Anti-islanding detection method and device, electronic equipment and storage medium

Abstract

The invention relates to the technical field of inverters, in particular to an anti-islanding detection method and device, electronic equipment and a storage medium. The method comprises the steps of starting a reactive power disturbance mode to apply a reactive power current disturbance signal to a power grid for disturbance, and converting the reactive power disturbance mode into a frequency disturbance mode when it is determined that the frequency of the power grid fluctuates; further, at least applying a frequency disturbance signal with a first preset frequency value to the power grid for at least three times, and judging whether an islanding effect occurs or not according to a disturbance result of the frequency disturbance signal; the disturbance directions of the at least three times of frequency disturbance signals at least comprise a first disturbance direction and a second disturbance direction. Therefore, by adopting an anti-islanding detection mode of combining reactive power disturbance and frequency disturbance of changing the disturbance direction, the accuracy of anti-islanding detection can be improved while the influence of disturbance on the quality of the output electric energy of the inverter can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of inverters, and in particular to an anti-islanding detection method, device, electronic device and storage medium. Background Art

[0002] With the increasing widespread application of distributed power generation from new energy sources such as solar energy and wind energy, a large number of distributed power sources are connected to the power grid. However, when the power grid is disconnected due to a fault or maintenance, if the distributed power source (such as a photovoltaic grid-connected system) continues to supply power to the local load, an independent power generation system will be formed. This is the so-called "island effect". The island state may cause harm to power equipment and maintenance personnel. For example, the voltage and frequency in the island may exceed the normal range, affecting the normal operation of the load and even damaging the equipment; it will also interfere with the recovery of the power grid and may pose a safety threat to personnel who are performing power grid maintenance. In order to ensure the safe and stable operation of distributed power sources and the safety of power maintenance personnel, the inverter needs to detect the island state in time and take corresponding measures, such as stopping the output of distributed power sources.

[0003] At present, the inverter mainly adopts passive detection method and active detection method in anti-islanding detection. However, the passive detection method has the problem of low probability of detecting islanding effect and large blind area; while the active detection method is prone to false detection, and due to the introduction of disturbance, it may have an adverse effect on the power quality of distributed power output.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0005] In view of this, the purpose of the present application is to provide an anti-islanding detection method, device, electronic device and storage medium, which can improve the accuracy of anti-islanding detection while reducing the impact of disturbances on the output power quality of the inverter.

[0006] This application mainly includes the following aspects:

[0007] In a first aspect, an embodiment of the present application provides an anti-islanding detection method, the method comprising:

[0008] Start the reactive disturbance mode to apply reactive current disturbance signal to the power grid for disturbance;

[0009] In response to the disturbance of the reactive current disturbance signal, determining an instantaneous frequency value and an average frequency value of the power grid;

[0010] In response to determining that an absolute difference between the instantaneous frequency value and the average frequency value is greater than or equal to a preset frequency fluctuation threshold, converting the reactive disturbance mode into a frequency disturbance mode;

[0011] In response to determining that the disturbance mode of the power grid is the frequency disturbance mode, applying a frequency disturbance signal of a first preset frequency value to the power grid at least three times in sequence to disturb the power grid, and judging whether an islanding effect occurs according to a result of the disturbance of the frequency disturbance signal;

[0012] The disturbance directions of the frequency disturbance signals of the at least three first preset frequency values ​​include at least a first disturbance direction and a second disturbance direction, and the first disturbance direction and the second disturbance direction are opposite to each other.

[0013] In a second aspect, an embodiment of the present application further provides an anti-islanding detection device, the device comprising:

[0014] The reactive disturbance module is used to start the reactive disturbance mode to apply a reactive current disturbance signal to the power grid for disturbance;

[0015] A frequency fluctuation determination module, configured to determine an instantaneous frequency value and an average frequency value of the power grid in response to a disturbance of the reactive current disturbance signal;

[0016] a disturbance mode switching module, configured to transform the reactive disturbance mode into a frequency disturbance mode in response to determining that the absolute difference between the instantaneous frequency value and the average frequency value is greater than or equal to a preset frequency fluctuation threshold;

[0017] a frequency disturbance module, configured to, in response to determining that the disturbance mode of the power grid is the frequency disturbance mode, sequentially apply a frequency disturbance signal of a first preset frequency value to the power grid for at least three times to perform disturbance, and determine whether an islanding effect occurs according to a result of the disturbance of the frequency disturbance signal;

[0018] The disturbance directions of the frequency disturbance signals of the at least three first preset frequency values ​​include at least a first disturbance direction and a second disturbance direction, and the first disturbance direction and the second disturbance direction are opposite to each other.

[0019] In the third aspect, an embodiment of the present application also provides an electronic device, comprising: a processor, a memory and a bus, the memory storing machine-readable instructions executable by the processor, when the electronic device is running, the processor and the memory communicate through the bus, and the machine-readable instructions are executed by the processor to execute the steps of the anti-island detection method described in the first aspect or any possible implementation manner of the first aspect.

[0020] In a fourth aspect, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the anti-island detection method described in the above-mentioned first aspect or any possible implementation manner of the first aspect are executed.

[0021] The embodiment of the present application provides an anti-islanding detection method, device, electronic device and storage medium. By adopting an anti-islanding detection method that combines reactive disturbance with frequency disturbance with a change in disturbance direction, compared with the anti-islanding detection method in the prior art that is prone to false detection and has an adverse effect on the power quality output by the distributed power supply, the embodiment of the present application disturbs the power grid by first starting a reactive disturbance mode, and when it is initially detected that there is a risk of being in an islanding state, the reactive disturbance mode is switched to a frequency disturbance mode with a change in disturbance direction with a smaller first preset frequency value to perform a secondary disturbance on the power grid, which can reduce the impact on the output power quality. In addition, the embodiment of the present application can prevent false detection caused by the consistency between the power grid frequency fluctuation direction and the disturbance direction by performing a secondary disturbance on the power grid according to frequency disturbance modes with different disturbance directions.

[0022] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A flow chart of an anti-islanding detection method provided by an embodiment of the present application is shown;

[0025] Figure 2 A flowchart of an anti-islanding detection method provided by a specific embodiment of the present application is shown;

[0026] Figure 3 One of the structural schematic diagrams of an anti-islanding detection device provided in an embodiment of the present application is shown;

[0027] Figure 4 A second structural schematic diagram of an anti-islanding detection device provided in an embodiment of the present application is shown;

[0028] Figure 5 A schematic structural diagram of an electronic device provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0029] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It should be understood that the drawings in the present application only serve the purpose of explanation and description and are not used to limit the scope of protection of the present application. In addition, it should be understood that the schematic drawings are not drawn in real proportion. The flowchart used in this application shows the operations implemented according to some embodiments of the present application. It should be understood that the operations of the flowchart can be implemented out of sequence, and the steps without logical context can be reversed in order or implemented simultaneously. In addition, those skilled in the art, under the guidance of the content of the present application, can add one or more other operations to the flowchart, or remove one or more operations from the flowchart.

