A method and system for anti-islanding protection combining active and passive methods

Abstract

A kind of active-passive combined islanding protection method and system, passive islanding protection uses voltage criterion, when voltage is in abnormal value, islanding protection is respectively acted by short delay and long delay, wherein short delay is set according to the time of one level larger than the current time of main branch of distribution network, short delay islanding starts independent reclosing, reclosing is checked by voltage delay closing, long delay period islanding blocks reclosing;Active islanding protection starts islanding protection in the way of remote / local transmission, active islanding protection starts independent reclosing, reclosing is checked by voltage delay closing.The present application solves the problem that traditional islanding protection action delay is long, leading to that upper switch cannot be automatically reclosed, and backup power supply cannot be closed;At the same time, it solves the problem that islanding protection misoperation leads to large-scale new energy off-grid during system disturbance.

Description

Technical Field

[0001] This invention belongs to the field of power system relay protection technology, and relates to distribution network anti-islanding protection technology and system, and particularly to an active-passive combined anti-islanding protection method and system. Background Technology

[0002] Against the backdrop of continuously rising global energy demand and increasingly severe climate change, countries are vigorously developing new energy technologies. However, the instability of new energy output can affect the safe and reliable operation of equipment, especially unplanned isolated operation of new energy sources, which may not only damage high-precision electrical equipment but also endanger the personal safety of personnel.

[0003] Currently, typical anti-islanding protection is mainly divided into passive anti-islanding protection and active anti-islanding protection. Passive anti-islanding protection is based on local electrical quantities and mainly includes voltage protection, frequency protection, and vector offset protection. These methods utilize the imbalance between the active and reactive power output of distributed power sources and the load power when the distribution network is in islanded operation, which causes voltage drops or rises, frequency changes, and voltage phase shifts before and after islanding. Active anti-islanding protection mainly includes the injection signal method and the inverter active disturbance method. The injection signal is a signal different from the power frequency and harmonics injected at the grid connection point. The change in the system's measured impedance under this signal is detected to determine whether the outgoing line is in islanded operation. The working principle of the inverter active disturbance protection method is that the inverter actively adjusts its output voltage amplitude and frequency. When islanding occurs, even when the output power and load power are balanced, the island balance will be disrupted, causing significant changes in island voltage and frequency, causing the voltage and frequency protection to activate.

[0004] In summary, current anti-islanding protection mainly relies on voltage and frequency to determine whether islanding has occurred. This method lacks selectivity and can only activate anti-islanding protection after reliable isolation of the fault outside the zone by increasing the delay. The activation time of anti-islanding protection is generally between 2 and 50 seconds. This also means that the "no voltage detection" condition for reclosing and backup switching cannot be met, affecting power restoration. In addition, when the distributed voltage and load are exactly balanced, forming an unplanned island, anti-islanding protection based on voltage and frequency will fail to operate. At this time, the personal safety of maintenance personnel will be threatened when repairing distribution network equipment. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention proposes a combined active-passive anti-islanding protection method and system. It utilizes voltage to determine anti-islanding operation, triggering a short-delay anti-islanding protection trip to resolve issues related to reclosing and backup power supply failures due to renewable energy sources. Simultaneously, it employs short-delay rapid anti-islanding action and remote / local reclosing initiation to address the problems of large-scale grid disconnection of renewable energy sources due to anti-islanding protection malfunctions and the threat to maintenance personnel's safety caused by unplanned islanding operations.

[0006] The present invention specifically adopts the following technical solution: In a first aspect, the present invention discloses an active-passive combined anti-islanding protection method, comprising: Step 1: Cyclicly collect the positive sequence voltage and zero sequence voltage at the installation points of the protection devices of each branch of the distribution network connected to the microgrid at the first time interval; Step 2: When the positive sequence voltage change at any protection device installation location in Step 1 meets the start-up condition or the zero sequence voltage meets the start-up condition, the protection is activated and proceeds to Step 3; otherwise, return to Step 1. Step 3: Collect the positive sequence voltage at the installation location of the protection device for the branch connected to the microgrid and the distributed power source branch of the microgrid at the second time interval. If the positive sequence voltage is not within the preset operating voltage range, proceed to step 4; otherwise, proceed to step 5. Step 4: The anti-islanding protection will activate if the conditions in Step 3 are met continuously until the first delay (short delay setting) is reached. After the anti-islanding protection activates, or after remote / local anti-islanding operation, if the positive sequence voltage at the installation location of the anti-islanding protection or anti-islanding operation branch protection device returns to the preset voltage range and continues to reach the third delay (reclosing delay setting), the anti-islanding protection will activate reclosing. Step 5: If the conditions in Step 3 are met continuously and the second delay (i.e., the long delay setting) is reached, the anti-islanding protection will activate and the reclosing circuit will be blocked.

