Island detection system and method when multiple inverters are operated in parallel

Abstract

The present application provides an island detection system and method when multiple inverters are running in parallel. The multiple inverters include at least a first inverter and a second inverter connected in parallel. The island detection system includes: a current detection circuit, which is arranged on the grid side or the AC side of the second inverter; and a controller, which is connected to the current detection circuit and the first inverter respectively; the controller determines whether to perform distributed island detection or centralized island detection on the first inverter and the second inverter according to the grid voltage signal and the current detection signal of the current detection circuit. The present invention identifies the island detection model of the second inverter through the controller, matches it with the typical island detection model in the pre-set model library, and determines whether to perform distributed or centralized island detection according to the matching result, thereby improving the success rate of island detection.

Description

Technical Field

[0001] The present invention relates to the field of island detection, and in particular to an island detection system and method when multiple inverters are operated in parallel. Background Art

[0002] In the renewable energy power generation system, an inverter is usually used to convert electrical energy into AC power, and the output end of the inverter is connected to the load and the grid through a circuit breaker. When the grid is disconnected due to a fault or other reasons, the inverter and the local load will operate in an islanding state. The islanding operation state will pose a threat to inspection and maintenance, and needs to be detected and terminated under certain conditions. In the prior art, there are mainly active and passive methods for islanding operation state detection (referred to as "islanding detection"). The passive method mainly realizes islanding detection by monitoring parameters such as PCC point voltage and frequency, but passive islanding detection often has a relatively large non-detection zone (NDZ). As a supplement, active islanding detection is usually required. Common active islanding detection methods include active frequency offset, reactive power injection, harmonic injection, etc.

[0003] For island detection when multiple inverters are running in parallel, the common treatment measure is "same detection method + synchronous injection". That is, in a system with multiple inverters in parallel, all inverters use the same active island detection method. Generally, in order to ensure the synchronization of the injection action, a master controller needs to be designed in the system. The master controller can be an independent controller, or the controller of a certain inverter can be used as the master controller, and the controllers of other inverters can be used as slave controllers. The master controller and the slave controller are connected through communication. During island detection, the master controller outputs a synchronization reference signal and transmits it to each slave controller. After receiving the synchronization signal, the slave controller performs the island detection action. In order to reduce communication delay, a high-speed communication bus, such as CAN bus, is generally used. The implementation premise of this treatment measure is that each inverter uses the same island detection model, and the inverters need to establish high-speed (or real-time) communication to achieve accurate synchronization. If one inverter in the system uses a different model or the detection is not synchronized, the island detection of the entire system may fail, so the robustness of the algorithm is poor.

[0004] Furthermore, if the inverters in the system cannot achieve high-speed (or real-time) communication with each other, or even no communication at all, such as in a parallel system consisting of a photovoltaic energy storage inverter and an electric vehicle with bidirectional power interaction capability, the traditional parallel system island detection method is difficult to work in this type of application scenario.

[0005] Therefore, it is very necessary to find an island detection system and method when multiple inverters are operated in parallel without communication to solve one or more of the above-mentioned technical problems. Summary of the invention

[0006] In view of this, an object of the present invention is to provide an island detection system when multiple inverters are operating in parallel, which can adaptively perform distributed or centralized island detection for different situations by adding a current detection circuit on the grid side or the AC side of the second inverter, thereby improving the success rate of island detection.

[0007] In order to achieve the above object, the present invention provides an island detection system when multiple inverters are running in parallel, the multiple inverters at least include a first inverter and a second inverter connected in parallel, and the island detection system includes:

[0008] A first current detection circuit is provided on the grid side or the AC side of the second inverter; and

[0009] A controller, connected to the first current detection circuit and the first inverter respectively;

[0010] The controller determines the island detection model of the second inverter based on the current detection signal of the first current detection circuit and the grid voltage signal, and determines whether to perform distributed island detection or centralized island detection on the first inverter and the second inverter based on whether the island detection model matches the island detection model library.

