Failure protection method, device and equipment for alternating-current circuit breaker and medium

Abstract

The invention relates to the technical field of power transmission systems, and discloses an AC circuit breaker failure protection method, device, equipment and medium, and the method comprises the steps: collecting the network side and valve side feature data of a back-to-back flexible DC power transmission system under various fault conditions, so as to construct a multi-condition electrical feature data set; determining a direct current control protection action type of the back-to-back flexible direct current power transmission system according to each fault working condition type so as to establish a failure protection action criterion set in combination with the various fault working conditions and the multi-working-condition electrical characteristic data set; obtaining failure starting types of the alternating-current circuit breaker under various fault working conditions, and combining the failure starting types with a failure protection action criterion set to construct a self-adaptive failure protection strategy; when it is monitored in real time that the back-to-back flexible direct current power transmission system breaks down, an alternating current circuit breaker is controlled to carry out failure protection based on a self-adaptive failure protection strategy; according to the method, a circuit breaker does not need to be newly added, and faults can be timely isolated only by newly adding criteria.

Description

Technical Field

[0001] This invention relates to the field of power transmission system technology, and in particular to a method, device, equipment and medium for AC circuit breaker failure protection. Background Technology

[0002] Back-to-back flexible DC transmission systems typically employ symmetrical single-pole connections, with the connecting transformer using a YNd11 connection. The valve side utilizes a star-connected reactor to construct the neutral point, which is then grounded via high resistance. If a fault occurs in the valve-side bridge arm of the connecting transformer, the DC control and protection system issues a command to trip the grid-side circuit breaker of that transformer and lock the converter valve. If the circuit breaker fails to operate, the circuit breaker failure protection must be activated and the fault clearing range expanded to ensure reliable disconnection between the connecting transformer and the grid. However, because this system uses a high-resistance grounded neutral point, the grid-side circuit breaker may lack fault electrical quantities during a circuit breaker failure, and the conventional circuit breaker failure protection failure criteria (phase current / negative sequence current / zero sequence current) may not be met, posing a risk that the failure protection cannot be activated. Currently, the common solution to this problem is to add a circuit breaker to the circuit, but this significantly increases the operating cost of the equipment.

[0003] Therefore, how to ensure that a back-to-back flexible DC transmission system can accurately and promptly disconnect a fault after a single-phase circuit breaker fails without the addition of a circuit breaker has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] This invention provides a method, device, equipment, and medium for AC circuit breaker failure protection, which solves the problem of how to ensure that a back-to-back flexible DC transmission system can accurately and promptly disconnect the fault after a single-phase circuit breaker failure without adding a circuit breaker.

[0005] To solve the above-mentioned technical problems, the first aspect of the present invention provides an AC circuit breaker failure protection method, comprising: collecting grid-side characteristic data and valve-side characteristic data of a back-to-back flexible DC transmission system under various fault conditions to construct a multi-condition electrical characteristic dataset; In response to each of the aforementioned fault conditions, determine the DC control protection action type of the back-to-back flexible DC transmission system; A failure protection action criterion set is established based on the various fault conditions, the multi-condition electrical feature dataset, and the DC control protection action type. Obtain the failure start type of the AC circuit breaker under each of the aforementioned fault conditions, and combine it with the failure protection action criterion set to construct an adaptive failure protection strategy; When a fault is detected in the back-to-back flexible DC transmission system in real time, the AC circuit breaker is controlled to perform fault protection based on the adaptive failure protection strategy.

[0006] As one preferred embodiment, the fault conditions include valve-side single-phase ground fault, valve-side two-phase ground fault, valve-side two-phase ungrounded fault, valve-side three-phase ground fault, and valve-side three-phase ungrounded fault. The grid-side characteristic data includes grid-side instantaneous current, grid-side zero-sequence current, grid-side negative-sequence current, grid-side instantaneous voltage, grid-side zero-sequence voltage, and grid-side negative-sequence voltage. The valve-side characteristic data includes valve-side instantaneous current, valve-side zero-sequence current, valve-side negative-sequence current, valve-side instantaneous voltage, valve-side zero-sequence voltage, and valve-side negative-sequence voltage.

[0007] As one preferred embodiment, the DC control protection action type includes zero-sequence overvoltage and valve-side differential current; wherein, determining the DC control protection action type of the back-to-back flexible DC transmission system in response to each of the fault conditions includes: when the fault condition is a valve-side single-phase ground fault, the DC control protection action type of the back-to-back flexible DC transmission system is the zero-sequence overvoltage. When the fault condition is a two-phase ground fault on the valve side, a two-phase ungrounded fault on the valve side, a three-phase ground fault on the valve side, or a three-phase ungrounded fault on the valve side, the DC control protection action type of the back-to-back flexible DC transmission system is the valve side differential current.

[0008] As one preferred embodiment, the establishment of a failure protection action criterion set through the various fault conditions, the multi-condition electrical feature dataset, and the DC control protection action type includes: When the fault condition is the first fault type, the zero-sequence overvoltage protection output signal is used as the first failure signal, and the grid-side negative sequence voltage exceeding the preset voltage threshold is used as the first failure protection action criterion; the first fault type is the valve-side single-phase ground fault. When the fault condition is the second fault type, the DC differential protection output signal is used as the second failure signal, and the grid-side current exceeding the preset current threshold is used as the second failure protection action criterion; the second fault type is the valve-side two-phase ground short circuit and grid-side B-phase failure, the valve-side two-phase ungrounded short circuit and grid-side B-phase failure, the valve-side three-phase ground short circuit, or the valve-side three-phase ungrounded short circuit; When the fault condition is the third fault type, the DC differential protection output signal is used as the third failure signal, and the grid-side negative sequence voltage exceeding the preset voltage threshold is used as the third failure protection action criterion; the third fault type is any fault condition other than the valve-side single-phase ground fault and grid-side C-phase failure, the first fault type, and the second fault type. A set of failure protection action criteria is established based on the first failure protection action criterion, the second failure protection action criterion, and the third failure protection action criterion.

