Island detection method and device, electronic equipment and storage medium

Abstract

The invention provides an island detection method and device, electronic equipment and a storage medium. The island detection method comprises the following steps: controlling each grid-connected inverter to inject a reactive disturbance sequence into a power grid; wherein the reactive power disturbance sequence comprises the following disturbances in one disturbance period: a positive disturbance, a negative disturbance and a zero disturbance, the disturbance period comprises a plurality of continuously arranged judgment periods, the positive disturbance and the negative disturbance respectively last for one judgment period, and the zero disturbance lasts for the rest judgment periods; the amplitude of the positive disturbance quantity is not equal to that of the negative disturbance quantity; for any grid-connected inverter, judging whether a disturbance reset criterion is met or not according to the power grid frequency of each judgment period; if yes, the grid-connected inverter is controlled to reset the reactive power disturbance sequence to output each disturbance quantity again from the first judgment period; otherwise, judging whether the power grid frequency meets a preset island condition or not to confirm whether the power grid has an island or not.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of power systems, and particularly relates to an islanding detection method, device, electronic device, and storage medium. Background Art

[0002] Currently, grid-connected inverters inject disturbance current into the grid, and then detect the characteristic values (such as frequency, frequency offset, etc.) generated by the disturbance voltage at the point of common coupling, and judge the change of the characteristic values within the detection threshold range to determine whether islanding occurs and trigger islanding protection. However, since different grid-connected inverters are in parallel, there is a probability that the disturbance amounts interfere with each other, resulting in the failure of islanding protection. Summary of the Invention

[0003] The purpose of the present invention is to provide an islanding detection method, device, electronic device, and storage medium, which are used to eliminate the parallel dilution effect randomly caused by the reactive power disturbance sequences between different grid-connected inverters, avoid the interference of the disturbance amounts injected by different inverters during multi-machine parallel connection, and thus improve the reliability of islanding detection.

[0004] In a first aspect, the present application provides an islanding detection method, including: Controlling each grid-connected inverter to inject a reactive power disturbance sequence into the grid; wherein, the reactive power disturbance sequence includes the following disturbance amounts in one disturbance period: a positive disturbance amount, a negative disturbance amount, and a zero disturbance amount. The disturbance period includes a plurality of consecutive judgment periods. The positive disturbance amount and the negative disturbance amount each last for one judgment period, and the zero disturbance amount lasts for the remaining judgment periods. The amplitude of the positive disturbance amount is not equal to the amplitude of the negative disturbance amount; For any one of the grid-connected inverters, perform the following islanding detection steps: Obtain the grid frequency at the point of common coupling in the current disturbance period and the previous disturbance period, and judge whether the disturbance reset criterion is satisfied according to the grid frequency; If so, control the grid-connected inverter to reset the reactive power disturbance sequence to output each disturbance amount again starting from the first judgment period; Otherwise, judge whether the grid frequency satisfies a preset islanding condition to confirm whether islanding occurs in the grid.

[0005] In one implementation, the disturbance reset criterion includes:

[0006] Wherein, represents the synchronization criterion quantity, represents the first cumulative frequency deviation corresponding to the previous disturbance period, represents the second cumulative frequency deviation corresponding to the current disturbance period, is the judgment threshold.

[0007] In one implementation, the first cumulative frequency deviation is:

[0008] The second cumulative frequency deviation is:

[0009] where , represents the frequency deviation value of the current judgment period, represents the grid frequency of the current judgment period, represents the rated grid frequency.

[0010] In one implementation, controlling each grid-connected inverter to inject a reactive power disturbance sequence into the grid includes: In response to the connection point voltages of the grid-connected inverters all being at the zero crossing point, controlling each grid-connected inverter to inject a reactive power disturbance sequence into the grid.

[0011] In one implementation, the disturbance reset criterion further includes: The time interval between the current time and the reset time of the previous reactive power disturbance sequence is greater than a preset interval threshold.

[0012] In one implementation, the amplitude of the negative disturbance amount is one-half of the amplitude of the positive disturbance amount.

[0013] In one implementation, determining whether the grid frequency meets a preset islanding condition includes: Calculating the frequency difference between the current judgment period and the previous judgment period according to the grid frequency; Determining whether the frequency difference meets the islanding condition to confirm whether the grid has an islanding event.

