Photovoltaic system and automatic on-off control method therefor
Patent Information
- Application Number
- PCT/CN2025/102255
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-04-14
- Filing Date
- 2025-06-20
- Publication Date
- 2026-10-22
Smart Images
Figure CN2025102255_22102026_PF_FP_ABST
Abstract
Description
Photovoltaic systems and their automatic on / off control methods
[0001] This application claims priority to Chinese Patent Application No. 202510460395.1, filed with the Chinese Patent Office on April 14, 2025, the entire contents of which are incorporated herein by reference. Technical Field
[0002] This application relates to the field of photovoltaic technology, and in particular to a photovoltaic system and its automatic on / off control method. Background Technology
[0003] Currently, the on / off control of existing photovoltaic (PV) systems mainly relies on external PLC signal transmitters. However, controlling the on / off of PV systems through external PLC signal transmitters has the following drawbacks: configuring PLC signal transmitters increases the complexity and cost of PV systems; the on / off control of PV systems via PLC communication by the PLC signal transmitters is susceptible to environmental interference (such as electromagnetic noise, changes in line impedance, etc.), which can lead to false or delayed triggering of the PV system's on / off control, reducing the accuracy of the PV system's on / off control; once the external PLC signal transmitters malfunction, the on / off control of the PV system will fail; in addition, the PLC signal transmitters need to be calibrated and troubleshooted regularly, resulting in relatively poor reliability of the PV system's on / off control. Summary of the Invention
[0004] This application provides a photovoltaic system and its automatic on / off control method, which can improve the accuracy and reliability of automatic on / off control of the photovoltaic system, and reduce the complexity and cost of automatic on / off control of the photovoltaic system.
[0005] In a first aspect, embodiments of this application provide an automatic on / off control method for a photovoltaic system. This method is applied to module-level photovoltaic equipment, each of which is connected to a photovoltaic module. The module-level photovoltaic equipment connected to the photovoltaic modules in the same photovoltaic string are connected to each other via a PLC communication link.
[0006] The automatic on / off control method for the photovoltaic system includes:
[0007] Collect the communication link parameters of the photovoltaic string and the current value of the photovoltaic module;
[0008] Based on the communication link parameters and the current value, determine the on / off state of the inverter's DC switch;
[0009] The voltage output of the photovoltaic module connected to the inverter is controlled according to the on / off state of the inverter DC switch, thereby controlling the on / off state of the photovoltaic system.
[0010] Optionally, the step of determining the on / off state of the inverter's DC switch includes:
[0011] A first on / off command is generated based on the communication link parameters, and the first on / off command is broadcast through the PLC communication link;
[0012] The received multiple first on / off commands and the generated first on / off commands are statistically analyzed, and a second on / off command is generated based on the statistical results.
[0013] A third on / off command is generated based on the current value of the photovoltaic module;
[0014] The on / off state of the inverter DC switch is determined according to the second on / off command and the third on / off command.
[0015] Optionally, the communication link parameters include the communication link impedance value and signal strength;
[0016] The first on / off command includes a first off command and a first on command;
[0017] The second on / off command includes a second off command and a second on command;
[0018] The third on / off command includes a third disconnect command and a third on command.
[0019] Optionally, generating the first on / off command based on the communication link parameters includes:
[0020] If the communication link impedance value is less than a first preset impedance threshold and the signal strength is greater than a first preset strength threshold, then the first conduction command is generated.
[0021] If the communication link impedance value is greater than the second preset impedance threshold and the signal strength is less than the second preset strength threshold, then the first disconnect command is generated.
[0022] Optionally, the step of statistically analyzing the received multiple first on / off commands and the generated first on / off commands, and generating a second on / off command based on the statistical results, includes:
[0023] The first percentage of the first disconnect command and the second percentage of the first connect command are statistically analyzed.
[0024] If the first percentage is greater than or equal to a preset percentage threshold, then the second disconnection command is generated;
[0025] If the second percentage is greater than or equal to the preset percentage threshold, then the second conduction command is generated.
[0026] Optionally, generating a third on / off command based on the current value of the photovoltaic module includes:
[0027] If the current value is equal to 0, then the third disconnect command is generated;
[0028] If the current value is not equal to 0, then the third conduction command is generated.
