Flexible direct-current power emergency limiting method and device, electronic equipment and storage medium

Abstract

The invention discloses a flexible direct-current power emergency limiting method and device, electronic equipment and a storage medium, which are used for solving the problem of how to timely reduce the flexible direct-current output power of a wind power plant to be below the long-term transmission capacity of an in-operation connection transformer and avoid damage to the residual connection transformer of a land station when a land fault occurs. The offshore wind power flexible direct delivery system comprises at least one sea connection transformer and at least one land connection transformer which are equal in number. When the onshore connection transformer fault occurs on the onshore side, whether the number n of the onshore connection transformers in the running state before the fault is larger than or equal to 2 is judged; if yes, determining the long-term stable transmission power of n-1 land connection transformers except the fault land connection transformer, and generating a power limit instruction; and measuring the direct-current active power at the sea side in real time, generating an emergency power reduction instruction based on the power limiting instruction, and controlling the direct-current active power at the sea side to be reduced to long-term stable transmission power based on the emergency power reduction instruction.

Description

Technical Field

[0001] This invention relates to the field of power control technology, and in particular to a flexible DC power emergency limiting method, device, electronic device, and storage medium. Background Technology

[0002] Large-capacity offshore wind power transmitted via flexible DC transmission is a crucial technological means to achieve efficient long-distance, large-scale transmission of clean energy. In this project, a single converter can reach a capacity of 2000MW, meeting the transmission needs of large-scale wind power. To achieve voltage level conversion and electrical isolation, offshore and onshore converter stations typically each have multiple interconnecting transformers operating in parallel. Each interconnecting transformer possesses a certain overload capacity to ensure the stability and reliability of the system under different operating conditions. Notably, the grid-side and valve-side terminals of multiple interconnecting transformers are connected to the same electrical point, meaning they operate directly in parallel under normal operating conditions. During normal operation, the valve-side and grid-side terminals of the multiple interconnecting transformers are directly connected in parallel. This configuration not only improves system redundancy and flexibility but also effectively balances load distribution, ensuring the efficient operation and power quality of the entire wind power transmission system.

[0003] However, the sending end of offshore wind power's flexible DC transmission is an isolated system and does not control DC active power. In other words, the DC transmission itself lacks active power control capabilities. Active power limitation is primarily achieved through power limiting at the wind farm. Under this operating mode, if one onshore transformer fails and goes out of service, all power will be transferred to the remaining operating transformers. In this situation, operation can continue for short periods (minutes or less), but not long-term. If the power transmitted from the wind farm via flexible DC cannot be reduced to below the long-term transmission capacity of the operating transformers in time, the remaining onshore transformers will eventually be damaged. Summary of the Invention

[0004] This invention provides a flexible DC power emergency limiting method, device, electronic equipment, and storage medium to solve or partially solve the technical problem of how to promptly reduce the power transmitted from the wind farm via flexible DC to below the long-term transmission capacity of the onshore connection transformer when an onshore fault occurs, so as to avoid damage to the remaining connection transformers of the onshore station.

[0005] This invention provides a flexible DC power emergency limiting method applied to an offshore wind power flexible DC transmission system; the offshore wind power flexible DC transmission system includes at least one offshore connection transformer and an onshore connection transformer of equal number; the method includes:

[0006] When a fault occurs in an onshore connecting transformer, determine whether the number n of onshore connecting transformers that were in operation before the fault is greater than or equal to 2.

[0007] If so, determine the long-term stable transmission power of n-1 onshore connection transformers other than the faulty onshore connection transformer, and generate a power limiting command.

[0008] The DC active power on the sea side is measured in real time, an emergency power reduction command is generated based on the power limitation command, and the DC active power on the sea side is automatically reduced to the long-term stable transmission power based on the emergency power reduction command.

[0009] Optionally, each of the onshore interconnection transformers is connected in parallel to the onshore control and protection device of the onshore converter station; the onshore control and protection device is connected to the offshore control and protection device of the offshore converter station via a DC submarine cable; the determination of the long-term stable transmission power of n-1 onshore interconnection transformers excluding the faulty onshore interconnection transformer, and the generation of power limiting commands, includes:

[0010] When a fault is detected by the aforementioned land-based control and protection device, the long-term stable transmission power of n-1 land-based connection transformers, excluding the faulty land-based connection transformer, is measured.

