A three-side differential protection method and system for submarine cable when performing reactive compensation

Abstract

The application discloses a three-side differential protection method and system for reactive compensation of a submarine cable, and belongs to the technical field of relay protection. The method comprises the following steps: determining the main wiring form of a target submarine cable and a marine high resistance station connected with the target submarine cable; if the main wiring form meets preset requirements, determining the protection configuration mode of the target submarine cable under the main wiring form, and determining the capacitance current compensation mode and protection action logic of the target submarine cable based on the protection configuration mode; generating a three-side differential protection strategy based on the protection configuration mode, the capacitance current compensation mode and the protection action logic determined based on the protection configuration mode, and controlling the target submarine cable to perform three-side differential protection during reactive compensation based on the three-side differential protection strategy. The application provides a sensitive and reliable protection configuration technical scheme for offshore wind power AC grid connection long-distance power transmission.

Description

Technical Field

[0001] The present invention relates to the technical field of relay protection, and more particularly to a three-side differential protection method and system for reactive power compensation of a submarine cable. Background Art

[0002] Developing clean energy is a crucial component of the nation's energy strategy, and developing wind power is an inevitable choice for achieving this goal. Offshore wind power offers distinct advantages over onshore wind power. my country boasts 750 GW of offshore wind resources. As of the end of September 2019, China's cumulative grid-connected offshore wind power capacity reached 5,035,400 kW, ranking third in the world after the United Kingdom and Germany.

[0003] Currently, all major coastal provinces in China with significant offshore wind power development have formulated medium- and long-term development plans for offshore wind power, identifying it as a key area of ​​clean energy. Offshore wind power is transitioning from an "exploratory mode" to a "breakthrough development mode." Large-scale development of offshore wind power inevitably faces the challenge of grid connection. Currently, the selection of offshore wind power grid connection solutions primarily considers factors such as transmission capacity, transmission distance, economic efficiency, reliability, and environmental friendliness. Globally, offshore wind power grid connections are primarily categorized into two main types: high-voltage AC (HVAC) and high-voltage DC (HVDC).

[0004] Offshore wind power AC grid-connected technology is mature, simple in structure, and low in construction cost, but it is limited by the capacitance effect of submarine cables. The capacitance effect of submarine cables generates a large amount of reactive power, which not only reduces the effective load capacity of the cables but also increases the voltage of the grid system. Therefore, line reactors are required to balance the charging reactive power of the cables. These reactors are generally located on the side of offshore substations, onshore substations, or in newly built offshore reactor stations. For reactive power compensation, an offshore reactor station is added in the middle of the submarine cable. To save space on the offshore reactor station platform, the offshore reactor station is generally not equipped with a circuit breaker. Instead, a high-energy reactor is connected directly to the submarine cable via a knife switch.

[0005] For the phase-by-phase current differential protection on both sides of the submarine cable, the PT voltage on the offshore high-voltage reactor side cannot be directly obtained, which makes it difficult to calculate the compensation current of the offshore high-voltage reactor at the offshore high-voltage reactor station, directly affecting the accuracy of the differential protection capacitor current compensation calculation. The differential protection sensitivity may be insufficient, resulting in a decline in the main protection performance. In addition, the offshore high-voltage reactor at the offshore high-voltage reactor station is directly connected to the submarine cable through a knife switch. In the event of a high-voltage reactor failure, an additional remote tripping device needs to be configured to trip the switches on both sides of the submarine cable. The protection configuration and loop wiring are complicated, and the reliability is reduced. Summary of the Invention

[0006] In response to the above problems, the present invention proposes a three-side differential protection method for reactive power compensation of submarine cables, comprising:

[0007] Determining the main connection form between the target submarine cable and the offshore high-voltage resistive station to which the target submarine cable is connected;

[0008] If the main wiring form meets the preset requirements, determining the protection configuration mode of the target submarine cable under the main wiring form, and determining the capacitance current compensation mode and protection action logic of the target submarine cable based on the protection configuration mode;

[0009] Based on the protection configuration mode and the capacitance current compensation mode and protection action logic determined based on the protection configuration mode, a three-side differential protection strategy is generated. Based on the three-side differential protection strategy, the target submarine cable is controlled to perform three-side differential protection during reactive power compensation.