[0029] Optionally, determining the on / off state of the inverter DC switch based on the second on / off command and the third on / off command includes:
[0030] If the second on / off command is the second off command and the third on / off command is the third off command, then the on / off state of the inverter DC switch is the off state;
[0031] If the second on / off command is the second on command and the third on / off command is the third on command, then the on / off state of the inverter DC switch is the on state.
[0032] Optionally, controlling the voltage output of the connected photovoltaic module according to the on / off state of the inverter DC switch includes:
[0033] If the on / off state of the inverter DC switch is the off state, then control the stop output voltage of the photovoltaic module connected to it;
[0034] If the on / off state of the inverter DC switch is the on state, then the photovoltaic module connected to it is controlled to continue outputting voltage.
[0035] Secondly, embodiments of this application also provide a photovoltaic system, which includes: a plurality of photovoltaic strings;
[0036] Each of the photovoltaic strings includes multiple photovoltaic modules and multiple module-level photovoltaic devices;
[0037] Each of the component-level photovoltaic devices is connected to a photovoltaic module, and the component-level photovoltaic devices on each photovoltaic string are connected to each other via a PLC communication link.
[0038] Each of the aforementioned module-level photovoltaic devices is used to execute the automatic on / off control method for a photovoltaic system as described in any one of claims 1-8.
[0039] Optionally, the module-level photovoltaic device includes a current detection module, a carrier communication module, a control module, and a switching module;
[0040] The current detection module, the carrier communication module, and the switch module are all connected to an output terminal of the photovoltaic module, and the current detection module, the carrier communication module, and the switch module are all connected to the control module.
[0041] The current detection module is used to collect the current value of the photovoltaic module;
[0042] The carrier communication module is used to collect the communication link parameters of the photovoltaic string;
[0043] The control module is used to determine the on / off state of the inverter DC switch based on the communication link parameters and the current value, and to control the voltage output of the photovoltaic module connected to the switch module based on the on / off state of the inverter DC switch, so as to control the on / off state of the photovoltaic system.
[0044] This application embodiment collects the communication link parameters of the photovoltaic string and the current value of the photovoltaic module. Based on the communication link parameters and current value, the on / off state of the inverter's DC switch can be determined from different perspectives, thereby increasing the accuracy and reliability of determining the on / off state of the inverter's DC switch. This improves the accuracy and reliability of controlling the voltage output of the connected photovoltaic module based on the on / off state of the inverter's DC switch, thus enhancing the accuracy and reliability of controlling the on / off state of the photovoltaic system. Furthermore, compared to related technologies, the automatic on / off control of the photovoltaic system eliminates the need for a PLC signal transmitter, thereby reducing the complexity and cost of automatic on / off control of the photovoltaic system. Attached Figure Description
[0045] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0046] Figure 1 is a flowchart illustrating an automatic on / off control method for a photovoltaic system provided in an embodiment of this application;
[0047] Figure 2 is a schematic diagram of a step for determining the on / off state of an inverter DC switch according to an embodiment of this application;
[0048] Figure 3 is a schematic diagram of the structure of a module-level photovoltaic device provided in an embodiment of this application. Detailed Implementation
[0049] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.
[0050] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0051] This application provides an automatic on / off control method for a photovoltaic system. This method is applied to module-level photovoltaic equipment. Each module-level photovoltaic device is connected to a photovoltaic module. Module-level photovoltaic devices connected to photovoltaic modules in the same photovoltaic string are connected to each other via a PLC communication link.
[0052] Among them, the module-level photovoltaic equipment includes optimizers or circuit breakers, which can monitor the operating parameters of the photovoltaic modules connected to them, the operating parameters of the photovoltaic strings in which the photovoltaic modules connected to them are located, and exchange information with other module-level photovoltaic equipment in the same photovoltaic string, and adjust the operating status and operating parameters of the photovoltaic strings connected to them according to the above information.
[0053] Based on the structural characteristic that photovoltaic devices connected to photovoltaic modules in the same photovoltaic string can communicate through PLC communication links, this solution proposes an automatic on / off control method for photovoltaic systems to improve the accuracy and reliability of automatic on / off control and reduce the complexity and cost of automatic on / off control.
[0054] Figure 1 is a flowchart illustrating an automatic on / off control method for a photovoltaic system according to an embodiment of this application. This embodiment is applicable to situations requiring on / off control of a photovoltaic system. As shown in Figure 1, the method specifically includes the following steps:
[0055] S110: Collect the communication link parameters of the photovoltaic string and the current value of the photovoltaic module.