[0011] Based on the long-term stable transmission power, a power limiting command is generated by the land-based control and protection device, and the power limiting command is transmitted to the marine control and protection device based on DC inter-station communication.

[0012] Optionally, each of the offshore connection transformers corresponds to the energy management system of an offshore wind farm area, and each of the energy management systems is connected in parallel to the automatic power control system of the offshore wind farm. The automatic power control system is connected to the offshore control and protection device. The real-time measurement of the DC active power on the offshore side, the generation of an emergency power reduction command based on the power limitation command, and the automatic control of reducing the DC active power on the offshore side to the long-term stable transmission power based on the emergency power reduction command include:

[0013] After receiving the power limitation command, the marine control and protection device synchronously measures the DC active power on the marine side in real time.

[0014] The marine control and protection device extracts the long-term stable transmission power from the power limitation command, generates an emergency power reduction command based on the long-term stable transmission power, and sends the emergency power reduction command to the automatic power control system.

[0015] The automatic power control system distributes the emergency power reduction command to each of the energy management systems, so as to control the power reduction of the corresponding offshore wind farm through each of the offshore connection transformers, so as to reduce the DC active power on the offshore side to the long-term stable transmission power.

[0016] Optionally, the method further includes:

[0017] If, after a preset period of power reduction control, the marine control and protection device detects that the DC active power on the marine side has not been successfully reduced to the long-term stable transmission power, it controls the automatic disconnection of one of the marine connection transformers from the at least one marine connection transformer.

[0018] Optionally, after automatically disconnecting one offshore connection transformer via the offshore control and protection device, the method further includes:

[0019] Control the shutdown of wind turbines in offshore wind farms connected to the disconnected offshore transformers to reduce the total power fed into the offshore wind power flexible DC transmission system, thereby reducing the DC active power on the offshore side to the long-term stable transmission power.

[0020] Optionally, the method further includes:

[0021] When the number of onshore connected transformers n that were in operation before the fault was 1, the automatic interlocking action was directly executed to shut down the offshore wind power flexible direct transmission system.

[0022] Optionally, the method further includes:

[0023] When the number of onshore connecting transformers n that were in operation before the fault is greater than or equal to 2, and two or more onshore connecting transformers fail simultaneously on the onshore side, an automatic interlocking action is directly executed to shut down the offshore wind power flexible direct transmission system.

[0024] This invention also provides a flexible DC power emergency limiting device for use in offshore wind power flexible DC transmission systems; the offshore wind power flexible DC transmission system includes at least one offshore connection transformer and an onshore connection transformer of equal number; the device includes:

[0025] The fault monitoring unit is used to determine whether the number n of onshore connected transformers that were in operation before the fault occurred is greater than or equal to 2 when an onshore connected transformer fault occurs on the onshore side.

[0026] The power limiting command generation unit is used to determine the long-term stable transmission power of n-1 onshore interconnection transformers, excluding the faulty onshore interconnection transformer, and to generate power limiting commands.

[0027] The emergency power reduction unit is used to measure the DC active power on the sea side in real time, generate an emergency power reduction command based on the power limit command, and automatically control the DC active power on the sea side to be reduced to the long-term stable transmission power based on the emergency power reduction command.

[0028] The present invention also provides an electronic device, the device comprising a processor and a memory:

[0029] The memory is used to store program code and transmit the program code to the processor;

[0030] The processor is configured to execute the flexible DC power emergency limiting method as described above, according to instructions in the program code.

[0031] The present invention also provides a computer-readable storage medium for storing program code for performing the flexible DC power emergency limiting method as described in any of the preceding claims.

[0032] As can be seen from the above technical solutions, the present invention has the following advantages:

[0033] A flexible DC power emergency limiting method is provided. It is applied to an offshore wind power flexible DC transmission system, which includes at least one offshore connection transformer and an onshore connection transformer of equal number. When an onshore connection transformer fails, the method determines whether the number of onshore connection transformers (n) that were in operation before the failure is greater than or equal to 2. If so, the method determines the long-term stable transmission power of the remaining n-1 onshore connection transformers (excluding the failed transformer) and generates a power limiting command. The method then measures the DC active power on the offshore side in real time, generates an emergency power reduction command based on the power limiting command, and controls the offshore DC active power to decrease to the long-term stable transmission power. Thus, when a failure of the onshore connection transformer limits the maximum DC transmission power, the method prioritizes reducing the output of the offshore wind farm without disconnecting operating equipment, thereby reducing the flexible DC power and maintaining the stable and safe operation of the system. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of a flexible direct power transmission system for offshore wind power.

