although the use of energy-dissipating resistance devices can effectively consume excess power, the requirements for its resistance parameters are relatively high, the economy is not high, and the fast response speed requirements also make the investment cost of energy-dissipating resistance devices relatively high; while the use of wind turbines to reduce Power operation can also balance power to a certain extent, but the response speed is too slow; while the adjustment method of the flexible DC transmission system has no obvious effect on serious faults and can easily cause wind turbines to go off-grid. Therefore, the AC fault control method needs to be optimized.

Contents of the invention

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

The embodiment of the first aspect of the present disclosure proposes an AC fault control method for the cooperation of the converter and the flexible direct current system, including: monitoring the land converter station of the flexible direct current transmission system when there is surplus power in the flexible direct current transmission system DC voltage value; in response to the DC voltage value reaching the voltage threshold, the offshore converter station of the flexible DC transmission system is controlled to implement 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 falling to For the lower limit of the amplitude, the grid-side converter controlling the wind turbine converter system implements a low-voltage current-limiting control strategy to reduce the input power of the HVDC system.

The embodiment of the second aspect of the present disclosure proposes an AC fault control device coordinated by a converter and a flexible DC system, including: a first monitoring module, used to monitor the flexible DC transmission system when there is surplus power in the flexible DC transmission system The DC voltage value of the onshore converter station of the system; the first control module is used to control the offshore converter station of the flexible direct current transmission system to implement a low-voltage voltage limiting control strategy in response to the DC voltage value reaching the voltage threshold, so as to reduce the offshore converter The voltage amplitude of the AC busbar of the station; the second control module is used to respond to the voltage amplitude falling to the lower limit of the amplitude, and control the grid-side converter of the fan conversion system to implement a low-voltage current limiting control strategy to reduce the voltage of the flexible DC transmission system. input power.

The embodiment of the third aspect of the present disclosure provides a computer device, including: at least one processor; and a memory connected in communication with the at least one processor; wherein, the memory stores information that can be executed by the at least one processor. instructions, 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 coordination of the converter and the flexible DC system according to the embodiment of the present disclosure.

The embodiment of the fourth aspect of the present disclosure proposes a non-transitory computer-readable storage medium storing computer instructions, the computer instructions are used to enable the computer to execute the coordination of the converter and the flexible straight system disclosed in the embodiment of the present disclosure AC fault control method.

In this embodiment, when there is surplus power in the flexible direct current transmission system, by monitoring the direct current voltage value of the land converter station of the flexible direct current transmission system, and responding to the direct current voltage value reaching the voltage threshold, the control of the flexible direct current transmission system The offshore converter station implements a low-voltage voltage limiting control strategy to reduce the voltage amplitude of the AC busbar of the offshore converter station, and responds to the voltage amplitude falling to the lower limit of the amplitude, and controls the grid-side converter of the wind turbine conversion system to implement low-voltage current limiting control strategy to reduce the input power of the flexible direct current transmission system, which can give full play to the reactive power support and overvoltage regulation capabilities of the flexible direct current transmission system when the system is slightly faulty, and does not need to invest in energy-consuming devices. A sufficient response time is reserved for the input 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.

Additional aspects and advantages of the disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the disclosure.

Description of drawings

The above and/or additional aspects and advantages of the present disclosure will become apparent and understandable from the following description of the embodiments in conjunction with the accompanying drawings, wherein:

Fig. 1 is a schematic flow chart of an AC fault control method in which a converter and a flexible DC system cooperate according to an embodiment of the present disclosure;

Fig. 2 is a schematic structural diagram of a wind power grid-connected system provided according to an embodiment of the present disclosure;

Fig. 3 is a schematic diagram of an AC fault control device coordinated by a converter and a flexible DC system according to another embodiment of the present disclosure;

Figure 4 shows a block diagram of an exemplary computer device suitable for use in implementing embodiments of the present disclosure.

Detailed ways

Embodiments of the present disclosure are described in detail below, examples of which are illustrated in the drawings, in which the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present disclosure and should not be construed as limiting the present disclosure. On the contrary, the embodiments of the present disclosure include all changes, modifications and equivalents coming within the spirit and scope of the appended claims.