[0030] In addition, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0031] In order to enable those skilled in the art to use the contents of this application, the following implementation methods are given in combination with the specific application scenario of "distributed power supply grid connection". For those skilled in the art, the general principles defined here can be applied to other embodiments and application scenarios without departing from the spirit and scope of this application.

[0032] The following methods, devices, electronic devices or computer-readable storage media of the embodiments of the present application can be applied to any scenario where a photovoltaic system needs to be connected to the grid. The embodiments of the present application are not limited to specific application scenarios. Any solution using the anti-islanding detection method and device provided by the embodiments of the present application is within the scope of protection of the present application.

[0033] It is worth noting that before the present application was proposed, the inverter mainly adopted passive detection method and active detection method in anti-islanding detection. Among them, the passive detection method is to detect the grid voltage and grid frequency at the coupling point between the inverter output end and the grid, and disconnect the inverter from the grid when the islanding effect conditions are met. This detection method mainly includes overvoltage protection, undervoltage protection, overfrequency protection, underfrequency protection, voltage harmonics, etc. The power quality of the inverter output is high, but the probability of detecting the islanding effect is low and the blind area is large; the active detection method is that the inverter actively introduces changes or disturbances to the output current, causing the voltage parameters at the coupling point between the inverter and the grid to change and exceed the set range, so that the inverter stops running. This detection method mainly includes active frequency offset and sliding frequency offset. Although this method has a higher probability of detecting the islanding effect and a smaller blind area than the passive detection method, due to the introduction of disturbance, the stability is not good, which will affect some power quality of the inverter. In addition, for the frequency-increasing active power method in the active detection method, due to the photovoltaic panels at the input, when the inverter is already operating at the maximum power of the panels, the active power cannot be increased as required, and there is a detection blind spot.

[0034] In response to the above problems, the embodiments of the present application provide an anti-islanding detection method, device, electronic device and storage medium, which applies a reactive current disturbance signal to the power grid by starting a reactive disturbance mode, and when it is determined that the power grid frequency fluctuates, the reactive disturbance mode is converted into a frequency disturbance mode; further, a frequency disturbance signal of a first preset frequency value is applied to the power grid at least three times, and whether an islanding effect occurs is determined based on the result of the frequency disturbance signal disturbance; the disturbance direction of the at least three frequency disturbance signals includes at least a first disturbance direction and a second disturbance direction. In this way, the present application can improve the accuracy of anti-islanding detection while reducing the impact of disturbance on the output power quality of the inverter by adopting an anti-islanding detection method that combines reactive disturbance with frequency disturbance with a changed disturbance direction.

[0035] To facilitate the understanding of the present application, the technical solution provided by the present application is described in detail below in conjunction with specific embodiments.

[0036] Figure 1 This is a flow chart of an anti-islanding detection method provided in an embodiment of the present application. Figure 1 As shown, the anti-islanding detection method provided in the embodiment of the present application can be applied to an inverter in a distributed power source, such as a photovoltaic grid-connected system, and the method includes the following steps:

[0037] S101: Start the reactive disturbance mode to apply a reactive current disturbance signal to the power grid for disturbance.

[0038] It should be noted that the reactive disturbance method is a method for detecting the islanding effect, which is mainly used in the connection between distributed power sources (such as photovoltaic grid-connected systems, wind power generation systems, etc.) and the power grid. The reactive disturbance method can cause the voltage and frequency of the system to change by changing the reactive current output by the inverter, that is, introducing a disturbance signal of the reactive current, so as to determine whether the system is in an islanding state. Specifically, when the power grid is connected normally, due to the strong support of the power grid, the impact of injected reactive current on the system voltage and frequency is small. When the islanding effect occurs, the distributed power source and the local load form an independent small system. At this time, the injection of reactive current will cause the voltage and frequency of the system to change significantly, thereby determining the possibility of being in an islanding state.

[0039] Based on this, the embodiment of the present application first controls the start of the reactive disturbance mode to apply a reactive current disturbance signal to the power grid to perform a preliminary anti-islanding detection. Specifically, it is possible to preliminarily judge whether there is a risk of an islanding effect based on the fluctuation of the power grid frequency after the reactive disturbance mode is adopted.

[0040] In the specific implementation, for the control strategy of starting the reactive disturbance mode to apply the reactive current disturbance signal to the power grid for disturbance, a positive feedback reactive current disturbance strategy or a periodic reactive current disturbance strategy can be adopted. Specifically, the positive feedback reactive current disturbance strategy is to dynamically adjust the amplitude of the reactive disturbance current according to the deviation between the instantaneous frequency of the power grid measured in real time and the reference frequency (such as the average frequency value of the power grid). When the power grid frequency deviation is larger, the amplitude of the reactive disturbance current is increased to form positive feedback, accelerate the frequency offset, and thus detect the island state faster. The periodic reactive current disturbance strategy is to inject a reactive current of a fixed amplitude according to a certain period, such as every fixed period (preset duration), and measure the frequency fluctuation of the power grid at the grid connection point, and compare it with a given threshold to determine the possibility of the occurrence of the island effect. Among them, the fixed period can be set to 100ms, that is, every 100ms, the reactive disturbance mode is started to apply disturbance to the power grid to achieve a preliminary anti-island detection.

[0041] S102: In response to the disturbance of the reactive current disturbance signal, determine the instantaneous frequency value and the average frequency value of the power grid.

[0042] Here, the inverter can obtain the grid frequency through the connection port with the grid. Specifically, the instantaneous frequency value of the grid can be obtained once in each power frequency cycle, so as to calculate the average frequency value F of the grid within a certain period of time. avg The power frequency period is set according to the grid frequency. For example, if the grid frequency is 50 Hz, the power frequency period is 20 ms.

[0043] S103: In response to determining that the absolute difference between the instantaneous frequency value and the average frequency value is greater than or equal to a preset frequency fluctuation threshold, converting the reactive disturbance mode into a frequency disturbance mode.

[0044] In a specific implementation, after the disturbance is applied to the power grid by using a reactive disturbance method, the risk of the islanding effect can be preliminarily determined by judging whether the absolute difference between the instantaneous frequency value of the power grid after the disturbance and the average frequency value of the power grid is greater than or equal to the preset frequency fluctuation threshold. That is, when it is detected that the instantaneous frequency value of the power grid after the disturbance deviates from the average frequency value of the power grid by a certain amplitude, it indicates that there is a possibility of an islanding effect at present, and the reactive disturbance method can be switched to the frequency disturbance method to further perform anti-islanding detection to improve the accuracy of islanding effect detection. Among them, the preset frequency fluctuation threshold can be set according to the power grid operation requirements, inverter performance, islanding detection requirements, etc., for example, it is set to 0.1Hz.

[0045] It should be noted that the embodiment of the present application first uses a reactive disturbance method to apply a disturbance signal to the power grid, and when it is determined that there is a risk of an islanding effect, the reactive disturbance method is switched to a frequency disturbance method. Compared with the direct use of the frequency disturbance method in the related art, the frequency of use of the frequency disturbance method can be greatly reduced, and the impact of direct and frequent frequency disturbances on the output power quality (such as current quality) can be greatly reduced, which can reduce the distortion of the output current waveform caused by active anti-islanding detection.