[0014] In a second aspect, the present application provides an islanding detection device, including: A disturbance output module, configured to control each grid-connected inverter to inject a reactive power disturbance sequence into the grid; wherein, the reactive power disturbance sequence includes the following disturbance amounts in a disturbance period: a positive disturbance amount, a negative disturbance amount, and a zero disturbance amount, the disturbance period includes a plurality of continuously set judgment periods, the positive disturbance amount and the negative disturbance amount each last for one judgment period, the zero disturbance amount lasts for the remaining judgment periods, and the amplitude of the positive disturbance amount is not equal to the amplitude of the negative disturbance amount; An islanding detection module, configured to perform the following islanding detection steps for any one of the grid-connected inverters: Obtain the grid frequencies of each judgment period in the current disturbance period and the previous disturbance period through a common connection point, and determine whether the disturbance reset criterion is satisfied according to the grid frequencies of each judgment period; If so, control the grid-connected inverter to reset the reactive power disturbance sequence to output each disturbance amount again starting from the first judgment period; Otherwise, determine whether the grid frequency satisfies a preset islanding condition to confirm whether the grid has islanded.

[0015] In a third aspect, the present application provides an electronic device, including: one or more processors; and one or more memories coupled to the one or more processors and storing instructions thereon, when the instructions are executed alone or jointly by the one or more processors, causing the electronic device to execute the method according to any one of the first aspect.

[0016] In a fourth aspect, the present application provides a non-volatile computer-readable storage medium, the computer-readable storage medium stores computer-executable instructions, when the computer-executable instructions are executed by an electronic device, causing the electronic device to execute the method according to any one of the first aspect.

[0017] Compared with the prior art, the present invention has the following advantages: The present application provides an islanding detection method, device, electronic device and storage medium. By setting a positive disturbance amount, a negative disturbance amount and a zero disturbance amount in a disturbance period, where the amplitude of the positive disturbance amount is not equal to the amplitude of the negative disturbance amount, so that there is always a non-zero total reactive power disturbance sequence in the power grid. In this way, the parallel dilution effect randomly caused by the reactive power disturbance sequences between different grid-connected inverters can be eliminated, and the interference between the disturbance amounts injected by different inverters during multi-machine parallel connection can be avoided, thereby improving the reliability of islanding detection.

[0018] In addition, in the solution of the present application, a disturbance reset criterion based on the first cumulative frequency deviation corresponding to the previous disturbance period and the second cumulative frequency deviation corresponding to the current disturbance period is provided, and the moment when the connection point voltage is at the zero-crossing point is set as the moment when all grid-connected inverters need to synchronously inject reactive power disturbance sequences into the power grid, which can ensure the time synchronization of the reactive power disturbance sequences injected by each grid-connected inverter, and the reactive power disturbance sequences of each grid-connected inverter are synchronized, which can further improve the accuracy of islanding detection. Description of the Drawings

[0019] The inclusion of the drawings is to provide a further understanding of the present application, and they are incorporated and constitute a part of the present application. The drawings illustrate the embodiments of the present application and, together with this specification, serve to explain the principles of the present application. In the drawings: Figure 1It is a flowchart of an islanding detection method shown in an exemplary embodiment of the present application; Figure 2 It is a waveform schematic diagram of a reactive power disturbance sequence shown in an exemplary manner of the present application; Figure 3 It is a schematic diagram of a calculation method for a synchronization criterion quantity in an exemplary manner of the present application; Figure 4 It is a timing block diagram of an islanding detection method provided in an exemplary manner of the present application; Figure 5 It is an example diagram of a scenario where islanding has not occurred provided in an exemplary manner of the present application; Figure 6 It is an example diagram of a scenario after islanding has occurred provided in an exemplary manner of the present application; Figure 7 It is a schematic diagram of an islanding detection device provided in an exemplary manner of the present application; Figure 8 It is a schematic diagram of an electronic device provided in an exemplary manner of the present application. Detailed implementation manners

[0020] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following-described drawings are only some examples or embodiments of the present application. For those of ordinary skill in the art, without creative efforts, the present application can also be applied to other similar scenarios based on these drawings. Unless obvious from the language context or otherwise stated, the same reference numerals in the figures represent the same structure or operation.

