Island protection method, device and equipment for multiple distributed power supplies and medium

Abstract

The invention relates to the technical field of photovoltaic distributed power supplies, in particular to a multi-distributed power supply island protection method, device and equipment and a medium, and the method comprises the steps: replacing a phase-locked loop control mode through a double-second-order generalized integrator to control the output frequency of an inverter, and collecting the tracking frequency generated by a synchronous frequency-locked loop; judging whether the tracking frequency reaches a set condition or not, if so, judging that an island occurs, and cutting off each distributed power supply; if not, extracting a high-frequency harmonic component of the inverter by using a high-pass filter, and performing local weighted linear fitting to obtain a frequency fitting curve; and calculating the slope of the frequency fitting curve, judging whether the slope of the frequency fitting curve exceeds a set threshold according to the threshold, if so, judging that an island occurs, and cutting off each distributed power supply. According to the method, the dynamic response speed is high, misjudgment caused by power grid disturbance in a normal grid-connected state can be prevented, and non-blind area detection of the multi-DG island is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic distributed power supply, and in particular to a method, device, equipment and medium for protecting multiple distributed power supply islands. Background Art

[0002] As the penetration rate of distributed generation (DG) represented by renewable energy and clean energy in the distribution network increases, when the distribution network is interrupted due to failure, maintenance and other reasons, an isolated network operation system consisting only of distributed generation and load will be formed. This will endanger the safety of maintenance personnel on the power transmission line, affect the action program of the protection switch on the distribution system, impact the power grid protection device, affect the quality of transmitted power, and cause the power supply voltage and frequency in the power island area to be unstable.

[0003] At present, the anti-islanding protection methods are mainly divided into remote method, passive method and active method. Among them, the communication-based islanding detection method is also called remote method. It performs islanding protection by detecting the signal state of the switch, that is, establishing communication between the power grid and DG, and judging the occurrence of islanding according to the communication signal sent by the circuit breaker on the power grid side. The remote method has fast response speed and high detection efficiency, but it has high requirements on the cost of communication equipment. The active method is to inject a small disturbance into the system to break the original stable state of the system and then detect the islanding; the active method includes active frequency drift (AFD), sliding mode frequency shift (SMS), positive feedback frequency shift (Sandia Frequency Shift, SFS), active power / reactive power disturbance method, etc. The active method has a small detection blind area, but with the access of a high proportion of distributed power sources, the active islanding detection method also needs to consider the problem of dilution effect in the islanding detection process. The passive method mainly detects islands by detecting changes in various electrical quantities such as frequency, phase, and grid voltage at the common coupling point. The method is simple in principle, easy to operate, and has no harmonic injection impact on the power system. However, the traditional passive method has the disadvantages of large detection blind areas, low accuracy, and poor results.

[0004] In the prior art, island protection cannot detect islands formed by pure resistive loads, and cannot distinguish the impact of grid disturbances on electrical quantities. When the power output by the inverter approximately matches or completely matches the power required by the local load, a detection blind spot will appear.

[0005] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0006] The present invention provides a multi-distributed power supply island protection method, device, equipment and medium, thereby effectively solving the problems in the background technology.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: a multi-distributed power supply island protection method, comprising the following steps:

[0008] Using a synchronous frequency-locked loop control method using a dual second-order generalized integrator to replace a phase-locked loop to control the output frequency of the inverter, and collecting the tracking frequency generated by the synchronous frequency-locked loop;

[0009] Determine whether the tracking frequency reaches a set condition, and if so, determine that an island occurs and cut off each distributed power source;

[0010] If it is not reached, a high-pass filter is used to extract the high-frequency harmonic components of the inverter, and a local weighted linear fitting is performed to obtain a frequency fitting curve;

[0011] The slope of the frequency fitting curve is calculated, and it is determined whether the slope of the frequency fitting curve exceeds a set threshold according to a threshold. If it exceeds a set threshold, it is determined that an island occurs, and each distributed power source is cut off.

[0012] Furthermore, the use of a synchronous frequency-locked loop control method using a biquad generalized integrator to replace a phase-locked loop to control the output frequency of the inverter comprises the following steps:

[0013] The three-phase voltage containing harmonic components in the abc coordinate system is transformed to the two-phase static coordinate system by Clarke to obtain the two-phase static voltage;

[0014] The two-phase static voltage is respectively passed through a dual-orthogonal signal generator to generate an in-phase output signal and a 90° phase lag signal to generate a tracking frequency;

[0015] The synchronous frequency-locked loop is used to track the frequency of the inverter AC side and output the tracking frequency.