[0010] Optionally, the main connection form is: there is no circuit breaker at the offshore high-voltage transformer station in the middle of the submarine cable, and the offshore high-voltage transformer station is directly connected to the target submarine cable through a knife switch, which meets the preset requirements.

[0011] Optional protection configuration methods include:

[0012] The offshore booster station side, offshore high-voltage reactor side and onshore booster station side connected to the target submarine cable are respectively equipped with double sets of optical fiber phase-splitting current differential protection to form a master-slave differential protection for the target submarine cable;

[0013] Each set of optical fiber phase-splitting current differential protection includes complete backup protection, reclosing protection, and overvoltage and remote trip local discrimination protection.

[0014] The backup protection includes: distance protection and zero-sequence overcurrent protection;

[0015] The local criterion for the overvoltage and remote trip local discrimination protection includes: current sudden change criterion, low current criterion, low power criterion and low power factor criterion;

[0016] The master-slave differential protection is specifically as follows: the offshore booster station side and the onshore booster station side respectively put into differential protection, distance protection and zero-sequence overcurrent protection, while the offshore high-voltage reactor side only puts into differential protection, and the offshore booster station side, the offshore high-voltage reactor side and the onshore booster station side exit the reclosing protection.

[0017] Optionally, the capacitance current compensation method includes: using a Π-type network semi-compensation method to compensate for the capacitance current of the target submarine cable and the high-impedance current of other lines configured on both sides of the target cable.

[0018] Optional, protection action logic, including:

[0019] If the target submarine cable between the offshore booster station and the offshore high-voltage reactor station, the offshore high-voltage reactor station busbar, or the target submarine cable between the offshore high-voltage reactor station and the onshore booster station fails, the three-side differential protection of the target submarine cable will be activated, and the three-side differential protection switches on both sides of the target submarine cable will be tripped;

[0020] If a fault occurs in the high-voltage transformer area of ​​the offshore high-voltage transformer station, and the protection action is initiated after the high-voltage transformer is pumped out, and the protection action signal is input into other protection actions or remote transmission contacts of the three-side differential protection device of the offshore high-voltage transformer station, the three-side differential protection switches on both sides of the target submarine cable will be tripped through the remote tripping function of the three-side differential protection of the target submarine cable.

[0021] On the other hand, the present invention also proposes a three-side differential protection system for reactive power compensation of a submarine cable, comprising:

[0022] a wiring form determining unit, configured to determine a main wiring form between a target submarine cable and an offshore high-voltage resistive station to which the target submarine cable is connected;

[0023] a configuration scheme determining unit, configured to determine whether the main wiring form meets preset requirements; if so, determine a protection configuration mode of the target submarine cable under the main wiring form; and based on the protection configuration mode, determine a capacitance current compensation mode and protection action logic of the target submarine cable;

[0024] A control unit is configured to generate a three-side differential protection strategy based on the protection configuration mode and the capacitance current compensation mode and protection action logic determined based on the protection configuration mode, and control the target submarine cable to perform three-side differential protection during reactive power compensation based on the three-side differential protection strategy.

[0025] Optionally, the main connection form is: there is no circuit breaker at the offshore high-voltage transformer station in the middle of the submarine cable, and the offshore high-voltage transformer station is directly connected to the target submarine cable through a knife switch, which meets the preset requirements.

[0026] Optional protection configuration methods include:

[0027] The offshore booster station side, offshore high-voltage reactor side and onshore booster station side connected to the target submarine cable are respectively equipped with double sets of optical fiber phase-splitting current differential protection to form a master-slave differential protection for the target submarine cable;

[0028] Each set of optical fiber phase-splitting current differential protection includes complete backup protection, reclosing protection, and overvoltage and remote trip local discrimination protection.

