Single-phase photovoltaic inverter island detection method and equipment, photovoltaic system

Abstract

The present invention provides a single-phase photovoltaic inverter islanding detection method and device, as well as a photovoltaic system. The method includes: obtaining a target grid-connected voltage and a sampling frequency corresponding to the target grid-connected voltage, and determining a reactive voltage component corresponding to the target grid-connected voltage based on the target grid-connected voltage and the sampling frequency; extracting harmonics of a preset frequency from the reactive voltage component, and generating a reactive disturbance value based on the harmonics of the preset frequency; superimposing the reactive disturbance value on a reactive current set value in a target control loop, and adjusting the output of a current controller in the target control loop based on a phase angle corresponding to the target grid-connected voltage; and, in response to an internal / external islanding detection trigger signal, obtaining a reactive voltage component after phase-locking the current target grid-connected voltage, and determining whether an islanding effect exists based on the harmonics of the preset frequency contained in the current reactive voltage component. The present invention can effectively improve the reliability of islanding detection in single-phase photovoltaic inverters.

Description

Technical Field

[0001] The present invention belongs to the technical field of island detection, and more specifically, relates to a single-phase photovoltaic inverter island detection method and device, and a photovoltaic system. Background Art

[0002] In the field of photovoltaic grid-connected systems, the islanding effect occurs when the photovoltaic system fails to detect the outage and is unable to disconnect from the utility grid due to a power outage, such as a fault or maintenance outage. This creates a self-sufficient power supply island, where the photovoltaic system supplies power to surrounding loads. Generally speaking, the islanding effect can adversely affect the entire distribution system and user-side equipment. Therefore, timely detection of the islanding effect is crucial.

[0003] Existing islanding detection methods primarily include passive and active detection. Passive detection methods do not require additional hardware circuitry, but their islanding detection capabilities are lost when the PV system's output power balances with the local load power. Active detection methods can avoid these drawbacks, but when applied to single-phase PV inverters, due to their typically low power capacity, their application can easily affect the system's operating power parameters. Therefore, improving the reliability of existing islanding detection solutions has become a pressing issue for those skilled in the art. Summary of the Invention

[0004] The object of the present invention is to provide a single-phase photovoltaic inverter islanding detection method and device, and a photovoltaic system, so as to solve the technical problem of low reliability of islanding detection in the prior art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is to provide a single-phase photovoltaic inverter islanding detection method, comprising:

[0006] Obtaining a target grid-connected voltage and a sampling frequency corresponding to the target grid-connected voltage, and determining a reactive voltage component corresponding to the target grid-connected voltage based on the target grid-connected voltage and the sampling frequency; extracting harmonics of a preset frequency from the reactive voltage component, and generating a reactive disturbance amount based on the harmonics of the preset frequency; superimposing the reactive disturbance amount on a reactive current set value in a target control loop, and adjusting an output of a current controller in the target control loop based on a phase angle corresponding to the target grid-connected voltage;

[0007] The target grid-connected voltage is the grid-connected voltage corresponding to the target single-phase photovoltaic inverter, and the target control loop is the control loop corresponding to the target single-phase photovoltaic inverter;

[0008] In response to an internal / external islanding detection trigger signal, the reactive voltage component of the current target grid-connected voltage after phase locking is obtained, and whether an islanding effect exists is determined based on the harmonic amount of the preset frequency contained in the current reactive voltage component.

[0009] In a possible implementation, determining the reactive voltage component corresponding to the target grid-connected voltage based on the target grid-connected voltage and the sampling frequency includes:

[0010] Determining adaptive parameters of a preset digital quadrature signal generator based on the frequency of the target grid-connected voltage and the sampling frequency;

[0011] Inputting the target grid-connected voltage into the preset digital orthogonal signal generator with determined adaptive parameters to obtain the orthogonal component of the target grid-connected voltage;

[0012] A reactive voltage component corresponding to the target grid-connected voltage is determined based on the orthogonal component.