[0046] In addition, compared with the active disturbance method (i.e., increasing active power method) in the traditional active detection method, the embodiment of the present application adopts an anti-island detection method that combines a reactive disturbance method with a fixed period and a smaller preset reactive current value with a frequency disturbance method with a changed disturbance direction. When the inverter is already operating at maximum power, the active power cannot be increased as required, resulting in the problem of a detection blind spot.

[0047] S104: In response to determining that the disturbance mode of the power grid is the frequency disturbance mode, applying a frequency disturbance signal of a first preset frequency value to the power grid in sequence at least three times for disturbance, and judging whether an islanding effect occurs according to the disturbance result of the frequency disturbance signal.

[0048] The disturbance directions of the frequency disturbance signals of the at least three first preset frequency values ​​include at least a first disturbance direction and a second disturbance direction, and the first disturbance direction and the second disturbance direction are opposite to each other.

[0049] In a specific implementation, after determining that the reactive disturbance mode is switched to the frequency disturbance mode, a frequency disturbance signal of a first preset frequency value with a smaller first disturbance direction can be applied to the power grid first. If the use conditions of the frequency disturbance mode are still met after application, a frequency disturbance signal of a first preset frequency value with a second disturbance direction opposite to the first disturbance direction is applied to the power grid again. At this time, the frequency values ​​of the two disturbance directions cancel each other out, and the overall frequency disturbance value applied to the power grid actually becomes 0; further, if the use conditions of the frequency disturbance mode are still met at this time, a frequency disturbance signal of a first preset frequency value with a smaller first disturbance direction can be applied to the power grid again. In this way, the frequency disturbance signal is continuously applied to the power grid until the island effect can be judged according to the frequency disturbance result and the disturbance signal is stopped from being applied to the power grid. In other words, it is necessary to apply frequency disturbance signals of the first preset frequency value of the first disturbance direction, the second disturbance direction, and the first disturbance direction to the power grid before the island effect can be judged.

[0050] Here, in practical applications, the first preset frequency value is usually set to a smaller value to avoid distortion of the current waveform output by the inverter, that is, to reduce the impact of anti-islanding detection on the quality of the inverter output current. In this way, it may be necessary to apply frequency disturbances to the power grid more times, not limited to applying three disturbance signals of the first disturbance direction, the second disturbance direction, and the first preset frequency value of the first disturbance direction to the power grid, until it is possible to determine whether an islanding effect occurs based on the result of the frequency disturbance signal disturbance.

[0051] Among them, the frequency disturbance result is, for example, whether the instantaneous frequency value of the power grid after the disturbance triggers the anti-islanding overfrequency protection shutdown result, such as whether the instantaneous frequency value of the power grid after the disturbance is applied is greater than the preset overfrequency protection threshold, to determine whether an islanding effect occurs.

[0052] Here, taking the first disturbance direction as a positive disturbance and the second disturbance direction as a negative disturbance as an example, the embodiment of the present application can implement the detection function of a small frequency increase, decrease, and increase by applying a small positive frequency disturbance w1, a small negative frequency disturbance -w1, and then applying a small positive frequency disturbance w1, thereby avoiding the occurrence of false detection due to the fact that the fluctuation direction of the grid frequency is consistent with the frequency disturbance direction of the inverter, that is, the accuracy of anti-islanding detection can be improved. In addition, since the frequency disturbance signal applied to the grid is small, and the disturbance directions of the two disturbances are different, the impact on the quality of the inverter output power can be reduced.

[0053] Here, the use condition of the frequency disturbance mode refers to the frequency change in the same direction when a frequency disturbance signal is applied to the power grid, that is, when a positive frequency disturbance signal is applied, the instantaneous frequency value of the power grid increases; when a negative frequency disturbance signal is applied, the instantaneous frequency value of the power grid decreases; in addition, the frequency change value of the power grid before and after the disturbance signal is not within the preset error range, that is, the frequency change value of the power grid exceeds the preset error range. If the above two conditions are met, it is considered that the use conditions are met, and it can be judged that there is a risk of islanding effect. The frequency disturbance can continue to be executed according to the frequency disturbance strategy until the islanding effect is detected.

[0054] The first preset frequency value is a smaller frequency value, and the first preset frequency value may be set by comprehensively considering various factors. For example, the first preset frequency value is set to 0.05 Hz.

[0055] In an embodiment of the present application, a reactive current disturbance signal is applied to the power grid by starting a reactive disturbance mode to disturb it, and when it is determined that the power grid frequency fluctuates, the reactive disturbance mode is converted into a frequency disturbance mode; further, a frequency disturbance signal of a first preset frequency value is applied to the power grid at least three times, and whether an islanding effect occurs is determined based on the result of the frequency disturbance signal disturbance; the disturbance direction of the at least three frequency disturbance signals includes at least a first disturbance direction and a second disturbance direction. In this way, the present application can improve the accuracy of anti-islanding detection while reducing the impact of anti-islanding detection on the output power quality of the inverter by adopting an anti-islanding detection method that combines reactive disturbance with frequency disturbance with a changed disturbance direction.

[0056] A possible implementation method of applying reactive disturbance to the power grid is described below. Here, a periodic reactive current disturbance strategy is used as an example. That is, the reactive disturbance method described in S101 is started to apply a reactive current disturbance signal to the power grid for disturbance, including the following steps: at preset time intervals, a reactive current disturbance signal with a preset reactive current value in a third disturbance direction and / or a fourth disturbance direction is applied to the power grid; wherein the third disturbance direction and the fourth disturbance direction are in opposite directions to each other.

[0057] In a specific implementation, a reactive disturbance mode can be started once every preset time (fixed period) to apply disturbance to the power grid. For example, the preset time is 100ms, and the reactive disturbance mode can be started once at 100ms, 200ms, 300ms, etc. Among them, starting a reactive disturbance mode can only include a disturbance in a certain disturbance direction, and starting a reactive disturbance mode can also include a disturbance in a first disturbance direction and a disturbance in a second disturbance direction.

[0058] In addition, during the process of applying a reactive disturbance mode to the power grid, if an event occurs that satisfies the reactive disturbance mode to be transformed into a frequency disturbance mode, the reactive disturbance mode is directly stopped and the frequency disturbance mode is directly entered. After a reactive disturbance mode is applied to the power grid once, if no event occurs that satisfies the reactive disturbance mode to be transformed into a frequency disturbance mode, the reactive disturbance mode is started at the moment of reaching a fixed period to apply a reactive current disturbance signal to the power grid for disturbance.

[0059] Among them, the preset reactive current value can be pre-set based on the capacity of the new energy power supply (such as the capacity of the photovoltaic system), the rated power of the inverter, the grid specifications and standards requirements, the optimization requirements of the detection blind area, etc. The preset reactive current value is usually small, for example, it can be about 0.5%-5% of the rated current of the inverter, such as set to 1%.