[0009] As one preferred embodiment, the failure start type includes passive start and active start; wherein, passive start is caused by external tripping control to cause the AC circuit breaker to fail to start, and active start is caused by the AC circuit breaker's own failure due to protection action.

[0010] As one preferred embodiment, the step of combining the failure protection action criterion set with the adaptive failure protection strategy includes: When the failure start type is passive start, if it is determined that the second failure protection action criterion or the third failure protection action criterion is met, then the first duration of the external tripping order and the second duration of the grid-side negative sequence voltage are detected. If it is determined that the first duration satisfies a preset duration rule and the second duration satisfies a preset time threshold, then the AC circuit breaker is tripped.

[0011] As one preferred embodiment, the adaptive failure protection strategy further includes: When it is detected that the side circuit breaker and the interrupt circuit breaker of the AC circuit breaker simultaneously receive the external tripping command, and both the side circuit breaker and the interrupt circuit breaker meet the tripping conditions, the position nodes of the side circuit breaker and the interrupt circuit breaker are detected. Upon receiving information from the location node indicating the existence of a breakpoint, the corresponding circuit breaker is tripped.

[0012] A second aspect of the present invention provides an AC circuit breaker failure protection device, comprising: The feature set construction module is used to collect grid-side and valve-side feature data of back-to-back flexible DC transmission systems under various fault conditions in order to construct a multi-condition electrical feature dataset. A type determination module is used to determine the DC control protection action type of the back-to-back flexible DC transmission system in response to each of the aforementioned fault conditions. The criterion set establishment module is used to establish a failure protection action criterion set through each of the aforementioned fault conditions, the multi-condition electrical feature dataset, and the DC control protection action type; The strategy generation module is used to obtain the failure start type of the AC circuit breaker under each of the aforementioned fault conditions, and combine it with the failure protection action criterion set to construct an adaptive failure protection strategy. The failure protection module is used to control the AC circuit breaker to perform failure protection based on the adaptive failure protection strategy when a fault is detected in the back-to-back flexible DC transmission system in real time.

[0013] A third aspect of the present invention provides an electronic device including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor, when executing the computer program, implements the AC circuit breaker failure protection method as described above.

[0014] A fourth aspect of the present invention provides a computer-readable storage medium comprising a stored computer program, wherein when the device containing the computer-readable storage medium executes the computer program, it implements the AC circuit breaker failure protection method as described above.

[0015] Compared with the prior art, the beneficial effects of the embodiments of the present invention are at least one of the following: (1) By collecting network-side and valve-side characteristic data under various fault conditions, the electrical characteristics of the system under different fault conditions can be fully reflected, which provides a solid foundation for establishing accurate failure protection action criteria and improves the accuracy of fault judgment. (2) An adaptive failure protection strategy is constructed by combining the DC control protection action type under each fault condition and the failure start type of AC circuit breaker under each fault condition. This strategy can automatically adjust the protection action according to different fault conditions, thereby enhancing the adaptability and flexibility of the protection strategy. (3) Based on the adaptive failure protection strategy, the AC circuit breaker can be quickly controlled to perform failure protection, which can significantly shorten the fault clearing time and reduce the impact of the fault on the system; and no new circuit breaker is required. Only the criteria need to be added to the AC circuit breaker failure protection device to achieve timely isolation of the fault and ensure the safe operation of the equipment. Attached Figure Description

[0016] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments 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.

[0017] Figure 1 This is a flowchart of an AC circuit breaker failure protection method provided in a certain embodiment of the present invention; Figure 2 This is a structural diagram of an AC circuit breaker failure protection device provided in a certain embodiment of the present invention; Figure 3 This is a structural diagram of an electronic device provided in a certain embodiment of the present invention; Figure label: Among them, 10 is the feature set construction module; 20 is the type determination module; 30 is the criterion set establishment module; 40 is the strategy generation module; 50 is the failure protection module; 5000 is the electronic device; 5001 is the processor; 5002 is the bus; 5003 is the memory; and 5004 is the transceiver. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings and examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] In the description of this application, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0020] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. The terms "vertical," "horizontal," "left," "right," "upper," "lower," and similar expressions used herein are for illustrative purposes only and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0021] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is merely for describing specific embodiments and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0022] A back-to-back flexible DC transmission system (VSC-HVDC system) is a high-voltage direct current (HVDC) transmission system that employs voltage source converter (VSC) technology. Its key feature is that the two ends of the transmission system are not directly connected by DC transmission lines; instead, they are connected back-to-back through converter stations, achieving flexible DC interconnection between two AC power grids. With the widespread application of flexible DC transmission technology in inter-regional power grid interconnection, the back-to-back converter stations, as energy exchange hubs between DC and AC systems, directly impact power grid security due to their operational reliability.

[0023] Traditional AC circuit breaker failure protection suffers from the following problems: a single current criterion cannot cover the fault characteristics of DC systems; the AC protection start-up logic is missing after DC protection reset; and the negative sequence voltage characteristics caused by DC faults are not fully utilized. Based on this, this invention constructs a multi-condition electrical feature dataset, innovatively integrates DC control signals and AC electrical quantities, and combines them with failure start-up types to propose an adaptive failure protection strategy. This strategy effectively solves the problem of signal loss due to DC protection reset and the challenge of circuit breaker failure to operate under harsh DC system conditions, without requiring additional circuit breakers and only needing to add a criterion to the AC circuit breaker failure protection device.