[0007] More preferably, In step 1, the first time interval is 40ms; each protection installation location includes: the distribution network branch connected to the microgrid, other branches on the same busbar as the distribution network branch, and the protection installation locations of each section of the upper part of the distribution network branch.

[0008] More preferably, In step 2, the positive sequence voltage surge meets the following activation conditions: a first activation condition and a second activation condition. The protection system activates when either activation condition is met. The first startup condition is , The second startup condition is , in, The maximum value among the half-wave integrals of the effective values ​​of the three phase voltages. The maximum value among the half-wave integrals of the effective values ​​of the three phase-to-phase voltages. It is an adjustable positive-sequence voltage mutation threshold for startup.

[0009] More preferably, Value range: 0.01 U N ~0.5 U N ,in, U N To protect the rated voltage of the corresponding branch at the installation location.

[0010] In step 2, the positive sequence voltage surge meets the following activation conditions: a first activation condition and a second activation condition. The protection system activates when either activation condition is met. The first startup condition is , The second startup condition is , in, The maximum value among the half-wave integrals of the effective values ​​of the three phase voltages. The maximum value among the half-wave integrals of the effective values ​​of the three phase-to-phase voltages. It is an adjustable positive-sequence voltage mutation threshold for startup.

[0011] More preferably, Value range: 0.01 U N ~0.5 U N ,in, U N To protect the rated voltage of the corresponding branch at the installation location.

[0012] More preferably, In step 3, the second time interval is 20ms; the preset voltage range is: 0.85 U N < U 1<1.1 U N in, This is the positive sequence voltage value. To protect the system's rated voltage at the installation location.

[0013] More preferably, In step 4, the first delay, i.e. the short delay setting, is set according to the time difference of the main branch current I segment of the distribution network. An additional time difference is added to the time difference of the main branch, and each time difference is generally taken as 0.2S.

[0014] More preferably, In step 4, the third delay is the coincidence delay setpoint. Calculate using the following formula:

[0015] in U 1 represents the positive sequence voltage acquired at the second time interval. T 0_set For fixed delay, U 1_set For the positive sequence voltage setting, take... U 1_set =0.85 U N , T set Let the floating delay be a fixed value, where, To protect the system's rated voltage at the installation location.

[0016] More preferably, T 0_set The value range is 0.1~0.5S; T set The value range is 20~80S; U 1_set The value is 0.85 U N , U N To protect the rated voltage of the corresponding branch at the installation location.

[0017] More preferably, In step 5, the second delay, i.e. the long delay, is set according to the reclosing time of the reclosing function switch configured at the upper level of the anti-islanding protection installation location and the automatic transfer time of the sectionalizing switch, with a time difference of more than 0.5 seconds added to the longest time of the two.

[0018] Secondly, the present invention discloses an active-passive combined anti-islanding protection system based on the aforementioned method, including a data acquisition module, a protection start module, a short-delay anti-islanding protection and reclosing module, and a long-delay anti-islanding protection and blocking reclosing module; The data acquisition module is used to cyclically acquire the positive sequence voltage and zero sequence voltage at the installation locations of the protection devices of each branch of the distribution network connected to the microgrid at a first time interval; after the protection is started, it is used to acquire the positive sequence voltage at the installation locations of the protection devices of the branches connected to the microgrid and the distributed power supply branches of the microgrid at a second time interval. The protection start-up module is equipped with a voltage surge start-up element and a zero-sequence voltage start-up element. When the collected positive-sequence voltage surge or zero-sequence voltage meets the corresponding start-up conditions, the protection is activated. The short-delay anti-islanding protection and reclosing module will activate the anti-islanding protection when the positive sequence voltage is determined to be outside the preset operating voltage range for a continuous period of time. After the anti-islanding protection is activated, or after remote / local anti-islanding operation, if the positive sequence voltage returns to the preset voltage range, the reclosing operation will be performed after the reclosing delay setting. The long-delay anti-islanding protection and reclosing blocking module will activate the anti-islanding protection and block the reclosing when it is determined that the positive sequence voltage is outside the preset operating voltage range for a continuous long delay period.