[0021] As shown in the present application and the claims, unless the context clearly indicates an exception, words such as "a", "an", "one", and / or "the" are not specifically singular and may also include plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of the clearly identified steps and elements, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0022] In addition, it should be noted that using words such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Without further declaration, the above words have no special meaning, so it cannot be understood as a limitation on the protection scope of the present application. In addition, although the terms used in the present application are selected from well-known and commonly used terms, some of the terms mentioned in the description of the present application may be selected by the applicant according to his or her judgment. Their detailed meanings are described in the relevant parts of this description. In addition, it is required to understand the present application not only through the actual terms used, but also through the meaning implied by each term.

[0023] Figure 1 FIG. 100 is a flowchart of an islanding detection method shown in an exemplary embodiment of the present application, including: S101, controlling each grid-connected inverter to inject a reactive power disturbance sequence into the power grid; wherein, the reactive power disturbance sequence includes the following disturbance quantities in one disturbance period: a positive disturbance quantity, a negative disturbance quantity, and a zero disturbance quantity. The disturbance period includes a plurality of consecutive judgment periods. The positive disturbance quantity and the negative disturbance quantity each last for one judgment period, and the zero disturbance quantity lasts for the remaining judgment periods. The amplitudes of the positive disturbance quantity and the negative disturbance quantity are not equal; S102, for any grid-connected inverter, perform the following islanding detection steps: S1021, obtain the grid frequencies of each judgment period in the current disturbance period and the previous disturbance period through the point of common coupling, and judge whether the disturbance reset criterion is satisfied according to the grid frequencies of each judgment period; if so, execute S1022, otherwise, execute S1023; S1022, controlling the grid-connected inverter to reset the reactive power disturbance sequence to output each disturbance quantity again starting from the first judgment period; S1023, judge whether the grid frequency satisfies a preset islanding condition to confirm whether an islanding occurs in the power grid.

[0024] It will be understood that "each grid-connected inverter" may specifically refer to two or more grid-connected inverters. Figure 2 FIG. 200 is a waveform schematic diagram of the reactive power disturbance sequence shown in an exemplary manner of the present application. As Figure 2 , as an example, in the case of two grid-connected inverters, the reactive power disturbance sequences respectively output by each grid-connected inverter (i.e., grid-connected inverter 1 and grid-connected inverter 2) to the power grid. Figure 2 The three waveforms shown from top to bottom respectively represent the waveform (1) of the reactive power disturbance sequence injected by grid-connected inverter 1, the waveform (2) of the reactive power disturbance sequence injected by grid-connected inverter 2, and the waveform (3) of the total reactive power disturbance sequence in the power grid. Wherein, the horizontal axis represents time, and the vertical axis represents amplitude.

[0025] As Figure 2 , for two reactive power disturbance sequences with the same time scale, one disturbance period is 0 to 4t1, including four consecutive judgment periods, which are 0 to t1, t1 to 2t1, 2t1 to 3t1, and 3t1 to 4t1. The subsequent 4t1 to 5t1 repeats the disturbance quantity of 0 to t1. f[0] to f[1] respectively represent the grid frequencies of the corresponding judgment periods. The reactive power disturbance sequence injected by grid-connected inverter 1 includes a zero disturbance quantity, a positive disturbance quantity, a zero disturbance quantity, a negative disturbance quantity, and a zero disturbance quantity that each last for five judgment periods in sequence. The reactive power disturbance sequence injected by grid-connected inverter 2 includes a zero disturbance quantity, a negative disturbance quantity, a zero disturbance quantity, a positive disturbance quantity, and a zero disturbance quantity that each last for five judgment periods in sequence.

[0026] Since in the embodiments of the present application, the amplitudes of the positive disturbance quantity and the negative disturbance quantity are not equal, even if the grid-connected inverter 1 and the grid-connected inverter 2 do not start injecting disturbances from the same judgment period, the total reactive power disturbance sequence in the power grid will not be completely cancelled out, thereby eliminating the parallel dilution effect between different grid-connected inverters, avoiding the interference of the disturbance quantities injected by different inverters during multi-inverter parallel connection, and thus improving the reliability of island detection.