[0029] The backup protection includes: distance protection and zero-sequence overcurrent protection;

[0030] The local criterion for the overvoltage and remote trip local discrimination protection includes: current sudden change criterion, low current criterion, low power criterion and low power factor criterion;

[0031] The master-slave differential protection is specifically as follows: the offshore booster station side and the onshore booster station side respectively put into differential protection, distance protection and zero-sequence overcurrent protection, while the offshore high-voltage reactor side only puts into differential protection, and the offshore booster station side, the offshore high-voltage reactor side and the onshore booster station side exit the reclosing protection.

[0032] Optionally, the capacitance current compensation method includes: using a Π-type network semi-compensation method to compensate for the capacitance current of the target submarine cable and the high-impedance current of other lines configured on both sides of the target cable.

[0033] Optional, protection action logic, including:

[0034] If the target submarine cable between the offshore booster station and the offshore high-voltage reactor station, the offshore high-voltage reactor station busbar, or the target submarine cable between the offshore high-voltage reactor station and the onshore booster station fails, the three-side differential protection of the target submarine cable will be activated, and the three-side differential protection switches on both sides of the target submarine cable will be tripped;

[0035] If a fault occurs in the high-voltage transformer area of ​​the offshore high-voltage transformer station, and the protection action is initiated after the high-voltage transformer is pumped out, and the protection action signal is input into other protection actions or remote transmission contacts of the three-side differential protection device of the offshore high-voltage transformer station, the three-side differential protection switches on both sides of the target submarine cable will be tripped through the remote tripping function of the three-side differential protection of the target submarine cable.

[0036] In yet another aspect, the present invention further provides a computing device comprising: one or more processors;

[0037] a processor for executing one or more programs;

[0038] When the one or more programs are executed by the one or more processors, the above-described method is implemented.

[0039] In another aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed, the method described above is implemented.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention provides a three-side differential protection method for reactive power compensation on a submarine cable, comprising: determining the main connection type between a target submarine cable and the offshore high-voltage reactor station to which the target submarine cable is connected; if the main connection type meets preset requirements, determining a protection configuration mode for the target submarine cable under the main connection type, and based on the protection configuration mode, determining a capacitive current compensation mode and protection action logic for the target submarine cable; generating a three-side differential protection strategy based on the protection configuration mode and the capacitive current compensation mode and protection action logic determined based on the protection configuration mode; and controlling the target submarine cable to perform three-side differential protection during reactive power compensation based on the three-side differential protection strategy. The present invention provides a sensitive and reliable protection configuration technical solution for offshore wind power AC grid-connected long-distance power transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a flow chart of the method of the present invention;

[0043] Figure 2 This is a circuit diagram of the offshore high-voltage reactor station without a circuit breaker in the method of the present invention, where the energy extraction high-voltage reactor is directly connected to the submarine cable through a knife switch;

[0044] Figure 3 The offshore high-voltage reactor station of the method of the present invention has a circuit breaker, and the circuit diagram of the energy extraction high-voltage reactor is directly connected to the submarine cable through a knife switch;

[0045] Figure 4 This is a diagram of the differential protection configuration for three sides of a submarine cable according to the method of the present invention;

[0046] Figure 5 The equivalent circuit diagram of the steady-state capacitance current compensation method of the present invention is as follows;

[0047] Figure 6 The equivalent circuit diagram of the transient capacitance current compensation method of the present invention is as follows;

[0048] Figure 7 This is the logic diagram of the differential protection action on three sides of the submarine cable according to the method of the present invention;

[0049] Figure 8 It is a structural diagram of the system of the present invention. DETAILED DESCRIPTION

[0050] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to provide a thorough and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments shown in the accompanying drawings is not intended to limit the present invention. In the accompanying drawings, identical elements are denoted by the same reference numerals.