[0016] Furthermore, the performing of local weighted linear fitting includes:

[0017] Based on the existing samples, a new regression coefficient θ is fitted through the cost function. Given the sequence x i (i=1,2,…,m), the cost function is as follows:

[0018]

[0019] Where: y i is the true value, f(x i )=θ T x i is the predicted value, wi For x i The weight of , m is the number of sequences;

[0020] The regression coefficient θ is an initialization vector whose elements can be any random numbers and are updated in each iteration:

[0021]

[0022] Where: α is the iteration step length;

[0023] Weight w i Through the predicted point x and x i The closer the distance, the greater the x i The larger the weight, the corresponding error value (f(x i )-y i ) has a greater impact on the fitting results;

[0024] Introduce w into F(θ) i , weight function w i The calculation formula is:

[0025]

[0026] Where: x is the point to be predicted; e is the control weight w i The parameter of the rate of change; the larger e is, the larger w i Follow x i The rate of decrease increases as the distance from x increases.

[0027] Furthermore, the e is set to 0.001.

[0028] Furthermore, the determining whether the tracking frequency reaches a set condition includes:

[0029] Determine whether the tracking frequency f1 is less than 49.5 Hz or greater than 49.5 Hz.

[0030] Further, the calculating the slope of the frequency fitting curve includes:

[0031] Deriving the frequency fitting curve to obtain a slope of the frequency fitting curve;

[0032] The absolute value of the slope of the frequency fitting curve is calculated, and a threshold value is determined for the absolute value.

[0033] Furthermore, the threshold judgment condition includes:

[0034] Whether the absolute value of the slope of the frequency fitting curve is greater than 2, if so, it is determined that an island occurs.

[0035] The present invention also includes a multi-distributed power supply island protection device, using the above method, including:

[0036] A synchronous frequency-locked loop unit, used to control the output frequency of the inverter using a synchronous frequency-locked loop control method using a dual second-order generalized integrator instead of a phase-locked loop, and to collect a tracking frequency generated by the synchronous frequency-locked loop;

[0037] A frequency judgment unit, used to judge whether the tracking frequency reaches a set condition, and if so, it is determined that an island occurs and each distributed power source is cut off;

[0038] A local weighted linear fitting unit, used for extracting the high-frequency harmonic components of the inverter using a high-pass filter and performing local weighted linear fitting to obtain a frequency fitting curve when the tracking frequency does not reach a set condition;

[0039] The slope judgment unit is used to calculate the slope of the frequency fitting curve, and judge whether the slope of the frequency fitting curve exceeds a set threshold according to a threshold. If it exceeds, it is determined that an island occurs and each distributed power source is cut off.

[0040] The present invention also includes a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method described above is implemented.

[0041] The present invention also includes a storage medium on which a computer program is stored. When the computer program is executed by a processor, the method described above is implemented.

[0042] The beneficial effects of the present invention are as follows: (1) the synchronous frequency-locked loop of the dual second-order generalized integrator requires fewer components, has good economy, fast dynamic response speed, and supports the frequency of the grid-connected point; (2) the low-frequency component is effectively filtered out by a high-pass filter, which can prevent misjudgment caused by grid disturbance in a normal grid-connected state; (3) the local weighted linear fitting algorithm adopted can avoid the influence of multiple DGs on the electrical characteristic quantity when multiple DGs are connected, and realize the detection of multiple DG islands without blind spots. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 is a flow chart of the method of the present invention;

[0045] Figure 2This is a schematic diagram of multiple DG grid connection;

[0046] Figure 3 This is the control block diagram of DSOGI-FLL;

[0047] Figure 4 It is a structural schematic diagram of the device of the present invention;

[0048] Figure 5 It is a structural schematic diagram of the computer device of the present invention. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0050] like Figure 1 As shown: A multi-distributed power supply island protection method includes the following steps:

[0051] A synchronous frequency-locked loop control method using a dual second-order generalized integrator is used to replace a phase-locked loop to control the output frequency of the inverter, and a tracking frequency generated by the synchronous frequency-locked loop is collected;

[0052] Determine whether the tracking frequency reaches the set condition. If so, it is determined that an island has occurred and all distributed power sources are cut off;

[0053] If it is not reached, a high-pass filter is used to extract the high-frequency harmonic components of the inverter, and a local weighted linear fitting is performed to obtain a frequency fitting curve;

[0054] The slope of the frequency fitting curve is calculated, and it is determined whether the slope of the frequency fitting curve exceeds the set threshold according to the threshold. If it exceeds the threshold, it is determined that an island has occurred and each distributed power source is cut off.