Wherein, it should be noted that the execution body of the AC fault control method for the cooperation of the converter and the DC system in this embodiment may be the AC fault control device for the cooperation of the converter and the DC system, and the device may be controlled by software and/or or hardware, the apparatus may be configured in electronic equipment, and the electronic equipment may include but not limited to a terminal, a server, and the like.

Fig. 1 is a schematic flowchart of an AC fault control method for a converter and a DC system coordinated according to an embodiment of the present disclosure. As shown in Fig. 1 , the method includes:

S101: When there is surplus power in the flexible direct current transmission system, monitor the direct current voltage value of the land converter station of the flexible direct current transmission system.

Specifically, FIG. 2 is a schematic structural diagram of a wind power grid-connected system provided according to an embodiment of the present disclosure. As shown in FIG. 2 , the wind power grid-connected system of this embodiment includes a flexible DC system (wind turbine converter) and any other possible devices, without limitation. Among them, the flexible DC transmission system includes offshore converter stations and onshore converter stations. On-road converter stations are connected to the onshore power grid system, and offshore converter stations are connected to the offshore power grid. The wind turbine conversion system includes machine-side converters and The grid-side converter is connected to the wind turbine generator, and the grid-side converter is connected to the offshore power grid. This embodiment does not limit the specific structure of the wind power grid-connected system.

In practical applications, the mechanical power generated by the wind farm can be represented by Pm, for example; the input power of the wind power grid-connected system, that is: the electrical power converted from mechanical power (also called electromagnetic power), which can be represented by Pin; The output power of the grid-connected system, that is, the power integrated into the onshore grid, can be represented by Pout; while the surplus power generated by the wind power grid-connected system (more specifically, the flexible DC transmission system) can be represented by Pec, and the relationship is Pin =Pout+Pec. When there is no AC fault on land and the system is in steady state operation, Pm=Pin=Pout, Pec=0.

Among them, the offshore converter station in this embodiment adopts a constant AC voltage and constant frequency control strategy (also called a control mode), that is to say, the offshore converter station operates at a constant AC voltage and a fixed frequency during steady-state operation. , and can also be equipped with low-voltage voltage limiting and low-voltage frequency modulation control strategies; while onshore converter stations, for example, adopt constant DC voltage and constant reactive power control strategies, that is to say, when the offshore converter station operates in a steady state, it is a fixed AC Voltage, fixed reactive power, and also equipped with low-voltage reactive power control strategy; while the machine-side converter adopts constant DC voltage and constant reactive power control strategy, while the grid-side converter adopts constant electromagnetic power, constant reactive power In addition, the grid-side converter is also equipped with a low-voltage current limiting control strategy.

In practical applications, the onshore AC fault will cause the voltage of the onshore AC bus to drop, and the ability to send active power on the AC side of the onshore converter station of the flexible DC system will drop. Since the power of the offshore wind farm cannot be sent out completely, the DC system A large amount of surplus power appears, and the surplus power will charge the sub-module capacitors of the flexible DC system, which will cause the voltage of the onshore converter station and the DC voltage between poles to rise rapidly.

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 judged whether there is surplus power in the flexible DC transmission system, and after determining that there is surplus power in the flexible DC transmission system In the case of , the DC voltage value of the onshore converter station of the flexible DC transmission system is monitored, and the DC voltage value can be expressed by U _dc .

In some embodiments, after monitoring the onshore AC bus voltage drop, this embodiment can also control the onshore converter station to implement a low-voltage reactive power control strategy to increase the reactive power setting value of the onshore converter station, so that the flexible direct current transmission system It can generate additional reactive power, maintain the voltage amplitude of the onshore AC busbar, and give full play to the reactive power support of the flexible DC system under AC faults, and improve the control effect under fault conditions to a certain extent.

S102: In response to the DC voltage reaching the voltage threshold, control the offshore converter station of the flexible direct current transmission system to implement a low-voltage voltage limiting control strategy, so as to reduce the voltage amplitude of the AC bus of the offshore converter station.

