Photovoltaic system and control method
By introducing combiner box switches, excitation fuses, and DC switches into the photovoltaic system, and combining current and voltage thresholds to determine short-circuit faults, flexible control at different locations is achieved, solving the problem of DC-side short-circuit fault expansion in the photovoltaic system and improving the system's safety and reliability.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SUNGROW POWER SUPPLY CO LTD
- Filing Date
- 2025-06-10
- Publication Date
- 2026-07-30
AI Technical Summary
When a short circuit fault occurs on the DC side of a centralized photovoltaic system, it may damage the combiner box, inverter, or photovoltaic string. Existing technology makes it difficult to disconnect the faulty branch in time, thus expanding the scope of the fault.
By introducing combiner box switches, excitation fuses, and DC switches into combiner boxes and inverters, the location of short-circuit faults can be determined by current and voltage thresholds, and the corresponding switches and fuses can be controlled to open, thus achieving flexible protection measures.
It effectively narrows the scope of the fault, prevents damage to photovoltaic panels, combiner boxes or inverters, ensures the continued operation of normal circuits, and improves the safety and reliability of the system.
Smart Images
Figure CN2025100069_30072026_PF_FP_ABST
Abstract
Description
A photovoltaic system and its control method
[0001] This disclosure claims priority to Chinese patent applications filed on January 23, 2025, with application number 202510112938.0 and entitled "A Photovoltaic System and Control Method", and on May 26, 2025, with application number 202510685835.3 and entitled "A Photovoltaic System and Control Method", the entire contents of which are incorporated herein by reference. Technical Field
[0002] This disclosure relates to a photovoltaic system and a control method thereof. Background Technology
[0003] Centralized photovoltaic (PV) systems typically consist of a combiner box and an inverter. The combiner box's input is connected to multiple PV panels, and its output is connected to the DC side of the inverter. The combiner box's function is to combine current from multiple PV panels, while the inverter converts DC power to AC power. Due to the 1V / 1A current characteristic of PV panels, if a short circuit occurs on the DC side of the PV system and the faulty branch is not disconnected promptly, it may cause damage to one or more components of the combiner box, inverter, or PV string. Summary of the Invention
[0004] In view of the above, this disclosure provides a photovoltaic system and control method, as follows.
[0005] This disclosure provides a photovoltaic system, including: a combiner box and an inverter; the combiner box includes a combiner box switch, and the inverter includes an excitation fuse and a power conversion circuit.
[0006] The input terminal of the combiner box is used to connect to the corresponding photovoltaic panel, and the output terminal of the combiner box is connected to the DC side of the inverter. The combiner box switch is connected in series between the input terminal and the output terminal of the combiner box. The first end of the excitation fuse is connected to the DC side of the inverter, and the second end of the excitation fuse is connected to the power conversion circuit.
[0007] In the event of a short circuit fault between the combiner box switch and the photovoltaic panel, the combiner box switch opens, and the current flowing through the excitation fuse exceeds the first current threshold, causing the excitation fuse to open; in the event of a short circuit fault between the combiner box switch and the DC side of the inverter, the combiner box switch and the corresponding excitation fuse open; in the event of a short circuit fault inside the inverter, the combiner box switch opens.
[0008] One possible implementation is that the combiner box includes a first controller;
[0009] The first controller is configured to determine that a short circuit fault has occurred between the combiner box switch and the photovoltaic panel when the input voltage of the combiner box is less than a first voltage threshold and / or the input current of the combiner box flows from the combiner box to the photovoltaic panel and is greater than a second current threshold, and control the corresponding combiner box switch to open; the first current threshold is greater than the second current threshold.
[0010] One possible implementation is that the inverter includes a second controller;
[0011] The second controller is used to determine that a short circuit fault has occurred between the combiner box switch connected to the excitation fuse and the photovoltaic panel when the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than the second current threshold, and the input voltage of the inverter is less than the second voltage threshold; when the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than the first current threshold, the controller controls the excitation fuse to open, and the first current threshold is greater than the second current threshold.
[0012] One possible implementation is that the combiner box includes a first controller; the first controller is used to determine that a short circuit fault has occurred between the combiner box switch and the DC side of the inverter when the input voltage of the combiner box is less than a third voltage threshold and the input current of the combiner box flows from the photovoltaic panel to the combiner box and is greater than a third current threshold, and then controls the corresponding combiner box switch to open.