[0013] In a possible implementation, extracting harmonics of a preset frequency from the reactive voltage component includes:

[0014] Filtering the reactive voltage component using a bandpass filter with a preset frequency to obtain a filtered reactive voltage component;

[0015] The power frequency component in the reactive voltage component after filtering is filtered out based on a preset notch filter to obtain harmonics of a preset frequency.

[0016] In a possible implementation, generating a reactive disturbance amount based on harmonics of the preset frequency includes:

[0017] By ΔI=K*I d *U xhz Get the reactive disturbance;

[0018] Among them, U xhz is the harmonic of the preset frequency, K is the preset coefficient, I d is the active output current corresponding to the target single-phase photovoltaic inverter, and ΔI is the reactive disturbance.

[0019] In a possible implementation, before superimposing the reactive disturbance value onto the reactive current set value in the target control loop, the single-phase photovoltaic inverter islanding detection method further includes:

[0020] performing amplitude limiting processing on the reactive disturbance amount;

[0021] The amplitude limiting value corresponding to the amplitude limiting process is positively correlated with the maximum value of the active output current corresponding to the target single-phase photovoltaic inverter.

[0022] In a possible implementation, the current controller in the target control loop includes a reactive current controller and an active current controller;

[0023] The adjusting the output of the current controller in the target control loop based on the phase angle corresponding to the target grid-connected voltage includes:

[0024] Will Input into the active current controller to adjust the output of the active current controller; Input into the reactive current controller to adjust the output of the reactive current controller; wherein, is the phase angle corresponding to the target grid-connected voltage.

[0025] In a possible implementation, the preset frequency range is 5-10 Hz.

[0026] In one possible implementation, determining whether an islanding effect exists based on the amount of harmonics of a preset frequency contained in the current reactive voltage component includes:

[0027] If the harmonic amount of the preset frequency contained in the current reactive voltage component is greater than the preset threshold, it is determined that an islanding effect exists;

[0028] If the amount of harmonics of the preset frequency contained in the current reactive voltage component is not greater than the preset threshold, it is determined that no islanding effect exists.

[0029] In another aspect of the present invention, a single-phase photovoltaic inverter islanding detection device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the single-phase photovoltaic inverter islanding detection method described above are implemented.

[0030] In another aspect of the present invention, a photovoltaic system is provided, comprising:

[0031] The above-mentioned single-phase photovoltaic inverter islanding detection equipment.

[0032] The single-phase photovoltaic inverter islanding detection method and device, and photovoltaic system provided by the present invention have the following beneficial effects:

[0033] Taking into account the single-phase characteristics of the target single-phase photovoltaic inverter, the present invention first uses the target grid-connected voltage and its sampling frequency to extract the reactive voltage component corresponding to the target grid-connected voltage. The extraction of the reactive voltage component effectively supports the subsequent reactive disturbance step. On this basis, since the present invention performs island detection based on reactive disturbance, and the generation of reactive disturbance is based on the voltage parameters corresponding to the single-phase photovoltaic inverter itself (there is no artificially introduced disturbance), it can effectively reduce the impact of the detection process on the parameters of the original circuit of the single-phase photovoltaic inverter, thereby overcoming the problem in the prior art that the electric energy parameters are easily affected by the small capacity of the single-phase photovoltaic inverter, and ensuring the reliability of island detection. In addition, in terms of the generation of reactive disturbance, unlike the method of generating reactive disturbance based on frequency in the prior art, the present invention generates reactive disturbance by extracting harmonics in the reactive voltage component. Compared with the prior art, the present invention can effectively reduce the dependence of island detection on the grid frequency resolution, has a wider scope of application, and further improves the reliability of island detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 A schematic flow chart of a method for detecting islanding in a single-phase photovoltaic inverter according to an embodiment of the present invention;

[0036] Figure 2 A schematic diagram of the structure of a single-phase photovoltaic inverter islanding detection device provided by an embodiment of the present invention;

[0037] Figure 3 A partial control loop diagram corresponding to a single-phase photovoltaic inverter provided in one embodiment of the present invention;