[0019] Thirdly, the present invention discloses a computer device, including a memory, a processor, and a computer program stored in the memory; the processor executes the computer program to implement the steps of the aforementioned active-passive combined anti-islanding protection method.

[0020] Fourthly, the present invention discloses a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the aforementioned active-passive combined anti-islanding protection method.

[0021] Compared with the prior art, the present invention has the following significant advantages: This invention combines active and passive anti-islanding protection, and integrates anti-islanding protection with reclosing based on fault positive sequence voltage delay. This achieves sensitive and fast passive anti-islanding protection in coordination with distribution network main branch switch reclosing and sectional backup automatic transfer. At the same time, the active anti-islanding method based on remote / local uninterrupted power transmission solves the problem of anti-islanding protection being unable to disconnect distributed power sources during unplanned islanding operation, which threatens the personal safety of maintenance personnel. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the active-passive combined anti-islanding protection method of the present invention; Figure 2 This is a typical application scenario diagram of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0024] like Figure 1 As shown, this invention discloses a combined active-passive anti-islanding protection method, comprising the following steps: Step 1: Cyclicly collect the positive sequence voltage and zero sequence voltage at the installation points of the protection devices of each branch of the distribution network connected to the microgrid at the first time interval; The first time interval is 40ms. Each protection installation location includes: the distribution network branch connected to the microgrid, other branches on the same busbar as that distribution network branch, and the protection installation locations of each section of the upper part of that distribution network branch. Before protection activation, record the positive sequence voltage and zero sequence voltage at each protection installation location.

[0025] Step 2: When the positive sequence voltage change meets the operating conditions of the voltage change start-up element or the zero sequence voltage meets the zero sequence voltage start-up conditions, the protection starts and proceeds to Step 3; otherwise, return to Step 1. In step 2, the activation conditions for the positive sequence voltage surge initiation element include a first activation condition and a second activation condition. The protection is activated when either activation condition is met. The first action condition is , The second action condition is , in, The maximum value among the half-wave integrals of the effective values ​​of the three phase voltages. The maximum value among the half-wave integrals of the effective values ​​of the three phase-to-phase voltages. It is a fixed threshold that can be adjusted. Value range: 0.01 U N ~0.5 U N In this case U N Considering 10kV, , All are taken as 300V.

[0026] Step 3: Collect the positive sequence voltage at the installation location of the protection device for the branch connected to the microgrid and the distributed power source branch of the microgrid at the second time interval. If the positive sequence voltage is not within the preset operating voltage range, proceed to step 4; otherwise, proceed to step 5. The second time interval is 20ms. The preset voltage range is: 0.85 U N < U 1<1.1 U N in, This is the positive sequence voltage value. To protect the system's rated voltage at the installation location.

[0027] Step 4: The anti-islanding protection will activate if the conditions in Step 3 are met continuously until the first delay (short delay setting) is reached. After the anti-islanding protection activates, or after remote / local anti-islanding operation, if the positive sequence voltage at the installation location of the anti-islanding protection or anti-islanding operation branch protection device returns to the preset voltage range and continues to reach the third delay (reclosing delay setting), the anti-islanding protection will activate reclosing. In step 4, the protection based on positive sequence voltage is passive anti-islanding protection, while the protection based on remote / local transmission is active anti-islanding protection. Remote transmission can trigger the anti-islanding protection action through the background via the longitudinal communication remote control device, or it can be triggered on the device's LCD screen.

[0028] The anti-islanding short-delay setting is based on the time difference of the main and branch line currents in the distribution network. An additional time difference is added to the main and branch line time difference, with each time difference typically set to 0.2 seconds. Figure 2 Taking the distribution network as an example, the main branch containing distributed power supply has only one primary switch 5DL. If the overcurrent protection time of switch 5DL is 0.2S, the anti-islanding protection time of switch 6DL is 0.4S, and the anti-islanding protection time of switch 7DL is 0.6S; The third delay is the overlap delay setpoint. Calculate using the following formula:

[0029] in U 1 represents the positive sequence voltage acquired at the second time interval. T 0_set For fixed delay, U 1_set For the positive sequence voltage setting, take... U 1_set =0.85 U N , T set This is a floating delay setpoint. In this case, T... 0_set The fixed delay is set to 0.1s to match the low-voltage characteristics of the photovoltaic system, and the floating delay is set to T. set =40S. Step 5: If the conditions in step 3 are met continuously and the second delay value (i.e., the long delay setting) is reached, the anti-islanding protection will activate and the reclosing circuit will be blocked.