[0027] The amplitudes of the positive disturbance quantity and the negative disturbance quantity being not equal may mean that the amplitude of the positive disturbance quantity is greater than the amplitude of the negative disturbance quantity, or may mean that the amplitude of the negative disturbance quantity is greater than the amplitude of the positive disturbance quantity.

[0028] Exemplarily, such as Figure 2 where Δi q + represents the amplitude of the positive disturbance quantity, and Δi q - represents the amplitude of the negative disturbance quantity, and the amplitude of the negative disturbance quantity is one-half of the amplitude of the positive disturbance quantity.

[0029] In one implementation manner, the disturbance reset criterion includes:

[0030] wherein, represents the synchronization criterion quantity, represents the first cumulative frequency deviation corresponding to the previous disturbance period, represents the second cumulative frequency deviation corresponding to the current disturbance period, is the judgment threshold.

[0031] The embodiments of the present application design the disturbance reset criterion by comprehensively considering the cumulative frequency deviations within two adjacent disturbance periods, thereby ensuring the reliability of the disturbance reset for each grid-connected inverter. The judgment threshold can be determined according to the actual working conditions, and there is no limitation thereto.

[0032] In one implementation manner, the first cumulative frequency deviation is:

[0033] The second cumulative frequency deviation is:

[0034] wherein, , represents the frequency deviation value of the current judgment period, represents the power grid frequency of the current judgment period, represents the rated power grid frequency.

[0035] The first cumulative frequency deviation and the second cumulative frequency deviation can be calculated using a sliding window method.

[0036] Figure 3 It is a schematic diagram 300 of the calculation method of the exemplary synchronization criterion quantity in this application. As Figure 3 , as an example, in the case of two grid-connected inverters, the first cumulative frequency deviation is expressed as , , , the cumulative value of the frequency deviation values respectively represented, and the second cumulative frequency deviation is expressed as , , , the cumulative value of the frequency deviation values respectively represented. When the two grid-connected inverters adopt the above form of reactive power disturbance sequence, even if the timing relationship between reactive power disturbance sequence 1 and reactive power disturbance sequence 2 is different, the total reactive power disturbance amount in the power grid still changes periodically. Therefore, when the synchronization criterion quantity exceeds the judgment threshold, it indicates that the frequency change situation in the current disturbance period and the previous disturbance period is relatively large, and islanding may occur in the power grid. For each grid-connected inverter, its reactive power disturbance sequence needs to be reset, that is, the corresponding disturbance amount is re-output starting from the first judgment period of the reactive power disturbance sequence; conversely, when the synchronization criterion quantity does not exceed the judgment threshold, it indicates that the current frequency change situation is normal, and it is not necessary to reset the reactive power disturbance of each grid-connected inverter.

[0037] In one implementation, the disturbance reset criterion further includes: The time interval between the current time and the reset time of the previous reactive power disturbance sequence is greater than a preset interval threshold.

[0038] In other words, a grid-connected inverter is only allowed to reset the reactive power disturbance sequence when the synchronization criterion quantity is greater than the judgment threshold and at the same time the time interval between the current time and the reset time of the previous reactive power disturbance sequence is greater than the preset interval threshold. If the time interval between the current time and the reset time of the previous reactive power disturbance sequence is less than or equal to this interval threshold, then even if the synchronization criterion quantity is greater than the judgment threshold, this grid-connected inverter is not allowed to reset the reactive power disturbance sequence again.

[0039] For example, if the time since the last reset time of the reactive power disturbance sequence has not exceeded 2 s, then even if the synchronization criterion quantity is greater than the judgment threshold, the reactive power disturbance sequence of this grid-connected inverter is not reset. This can avoid the reactive power disturbance sequence being repeatedly reset, resulting in too long islanding detection time, and can also ensure effective synchronization between grid-connected inverters, avoiding synchronization anomalies and affecting the accuracy of subsequent islanding detection.

[0040] In one implementation, controlling each grid-connected inverter to inject a reactive power disturbance sequence into the power grid includes: In response to the connection point voltages of the grid-connected inverters all being at the zero-crossing point, controlling each grid-connected inverter to inject a reactive power disturbance sequence into the power grid.

[0041] Based on the time consistency of the zero-crossing points of the power grid, controlling all grid-connected inverters to trigger the islanding detection process 100 at the same moment, thereby solving the problem of time inconsistency caused by the power-on and calculation timing differences between different inverters and improving the accuracy of islanding detection.