[0011] The present invention also provides an island detection method when multiple inverters are running in parallel, wherein the multiple inverters include at least a first inverter and a second inverter connected in parallel, and the island detection method includes:

[0012] Sampling the grid voltage to obtain a grid voltage signal;

[0013] Sampling the current on the grid side or the AC side of the second inverter to obtain a current detection signal; and

[0014] An island detection model of the second inverter is determined according to the current detection signal and the grid voltage signal, and whether distributed island detection or centralized island detection is performed on the first inverter and the second inverter is determined according to whether the island detection model matches an island detection model library.

[0015] The present invention identifies the islanding detection model of the second inverter through a controller, matches it with a typical islanding detection model in a preset model library, and determines whether to perform distributed or centralized islanding detection based on the matching result, thereby improving the success rate of islanding detection.

[0016] The above description will be described in detail below with reference to implementation examples, and a further explanation will be provided for the technical solution of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to make the above and other objects, features, advantages and embodiments of the present invention more clearly understood, the accompanying drawings are described as follows:

[0018] Figure 1 A circuit diagram of an island detection system when multiple inverters are operated in parallel according to an embodiment of the present invention;

[0019] Figure 2 A simplified circuit diagram of an island detection system when multiple inverters are operated in parallel according to another embodiment of the present invention;

[0020] Figure 3 An island detection model based on reactive current injection according to an embodiment of the present invention;

[0021] Figure 4 is a flow chart of an island detection method when multiple inverters are operated in parallel according to an embodiment of the present invention;

[0022] Figure 5 A flowchart of centralized island detection according to an embodiment of the present invention;

[0023] Figure 6 A distributed island detection flow chart according to an embodiment of the present invention;

[0024] Figure 7 A schematic diagram of a distributed island detection model based on synchronous injection according to an embodiment of the present invention;

[0025] Figure 8 A schematic diagram of a distributed island detection model based on time-sharing injection according to an embodiment of the present invention;

[0026] Fig. 9 A distributed island detection flow chart according to another embodiment of the present invention;

[0027] Fig.10 Schematic diagram of a distributed island detection model based on adversarial injection according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the description of the present invention more detailed and complete, reference may be made to the attached drawings and the various embodiments below, in which the same numbers represent the same or similar components. On the other hand, well-known components and steps are not described in the embodiments to avoid unnecessary limitations on the present invention. In addition, in order to simplify the drawings, some known and commonly used structures and elements will be depicted in the drawings in a simple schematic manner.

[0029] According to a preferred embodiment of the present invention, see Figure 1-2, provides an island detection system when multiple inverters are running in parallel, comprising at least a first inverter 131 and a second inverter 170 connected in parallel. The island detection system also includes: a current detection circuit 140 (referred to as a first current detection circuit) and a controller 132. The first current detection circuit 140 can be arranged on the grid side or the AC side of the second inverter 170. The controller 132 is connected to the first current detection circuit 140 and the first inverter 131, respectively. The controller 132 determines whether to perform distributed island detection or centralized island detection on the first inverter 131 and the second inverter 170 based on a grid voltage signal obtained by sampling the grid voltage and a current detection signal detected by the first current detection circuit 140.

[0030] Specifically, see Figure 1 , which shows a circuit diagram of an island detection system when multiple inverters are running in parallel according to a preferred embodiment of the present invention. The system may include: a first DC source 110, a second DC source 120, an inverter system 130, a local load 190, a power grid 150, a third DC source 160, a second inverter 170, a first current detection circuit 140, and a connector 180. In some embodiments, the first DC source 110, such as a photovoltaic panel, is connected to the first inverter 131. The second DC source 120, such as a household energy storage battery, is connected to the first inverter 131. The inverter system 130 is, for example, an energy storage inverter system. The third DC source 160, such as a vehicle battery, is connected to the second inverter 170. The second inverter 170 is, for example, a vehicle charger. The connector 180 may be a connector in the form of a charging gun or the like.