[0060] Further, a specific implementation method of applying a reactive disturbance mode to the power grid is described below, that is, a reactive disturbance mode including two disturbance directions of positive and negative disturbances is described for a single startup, and a reactive current disturbance signal of a preset reactive current value in a third disturbance direction and a fourth disturbance direction is applied to the power grid, comprising the following steps:

[0061] Step 1011: applying a reactive current disturbance signal of a preset reactive current value in a third disturbance direction to the power grid at a first preset time, and determining whether an absolute difference between an instantaneous frequency value and an average frequency value of the power grid at a second preset time after applying the reactive current disturbance signal of the preset reactive current value in the third disturbance direction is greater than or equal to the preset frequency fluctuation threshold;

[0062] Step 1012a: if the absolute difference between the instantaneous frequency value and the average frequency value of the power grid at the second preset moment is greater than or equal to the preset frequency fluctuation threshold, the reactive disturbance mode is converted into a frequency disturbance mode; or, step 1012b: if the absolute difference between the instantaneous frequency value and the average frequency value of the power grid at the second preset moment is less than the preset frequency fluctuation threshold, a reactive current disturbance signal of the preset reactive current value in the fourth disturbance direction is applied to the power grid at the third preset moment, and it is determined whether the absolute difference between the instantaneous frequency value and the average frequency value of the power grid at the fourth preset moment after the reactive current disturbance signal of the preset reactive current value in the fourth disturbance direction is greater than or equal to the preset frequency fluctuation threshold;

[0063] Step 1013a: If the absolute difference between the instantaneous frequency value and the average frequency value of the power grid at the fourth preset moment is greater than or equal to the preset frequency fluctuation threshold, the reactive disturbance mode is converted into the frequency disturbance mode; or, step 1013b: If the absolute difference between the instantaneous frequency value and the average frequency value of the power grid at the fourth preset moment is less than the preset frequency fluctuation threshold, jump to the operation of starting the reactive disturbance mode to apply a reactive current disturbance signal to the power grid for disturbance.

[0064] In a specific implementation, the reactive disturbance mode adopted in the embodiment of the present application can be to start the reactive disturbance mode once every fixed period, and each start-up of the reactive disturbance mode can include two stages. The two stages apply reactive current signals of different disturbance directions to the power grid to perform preliminary anti-islanding detection. Specifically, the first stage is to apply a reactive current disturbance signal of a preset reactive current value in a third disturbance direction to the power grid at a first preset time, and the second stage is to apply a reactive current disturbance signal of a preset reactive current value in a fourth disturbance direction to the power grid at a third preset time. If the instantaneous frequency value of the power grid does not deviate from the average frequency of the power grid by a certain amplitude in the two stages of starting the reactive disturbance mode (the absolute difference between the instantaneous frequency value of the power grid and the average frequency value of the power grid is less than the preset frequency fluctuation threshold), it means that the reactive disturbance did not detect the possibility of the islanding effect, then the time is reset by a timer or a counter, and when the next fixed cycle is reached, the reactive disturbance mode is restarted to continue the detection; if the instantaneous frequency value of the power grid deviates from the average frequency of the power grid by a certain amplitude in any stage of starting the reactive disturbance mode, it means that the reactive disturbance detected the possibility of the islanding effect, then the reactive disturbance mode is directly switched to the frequency disturbance mode for further anti-islanding detection to improve the accuracy of the detection.

[0065] Specifically, when starting the reactive disturbance mode, firstly, at the first preset time t1, a reactive current disturbance signal of a third disturbance direction is applied to the power grid, and at the second preset time t2, it is judged whether the instantaneous frequency value of the power grid at this time deviates from the average frequency value of the power grid by a certain amplitude; if so, the reactive disturbance mode is directly switched to the frequency disturbance mode; if not, at the third preset time t3, a reactive current disturbance signal of a fourth disturbance direction is applied to the power grid, and at the fourth preset time t4, it is judged whether the instantaneous frequency value of the power grid at this time deviates from the average frequency value of the power grid by a certain amplitude; if so, the reactive disturbance mode is directly switched to the frequency disturbance mode; if not, jump to the operation of starting the reactive disturbance mode to apply the reactive current disturbance signal to the power grid for disturbance.

[0066] Among them, the time sequence of the first preset moment, the second preset moment, the third preset moment, and the fourth preset moment is the first preset moment t1 < the second preset moment t2 < the third preset moment t3 < the fourth preset moment t4, and the time interval between the first preset moment, the second preset moment, the third preset moment, and the fourth preset moment can be set to a power frequency cycle T, that is, t2 = t1 + T, t3 = t1 + 2T, t4 = t1 + 3T. The preset frequency fluctuation threshold can be set according to the power grid fluctuation regulations, for example, set to 0.1Hz.

[0067] A possible implementation method of applying a frequency disturbance mode to a power grid is specifically described below, that is, in response to determining that the disturbance mode of the power grid is the frequency disturbance mode in S104, a frequency disturbance signal of a first preset frequency value is sequentially applied to the power grid for at least three times to perform disturbance, and whether an islanding effect occurs is determined according to the result of the disturbance of the frequency disturbance signal, including the following steps:

[0068] Step 1041: applying a frequency disturbance signal of a first preset frequency value in the first disturbance direction to the power grid, and determining whether a frequency change value of the power grid is within a preset error range before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied;

[0069] Step 1042a: if the frequency change value of the power grid before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied is within the preset error range, jump to the operation of starting the reactive disturbance mode to apply a reactive current disturbance signal to the power grid for disturbance; or, step 1042b: if the frequency change value of the power grid before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is not within the preset error range, apply the frequency disturbance signal of the first preset frequency value in the second disturbance direction to the power grid, and determine whether the frequency change value of the power grid before and after the frequency disturbance signal of the first preset frequency value in the second disturbance direction is within the preset error range;

[0070] Step 1043a: If the frequency change value of the power grid before and after the frequency disturbance signal of the first preset frequency value in the second disturbance direction is applied is not within the preset error range, then the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied to the power grid again, and whether an islanding effect occurs is determined based on the result of the disturbance of the frequency disturbance signal; or, step 1043b: If the frequency change value of the power grid before and after the frequency disturbance signal of the first preset frequency value in the second disturbance direction is applied is within the preset error range, jump to execute the operation of starting the reactive disturbance mode to apply a reactive current disturbance signal to the power grid for disturbance.

[0071] In a specific implementation, after switching from the reactive disturbance mode to the frequency disturbance mode, a frequency disturbance signal of a first preset frequency value can be applied to the power grid first, and it can be applied in the first disturbance direction, the second disturbance direction, and the first disturbance direction. Specifically, if before and after applying a frequency disturbance in a certain disturbance direction at any time, it is detected that the frequency change value of the power grid is not within the preset error range, then the frequency disturbance in the opposite disturbance direction is entered. At this time, it indicates that there is a risk of islanding effect, and the frequency disturbance can be continued to further monitor whether the islanding effect actually occurs; if before and after applying a frequency disturbance in a certain disturbance direction at any time, it is detected that the instantaneous frequency value of the power grid has not changed, or the frequency change value of the power grid is within the preset error range, then jump to the reactive disturbance link. At this time, it indicates that there is no risk of islanding effect at present, and the conventional monitoring of islanding effect can be continued.