[0051] Unless otherwise specified, the terms used herein (including technical terms) have the meanings commonly understood by those skilled in the art. In addition, it is understood that terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0052] Example 1:

[0053] The present invention proposes a three-side differential protection method for reactive power compensation of submarine cables. Figure 1 Shown, including:

[0054] Step 1: Determine the main connection form between the target submarine cable and the offshore high-voltage anti-interference station to which the target submarine cable is connected;

[0055] Step 2: If the main wiring form meets the preset requirements, determine the protection configuration mode of the target submarine cable under the main wiring form, and determine the capacitance current compensation mode and protection action logic of the target submarine cable based on the protection configuration mode;

[0056] Step 3: Based on the protection configuration mode, the capacitance current compensation mode determined based on the protection configuration mode, and the protection action logic, a three-side differential protection strategy is generated; based on the three-side differential protection strategy, the target submarine cable is controlled to perform three-side differential protection during reactive power compensation.

[0057] Among them, the main connection form is: there is no circuit breaker at the offshore high-voltage transformer station in the middle of the submarine cable, and when the offshore high-voltage transformer station draws energy and is directly connected to the target submarine cable through a knife switch, the preset requirements are met.

[0058] The protection configuration methods include:

[0059] The offshore booster station side, offshore high-voltage reactor side and onshore booster station side connected to the target submarine cable are respectively equipped with double sets of optical fiber phase-splitting current differential protection to form a master-slave differential protection for the target submarine cable;

[0060] Each set of optical fiber phase-splitting current differential protection includes complete backup protection, reclosing protection, and overvoltage and remote trip local discrimination protection.

[0061] The backup protection includes: distance protection and zero-sequence overcurrent protection;

[0062] The local criterion for the overvoltage and remote trip local discrimination protection includes: current sudden change criterion, low current criterion, low power criterion and low power factor criterion;

[0063] The master-slave differential protection is specifically as follows: the offshore booster station side and the onshore booster station side respectively put into differential protection, distance protection and zero-sequence overcurrent protection, while the offshore high-voltage reactor side only puts into differential protection, and the offshore booster station side, the offshore high-voltage reactor side and the onshore booster station side exit the reclosing protection.

[0064] Among them, the capacitive current compensation method includes: using the Π-type network semi-compensation method to compensate for the capacitive current of the target submarine cable and the high-impedance current of other lines configured on both sides of the target cable.

[0065] The protection action logic includes:

[0066] If the target submarine cable between the offshore booster station and the offshore high-voltage reactor station, the offshore high-voltage reactor station busbar, or the target submarine cable between the offshore high-voltage reactor station and the onshore booster station fails, the three-side differential protection of the target submarine cable will be activated, and the three-side differential protection switches on both sides of the target submarine cable will be tripped;

[0067] If a fault occurs in the high-voltage transformer area of ​​the offshore high-voltage transformer station, and the protection action is initiated after the high-voltage transformer is pumped out, and the protection action signal is input into other protection actions or remote transmission contacts of the three-side differential protection device of the offshore high-voltage transformer station, the three-side differential protection switches on both sides of the target submarine cable will be tripped through the remote tripping function of the three-side differential protection of the target submarine cable.

[0068] The present invention will be further described below with reference to specific examples:

[0069] In the specific example, the above steps 1 and 2 can be divided into the following small steps for implementation, including:

[0070] Step 1: Confirm that the main wiring of the offshore high-voltage reactor station is in the form of no circuit breaker at the offshore high-voltage reactor station, and the energy extraction high-voltage reactor is directly connected to the submarine cable through a knife switch;

[0071] Step 2-1: Determine the protection configuration method for this main wiring form;

[0072] Step 2-2: Determine the capacitance current compensation method for this protection configuration method;

[0073] Step 2-3: Determine the protection action logic of this protection configuration method.

[0074] Among them, the specific process of step 1 is: first, it is necessary to determine that the main wiring of the offshore high-voltage reactor station is in the form of no circuit breaker at the offshore high-voltage reactor station, and the energy extraction high-voltage reactor is directly connected to the submarine cable through a knife switch. The primary electrical main wiring form directly determines the relay protection configuration scheme, and the three-side differential protection configuration method is applicable to the above-mentioned main wiring form. In actual engineering applications, when the submarine cable passes through the intermediate offshore high-voltage reactor station for reactive power compensation, from the perspective of economy, compactness and reliability, the optimal solution is to use the offshore high-voltage reactor station without a circuit breaker, and the energy extraction high-voltage reactor is directly connected to the submarine cable through a knife switch. In addition, there is also a main wiring form in which the offshore high-voltage reactor station is equipped with a circuit breaker. The relevant main wirings are as follows: Figure 2 、 Figure 3 shown.