[0042] Specifically, the moment of the "zero-crossing point" can be determined according to the phase-locked angle of the power grid. When the phase-locked angle of the power grid is equal to 2π, the corresponding grid-connected inverter is at the zero-crossing point.

[0043] In other words, in an actual scenario, since each grid-connected inverter will trigger the step of injecting the disturbance sequence only when it reaches the expected time for injecting the disturbance and detection, it is very likely that the timing of each grid-connected inverter to execute this step cannot be kept consistent. To solve this problem, in this embodiment, it is selected to make each grid-connected inverter trigger the step of injecting the disturbance sequence at the same specified moment, and the moment when the phase-locked angle of the power grid is equal to 2π is selected as this specified moment, because the connection point voltage will never be affected by the injected reactive power disturbance sequence.

[0044] In one implementation, determining whether the power grid frequency meets a preset islanding condition includes: Calculating the frequency difference between the current judgment period and the previous judgment period according to the power grid frequency; Judging whether the frequency difference meets the islanding condition to confirm whether an islanding has occurred in the power grid.

[0045] The islanding condition can be a preset frequency threshold range. If the calculated frequency difference does not belong to the set frequency threshold range, it is determined that an islanding has occurred in the power grid, and then the grid-connected inverter immediately triggers islanding protection; if the frequency difference belongs to the frequency threshold range, it is determined that no islanding has occurred in the power grid, and then it can wait for the next trigger of the islanding detection process 100.

[0046] It will be understood that in addition to the frequency difference, the grid-connected inverter can also use other characteristic values (such as harmonics, etc.) and their corresponding islanding conditions to judge whether an islanding has occurred, and this is not limited.

[0047] Figure 4 It is the timing block diagram 400 of the islanding detection method exemplarily provided by this application. As Figure 4 , for any grid-connected inverter, it includes: S401, judging whether the disturbance reset criterion is met. If so, execute S40? Otherwise, do not process; S402, reset the reactive power disturbance sequence; S403, update each disturbance quantity until the next disturbance period, and then go to step S404; S404, determine whether the islanding condition is met. If yes, execute S405; otherwise, end the current islanding detection process; S405, trigger islanding protection.

[0048] Figure 5 This is the example diagram 500 of the scenario where islanding does not occur provided exemplarily by this application. As Figure 5 , as an example, in the case of two grid-connected inverters, the reactive power disturbance sequences output by each grid-connected inverter (i.e., grid-connected inverter 1 and grid-connected inverter 2) to the power grid respectively. Figure 5 The four waveforms shown successively from top to bottom respectively represent the waveform (1) of the reactive power disturbance sequence injected by grid-connected inverter 1, the waveform (2) of the reactive power disturbance sequence injected by grid-connected inverter 2, the waveform (3) of the total reactive power disturbance sequence in the power grid, and the waveform (4) of the frequency change on the side of the point of common coupling PCC. Among them, the horizontal axis represents time, the vertical axis represents amplitude, and Δi q + represents the amplitude of the positive disturbance quantity, and Δi q - represents the amplitude of the negative disturbance quantity, and Δf represents the frequency on the PCC side.

[0049] As Figure 5 in waveform (4), in the case where islanding does not occur, the frequency Δf on the PCC side is always clamped by the power grid near the rated frequency, and the reactive power disturbance sequence has no effect on the power grid frequency.

[0050] Figure 6 This is the example diagram 600 of the scenario after islanding occurs provided exemplarily by this application. As Figure 6 , as an example, in the case of two grid-connected inverters, the reactive power disturbance sequences output by each grid-connected inverter (i.e., grid-connected inverter 1 and grid-connected inverter 2) to the power grid respectively. Figure 6 The four waveforms shown successively from top to bottom respectively represent the waveform (1) of the reactive power disturbance sequence injected by grid-connected inverter 1, the waveform (2) of the reactive power disturbance sequence injected by grid-connected inverter 2, the waveform (3) of the total reactive power disturbance sequence in the power grid, and the waveform (4) of the frequency change on the side of the point of common coupling PCC. Among them, the horizontal axis represents time, the vertical axis represents amplitude, and Δi q + represents the amplitude of the positive disturbance quantity, and Δi q - represents the amplitude of the negative disturbance quantity, and Δf represents the frequency on the PCC side.