[0055] Based on the frequency change rate of multi-distributed power island protection method, the DSOGI-FLL (Double Second-Order Generalized Integrator-Frequency Locked Loop) control method has a fast dynamic response speed. Due to the influence of the inverter unit and nonlinear load after the island occurs, the inverter output current will produce high-frequency harmonics. In order to effectively distinguish the interference of the grid under grid connection and amplify the influence of the island effect, a high-frequency filter is used to eliminate the low-frequency component. The local weighted linear regression algorithm (Locally Weighted LinearRegression, LWLR) is used to fit the sampling frequency data of the frequency-locked loop, which can highlight the local characteristics and effectively avoid the detection blind area when the pure resistive load and power matching.

[0056] The local weighted linear fitting algorithm adopted can avoid the impact of multiple DG (Distributed Generation) access on the electrical characteristic quantity, realize the island detection of multi-DG system, and eliminate the detection blind area; compared with other detection methods, this method can avoid the misjudgment problem caused by power grid disturbance while achieving fast and reliable detection, and will not affect the power quality of the system.

[0057] The output power of distributed power sources often fluctuates due to changes in the light intensity and temperature of the photovoltaic panel surface. In order to ensure the power quality of the DG grid-connected point, distributed power sources usually operate in a grid-connected state. For a specific grid-connected schematic diagram, see Figure 2 .

[0058] Depend on Figure 2 It can be seen that when DG is connected to the grid, the power required by the load is jointly provided by the power grid and distributed power sources. When the island phenomenon occurs, the power matching in the system will determine the corresponding change in the PCC (Point Of Common Coupling) frequency. If the output power of the inverter after the island is close to or completely consistent with the power required by the local load, the output frequency change of the inverter will be relatively small. At this time, the traditional over / under frequency detection method will face the problem of detection blind area. With the access of multiple DGs, the frequency change will become weaker, which will further expand the detection blind area.

[0059] Depend on Figure 2 It can be seen that in the normal grid-connected state, the switch CB is closed, and the inverter and the large power grid supply power to the load at the same time. Due to the balancing effect of the large power grid, the voltage, current and other parameters of the common coupling point PCC can remain stable, and the harmonic amount is very small. When the switch on the large power grid side is cut off due to a fault or other reasons, the inverter system and the local load will form an unplanned island. At this time, the inverter system will independently assume the responsibility of supplying power to the local load. In this case, since the PCC loses the balancing effect of the large power grid and is disturbed by the inverter unit and nonlinear load, the current output by the inverter will generate high-frequency harmonics. Therefore, in order to amplify the influence of the high-frequency harmonics on the frequency, a high-pass filter is designed to extract the high-frequency harmonic components.

[0060] In this embodiment, a synchronous frequency-locked loop control method using a dual second-order generalized integrator is used instead of a phase-locked loop to control the output frequency of the inverter. The control principle is as follows: Figure 3 As shown, the control strategy can be divided into three parts:

[0061] The three-phase voltage U containing harmonic components in the abc coordinate system a , U b , U c After Clarke transformation to the two-phase stationary coordinate system, the two-phase stationary voltage U is obtained.α , U β ;

[0062] The two-phase static voltage U α , U β The in-phase output signal u′ is generated by the dual orthogonal signal generator α , u′ β and 90° phase lag signals qu′α, qu′β; U α , U β The in-phase output signal u′ is generated by the dual orthogonal signal generator α , and the 90° phase-lag signal qu′ α , qu′ β Finally, the positive sequence voltage component is obtained through the positive and negative sequence separation calculation module

[0063] The synchronous frequency-locked loop is used to track the frequency on the inverter AC side and output the tracking frequency.

[0064] As a typical nonlinear load, power electronic devices will generate a large amount of harmonic currents, which have a serious impact on the power quality of the distribution network. Therefore, in this embodiment, a DSOGI-FLL control method is proposed to replace the traditional phase-locked loop control, so that the slave inverter can maintain phase lock in real time to solve the multi-inverter island detection. The FLL control module is used to track the frequency of the inverter AC side, improve the response speed of the system, and quickly achieve frequency adaptation.