[0075] The specific process of step 2-1 is as follows: The configuration method of differential protection on three sides of submarine cable under this main wiring form is as follows: Figure 4 As shown in the figure, the submarine cable offshore booster station, offshore high-voltage reactor station and onshore booster station sides should be equipped with two sets of optical fiber phase-splitting current differential protection to form a master-slave three-side differential.

[0076] Each set of protection includes complete backup protection (distance protection, zero-sequence overcurrent protection), reclosing and optional overvoltage and remote tripping local discrimination protection (local criteria include current mutation, low current, low power, low power factor, etc.). Differential protection, distance protection, and zero-sequence overcurrent protection are put into operation on the offshore booster station and onshore booster station sides; only differential protection is put into operation on the offshore high-voltage reactor side; and reclosing protection on all three sides is withdrawn. In order to prevent false operation due to abnormal conditions such as system operation, faults, and DC grounding, important circuits such as remote tripping and opening of differential protection on the three sides of the submarine cable should be equipped with high-power re-operating relays, or software anti-error measures should be adopted. In addition, the differential protection on the three sides of the submarine cable should be coordinated with the main protection of other equipment to eliminate the dead zone of the main protection.

[0077] The specific process of step 2-2 is as follows: Under this protection configuration method, the equivalent circuit diagram of the differential protection capacitor current compensation on the three sides of the submarine cable is as follows: Figure 5 、 Figure 6 As shown in the figure, the three-side differential protection can directly obtain the high-voltage reactor current at the offshore high-voltage reactor station side. There is no need to compensate for the high-voltage reactor current. It is only necessary to compensate for the capacitive current of the submarine cable itself and the high-voltage reactor current of other lines configured at both ends. The capacitive current compensation adopts the π-type network semi-compensation method.

[0078] for Figure 5 The equivalent circuit diagram of the steady-state capacitor current compensation method is shown in the figure. The capacitor current that needs to be compensated is:

[0079]

[0080]

[0081] Where: are the voltages at the k-terminal and j-terminal respectively; is the zero-sequence voltage at terminals k and j; X C1 、X C0 is the line positive sequence and zero sequence capacitive reactance; X lk1 、X lj1 X lk0 X lj0 are the positive-sequence reactance and zero-sequence reactance of the high-voltage reactor at the k-end and j-end.

[0082] for Figure 6 The equivalent circuit diagram of the transient capacitance current compensation method based on the time domain is shown. The current of each capacitor and reactance can be calculated by the following formula:

[0083]

[0084]

[0085] Where: i c is the current passing through each capacitor, C is the capacitance value, u c is the voltage drop across the capacitor.

[0086] After finding the current of each capacitor and reactance, the compensation capacitance current of each phase of the line can be obtained. Taking phase a as an example, the capacitance current that needs to be compensated on both sides is calculated as follows:

[0087]

[0088]

[0089] Where: C pg is the line-to-ground capacitance, C pp is the phase-to-phase capacitance, The capacitance current to ground calculated at the k-terminal and the j-terminal respectively, The inductor current calculated at the k-terminal and j-terminal respectively is: It is the capacitive current that needs to be compensated at the k and j terminals in the differential protection.