[0051] As Figure 6Medium waveform (4). After islanding occurs, the frequency on the PCC side changes according to the change of the total reactive power disturbance sequence in the power grid. Since the grid frequencies detected by grid-connected inverter 1 and grid-connected inverter 2 are at the same point, and the timing of executing the islanding detection process is the same (that is, injecting a reactive power disturbance sequence into the power grid when the voltage at the connection point is at the zero crossing point), then as Figure 6 shown in the judgment period corresponding to 4t0 - 9t0 in (1) and (2), after the disturbance reset criterion is satisfied, the reactive power disturbance sequence re-injected into the power grid will remain exactly the same. Therefore, combining the moment when the voltage at the connection point is at the zero crossing point and the disturbance reset criterion can quickly synchronize the reactive power disturbance sequences of each grid-connected inverter, which can avoid multiple resets to synchronize the disturbances of each grid-connected inverter, reduce the number of resets, and can capture the islanding existing in the power grid faster.

[0052] Figure 7 Figure 700 is a schematic diagram of an islanding detection device exemplarily provided by the present application, including: a disturbance output module 701 and an islanding detection module 702; wherein: The disturbance output module 701 is used to control each grid-connected inverter to inject a reactive power disturbance sequence into the power grid; wherein, the reactive power disturbance sequence includes the following disturbance amounts in a disturbance period: a positive disturbance amount, a negative disturbance amount, and a zero disturbance amount. The disturbance period includes four consecutive judgment periods, and the zero disturbance amount is set in the first judgment period and the third judgment period, and the amplitude of the positive disturbance amount is not equal to the amplitude of the negative disturbance amount; The islanding detection module 702 is used to perform the following islanding detection steps for any grid-connected inverter: Obtain the grid frequency of the common connection point in the current disturbance period and the previous disturbance period, and judge whether the disturbance reset criterion is satisfied according to the grid frequency; If so, control the grid-connected inverter to reset the reactive power disturbance sequence to re-output the corresponding disturbance amount starting from the first judgment period; Otherwise, judge whether the grid frequency satisfies the preset islanding condition to confirm whether islanding has occurred in the power grid.

[0053] In one implementation, the disturbance reset criterion includes:

[0054] wherein, represents the synchronization criterion quantity, represents the first cumulative frequency deviation corresponding to the previous disturbance period, represents the second cumulative frequency deviation corresponding to the current disturbance period, is the judgment threshold.

[0055] In one implementation, the first cumulative frequency deviation is:

[0056] The second cumulative frequency deviation is:

[0057] Wherein, , represents the frequency deviation value of the current judgment period, represents the grid frequency of the current judgment period, represents the rated grid frequency.

[0058] In one implementation, the disturbance output module 701 is specifically configured to: In response to the connection point voltages of the grid-connected inverters all being at the zero crossing point, control each grid-connected inverter to inject a reactive power disturbance sequence into the grid.

[0059] In one implementation, the disturbance reset criterion further includes: The time interval between the current time and the reset time of the previous reactive power disturbance sequence is greater than a preset interval threshold.

[0060] In one implementation, the amplitude of the negative disturbance amount is one-half of the amplitude of the positive disturbance amount.

[0061] In one implementation, the islanding detection module 702 is specifically configured to: Calculate the frequency difference between the current judgment period and the previous judgment period according to the grid frequency; Judge whether the frequency difference satisfies the islanding condition to confirm whether an islanding occurs in the grid.

[0062] The above-mentioned islanding detection device 700 sets a positive disturbance amount, a negative disturbance amount, and a zero disturbance amount in a disturbance period, wherein the amplitudes of the positive disturbance amount and the negative disturbance amount are not equal, so that there is always a non-zero total disturbance in the grid. In this way, the parallel dilution effect randomly caused by the reactive power disturbance sequences between different grid-connected inverters can be eliminated, and the interference between the disturbance amounts injected by different inverters during multi-machine parallel connection can be avoided, thereby improving the reliability of islanding detection.