[0036] Figure 2 A flowchart illustrating the steps of a flexible DC power emergency limiting method;

[0037] Figure 3 A schematic diagram of the overall process of a flexible DC power emergency limiting method;

[0038] Figure 4 This is a structural block diagram of a flexible DC power emergency limiting device. Detailed Implementation

[0039] This invention provides a flexible DC power emergency limiting method, device, electronic device, and storage medium to solve or partially solve the technical problem of how to promptly reduce the power transmitted from the wind farm via flexible DC to below the long-term transmission capacity of the onshore connection transformer when an onshore fault occurs, thereby avoiding damage to the remaining connection transformers of the onshore station.

[0040] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0041] As an example, large-capacity offshore wind power transmitted via flexible DC transmission is an important technological means to achieve efficient long-distance, large-scale transmission of clean energy. Multiple interconnecting transformers have their grid-side and valve-side terminals connected to the same electrical point, meaning they operate directly in parallel under normal conditions. During normal operation, the valve-side and grid-side terminals of these transformers are directly connected in parallel. This configuration not only improves system redundancy and flexibility but also effectively balances load distribution, ensuring efficient operation and power quality of the entire wind power transmission system.

[0042] However, the sending end of offshore wind power's flexible DC transmission is an isolated system and does not control DC active power. In other words, the DC transmission itself lacks active power control capabilities. Active power limitation is primarily achieved through power limiting at the wind farm. Under this operating mode, if one onshore transformer fails and goes out of service, all power will be transferred to the remaining operating transformers. In this situation, operation can continue for short periods (minutes or less), but not long-term. If the power transmitted from the wind farm via flexible DC cannot be reduced to below the long-term transmission capacity of the operating transformers in time, the remaining onshore transformers will eventually be damaged.

[0043] Therefore, one of the core inventive points of this invention is to propose a flexible DC power emergency limiting method. When a failure of the onshore connecting transformer limits the maximum DC transmission power, the output of the offshore wind farm is promptly and preferentially reduced without disconnecting the operating equipment to decrease the flexible DC power, thereby maintaining the stable and safe operation of the system. When the offshore wind farm power reduction fails, the flexible DC power is reduced by precisely disconnecting the offshore connecting transformer. This ensures the safety of the operating equipment and improves the safety and stability of the offshore wind power flexible DC transmission system.

[0044] Taking the example of configuring three interconnecting transformers on both the offshore and onshore sides. (Refer to...) Figure 1 The diagram shows a structural schematic of an offshore wind power flexible direct transmission system provided in an embodiment of the present invention.

[0045] It can be seen that the offshore wind power flexible DC transmission system includes at least one offshore connection transformer and one onshore connection transformer of equal number. The offshore wind farm is connected to the offshore converter station via submarine collection cables. The AC side of the offshore converter station is equipped with three connection transformers connected in parallel. The offshore converter station is connected to the onshore converter station via a DC cable. The AC side of the onshore converter station is also equipped with three connection transformers connected in parallel.

[0046] In actual operation, when one connecting transformer at the offshore converter station fails and goes out of service, or when two connecting transformers successively go out of service, the flexible DC transmission will automatically implement power reduction measures for the offshore wind farm, but there is no need for DC transmission shutdown. If all three connecting transformers go out of service, the flexible DC transmission will be directly shut down.

[0047] When one connecting transformer at the onshore converter station is out of service due to a fault, or when two connecting transformers are successively taken out of service, the flexible DC transmission system needs to reduce the active power of the offshore wind farm, but there is no need for DC transmission shutdown. If all three connecting transformers at the onshore converter station are taken out of service, the flexible DC transmission system will be directly shut down.