[0065] The output frequency of the frequency-locked loop control mode is 50Hz under normal grid connection. When islanding occurs, it is affected by the load and becomes the load resonant frequency.

[0066] Among them, local weighted linear fitting is performed, including:

[0067] Based on the existing samples, a new regression coefficient θ is fitted through the cost function. Given the sequence x i (i=1,2,…,m), the cost function is as follows:

[0068]

[0069] Where: y i is the true value, f(x i )=θ T x i is the predicted value, w i For x i The weight of , m is the number of sequences;

[0070] The regression coefficient θ is an initialization vector whose elements can be any random numbers and are updated in each iteration:

[0071]

[0072] Where: α is the iteration step length;

[0073] Weight w i Through the predicted point x and x i The closer the distance, the greater the x i The larger the weight, the corresponding error value (f(x i )-y i ) has a greater impact on the fitting results;

[0074] Introduce w into F(θ) i , we can get a similar fitting effect as adding a polynomial to a polynomial linear fit. The weight function w i The calculation formula is:

[0075]

[0076] Where: x is the point to be predicted; e is the control weight w i The parameter of the rate of change; the larger e is, the larger w i Follow x i The rate of decrease increases as the distance from x increases.

[0077] The local weighted linear regression algorithm is an improved linear regression algorithm. Its basic idea is to assign weights to each prediction data by introducing a weighting function. Points near the predicted point have higher weights, and the weights decrease as the distance increases, that is, the weights of sampled data in an area containing more data are greater than other data. Therefore, compared with the ordinary linear fitting algorithm, the local weighted linear regression algorithm highlights the local features of the sampled data and has higher accuracy.

[0078] As a preference of the above embodiment, e is set to 0.001, at which time the fitting result can best reflect the distribution characteristics of the sample data.

[0079] In this embodiment, it is determined whether the tracking frequency reaches a set condition, and the set condition includes:

[0080] Determine whether the tracking frequency f1 is less than 49.5 Hz or greater than 49.5 Hz.

[0081] Calculate the slope of the frequency fitting curve, including:

[0082] Derivative the frequency fitting curve to obtain the slope of the frequency fitting curve;

[0083] The absolute value of the slope of the frequency fitting curve is calculated, and a threshold value is determined for the absolute value.

[0084] For the convenience of comparison, considering that the frequency change rate may produce negative values, this article will process the calculation results in absolute values. In order to avoid the system making wrong judgments due to the threshold being too small or the system taking no action due to the threshold being too large, thus affecting the accuracy of island detection, the judgment threshold K is set to 2 after comprehensive consideration. If the rate of change of frequency (RoCoF) exceeds the preset threshold, the system will determine it as an island and disconnect the circuit breaker to achieve island detection.

[0085] like Figure 4 As shown, this embodiment also includes a multi-distributed power supply island protection device, using the above method, including:

[0086] A synchronous frequency-locked loop unit, used to control the output frequency of the inverter using a synchronous frequency-locked loop control method using a dual second-order generalized integrator instead of a phase-locked loop, and to collect a tracking frequency generated by the synchronous frequency-locked loop;

[0087] A frequency judgment unit is used to judge whether the tracking frequency reaches the set condition. If so, it is determined that an island has occurred and each distributed power source is cut off;

[0088] The local weighted linear fitting unit is used to extract the high-frequency harmonic components of the inverter using a high-pass filter and perform local weighted linear fitting to obtain a frequency fitting curve when the tracking frequency does not reach the set condition;

[0089] The slope judgment unit is used to calculate the slope of the frequency fitting curve and judge whether the slope of the frequency fitting curve exceeds the set threshold according to the threshold. If it exceeds, it is determined that an island occurs and each distributed power source is cut off.

[0090] This embodiment has the following advantages: (1) The synchronous frequency-locked loop of the dual second-order generalized integrator requires fewer components, has good economy, fast dynamic response speed, and supports the grid-connected point frequency; (2) The high-pass filter is used to effectively filter out low-frequency components, which can prevent misjudgment caused by grid disturbances under normal grid-connected conditions; (3) The local weighted linear fitting algorithm used can avoid the impact of multiple DG access on electrical characteristic quantities, and realize blind-zone detection of multiple DG islands.

[0091] See also Figure 5 A computer device 400 provided in an embodiment of the present application includes: a processor 410 and a memory 420, wherein the memory 420 stores a computer program executable by the processor 410, and when the computer program is executed by the processor 410, the above method is executed.