[0024] In one embodiment, such as Figure 1 As shown, the first aspect of the present invention provides a method for protecting an AC circuit breaker from failure, comprising: S1. Collect grid-side and valve-side characteristic data of the back-to-back flexible DC transmission system under various fault conditions to construct a multi-condition electrical characteristic dataset; wherein, the fault conditions include valve-side single-phase ground fault, valve-side two-phase ground fault, valve-side two-phase ungrounded fault, valve-side three-phase ground fault, and valve-side three-phase ungrounded fault; grid-side characteristic data includes grid-side instantaneous current, grid-side zero-sequence current, grid-side negative-sequence current, grid-side instantaneous voltage, grid-side zero-sequence voltage, and grid-side negative-sequence voltage; valve-side characteristic data includes valve-side instantaneous current, valve-side zero-sequence current, valve-side negative-sequence current, valve-side instantaneous voltage, valve-side zero-sequence voltage, and valve-side negative-sequence voltage.

[0025] Specifically, multiple measuring points are set up in the back-to-back flexible DC transmission system to simulate the failure of the grid-side circuit breaker under fault conditions such as single-phase grounding, two-phase grounding, three-phase grounding, two-phase short circuit, and three-phase short circuit (i.e., valve-side single-phase grounding short circuit, valve-side two-phase grounding short circuit, valve-side two-phase ungrounded short circuit, valve-side three-phase grounding short circuit, and valve-side three-phase ungrounded short circuit) on the valve side of the connecting transformer. A steady-state transmission of 1500MW of active power is simulated, and a permanent fault occurs at 4s of simulation time. The DC protection will issue blocking and tripping commands based on changes in electrical quantities, simulating different failure conditions of the grid-side circuit breaker. The simulated values ​​of grid-side current / voltage and valve-side current / voltage are observed and recorded. In this context, "grid side" refers to the grid side of a back-to-back flexible DC transmission system, while "valve side" refers to the converter valve side. Measurement points on the grid side are grid-side voltage and current measurement points, located on the grid side of the converter, i.e., the side directly connected to the AC grid, adjacent to the AC input port of the converter. These points are used to measure the voltage and current parameters of the converter's grid side, i.e., grid-side characteristic data. Measurement points on the valve side include valve-side voltage measurement points and valve-side current measurement points. The valve-side voltage measurement point is located on the valve side of the converter, i.e., the connection point between the converter and the DC link, specifically between the converter output and the DC capacitor. It primarily measures the voltage parameters on the converter's valve side. The valve-side current measurement point is also located on the valve side of the converter, typically on the connection line between the converter and the DC line or DC equipment, i.e., near the output of the right-side converter. It is used to measure the current parameters on the converter's valve side.

[0026] For back-to-back flexible DC transmission systems, there are 15 fault conditions on the valve side, as shown in Table 1: Table 1 Valve-side Fault Conditions of Back-to-Back Flexible DC Transmission Systems After simulating the above faults, the network-side characteristic data and valve-side characteristic data were recorded respectively; among them, the network-side characteristic data under multiple fault conditions are shown in Table 2: Table 2. Network-side characteristic data under multiple fault conditions. As shown in Table 2, for a single-phase failure due to a phase A ground fault, the grid-side current is 0. For a phase AB ground fault, the grid-side current is 0 when phases A and C fail; however, there will be current on the grid side under other operating conditions. In operating conditions where current exists, the failure protection can operate based on the current flow. In operating conditions where no current exists, additional criteria are needed to ensure the correct operation of the failure protection; otherwise, the persistent presence of unisolated fault points will jeopardize the safe and stable operation of the equipment.

[0027] The valve-side characteristic data under multiple fault conditions are shown in Table 3: Table 3 Valve-side characteristic data under multiple fault conditions As shown in Table 3, for the above-mentioned faults, we should pay attention to the valve side current and valve side voltage. The valve side current is 0, and the valve side voltage has a zero-sequence component.

[0028] Next, the characteristic data for each fault condition are organized according to a unified format to construct a multi-condition electrical characteristic dataset. By collecting grid-side and valve-side characteristic data under various fault conditions, this invention can comprehensively reflect the electrical characteristics of the system under different fault states, thereby improving the accuracy of fault diagnosis. Based on the multi-condition electrical characteristic dataset, the changing patterns of electrical characteristics under different fault conditions can be analyzed, thereby optimizing the protection strategy of back-to-back flexible DC transmission systems.

[0029] S2. In response to each of the aforementioned fault conditions, determine the DC control protection action type of the back-to-back flexible DC transmission system; wherein, the DC control protection action type includes zero-sequence overvoltage and valve-side differential current; In one embodiment, step S2 includes: When the fault condition is a single-phase ground fault on the valve side, the DC control protection action type of the back-to-back flexible DC transmission system is the zero-sequence overvoltage. When the fault condition is a two-phase ground fault on the valve side, a two-phase ungrounded fault on the valve side, a three-phase ground fault on the valve side, or a three-phase ungrounded fault on the valve side, the DC control protection action type of the back-to-back flexible DC transmission system is the valve side differential current.