[0048] exist Figure 1 Based on the offshore wind power flexible direct transmission system shown, and referring to Figure 2 The diagram illustrates a flowchart of a flexible DC power emergency limiting method provided by an embodiment of the present invention, which may specifically include the following steps:

[0049] Step 201: When a fault occurs in the onshore connecting transformer, determine whether the number n of the onshore connecting transformers that were in operation before the fault is greater than or equal to 2.

[0050] In the specific implementation, when a fault occurs in the onshore connecting transformer, it is necessary to first determine whether the number of onshore connecting transformers n that were in operation before the fault was greater than or equal to 2, and then execute subsequent control actions based on the determination result.

[0051] In one scenario, when the number of onshore connected transformers n that were in operation before the fault was 1, an automatic interlocking action was directly executed to shut down the offshore wind power flexible direct transmission system.

[0052] In another scenario, when there are two or more onshore connected transformers in operation before the fault, steps 202 to 203 are executed to achieve emergency power limitation of the system.

[0053] Step 202: If yes, determine the long-term stable transmission power of n-1 onshore interconnection transformers other than the faulty onshore interconnection transformer, and generate a power limiting command.

[0054] When there are 2 or more onshore connection transformers in operation before the fault, it is necessary to determine the long-term stable transmission power of the n-1 onshore connection transformers other than the faulty onshore connection transformer, and generate a power limiting command.

[0055] Combination Figure 1 Each onshore interconnecting transformer is connected in parallel to the onshore control and protection device (also known as the onshore DC control and protection system) of the onshore converter station. The onshore control and protection device is then connected to the offshore control and protection device (also known as the offshore DC control and protection system) of the offshore converter station via a DC submarine cable. In the specific implementation, the long-term stable transmission power of n-1 onshore interconnecting transformers (excluding the faulty onshore transformer) is determined, and a power limiting command is generated. This can include: detecting the long-term stable transmission power of the n-1 onshore interconnecting transformers (excluding the faulty onshore transformer) when a fault occurs through the onshore control and protection device; generating a power limiting command based on the long-term stable transmission power through the onshore control and protection device; and transmitting the power limiting command to the offshore control and protection device based on DC inter-station communication.

[0056] In one possible scenario, if two or more connected transformers simultaneously fail to operate during DC operation, this likely indicates a very extreme fault condition, potentially threatening the safe and stable operation of the transformers and the DC system. Therefore, for safety reasons, when multiple connected transformers fail simultaneously, a direct DC interlocking action can be implemented to shut down the entire system.

[0057] In practice, when the number of onshore connected transformers n that were in operation before the fault is greater than or equal to 2, and two or more onshore connected transformers fail simultaneously on the onshore side, an automatic interlocking action is directly executed to shut down the offshore wind power flexible direct transmission system and avoid causing greater losses or accidents.

[0058] Step 203: Measure the DC active power on the sea side in real time, generate an emergency power reduction command based on the power limitation command, and automatically control the DC active power on the sea side to be reduced to the long-term stable transmission power based on the emergency power reduction command.

[0059] Once the power limiting command is generated, the DC active power on the offshore side can be measured in real time. An emergency power reduction command is generated based on the power limiting command, and based on the emergency power reduction command, the DC active power on the offshore side is automatically reduced to the long-term stable transmission power that the remaining connected transformers on the onshore side need to withstand.

[0060] Combination Figure 1 Each offshore transformer corresponds to the energy management system of an offshore wind farm area. All energy management systems are connected in parallel to the offshore wind farm's Automatic Generation Control (AGC). The AGC, in turn, is connected to the offshore control and protection equipment.

[0061] In specific implementation, the DC active power on the offshore side is measured in real time, an emergency power reduction command is generated based on the power limitation command, and the DC active power on the offshore side is automatically reduced to the long-term stable transmission power based on the emergency power reduction command. This can include: when the offshore control and protection device receives the power limitation command, it synchronously measures the DC active power on the offshore side in real time; the offshore control and protection device extracts the long-term stable transmission power from the power limitation command, generates an emergency power reduction command based on the long-term stable transmission power, and sends the emergency power reduction command to the automatic power control system; the automatic power control system distributes the emergency power reduction command to each energy management system, so as to control the power reduction of the corresponding offshore wind farm through each offshore connection transformer, so as to reduce the DC active power on the offshore side to the long-term stable transmission power.