[0092] The embodiment of the present application further provides a storage medium 430 on which a computer program is stored. When the computer program is run by the processor 410, the above method is executed.

[0093] Among them, the storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable red-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, disk or optical disk.

[0094] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0095] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0096] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0097] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0098] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic devices), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0099] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0100] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0101] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for protecting multiple distributed power supply islands, characterized in that: The steps include: Using a synchronous frequency-locked loop control method using a dual second-order generalized integrator to replace a phase-locked loop to control the output frequency of the inverter, and collecting the tracking frequency generated by the synchronous frequency-locked loop; Determine whether the tracking frequency reaches a set condition, and if so, determine that an island occurs and cut off each distributed power source; If it is not reached, a high-pass filter is used to extract the high-frequency harmonic components of the inverter, and a local weighted linear fitting is performed to obtain a frequency fitting curve; The slope of the frequency fitting curve is calculated, and it is determined whether the slope of the frequency fitting curve exceeds a set threshold according to a threshold. If it exceeds the threshold, it is determined that an island occurs, and each distributed power source is cut off.

2. The multi-distributed power supply island protection method according to claim 1, characterized in that: The method of using a synchronous frequency-locked loop control method using a biquad generalized integrator to replace a phase-locked loop to control the output frequency of the inverter comprises the following steps: The three-phase voltage containing harmonic components in the abc coordinate system is transformed to the two-phase static coordinate system by Clarke to obtain the two-phase static voltage; The two-phase static voltage is respectively passed through a dual-orthogonal signal generator to generate an in-phase output signal and a 90° phase lag signal to generate a tracking frequency; The synchronous frequency-locked loop is used to track the frequency of the inverter AC side and output the tracking frequency.

3. The multi-distributed power supply island protection method according to claim 1, characterized in that: The local weighted linear fitting comprises: Based on the existing samples, a new regression coefficient θ is fitted through the cost function. Given the sequence x i , i=1,2,…,m, the cost function is as follows: Where: y i is the true value, θ T x i is the predicted value, w i For x i The weight of , m is the number of sequences; The regression coefficient θ is an initialization vector whose elements can be any random numbers and are updated in each iteration: Where: α is the iteration step length; w i The calculation formula is: Where: x is the point to be predicted; e is the control weight w i The parameter of the rate of change; the larger e is, the larger w i Follow x i The rate of decrease increases as the distance from x increases.

4. The multi-distributed power supply island protection method according to claim 3 is characterized in that: The e is set to 0.

001.

5. The multi-distributed power supply island protection method according to claim 1, characterized in that: The determining whether the tracking frequency reaches a set condition includes: Determine whether the tracking frequency f1 is less than 49.5 Hz or greater than 49.5 Hz.

6. The multi-distributed power supply island protection method according to claim 1, characterized in that: The calculating the slope of the frequency fitting curve comprises: Deriving the frequency fitting curve to obtain the slope of the frequency fitting curve; The absolute value of the slope of the frequency fitting curve is calculated, and a threshold value is determined for the absolute value.

7. The multi-distributed power supply island protection method according to claim 6, characterized in that: The step of judging whether the slope of the frequency fitting curve exceeds a set threshold according to the threshold, and judging that an island occurs if the slope exceeds the set threshold, includes: It is determined whether the absolute value of the slope of the frequency fitting curve is greater than 2, and if so, it is determined that an island occurs.

8. A multi-distributed power supply island protection device, characterized in that: Use of the method according to any one of claims 1 to 7, comprising: A synchronous frequency-locked loop unit, used to control the output frequency of the inverter using a synchronous frequency-locked loop control method using a dual second-order generalized integrator instead of a phase-locked loop, and to collect a tracking frequency generated by the synchronous frequency-locked loop; A frequency judgment unit, used to judge whether the tracking frequency reaches a set condition, and if so, it is determined that an island occurs and each distributed power source is cut off; A local weighted linear fitting unit, used for extracting the high-frequency harmonic components of the inverter using a high-pass filter and performing local weighted linear fitting to obtain a frequency fitting curve when the tracking frequency does not reach a set condition; The slope judgment unit is used to calculate the slope of the frequency fitting curve, and judge whether the slope of the frequency fitting curve exceeds the set threshold according to the threshold. If it exceeds, it is determined that an island occurs and each distributed power source is cut off.

9. A computer 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 method according to any one of claims 1 to 7 is implemented.

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

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