[0030] The anti-islanding long delay is set according to the reclosing time of the reclosing function switch configured at the upstream location of the anti-islanding protection installation and the automatic transfer time of the sectionalizing switch, with a time difference of more than 0.5 seconds added to the maximum time of both. Figure 2 For the distribution network structure, the main and branch circuit switches 5DL have a reclosing time of 5S, a standby time of 10S, and an anti-islanding long delay setting of 11S. This invention discloses an active-passive combined anti-islanding protection system based on the aforementioned method, including a data acquisition module, a protection start module, a short-delay anti-islanding protection and reclosing module, and a long-delay anti-islanding protection and blocking reclosing module; The data acquisition module is used to cyclically acquire the positive sequence voltage and zero sequence voltage at the installation locations of the protection devices of each branch of the distribution network connected to the microgrid at a first time interval; after the protection is started, it is used to acquire the positive sequence voltage at the installation locations of the protection devices of the branches connected to the microgrid and the distributed power supply branches of the microgrid at a second time interval. The protection start-up module is equipped with a voltage surge start-up element and a zero-sequence voltage start-up element. When the collected positive-sequence voltage surge or zero-sequence voltage meets the corresponding start-up condition, the protection is activated. The short-delay anti-islanding protection and reclosing module will activate the anti-islanding protection when the positive sequence voltage is determined to be outside the preset operating voltage range for a continuous period of time. After the anti-islanding protection is activated, or after remote / local anti-islanding operation, if the positive sequence voltage returns to the preset voltage range, the reclosing operation will be performed after the reclosing delay setting. The long-delay anti-islanding protection and reclosing blocking module will activate the anti-islanding protection and block the reclosing when it is determined that the positive sequence voltage is outside the preset operating voltage range for a continuous long delay period.

[0031] Example 1: Figure 2 When a transient phase-to-phase fault occurs at k2, the positive sequence voltage at the protection installation point is collected cyclically at the first time interval to meet the operating conditions of the voltage surge initiation element, the protection is activated, and the 5DL switch trips in 0.2 seconds. The positive sequence voltage after a fault at the protection installation location is collected at the second time interval. Because the main branch switch is open, the power supply and load of its downstream lines are disconnected from the main system. The distributed power supply cannot maintain source-load balance, and the positive sequence voltage is no longer between 0.85 and 1.1 times the rated voltage. U N Within the specified range, the anti-islanding protection of switches 6DL and 7DL activated at 0.4S and 0.6S respectively. After 5S, switch 5DL reclosed. Switches 6DL and 7DL detected a voltage between 0.85 and 1.1 times the rated voltage U. N Within this range, after this state lasts for 0.1 seconds, switches 6DL and 7DL will reclose.

[0032] Example 2: Figure 2 When a permanent phase-to-phase fault occurs at k2, the positive sequence voltage at the protection installation point is collected cyclically at the first time interval to meet the operating conditions of the voltage surge initiation element, the protection is activated, and the 5DL switch trips in 0.2 seconds. The positive sequence voltage after a fault at the protection installation location is collected at the second time interval. Because the main branch switch is open, the power supply and load of its downstream lines are disconnected from the main system. The distributed power supply cannot maintain source-load balance, and the positive sequence voltage is no longer between 0.85 and 1.1 times the rated voltage. U N Within the specified range, the anti-islanding protection of switches 6DL and 7DL activated at 0.4S and 0.6S respectively. After 5S, switch 5DL reclosed and accelerated its operation. Switches 6DL and 7DL detected that the positive sequence voltage was not between 0.85 and 1.1 times the rated voltage. U N Within the range, the reclosing circuit could not operate until the long-delay anti-islanding protection activated 11 seconds after the fault, and the reclosing discharge of switches 6DL and 7DL was initiated.