[0063] Furthermore, as Figure 8 , the present application also exemplarily provides a schematic diagram 800 of an electronic device, including a memory 801 and a processor 802. Instructions are stored in the memory 801, and when the instructions are executed by the processor 802, the processor 802 executes the method as Figure 1 shown.

[0064] It should be understood that the processor mentioned in the embodiments of the present application may be a CPU, or may also be other general-purpose processors, DSPs, ASICs, FPGAs, or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0065] It should also be understood that the memory mentioned in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory, an erasable programmable read-only memory, an electrically erasable programmable read-only memory, or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example but not limitation, many forms of RAM are available, such as static random access memory, dynamic random access memory, synchronous dynamic random access memory, double data rate synchronous dynamic random access memory, enhanced synchronous dynamic random access memory, synchronous link dynamic random access memory, and direct memory bus random access memory.

[0066] The present application also provides a non-volatile computer-readable storage medium, which stores computer-executable instructions. When the computer-executable instructions are executed by an electronic device, the electronic device is caused to execute the steps of any of the methods mentioned above.

[0067] A computer-readable medium may include a propagated data signal having computer program code embodied therein, for example, on a baseband or as part of a carrier wave. The propagated signal may take many forms, including electromagnetic, optical, or the like, or suitable combinations thereof. A computer-readable medium may be any computer-readable medium other than a computer-readable storage medium, which can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. The program code located on the computer-readable medium may be propagated through any appropriate medium, including radio, cable, fiber optic cable, RF signals, or similar media, or any combination of the foregoing.

[0068] The basic concepts have been described above. Obviously, for those skilled in the art, the above invention disclosure is only an example and does not constitute a limitation to the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to the present application. Such modifications, improvements, and corrections are proposed in the present application, so such modifications, improvements, and corrections still fall within the spirit and scope of the exemplary embodiments of the present application.

[0069] Meanwhile, this application uses specific terms to describe the embodiments of this application. For example, "an embodiment", "one embodiment", and / or "some embodiments" mean a certain feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that "an embodiment" or "one embodiment" or "an alternative embodiment" mentioned twice or more at different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application can be appropriately combined.

[0070] Some aspects of this application can be executed entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. The above-mentioned hardware or software can all be referred to as "data blocks", "modules", "engines", "units", "components", or "systems". The processor can be one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DAPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, or combinations thereof. In addition, aspects of this application may be embodied as a computer product located in one or more computer-readable media, which includes computer-readable program code. For example, computer-readable media can include, but are not limited to, magnetic storage devices (such as hard disks, floppy disks, magnetic tapes...), optical discs (such as compact discs CD, digital versatile discs DVD...), smart cards, and flash memory devices (such as cards, sticks, key drives...).

[0071] The computer-readable medium may contain a propagated data signal containing computer program code, such as on a baseband or as part of a carrier wave. This propagated signal may have various forms of manifestation, including electromagnetic form, optical form, etc., or a suitable combination of forms. The computer-readable medium can be any computer-readable medium other than a computer-readable storage medium, which can be connected to an instruction execution system, apparatus, or device to implement communication, propagation, or transmission for use of the program. The program code located on the computer-readable medium can be propagated through any suitable medium, including radio, cable, fiber optic cable, radio frequency signal, or similar media, or any combination of the above media.

[0072] Similarly, it should be noted that, in order to simplify the description of this application disclosure and thus help the understanding of one or more embodiments of the invention, in the previous description of the embodiments of this application, sometimes multiple features are grouped into one embodiment, drawing, or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than those mentioned in the claims. In fact, the features of the embodiment are fewer than all the features of the single embodiment disclosed above.

[0073] In some embodiments, numbers are used to describe components and the quantity of attributes. It should be understood that such numbers used in the description of embodiments are, in some examples, modified by the modifiers "about", "approximately" or "substantially". Unless otherwise stated, "about", "approximately" or "substantially" indicate that the stated numbers allow a variation of ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may vary according to the characteristics required by individual embodiments. In some embodiments, the numerical parameters should consider the specified significant digits and adopt the method of retaining the general number of digits. Although the numerical ranges and parameters used in some embodiments of the present application to confirm the breadth of their scope are approximate values, in specific embodiments, such numerical settings are made as precise as possible within the feasible range.