[0062] In a further optional embodiment, if the marine control and protection device detects that the DC active power on the marine side has not been successfully reduced to the long-term stable transmission power after a preset time period (e.g., 5 minutes) of power reduction control, it controls the automatic disconnection of one of the marine connection transformers from at least one marine connection transformer, so as to achieve emergency power reduction by directly disconnecting the power on the marine side.

[0063] Furthermore, after automatically disconnecting one offshore connecting transformer through the offshore control and protection device, the wind turbines of the offshore wind farm connected to the disconnected offshore connecting transformer are shut down to reduce the total power fed into the offshore wind power flexible DC transmission system, thereby reducing the DC active power on the offshore side to the long-term stable transmission power.

[0064] Next, combine Figure 1 The technical solutions provided in the above embodiments will be briefly described below.

[0065] The onshore converter station adopts a parallel structure of three interconnected transformers. Each interconnected transformer has a certain overload capacity, such as a minute-level overload capacity at a 2 p.u. power level.

[0066] When all three connecting transformers of the onshore converter station are running together, if one connecting transformer fails, all power will be automatically transferred to the remaining two connecting transformers, resulting in overload.

[0067] The land-based control and protection device of the flexible DC system detected that the DC power exceeded the maximum power that the remaining two connected transformers could transmit continuously, and will initiate power limiting measures. First, the land-based control and protection device sends a power limiting command to the marine control and protection device through DC inter-station communication.

[0068] After receiving the power limitation command, the marine control and protection device synchronously measures the DC active power in real time.

[0069] The offshore control and protection device first issues an emergency power reduction command to the automatic power control system (AGC) of the offshore wind farm. After receiving the command, the AGC sends instructions to the energy management system of each offshore wind farm area to automatically control the active power of the offshore wind farm to reduce it to the power level that can be continuously transmitted by two onshore transformers.

[0070] Under normal circumstances, after receiving an instruction, the automatic power control system (AGC) of an offshore wind farm can reduce the active power of the offshore wind farm to a level that can be continuously transmitted by two onshore transformers within one minute, which is within the overload capacity of the onshore transformers.

[0071] If, within approximately 5 minutes, the offshore control and protection device detects that the total DC power has not been successfully reduced to a level that can be continuously transmitted by the two onshore transformers, the device will automatically disconnect one of the three parallel transformers at the offshore converter station (at this time, the power restrictions on the remaining transformers can be lifted, allowing the power to be restored to the level before the power reduction adjustment). The offshore wind turbines connected to the busbar of the disconnected parallel transformer will be shut down, and the total power fed from the offshore wind farm to the flexible DC system will be reduced, ensuring that the active power of the offshore wind farm is reduced to a level that can be continuously transmitted by the two onshore transformers.

[0072] When two connecting transformers of an onshore converter station are running together, if one connecting transformer fails, all power will be automatically transferred to the remaining connecting transformer, resulting in overload.

[0073] The land-based control and protection device of the flexible DC system detected that the DC power exceeded the maximum power that the remaining connected transformer could transmit continuously, and will initiate power limiting measures. First, the land-based control and protection device sends a power limiting command to the marine control and protection device through DC inter-station communication.

[0074] After receiving the power limitation command, the marine control and protection device synchronously measures the DC active power in real time.

[0075] The offshore control and protection device first sends an emergency power reduction command to the automatic power control system (AGC) of the offshore wind farm. After receiving the command, the AGC sends instructions to the energy management system of each offshore wind farm area to automatically control the active power of the offshore wind farm to reduce it to the power level that can be continuously transmitted by one onshore transformer.

[0076] Under normal circumstances, after receiving an instruction, the automatic power control system (AGC) of an offshore wind farm can reduce the active power of the offshore wind farm to a power level that can be continuously transmitted by one onshore transformer within one minute, which is within the overload capacity of the onshore transformer.

[0077] If, within approximately 5 minutes, the offshore control and protection device detects that the total DC power has not been successfully reduced to the power level that can be continuously transmitted by one onshore transformer, the device will automatically disconnect two of the three parallel transformers of the offshore converter station (one disconnected this time, plus the one disconnected previously, for a total of two). The offshore wind turbines connected to the busbars of these two disconnected parallel transformers will be shut down, reducing the total power fed from the offshore wind farm to the flexible DC system. This ensures that the active power of the offshore wind farm is reduced to the power level that can be continuously transmitted by one onshore transformer.

