Power distribution network self-adaptive reclosing method and system of inverter off-network time sequence

Abstract

The invention belongs to the field of power distribution network time limit of an inverter off-network time sequence, and particularly relates to a power distribution network self-adaptive reclosing method and system of an inverter off-network time sequence, which are used for monitoring the running state of a power distribution network and the inverter off-network time sequence in real time. Determining a fault type according to the running state and a fault judgment principle; the time delay of reclosing is automatically adjusted according to the fault type; the reasonability of time delay is verified, and a feedback mechanism is optimized; by monitoring the operation state of the inverter in real time, potential problems can be found in time, early warning of faults can be achieved, the defect that a traditional method depends on historical data is overcome, the real-time performance and accuracy of system response are ensured, and then the stability and reliability of a power distribution network are improved.

Description

Technical Field

[0001] The present invention belongs to the field of distribution networks for inverter disconnection timing, and particularly relates to a method and system for adaptive reclosing of a distribution network based on inverter disconnection timing. Background Art

[0002] In recent years, with the wide application of distributed power sources, the automatic control function of inverters has been increasingly enhanced. Especially when a grid fault occurs, the inverter can disconnect from the grid (i.e., "disconnect from the network") to protect equipment and ensure the stability of the grid. The regulation of reclosing timing after the inverter disconnects from the grid has become a key issue. Reclosing refers to the process of automatically reclosing the circuit breaker after the grid fault is cleared to restore power supply. With the progress of distribution network technology, reclosing technology has gradually achieved automation and intelligence.

[0003] However, traditional reclosing strategies mostly rely on fixed time delay settings. Although this method can effectively restore the stability of the grid in some cases, it has significant limitations. Specifically, the reclosing strategy with a fixed time delay is difficult to fully consider the characteristics of different types of faults and their recovery times, and it is also unable to respond flexibly to the interaction between the inverter and the grid. As the requirements for the stability and reliability of the distribution network are getting higher and higher, how to automatically adjust the time delay of reclosing according to the different natures of faults has become an important direction for current technological development.

[0004] In addition, although great progress has been made in the real-time monitoring of inverters in the existing technology, most of the solutions rely on traditional threshold-based diagnostic methods for fault type determination. These methods usually ignore the complex interaction effects between the inverter and the grid during the fault occurrence process.

[0005] Therefore, developing a method for adaptive reclosing of a distribution network based on inverter disconnection timing, through precise state monitoring and a dynamic fault judgment model, can greatly improve the accuracy of fault identification and effectively avoid the defects of fixed reclosing delay time in the existing technology. Summary of the Invention

[0006] In view of the problems existing in the above-mentioned prior art, the present invention is proposed.

[0007] To solve the above technical problems, the present invention provides the following technical solutions. A method for adaptive reclosing of a distribution network based on inverter disconnection timing includes: real-time monitoring the operation state of the distribution network and the inverter disconnection timing; determining the fault type according to the operation state and the fault judgment principle; automatically adjusting the time delay of reclosing according to the fault type; verifying the rationality of the time delay and optimizing the feedback mechanism.

[0008] As a preferred solution of the adaptive reclosing method for a distribution network with an inverter disconnection timing according to the present invention, wherein: the real-time monitoring of the operation state of the distribution network includes calculating the current change rate of the distribution network, expressed as, Wherein, is the current change rate, is the current value at time t, is the current value at time t−1, is the time step.

[0009] As a preferred solution of the adaptive reclosing method for a distribution network with an inverter disconnection timing according to the present invention, wherein: the inverter disconnection timing includes that when the grid current change rate is abnormal, the persistence of the fault is confirmed by setting the disconnection timing, and after a delay, the inverter performs a disconnection operation, and the system automatically records the inverter disconnection timing after disconnection.

[0010] As a preferred solution of the adaptive reclosing method for a distribution network with an inverter disconnection timing according to the present invention, wherein: the fault judgment principle includes that when 10% < <30%, the system determines it as a Class I fault. The system combines the inverter disconnection timing to give a recommended reclosing time delay of 300 ms and real-time monitors the recovery process. If the grid current fluctuation returns to normal within 300 ms, the reclosing is automatically executed to restore power supply. If the current fluctuation does not return to normal within 300 ms, the Class II fault reclosing time delay is executed; when 30% < <50%, the system determines it as a Class II fault, and the reclosing time delay is set to 500 ms. If the grid current fluctuation returns to normal within 500 ms, the reclosing is automatically executed to restore power supply. If the current fluctuation does not return to normal within 500 ms, the Class III fault reclosing time delay is executed; when >50%, the system determines it as a Class III fault, and the reclosing time delay is extended to 2 s. If the current fluctuation does not return to normal within 2 s, the reclosing function is controlled to be locked, and the on-site operators are notified to conduct problem troubleshooting.