[0033] Example 3: Figure 2 A transient phase-to-phase fault occurs at k1, causing the 1DL and 2DL switches to trip instantaneously. The positive sequence voltage at the protection installation point is collected cyclically at the first time interval to meet the operating conditions of the voltage surge triggering element, thus activating the protection. After the fault, the positive sequence voltage at the protection installation point is collected at the second time interval. Due to the disconnection of the main branch switch, the downstream power supply and load are disconnected from the main system, and the distributed power supply cannot maintain source-load balance. Therefore, the positive sequence voltage is no longer between 0.85 and 1.1 times the rated voltage. U N Within the specified range, the anti-islanding protection of switches 6DL and 7DL activated at 0.4S and 0.6S respectively. Switches 1DL and 2DL reclosed after 1S, and switches 6DL and 7DL detected that the voltage had recovered to 0.85~1.1 times the rated voltage. U N Within this range, after this state lasts for 0.1 seconds, switches 6DL and 7DL will reclose.

[0034] Example 4: Figure 2 A permanent phase-to-phase fault occurs at k1, causing instantaneous tripping of switches 1DL and 2DL. The positive sequence voltage at the protection installation point is collected cyclically at the first time interval to meet the operating conditions of the voltage surge initiation element, thus activating the protection. After the fault, the positive sequence voltage at the protection installation point is collected at the second time interval. Due to the disconnection of the main branch switch, the downstream power supply and load are disconnected from the main system, and the distributed power supply cannot maintain source-load balance. Therefore, the positive sequence voltage is no longer between 0.85 and 1.1 times the rated voltage. U N Within the specified range, the anti-islanding protection of switches 6DL and 7DL activated within 0.4 seconds and 0.6 seconds, respectively. Switches 6DL and 7DL detected that the positive sequence voltage was not between 0.85 and 1.1 times the rated voltage. U NWithin the specified range, the reclosing switch failed to operate until the automatic transfer switch activated, restoring the 10kV bus voltage to its rated voltage. U N Switches 6DL and 7DL automatically overlap.

[0035] Example 5: Figure 2 A permanent phase-to-phase fault occurred at k1, causing instantaneous tripping of switches 1DL and 2DL. The positive sequence voltage at the protection installation point was cyclically collected at the first time interval to meet the operating conditions of the voltage surge initiation element, thus activating the protection. The 10kV busbar, including the distributed power supply section, formed an unplanned island, with the positive sequence voltage ranging from 0.85 to 1.1 times the rated voltage. U N Within this range, the passive anti-islanding protection of switches 6DL and 7DL, based on voltage, fails to operate. At this time, the automatic transfer switch does not meet the no-voltage detection condition and cannot close. This leads to unplanned islanding operation for an extended period. When maintaining this 10kV distribution network equipment, the 7DL switch is first remotely controlled. After the anti-islanding protection of switch 7DL trips, the downstream distributed power supply of the 10kV busbar cannot maintain source-load balance, and the positive sequence voltage is no longer between 0.85 and 1.1 times the rated voltage. U N Within the specified range, the detection voltage does not meet the reclosing conditions until the reclosing discharges, thus enabling the 10kV distribution network equipment to be maintained without being energized.

[0036] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0037] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0038] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0039] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A combined active-passive anti-islanding protection method, characterized in that, The protection method includes: Step 1: Cyclicly collect the positive sequence voltage and zero sequence voltage at the installation points of the protection devices of each branch of the distribution network connected to the microgrid at the first time interval; Step 2: When the positive sequence voltage change at any protection device installation location in Step 1 meets the start-up condition or the zero sequence voltage meets the start-up condition, the protection is activated and proceeds to Step 3; otherwise, return to Step 1. Step 3: Collect the positive sequence voltage at the installation location of the protection device for the branch connected to the microgrid and the distributed power source branch of the microgrid at the second time interval. If the positive sequence voltage is not within the preset operating voltage range, proceed to step 4; otherwise, proceed to step 5. Step 4: The anti-islanding protection will activate if the conditions in Step 3 are met continuously until the first delay (short delay setting) is reached. After the anti-islanding protection activates, or after remote / local anti-islanding operation, if the positive sequence voltage at the installation location of the anti-islanding protection or anti-islanding operation branch protection device returns to the preset voltage range and continues to reach the third delay (reclosing delay setting), the anti-islanding protection will activate reclosing. Step 5: If the conditions in Step 3 are met continuously and the second delay (i.e., the long delay setting) is reached, the anti-islanding protection will activate and the reclosing circuit will be blocked.

