Anti-flow method and device of photovoltaic power supply system, terminal and storage medium

Abstract

The application provides a reverse current prevention method and device of a photovoltaic power supply system, a terminal and a storage medium. The method comprises the following steps: acquiring electric energy data of a low-voltage power grid in real time; subtracting the electric energy data at a previous moment from the electric energy data at a current moment to obtain an electric energy difference; if the electric energy difference is greater than a first preset threshold, adjusting a photovoltaic inverter based on the electric energy difference to reduce the output power of the photovoltaic inverter; if the electric energy difference is greater than a second preset threshold, controlling the photovoltaic inverter to stop; and if the electric energy difference is greater than a third preset threshold, controlling a contactor to be disconnected. The first preset threshold is smaller than the second preset threshold, and the second preset threshold is smaller than the third preset threshold. Through the above scheme, the application can perform hierarchical reverse current prevention control according to the size of a local load surge, thereby improving the reverse current prevention response speed and guaranteeing the interests of photovoltaic power generation users.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power supply technology, and in particular to a method, device, terminal and storage medium for preventing reverse current in a photovoltaic power supply system. Background Technology

[0002] Photovoltaic power generation is a technology that directly converts light energy into electrical energy using the photovoltaic effect at semiconductor interfaces. To save on electricity bills, many users employ photovoltaic systems to supply power to their local loads. In this case, the power supply circuit diagram is as follows: Figure 1 As shown, the photovoltaic modules are connected to the low-voltage grid and the local load through the photovoltaic inverter. When the local load suddenly drops in power, the output power of the photovoltaic modules will flow back to the grid, causing the grid current to flow backward.

[0003] Currently, the common method in this field to prevent reverse current is to adjust the output power of the photovoltaic inverter when the load suddenly drops. However, this method has a slow response speed and the effect of preventing reverse current is not ideal. Summary of the Invention

[0004] In view of this, the present invention provides a method, device, terminal and storage medium for preventing reverse current in a photovoltaic power supply system, which can solve the problem of slow response speed in the prior art.

[0005] In a first aspect, embodiments of the present invention provide a method for preventing reverse current in a photovoltaic power supply system, the photovoltaic power supply system including a photovoltaic inverter and a contactor; the photovoltaic inverter is connected to a first end of the contactor, and the second end of the contactor is used to connect to a low-voltage power grid and a local load, respectively;

[0006] The method includes:

[0007] Real-time acquisition of power data from the low-voltage power grid side;

[0008] The difference in electrical energy is obtained by subtracting the electrical energy data at the current moment from the electrical energy data at the previous moment.

[0009] If the power difference is greater than a first preset threshold, the photovoltaic inverter is adjusted based on the power difference to reduce the output power of the photovoltaic inverter.

[0010] If the power difference is greater than the second preset threshold, the photovoltaic inverter is controlled to shut down.

[0011] If the energy difference is greater than a third preset threshold, then the contactor is controlled to disconnect.

[0012] The first preset threshold is less than the second preset threshold, and the second preset threshold is less than the third preset threshold.

[0013] Secondly, embodiments of the present invention provide an anti-reverse current device for a photovoltaic power supply system, the photovoltaic power supply system including a photovoltaic inverter and a contactor; the photovoltaic inverter is connected to a first end of the contactor, and the second end of the contactor is used to connect to a low-voltage power grid and a local load, respectively.

[0014] The device includes:

[0015] The power data acquisition module is used to acquire power data from the low-voltage power grid side in real time.

[0016] The difference calculation module is used to subtract the current energy data from the previous energy data to obtain the energy difference.

[0017] The first anti-reverse current module is used to adjust the photovoltaic inverter based on the power difference if the power difference is greater than a first preset threshold, so as to reduce the output power of the photovoltaic inverter.

[0018] The second anti-reverse current module is used to control the photovoltaic inverter to shut down if the power difference is greater than a second preset threshold.

[0019] The third anti-reverse current module is used to control the contactor to disconnect if the power difference is greater than a third preset threshold.

[0020] The first preset threshold is less than the second preset threshold, and the second preset threshold is less than the third preset threshold.