[0030] Specifically, the DC control protection action type (also known as the failure start criterion) differs for different types of fault conditions. For back-to-back flexible DC transmission, the protection types for different fault conditions are shown in Table 4: Table 4 DC control protection actions under multiple fault conditions As shown in Table 4, when a single-phase ground fault occurs on the valve side, i.e., when the main wiring topology with a large resistance grounding on the valve side experiences this fault, the current in the fault path is 0, the valve-side differential current cannot operate accurately, the zero-sequence voltage of the backup protection is greater than or equal to the set value, and the AC circuit breaker trips after several hundred milliseconds. Therefore, the DC control protection action type under this fault is set to zero-sequence overvoltage. However, when a two-phase or three-phase ground / ungrounded fault occurs on the valve side, there is a fault loop path, and the valve-side differential current operates within milliseconds, tripping the AC circuit breaker. Therefore, the DC control protection action type under a multi-phase fault on the valve side is set to valve-side differential current.

[0031] This invention determines the corresponding DC control protection action type according to different fault conditions, which can realize targeted protection for back-to-back flexible DC transmission systems, thereby more effectively identifying and handling faults, improving the safety and stability of the system, avoiding unnecessary investment in protection equipment, reducing system construction and operation and maintenance costs, reducing false tripping and failure to trip, and improving the reliability and economy of protection.

[0032] S3. Establish a failure protection action criterion set based on the fault conditions, the multi-condition electrical feature dataset, and the DC control protection action type. In one embodiment, step S3 includes: When the fault condition is the first fault type, the zero-sequence overvoltage protection output signal is used as the first failure signal, and the grid-side negative sequence voltage exceeding the preset voltage threshold is used as the first failure protection action criterion; the first fault type is the valve-side single-phase ground fault. When the fault condition is the second fault type, the DC differential protection output signal is used as the second failure signal, and the grid-side current exceeding the preset current threshold is used as the second failure protection action criterion; the second fault type is the valve-side two-phase ground short circuit and grid-side B-phase failure, the valve-side two-phase ungrounded short circuit and grid-side B-phase failure, the valve-side three-phase ground short circuit, or the valve-side three-phase ungrounded short circuit; When the fault condition is the third fault type, the DC differential protection output signal is used as the third failure signal, and the grid-side negative sequence voltage exceeding the preset voltage threshold is used as the third failure protection action criterion; the third fault type is any fault condition other than the valve-side single-phase ground fault and grid-side C-phase failure, the first fault type, and the second fault type. A set of failure protection action criteria is established based on the first failure protection action criterion, the second failure protection action criterion, and the third failure protection action criterion.

[0033] Specifically, this invention can classify different fault conditions into three types of criteria: When the fault condition is a single-phase ground fault on the valve side, this invention establishes a system where the zero-sequence overvoltage protection output signal is used as the first failure signal, and the grid-side negative-sequence voltage exceeding a preset voltage threshold is used as the first failure protection action criterion. In other words, when a zero-sequence overvoltage protection output signal is detected and the grid-side negative-sequence voltage exceeds the preset voltage threshold, it is determined that the protection device has failed, triggering the failure protection action. When any of the following fault conditions occur: a two-phase ground fault on the valve side and a failure of phase B on the grid side; a two-phase unground fault on the valve side and a failure of phase B on the grid side; a three-phase ground fault on the valve side; or a three-phase unground fault on the valve side, this invention establishes a second failure signal based on the DC differential protection output signal caused by the valve side differential current, and a second failure protection action criterion based on the grid side current (three-phase current, zero-sequence current, and negative-sequence current) exceeding a preset current threshold. In other words, when a DC differential protection output signal is detected and the grid side current exceeds the preset current threshold, it is determined that the protection device has failed, triggering the failure protection action. When any of the following fault conditions occur: a two-phase ground fault on the valve side and phase A on the grid side fails; a two-phase ground fault on the valve side and phase C on the grid side fails; a two-phase ungrounded short circuit on the valve side and phase A on the grid side fails; or a two-phase ungrounded short circuit on the valve side and phase C on the grid side fails, this invention establishes a third failure signal based on the DC differential protection output signal caused by the valve side differential current, and a third failure protection action criterion based on the grid side negative sequence voltage exceeding a preset voltage threshold. In other words, when a DC differential protection output signal is detected and the grid side negative sequence voltage exceeds a preset voltage threshold, it is determined that the protection device has failed, triggering the failure protection action. Finally, the failure protection action criteria formulated for different fault types will be organized to establish a failure protection action criterion set. This criterion set should include all possible fault conditions and their corresponding failure protection action criteria, so as to quickly and accurately determine whether the protection device has failed when a fault occurs and take corresponding measures.

[0034] This invention, by establishing specific failure protection action criteria for different fault conditions, can more accurately identify the failure status of protection devices, improve protection reliability, and provide additional safety assurance for back-to-back flexible DC transmission systems. Setting different failure protection action criteria according to different fault conditions helps optimize the system's protection strategy, better adapt to the system's operating characteristics and fault features, and improve the overall protection effect. Furthermore, by combining DC signals (protection output signal type) and AC electrical quantities (grid-side current, grid-side voltage) as criteria, timely fault isolation can be achieved without adding new circuit breakers.

[0035] S4. Obtain the failure start type of the AC circuit breaker under each of the aforementioned fault conditions, and combine it with the failure protection action criterion set to construct an adaptive failure protection strategy; the failure start type includes passive start and active start; wherein, the passive start is caused by external tripping control to cause the AC circuit breaker to start and fail, and the active start is caused by the AC circuit breaker's own failure due to the protection action.

[0036] In one embodiment, the step of constructing an adaptive failure protection strategy by combining it with the failure protection action criterion set includes: When the failure start type is passive start, if it is determined that the second failure protection action criterion or the third failure protection action criterion is met, then the first duration of the external tripping order and the second duration of the grid-side negative sequence voltage are detected. If it is determined that the first duration satisfies a preset duration rule and the second duration satisfies a preset time threshold, then the AC circuit breaker is tripped.