[0011] As a preferred solution of the adaptive reclosing method for a distribution network with an inverter disconnection timing according to the present invention, wherein: the automatic adjustment of the reclosing time delay according to the fault type includes that if the Class I fault reclosing time delay is set lower than 200 ms, the system prompts that the Class I fault reclosing time delay causes frequent execution of the Class II time delay, increasing the power supply restoration time, and recommends increasing the Class I fault time delay; if the Class II fault time delay is set higher than 600 ms, the system prompts that the reclosing is not performed in time after the fault recovery, resulting in an increase in the line power outage time, and recommends reducing the Class II fault time delay; if the Class III fault time delay is set higher than 3 s, the system prompts that there is a short-circuit risk in the grid and recommends reducing the Class III fault time delay.

[0012] As a preferred solution of the adaptive reclosing method for a distribution network with the inverter disconnection timing according to the present invention, wherein: the verification of the rationality of the time delay includes adjusting the reclosing time delay according to the fault type, monitoring the recovery effect of the power grid after reclosing in real time, and monitoring the rate of change of the power grid current after reclosing in real time to detect whether there are premature and late reclosing situations. When premature reclosing is detected, the system automatically trips and locks the reclosing function, and automatically increases the reclosing time delay; when late reclosing is detected, the system evaluates the operating state. When ≤10%, the reclosing operation is immediately executed, and the reclosing time delay is automatically reduced.

[0013] As a preferred solution of the adaptive reclosing method for a distribution network with the inverter disconnection timing according to the present invention, wherein: the optimization feedback mechanism includes evaluating the restorability of the fault node after reclosing, expressed as , where Sr is the restorability score, is the current value at the kth monitoring point after reclosing, is the rated current value of the power grid, and n is the total number of monitoring points. When <0.1 the power grid returns to normal, and the reclosing time delay is automatically fed back. When ≥0.1 the power grid recovery is abnormal, the reclosing function is automatically locked and an abnormality is fed back, and the reclosing time delay is adjusted.

[0014] As a preferred solution of the adaptive reclosing system for a distribution network with the inverter disconnection timing according to the present invention, wherein: it includes a data acquisition module, a fault judgment module, an automatic adjustment module, and a verification feedback module; The data acquisition module monitors the operating state of the distribution network and the inverter disconnection timing in real time; The fault judgment module determines the fault type according to the operating state and the fault judgment principle; The automatic adjustment module automatically adjusts the time delay of reclosing according to the fault type; The verification feedback module verifies the rationality of the time delay and optimizes the feedback mechanism.

[0015] A computer device includes a memory and a processor. The memory stores a computer program. It is characterized in that when the processor executes the computer program, the steps of any one of the methods of the adaptive reclosing method for a distribution network with the inverter disconnection timing are implemented.

[0016] A computer-readable storage medium has a computer program stored thereon, characterized in that when the computer program is executed by a processor, it implements the steps of any one of the methods in a method for adaptive reclosing of a distribution network according to the off-grid timing of an inverter.

[0017] Advantages of the present invention: By real-time monitoring the operating state of the inverter, potential problems can be detected in a timely manner and faults can be warned, avoiding the deficiency of traditional methods relying on historical data, ensuring the real-time performance and accuracy of system response, and thus improving the stability and reliability of the distribution network.

[0018] Based on the inverter state data collected in real time, an advanced algorithm is used to construct a more complex and accurate fault identification model. This process realizes the intelligent determination of fault types.

[0019] It can flexibly cope with various fault situations, and can also dynamically adjust the reclosing delay time according to the actual restoration needs of the power grid, avoiding the rigid limitation of the fixed delay time in the traditional reclosing strategy.