[0072] In a possible implementation manner, the step of applying a frequency disturbance signal of a first preset frequency value in the first disturbance direction to the power grid again, and judging whether an islanding effect occurs according to a disturbance result of the frequency disturbance signal, comprises the following steps:

[0073] Step (1): applying a frequency disturbance signal of a first preset frequency value in the first disturbance direction to the power grid again, and determining whether a frequency change value of the power grid is within a preset error range before and after applying the frequency disturbance signal of the first preset frequency value in the first disturbance direction;

[0074] Step (2): if the power grid frequency change value before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied again is not within the preset error range, then a frequency disturbance signal of a second preset frequency value in the first disturbance direction is applied to the power grid, and it is determined whether the power grid frequency change value before and after the frequency disturbance signal of the second preset frequency value in the first disturbance direction is applied is within the preset error range; the second preset frequency value is greater than the first preset frequency value;

[0075] Step (3): if the power grid frequency change value before and after the frequency disturbance signal of the second preset frequency value in the first disturbance direction is applied is not within the preset error range, then a frequency disturbance signal of a third preset frequency value in the first disturbance direction is applied to the power grid, and it is determined whether the power grid frequency change value before and after the frequency disturbance signal of the third preset frequency value in the first disturbance direction is within the preset error range; the third preset frequency value is greater than the second preset frequency value;

[0076] Step (4): If the frequency change value of the power grid before and after the frequency disturbance signal of the third preset frequency value in the first disturbance direction is applied is not within the preset error range, continue to apply the disturbance signal to the power grid according to the positive feedback frequency disturbance strategy until the instantaneous frequency value of the power grid is monitored to be greater than the preset overfrequency protection threshold, and determine that an islanding effect occurs.

[0077] In the specific implementation, for the frequency disturbance mode, the present application sets two stages, and the disturbance control strategies adopted in different stages are different. Specifically, in the first stage, a fixed frequency disturbance strategy is adopted, which refers to the use of a fixed disturbance frequency and the application of frequency disturbance to the power grid according to different disturbance direction changes. Specifically, at least the first disturbance direction, the second disturbance direction, and the frequency disturbance signal of the first preset frequency value of the first disturbance direction are applied to the power grid in sequence. If the power grid frequency change value exceeds the preset error range during the first stage, the second stage is entered; if the power grid frequency change value does not exceed the preset error range during the first stage, the working link of the reactive disturbance mode is jumped to. In the second stage, a positive feedback frequency disturbance strategy is adopted. The positive feedback frequency disturbance strategy refers to applying frequency disturbance to the power grid with continuously increasing frequency and in the same disturbance direction. Specifically, frequency disturbance signals of at least a first preset frequency value, a second preset frequency value, and a third preset frequency value in a first disturbance direction are applied to the power grid in sequence. If the frequency change value of the power grid before and after the disturbance signal is applied to the power grid exceeds the preset error range, the disturbance signal is continued to be applied to the power grid according to the positive feedback frequency disturbance strategy until the instantaneous frequency value of the power grid is monitored to be greater than the preset overfrequency protection threshold. Then, the frequency disturbance signal is stopped being applied to the power grid, and it is determined that an islanding effect occurs.

[0078] In this way, the embodiment of the present application adopts a combination of a fixed frequency disturbance strategy and a positive feedback frequency disturbance strategy in the frequency disturbance link. On the one hand, a fixed frequency disturbance strategy with a changed disturbance direction of a smaller first preset frequency value is adopted to reduce the impact on the output current of the inverter; on the other hand, when it is determined through the first stage that there is a risk of islanding effect, a positive feedback frequency disturbance strategy of a disturbance signal with a continuously increasing frequency in the same disturbance direction is adopted. The disturbance amount can be gradually increased through rapid frequency feedback to achieve a rapid islanding detection function, so as to meet the time limit requirement of anti-islanding detection.

[0079] It can be understood that the second stage of the frequency disturbance method adopts the direction of increasing the frequency, which can effectively shorten the anti-islanding detection time. As the frequency increases, the cycle time becomes shorter and the passive anti-islanding protection time is triggered faster.

[0080] Among them, the preset error range is used in the anti-islanding detection scenario as an indicator to measure the accuracy of frequency changes. It represents a frequency error range that is defined as smaller, and is used to determine whether the actual measured frequency change is within an acceptable small error range. For example, in the frequency monitoring of a power system, if the normal grid frequency is 50Hz, the preset error range can be set to ±0.05Hz, which means that as long as the measured frequency change is within the range of 50Hz±0.05Hz, the frequency change can be considered to be a normal fluctuation within the allowable error range.

[0081] In a possible implementation, for the positive feedback frequency disturbance strategy, there may be a fixed relationship between the preset frequency values ​​applied to the power grid twice. Here, the latter preset frequency value is required to be greater than the previous preset frequency value, and the latter preset frequency value is calculated based on the previous preset frequency value. Specifically, the second preset frequency value is determined according to the following steps: the adjustment coefficient is multiplied by the grid frequency change value before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied to obtain a first value; the adjustment coefficient is determined based on the anti-island detection duration threshold; the first value is added to the first preset frequency value to obtain a second value, and the second value is determined as the second preset frequency value.

[0082] In a specific implementation, each time a frequency disturbance is performed in the second stage of the frequency disturbance mode, the frequency of the disturbance is increased compared to the previous disturbance. Specifically, the preset frequency value of the next frequency disturbance = the previous preset frequency value + the grid frequency change value × the adjustment coefficient. The adjustment coefficient is the disturbance increase coefficient for adjusting each frequency increment, which can be set according to the anti-islanding detection time requirement.

[0083] In one example, the second preset frequency value = the first preset frequency value + the first frequency change value × the adjustment coefficient, wherein the first frequency change value is the grid frequency change value before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied; in one example, the third preset frequency value = the second preset frequency value + the second frequency change value × the adjustment coefficient, wherein the second frequency change value is the grid frequency change value before and after the frequency disturbance signal of the second preset frequency value in the first disturbance direction is applied.