[0037] Specifically, this invention classifies the failure start-up types of AC circuit breakers in back-to-back flexible DC transmission systems at various fault conditions into two types: passive start-up, where the AC circuit breaker fails to start due to external tripping control, and active start-up, where the AC circuit breaker fails to start due to its own protection action. The failure start-up type can be determined by monitoring the source of the AC circuit breaker's tripping command (external tripping command or its own protection action).

[0038] For DC zero-sequence overvoltage protection or current differential start failure protection, after a single-phase failure of the circuit breaker, there may be a situation where the zero-sequence overvoltage protection judgment or the current differential signal disappears. At this time, the DC protection operation resets, the AC circuit breaker does not receive the trip command, the failure start fails, and it will not trip even if the operation signal exists.

[0039] The current criterion for circuit breaker failure protection is generally taken as 0.06~0.08IN. Currently, the minimum grid-side current is 0.041 / (1500 / 525 / 1.732*1.414)=0.018pu, and the current characteristic is not obvious. Current cannot be used as a condition for failure protection operation. After introducing a new characteristic quantity, for single-phase failure under different fault conditions, the original failure start criterion disappears after the failure. At this time, the AC circuit breaker failure protection start condition disappears, and some faults require the introduction of a new failure protection start signal at the same time. For multi-phase faults, after a valve-side fault, the DC protection valve-side differential current signal will recover. For a single-phase ground fault, C-phase failure, the zero-sequence overvoltage signal will recover. At this time, if the failure protection criterion disappears after detecting the trip command, it is determined that the zero-sequence voltage signal or the current differential signal disappeared after it existed. When the negative sequence voltage exists for a longer than a fixed delay, the AC circuit breaker can be tripped directly.

[0040] In other words, when the failure start type is passive start, if the second failure protection action criterion or the third failure protection action criterion is met, the first duration of the external trip order and the second duration of the grid-side negative sequence voltage are detected; if the first duration is determined to meet the preset duration rule (i.e., it exists and then disappears) and the second duration meets the preset time threshold (this value needs to take into account the AC system fault backup protection clearing time and the AC circuit breaker mechanical opening and closing time, preferably 500ms), the output AC circuit breaker is tripped; if only the negative sequence voltage exists and no trip order is detected, the AC circuit breaker does not trip.

[0041] This invention, by combining the failure start type (passive start) and the failure protection action criterion set (second and third failure protection action criteria) with AC electrical quantities, breaks through the problem of signal disappearance caused by DC protection reset. Furthermore, it detects the duration of external tripping orders and grid-side negative sequence voltage, enabling more accurate determination of whether the AC circuit breaker has truly failed, avoiding false tripping due to momentary disturbances or misoperation, and improving the accuracy of protection actions. The adaptive failure protection strategy can dynamically adjust the protection action according to the actual fault conditions and failure start type, ensuring that the circuit breaker can be tripped quickly and accurately when the AC circuit breaker truly fails, preventing the fault from escalating, thereby enhancing the reliability and stability of the system.

[0042] In one embodiment, the adaptive failure protection strategy further includes: When it is detected that the side circuit breaker and the interrupt circuit breaker of the AC circuit breaker simultaneously receive the external tripping command, and both the side circuit breaker and the interrupt circuit breaker meet the tripping conditions, the position nodes of the side circuit breaker and the interrupt circuit breaker are detected. Upon receiving information from the location node indicating the existence of a breakpoint, the corresponding circuit breaker is tripped.

[0043] Specifically, when both the side circuit breaker and the interrupted circuit breaker of an AC circuit breaker receive trip orders simultaneously, and both have negative sequence voltages (meaning the electrical characteristic data and protection action signals meet the requirements), the side and interrupted circuit breakers cannot be distinguished and will trip simultaneously. At this time, their position node feedback is detected. Position node feedback typically indicates the actual state of the circuit breaker (e.g., closed or open), including: side circuit breaker: line-side PT disconnection signal; interrupted circuit breaker: bus-side CT disconnection signal. The received position node feedback information is then analyzed: if the feedback indicates a break (i.e., the circuit breaker has not been correctly closed or opened), it is determined that the corresponding circuit breaker needs to be tripped, and the system will issue a trip command to trip the corresponding side circuit breaker or interrupted circuit breaker.

[0044] This invention enables coordinated operation of protection strategies by simultaneously monitoring the status of side circuit breakers and interrupt circuit breakers and making decisions based on location node feedback, which helps improve the system's ability to cope with complex fault conditions. Through precise location node feedback detection, circuit breakers can be prevented from tripping under non-fault conditions, reducing unnecessary operations and power outage losses, and improving the continuity and stability of power supply.

[0045] Meanwhile, the single-phase failure protection logic of the AC circuit breaker is as follows: it only initiates the failure of this circuit breaker in response to an external tripping command. If the device continuously meets the single-phase tripping condition, the failure tripping protection action of this circuit breaker will trip all three phases of this circuit breaker after the "failure tripping time of this circuit breaker" has elapsed; if this circuit breaker still does not trip, the delay failure protection action of "failure tripping time of adjacent circuit breakers" will trip all surrounding related circuit breakers. In other words, the single-phase failure protection logic of the AC circuit breaker is as follows: when an external trip order is detected and the first failure protection action criterion is met, and the zero-sequence current action or negative-sequence current action is detected, and the fault phase current is also greater than the failure phase current, then a three-level tripping logic is executed: after receiving the trip order, if the "follow-trip this circuit breaker" control word is enabled, then the circuit breaker will be tripped after a 10ms delay; if it does not trip, then the AC circuit breaker will be tripped three times after a T1 delay (e.g., 100ms); if it still does not trip, then the adjacent circuit breaker of the AC circuit breaker will be tripped after a T2 delay (e.g., 200ms).