[0020] Combining the intelligently adjusted reclosing time delay with the real-time monitoring function forms a closed-loop control system. When the fault is accurately diagnosed and the reclosing time delay is determined, the present invention can send a reclosing signal to the circuit breaker through a control instruction to ensure the restoration of power supply at the time when the system returns to stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 It is a schematic flow chart of a method for adaptive reclosing of a distribution network according to the off-grid timing of an inverter provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below with reference to the drawings of the specification. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] Embodiment 1 Refer to Figure 1, which is the first embodiment of the present invention. This embodiment provides a method for adaptive reclosing of a distribution network for the off-grid timing of an inverter, including: S1: Monitor the operating state of the distribution network and the off-grid timing of the inverter in real time.

[0025] Monitoring the operating state of the distribution network in real time includes calculating the rate of change of the distribution network current, expressed as where is the rate of change of current, is the current value at time t, is the current value at time t - 1, is the time step.

[0026] Further, monitor the current changes at each monitoring point (such as substations, distribution lines, inverter outputs, etc.) in the power grid in real time, and judge whether the power grid is in a normal operating state according to the current fluctuations. If the change in current is very drastic, that is, the current changes greatly in a short time, then the rate of change of current is large, usually occurring during load mutations, electrical equipment failures (such as short circuits), or during the inverter regulation process. If the current changes slowly and the rate of change of current is small, it indicates that the system is operating smoothly without obvious emergencies.

[0027] Collect real-time current data at each key position of the distribution network through devices such as sensors. To ensure the timeliness and accuracy of the data, the current data should be collected at a relatively high frequency. Calculate the rate of change of current based on the current value at time t and the current value at time t - 1 collected.

[0028] Even further, the off-grid timing of the inverter includes that when the rate of change of the grid current is abnormal, confirm the persistence of the fault by setting the off-grid timing, and after a delay, the inverter performs an off-grid operation, and the system automatically records the off-grid timing of the inverter after the off-grid.

[0029] When the system detects that the rate of change of the grid current is abnormal, the inverter judges the persistence of the grid fault according to the preset off-grid timing. After a current fluctuation occurs, the inverter does not immediately go off-grid, but executes a delay instruction to observe whether the fault recovers. If the rate of change of current does not return to the normal range during the delay period, the system confirms that the fault persists, and the inverter will continue to perform the off-grid operation; if the rate of change of current returns to normal during the delay period, the system considers that the fault has been eliminated, and the inverter will cancel the off-grid operation and continue to be connected to the grid.

[0030] S2: Determine the type of fault according to the operating state and the fault judgment principle.

[0031] It should be noted that the fault judgment principle includes that when 10% < When it is < 30%, the system determines it as a Class I fault. The system combines the inverter disconnection sequence to give a reclosing time delay recommendation of 300 ms and monitors the recovery process in real time. If the current fluctuation returns to normal within 300 ms, the reclosing is automatically executed to restore power supply. If the current fluctuation does not return to normal within 300 ms, the reclosing time delay for Class II fault is executed; when 30% < < 50%, the system determines it as a Class II fault, and the reclosing time delay is set to 500 ms. If the current fluctuation returns to normal within 500 ms, the reclosing is automatically executed to restore power supply. If the current fluctuation does not return to normal within 500 ms, the reclosing time delay for Class III fault is executed; when > 50%, the system determines it as a Class III fault, and the reclosing time delay is extended to 2 s. If the current fluctuation does not return to normal within 2 s, the reclosing function is controlled to be locked, and the on-site operators are notified to conduct problem troubleshooting.

[0032] Furthermore, through the analysis of the inverter disconnection sequence during the fault occurrence and the analysis of the recovery time for different fault types (such as single-phase grounding, two-phase short circuit, three-phase short circuit), when a Class I fault occurs, the disconnection sequence of the inverter is usually not severely affected, and the 300-ms delay can quickly complete the reclosing operation at the initial stage of current recovery without interfering with the inverter reconnecting sequence; when a Class II fault occurs, the inverter usually conducts self-check and waits for the grid to stably recover at this stage. 500 ms can provide enough time for the inverter to complete self-check and get ready to reconnect; when a Class III fault occurs, the 2-s delay can protect the grid equipment from instantaneous overcurrent caused by premature reclosing, and if the current fluctuation does not return to normal after 2 s of fault duration, the system will automatically lock the reclosing function, and the reclosing operation at this time is more secure and will not pose unnecessary risks to the grid.