[0056] The communication link parameters include the communication link impedance and signal strength. Changes in the on / off state of the inverter's DC switch will cause changes in the communication link parameters of the connected photovoltaic strings and the current value of each photovoltaic module. Therefore, the module-level photovoltaic equipment connected to each photovoltaic module can confirm the on / off state of the inverter's DC switch by collecting the communication link parameters of the photovoltaic strings and the current value of the photovoltaic modules.
[0057] S120. Determine the on / off state of the inverter's DC switch based on the communication link parameters and current value.
[0058] The on / off state of the inverter DC switch includes an on state and an off state; when the inverter DC switch is closed, the on / off state of the inverter DC switch is the on state; when the inverter DC switch is open, the on / off state of the inverter DC switch is the off state.
[0059] Specifically, when the inverter's DC switch is closed, the internal capacitors of the inverter connect to the photovoltaic string, completing the photovoltaic string's circuit. This reduces the impedance of the PLC communication link, increases the signal strength, and allows the photovoltaic modules in the photovoltaic string to output current when there is no fault. Conversely, when the inverter's DC switch is open, the photovoltaic string is disconnected from the internal capacitors of the inverter, breaking the photovoltaic string's circuit. This causes a sharp increase in the impedance of the PLC communication link, weakens the signal strength, and prevents the photovoltaic modules from outputting current. Therefore, the module-level photovoltaic equipment connected to each photovoltaic module can determine the on / off state of the inverter's DC switch based on changes in communication link parameters and current values.
[0060] S130. Control the voltage output of the photovoltaic modules connected to the inverter based on the on / off state of the inverter's DC switch, so as to control the on / off state of the photovoltaic system.
[0061] The inverter's DC switch has two states: on and off. If the DC switch is on, the photovoltaic string's circuit is connected, and the connected photovoltaic modules need to be controlled to continue outputting voltage to keep the photovoltaic system running normally. If the DC switch is off, the photovoltaic string's circuit is disconnected, and the connected photovoltaic modules need to be controlled to stop outputting voltage to disconnect the photovoltaic system and stop its operation.
[0062] This application embodiment collects the communication link parameters of the photovoltaic string and the current value of the photovoltaic module. Based on the communication link parameters and current value, the on / off state of the inverter's DC switch can be determined from different perspectives, thereby increasing the accuracy and reliability of determining the on / off state of the inverter's DC switch. This improves the accuracy and reliability of controlling the voltage output of the connected photovoltaic module based on the on / off state of the inverter's DC switch, thus enhancing the accuracy and reliability of controlling the on / off state of the photovoltaic system. Furthermore, compared to related technologies, the automatic on / off control of the photovoltaic system eliminates the need for a PLC signal transmitter, thereby reducing the complexity and cost of automatic on / off control of the photovoltaic system.
[0063] Based on the above embodiments, optionally, Figure 2 is a schematic diagram illustrating a step for determining the on / off state of an inverter DC switch according to an embodiment of this application. As shown in Figure 2, the steps for determining the on / off state of the inverter DC switch are explained:
[0064] S210. Generate a first on / off command based on the communication link parameters, and broadcast the first on / off command through the PLC communication link.
[0065] The communication link parameters include the communication link impedance value and signal strength. The first on / off command is a signal indicating the on / off state of the inverter's DC switch, obtained by judging through the communication link parameters. The first on / off command includes a first off command and a first on command. The first off command indicates that the inverter's DC switch is in an off state, and the first on command indicates that the inverter's DC switch is in a on state. Furthermore, the first off command includes a timestamp, the address of the device sending the command, and signal parameters (parameters indicating that the inverter's DC switch is in an off state); the first on command includes a timestamp, the address of the device sending the command, and signal parameters (parameters indicating that the inverter's DC switch is in a on state).
[0066] Specifically, based on the characteristics that closing the inverter DC switch reduces the impedance of the PLC communication link and increases the signal strength, and opening the inverter DC switch causes a sharp increase in the impedance of the PLC communication link and attenuates the signal strength, the on / off state of the inverter DC switch can be determined by judging the range of the communication link impedance and signal strength. The specific process of generating the first on / off command based on the communication link parameters is as follows:
[0067] If the communication link impedance is less than the first preset impedance threshold and the signal strength is greater than the first preset strength threshold, a first conduction command is generated; if the communication link impedance is greater than the second preset impedance threshold and the signal strength is less than the second preset strength threshold, a first disconnection command is generated.