[0046] The three-phase failure protection logic of the AC circuit breaker includes both external tripping commands that trigger the failure of this circuit breaker and protection actions that trigger the failure of this circuit breaker. 1) External trip command to initiate circuit breaker failure: If the device continuously meets the three-phase trip conditions, the three phases of this circuit breaker will be tripped in conjunction with the failure trip protection action after the "failure trip time of this circuit breaker"; if this circuit breaker still fails to trip, all surrounding related circuit breakers will be tripped after the "failure trip time of adjacent circuit breakers" time delay failure protection action; 2) Circuit breaker protection action to initiate circuit breaker failure: If the device continuously meets the circuit breaker protection action (charging overcurrent protection, three-phase inconsistency protection after the "inconsistency start failure" control word is activated) conditions, and simultaneously meets any three-phase trip criterion, the three phases of this circuit breaker will be tripped in conjunction with the failure trip protection action after the "failure trip time of this circuit breaker"; if this circuit breaker still fails to trip, all surrounding related circuit breakers will be tripped after the "failure trip time of adjacent circuit breakers" time delay failure protection action. When a three-phase trip signal is received (three-phase trip input or three separate phase trip input), if any of the following criteria are met simultaneously, and the "follow-trip this circuit breaker" control word is activated, the three phases of this circuit breaker will be tripped after a 10ms delay: 1) Zero-sequence current element or negative-sequence current element operates; 2) The current of any phase is greater than the current setting of the failed phase. In other words, upon receiving an external trip order, and determining if the failure protection action criteria for a three-phase fault are met, it will determine whether the three-phase follow-trip condition is met. If so, the AC circuit breaker will trip after a T1 delay (e.g., 100ms). If it does not trip, the adjacent circuit breaker of the AC circuit breaker will trip after a T2 delay (e.g., 200ms). For active initiation and determination of failure protection action criteria for three-phase faults, if the monitoring detects that the protection action conditions of this circuit breaker (charging overcurrent protection / inconsistency protection action) and any three-phase tripping criterion are met simultaneously, the AC circuit breaker will trip after a delay of T1 (e.g., 100ms). If it does not trip, the adjacent circuit breaker of the AC circuit breaker will trip after a delay of T2 (e.g., 200ms).

[0047] For single-phase grounding failure of phase C under special operating conditions: if the zero-sequence voltage signal is detected to return, the negative-sequence voltage criterion is activated, and the adjacent circuit breaker is tripped directly when the negative-sequence voltage > 25kV for 500ms. This invention, by introducing a new criterion, can still accurately identify and trip the next-level circuit breaker after a single-phase circuit breaker failure, promptly clearing the fault and ensuring the safe and stable operation of the DC transmission system. Simultaneously, it fully considers the characteristic quantities of different phase failures under various fault conditions, performs hierarchical processing of the consequences of various fault handling, and identifies several types of faults requiring new criterions, ensuring accurate operation under various types of faults on the valve side of the DC transmission system.

[0048] S5. When a fault is detected in the back-to-back flexible DC transmission system in real time, the AC circuit breaker is controlled to perform fault protection based on the adaptive failure protection strategy. In back-to-back flexible DC transmission systems, high-precision sensors (such as voltage transformers (PTs) and current transformers (CTs) are deployed to record real-time voltage and current waveforms at microsecond-level sampling rates (e.g., 1 MHz). Faults are detected when instantaneous waveform jumps occur. High-frequency components can also be extracted using FFT or wavelet transform, and fault occurrence can be monitored through changes in harmonic content. The specific fault monitoring process is not limited here. Compression algorithms (such as wavelet transform) are used to compress the original waveforms before and after the fault, reducing storage space while retaining key feature information. After a fault occurs, the voltage and current waveforms of the initial 1 / 4 cycle are extracted; this time period contains the initial fault characteristics and is crucial for failure protection. Feature data from the waveforms, such as time-domain features (peak value, root mean square value, waveform distortion rate), are extracted. The system employs a combination of frequency domain features (e.g., amplitude and phase of high-frequency components extracted via Fast Fourier Transform) and time-frequency features (joint time-frequency features extracted using wavelet transform or Hilbert-Huang transform). Based on these features, dynamic time warping (DTW), cosine similarity, or deep learning models (such as Siamese networks) are used to calculate the similarity between the current fault waveform and historical waveforms in a historical failure event waveform library. This library contains information such as fault type, time, location, and waveform characteristics of historical failure event waveforms. A similarity threshold is set; if the similarity between the current waveform and a historical waveform is below the threshold, it is considered abnormal. Based on the comparison results, the fault type and location are quickly identified, and an adaptive failure protection strategy is used to control the corresponding AC circuit breaker at the fault location for failure protection.

[0049] This application addresses the challenge of ensuring accurate and timely fault isolation in a back-to-back flexible DC transmission system after a single-phase circuit breaker failure without adding a circuit breaker. It proposes an AC circuit breaker failure protection method. By collecting grid-side and valve-side characteristic data under various fault conditions, this method comprehensively reflects the electrical characteristics of the system under different fault states, providing a solid foundation for establishing accurate failure protection action criteria and improving fault judgment accuracy. An adaptive failure protection strategy is constructed by combining the DC control protection action types under various fault conditions and the failure initiation types of the AC circuit breaker under these conditions. This strategy automatically adjusts protection actions according to different fault conditions, enhancing the adaptability and flexibility of the protection strategy. Based on this adaptive failure protection strategy, the AC circuit breaker is rapidly controlled for failure protection, significantly shortening fault isolation time and reducing the impact of the fault on the system. Furthermore, no additional circuit breaker is required; only criteria need to be added to the AC circuit breaker failure protection device to achieve timely fault isolation and ensure safe equipment operation.