Further, this embodiment can compare the rising DC voltage value U _dc with the voltage threshold, and if the DC voltage value U _dc reaches the voltage threshold, this embodiment can control the offshore converter station of the flexible direct current transmission system to perform low-voltage voltage limiting Control strategy to reduce AC bus voltage amplitude in offshore converter station.

In some embodiments, the voltage threshold is, for example, 1.1 times the rated voltage. Wherein, the rated voltage value can be represented by U _dcN , for example, that is to say, when the DC voltage value U _dc =1.1U _dcN (rising to 1.1 times the rated value), the offshore converter station implements a low-voltage voltage limiting control strategy to reduce AC busbar voltage amplitude of offshore converter station. Wherein, the voltage threshold can be flexibly set according to actual application scenarios, and there is no limitation on this.

In some other embodiments, while controlling the offshore converter station of the flexible direct current transmission system to implement the low-voltage voltage limiting control strategy, this embodiment can also control the offshore converter station of the flexible direct current transmission system to implement the low-voltage frequency modulation control strategy, so as to increase the The system frequency of the current station, that is to say, the low-voltage voltage limiting and low-voltage frequency modulation control strategies of the offshore converter station work at the same time to reduce the AC bus voltage amplitude of the offshore station and increase the system frequency.

S103: In response to the voltage amplitude falling to the lower limit of the amplitude, the grid-side converter controlling the wind turbine converter system executes a low-voltage current limiting control strategy to reduce the input power of the flexible direct current transmission system.

Further, this embodiment can compare the voltage amplitude with a preset lower limit of the amplitude (that is, the minimum limit value), and when the voltage amplitude drops to the lower limit of the amplitude, this embodiment can control the grid of the wind turbine converter system The low-voltage current-limiting control strategy of the grid-side converter is implemented to reduce the DC current of the grid-side converter, thereby reducing the input power Pin of the HVDC system. That is to say, when the voltage amplitude drops to the lower limit, the grid-side converter The low-voltage current-limiting control of the current regulator starts to function, limiting the electromagnetic power Pin. Since the mechanical power Pm of the wind farm remains unchanged, Pm>Pin at this time, the excess energy can be converted into the rotor speed ω of the generator, and ω increases from the rated value to absorb the excess mechanical power, which in turn can reduce the power of the flexible DC transmission system Surplus Power Pec.

In some embodiments, an energy-consuming device (for example, an energy-dissipating resistor) may also be configured in the flexible direct current transmission system to absorb surplus power, wherein, for example, the energy-consuming device may be configured on the DC side of the onshore converter station. Specifically, this embodiment can monitor the current rotational speed value of the generator rotor in real time; further, compare the current rotational speed value ω with the rotational speed threshold (the upper limit value of the rotational speed of the generator rotor), and if the current rotational speed value ω reaches the rotational speed threshold, then Further determine whether there is 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 means that the system is seriously faulty and cannot be supported by the reactive power of the flexible direct current system and the control method provided by the above-mentioned embodiments To reduce the surplus power Pec, in this case, this embodiment can also control and start the energy-consuming device to absorb the surplus power. Therefore, when the system fails seriously, this embodiment can reserve sufficient response time for the input of energy-consuming devices, greatly reducing the design requirements and investment costs of energy-consuming resistor parameters.

In this embodiment, when there is surplus power in the flexible direct current transmission system, by monitoring the direct current voltage value of the land converter station of the flexible direct current transmission system, and responding to the direct current voltage value reaching the voltage threshold, the control of the flexible direct current transmission system The offshore converter station implements a low-voltage voltage limiting control strategy to reduce the voltage amplitude of the AC busbar of the offshore converter station, and responds to the voltage amplitude falling to the lower limit of the amplitude, and controls the grid-side converter of the wind turbine conversion system to implement low-voltage current limiting control strategy to reduce the input power of the flexible direct current transmission system, which can give full play to the reactive power support and overvoltage regulation capabilities of the flexible direct current transmission system when the system is slightly faulty, and does not need to invest in energy-consuming devices. A sufficient response time is reserved for the input 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.