[0078] When only one connecting transformer is running at the onshore converter station, if that connecting transformer fails, all DC power will be unable to continue to be transmitted. The DC control and protection device will automatically lock the flexible DC power supply and shut down the entire system.

[0079] This invention proposes a flexible DC power emergency limiting method. When a failure of the onshore connecting transformer limits the maximum DC transmission power, the output of the offshore wind farm is promptly and preferentially reduced without disconnecting in-operation equipment to decrease the flexible DC power, thereby maintaining the stable and safe operation of the system. If the offshore wind farm power reduction fails, the flexible DC power is reduced by precisely disconnecting the offshore connecting transformer. This ensures the safety of in-operation equipment and improves the safety and stability of the offshore wind power flexible DC transmission system.

[0080] For better explanation, refer to Figure 3 This diagram illustrates the overall flow of a flexible DC power emergency limiting method according to an embodiment of the present invention. It should be noted that this embodiment only provides a brief description of the general flow of flexible DC power emergency limiting; the specific implementation process of each step can be understood by referring to the relevant content in the foregoing embodiments, and will not be elaborated upon here. It is understood that the present invention does not impose any limitations on this.

[0081] A fault was detected in the onshore connection transformer on the onshore side;

[0082] When the number of onshore connected transformers n that were in operation before the fault is 1, the automatic interlocking action is executed directly, and the entire system is shut down.

[0083] When the number of onshore connecting transformers n that were in operation before the fault is greater than or equal to 2, and two or more onshore connecting transformers fail at the same time on the onshore side, the automatic interlocking action is executed directly, and the entire system is shut down.

[0084] When the number of onshore connecting transformers n that were in operation before the fault is greater than or equal to 2, and one onshore connecting transformer fails, determine the long-term stable transmission power of the n-1 onshore connecting transformers other than the faulty onshore connecting transformer, and generate a power limiting command.

[0085] The system measures the DC active power on the sea side in real time, generates an emergency power reduction command based on the power limitation command, and automatically controls the DC active power on the sea side to be reduced to the long-term stable transmission power based on the emergency power reduction command.

[0086] If, after a preset period of power reduction control, the marine control and protection device detects that the DC active power on the marine side has not been successfully reduced to the long-term stable transmission power, then the control will automatically disconnect one of the marine connection transformers from at least one marine connection transformer.

[0087] Control the shutdown of wind turbines in offshore wind farms connected to the disconnected offshore transformers to reduce the total power fed into the offshore wind power flexible DC transmission system, thereby reducing the DC active power on the offshore side to the long-term stable transmission power.

[0088] Reference Figure 4 This diagram illustrates a structural block diagram of a flexible DC power emergency limiting device provided by an embodiment of the present invention, applied to an offshore wind power flexible DC transmission system; the offshore wind power flexible DC transmission system includes at least one offshore connection transformer and an onshore connection transformer of equal number; the device may specifically include:

[0089] The fault monitoring unit 401 is used to determine whether the number n of onshore connecting transformers that were in operation before the fault occurred is greater than or equal to 2 when an onshore connecting transformer fault occurs on the onshore side.

[0090] The power limiting instruction generation unit 402 is used to determine the long-term stable transmission power of n-1 onshore interconnection transformers other than the faulty onshore interconnection transformer, and at the same time generate power limiting instructions.

[0091] Emergency power reduction unit 403 is used to measure the DC active power on the sea side in real time, generate an emergency power reduction command based on the power limit command, and automatically control the DC active power on the sea side to be reduced to the long-term stable transmission power based on the emergency power reduction command.

[0092] In one optional embodiment, each of the onshore interconnection transformers is connected in parallel to the onshore control and protection device of the onshore converter station; the onshore control and protection device is connected to the offshore control and protection device of the offshore converter station via a DC submarine cable; the power limiting command generation unit 402 includes:

[0093] The long-term stable transmission power determination unit is used to detect the long-term stable transmission power of n-1 land-based connection transformers (excluding the faulty land-based connection transformer) when a fault occurs through the land-based control and protection device.