[0084] Exemplarily, a specific anti-islanding detection method provided in an embodiment of the present application is described below. Figure 2 FIG. 1 is a flowchart of an anti-islanding detection method provided by a specific embodiment of the present application; Figure 2 As shown, the anti-island detection method includes the following steps:

[0085] S201: Start the reactive disturbance mode and apply reactive current +i to the grid at time t1 qin;

[0086] S202: Determine the instantaneous frequency value F1 and the average frequency value F1 of the power grid at time t2 avg Is the absolute difference between them greater than 0.1Hz? If so, switch the reactive disturbance mode to the frequency disturbance mode and jump to S205;

[0087] S203: If not, apply -i to the grid at time t3 qin ;

[0088] S204: Determine the instantaneous frequency value F2 of the power grid at time t4 and the average frequency value F avg Is the absolute difference between them greater than 0.1Hz? If not, jump to S201;

[0089] S205: If yes, apply a frequency disturbance w1 to the power grid, and determine whether the power grid frequency change value before and after the frequency disturbance is applied is within a preset error range; if yes, jump to S201;

[0090] S206: If not, apply a frequency disturbance -w1 to the power grid, and determine whether the power grid frequency change value before and after the frequency disturbance is applied is within a preset error range; if so, jump to S201;

[0091] S207: If not, apply a positive frequency disturbance w1 to the power grid, and determine whether the power grid frequency change value before and after the frequency disturbance is applied is within a preset error range; if so, jump to S201;

[0092] S208: If not, apply a positive frequency disturbance w2 to the power grid, and determine whether the power grid frequency change value before and after the frequency disturbance is applied is within a preset error range; if so, jump to S201;

[0093] S209: If not, apply a positive frequency disturbance w3 to the power grid, and determine whether the power grid frequency change value before and after the frequency disturbance is applied is within the preset error range; if not, continue to apply the disturbance signal to the power grid according to the positive feedback frequency disturbance strategy until the instantaneous frequency value of the power grid is monitored to be greater than the preset overfrequency protection threshold, and determine that an islanding effect occurs.

[0094] Among them, w3>w2>w1.

[0095] In this specific embodiment, two disturbance modes are adopted, including a reactive disturbance mode and a frequency disturbance mode. Specifically, the reactive disturbance mode may include a positive reactive current disturbance and a negative reactive current disturbance. The frequency disturbance mode may include two stages, one stage adopting a fixed frequency disturbance strategy, and one stage adopting a positive feedback frequency disturbance strategy. Among them, the fixed frequency disturbance strategy includes positive frequency disturbance w1, negative frequency disturbance -w1, and positive frequency disturbance w1; the positive feedback frequency disturbance strategy includes at least positive frequency disturbance w1, positive frequency disturbance w2, and positive frequency disturbance w3.

[0096] In this way, the influence of frequent frequency disturbances on the output current quality can be avoided through fixed-cycle reactive power detection; by applying a smaller positive frequency disturbance w1, a smaller negative frequency disturbance -w1, and then a smaller positive frequency disturbance w1, the detection function of a smaller frequency increase, decrease, and increase is realized, avoiding the false detection when the grid frequency increases or decreases in the same direction as the inverter frequency offset. In addition, by gradually increasing the disturbance amount through fast frequency positive feedback, a fast island detection function can be realized, which can meet the prescribed anti-island detection limit time requirements.

[0097] Based on the same inventive concept, an anti-island detection device corresponding to the anti-island detection method provided in the above embodiment is also provided in the embodiment of the present application. Since the principle of solving the problem by the device in the embodiment of the present application is similar to the anti-island detection method in the above embodiment of the present application, the implementation of the device can refer to the implementation of the method, and the repeated parts will not be repeated.

[0098] like Figure 3 , Figure 4 As shown, Figure 3 One of the structural schematic diagrams of an anti-islanding detection device 300 provided in an embodiment of the present application is shown; Figure 4 FIG. 2 shows a second structural diagram of an anti-islanding detection device 300 provided in an embodiment of the present application. Figure 3 As shown, the anti-islanding detection device 300 includes:

[0099] The reactive disturbance module 310 is used to start the reactive disturbance mode to apply a reactive current disturbance signal to the power grid for disturbance;

[0100] A frequency fluctuation determination module 320, configured to determine an instantaneous frequency value and an average frequency value of the power grid in response to a disturbance of the reactive current disturbance signal;

[0101] a disturbance mode switching module 330, configured to transform the reactive disturbance mode into a frequency disturbance mode in response to determining that the absolute difference between the instantaneous frequency value and the average frequency value is greater than or equal to a preset frequency fluctuation threshold;

[0102] A frequency disturbance module 340 is used for, in response to determining that the disturbance mode of the power grid is the frequency disturbance mode, applying a frequency disturbance signal of a first preset frequency value to the power grid at least three times in sequence to perform disturbance, and judging whether an islanding effect occurs according to a result of the disturbance of the frequency disturbance signal;

[0103] The disturbance directions of the frequency disturbance signals of the at least three first preset frequency values ​​include at least a first disturbance direction and a second disturbance direction, and the first disturbance direction and the second disturbance direction are opposite to each other.

[0104] In a possible implementation, Figure 3 As shown, the reactive disturbance module 310 is specifically used to: apply a reactive current disturbance signal of a preset reactive current value in a third disturbance direction and / or a fourth disturbance direction to the power grid at preset time intervals; wherein the third disturbance direction and the fourth disturbance direction are opposite directions to each other.

[0105] In a possible implementation, Figure 4 As shown, the reactive disturbance module 310 includes:

[0106] The first judgment unit 311 is used to apply a reactive current disturbance signal of a preset reactive current value in a third disturbance direction to the power grid at a first preset time, and to determine whether the absolute difference between the instantaneous frequency value and the average frequency value of the power grid at a second preset time after the reactive current disturbance signal of the preset reactive current value in the third disturbance direction is applied is greater than or equal to the preset frequency fluctuation threshold.

[0107] The second judgment unit 312 is used to apply a reactive current disturbance signal of the preset reactive current value in a fourth disturbance direction to the power grid at a third preset time if the absolute difference between the instantaneous frequency value and the average frequency value of the power grid at the second preset moment is less than the preset frequency fluctuation threshold, and to judge whether the absolute difference between the instantaneous frequency value and the average frequency value of the power grid at the fourth preset moment after applying the reactive current disturbance signal of the preset reactive current value in the fourth disturbance direction is greater than or equal to the preset frequency fluctuation threshold.

[0108] The jump unit 313 is used to jump to the operation of starting the reactive disturbance mode to apply a reactive current disturbance signal to the grid for disturbance if the absolute difference between the instantaneous frequency value and the average frequency value of the grid at the fourth preset moment is less than the preset frequency fluctuation threshold.

[0109] In a possible implementation, Figure 4 As shown, the frequency disturbance module 340 includes:

[0110] The third judgment unit 341 is used to apply a frequency disturbance signal of a first preset frequency value in the first disturbance direction to the power grid, and judge whether the power grid frequency change value is within a preset error range before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied;

[0111] The fourth judgment unit 342 is used to apply a frequency disturbance signal of the first preset frequency value in the second disturbance direction to the power grid if the power grid frequency change value before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied is not within a preset error range, and judge whether the power grid frequency change value before and after the frequency disturbance signal of the first preset frequency value in the second disturbance direction is within a preset error range;

[0112] The fifth judgment unit 343 is used to apply the frequency disturbance signal of the first preset frequency value in the first disturbance direction to the power grid again if the grid frequency change value before and after the frequency disturbance signal of the first preset frequency value in the second disturbance direction is applied is not within a preset error range, and judge whether an islanding effect occurs based on the result of the disturbance of the frequency disturbance signal.