[0013] In one possible implementation, the inverter includes a second controller; the second controller is configured to determine that a short circuit fault has occurred between the combiner box switch and the DC side of the inverter when the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than a third current threshold, and the input voltage of the inverter is less than a fourth voltage threshold, and then control the excitation fuse to open.
[0014] One possible implementation is that the photovoltaic system includes at least two combiner boxes; the input of each combiner box is connected to the corresponding photovoltaic panel, and the output of each combiner box is connected in parallel to the DC side of the inverter;
[0015] The inverter has a corresponding excitation fuse for each combiner box.
[0016] One possible implementation is that each combiner box includes a first controller; the first controllers of all combiner boxes communicate with each other;
[0017] For any first controller, if the input voltage of all combiner boxes is less than the fifth voltage threshold, and the input current of all combiner boxes flows from the corresponding photovoltaic panel to the combiner box and is greater than the fourth current threshold, it is determined that there is a fault inside the inverter, and all combiner box switches are controlled to be disconnected.
[0018] In one possible implementation, the inverter includes a second controller and a DC switch; the second end of an excitation fuse is connected to the first end of the DC switch, and the second end of the DC switch is connected to a power conversion circuit;
[0019] The second controller is used to determine that a short circuit fault has occurred inside the inverter when the current direction of the excitation fuse corresponding to each combiner box is from the corresponding combiner box to the excitation fuse and is greater than the fourth current threshold, and the input voltage of the inverter is less than the sixth voltage threshold, and controls the DC switch of the inverter to open.
[0020] This disclosure also provides a control method for a photovoltaic system.
[0021] The method includes:
[0022] In the event of a short circuit fault between the combiner box switch and the photovoltaic panel, the combiner box switch in the control combiner box is opened, and the current flowing through the excitation fuse exceeds the first current threshold, thus opening the excitation fuse. The combiner box switch is connected in series between the input terminal and the output terminal of the combiner box; the excitation fuse is connected between the DC side of the inverter and the power conversion circuit.
[0023] In the event of a short circuit fault between the combiner box switch and the DC side of the inverter, the combiner box switch and the corresponding excitation fuse will be disconnected.
[0024] In the event of a short circuit fault inside the inverter, the control combiner box switch will be disconnected.
[0025] One possible implementation, the method provided in this disclosure, further includes: if the input voltage of the combiner box is less than a first voltage threshold, and / or the input current of the combiner box flows from the combiner box to the photovoltaic panel and is greater than a second current threshold, then it is determined that a short circuit fault has occurred between the combiner box switch and the photovoltaic panel.
[0026] One possible implementation, the method provided in this disclosure, further includes: when the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than a second current threshold, and the input voltage of the inverter is less than a second voltage threshold, then it is determined that a short circuit fault has occurred between the combiner box switch connected to the excitation fuse and the photovoltaic panel; when the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than a first current threshold, the excitation fuse is controlled to open.
[0027] One possible implementation, the method provided in this disclosure, further includes: if the input voltage of the combiner box is less than a third voltage threshold, and the input current of the combiner box flows from the photovoltaic panel to the combiner box and is greater than a third current threshold, then it is determined that a short circuit fault has occurred between the combiner box switch and the DC side of the inverter.
[0028] One possible implementation, the method provided in this disclosure, further includes: if the current flowing through the excitation fuse is in the direction of flowing from the excitation fuse to the combiner box and is greater than a third current threshold, and the input voltage of the inverter is less than a fourth voltage threshold, then it is determined that a short circuit fault has occurred between the combiner box switch and the DC side of the inverter.
[0029] One possible implementation, the method provided in this disclosure embodiment, further includes: when the input voltage of all combiner boxes is less than a fifth voltage threshold, and the input current direction of all combiner boxes is from the corresponding photovoltaic panel to the combiner box and is greater than a fourth current threshold, it is determined that a fault has occurred inside the inverter, and the corresponding combiner box switch is controlled to open.
[0030] One possible implementation, the method provided in this disclosure embodiment, further includes: the current direction of the excitation fuse corresponding to each combiner box is from the corresponding combiner box to the excitation fuse and is greater than the fourth current threshold, the input voltage of the inverter is less than the sixth voltage threshold, and a short circuit fault is determined to have occurred inside the inverter.