[0038] Figure 4 This is a diagram showing the test results of island detection provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] Please refer to Figure 1 , Figure 1 This is a flow chart of a method for detecting islanding of a single-phase photovoltaic inverter according to an embodiment of the present invention. The method comprises:

[0042] S101: Obtain a target grid-connected voltage and a sampling frequency corresponding to the target grid-connected voltage, and determine a reactive voltage component corresponding to the target grid-connected voltage based on the target grid-connected voltage and the sampling frequency. Extract harmonics of a preset frequency from the reactive voltage component, and generate a reactive disturbance based on the harmonics of the preset frequency. Superimpose the reactive disturbance on the reactive current setpoint in the target control loop, and adjust the output of the current controller in the target control loop based on the phase angle corresponding to the target grid-connected voltage.

[0043] In this embodiment, the target grid-connected voltage is the grid-connected voltage corresponding to the target single-phase photovoltaic inverter, and the target control loop is the control loop corresponding to the target single-phase photovoltaic inverter. The target control loop is used to control the active and reactive power of the target single-phase photovoltaic inverter by controlling the active and reactive power of the grid current. The target control loop can be an existing control loop, and its detailed structure is not further described here.

[0044] In this embodiment, taking into account the single-phase characteristics of the target single-phase photovoltaic inverter, the present invention first uses the target grid-connected voltage and its sampling frequency to determine the reactive component (i.e., reactive voltage component) corresponding to the target grid-connected voltage, and then extracts the harmonics of the preset frequency from the reactive voltage component, and realizes the generation of reactive disturbance based on the harmonics of the preset frequency.

[0045] In this embodiment, step S101 is essentially a disturbance step before islanding detection, that is, a corresponding reactive disturbance is generated based on the harmonics of a preset frequency extracted from the reactive voltage component, and reactive disturbance is achieved by superimposing the reactive disturbance onto the reactive current set value in the target control loop.

[0046] Since the embodiment of the present invention extracts the reactive voltage component and also adopts a reactive disturbance method, the target control loop uses a method of separately calculating the reactive component and the active component when performing control calculations on the single-phase photovoltaic inverter. Therefore, in order to generate the final control quantity, it is also necessary to use the phase angle of the target grid-connected voltage to transform the output of the current controller in the target control loop to synthesize the final control quantity of the single-phase photovoltaic inverter. In other words, "adjusting the output of the current controller in the target control loop based on the phase angle corresponding to the target grid-connected voltage" is essentially to adapt to the aforementioned reactive voltage component extraction process (that is, to adapt to the process of "determining the reactive voltage component corresponding to the target grid-connected voltage based on the target grid-connected voltage and the sampling frequency"), with the purpose of ensuring that the reactive voltage component is extracted from the single-phase data, thereby completing the reactive disturbance process. In one possible implementation of the embodiment of the present invention, the current controller in the target control loop includes a reactive current controller and an active current controller. Adjusting the output of the current controller in the target control loop based on the phase angle corresponding to the target grid-connected voltage can be detailed as follows:

[0047] Will Input into the active current controller to adjust the output of the active current controller. Input to the reactive current controller to adjust the output of the reactive current controller. is the phase angle corresponding to the target grid-connected voltage.

[0048] S102: In response to an internal / external islanding detection trigger signal, obtain the reactive voltage component of the current target grid-connected voltage after phase locking, and determine whether there is an islanding effect based on the harmonic amount of a preset frequency contained in the current reactive voltage component.

[0049] In this embodiment, when islanding detection is required (i.e., when an internally transmitted or externally input islanding detection signal is received), the reactive voltage component of the current target grid-connected voltage after phase locking can be extracted. Given that a reactive disturbance has occurred in step S101, when the grid is operating normally, no harmonic disturbance of the preset frequency is detected due to the presence of the grid, and harmonics of the preset frequency do not accumulate. Once a grid fault occurs, the reactive disturbance continues, and harmonics of the preset frequency rapidly accumulate. At this point, detecting the amount of harmonics of the preset frequency contained in the current reactive voltage component can determine whether an islanding effect exists.