[0090] The specific process of steps 2-3 is as follows: Figure 7As shown in the figure, when a fault occurs in the submarine cable from the offshore booster station to the offshore high-voltage reactor station (point k1), the offshore high-voltage reactor station busbar (point k2), or the submarine cable from the offshore high-voltage reactor station to the onshore booster station (point k3), the differential protection on all three sides of the submarine cable can quickly trip the switches on both sides of the submarine cable. When a fault occurs in the high-voltage reactor extraction area (point k4) of the offshore high-voltage reactor station, the high-voltage reactor extraction protection quickly operates and inputs the protection action signal into the "other protection action" or "remote transmission" contacts of the three-side differential protection device of the offshore high-voltage reactor station, tripping the switches on both sides of the submarine cable through the remote tripping function of the three-side differential protection. For a high-voltage reactor extraction fault, the fault characteristics may not be obvious on both sides of the submarine cable. In order to prevent the failure of switches on both sides of the submarine cable due to the action of the high-voltage transformer protection, when the action signal of the high-voltage transformer protection is input into the "other protection action" contact of the three-side differential protection device of the offshore high-voltage transformer station, the "remote trip controlled by the starting element" control word in the three-side differential protection device of the offshore substation and the onshore substation side should be set to "0", that is, the remote tripping is not locked by the starting element.

[0091] For submarine cables, a reactive power compensation method is adopted in which an offshore high-voltage reactor station is added in the middle. When the offshore high-voltage reactor station has no circuit breaker and the energy extraction high-voltage reactor is directly connected to the submarine cable through a knife switch, the differential protection configuration scheme on both sides commonly used in the project cannot directly obtain the PT voltage on the offshore high-voltage reactor station side, resulting in the inability to accurately calculate the compensation current of the energy extraction high-voltage reactor at the offshore high-voltage reactor station, which directly affects the accuracy of the differential protection capacitance current compensation calculation. The sensitivity of the differential protection may be insufficient, resulting in a decrease in the performance of the main protection. At the same time, the energy extraction high-voltage reactor fault requires an additional remote tripping device to trip the switches on both sides of the submarine cable, which makes the protection configuration and loop wiring complicated and reduces reliability.

[0092] The present invention actually provides a three-side differential protection configuration method when a submarine cable passes through an intermediate offshore high-voltage reactor station for reactive power compensation, realizes the precise calculation of capacitive current compensation, and can greatly improve the sensitivity of differential protection; at the same time, it simplifies the protection configuration and circuit design when the high-voltage reactor protection action is linked to the switches on both sides of the submarine cable, providing a sensitive and reliable protection configuration technical solution for offshore wind power AC grid-connected long-distance power transmission.

[0093] Example 2:

[0094] The present invention also proposes a three-side differential protection system 200 for reactive power compensation of submarine cables, such as Figure 8 Shown, including:

[0095] The connection type determination unit 201 is used to determine the main connection type of the target submarine cable and the offshore high-voltage resistive station connected to the target submarine cable;

[0096] a configuration scheme determining unit 202 for determining whether the main wiring form meets preset requirements; if so, determining a protection configuration mode for the target submarine cable under the main wiring form; and determining a capacitance current compensation mode and protection action logic for the target submarine cable based on the protection configuration mode;

[0097] The control unit 203 is configured to generate a three-side differential protection strategy based on the protection configuration mode and the capacitance current compensation mode and protection action logic determined based on the protection configuration mode, and control the target submarine cable to perform three-side differential protection during reactive power compensation based on the three-side differential protection strategy.

[0098] Among them, the main connection form is: there is no circuit breaker at the offshore high-voltage transformer station in the middle of the submarine cable, and when the offshore high-voltage transformer station draws energy and is directly connected to the target submarine cable through a knife switch, the preset requirements are met.

[0099] The protection configuration methods include:

[0100] The offshore booster station side, offshore high-voltage reactor side and onshore booster station side connected to the target submarine cable are respectively equipped with double sets of optical fiber phase-splitting current differential protection to form a master-slave differential protection for the target submarine cable;

[0101] Each set of optical fiber phase-splitting current differential protection includes complete backup protection, reclosing protection, and overvoltage and remote trip local discrimination protection.