[0074] Although the present application has been described with reference to the current specific embodiments, those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the present application, and various equivalent changes or substitutions can be made without departing from the spirit of the present application. Therefore, as long as the changes and modifications of the above embodiments are within the scope of the spirit of the present application, they will fall within the scope of the claims of the present application.

Claims

1. An islanding detection method, characterized in that, Including: Controlling each grid-connected inverter to inject a reactive power disturbance sequence into the grid; wherein, the reactive power disturbance sequence includes the following disturbance quantities in a disturbance period: a positive disturbance quantity, a negative disturbance quantity, and a zero disturbance quantity. The disturbance period includes a plurality of continuously set judgment periods. The positive disturbance quantity and the negative disturbance quantity each last for one judgment period, and the zero disturbance quantity lasts for the remaining judgment periods. The amplitude of the positive disturbance quantity is not equal to the amplitude of the negative disturbance quantity; For any one of the grid-connected inverters, perform the following islanding detection steps: Obtain the grid frequencies of each judgment period in the current disturbance period and the previous disturbance period through the point of common coupling, and judge whether the disturbance reset criterion is satisfied according to the grid frequencies of each judgment period; If so, control the grid-connected inverter to reset the reactive power disturbance sequence to output each disturbance quantity again starting from the first judgment period; Otherwise, judge whether the grid frequency satisfies a preset islanding condition to confirm whether the grid has an islanding event.

2. The method according to claim 1, characterized in that, The disturbance reset criterion includes: Among them, represents the synchronization criterion quantity, represents the first cumulative frequency deviation corresponding to the previous disturbance period, represents the second cumulative frequency deviation corresponding to the current disturbance period, is the judgment threshold.

3. The method according to claim 2, wherein The first cumulative frequency deviation is: The second cumulative frequency deviation is: Among them, , represents the frequency deviation value of the current judgment period, represents the grid frequency of the current judgment period, represents the rated grid frequency.

4. The method according to any one of claims 1 to 3, characterized in that The controlling each grid-connected inverter to inject a reactive power disturbance sequence into the grid includes: In response to the connection point voltages of the grid-connected inverters all being at zero crossings, controlling the grid-connected inverters to inject a reactive power disturbance sequence into the grid.

5. The method according to any one of claims 1-3, characterized in that, The disturbance reset criterion further includes: The time interval between the current time and the reset time of the previous reactive power disturbance sequence is greater than a preset interval threshold.

6. The method according to any one of claims 1-3, characterized in that, The amplitude of the negative disturbance quantity is one-half of the amplitude of the positive disturbance quantity.

7. The method according to any one of claims 1 to 3, characterized in that, The judging whether the grid frequency satisfies a preset islanding condition includes: Calculating the frequency difference between the current judgment period and the previous judgment period according to the grid frequency; Judging whether the frequency difference satisfies the islanding condition to confirm whether the grid has an islanding event.

8. An islanding detection device, characterized in that, Including: A disturbance output module for controlling each grid-connected inverter to inject a reactive power disturbance sequence into the grid; wherein, the reactive power disturbance sequence includes the following disturbance quantities in a disturbance period: a positive disturbance quantity, a negative disturbance quantity, and a zero disturbance quantity. The disturbance period includes a plurality of continuously set judgment periods. The positive disturbance quantity and the negative disturbance quantity each last for one judgment period, and the zero disturbance quantity lasts for the remaining judgment periods. The amplitude of the positive disturbance quantity is not equal to the amplitude of the negative disturbance quantity; An islanding detection module for obtaining the grid frequencies of each judgment period in the current disturbance period and the previous disturbance period through the point of common coupling, and judging whether the disturbance reset criterion is satisfied according to the grid frequencies of each judgment period; If so, control the grid-connected inverter to reset the reactive power disturbance sequence to output each disturbance quantity again starting from the first judgment period; Otherwise, judge whether the grid frequency satisfies a preset islanding condition to confirm whether the grid has an islanding event.

9. An electronic device, characterized in that, Including: One or more processors; And One or more memories coupled to and storing instructions on the one or more processors, which when executed by the one or more processors alone or in combination, cause the electronic device to perform the method according to any one of claims 1-7.

10. A non-volatile computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions which, when executed by an electronic device, cause the electronic device to perform the method according to any one of claims 1-7.

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