[0033] Even further, when the change rate of current fluctuation for a Class I fault is between 10% and 30%, it indicates that the grid has a minor fault (such as instantaneous overload or short-term voltage instability). This situation is usually temporary and has a high possibility of recovery. The system calculates the change rate of current to determine the fault type. When the system determines the fault type as a Class I fault, it combines the historical data of the inverter disconnection sequence and recommends setting the reclosing delay to 300 ms. This period is sufficient for the grid fluctuation to return to normal, and the system will continuously monitor the current and voltage fluctuations; if the current returns to the normal range within 300 ms, the reclosing is automatically executed to restore power supply; if the current does not recover, it will enter the next-level fault (Class II fault) for processing.

[0034] Level II faults indicate that there are significant fluctuations in the power grid, which may be caused by large load changes, equipment failures, or local short circuits in the power grid. At this time, the amplitude of the current fluctuation is large, and the difficulty of recovery increases. Although the possibility of power grid recovery still exists, it takes more time to verify whether it can return to the normal state. Therefore, Level II faults require a longer time delay to ensure the accuracy of the recovery operation. If the current returns to normal within 500 ms, the system will automatically perform reclosing to restore power supply. If the current does not return to normal within 500 ms, the system will enter the Level III fault state, continue to extend the reclosing time delay, and perform further processing.

[0035] Level III faults indicate that a serious fault has occurred in the power grid, usually caused by large-scale short circuits, overloads, or serious equipment failures. Such faults usually cause large-scale current fluctuations in the power grid, and it may take a long time to return to the normal state, or fault troubleshooting is required before recovery. Therefore, the handling of Level III faults requires the system to have stronger adaptability and delay time to ensure power grid stability. The reclosing time delay for Level III faults is set to 2 s. This delay time is much higher than that of Level I and Level II faults, giving the system more time to evaluate whether the fault can be recovered. If the current fluctuation does not return to normal within 2 s, the control locks the reclosing function, notifies the on-site operators to conduct problem troubleshooting, and at the same time avoids unnecessary recovery operations by the system due to misjudgment.

[0036] S3: Automatically adjust the reclosing time delay according to the fault type.

[0037] It should be noted that automatically adjusting the reclosing time delay according to the fault type includes: if the reclosing time delay for Level I faults is set lower than 200 ms, the system will prompt that the reclosing time delay for Level I faults causes frequent execution of the Level II time delay, increasing the power supply restoration time, and it is recommended to increase the Level I fault time delay; if the Level II fault time delay is set higher than 600 ms, the system will prompt that the reclosing is not timely after the fault recovery, resulting in an increase in the line power outage time, and it is recommended to lower the Level II fault time delay; if the Level III fault time delay is set higher than 3 s, the system will prompt that there is a short circuit risk in the power grid, and it is recommended to lower the Level III fault time delay.

[0038] Furthermore, if the reclosing time delay is too short, the system may repeatedly attempt the reclosing operation for level I faults before the power grid recovers. This situation will force the reclosing delay to be extended to 500 ms (the time delay for level II faults), thus increasing the power supply restoration time and the burden on the system. An overly low time delay will cause the system to judge that the power grid recovery is insufficient, resulting in unnecessary delays and a longer actual recovery time, affecting the efficiency of the power grid. When the reclosing time delay for level I faults is less than 200 ms, the system will prompt: The reclosing time delay for level I faults is too short, which may lead to frequent entry into the level II fault delay mode and increase the power supply restoration time. It is recommended to increase the reclosing time delay for level I faults.

[0039] If the time delay for level II faults exceeds 600 ms, the reclosing operation may be delayed until after the power grid has recovered, resulting in an overly long power grid outage time. Especially, an overly long time delay after power supply restoration will miss the opportunity when the power grid has recovered, leading to a reduction in the overall power supply restoration efficiency. The system should reclose as soon as possible to avoid continuous power outages. When the reclosing time delay for level II faults exceeds 600 ms, the system will prompt: The reclosing time delay for level II faults is too long, resulting in failure to reclose in time after power supply restoration and increasing the line outage time. It is recommended to decrease the reclosing time delay for level II faults.