[0102] The backup protection includes: distance protection and zero-sequence overcurrent protection;

[0103] The local criterion for the overvoltage and remote trip local discrimination protection includes: current sudden change criterion, low current criterion, low power criterion and low power factor criterion;

[0104] The master-slave differential protection is specifically as follows: the offshore booster station side and the onshore booster station side respectively put into differential protection, distance protection and zero-sequence overcurrent protection, while the offshore high-voltage reactor side only puts into differential protection, and the offshore booster station side, the offshore high-voltage reactor side and the onshore booster station side exit the reclosing protection.

[0105] Among them, the capacitive current compensation method includes: using the Π-type network semi-compensation method to compensate for the capacitive current of the target submarine cable and the high-impedance current of other lines configured on both sides of the target cable.

[0106] The protection action logic includes:

[0107] If the target submarine cable between the offshore booster station and the offshore high-voltage reactor station, the offshore high-voltage reactor station busbar, or the target submarine cable between the offshore high-voltage reactor station and the onshore booster station fails, the three-side differential protection of the target submarine cable will be activated, and the three-side differential protection switches on both sides of the target submarine cable will be tripped;

[0108] If a fault occurs in the high-voltage transformer area of ​​the offshore high-voltage transformer station, and the protection action is initiated after the high-voltage transformer is pumped out, and the protection action signal is input into other protection actions or remote transmission contacts of the three-side differential protection device of the offshore high-voltage transformer station, the three-side differential protection switches on both sides of the target submarine cable will be tripped through the remote tripping function of the three-side differential protection of the target submarine cable.

[0109] The present invention provides a sensitive and reliable protection configuration technical solution for offshore wind power AC grid-connected long-distance power transmission.

[0110] Example 3:

[0111] Based on the same inventive concept, the present invention also provides a computer device, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of the method in the above embodiment.

[0112] Example 4:

[0113] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It can be understood that the computer-readable storage medium here can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space that stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space. These instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the method in the above embodiment.

[0114] It will be understood by those skilled in the art that the embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention may be implemented in various computer languages, for example, the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0115] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0116] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0117] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0118] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0119] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A three-side differential protection method for reactive power compensation of submarine cables, characterized in that: The method comprises: Determining the main connection form between the target submarine cable and the offshore high-voltage resistive station to which the target submarine cable is connected; If the main wiring form meets the preset requirements, determining the protection configuration mode of the target submarine cable under the main wiring form, and determining the capacitance current compensation mode and protection action logic of the target submarine cable based on the protection configuration mode; generating a three-side differential protection strategy based on the protection configuration mode, a capacitance current compensation mode determined based on the protection configuration mode, and a protection action logic; and controlling the target submarine cable to perform three-side differential protection during reactive power compensation based on the three-side differential protection strategy; The protection configuration method includes: The offshore booster station side, offshore high-voltage reactor side and onshore booster station side connected to the target submarine cable are respectively equipped with double sets of optical fiber phase-splitting current differential protection to form a master-slave differential protection for the target submarine cable; Each set of optical fiber phase-splitting current differential protection includes complete backup protection, reclosing protection, and overvoltage and remote trip local discrimination protection. The backup protection includes: distance protection and zero-sequence overcurrent protection; The local criterion for the overvoltage and remote trip local discrimination protection includes: current sudden change criterion, low current criterion, low power criterion and low power factor criterion; The master-slave differential protection is specifically as follows: the offshore booster station side and the onshore booster station side are respectively activated for differential protection, distance protection and zero-sequence overcurrent protection, while the offshore high-voltage reactor side is only activated for differential protection, and the offshore booster station side, the offshore high-voltage reactor side and the onshore booster station side are deactivated for reclosing protection; The capacitive current compensation method includes: using a π-type network semi-compensation method to compensate for the capacitive current of the target submarine cable and the high-impedance current of other lines configured on both sides of the target submarine cable.

2. The three-side differential protection method according to claim 1, characterized in that: The main connection form is: there is no circuit breaker at the offshore high-voltage transformer station in the middle of the submarine cable, and when the offshore high-voltage transformer station draws energy and is directly connected to the target submarine cable through a knife switch, the preset requirements are met.