[0050] As can be seen from the above description, considering the single-phase characteristics of the target single-phase photovoltaic inverter, the embodiment of the present invention first uses the target grid-connected voltage and its sampling frequency to extract the reactive voltage component corresponding to the target grid-connected voltage. The extraction of this reactive voltage component effectively supports the subsequent reactive disturbance step. On this basis, since the embodiment of the present invention performs island detection based on reactive disturbance, and the generation of reactive disturbance is based on the voltage parameters corresponding to the single-phase photovoltaic inverter itself (no artificially introduced disturbance), it can effectively reduce the impact of the detection process on the parameters of the original circuit of the single-phase photovoltaic inverter, thereby overcoming the problem in the prior art that the power parameters are easily affected by the small capacity of the single-phase photovoltaic inverter, and ensuring the reliability of island detection. In addition, in terms of the generation of reactive disturbance, unlike the prior art method of generating reactive disturbance based on frequency, the embodiment of the present invention generates reactive disturbance by extracting harmonics from the reactive voltage component. Compared with the prior art, the embodiment of the present invention can effectively reduce the dependence of island detection on the grid frequency resolution, has a wider range of applicability, and further improves the reliability of island detection.

[0051] In one possible implementation, determining a reactive voltage component corresponding to the target grid-connected voltage based on the target grid-connected voltage and the sampling frequency includes:

[0052] The adaptive parameters of the preset digital quadrature signal generator are determined based on the frequency of the target grid-connected voltage and the sampling frequency.

[0053] The target grid-connected voltage is input into a preset digital orthogonal signal generator with determined adaptive parameters to obtain the orthogonal components of the target grid-connected voltage.

[0054] The reactive voltage component corresponding to the target grid-connected voltage is determined based on the orthogonal component.

[0055] In this embodiment, the adaptive parameters of the preset digital orthogonal signal generator are determined based on the frequency and sampling frequency of the target grid-connected voltage, and the target grid-connected voltage is input into the preset digital orthogonal signal generator with the determined adaptive parameters. The orthogonal components of the target grid-connected voltage can be obtained by using the existing frequency-adaptive SOGI algorithm (i.e., the second-order generalized integral phase-locked algorithm). In other words, the orthogonal components in the target grid-connected voltage can be extracted based on the frequency-adaptive SOGI algorithm (i.e., the second-order generalized integral phase-locked algorithm) to obtain the α component of the target grid-connected voltage after phase-locking and the β component of the target grid-connected voltage after phase-locking (i.e., obtaining the 0-degree and 90-degree orthogonal signals of the grid voltage). The α component of the target grid-connected voltage after phase-locking and the β component of the target grid-connected voltage after phase-locking are subjected to Park transformation (i.e., conversion from the αβ coordinate system to the dq coordinate system) to obtain the reactive voltage component of the target grid-connected voltage after phase-locking. In one possible implementation, extracting harmonics of a preset frequency from the reactive voltage component includes:

[0056] The reactive voltage component is filtered by a bandpass filter based on a preset frequency to obtain a filtered reactive voltage component.

[0057] The preset notch filter removes the power frequency component in the reactive voltage component after filtering to obtain harmonics of the preset frequency.

[0058] In this embodiment, a bandpass filter with a preset frequency can be used to filter the reactive voltage component to obtain a filtered reactive voltage component (i.e., harmonics of the preset frequency including the power frequency component). A preset notch filter can then be used to filter out the power frequency component to obtain harmonics of the preset frequency. For example, to extract 5Hz harmonics, the reactive voltage component can be filtered with a 5Hz bandpass filter, and then a notch filter with a 50Hz bandpass filter (other frequencies can also be set depending on the actual application) can be used to filter out the power frequency component, ultimately obtaining 5Hz harmonics. The parameters of the notch filter can be adaptively adjusted based on the switching frequency and grid frequency.

[0059] In a possible implementation, generating a reactive disturbance based on harmonics of a preset frequency includes:

[0060] By ΔI=K*I d *U xhz Get the reactive disturbance.