[0113] In a possible implementation, Figure 4 As shown, the fifth judgment unit 343 is specifically used for:

[0114] Applying a frequency disturbance signal of a first preset frequency value in the first disturbance direction to the power grid again, and determining whether a frequency change value of the power grid before and after applying the frequency disturbance signal of the first preset frequency value in the first disturbance direction is within a preset error range;

[0115] If the frequency change value of the power grid before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied again is not within the preset error range, a frequency disturbance signal of a second preset frequency value in the first disturbance direction is applied to the power grid, and it is determined whether the frequency change value of the power grid before and after the frequency disturbance signal of the second preset frequency value in the first disturbance direction is within the preset error range; the second preset frequency value is greater than the first preset frequency value;

[0116] If the frequency change value of the power grid before and after the frequency disturbance signal of the second preset frequency value of the first disturbance direction is applied is not within the preset error range, a frequency disturbance signal of a third preset frequency value of the first disturbance direction is applied to the power grid, and it is determined whether the frequency change value of the power grid before and after the frequency disturbance signal of the third preset frequency value of the first disturbance direction is within the preset error range; the third preset frequency value is greater than the second preset frequency value;

[0117] If the frequency change value of the power grid before and after the frequency disturbance signal of the third preset frequency value in the first disturbance direction is applied is not within the preset error range, the disturbance signal continues to be applied to the power grid according to the positive feedback frequency disturbance strategy until the instantaneous frequency value of the power grid is monitored to be greater than the preset overfrequency protection threshold, and it is determined that an island effect occurs.

[0118] In a possible implementation, Figure 4 As shown, the fifth determination unit 343 is specifically configured to determine the second preset frequency value according to the following steps:

[0119] Multiplying the adjustment coefficient by the grid frequency change value before and after applying the frequency disturbance signal of the first preset frequency value in the first disturbance direction to obtain a first value; the adjustment coefficient is determined based on the anti-islanding detection duration threshold;

[0120] The first value is added to the first preset frequency value to obtain a second value, and the second value is determined as the second preset frequency value.

[0121] In a possible implementation, Figure 4 As shown, the frequency disturbance module 340 is also used to jump to the operation of starting the reactive disturbance mode to apply a reactive current disturbance signal to the power grid for disturbance if the power grid frequency change value before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied is within the preset error range, or if the power grid frequency change value before and after the frequency disturbance signal of the first preset frequency value in the second disturbance direction is applied is within the preset error range.

[0122] In an embodiment of the present application, a reactive current disturbance signal is applied to the power grid by starting a reactive disturbance mode, and when it is determined that the power grid frequency fluctuates, the reactive disturbance mode is converted into a frequency disturbance mode; further, a frequency disturbance signal of a first preset frequency value is applied to the power grid at least three times, and whether an islanding effect occurs is determined based on the result of the frequency disturbance signal disturbance; the disturbance direction of the at least three frequency disturbance signals includes at least a first disturbance direction and a second disturbance direction. In this way, the present application can improve the accuracy of anti-islanding detection while reducing the impact of disturbance on the output power quality of the inverter by adopting an anti-islanding detection method that combines reactive disturbance with frequency disturbance with a changed disturbance direction.

[0123] Based on the same inventive concept, see Figure 5As shown, it is a structural diagram of an electronic device 500 provided in an embodiment of the present application, including: a processor 510, a memory 520 and a bus 530, the memory 520 stores machine-readable instructions executable by the processor 510, when the electronic device 500 is running, the processor 510 and the memory 520 communicate through the bus 530, and the machine-readable instructions are executed by the processor 510 when running to perform the steps of the anti-island detection method as described in any of the above embodiments.

[0124] Specifically, when the machine-readable instruction is executed by the processor 510, the following processing may be performed:

[0125] Start the reactive disturbance mode to apply reactive current disturbance signal to the power grid for disturbance;

[0126] In response to the disturbance of the reactive current disturbance signal, determining an instantaneous frequency value and an average frequency value of the power grid;

[0127] In response to determining that an absolute difference between the instantaneous frequency value and the average frequency value is greater than or equal to a preset frequency fluctuation threshold, converting the reactive disturbance mode into a frequency disturbance mode;

[0128] In response to determining that the disturbance mode of the power grid is the frequency disturbance mode, applying a frequency disturbance signal of a first preset frequency value to the power grid at least three times in sequence to disturb the power grid, and judging whether an islanding effect occurs according to a result of the disturbance of the frequency disturbance signal;

[0129] The disturbance directions of the frequency disturbance signals of the at least three first preset frequency values ​​include at least a first disturbance direction and a second disturbance direction, and the first disturbance direction and the second disturbance direction are opposite to each other.

[0130] Based on the same inventive concept, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the anti-islanding detection method provided in the above embodiment are executed.

[0131] Specifically, the storage medium can be a general storage medium, such as a mobile disk, a hard disk, etc. When the computer program on the storage medium is run, the above-mentioned anti-islanding detection method can be executed. By adopting an anti-islanding detection method that combines reactive disturbance with frequency disturbance with a changed disturbance direction, the accuracy of anti-islanding detection can be improved while reducing the impact of the disturbance on the output power quality of the inverter.

[0132] In the embodiment of the present application, the computer program can also execute other machine-readable instructions when run by the processor to execute other methods described in the embodiment. For the specific execution method steps and principles, please refer to the description of the embodiment, which will not be repeated here.

[0133] The computer program product for performing anti-islanding detection provided in the embodiments of the present application includes a computer-readable storage medium storing program code. The instructions included in the program code can be used to execute the methods described in the previous method embodiments. The specific implementation can be found in the method embodiments, which will not be repeated here.

[0134] The device for anti-islanding detection provided in the embodiment of the present application can be specific hardware on the device or software or firmware installed on the device. The device provided in the embodiment of the present application, its implementation principle and the technical effect produced are the same as those in the aforementioned method embodiment. For the sake of brief description, for the parts not mentioned in the device embodiment, reference can be made to the corresponding contents in the aforementioned method embodiment. Technical personnel in the relevant field can clearly understand that for the convenience and conciseness of description, the specific working processes of the systems, devices and units described above can all refer to the corresponding processes in the aforementioned method embodiment, and will not be repeated here.

[0135] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0136] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0137] In addition, each functional unit in the embodiments provided in the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0138] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0139] It should be noted that similar numbers and letters represent similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description and are not to be understood as indicating or implying relative importance.

[0140] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present application, which are used to illustrate the technical solutions of the present application, rather than to limit them. The protection scope of the present application is not limited thereto. Although the present application is described in detail with reference to the above-mentioned embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-mentioned embodiments within the technical scope disclosed in the present application, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application. They should all be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. An anti-islanding detection method, characterized in that: The method comprises: Start the reactive disturbance mode to apply reactive current disturbance signal to the power grid for disturbance; In response to the disturbance of the reactive current disturbance signal, determining an instantaneous frequency value and an average frequency value of the power grid; In response to determining that an absolute difference between the instantaneous frequency value and the average frequency value is greater than or equal to a preset frequency fluctuation threshold, converting the reactive disturbance mode into a frequency disturbance mode; In response to determining that the disturbance mode of the power grid is the frequency disturbance mode, applying a frequency disturbance signal of a first preset frequency value to the power grid at least three times in sequence to disturb the power grid, and judging whether an islanding effect occurs according to a result of the disturbance of the frequency disturbance signal; The disturbance directions of the frequency disturbance signals of the at least three first preset frequency values ​​include at least a first disturbance direction and a second disturbance direction, and the first disturbance direction and the second disturbance direction are opposite to each other.