[0040] Level III faults indicate that a severe fault has occurred in the power grid, usually caused by large-scale short circuits, equipment failures, or other major problems, with a current change rate exceeding 50%. The recovery process for this type of fault is complex and time-consuming. The system sets the reclosing time delay to 2 s to ensure sufficient recovery time. If the reclosing time delay is set higher than 3 s, the true faults in the power grid cannot be identified in time, resulting in the power grid being in an unstable state for a long time, increasing the risk of power grid short circuits. An overly long delay may fail to timely judge whether the power grid is in a fault state or fail to lock the reclosing function in time, leading to further damage to the system. When the reclosing time delay for level III faults exceeds 3 s, the system will prompt: The reclosing time delay for level III faults is too long, which may lead to an increase in the risk of power grid short circuits. It is recommended to decrease the reclosing time delay for level III faults.

[0041] S4: Verify the reasonableness of the time delay and optimize the feedback mechanism.

[0042] It should be noted that verifying the reasonableness of the time delay includes adjusting the reclosing time delay according to the fault type, monitoring the recovery effect of the power grid after reclosing in real time, and monitoring the current change rate of the power grid after reclosing in real time to detect whether there are cases of premature and late reclosing. When premature reclosing is detected, the system automatically trips and locks the reclosing function, and automatically increases the reclosing time delay; when late reclosing is detected, the system evaluates the operating state. When ≤10%, immediately perform the reclosing operation and automatically decrease the reclosing time delay.

[0043] When the system determines a certain type of fault and sets the corresponding reclosing time delay, the system will automatically perform the reclosing operation and monitor the recovery effect of the power grid in real time. First, it is necessary to check the recovery of current and voltage fluctuations and evaluate whether the power grid has returned to a stable state after reclosing. By continuously monitoring the rate of change of the current in the power grid, it is judged whether it has returned to a safe operating state. Premature reclosing refers to attempting to perform the reclosing operation before the power grid has fully recovered. The current or voltage fluctuations in the power grid may not have been completely eliminated. Premature reclosing will cause the power grid recovery to be unstable and may cause equipment such as transformers and circuit breakers to be impacted. Because these devices may be subject to uneven load impacts when the current has not returned to the normal level, and may even burn out or be damaged. By observing the process of power grid recovery, the system can judge whether the reclosing timing is premature. When the system detects premature reclosing, it will automatically trip and lock the reclosing function, and notify the on-site operators to conduct problem troubleshooting; Late reclosing means that after the fault has been cleared, the reclosing operation is delayed, resulting in an overly long power grid recovery time. Late reclosing will extend the power grid recovery time, cause power outages, affect the power consumption needs of users, and may even cause the system to be overloaded. An overly long power grid recovery time will cause continuous power outages, affect the reliability of power supply, cause unstable power consumption of users, lead to uneven power grid loads, and cause excessive current changes. When the system detects late reclosing, it will detect the rate of change of the power grid current. When the rate of change of the current is stable, the system will immediately perform the reclosing action and give suggestions to reduce the reclosing time delay.

[0044] Furthermore, the optimized feedback mechanism includes evaluating the restorability of the fault node after reclosing, expressed as , where Sr is the restorability score, is the current value at the kth monitoring point after reclosing, is the rated current value of the power grid, and n is the total number of monitoring points. When <0.1 , the power grid returns to normal, and the reclosing time delay is automatically fed back. When ≥0.1 , the power grid recovery is abnormal, the reclosing function is automatically locked and an abnormality is fed back, and the reclosing time delay is adjusted.

[0045] After each reclosing operation is performed, the system will evaluate the restorability of the fault node. When <0.1 , it is determined that the fault node has returned to normal. At this time, the feedback mechanism automatically feeds back the repair result and records the inverter disconnection timing and the reclosing time delay, providing a basis for the system to automatically adjust the reclosing time delay; When ≥0.1 When it is ≥0.1, it is determined that the repair is abnormal. After reporting the abnormality, the reclosing system is automatically locked. The system will re-evaluate whether the reclosing operation is appropriate according to the fault judgment principle and automatically adjust the time delay according to the actual recovery situation.

[0046] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

[0047] Embodiment 2 The second embodiment of the present invention is different from the previous embodiment in that: If the said function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the essence of the technical solution of the present invention, or the part that contributes to the prior art, or part of the technical solution can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs that can store program codes.

[0048] The logic and / or steps described in other ways herein, for example, can be considered as a definite sequence list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device), or used in combination with these instruction execution systems, apparatus, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device.

[0049] More specific examples (nonexhaustive list) of computer-readable media include the following: electrical connections (electronic devices) having one or more wirings, portable computer disk cartridges (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber devices, and portable compact disc read-only memory (CDROM). Additionally, the computer-readable media can even be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpretation, or otherwise processing as appropriate, and then stored in a computer memory.