[0021] Thirdly, embodiments of the present invention provide a terminal, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method as described in any possible implementation of the first aspect above.

[0022] Fourthly, embodiments of the present invention provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method as described in any possible implementation of the first aspect above.

[0023] The beneficial effects of this invention compared to existing technologies are as follows: This invention acquires the power data from the low-voltage grid side; subtracts the current power data from the previous moment's power data to obtain a power difference; if the power difference is greater than a first preset threshold, the photovoltaic inverter is adjusted based on the power difference to reduce its output power; if the power difference is greater than a second preset threshold, the photovoltaic inverter is shut down; if the power difference is greater than a third preset threshold, the contactor is disconnected; the first preset threshold is less than the second preset threshold, and the second preset threshold is less than the third preset threshold. Through the above scheme, this embodiment can perform anti-reverse current control in stages according to the magnitude of the local load drop when the local load suddenly drops, thereby improving the anti-reverse current response speed and protecting the interests of photovoltaic power generation users. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a circuit connection diagram of the photovoltaic power supply system provided in an embodiment of the present invention;

[0026] Figure 2 This is a flowchart illustrating the implementation of the anti-reverse current method for a photovoltaic power supply system provided in this embodiment of the invention.

[0027] Figure 3 This is a schematic diagram of the anti-reverse current device of the photovoltaic power supply system provided in an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the terminal provided in an embodiment of the present invention. Detailed Implementation

[0029] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.

[0031] In this embodiment, as Figure 1 As shown, Figure 1 A circuit connection diagram of a photovoltaic power supply system is shown, such as... Figure 1 As shown, the photovoltaic power supply system includes photovoltaic modules, a photovoltaic inverter, and a contactor; the output terminal of the photovoltaic module is connected to the first terminal of the photovoltaic inverter, the second terminal of the photovoltaic inverter is connected to the first terminal of the contactor, and the second terminal of the contactor is used to connect to the low-voltage power grid and the local load, respectively.

[0032] Specifically, the execution subject (terminal) in this embodiment is Figure 1 The hierarchical backflow prevention controller in the hierarchical backflow prevention control cabinet is connected to both the photovoltaic inverter and the contactor. The contactor can be located within the hierarchical backflow prevention control cabinet.

[0033] like Figure 2 As shown, Figure 2 The implementation process of a reverse current prevention method for a photovoltaic power supply system is shown, and the process is detailed below:

[0034] S101: Real-time acquisition of power data from the low-voltage grid side.

[0035] In this embodiment, the electrical energy data can be either power or current. When the electrical energy data is power, Figure 2 The specific implementation process of S101 includes:

[0036] The voltage and current on the low-voltage grid side are acquired in real time.

[0037] Calculate the power on the low-voltage grid side based on the voltage and current on the low-voltage grid side.

[0038] In this embodiment, the hierarchical anti-reverse current controller obtains the voltage on the low-voltage grid side through a voltage transformer, collects the current on the low-voltage grid side through a current transformer, and then multiplies the voltage and current to obtain the power on the low-voltage grid side.

[0039] Specifically, under normal circumstances, both the photovoltaic inverter and the low-voltage grid serve as power sources to supply local loads. When the local load suddenly drops, the output power of the photovoltaic inverter remains unchanged, which will cause the output power of the photovoltaic inverter to be transmitted to the low-voltage grid. At this time, the low-voltage grid side is equivalent to another load of the photovoltaic inverter, causing the current on the low-voltage grid side to flow backward.

[0040] S102: Subtract the current energy data from the previous energy data to obtain the energy difference.

[0041] S103: If the power difference is greater than the first preset threshold, the photovoltaic inverter is adjusted based on the power difference to reduce the output power of the photovoltaic inverter.

[0042] To prevent the output power of the photovoltaic inverter from flowing to the low-voltage grid side and affecting the grid voltage, this embodiment monitors the power data of the low-voltage grid side in real time and subtracts the power data of the current moment from the power data of the previous moment to obtain the power difference. When the power difference between two adjacent moments is large, it is necessary to activate the graded anti-reverse flow control.