[0068] S220. Statistically analyze the received first on / off commands and the generated first on / off commands, and generate a second on / off command based on the statistical results.
[0069] Among them, the received first on / off commands and the generated first on / off commands are statistically analyzed. Each component-level photovoltaic device can be re-judged synchronously using a majority judgment mechanism to further avoid single-point misjudgment of each component-level photovoltaic device, thereby realizing collaborative verification of multiple devices and enhancing the accuracy of the judgment results.
[0070] In addition, the second on / off command includes a second off command and a second on command. The second off command indicates that the inverter DC switch is in the off state, and the second on command indicates that the inverter DC switch is in the on state.
[0071] The specific process for generating the second on / off command based on the statistical results is as follows: The first percentage of the first off command and the second percentage of the first on command are calculated. If the first percentage is greater than or equal to a preset percentage threshold, a second off command is generated; if the second percentage is greater than or equal to the preset percentage threshold, a second on command is generated.
[0072] For example, the total number of received and generated first on / off commands is 10, of which the number of first off commands is 7, so the first proportion is 7 / 10; the number of first on commands is 3, so the second proportion is 3 / 10; the preset proportion threshold is 6 / 10. Obviously, if the first proportion is greater than or equal to the preset proportion threshold, a second off command will be generated.
[0073] S230. Generate a third on / off command based on the current value of the photovoltaic module.
[0074] The third on / off command includes a third off command and a third on command. The third on / off command is a signal indicating the on / off state of the inverter's DC switch, obtained by judging the current value of the photovoltaic module. The third off command indicates that the inverter's DC switch is in the off state, and the third on command indicates that the inverter's DC switch is in the on state.
[0075] Specifically, based on the characteristic that closing the inverter's DC switch connects the photovoltaic string's circuit, causing the photovoltaic modules to output current when there is no fault, and opening the inverter's DC switch disconnects the photovoltaic string's circuit, preventing current output from the photovoltaic modules, the on / off state of the inverter's DC switch can be determined by observing the current value of the photovoltaic modules. The specific process of generating the three-way on / off command based on the photovoltaic module's current value is as follows:
[0076] If the current value is 0, a third disconnect command is generated. (A zero current value indicates that the photovoltaic string circuit is open and the inverter DC switch is disconnected.)
[0077] If the current value is not equal to 0, a third conduction command is generated. (A non-zero current value indicates that the photovoltaic string circuit is connected, and the inverter DC switch is closed.)
[0078] S240. Determine the on / off state of the inverter DC switch according to the second on / off command and the third on / off command.
[0079] The second and third on / off commands can be used to determine the on / off status of the inverter's DC switch from different perspectives, thereby increasing the accuracy and reliability of determining the on / off status of the inverter's DC switch, reducing the false judgment rate, and thus improving the accuracy and reliability of controlling the on / off state of the photovoltaic system.
[0080] Specifically, the process of determining the on / off state of the inverter's DC switch based on the second and third on / off commands is as follows:
[0081] If the second on / off command is the second off command and the third on / off command is the third off command, then the inverter DC switch is in the off state.
[0082] The fact that the second on / off command is the second off command and the third on / off command is the third off command indicates that the results of judging the on / off state of the inverter DC switch from different perspectives are consistent, and the judgment of the on / off state of the inverter DC switch is always the off state.
[0083] It should be noted that during the automatic disconnection control of the photovoltaic system, the inverter DC switch will only be determined to be in the disconnected state when both the second on / off command and the third on / off command are the same.
[0084] If the second on / off command is the second on command and the third on / off command is the third on command, then the on / off state of the inverter DC switch is the on state.
[0085] The second on / off command is the second on command and the third on / off command is the third on command, indicating that the results of judging the on / off state of the inverter DC switch from different perspectives are consistent, and the judgment of the on / off state of the inverter DC switch is always the on state.
[0086] It should be noted that during the automatic on / off control of the photovoltaic system, the inverter DC switch will only be determined to be in the on / off state when both the second on / off command and the third on / off command are the second on / off command.