2. The method according to claim 1, characterized in that The method of starting the reactive disturbance mode to apply a reactive current disturbance signal to the power grid for disturbance includes: At preset time intervals, a reactive current disturbance signal of a preset reactive current value in a third disturbance direction and / or a fourth disturbance direction is applied to the power grid; wherein the third disturbance direction and the fourth disturbance direction are opposite directions to each other.

3. The method according to claim 2, characterized in that The method of applying a reactive current disturbance signal of preset reactive current values ​​in a third disturbance direction and a fourth disturbance direction to the power grid includes: Applying a reactive current disturbance signal of a preset reactive current value in a third disturbance direction to the power grid at a first preset time, and determining whether an absolute difference between an instantaneous frequency value and an average frequency value of the power grid at a second preset time after applying the reactive current disturbance signal of the preset reactive current value in the third disturbance direction is greater than or equal to the preset frequency fluctuation threshold; If the absolute difference between the instantaneous frequency value and the average frequency value of the power grid at the second preset moment is less than the preset frequency fluctuation threshold, a reactive current disturbance signal of the preset reactive current value in the fourth disturbance direction is applied to the power grid at the third preset moment, and it is determined whether the absolute difference between the instantaneous frequency value and the average frequency value of the power grid at the fourth preset moment after the reactive current disturbance signal of the preset reactive current value in the fourth disturbance direction is applied is greater than or equal to the preset frequency fluctuation threshold; If the absolute difference between the instantaneous frequency value and the average frequency value of the power grid at the fourth preset moment is less than the preset frequency fluctuation threshold, the process jumps to executing the operation of starting the reactive disturbance mode to apply a reactive current disturbance signal to the power grid for disturbance.

4. The method according to claim 1, characterized in that: In response to determining that the disturbance mode of the power grid is the frequency disturbance mode, applying a frequency disturbance signal of a first preset frequency value to the power grid at least three times in sequence to disturb the power grid, and judging whether an islanding effect occurs according to a result of the disturbance of the frequency disturbance signal, including: Applying a frequency disturbance signal of a first preset frequency value in the first disturbance direction to the power grid, and determining whether a frequency change value of the power grid is within a preset error range before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied; If the frequency change value of the power grid before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied is not within the preset error range, then the frequency disturbance signal of the first preset frequency value in the second disturbance direction is applied to the power grid, and it is determined whether the frequency change value of the power grid before and after the frequency disturbance signal of the first preset frequency value in the second disturbance direction is within the preset error range; If the grid frequency change value before and after the frequency disturbance signal of the first preset frequency value in the second disturbance direction is applied is not within the preset error range, the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied to the grid again, and whether an islanding effect occurs is determined based on the result of the frequency disturbance signal disturbance.

5. The method according to claim 4, characterized in that The step of applying a frequency disturbance signal of a first preset frequency value in the first disturbance direction to the power grid again, and judging whether an islanding effect occurs according to a disturbance result of the frequency disturbance signal, comprises: Applying a frequency disturbance signal of a first preset frequency value in the first disturbance direction to the power grid again, and determining whether a frequency change value of the power grid before and after applying the frequency disturbance signal of the first preset frequency value in the first disturbance direction is within a preset error range; If the frequency change value of the power grid before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied again is not within the preset error range, a frequency disturbance signal of a second preset frequency value in the first disturbance direction is applied to the power grid, and it is determined whether the frequency change value of the power grid before and after the frequency disturbance signal of the second preset frequency value in the first disturbance direction is within the preset error range; the second preset frequency value is greater than the first preset frequency value; If the frequency change value of the power grid before and after the frequency disturbance signal of the second preset frequency value of the first disturbance direction is applied is not within the preset error range, a frequency disturbance signal of a third preset frequency value of the first disturbance direction is applied to the power grid, and it is determined whether the frequency change value of the power grid before and after the frequency disturbance signal of the third preset frequency value of the first disturbance direction is within the preset error range; the third preset frequency value is greater than the second preset frequency value; If the frequency change value of the power grid before and after the frequency disturbance signal of the third preset frequency value in the first disturbance direction is applied is not within the preset error range, the disturbance signal continues to be applied to the power grid according to the positive feedback frequency disturbance strategy until the instantaneous frequency value of the power grid is monitored to be greater than the preset overfrequency protection threshold, and it is determined that an island effect occurs.

6. The method according to claim 5, characterized in that The second preset frequency value is determined according to the following steps: Multiplying the adjustment coefficient by the grid frequency change value before and after applying the frequency disturbance signal of the first preset frequency value in the first disturbance direction to obtain a first value; the adjustment coefficient is determined based on the anti-islanding detection duration threshold; The first value is added to the first preset frequency value to obtain a second value, and the second value is determined as the second preset frequency value.

7. The method according to claim 4, characterized in that The method further comprises: If the grid frequency change value before and after the frequency disturbance signal of the first preset frequency value in the first disturbance direction is applied is within the preset error range, or if the grid frequency change value before and after the frequency disturbance signal of the first preset frequency value in the second disturbance direction is applied is within the preset error range, then jump to execute the operation of starting the reactive disturbance mode to apply a reactive current disturbance signal to the grid for disturbance.

8. An anti-islanding detection device, characterized in that: The device comprises: The reactive disturbance module is used to start the reactive disturbance mode to apply a reactive current disturbance signal to the power grid for disturbance; A frequency fluctuation determination module, configured to determine an instantaneous frequency value and an average frequency value of the power grid in response to a disturbance of the reactive current disturbance signal; a disturbance mode switching module, configured to transform the reactive disturbance mode into a frequency disturbance mode in response to determining that the absolute difference between the instantaneous frequency value and the average frequency value is greater than or equal to a preset frequency fluctuation threshold; a frequency disturbance module, configured to, in response to determining that the disturbance mode of the power grid is the frequency disturbance mode, sequentially apply a frequency disturbance signal of a first preset frequency value to the power grid for at least three times to perform disturbance, and determine whether an islanding effect occurs according to a result of the disturbance of the frequency disturbance signal; The disturbance directions of the frequency disturbance signals of the at least three first preset frequency values ​​include at least a first disturbance direction and a second disturbance direction, and the first disturbance direction and the second disturbance direction are opposite to each other.

9. An electronic device, characterized in that: include: A processor, a memory and a bus, wherein the memory stores machine-readable instructions executable by the processor, and when the electronic device is running, the processor and the memory communicate through the bus, and the machine-readable instructions are executed by the processor to execute the steps of the anti-islanding detection method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the anti-islanding detection method according to any one of claims 1 to 7 are executed.

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