2. The active-passive combined anti-islanding protection method according to claim 1, characterized in that: In step 1, the first time interval is 40ms; each protection installation location includes: the distribution network branch connected to the microgrid, other branches on the same busbar as the distribution network branch, and the protection installation locations of each section of the upper part of the distribution network branch.

3. The active-passive combined anti-islanding protection method according to claim 1, characterized in that: In step 2, the positive sequence voltage surge meets the following activation conditions: a first activation condition and a second activation condition. The protection system activates when either activation condition is met. The first startup condition is , The second startup condition is , in, The maximum value among the half-wave integrals of the effective values ​​of the three phase voltages. The maximum value among the half-wave integrals of the effective values ​​of the three phase-to-phase voltages. It is an adjustable positive-sequence voltage mutation threshold for startup.

4. The active-passive combined anti-islanding protection method according to claim 3, characterized in that: Value range: 0.01 U N ~0.5 U N ,in, U N To protect the rated voltage of the corresponding branch at the installation location.

5. The active-passive combined anti-islanding protection method according to claim 1, characterized in that: In step 3, the second time interval is 20ms; the preset voltage range is: 0.85 U N <U1<1.1 U N in, This is the positive sequence voltage value. To protect the system's rated voltage at the installation location.

6. The active-passive combined anti-islanding protection method according to claim 1, characterized in that: In step 4, the first delay, i.e. the short delay setting, is set according to the time difference of the main branch current I segment of the distribution network. An additional time difference is added to the time difference of the main branch, and each time difference is generally taken as 0.2S.

7. The active-passive combined anti-islanding protection method according to claim 1 or 6, characterized in that: In step 4, the third delay is the coincidence delay setpoint. Calculate using the following formula: in U 1 represents the positive sequence voltage acquired at the second time interval. T 0_set For fixed delay, U 1_set For the positive sequence voltage setting, take... U 1_set =0.85U N , T set Let the floating delay be a fixed value, where, To protect the system's rated voltage at the installation location.

8. The active-passive combined anti-islanding protection method according to claim 7, characterized in that: T 0_set The value range is 0.1~0.5S; T set The value range is 20~80S; U 1_set The value is 0.85 U N , U N To protect the rated voltage of the corresponding branch at the installation location.

9. The active-passive combined anti-islanding protection method according to claim 1, characterized in that: In step 5, the second delay, i.e. the long delay setting, is set according to the reclosing time of the reclosing function switch configured at the upper level of the anti-islanding protection installation location and the automatic transfer time of the sectionalizing switch, with a time difference of more than 0.5 seconds added to the longest time of the two.

10. A combined active-passive anti-islanding protection system utilizing the method of any one of claims 1-9, comprising a data acquisition module, a protection activation module, a short-delay anti-islanding protection and reclosing module, and a long-delay anti-islanding protection and blocking reclosing module; characterized in that: The data acquisition module is used to cyclically acquire the positive sequence voltage and zero sequence voltage at the installation locations of the protection devices of each branch of the distribution network connected to the microgrid at a first time interval; after the protection is started, it is used to acquire the positive sequence voltage at the installation locations of the protection devices of the branches connected to the microgrid and the distributed power supply branches of the microgrid at a second time interval. The protection start-up module is equipped with a voltage surge start-up element and a zero-sequence voltage start-up element. When the collected positive-sequence voltage surge or zero-sequence voltage meets the corresponding start-up conditions, the protection is activated. The short-delay anti-islanding protection and reclosing module will activate the anti-islanding protection when the positive sequence voltage is determined to be outside the preset operating voltage range for a continuous period of time. After the anti-islanding protection is activated, or after remote / local anti-islanding operation, if the positive sequence voltage returns to the preset voltage range, the reclosing operation will be performed after the reclosing delay setting. The long-delay anti-islanding protection and reclosing blocking module will activate the anti-islanding protection and block the reclosing when it is determined that the positive sequence voltage is outside the preset operating voltage range for a continuous long delay period.

11. A computer device, comprising a memory, a processor, and a computer program stored in the memory; characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1-9.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the steps of the method according to any one of claims 1-9.

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