[0094] The power limitation command generation and transmission unit is used to generate a power limitation command through the land-based control and protection device based on the long-term stable transmission power, and to transmit the power limitation command to the marine control and protection device based on DC inter-station communication.

[0095] In one optional embodiment, each of the offshore connection transformers corresponds to the energy management system of an offshore wind farm area, and each of the energy management systems is connected in parallel to the automatic power control system of the offshore wind farm. The automatic power control system is connected to the offshore protection device; the emergency power reduction unit 403 includes:

[0096] A real-time DC active power measurement unit is used to synchronously measure the DC active power on the sea side in real time after the marine control and protection device receives the power limitation command.

[0097] An emergency power reduction command generation and transmission unit is used to extract long-term stable transmission power from the power limitation command through the marine control and protection device, generate an emergency power reduction command based on the long-term stable transmission power, and send the emergency power reduction command to the automatic power control system.

[0098] The power reduction control unit is used to distribute the emergency power reduction command to each of the energy management systems through the automatic power control system, so as to reduce the power of the corresponding offshore wind farm through each of the offshore connection transformers, so as to reduce the DC active power on the offshore side to the long-term stable transmission power.

[0099] In one alternative embodiment, the device further includes:

[0100] The offshore connection transformer disconnection unit is used to automatically disconnect one of the offshore connection transformers after a preset period of power reduction control, when the offshore control and protection device detects that the DC active power on the offshore side has not been successfully reduced to the long-term stable transmission power.

[0101] In one alternative embodiment, the device further includes:

[0102] The wind turbine shutdown control unit is used to control the shutdown of wind turbines in offshore wind farms connected to the disconnected offshore transformer, so as to reduce the total power fed into the offshore wind power flexible DC transmission system, and reduce the DC active power on the offshore side to the long-term stable transmission power.

[0103] In one alternative embodiment, the device further includes:

[0104] The first automatic interlocking action execution unit is used to directly execute the automatic interlocking action to shut down the offshore wind power flexible direct transmission system when the number of onshore connected transformers n that were in operation before the fault is 1.

[0105] In one alternative embodiment, the device further includes:

[0106] The second automatic interlocking action unit is used to directly execute the automatic interlocking action to shut down the offshore wind power flexible direct transmission system when the number of onshore connected transformers n that were in operation before the fault was greater than or equal to 2, and when 2 or more onshore connected transformers simultaneously failed.

[0107] As the device embodiment is basically similar to the method embodiment, it is described in a relatively simple way. For relevant details, please refer to the description of the method embodiment above.

[0108] It should be noted that, in order to enable those skilled in the art to better distinguish data of the same type but with different actual meanings, the embodiments of the present invention use "first" and "second" to distinguish and describe some technical features. "First" and "second" are only used to distinguish data and have no other special meaning. It is understood that the present invention does not impose any limitations on them.

[0109] This invention also provides an electronic device, which includes a processor and a memory:

[0110] The memory is used to store program code and transfer the program code to the processor;

[0111] The processor is used to execute the flexible DC power emergency limiting method of any embodiment of the present invention according to instructions in the program code.

[0112] This invention also provides a computer-readable storage medium for storing program code for executing the flexible DC power emergency limiting method of any embodiment of the invention.

[0113] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0114] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this invention are all information and data authorized by the user or fully authorized by all parties. Furthermore, the collection, use and processing of related data must comply with the relevant laws, regulations and standards of the relevant countries and regions, and corresponding operation entry points are provided for users to choose to authorize or refuse.

[0115] In the embodiments provided by this invention, 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 devices or units through some interfaces, and may be electrical, mechanical, or other forms.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flexible DC power emergency limiting method, characterized in that, The method is applied to an offshore wind power flexible direct transmission system; the offshore wind power flexible direct transmission system includes at least one offshore connection transformer and an onshore connection transformer of equal number; the method includes: When a fault occurs in an onshore connecting transformer, determine whether the number n of onshore connecting transformers that were in operation before the fault is greater than or equal to 2. If so, determine the long-term stable transmission power of n-1 onshore connection transformers other than the faulty onshore connection transformer, and generate a power limiting command. The DC active power on the sea side is measured in real time, an emergency power reduction command is generated based on the power limitation command, and the DC active power on the sea side is automatically reduced to the long-term stable transmission power based on the emergency power reduction command.