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

Real-time monitoring of AC voltage changes at the onshore receiving-end converter station. When the bus voltage drops due to AC faults, the reactive power control strategy of the onshore receiving-end converter station immediately adjusts the reactive power setting value, and the flexible DC transmission system increases reactive power. Maintain the voltage amplitude of the AC busbar; if the voltage of the onshore AC busbar decreases, the system will generate a surplus power of Pec, charge the capacitor of the sub-module of the flexible DC system, and the _DC voltage Udc of the onshore converter station will rise, when _Udc = 1.1U When _dcN (rising to 1.1 times the rated value), the low-voltage limiting and low-voltage frequency limiting 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 voltage of the AC busbar of the offshore station drops to the minimum limit value, the low-voltage current limiting control on the grid side of the wind power converter starts to limit the electromagnetic power Pin, and the input power of the wind farm remains unchanged. At this time, Pm>Pin, the excess energy is converted into the rotor speed ω of the generator, and ω starts from the rated value Increase to absorb 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 will be put into operation to absorb the excess power.

Fig. 3 is a schematic diagram of an AC fault control device coordinated by a converter and a flexible DC system according to another embodiment of the present disclosure. As shown in Fig. 3, the AC fault control device 50 of the converter and the flexible DC system includes:

The first monitoring module 301 is configured to monitor the DC voltage value of the onshore converter station of the flexible direct current transmission system when there is surplus power in the flexible direct current transmission system;

The first control module 302 is configured to, in response to the DC voltage reaching a voltage threshold, control the offshore converter station of the flexible direct current transmission system to execute a low-voltage voltage limiting control strategy, so as to reduce the AC bus voltage amplitude of the offshore converter station;

The second control module 303 is configured to control the grid-side converter of the wind turbine converter system to implement a low-voltage current limiting control strategy to reduce the input power of the flexible direct current transmission system in response to the voltage amplitude falling to the lower limit of the amplitude.

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, so as to increase the reactive power setting value of the onshore converter station.

In some embodiments, the first control module 302 is further configured to: control the offshore converter station of the flexible direct current transmission system to execute a low-voltage frequency modulation control strategy, so as to increase the system frequency of the offshore converter station.

In some embodiments, the device 30 further includes: a second monitoring module, configured to monitor the current rotational speed value of the generator rotor; and a fourth control module, configured to control the startup flexibility in response to the current rotational speed value reaching the rotational speed threshold and surplus power The energy consumption device configured in the direct current transmission system.

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

In this embodiment, when there is surplus power in the flexible direct current transmission system, by monitoring the direct current voltage value of the land converter station of the flexible direct current transmission system, and responding to the direct current voltage value reaching the voltage threshold, the control of the flexible direct current transmission system The offshore converter station implements a low-voltage voltage limiting control strategy to reduce the voltage amplitude of the AC busbar of the offshore converter station, and responds to the voltage amplitude falling to the lower limit of the amplitude, and controls the grid-side converter of the wind turbine conversion system to implement low-voltage current limiting The control strategy to reduce the input power of the flexible DC transmission system can give full play to the reactive power support and overvoltage regulation capabilities of the flexible DC transmission system when the system is slightly faulty, without the need for energy-consuming devices, thereby improving the control effect of AC faults.

According to the embodiments of the present disclosure, the present disclosure also provides a computer device, a readable storage medium, and a computer program product.

In order to realize the above-mentioned embodiments, the present disclosure also proposes a computer program product. When the instruction processor in the computer program product is executed, it executes the AC fault control method for the cooperation of the converter and the flexible DC system as proposed in the foregoing embodiments of the present disclosure. .

Figure 4 shows a block diagram of an exemplary computer device suitable for use in implementing embodiments of the present disclosure. The computer device 12 shown in FIG. 4 is only an example, and should not limit the functions and scope of use of the embodiments of the present disclosure.

As shown in FIG. 4, computer device 12 takes the form of a general-purpose computing device. Components of computer device 12 may include, but are not limited to: one or more processors or processing units 16 , system memory 28 , bus 18 connecting various system components including system memory 28 and processing unit 16 .