[0043] Specifically, when the difference in electrical energy between the current moment and the previous moment exceeds a first preset threshold, the hierarchical anti-reverse current controller controls the photovoltaic inverter to reduce its output power. The first preset threshold can be set by the user; when the electrical energy data is in power, the first preset threshold is also in power. The setting range of the first preset threshold can be 15KW-35KW. Preferably, the first preset threshold can be set to 20KW.

[0044] S104: If the power difference is greater than the second preset threshold, then control the photovoltaic inverter to shut down.

[0045] Specifically, the second preset threshold can also be set by the user. When the power data is power, the second preset threshold is also power. The setting range of the second preset threshold can be 45KW-70KW. Preferably, the second preset threshold can be set to 50KW.

[0046] In this embodiment, the second preset threshold is greater than the first preset threshold. When the power difference is greater than the second preset threshold, it indicates that the local load drops significantly and it is difficult to respond quickly by controlling the output power of the photovoltaic inverter. At this time, the photovoltaic inverter can be directly shut down to speed up the anti-reverse current control.

[0047] S105: If the energy difference is greater than the third preset threshold, then control the contactor to disconnect.

[0048] The first preset threshold is less than the second preset threshold, and the second preset threshold is less than the third preset threshold.

[0049] In this embodiment, the third preset threshold is greater than the second preset threshold. The third preset threshold can also be set by the user. When the power data is power, the third preset threshold is also power. The setting range of the third preset threshold can be 90KW-120KW. Preferably, the third preset threshold can be set to 100KW. When the power difference is greater than the third preset threshold, it indicates that the local load has suddenly dropped significantly. At this time, the photovoltaic side can be directly disconnected from the grid side by disconnecting the contactor, thereby achieving anti-reverse current control more quickly.

[0050] In this embodiment, when the power data is current, the first preset threshold, the second preset threshold, and the third preset threshold are all current values, and the magnitude of the current values ​​of the first preset threshold, the second preset threshold, and the third preset threshold can be set based on user needs.

[0051] As can be seen from the above embodiments, this embodiment of the invention obtains the power data from the low-voltage grid side; subtracts the power data from the previous moment's power data to obtain a power difference; if the power difference is greater than a first preset threshold, the photovoltaic inverter is adjusted based on the power difference to reduce its output power; if the power difference is greater than a second preset threshold, the photovoltaic inverter is shut down; if the power difference is greater than a third preset threshold, the contactor is disconnected; the first preset threshold is less than the second preset threshold, and the second preset threshold is less than the third preset threshold. Through this scheme, this embodiment can perform anti-reverse current control in stages according to the magnitude of the local load drop when the local load suddenly decreases, thereby improving the anti-reverse current response speed and protecting the interests of photovoltaic power generation users.

[0052] In one embodiment, the specific implementation process of S103 includes:

[0053] If the power difference is greater than the first preset threshold, a power reduction command is generated based on the power difference and sent to the photovoltaic inverter through a digital communication interface, so that the photovoltaic inverter adjusts the duty cycle of its internal switching transistors to reduce the output power of the photovoltaic inverter.

[0054] In this embodiment, the data communication interface can be an RS485 communication interface. When the power difference is greater than the first preset threshold, the hierarchical anti-reverse current controller sends a power reduction command to the photovoltaic inverter through the RS485 communication interface. After receiving the power reduction command, the photovoltaic inverter reduces the duty cycle of the switching transistor drive signal according to the power reduction command, thereby reducing the output power of the photovoltaic inverter.

[0055] Specifically, the power reduction command is generated based on the power difference and is used to adjust the output power of the photovoltaic inverter to a range that does not exceed the local load.

[0056] In one embodiment, Figure 2 The specific implementation process of S104 includes:

[0057] If the power difference is greater than the second preset threshold, the photovoltaic inverter will be shut down via dry contact control.

[0058] The dry contact mentioned in this embodiment is used to control the start and stop of the photovoltaic inverter. Since the dry contact communication method has a faster response speed than the digital communication method, the dry contact is used to control the photovoltaic inverter to stop when the power difference is greater than the second preset threshold. This can achieve anti-reverse current control more quickly and prevent the photovoltaic output power from being transmitted to the grid.