2. The flexible DC power emergency limiting method according to claim 1, characterized in that, Each of the aforementioned onshore interconnection transformers is connected in parallel to the onshore control and protection device of the onshore converter station; the onshore control and protection device is connected to the offshore control and protection device of the offshore converter station via a DC submarine cable; the determination of the long-term stable transmission power of n-1 onshore interconnection transformers excluding the faulty onshore interconnection transformer, and the generation of power limiting commands, includes: When a fault is detected by the aforementioned land-based control and protection device, the long-term stable transmission power of n-1 land-based connection transformers, excluding the faulty land-based connection transformer, is measured. Based on the long-term stable transmission power, a power limiting command is generated by the land-based control and protection device, and the power limiting command is transmitted to the marine control and protection device based on DC inter-station communication.

3. The flexible DC power emergency limiting method according to claim 2, characterized in that, Each of the offshore connection transformers corresponds to the energy management system of an offshore wind farm area. Each of the energy management systems is connected in parallel to the automatic power control system of the offshore wind farm. The automatic power control system is connected to the offshore protection device. The real-time measurement of the DC active power on the sea side, the generation of an emergency power reduction command based on the power limitation command, and the automatic control of reducing the DC active power on the sea side to the long-term stable transmission power based on the emergency power reduction command, include: After receiving the power limitation command, the marine control and protection device synchronously measures the DC active power on the marine side in real time. The marine control and protection device extracts the long-term stable transmission power from the power limitation command, generates an emergency power reduction command based on the long-term stable transmission power, and sends the emergency power reduction command to the automatic power control system. The automatic power control system distributes the emergency power reduction command to each of the energy management systems, so as to control the power reduction of the corresponding offshore wind farm through each of the offshore connection transformers, so as to reduce the DC active power on the offshore side to the long-term stable transmission power.

4. The flexible DC power emergency limiting method according to claim 2 or 3, characterized in that, Also includes: If, after a preset period of power reduction control, the marine control and protection device detects that the DC active power on the marine side has not been successfully reduced to the long-term stable transmission power, it controls the automatic disconnection of one of the marine connection transformers from the at least one marine connection transformer.

5. The flexible DC power emergency limiting method according to claim 4, characterized in that, After automatically disconnecting one offshore connection transformer via the aforementioned offshore control and protection device, the method further includes: Control the shutdown of wind turbines in offshore wind farms connected to the disconnected offshore transformers to reduce the total power fed into the offshore wind power flexible DC transmission system, thereby reducing the DC active power on the offshore side to the long-term stable transmission power.

6. The flexible DC power emergency limiting method according to claim 1, characterized in that, Also includes: When the number of onshore connected transformers n that were in operation before the fault was 1, the automatic interlocking action was directly executed to shut down the offshore wind power flexible direct transmission system.

7. The flexible DC power emergency limiting method according to claim 1, characterized in that, Also includes: When the number of onshore connecting transformers n that were in operation before the fault is greater than or equal to 2, and two or more onshore connecting transformers fail simultaneously on the onshore side, an automatic interlocking action is directly executed to shut down the offshore wind power flexible direct transmission system.

8. A flexible DC power emergency limiting device, characterized in that, This device is applied to an offshore wind power flexible direct transmission system; the offshore wind power flexible direct transmission system includes at least one offshore connection transformer and an onshore connection transformer of equal quantity; the device includes: The fault monitoring unit is used to determine whether the number n of onshore connected transformers that were in operation before the fault occurred is greater than or equal to 2 when an onshore connected transformer fault occurs on the onshore side. The power limiting command generation unit is used to determine the long-term stable transmission power of n-1 onshore interconnection transformers, excluding the faulty onshore interconnection transformer, and to generate power limiting commands. The emergency power reduction unit is used to measure the DC active power on the sea side in real time, generate an emergency power reduction command based on the power limit command, and automatically control the DC active power on the sea side to be reduced to the long-term stable transmission power based on the emergency power reduction command.

9. An electronic device, characterized in that, The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the flexible DC power emergency limiting method according to any one of claims 1-7 according to the instructions in the program code.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store program code for executing the flexible DC power emergency limiting method according to any one of claims 1-7.

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