[0050] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or combinations thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application-specific integrated circuits having suitable combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

[0051] Embodiment 3 This is the third embodiment of the present invention, which provides a distribution network adaptive reclosing system for the inverter disconnection timing, characterized by comprising a data acquisition module, a fault judgment module, an automatic adjustment module, and a verification feedback module; The data acquisition module monitors the operation state of the distribution network and the inverter disconnection timing in real time; The fault judgment module determines the fault type according to the operation state and the fault judgment principle; The automatic adjustment module automatically adjusts the time delay of the reclosing according to the fault type; The verification feedback module verifies the reasonableness of the time delay and optimizes the feedback mechanism.

[0052] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

[0053] Embodiment 4 provides a method for adaptive reclosing of a distribution network for the off-grid timing of an inverter. To verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0054] In this embodiment, by simulating the current change rate of the distribution network under fault conditions, a technical solution for real-time monitoring, fault judgment, and automatic adjustment of reclosing delay based on the current change rate is verified. The experiment simulates several typical fault scenarios in the distribution network, including single-phase ground short circuit, two-phase short circuit, and system load fluctuation, etc. All experiments are based on the current change rate to identify the fault type, and the reclosing delay is adjusted according to the characteristics of the current fluctuation, in order to improve the recovery speed and system stability of the distribution network.

[0055] The test object includes a typical distribution network system, and the model contains 5 distribution lines and 5 inverters. Each inverter has the ability to monitor the current change rate in real time. The experiment judges the fault type of the distribution network by collecting the current change rate data of the inverter in real time and combining specific fault determination rules. Then, the system automatically adjusts the reclosing delay according to the fault type, and the reclosing delay setting is determined by the magnitude and change trend of the current change rate.

[0056] The test process is as follows: 1. Real-time monitoring of the current change rate: In the experiment, each inverter will record and report the current data in real time. By calculating the change rate of the current, the system can monitor the amplitude and speed of the current fluctuation.

[0057] 2. Fault determination: According to the characteristics of the current change rate, the system can automatically identify different fault types. For example, if the change rate of the current is greater than a certain threshold, it is determined as a short circuit fault; if the change rate of the current is less than a certain set threshold, it is determined as a load fluctuation.

[0058] 3. Automatic adjustment of the reclosing delay: The system adjusts the reclosing delay according to the fault type and the current change rate. For example, if the current change rate changes rapidly, it may be a short circuit fault, and the reclosing delay is set to a shorter time; while if the current change rate changes slowly, a longer reclosing delay can be set to ensure the system recovery.

[0059] 4. Rationality verification and optimization feedback mechanism: The system will continuously verify whether each reclosing delay is reasonable. If a certain reclosing operation fails to restore the system, the system will automatically feedback and adjust the delay parameter to ensure the efficiency of subsequent operations.

[0060] This embodiment improves the recovery speed of the system after a fault, reduces the system downtime, and increases the fault recovery ability of the system by optimizing the reclosing delay. The experimental data is shown in Table 1.

[0061] Table 1 Simulation experiment data , It can be seen from the experimental data that the proposed method can intelligently adjust the time delay of reclosing according to the current change rate of different types of faults and optimize the restoration operation. In the case of three-phase short circuit, a lower current change rate (10%-30%) can restore power supply with a delay of 300 ms.

[0062] For single-phase grounding faults, the system can intelligently identify the fault type and automatically adjust the delay time according to the different current change rates to ensure power supply restoration within 500 ms. When the current change rate is greater than 50%, the system adjusts the delay time through a feedback mechanism, significantly improving the restoration effect and avoiding fault recurrence caused by too short a delay.

[0063] Generally speaking, the proposed method effectively avoids the problems caused by too long or too short manually set delay time in traditional methods through the adaptive adjustment of the current change rate and fault type, ensuring the stability during the power grid restoration process and the safety of equipment, thus significantly improving the operation efficiency and reliability of the distribution network.

Claims

1. A distribution network adaptive reclosing method for inverter off-grid timing, characterized by: include: Real-time monitoring of the distribution network operation status and inverter off-grid timing; Determine the fault type based on the operating status and fault judgment principles; Automatically adjust the reclosing time delay according to the fault type; Verify the rationality of time delay and optimize the feedback mechanism.