[0059] In one embodiment, the photovoltaic inverter includes multiple units; Figure 2 Another implementation process for S104 includes:

[0060] If the energy difference is greater than the second preset threshold, then a first quantity is determined based on the energy difference;

[0061] The first number of photovoltaic inverters are shut down by controlling the dry contact.

[0062] In one embodiment of the present invention, when there are many photovoltaic inverters, both the anti-reverse current control method corresponding to the first preset threshold and the anti-reverse current control method corresponding to the second preset threshold require calculation processing to control the photovoltaic inverters, resulting in a slow response speed. Furthermore, when the power difference exceeds the third preset threshold, it indicates an extremely severe local load drop, requiring immediate disconnection of the photovoltaic power generation system from the low-voltage grid. Therefore, in this case, the connection can be directly switched off by disconnecting the contactor. Figure 2 Multiple photovoltaic inverters on the right side are disconnected from the low-voltage grid side, thereby enabling a rapid response to anti-reverse current control and ensuring that the output power of the photovoltaic inverters is not transmitted to the low-voltage grid. This ensures both voltage stability on the low-voltage grid side and protects the interests of photovoltaic power generation users.

[0063] In one embodiment, the power data includes power, and the power difference includes power difference; after S104, the method provided in this embodiment further includes:

[0064] The photovoltaic inverter is controlled to start and increase its output power from zero until a target power is reached. The target power is obtained by subtracting the power difference from the first power. The first power is the output power of the photovoltaic inverter before the contactor is disconnected.

[0065] In one embodiment, the power data includes power, and the power difference includes power difference; after S105, the method provided in this embodiment further includes:

[0066] Close the contactor;

[0067] The photovoltaic inverter is controlled to start and increase its output power from zero until a target power is reached. The target power is obtained by subtracting the power difference from the first power. The first power is the output power of the photovoltaic inverter before the contactor is disconnected.

[0068] This embodiment, through the above method, can ensure the power generation efficiency of the photovoltaic power generation system while preventing backflow, and avoid the waste of electrical energy, thereby further protecting the interests of photovoltaic power generation users.

[0069] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0070] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above.

[0071] Figure 3 A schematic diagram of the anti-reverse current device for a photovoltaic power supply system provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below:

[0072] like Figure 3 As shown, the photovoltaic power supply system includes a photovoltaic inverter and a contactor; the photovoltaic inverter is connected to the first end of the contactor, and the second end of the contactor is used to connect to the low-voltage grid and the local load, respectively; the anti-reverse current device 100 of the photovoltaic power supply system includes:

[0073] The power data acquisition module 110 is used to acquire power data from the low-voltage power grid side in real time.

[0074] The difference calculation module 120 is used to subtract the current energy data from the previous energy data to obtain the energy difference.

[0075] The first anti-reverse current module 130 is used to adjust the photovoltaic inverter based on the power difference if the power difference is greater than a first preset threshold, so as to reduce the output power of the photovoltaic inverter.

[0076] The second anti-reverse current module 140 is used to control the photovoltaic inverter to shut down if the power difference is greater than a second preset threshold.

[0077] The third anti-backflow module 150 is used to control the contactor to disconnect if the power difference is greater than a third preset threshold.

[0078] The first preset threshold is less than the second preset threshold, and the second preset threshold is less than the third preset threshold.

[0079] In one embodiment, the first anti-backflow module 130 is specifically used for:

[0080] If the power difference is greater than the first preset threshold, a power reduction command is generated based on the power difference and sent to the photovoltaic inverter through a digital communication interface, so that the photovoltaic inverter adjusts the duty cycle of its internal switching transistors to reduce the output power of the photovoltaic inverter.

[0081] In one embodiment, the second anti-backflow module 140 is specifically used for:

[0082] If the power difference is greater than the second preset threshold, the photovoltaic inverter will be shut down via dry contact control.

[0083] In one embodiment, the photovoltaic inverter includes multiple inverters; the second anti-reverse current module 140 is specifically used for:

[0084] If the energy difference is greater than the second preset threshold, then a first quantity is determined based on the energy difference;

[0085] The first number of photovoltaic inverters are shut down by controlling the dry contact.