[0031] Specifically, taking a V2G (Vehicle to Grid) system as an example, the system includes electric vehicles, photovoltaic panels, energy storage batteries and energy storage inverters. Figure 1 , the first DC source 110 is a photovoltaic panel, the second DC source 120 is an energy storage battery, the third DC source is a power battery installed in an electric vehicle, the first inverter 131 is an energy storage inverter, the second inverter 170 is a bidirectional charger installed in an electric vehicle, the connector 180 is a charging gun integrated in the energy storage inverter, and the energy storage inverter is designed with an energy management system that can monitor the status and control the power of the energy storage battery and the power battery of the electric vehicle. It should be noted that each DC source and inverter can also be applied to other technical fields, and this case does not limit this.

[0032] The inverter system 130 may include a first inverter 131 , a controller 132 , a current detection circuit 133 (referred to as a second current detection circuit), and a circuit breaker 134 . Figure 1The first inverter 131, the controller 132, the second current detection circuit 133 and the circuit breaker 134 shown in the figure are discrete components. In other embodiments, the controller 132, the second current detection circuit 133 and the circuit breaker 134 can be integrated in the first inverter 131. It should be noted that the inverter system 130 itself needs to set a second current detection circuit 133 in order to realize control and island detection. The second current detection circuit 133 is set on the AC side of the first inverter 131. The second current detection circuit 133 is required to be set in the inverter system 130 itself, and it already exists in the existing hardware, so it will not be explained in detail here. In actual applications, in order to realize the island detection of multiple inverters in parallel in this application, it is necessary to additionally set a first current detection circuit 140 in the system. In this embodiment, as Figure 1 As shown, the first current detection circuit 140 is arranged on the output side of the second inverter 170, for example, it can be arranged before and after the connector 180; in other embodiments, the first current detection circuit 140 is arranged on the common output side of the first inverter 131 and the second inverter 170, that is, the grid side. The second current detection circuit 133 and the first current detection circuit 140 can be current sensors CT, and the current detection signal sampled by the current sensor CT is input into the controller. Further, the inverter system 130 also includes a voltage detection circuit (not shown in the figure) for sampling the grid voltage and inputting the grid voltage signal into the controller. The controller 132 completes the identification of the island detection model of the second inverter 170 and / or the adjustment of the island detection model of the first inverter 131 itself by processing the sampled signals (for example, the current detection signal and the grid voltage signal).

[0033] Furthermore, the controller 132 is electrically connected to the first inverter 131, and transmits a control signal to the first inverter 131, so as to control the normal working state of the first inverter 131, and detect and perform subsequent actions of the first inverter 131. The controller 132 also controls the circuit breaker 134, and disconnects the system from the load 190 after detecting the occurrence of an island.

[0034] See also Figure 2 , which shows that according to the present invention Figure 1 The simplified circuit diagram of the island detection system when multiple inverters are operated in parallel is shown in FIG. The first current detection circuit 140 is arranged at the output end of the second inverter 170. In other embodiments, the first current detection circuit 140 can also be arranged on the grid side, and the effect is equivalent.

[0035] in, Figure 3 An island detection model based on reactive current injection according to an embodiment of the present invention is shown. The working mechanism of the island detection model based on reactive current injection is as follows:

[0036] Step 1: Periodically inject reactive current Iq at the output side of the inverter.

[0037] Step 2: Calculate the output frequency according to the grid voltage signal. When the output frequency changes, enter the enhanced injection mode and increase the reactive current injection intensity. When the injection intensity increases to a certain value, stop the injection and observe the output frequency.

[0038] Step 3: When the output frequency observed in step 2 meets Figure 3 When a pattern is observed in the , it is recorded as an event.

[0039] Step 4: When the event in the figure is detected to occur several times in succession, it is determined that an island occurs.