[0087] Based on the above embodiments, optionally, the voltage output of the connected photovoltaic modules is controlled according to the on / off state of the inverter's DC switch:
[0088] Specifically, if the inverter's DC switch is in the open state, the connected photovoltaic modules will stop outputting voltage. If the inverter's DC switch is in the on state, the connected photovoltaic modules will continue to output voltage.
[0089] This application embodiment also provides a photovoltaic system, which includes: multiple photovoltaic strings;
[0090] Each photovoltaic string includes multiple photovoltaic modules and multiple module-level photovoltaic devices; each module-level photovoltaic device is connected to a photovoltaic module, and the module-level photovoltaic devices on each photovoltaic string are connected to each other through a PLC communication link; each module-level photovoltaic device is used to execute the automatic on / off control method of the photovoltaic system provided in any embodiment of this application, and therefore has the beneficial effects of the automatic on / off control method of the photovoltaic system, which will not be elaborated further.
[0091] Based on the above embodiments, optionally, Figure 3 is a structural schematic diagram of a module-level photovoltaic device provided in an embodiment of this application. As shown in Figure 3, the module-level photovoltaic device includes a current detection module 310, a carrier communication module 320, a control module 330, and a switch module 340;
[0092] The current detection module 310, the carrier communication module 320, and the switch module 340 are all connected to one output terminal of the photovoltaic module PV, and the current detection module 310, the carrier communication module 320, and the switch module 340 are all connected to the control module 330.
[0093] The current detection module 310 is used to collect the current value of the photovoltaic module PV;
[0094] The carrier communication module 320 is used to collect the communication link parameters of the photovoltaic string;
[0095] The control module 330 is used to determine the on / off state of the inverter DC switch based on the communication link parameters and current value, and to control the voltage output of the photovoltaic module PV connected to the switch module 340 based on the on / off state of the inverter DC switch, so as to control the on / off state of the photovoltaic system.
[0096] Based on the above embodiments, optionally, the control module includes:
[0097] The first control unit is used to generate a first on / off command based on the communication link parameters, and control the carrier communication module to broadcast the first on / off command through the PLC communication link;
[0098] The second control unit is used to statistically analyze the received and generated first on / off commands and generate second on / off commands based on the statistical results.
[0099] The third control unit is used to generate a third on / off command based on the current value of the photovoltaic module;
[0100] The fourth control unit is used to determine the on / off state of the inverter DC switch based on the second and third on / off commands.
[0101] Based on the above embodiments, optionally, the first control unit is specifically used for:
[0102] If the communication link impedance is less than the first preset impedance threshold and the signal strength is greater than the first preset strength threshold, a first conduction command is generated.
[0103] If the communication link impedance is greater than the second preset impedance threshold and the signal strength is less than the second preset strength threshold, a first disconnect command is generated.
[0104] Based on the above embodiments, optionally, the second control unit is specifically used to: count the first proportion of the first disconnect command and the second proportion of the first turn-on command;
[0105] If the first percentage is greater than or equal to the preset percentage threshold, a second disconnect command is generated;
[0106] If the second percentage is greater than or equal to the preset percentage threshold, a second conduction command is generated.
[0107] Based on the above embodiments, optionally, the third control unit is specifically used to: generate a third disconnect command if the current value is equal to 0;
[0108] If the current value is not equal to 0, a third conduction command is generated.
[0109] Based on the above embodiments, optionally, the fourth control unit is specifically used for:
[0110] If the second on / off command is the second off command and the third on / off command is the third off command, then the on / off state of the inverter DC switch is the off state.
[0111] If the second on / off command is the second on command and the third on / off command is the third on command, then the on / off state of the inverter DC switch is the on state.
[0112] Optionally, based on the above embodiments, the control module further includes: a fifth control unit;
[0113] The fifth control unit is specifically used for:
[0114] If the DC switch of the inverter is in the open state, then the output voltage of the connected photovoltaic module is stopped.
[0115] If the DC switch of the inverter is in the ON state, the connected photovoltaic modules will continue to output voltage.
[0116] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this application can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this application can be achieved, and this is not limited herein.
[0117] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.