[0086] In one embodiment, the power data includes power, and the power data acquisition module 110 includes:

[0087] The voltage and current on the low-voltage grid side are acquired in real time.

[0088] Calculate the power on the low-voltage grid side based on the voltage and current on the low-voltage grid side.

[0089] In one embodiment, the power data includes power, and the power difference includes power difference; the anti-reverse current device 100 of the photovoltaic power supply system further includes a first inverter recovery module, used for:

[0090] The photovoltaic inverter is controlled to start and increase its output power from zero until a target power is reached. The target power is obtained by subtracting the power difference from the first power. The first power is the output power of the photovoltaic inverter before the contactor is disconnected.

[0091] In one embodiment, the power data includes power, and the power difference includes power difference; the anti-reverse current device 100 of the photovoltaic power supply system further includes a second inverter recovery module, used for:

[0092] Close the contactor;

[0093] The photovoltaic inverter is controlled to start and increase its output power from zero until a target power is reached. The target power is obtained by subtracting the power difference from the first power. The first power is the output power of the photovoltaic inverter before the contactor is disconnected.

[0094] As can be seen from the above embodiments, this embodiment of the invention obtains the power data from the low-voltage grid side; subtracts the power data from the previous moment's power data to obtain a power difference; if the power difference is greater than a first preset threshold, the photovoltaic inverter is adjusted based on the power difference to reduce its output power; if the power difference is greater than a second preset threshold, the photovoltaic inverter is shut down; if the power difference is greater than a third preset threshold, the contactor is disconnected; the first preset threshold is less than the second preset threshold, and the second preset threshold is less than the third preset threshold. Through this scheme, this embodiment can perform anti-reverse current control in stages according to the magnitude of the local load drop when the local load suddenly decreases, thereby improving the anti-reverse current response speed and protecting the interests of photovoltaic power generation users.

[0095] Figure 4 This is a schematic diagram of a terminal provided in an embodiment of the present invention. For example... Figure 4 As shown, the terminal 4 in this embodiment includes: a processor 40, a memory 41, and a computer program 42 stored in the memory 41 and executable on the processor 40. When the processor 40 executes the computer program 42, it implements the steps in the above-described embodiments of the anti-reverse current method for various photovoltaic power supply systems, for example... Figure 2 Steps 101 to 105 are shown. Alternatively, when the processor 40 executes the computer program 42, it implements the functions of each module / unit in the above-described device embodiments, for example... Figure 3 The functions of units 110 to 150 shown.

[0096] For example, the computer program 42 may be divided into one or more modules / units, which are stored in the memory 41 and executed by the processor 40 to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program 42 in the terminal 4.

[0097] The terminal 4 may include, but is not limited to, a processor 40 and a memory 41. Those skilled in the art will understand that... Figure 4 This is merely an example of terminal 4 and does not constitute a limitation on terminal 4. It may include more or fewer components than shown, or combine certain components, or different components. For example, the terminal may also include input / output devices, network access devices, buses, etc.

[0098] The processor 40 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0099] The memory 41 can be an internal storage unit of the terminal 4, such as a hard disk or memory of the terminal 4. The memory 41 can also be an external storage device of the terminal 4, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the terminal 4. Furthermore, the memory 41 can include both internal storage units and external storage devices of the terminal 4. The memory 41 is used to store the computer program and other programs and data required by the terminal. The memory 41 can also be used to temporarily store data that has been output or will be output.

[0100] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0101] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0102] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0103] In the embodiments provided by this invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0104] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0105] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0106] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the anti-reverse current method embodiments of the various photovoltaic power supply systems described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc. It should be noted that the content contained in the computer-readable medium may be appropriately added to or subtracted from the content as required by the legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium may not include electrical carrier signals and telecommunication signals.