[0040] It should be noted that, in practice, the island detection model includes but is not limited to the above-mentioned reactive current injection method, and may also be other methods, which are not limited to this case. The following will take reactive current injection as an example to describe the island detection when multiple inverters are running in parallel.

[0041] Figure 4 The flowchart of a method for detecting an islanding when multiple inverters are operated in parallel according to an embodiment of the present disclosure is schematically shown. Figure 4 As shown, it mainly includes:

[0042] Step S10: sampling the grid voltage to obtain a grid voltage signal; sampling the current on the grid side or the current on the AC side of the second inverter to obtain a current detection signal.

[0043] Step S20: fitting an islanding detection model of the second inverter according to the current detection signal and the grid voltage signal.

[0044] Step S30: Determine whether the island detection model matches the island detection model library.

[0045] In some embodiments, the current detection signal sampled by the first current detection circuit 140 and the grid voltage signal sampled by the voltage detection circuit are input into the controller 132. The controller 132 fits the island detection model of the second inverter 170 according to the current detection signal and the grid voltage signal. Specifically, the controller 132 can obtain the electrical parameters of the second inverter 170 according to the sampled signal, including voltage, current, active power, reactive power, frequency and other information. The controller 132 completes the analysis and extraction of key features of the island detection model of the second inverter 170 by obtaining a large number of electrical parameters of the second inverter 170, including disturbance type (such as frequency offset, reactive power injection, harmonic injection, etc.), disturbance period, disturbance amplitude, etc. The controller 132 fits the island detection model of the second inverter 170 according to the extracted features. Among them, the fitting of the island detection model of the second inverter 170 can be based on a large amount of sampled data (such as a large amount of historical sampled data), including the current detection signal and the grid voltage signal sampled in the current cycle. The island detection model of the second inverter 170 may be fitted by a fitting method in the prior art or by a machine learning method, which is not limited in the present case.

[0046] In some embodiments, the controller 132 determines whether the island detection model matches the island detection model library according to the island detection model, and performs distributed island detection or centralized island detection respectively. Among them, the controller 132 stores a model library, which contains several typical island detection models. The controller 132 compares and analyzes the island detection model of the fitted second inverter 170 with the model in the model library. If a certain degree of overlap is met with a certain model, the match is successful, otherwise the match fails.

[0047] Further, if there is no match, execute step S40; if there is a match, execute step S50.

[0048] Step S40: performing centralized island detection.

[0049] Step S50: Execute distributed island detection.

[0050] If the island detection model matches the island detection model library, distributed island detection is performed; in the distributed island detection, the first inverter 131 and the second inverter 170 connected in parallel each independently perform island detection.

[0051] If the island detection model does not match the island detection model library, centralized island detection is performed; in the centralized island detection, the first inverter 131 and the second inverter 170 are taken as a whole, and centralized island detection is performed through the first inverter 131 .

[0052] Specifically, in centralized island detection, the controller 132 compensates the control signal used to detect the island operation status of the first inverter 131 in real time according to the current detection signal, that is, compensates the island detection control signal of the first inverter 131 in real time, and outputs the compensated control signal to the first inverter 131.

[0053] Figure 5 The flowchart of centralized island detection according to one embodiment of the present invention may include the following steps:

[0054] Step S401: Acquire parameters of the second inverter according to the grid voltage signal and the current detection signal.

[0055] Exemplarily, the controller 132 may obtain parameters of the second inverter 170 according to the sampled current detection signal and the grid voltage signal, including information such as voltage, current, active power, reactive power, frequency or harmonics.

[0056] Step S402: Determine whether the second inverter is performing islanding detection. If yes, execute step S403, otherwise execute step S404.

[0057] Step S403: calculating a compensation amount of the islanding detection control signal of the first inverter according to the parameters of the islanding detection model of the second inverter.

[0058] Step S404: updating the islanding detection control signal of the first inverter.