Bus 18 represents one or more of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics 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 (Industry Standard Architecture; hereinafter referred to as: ISA) bus, Micro Channel Architecture (Micro Channel Architecture; hereinafter referred to as: MAC) bus, enhanced ISA bus, video electronics standard Association (Video Electronics Standards Association; hereinafter referred to as: VESA) local bus and peripheral component interconnection (Peripheral Component Interconnection; hereinafter referred to as: PCI) bus.

Computer device 12 typically includes a variety of computer system readable media. These media can be any available media that can be accessed by computer device 12 and include both volatile and nonvolatile media, removable and non-removable media.

The memory 28 may include a computer system readable medium in the form of a volatile memory, such as a random access memory (Random Access Memory; hereinafter referred to as: RAM) 30 and/or a cache memory 32 . Computer device 12 may further include other removable/non-removable, volatile/nonvolatile computer system storage media. By way of example only, storage system 34 may be used to read and write to non-removable, non-volatile magnetic media (not shown in FIG. 4, commonly referred to as a "hard drive").

Although not shown in FIG. 4, a disk drive for reading and writing to a removable nonvolatile disk (such as a "floppy disk") may be provided, as well as a disk drive for a removable nonvolatile disk (such as a CD-ROM (Compact Disc Read Only Memory; hereinafter referred to as: CD-ROM), Digital Video Disc Read Only Memory (hereinafter referred to as: DVD-ROM) or other optical media). In these cases, each drive may be connected to bus 18 via one or more data media interfaces. Memory 28 may include at least one program product having a set (eg, at least one) of program modules configured to perform the functions of various embodiments of the present disclosure.

A program/utility 40 having a set (at least one) of program modules 42 may be stored, for example, in 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 or some combination of these examples may include implementations of network environments. The program modules 42 generally perform the functions and/or methods of the embodiments described in this disclosure.

The computer device 12 may also communicate with one or more external devices 14 (e.g., a keyboard, pointing device, display 24, etc.), and with one or more devices that enable a user to interact with the computer device 12, and/or with Any device (eg, network card, modem, etc.) that enables the computing device 12 to communicate with one or more other computing devices. Such communication may occur through input/output (I/O) interface 22 . Moreover, the computer device 12 can also communicate with one or more networks (such as a local area network (Local Area Network; hereinafter referred to as: LAN), a wide area network (Wide Area Network; hereinafter referred to as: WAN) and/or public networks, such as the Internet, through the network adapter 20. ) communication. As shown, network adapter 20 communicates with other modules of computer device 12 via bus 18 . It should be appreciated that although not shown, other hardware and/or software modules may be used in conjunction with 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 system, etc.

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 cooperation of the converter and the flexible DC system mentioned in the foregoing embodiments.

Other embodiments of the present disclosure will be readily apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The present disclosure is intended to cover any modification, use or adaptation of the present disclosure. These modifications, uses or adaptations follow the general principles of the present disclosure and include common knowledge or conventional technical means in the technical field not disclosed in the present disclosure. . The specification and examples are to be considered exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

It should be understood that the present disclosure is not limited to the precise constructions which have been described above and shown in the drawings, and 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.

It should be noted that, in the description of the present disclosure, terms such as "first" and "second" are used for description purposes only, and should not be understood as indicating or implying relative importance. In addition, in the description of the present disclosure, unless otherwise specified, "plurality" means two or more.

Any process or method descriptions in flowcharts or otherwise described herein may be understood to represent modules, segments or portions of code comprising one or more executable instructions for implementing specific logical functions or steps of the process , and the scope of preferred embodiments of the present disclosure includes additional implementations in which functions may be performed out of the order shown or discussed, including substantially concurrently or in reverse order depending on the functions involved, which shall It is understood by those skilled in the art to which the embodiments of the present disclosure pertain.

It should be understood that various parts of the present disclosure may be implemented in hardware, software, firmware or a combination thereof. In the embodiments described above, various steps or methods may be implemented by software or firmware stored in 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 or combination of the following techniques known in the art: Discrete logic circuits, ASICs with suitable combinational logic gates, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

Those of ordinary skill in the art can understand that all or part of the steps carried by the methods of the above embodiments can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. During execution, one or a combination of the steps of the method embodiments is included.