3. The three-side differential protection method according to claim 1, characterized in that: The protection action logic includes: If the target submarine cable between the offshore booster station and the offshore high-voltage reactor station, the offshore high-voltage reactor station busbar, or the target submarine cable between the offshore high-voltage reactor station and the onshore booster station fails, the three-side differential protection of the target submarine cable will be activated, and the three-side differential protection switches on both sides of the target submarine cable will be tripped; If a fault occurs in the high-voltage transformer area of ​​the offshore high-voltage transformer station, and the protection action is initiated after the high-voltage transformer is pumped out, and the protection action signal is input into other protection actions or remote transmission contacts of the three-side differential protection device of the offshore high-voltage transformer station, the three-side differential protection switches on both sides of the target submarine cable will be tripped through the remote tripping function of the three-side differential protection of the target submarine cable.

4. A three-side differential protection system for reactive power compensation of submarine cables, characterized in that: The system comprises: a wiring form determining unit, configured to determine a main wiring form between a target submarine cable and an offshore high-voltage resistive station to which the target submarine cable is connected; a configuration scheme determining unit, configured to determine whether the main wiring form meets preset requirements; if so, determine a protection configuration mode of the target submarine cable under the main wiring form; and based on the protection configuration mode, determine a capacitance current compensation mode and protection action logic of the target submarine cable; a control unit, configured to generate a three-side differential protection strategy based on the protection configuration mode, a capacitance current compensation mode determined based on the protection configuration mode, and a protection action logic, and control the target submarine cable to perform three-side differential protection during reactive power compensation based on the three-side differential protection strategy; The protection configuration method includes: The offshore booster station side, offshore high-voltage reactor side and onshore booster station side connected to the target submarine cable are respectively equipped with double sets of optical fiber phase-splitting current differential protection to form a master-slave differential protection for the target submarine cable; Each set of optical fiber phase-splitting current differential protection includes complete backup protection, reclosing protection, and overvoltage and remote trip local discrimination protection. The backup protection includes: distance protection and zero-sequence overcurrent protection; The local criterion for the overvoltage and remote trip local discrimination protection includes: current sudden change criterion, low current criterion, low power criterion and low power factor criterion; The master-slave differential protection is specifically as follows: the offshore booster station side and the onshore booster station side are respectively activated for differential protection, distance protection and zero-sequence overcurrent protection, while the offshore high-voltage reactor side is only activated for differential protection, and the offshore booster station side, the offshore high-voltage reactor side and the onshore booster station side are deactivated for reclosing protection; The capacitive current compensation method includes: using a π-type network semi-compensation method to compensate for the capacitive current of the target submarine cable and the high-impedance current of other lines configured on both sides of the target submarine cable.

5. The three-side differential protection system according to claim 4, characterized in that: The main connection form is: there is no circuit breaker at the offshore high-voltage transformer station in the middle of the submarine cable, and when the offshore high-voltage transformer station draws energy and is directly connected to the target submarine cable through a knife switch, the preset requirements are met.

6. The three-side differential protection system according to claim 4, characterized in that: The protection action logic includes: If the target submarine cable between the offshore booster station and the offshore high-voltage reactor station, the offshore high-voltage reactor station busbar, or the target submarine cable between the offshore high-voltage reactor station and the onshore booster station fails, the three-side differential protection of the target submarine cable will be activated, and the three-side differential protection switches on both sides of the target submarine cable will be tripped; If a fault occurs in the high-voltage transformer area of ​​the offshore high-voltage transformer station, and the protection action is initiated after the high-voltage transformer is pumped out, and the protection action signal is input into other protection actions or remote transmission contacts of the three-side differential protection device of the offshore high-voltage transformer station, the three-side differential protection switches on both sides of the target submarine cable will be tripped through the remote tripping function of the three-side differential protection of the target submarine cable.

7. A computer device, characterized in that: include: one or more processors; a processor for executing one or more programs; When the one or more programs are executed by the one or more processors, the method according to any one of claims 1 to 3 is implemented.

8. A computer-readable storage medium, characterized in that A computer program is stored thereon, and when the computer program is executed, the method according to any one of claims 1 to 3 is implemented.

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