[0061] Among them, U xhz is the harmonic of the preset frequency, K is the preset coefficient, I d is the active output current corresponding to the target single-phase photovoltaic inverter, and ΔI is the reactive disturbance.

[0062] In this embodiment, the reactive disturbance is associated with the active output current corresponding to the target single-phase photovoltaic inverter, which can better limit the size of the reactive disturbance within a certain range, thereby reducing the impact of the reactive disturbance on the power quality of the photovoltaic system.

[0063] In one possible implementation, before adding the reactive disturbance value to the reactive current set value in the target control loop, the single-phase photovoltaic inverter islanding detection method further includes:

[0064] Limit the reactive disturbance.

[0065] The amplitude limiting value corresponding to the amplitude limiting process is positively correlated with the maximum value of the active output current corresponding to the target single-phase photovoltaic inverter.

[0066] In order to avoid increasing the output current harmonics corresponding to the target single-phase photovoltaic inverter as much as possible, this embodiment may also limit the reactive disturbance before adding it to the reactive current set value in the target control loop.

[0067] The limit value corresponding to the limit processing can be positively correlated with the maximum active output current corresponding to the target single-phase photovoltaic inverter. For example, the limit value Island_Iq_Limit can satisfy the following equation: Island_Iq_Limit = MAX_ID_8K * K_ISLAND_IQLIMIT, where MAX_ID_8K can be the active output current corresponding to the target single-phase photovoltaic inverter, and K_ISLAND_IQLIMIT can be a preset limit coefficient, which can be set according to actual needs.

[0068] In a possible implementation, the preset frequency range is 5-10 Hz.

[0069] In this embodiment, in order to prevent harmonic oscillation, the range of the preset frequency needs to be much smaller than the fundamental wave 50Hz. On this basis, in order to further meet the period of islanding protection (2s is taken as an example in this embodiment), the value of a single period of the harmonic is more appropriately between 0.5Hz and 5Hz. However, the value of 0.5Hz can only cover one period, which is too short. It is more appropriate to take 5-10 periods. Therefore, this embodiment sets the range of the preset frequency to between 5-10Hz, thereby ensuring the effect of islanding detection while avoiding harmonic oscillation.

[0070] In one possible implementation, determining whether an islanding effect exists based on the amount of harmonics of a preset frequency contained in the current reactive voltage component includes:

[0071] If the amount of harmonics of the preset frequency contained in the current reactive voltage component is greater than a preset threshold, it is determined that an islanding effect exists.

[0072] If the amount of harmonics of the preset frequency contained in the current reactive voltage component is not greater than the preset threshold, it is determined that no islanding effect exists.

[0073] In this embodiment, if a power grid failure occurs, the presence of reactive disturbance will cause the harmonics of the preset frequency to continue to accumulate and exceed a certain threshold. Therefore, this embodiment can determine whether there is an islanding effect by detecting whether the amount of harmonics of the preset frequency contained in the current reactive voltage component is greater than the preset threshold.

[0074] In this embodiment, the method for extracting the harmonic amount of the preset frequency contained in the current reactive voltage component can be: extracting the absolute value of the harmonic of the preset frequency contained in the current reactive voltage component and integrating it, and low-pass filtering the integrated harmonic absolute value to obtain the harmonic amount of the preset frequency contained in the current reactive voltage component.

[0075] In this embodiment, the preset threshold value may be associated with the aforementioned reactive disturbance amount to improve the accuracy of islanding detection.

[0076] In one possible implementation, the single-phase photovoltaic inverter islanding detection method further includes:

[0077] If it is determined that an islanding effect exists, the islanding effect protection action is triggered.

[0078] In this embodiment, the protection time of the islanding effect protection action can be set according to design requirements.