In addition, each functional unit in each embodiment of the present disclosure may be integrated into one processing module, each unit may exist separately physically, or two or more units may be integrated into one module. The above-mentioned integrated modules can be implemented in the form of hardware or in the form of software function modules. If the integrated modules are realized in the form of software function modules and sold or used as independent products, they can also be stored in a computer-readable storage medium.

The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, and the like.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or characteristic is included in at least one embodiment or example of the present disclosure. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present disclosure have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limitations on the present disclosure, and those skilled in the art can understand the above-mentioned embodiments within the scope of the present disclosure. The embodiments are subject to changes, modifications, substitutions and variations.

Claims (10)

1. An alternating current fault control method for cooperation of a converter and a soft direct current system is characterized by comprising the following steps of:

under the condition that surplus power exists in a flexible direct current transmission system, monitoring a direct current voltage value of a land converter station of the flexible direct current transmission system;

controlling an offshore converter station of the flexible direct current transmission system to execute a low-voltage limiting control strategy in response to the direct current voltage value reaching a voltage threshold value so as to reduce the alternating current bus voltage amplitude of the offshore converter station;

and in response to the voltage amplitude is reduced to the amplitude lower limit, controlling a grid-side converter of the fan converter system to execute a low-voltage current limiting control strategy so as to reduce the input power of the flexible direct current transmission system.

2. The method of claim 1, wherein prior to said monitoring the dc voltage value of the land based converter station, further comprising:

and controlling the land convertor station to execute a low-voltage reactive power control strategy so as to increase the reactive power setting value of the land convertor station.

3. The method of claim 1, wherein the controlling the grid-side converter of the fan converter system in response to the voltage magnitude falling to a magnitude lower limit further comprises, prior to the performing the low-voltage current limit control strategy:

and controlling the offshore converter station of the flexible direct current transmission system to execute a low-voltage frequency modulation control strategy so as to increase the system frequency of the offshore converter station.

4. The method of claim 1, wherein the controlling the grid-side converter of the fan converter system to implement the low-voltage current-limiting control strategy to reduce the input power of the flexible dc power transmission system further comprises:

monitoring the current rotation speed value of a generator rotor; and

and controlling and starting the energy consumption device configured by the flexible direct current transmission system in response to the current rotation speed value reaches a rotation speed threshold value and the surplus power exists.

5. The method of claim 1, wherein the voltage threshold is 1.1 times a voltage rating.

6. An ac fault control device for cooperation between a converter and a soft-direct system, comprising:

the first monitoring module is used for monitoring the direct-current voltage value of the land converter station of the flexible direct-current power transmission system under the condition that surplus power exists in the flexible direct-current power transmission system;

the first control module is used for responding to the direct-current voltage value reaching a voltage threshold value and controlling an offshore converter station of the flexible direct-current power transmission system to execute a low-voltage limiting control strategy so as to reduce the voltage amplitude of an alternating-current bus of the offshore converter station;

and the second control module is used for responding to the voltage amplitude falling to the amplitude lower limit and controlling a grid-side converter of the fan converter system to execute a low-voltage current-limiting control strategy so as to reduce the input power of the flexible direct-current transmission system.

7. The apparatus of claim 6, wherein the apparatus further comprises:

and the third control module is used for controlling the land convertor station to execute a low-voltage reactive power control strategy so as to increase the reactive power setting value of the land convertor station.

8. The apparatus of claim 6, wherein the first control module is further to:

and controlling the offshore converter station of the flexible direct current transmission system to execute a low-voltage frequency modulation control strategy so as to increase the system frequency of the offshore converter station.

9. The apparatus of claim 6, wherein the apparatus further comprises:

the second monitoring module is used for monitoring the current rotating speed value of the generator rotor; and

and the fourth control module is used for controlling and starting the energy consumption device configured by the flexible direct current transmission system in response to the current rotation speed value reaching a rotation speed threshold value and the surplus power.

10. A non-transitory computer readable storage medium storing computer instructions for causing the computer to perform the method of any one of claims 1-5.

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