[0107] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method of preventing backflow in a photovoltaic power supply system, characterized by, The photovoltaic power supply system comprises a photovoltaic inverter and a contactor; the photovoltaic inverter is connected with a first end of the contactor, and a second end of the contactor is respectively used for connecting a low-voltage power grid and a local load; The method comprises: Real-time acquisition of the electric energy data on the low-voltage power grid side; Subtraction of the electric energy data at the previous moment from the electric energy data at the current moment to obtain an electric energy difference value; If the electric energy difference value is greater than a first preset threshold value, the photovoltaic inverter is adjusted based on the electric energy difference value and through a digital communication interface to reduce the output power of the photovoltaic inverter; If the electric energy difference value is greater than a second preset threshold value, the photovoltaic inverter is shut down through dry contact control; If the electric energy difference value is greater than a third preset threshold value, the contactor is controlled to be disconnected; The first preset threshold value is less than the second preset threshold value, and the second preset threshold value is less than the third preset threshold value.

2. The method of claim 1, wherein the photovoltaic power supply system is a system for preventing reverse current flow of a photovoltaic power supply system, and the controller is a controller for preventing reverse current flow of a photovoltaic power supply system. If the electric energy difference value is greater than the first preset threshold value, a power reduction instruction is generated based on the electric energy difference value, and the power reduction instruction is sent to the photovoltaic inverter through a digital communication interface to make the photovoltaic inverter adjust the duty cycle of an internal switch tube to reduce the output power of the photovoltaic inverter. The photovoltaic inverter comprises a plurality of 3. The method of claim 1, wherein the method further comprises: If the electric energy difference value is greater than the second preset threshold value, a first number is determined according to the electric energy difference value; A first number of photovoltaic inverters are shut down through dry contact control. The electric energy data comprises power, and the electric energy difference value comprises a power difference value; after the photovoltaic inverter is controlled to be shut down if the electric energy difference value is greater than the second preset threshold value, the method further comprises: The photovoltaic inverter is controlled to be started and to increase the output power from zero until a target power is reached, the target power being obtained by subtracting the power difference value from a first power; the first power is the output power of the photovoltaic inverter before the contactor is disconnected.

4. The method for preventing reverse current in a photovoltaic power supply system according to claim 1, characterized in that, The electric energy data comprises power, and the electric energy difference value comprises a power difference value; after the contactor is controlled to be disconnected if the electric energy difference value is greater than the third preset threshold value, the method further comprises: The contactor is closed; 5. The method for preventing reverse current in a photovoltaic power supply system according to claim 1, characterized in that, The photovoltaic inverter is controlled to be started and to increase the output power from zero until a target power is reached, the target power being obtained by subtracting the power difference value from a first power; the first power is the output power of the photovoltaic inverter before the contactor is disconnected. The electric energy data comprises power, and the real-time acquisition of the electric energy data on the low-voltage power grid side comprises: Real-time acquisition of the voltage and current on the low-voltage power grid side; 6. The method for preventing reverse current in a photovoltaic power supply system according to claim 1, characterized in that, Calculation of the power on the low-voltage power grid side according to the voltage and current on the low-voltage power grid side. The photovoltaic power supply system comprises a photovoltaic inverter and a contactor; the photovoltaic inverter is connected with a first end of the contactor, and a second end of the contactor is respectively used for connecting a low-voltage power grid and a local load; The device comprises:

7. A reverse current prevention device for a photovoltaic power supply system, characterized by comprising: ​ ​ An electric energy data acquisition module is configured to acquire electric energy data of the low-voltage power grid in real time. A difference calculation module is configured to subtract the electric energy data at a current time from the electric energy data at a previous time to obtain an electric energy difference. A first anti-reverse flow module is configured to, if the electric energy difference is greater than a first preset threshold, adjust the photovoltaic inverter based on the electric energy difference and through a digital communication interface to reduce the output power of the photovoltaic inverter. A second anti-reverse flow module is configured to, if the electric energy difference is greater than a second preset threshold, control the photovoltaic inverter to shut down through dry contact. A third anti-reverse flow module is configured to, if the electric energy difference is greater than a third preset threshold, control the contactor to be disconnected. The first preset threshold is less than the second preset threshold, and the second preset threshold is less than the third preset threshold.

8. A terminal comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, The processor executes the computer program to implement the steps of the method of any one of claims 1-6.

9. A computer-readable storage medium storing a computer program, the computer program comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 8. The computer program is executed by the processor to implement the steps of the method of any one of claims 1-6.

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