[0079] In one possible implementation, the (grid-connected) control loop corresponding to the target single-phase photovoltaic inverter can be as follows: Figure 3 It should be noted that Figure 3 The parts directly related to the reactive disturbance are shown, and the parts not directly related to the reactive disturbance are omitted. Figure 3 The design is based on the preset frequency of 5Hz. Figure 3 Where Ugrid is the target grid voltage, (i.e., θ) is the phase angle corresponding to the target grid-connected voltage, SOGI is the second-order generalized integral software phase-locked loop algorithm, u alpha is the α component of the target grid-connected voltage after phase locking, u beta is the β component of the target grid-connected voltage after phase locking, is the initial angular frequency, is the current angular frequency, t is the time, u q is the reactive component after the target grid voltage is phase-locked, u d is the active component of the target grid-connected voltage after phase locking, 5hz refers to the 5Hz bandpass filter, 50Hz refers to the 50Hz notch filter, Id is the active output current corresponding to the target single-phase photovoltaic inverter, Iq is the reactive output current corresponding to the target single-phase photovoltaic inverter, and Uref is the reference voltage corresponding to the target single-phase photovoltaic inverter. Figure 3 As shown in the figure, the reactive voltage component after the target grid voltage is phase-locked can be determined by the SOGI algorithm, and then the harmonics of the preset frequency can be extracted from the reactive voltage component to generate reactive disturbance. The disturbance can be completed by adding the reactive disturbance to the given value of reactive current (subsequently, the The output of the current controller is converted to generate the final modulation value. Based on this, when islanding detection is required, the presence of an islanding effect can be determined based on the amount of harmonics of a preset frequency contained in the current reactive voltage component. The method provided by the embodiments of the present invention is simple to use, requires no additional hardware, has minimal impact on power quality, and offers relatively high reliability for islanding detection.

[0080] The present invention is also based on Figure 3 A specific experiment was conducted on the scheme. Figure 4 This is the test result of island detection in the embodiment of the present invention ( Figure 4The output current in the figure refers to the output current of the single-phase photovoltaic inverter). Figure 4 It can be seen that when the power grid existed in the early stage, the 5Hz component in the power grid was very low, so the disturbance was also very small. When the power grid was removed, due to the loss of the self-balancing ability of the power grid, the 5Hz harmonic content in the island power grid voltage will become larger and larger by continuously injecting 5Hz reactive disturbance into the power grid. As the amount of 5Hz reactive disturbance injected in the islanding situation becomes larger and larger, the amount of 5Hz disturbance in the island also becomes larger and larger, continuously forming positive feedback. At this time, after extracting the 5Hz harmonic content, islanding detection can be performed. According to experiments, the present invention can ensure that the detection of the islanding effect is completed within 200ms, which once again proves the convenience of the solution of the present invention.

[0081] Please refer to Figure 2In another aspect, the present invention further provides a single-phase photovoltaic inverter islanding detection device 200, comprising: one or more processors 201, one or more input devices 202, one or more output devices 203, and one or more memories 204. The processors 201, input devices 202, output devices 203, and memories 204 communicate with each other via a communication bus 205. Memory 204 is used to store computer programs, which include program instructions. Processor 201 is used to execute the program instructions stored in memory 204. Processor 201 is configured to invoke the program instructions to execute the steps of each of the above-described method embodiments. It should be understood that in the embodiments of the present invention, the processor 201 may be a central processing unit (CPU). The processor may also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), 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 be any conventional processor, etc. The input device 202 may include a touchpad, a fingerprint sensor (for collecting the user's fingerprint information and fingerprint direction information), a microphone, etc., and the output device 203 may include a display (LCD, etc.), a speaker, etc. The memory 204 may include a read-only memory and a random access memory, and provide instructions and data to the processor 201. A portion of the memory 204 may also include a non-volatile random access memory. For example, the memory 204 may also store information about the device type. In a specific implementation, the processor 201, the input device 202, and the output device 203 described in the embodiment of the present invention may execute the implementation methods described in the first embodiment and the second embodiment of the single-phase photovoltaic inverter island detection method provided in the embodiment of the present invention.

[0082] In another aspect of the present invention, a photovoltaic system is provided, comprising:

[0083] The single-phase photovoltaic inverter islanding detection equipment described above.