2. A distribution network adaptive reclosing method for inverter off-grid timing as claimed in claim 1, characterized in that: The real-time monitoring of the distribution network operation status includes calculating the distribution network current change rate expressed as: in, is the current change rate, is the current value at time t, is the current value at time t−1, is the time step.

3. A distribution network adaptive reclosing method for inverter off-grid timing as claimed in claim 2, characterized in that: The inverter off-grid timing includes: when the grid current change rate is abnormal, the continuity of the fault is confirmed by setting the off-grid timing, the inverter performs off-grid action after a delay, and the system automatically records the inverter off-grid timing after off-grid.

4. A distribution network adaptive reclosing method for inverter off-grid timing as claimed in claim 3, characterized in that: The fault judgment principle includes: when 10%< <30%, the system determines it as a Level I fault. The system recommends a reclosing time delay of 300ms based on the inverter off-grid timing, and monitors the recovery process in real time. If the current fluctuation of the power grid returns to normal within 300ms, the reclosing will be automatically executed to restore power supply. If the current fluctuation does not return to normal within 300ms, the Level II fault reclosing time delay will be executed. When 30%< When the current fluctuation of the power grid returns to normal within 500ms, the reclosing time delay will be set to 500ms. If the current fluctuation of the power grid returns to normal within 500ms, the reclosing time delay of the level III fault will be automatically executed to restore the power supply. If the current fluctuation does not return to normal within 500ms, the reclosing time delay of the level III fault will be executed. When the current fluctuation is >50%, the system determines it as a Level III fault and the reclosing time is delayed to 2s. If the current fluctuation does not return to normal within 2s, the control locks the reclosing function and notifies the on-site operating personnel to troubleshoot the problem.

5. A distribution network adaptive reclosing method for inverter off-grid timing as claimed in claim 4, characterized in that: The automatic adjustment of the reclosing time delay according to the fault type includes: if the reclosing time delay of the level I fault is set to less than 200ms, the system prompts that the reclosing time delay of the level I fault leads to frequent execution of the level II time delay, which increases the power supply restoration time, and it is recommended to increase the level I fault time delay; If the Level II fault time delay is set higher than 600ms, the system will prompt that the circuit breaker is not reclosed in time after the fault is restored, resulting in increased line outage time. It is recommended to lower the Level II fault time delay; If the Level III fault time delay is set higher than 3s, the system will prompt that there is a short circuit risk in the power grid and it is recommended to lower the Level III fault time delay.

6. A distribution network adaptive reclosing method for inverter off-grid timing as claimed in claim 5, characterized in that: The rationality of the verification time delay includes adjusting the reclosing time delay according to the fault type, monitoring and observing the recovery effect of the power grid after reclosing in real time, and monitoring the rate of change of the power grid current after reclosing in real time, detecting whether there is premature or late reclosing. When premature reclosing is detected, the system automatically trips and locks the reclosing function, and automatically increases the reclosing time delay; when late reclosing is detected, the system evaluates the operating status. When the value is less than or equal to 10%, the reclosing action is executed immediately and the reclosing time delay is automatically reduced.

7. A distribution network adaptive reclosing method for inverter off-grid timing as claimed in claim 6, characterized in that: The optimization feedback mechanism includes evaluating the recoverability of the fault node after reclosing, which is expressed as: ， Among them, Sr is the recovery score, is the current value of the kth monitoring point after reclosing, is the rated current value of the power grid, n is the total number of monitoring points, when <0.1 When the power grid returns to normal, the reclosing time delay is automatically fed back. ≥0.1 When the power grid recovers abnormally, the reclosing function is automatically locked and the abnormality is fed back, and the reclosing time delay is adjusted.

8. A distribution network adaptive reclosing system for inverter off-grid timing, using a distribution network adaptive reclosing method for inverter off-grid timing as described in any one of claims 1 to 7, characterized in that: Including data collection module, fault judgment module, automatic adjustment module, and verification feedback module; The data collection module monitors the operation status of the distribution network and the timing of inverter disconnection in real time; The fault judgment module determines the fault type according to the operating state and the fault judgment principle; The automatic adjustment module automatically adjusts the time delay of the reclosing switch according to the fault type; The verification feedback module verifies the rationality of the time delay and optimizes the feedback mechanism.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

Images