Claims
1. An automatic on / off control method for a photovoltaic system, applied to module-level photovoltaic equipment, wherein each module-level photovoltaic equipment is connected to a photovoltaic module, and the module-level photovoltaic equipment connected to the photovoltaic modules in the same photovoltaic string are connected to each other via a PLC communication link; The automatic on / off control method for the photovoltaic system includes: Collect the communication link parameters of the photovoltaic string and the current value of the photovoltaic module; Based on the communication link parameters and the current value, determine the on / off state of the inverter's DC switch; The voltage output of the photovoltaic module connected to the inverter is controlled according to the on / off state of the inverter DC switch, thereby controlling the on / off state of the photovoltaic system.
2. The automatic on / off control method for a photovoltaic system according to claim 1, wherein, The step of determining the on / off state of the inverter's DC switch includes: A first on / off command is generated based on the communication link parameters, and the first on / off command is broadcast through the PLC communication link; The received multiple first on / off commands and the generated first on / off commands are statistically analyzed, and a second on / off command is generated based on the statistical results. A third on / off command is generated based on the current value of the photovoltaic module; The on / off state of the inverter DC switch is determined according to the second on / off command and the third on / off command.
3. The automatic on / off control method for a photovoltaic system according to claim 2, wherein, The communication link parameters include the communication link impedance value and signal strength; The first on / off command includes a first off command and a first on command; The second on / off command includes a second off command and a second on command; The third on / off command includes a third disconnect command and a third on command.
4. The automatic on / off control method for a photovoltaic system according to claim 3, wherein, The step of generating a first on / off command based on the communication link parameters includes: If the communication link impedance value is less than a first preset impedance threshold and the signal strength is greater than a first preset strength threshold, then the first conduction command is generated. If the communication link impedance value is greater than the second preset impedance threshold and the signal strength is less than the second preset strength threshold, then the first disconnect command is generated.
5. The automatic on / off control method for a photovoltaic system according to claim 3, wherein, The step of statistically analyzing the received multiple first on / off commands and the generated first on / off commands, and generating a second on / off command based on the statistical results, includes: The first percentage of the first disconnect command and the second percentage of the first connect command are statistically analyzed. If the first percentage is greater than or equal to a preset percentage threshold, then the second disconnection command is generated; If the second percentage is greater than or equal to the preset percentage threshold, then the second conduction command is generated.
6. The automatic on / off control method for a photovoltaic system according to claim 3, wherein, The step of generating a third on / off command based on the current value of the photovoltaic module includes: If the current value is equal to 0, then the third disconnect command is generated; If the current value is not equal to 0, then the third conduction command is generated.
7. The automatic on / off control method for a photovoltaic system according to claim 3, wherein, Determining the on / off state of the inverter DC switch based on the second on / off command and the third on / off command includes: If the second on / off command is the second off command and the third on / off command is the third off command, then the on / off state of the inverter DC switch is the off state; If the second on / off command is the second on command and the third on / off command is the third on command, then the on / off state of the inverter DC switch is the on state.
8. The automatic on / off control method for a photovoltaic system according to claim 7, wherein, The step of controlling the voltage output of the connected photovoltaic module according to the on / off state of the inverter DC switch includes: If the on / off state of the inverter DC switch is the off state, then control the stop output voltage of the photovoltaic module connected to it; If the on / off state of the inverter DC switch is the on state, then the photovoltaic module connected to it is controlled to continue outputting voltage.
9. A photovoltaic system, comprising: Multiple photovoltaic strings; Each of the photovoltaic strings includes multiple photovoltaic modules and multiple module-level photovoltaic devices; Each of the component-level photovoltaic devices is connected to a photovoltaic module, and the component-level photovoltaic devices on each photovoltaic string are connected to each other via a PLC communication link. Each of the aforementioned module-level photovoltaic devices is used to execute the automatic on / off control method for a photovoltaic system as described in any one of claims 1-8.
10. The photovoltaic system according to claim 9, wherein, The component-level photovoltaic equipment includes a current detection module, a carrier communication module, a control module, and a switching module; The current detection module, the carrier communication module, and the switch module are all connected to an output terminal of the photovoltaic module, and the current detection module, the carrier communication module, and the switch module are all connected to the control module. The current detection module is used to collect the current value of the photovoltaic module; The carrier communication module is used to collect the communication link parameters of the photovoltaic string; The control module is used to determine the on / off state of the inverter DC switch based on the communication link parameters and the current value, and to control the voltage output of the photovoltaic module connected to the switch module based on the on / off state of the inverter DC switch, so as to control the on / off state of the photovoltaic system.