[0050] It should be noted that although the steps in the flowchart above are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order requirement for the execution of these steps, and they can be executed in other orders.

[0051] In another embodiment, such as Figure 2 As shown, a second aspect of the present invention provides an AC circuit breaker failure protection device, comprising: The feature set construction module 10 is used to collect grid-side feature data and valve-side feature data of back-to-back flexible DC transmission systems under various fault conditions, so as to construct a multi-condition electrical feature dataset. Type determination module 20 is used to determine the DC control protection action type of the back-to-back flexible DC transmission system in response to each of the aforementioned fault conditions. The criterion set establishment module 30 is used to establish a failure protection action criterion set through each of the fault conditions, the multi-condition electrical feature dataset, and the DC control protection action type; The strategy generation module 40 is used to obtain the failure start type of the AC circuit breaker under each of the fault conditions, so as to combine it with the failure protection action criterion set to construct an adaptive failure protection strategy. The failure protection module 50 is used to control the AC circuit breaker to perform failure protection based on the adaptive failure protection strategy when a fault is detected in the back-to-back flexible DC transmission system in real time.

[0052] It should be noted that each module in the aforementioned AC circuit breaker failure protection device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module. For specific limitations regarding the AC circuit breaker failure protection device, please refer to the limitations regarding the AC circuit breaker failure protection method described above; both have the same function and role, and will not be repeated here.

[0053] A third aspect of the present invention provides an electronic device comprising: Processor, memory, and bus; The bus is used to connect the processor and the memory; The memory is used to store operation instructions; The processor is configured to execute instructions by calling the operation instructions, causing the processor to perform operations corresponding to an AC circuit breaker failure protection method as shown in the first aspect of this application.

[0054] In one alternative embodiment, an electronic device is provided, such as Figure 3 As shown, Figure 3 The illustrated electronic device 5000 includes a processor 5001 and a memory 5003. The processor 5001 and the memory 5003 are connected, for example, via a bus 5002. Optionally, the electronic device 5000 may also include a transceiver 5004. It should be noted that in practical applications, the transceiver 5004 is not limited to one type, and the structure of this electronic device 5000 does not constitute a limitation on the embodiments of this application.

[0055] Processor 5001 may be a CPU, a general-purpose processor, a DSP, an ASIC, an FPGA, or other programmable logic device, transistor logic device, hardware component, or any combination thereof. It may implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. Processor 5001 may also be a combination that implements computational functions, such as including one or more microprocessor combinations, a combination of a DSP and a microprocessor, etc.

[0056] Bus 5002 may include a path for transmitting information between the aforementioned components. Bus 5002 may be a PCI bus or an EISA bus, etc. Bus 5002 can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 3 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0057] The memory 5003 may be a ROM or other type of static storage device capable of storing static information and instructions, RAM or other type of dynamic storage device capable of storing information and instructions, or it may be an EEPROM, CD-ROM or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but is not limited thereto.

[0058] The memory 5003 is used to store application code that executes the scheme of this application, and its execution is controlled by the processor 5001. The processor 5001 is used to execute the application code stored in the memory 5003 to implement the content shown in any of the foregoing method embodiments.

[0059] Among them, electronic devices include, but are not limited to: mobile terminals such as mobile phones, laptops, digital radio receivers, PDAs (personal digital assistants), PADs (tablet computers), PMPs (portable multimedia players), and in-vehicle terminals (such as in-vehicle navigation terminals), as well as fixed terminals such as digital TVs and desktop computers.

[0060] The fourth aspect of the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements an AC circuit breaker failure protection method as shown in the first aspect of the present application.

[0061] Another embodiment of this application provides a computer-readable storage medium storing a computer program that, when run on a computer, enables the computer to execute the corresponding content in the aforementioned method embodiments.

[0062] Furthermore, embodiments of the present invention also provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0063] In summary, this invention relates to the field of power transmission system technology, and discloses an AC circuit breaker failure protection method, device, equipment, and medium. It constructs a multi-condition electrical feature dataset by collecting grid-side and valve-side characteristic data of a back-to-back flexible DC transmission system under various fault conditions. Based on each fault condition type, it determines the DC control protection action type of the back-to-back flexible DC transmission system, and combines this data with the various fault conditions and the multi-condition electrical feature dataset to establish a failure protection action criterion set. It obtains the failure start type of the AC circuit breaker under various fault conditions, and combines this data with the failure protection action criterion set to construct an adaptive failure protection strategy. When a fault is detected in the back-to-back flexible DC transmission system in real time, it controls the AC circuit breaker to perform failure protection based on the adaptive failure protection strategy. This invention does not require adding new circuit breakers; only new criteria are needed to achieve timely fault isolation.

[0064] The various embodiments in this specification are described in a progressive manner. For directly identical or similar parts among the embodiments, refer to each other. Each embodiment focuses on its differences from other embodiments. In particular, the device embodiments are basically similar to the method embodiments, so the description is relatively simple; refer to the description of the method embodiments for relevant details. It should be noted that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification.

[0065] The embodiments described above are merely preferred embodiments of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the technical principles of this invention, and these improvements and substitutions should also be considered within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the scope of the claims.