[0084] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A single-phase photovoltaic inverter islanding detection method, characterized in that: include: Obtaining a target grid-connected voltage and a sampling frequency corresponding to the target grid-connected voltage, and determining a reactive voltage component corresponding to the target grid-connected voltage based on the target grid-connected voltage and the sampling frequency; Extracting harmonics of a preset frequency from the reactive voltage component, and generating a reactive disturbance amount based on the harmonics of the preset frequency; Superimposing the reactive disturbance onto a reactive current set value in a target control loop, and adjusting an output of a current controller in the target control loop based on a phase angle corresponding to the target grid-connected voltage; The preset frequency range is 1 / 10 to 1 / 5 of the fundamental frequency; The target grid-connected voltage is the grid-connected voltage corresponding to the target single-phase photovoltaic inverter, and the target control loop is the control loop corresponding to the target single-phase photovoltaic inverter; In response to an internal / external islanding detection trigger signal, the reactive voltage component of the current target grid-connected voltage after phase locking is obtained, and whether an islanding effect exists is determined based on the harmonic amount of the preset frequency contained in the current reactive voltage component.

2. The single-phase photovoltaic inverter islanding detection method according to claim 1, wherein: The determining, based on the target grid-connected voltage and the sampling frequency, a reactive voltage component corresponding to the target grid-connected voltage includes: Determining adaptive parameters of a preset digital quadrature signal generator based on the frequency of the target grid-connected voltage and the sampling frequency; Inputting the target grid-connected voltage into the preset digital orthogonal signal generator with determined adaptive parameters to obtain the orthogonal component of the target grid-connected voltage; A reactive voltage component corresponding to the target grid-connected voltage is determined based on the orthogonal component.

3. The single-phase photovoltaic inverter islanding detection method according to claim 1, wherein: The step of extracting harmonics of a preset frequency from the reactive voltage component comprises: Filtering the reactive voltage component using a bandpass filter with a preset frequency to obtain a filtered reactive voltage component; The power frequency component in the reactive voltage component after filtering is filtered out based on a preset notch filter to obtain harmonics of a preset frequency.

4. The single-phase photovoltaic inverter islanding detection method according to claim 1, wherein: The reactive disturbance amount generated by harmonics based on the preset frequency includes: By ΔI=K*I d *U xhz Get the reactive disturbance; Among them, U xhz is the harmonic of the preset frequency, K is the preset coefficient, I d is the active output current corresponding to the target single-phase photovoltaic inverter, and ΔI is the reactive disturbance.

5. The single-phase photovoltaic inverter islanding detection method according to claim 4, wherein: Before superimposing the reactive disturbance onto the reactive current set value in the target control loop, the single-phase photovoltaic inverter islanding detection method further includes: performing amplitude limiting processing on the reactive disturbance amount; The amplitude limiting value corresponding to the amplitude limiting process is positively correlated with the maximum value of the active output current corresponding to the target single-phase photovoltaic inverter.

6. The single-phase photovoltaic inverter islanding detection method according to claim 1, wherein: The current controller in the target control loop includes a reactive current controller and an active current controller; The adjusting the output of the current controller in the target control loop based on the phase angle corresponding to the target grid-connected voltage includes: Will Input into the active current controller to adjust the output of the active current controller; Input into the reactive current controller to adjust the output of the reactive current controller; wherein, is the phase angle corresponding to the target grid-connected voltage.

7. The single-phase photovoltaic inverter islanding detection method according to any one of claims 1 to 6, characterized in that: The preset frequency range is 5-10 Hz.

8. The single-phase photovoltaic inverter islanding detection method according to any one of claims 1 to 6, characterized in that: The determining whether an islanding effect exists based on the amount of harmonics of a preset frequency contained in the current reactive voltage component includes: If the harmonic amount of the preset frequency contained in the current reactive voltage component is greater than the preset threshold, it is determined that an islanding effect exists; If the amount of harmonics of the preset frequency contained in the current reactive voltage component is not greater than the preset threshold, it is determined that no islanding effect exists.

9. A single-phase photovoltaic inverter islanding detection device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

10. A photovoltaic system, characterized in that: It includes the single-phase photovoltaic inverter islanding detection device as described in claim 9.

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