[0059] Taking the above island detection method of injecting reactive current as an example, it is assumed that at a certain moment, when the influence of the second inverter 170 is not considered, the island detection control signal to be injected by the first inverter 131 is, for example, a reactive current of 1A. At this time, the judgment result of step S402 is "yes", that is, the second inverter 170 is performing island detection. At the same time, according to the sampling signal, for example, it is calculated that the second inverter 170 is injecting a reactive current of 0.5A, and a compensation amount is calculated accordingly, and its value is -0.5A. The island detection control signal of the first inverter 131 is updated according to the compensation amount, and its value is (1+(-0.5)=0.5A. The first inverter 131 performs island detection according to the updated island detection control signal. Similarly, if it is calculated that the second inverter 170 is injecting a reactive current of -0.5A, the compensation amount is 0.5A, and the updated island detection control signal of the first inverter is (1+(0.5))=1.5A. Here, the reactive current is taken as an example for specific description, but it is not limited to this electrical parameter, for example, it can also be the amount of injected harmonics. If the result of step S402 is "No", the first inverter can update the control signal according to its own island detection model.

[0060] Figure 6FIG. 1 is a flow chart of distributed island detection according to an embodiment of the present invention. Figure 6 As shown, including:

[0061] Step S501: loading parameters of an islanding detection model of a second inverter.

[0062] Step S502: configuring the islanding detection model of the first inverter to be the same as that of the second inverter.

[0063] Step S503: Determine whether synchronization is required.

[0064] If synchronization is required, execute step S504; if synchronization is not required, execute step S505.

[0065] Step S504: adopting the synchronous injection mode.

[0066] Step S505: adopting a time-sharing injection mode.

[0067] Similarly, the controller 132 loads the parameters of the islanding detection model of the second inverter 170 , including information such as disturbance type, injection period, and injection amplitude.

[0068] Specifically, after acquiring the islanding detection model of the inverter 132 , the controller 132 configures the first inverter 131 to use the same islanding detection model as the second inverter 170 , and controls the islanding detection control signal of the first inverter 131 to be synchronous or asynchronous with the second inverter 170 in timing.

[0069] For further information, see Figure 7 , which shows the schematic diagram of different inverter island detection models under synchronous injection mode. Taking reactive current injection as an example, see Figure 7 , if the island detection model of the second inverter 170 is fitted, for example, the injected reactive current law is as follows Figure 7 As shown in the second inverter Iq, the frequency changes when islanding occurs as follows Figure 7 The first inverter 131 is configured to load the island detection model of the second inverter 170, and the first inverter 131 uses the same model to periodically inject reactive current, the injection time is synchronized with the second inverter 170, and the injection amplitude is consistent with the second inverter 170. The purpose of this design is to make the injection signals of the two inverters form a superposition effect and improve the island detection speed.

[0070] In some embodiments, when the time-sharing injection mode is adopted, the first inverter uses the same island detection model as the second inverter, but its control command is strictly staggered in timing with the second inverter to ensure that the island detections between them will not affect each other.

[0071] For further information, see Figure 8 , which shows the schematic diagram of different inverter island detection models under time-sharing injection mode. Taking reactive injection as an example, see Figure 8 , the island detection model of the second inverter 170, that is, the injected reactive current law is as follows Figure 8 As shown in the second inverter Iq, when an island occurs, the frequency changes as follows Figure 8 The controller 132 configures the first inverter 131 to load the island detection model of the second inverter 170, so that the first inverter 131 also periodically injects reactive current, but the injection action in each cycle is completed within the interval when the second inverter 170 is not disturbed. The purpose of this design is to achieve independent island detection of the two inverters without interfering with each other.

[0072] In some other embodiments, a counter-injection mode may be used. Fig. 9 As shown, including:

[0073] Step S701: Acquire parameters of an islanding detection model of a second inverter.

[0074] Step S702: configuring the islanding detection model of the first inverter to be symmetrical with that of the second inverter.