Claims

1. A method for protecting against AC circuit breaker failure, characterized in that, include: Collect grid-side and valve-side characteristic data of back-to-back flexible DC transmission systems under various fault conditions to construct a multi-condition electrical characteristic dataset. In response to each of the aforementioned fault conditions, determine the DC control protection action type of the back-to-back flexible DC transmission system; A failure protection action criterion set is established based on the various fault conditions, the multi-condition electrical feature dataset, and the DC control protection action type. Obtain the failure start type of the AC circuit breaker under each of the aforementioned fault conditions, and combine it with the failure protection action criterion set to construct an adaptive failure protection strategy; When a fault is detected in the back-to-back flexible DC transmission system in real time, the AC circuit breaker is controlled to perform fault protection based on the adaptive failure protection strategy.

2. The AC circuit breaker failure protection method according to claim 1, characterized in that, The fault conditions include valve-side single-phase ground fault, valve-side two-phase ground fault, valve-side two-phase ungrounded fault, valve-side three-phase ground fault, and valve-side three-phase ungrounded fault. The grid-side characteristic data includes grid-side instantaneous current, grid-side zero-sequence current, grid-side negative-sequence current, grid-side instantaneous voltage, grid-side zero-sequence voltage, and grid-side negative-sequence voltage. The valve-side characteristic data includes valve-side instantaneous current, valve-side zero-sequence current, valve-side negative-sequence current, valve-side instantaneous voltage, valve-side zero-sequence voltage, and valve-side negative-sequence voltage.

3. The AC circuit breaker failure protection method according to claim 2, characterized in that, The DC control protection action types include zero-sequence overvoltage and valve-side differential current; among which... The method of determining the DC control protection action type of the back-to-back flexible DC transmission system in response to each of the fault conditions includes: when the fault condition is a single-phase ground fault on the valve side, the DC control protection action type of the back-to-back flexible DC transmission system is the zero-sequence overvoltage. When the fault condition is a two-phase ground fault on the valve side, a two-phase ungrounded fault on the valve side, a three-phase ground fault on the valve side, or a three-phase ungrounded fault on the valve side, the DC control protection action type of the back-to-back flexible DC transmission system is the valve side differential current.

4. The AC circuit breaker failure protection method according to claim 3, characterized in that, The establishment of a failure protection action criterion set through the various fault conditions, the multi-condition electrical feature dataset, and the DC control protection action type includes: When the fault condition is the first fault type, the zero-sequence overvoltage protection output signal is used as the first failure signal, and the grid-side negative sequence voltage exceeding the preset voltage threshold is used as the first failure protection action criterion; the first fault type is the valve-side single-phase ground fault. When the fault condition is the second fault type, the DC differential protection output signal is used as the second failure signal, and the grid-side current exceeding the preset current threshold is used as the second failure protection action criterion; the second fault type is the valve-side two-phase ground short circuit and grid-side B-phase failure, the valve-side two-phase ungrounded short circuit and grid-side B-phase failure, the valve-side three-phase ground short circuit, or the valve-side three-phase ungrounded short circuit; When the fault condition is the third fault type, the DC differential protection output signal is used as the third failure signal, and the grid-side negative sequence voltage exceeding the preset voltage threshold is used as the third failure protection action criterion; the third fault type is any fault condition other than the valve-side single-phase ground fault and grid-side C-phase failure, the first fault type, and the second fault type. A set of failure protection action criteria is established based on the first failure protection action criterion, the second failure protection action criterion, and the third failure protection action criterion.

5. The AC circuit breaker failure protection method according to claim 4, characterized in that, The failure start types include passive start and active start; wherein, the passive start is caused by an external tripping command to cause the AC circuit breaker to fail to start, and the active start is caused by the AC circuit breaker's own failure due to a protection action.

6. The AC circuit breaker failure protection method according to claim 5, characterized in that, The adaptive failure protection strategy is constructed by combining it with the failure protection action criterion set, including: When the failure start type is passive start, if it is determined that the second failure protection action criterion or the third failure protection action criterion is met, then the first duration of the external tripping order and the second duration of the grid-side negative sequence voltage are detected. If it is determined that the first duration satisfies a preset duration rule and the second duration satisfies a preset time threshold, then the AC circuit breaker is tripped.

7. The AC circuit breaker failure protection method according to claim 6, characterized in that, The adaptive failure protection strategy also includes: When it is detected that the side circuit breaker and the interrupt circuit breaker of the AC circuit breaker simultaneously receive the external tripping command, and both the side circuit breaker and the interrupt circuit breaker meet the tripping conditions, the position nodes of the side circuit breaker and the interrupt circuit breaker are detected. Upon receiving information from the location node indicating the existence of a breakpoint, the corresponding circuit breaker is tripped.

8. A circuit breaker failure protection device, characterized in that, include: The feature set construction module is used to collect grid-side and valve-side feature data of back-to-back flexible DC transmission systems under various fault conditions in order to construct a multi-condition electrical feature dataset. A type determination module is used to determine the DC control protection action type of the back-to-back flexible DC transmission system in response to each of the aforementioned fault conditions. The criterion set establishment module is used to establish a failure protection action criterion set through each of the aforementioned fault conditions, the multi-condition electrical feature dataset, and the DC control protection action type; The strategy generation module is used to obtain the failure start type of the AC circuit breaker under each of the aforementioned fault conditions, and combine it with the failure protection action criterion set to construct an adaptive failure protection strategy. The failure protection module is used to control the AC circuit breaker to perform failure protection based on the adaptive failure protection strategy when a fault is detected in the back-to-back flexible DC transmission system in real time.

9. An electronic device, characterized in that, The method includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor, when executing the computer program, implements the AC circuit breaker failure protection method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein when the device containing the computer-readable storage medium executes the computer program, it implements the AC circuit breaker failure protection method as described in any one of claims 1 to 7.

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