[0075] Step S703: adopting the anti-injection mode.

[0076] The first inverter 131 is configured to use an island detection model symmetrical to the second inverter 170, presenting an antagonistic relationship of one increasing while the other decreases, and the detection cycle and time of the first inverter 131 are synchronized with the second inverter 170, so that the sum of the control signals of the two remains constant.

[0077] For further information, see Fig.10 , which shows a schematic diagram of different inverter island detection models under synchronous injection mode. Taking reactive current injection as an example, if the island detection model of the second inverter 170 is fitted, its rule is as follows Fig.10 As shown in the second inverter Iq, the frequency changes when islanding occurs as follows Fig.10 As shown in the second inverter f in FIG. 1 . The controller 132 configures the first inverter 131 to load the symmetrical island detection model of the second inverter 170. The first inverter 131 also periodically injects reactive current, and the injection time is synchronized with the second inverter 170, but its injection amplitude forms a confrontation mode with the second inverter 170, keeping the total reactive current injection amount constant. That is, the injection amplitude of the first inverter 131 is configured to decrease as the injection amplitude of the second inverter 170 increases. The purpose of this design is to make the injection signals of the two inverters form a superposition effect, but to control the total injection amount and improve the island detection speed.

[0078] It can be understood that one of the three injection modes, namely synchronous injection, time-sharing injection and confrontation injection, can be selected as required.

[0079] Preferably, in the distributed island detection, the controller 132 configures the island detection model of the first inverter 131 to be the same as the island detection model of the second inverter 170, and the controller 132 applies the island detection control signal to the first inverter 131 in a synchronous injection or time-sharing injection manner relative to the second inverter 170, that is, the island detection control signal corresponding to the island detection model is applied to the first inverter 131. Alternatively, the controller 132 configures the island detection model of the first inverter 131 to be symmetrical with the island detection model of the second inverter 170, and the controller 132 applies the island detection control signal to the first inverter 131 in a counter-injection manner relative to the second inverter 170, that is, the island detection control signal corresponding to the island detection model is applied to the first inverter 131.

[0080] The present invention identifies the islanding detection model of the second inverter through a controller, matches it with a typical islanding detection model in a preset model library, and determines whether to perform distributed or centralized islanding detection based on the matching result, thereby improving the success rate of islanding detection.

[0081] Furthermore, the multi-inverter parallel island detection system of the present application has a simple structure and does not require the establishment of a complex real-time communication network; and the matching is simple. The system of the present application is theoretically applicable to any second inverter, and the second inverter does not require any design changes (including hardware and software).

[0082] At the same time, in centralized island detection, the control signal used to detect the island operation status of the first inverter is compensated in real time to reduce the interference of the second inverter's island detection; in distributed island detection, synchronous injection, time-sharing injection or antagonistic injection are used to eliminate the island detection interference between different inverters.

[0083] Although the present invention has been disclosed as above in the form of an implementation method, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the attached claims.

Claims

1. An island detection system when multiple inverters are operated in parallel, wherein the multiple inverters include at least a first inverter and a second inverter connected in parallel, characterized in that The island detection system comprises: a first current detection circuit, arranged on the grid side or the AC side of the second inverter; and A controller, connected to the first current detection circuit and the first inverter respectively; The controller determines an island detection model of the second inverter based on a grid voltage signal and a current detection signal of the first current detection circuit, and determines whether to perform distributed island detection or centralized island detection on the first inverter and the second inverter based on whether the island detection model matches an island detection model library.

2. The island detection system according to claim 1, characterized in that: The controller is used for controlling the circuit breaker to disconnect the multi-inverter from the load after detecting the occurrence of the island operation state.

3. The island detection system according to any one of claims 1-2, characterized in that: The controller and the second current detection circuit are independently arranged or integrated in the first inverter.

4. The island detection system according to claim 1, characterized in that: If the island detection model matches the island detection model library, distributed island detection is performed; in the distributed island detection, the first inverter and the second inverter each independently perform island detection.

5. The island detection system according to claim 1, characterized in that: If the island detection model does not match the island detection model library, centralized island detection is performed; in the centralized island detection, the first inverter and the second inverter are taken as a whole, and centralized island detection is performed through the first inverter.

6. The island detection system according to claim 5, characterized in that: In centralized islanding detection, the controller compensates the islanding detection control signal of the first inverter in real time according to the current detection signal, and outputs the compensated islanding detection control signal to the first inverter.

7. The island detection system according to claim 4, characterized in that: In the distributed islanding detection, the controller configures the islanding detection model of the first inverter to be the same as the islanding detection model of the second inverter, and the controller applies an islanding detection control signal to the first inverter in a synchronous injection or time-sharing injection manner relative to the second inverter; Alternatively, the controller configures the islanding detection model of the first inverter to be symmetrical to the islanding detection model of the second inverter, and the controller applies the islanding detection control signal to the first inverter in a counter-injection manner relative to the second inverter.

8. The island detection system according to any one of claims 1-2, characterized in that: The DC side of the first inverter is connected to a first DC source and a second DC source.

9. The island detection system according to claim 8, characterized in that: The first DC source includes a photovoltaic panel, the second DC source includes a household energy storage battery, and the first inverter includes an energy storage inverter.

10. The island detection system according to any one of claims 1-2, characterized in that: The DC side of the second inverter is connected to a third DC source.

11. The island detection system according to claim 10, characterized in that: The third DC source includes a vehicle-mounted battery, and the second inverter includes a vehicle-mounted charger.

12. A method for detecting an islanding of multiple inverters in parallel, wherein the multiple inverters include at least a first inverter and a second inverter in parallel, characterized in that: The island detection method includes: Sampling the grid voltage to obtain a grid voltage signal; Sampling the current on the grid side or the AC side of the second inverter to obtain a current detection signal; and An island detection model of the second inverter is determined according to the current detection signal and the grid voltage signal, and whether distributed island detection or centralized island detection is performed on the first inverter and the second inverter is determined according to whether the island detection model matches an island detection model library.

13. The island detection method according to claim 12, characterized in that: After the island operation state is detected, the circuit breaker is controlled to disconnect the multi-inverter from the load.

14. The island detection method according to claim 12, characterized in that: If the island detection model matches the island detection model library, distributed island detection is performed; in the distributed island detection, the first inverter and the second inverter each independently perform island detection.

15. The island detection method according to claim 12, characterized in that: If the island detection model does not match the island detection model library, centralized island detection is performed; in the centralized island detection, the first inverter and the second inverter are taken as a whole, and centralized island detection is performed through the first inverter.

16. The island detection method according to claim 15, characterized in that: In the centralized islanding detection, the islanding detection control signal of the first inverter is compensated in real time according to the current detection signal, and the control signal obtained after compensation is output to the first inverter.

17. The island detection method according to claim 14, characterized in that: In distributed island detection, the first inverter uses the same island detection model as the second inverter, and applies an island detection control signal to the first inverter in a synchronous injection or time-sharing injection manner; or, the first inverter uses a symmetrical island detection model with the second inverter, and applies an island detection control signal to the first inverter in an antagonistic injection manner.

18. The island detection method according to any one of claims 12 to 13, characterized in that: The DC side of the first inverter is connected to a first DC source and a second DC source.

19. The island detection method according to claim 18, characterized in that: The first DC source includes a photovoltaic panel, the second DC source includes a household energy storage battery, and the first inverter includes an energy storage inverter.

20. The island detection method according to any one of claims 12 to 13, characterized in that: The DC side of the second inverter is connected to a third DC source.

21. The island detection method according to claim 20, characterized in that: The third DC source includes a vehicle-mounted battery, and the second inverter includes a vehicle-mounted charger.

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