[0031] This disclosure also provides a control device, including a processor and a memory. The memory is used to store programs, instructions, or code, and the processor is used to execute the programs, instructions, or code in the memory to perform the control method described above.
[0032] This disclosure also provides a computer-readable storage medium storing a computer program, which is loaded by a processor to execute the control method described above.
[0033] The photovoltaic system provided in this disclosure may experience a short circuit on the DC side during operation. This short circuit may occur between the combiner box and the photovoltaic panel, between the combiner box and the inverter input terminal, or within the inverter itself. The technical solution provided in this disclosure allows for different protection measures depending on the location of the short circuit. Specifically, it allows for different controls based on the specific fault location, effectively disconnecting the faulty circuit to prevent the fault from spreading while ensuring the normal circuit continues to operate.
[0034] Brief description of the attached figures
[0035] Figure 1 is a schematic diagram of a photovoltaic system provided in an embodiment of this disclosure;
[0036] Figure 2 is a schematic diagram of another photovoltaic system provided in an embodiment of this disclosure;
[0037] Figure 3 is a schematic diagram of another photovoltaic system provided in an embodiment of this disclosure;
[0038] Figure 4 is a schematic diagram of the current flow of the photovoltaic system when a short circuit fault occurs between the combiner box switch and the photovoltaic panel according to an embodiment of this disclosure;
[0039] Figure 5 is a schematic diagram of a short circuit between the combiner box and the inverter provided in an embodiment of this disclosure;
[0040] Figure 6 is a schematic diagram of an internal short circuit in an inverter provided in an embodiment of this disclosure;
[0041] Figure 7 is a flowchart of a control method for a photovoltaic system provided in an embodiment of this disclosure;
[0042] Figure 8 is a schematic diagram of a control device provided in an embodiment of this disclosure. Detailed Implementation
[0043] To enable those skilled in the art to better understand and implement the photovoltaic system provided in the embodiments of this disclosure, the architecture of the photovoltaic system will be described below in conjunction with the accompanying drawings.
[0044] Referring to Figure 1, this figure is a schematic diagram of a photovoltaic system provided in an embodiment of this disclosure.
[0045] The photovoltaic system provided in this embodiment includes at least one combiner box, as shown in Figure 1 from combiner box 1 to combiner box N, where N is an integer greater than or equal to 1. Generally, a photovoltaic system includes multiple combiner boxes. The function of the combiner box is to combine the energy from multiple photovoltaic panels and provide it to the input terminal (i.e., the DC side) of the inverter 100. The input terminal of each combiner box is connected to a corresponding photovoltaic panel, which may include multiple photovoltaic cells, without specific limitations. The output terminal of each combiner box is connected to the DC side of the inverter 100, which is equivalent to the output terminals of all combiner boxes being connected in parallel.
[0046] When the photovoltaic system is working, a short circuit fault may occur on the DC side. The short circuit fault may occur between the combiner box and the photovoltaic panel, between the combiner box and the input terminal of the inverter 100, or inside the inverter 100.
[0047] The photovoltaic system provided in this disclosure can take different protection measures according to the short circuit fault occurring in different parts. That is, different controls can be performed according to the specific fault location. It can disconnect the faulty circuit to prevent the fault range from expanding, while ensuring that the normal circuit continues to operate.
[0048] To make the above-mentioned objectives, features and advantages of this disclosure more apparent and understandable, the embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings and specific implementation methods.
[0049] Referring to Figure 2, this figure is a schematic diagram of another photovoltaic system provided in an embodiment of this disclosure.
[0050] The photovoltaic system provided in this embodiment includes a combiner box and an inverter 100. The input terminal of the combiner box is used to connect to the corresponding photovoltaic panel, and the output terminal of the combiner box is connected to the DC side of the inverter 100.
[0051] For ease of explanation, this embodiment of the present disclosure uses a photovoltaic system comprising at least two combiner boxes as an example: a first combiner box 21 and a second combiner box 22. A combiner box switch is connected in series between the input and output terminals of the combiner box; that is, the first combiner box 21 includes a first combiner box switch 10, and the second combiner box 22 includes a second combiner box switch 11. The inverter 100 includes an excitation fuse and a DC switch 101. The inverter 100 internally provides a corresponding excitation fuse for each combiner box, meaning there is a one-to-one correspondence between the excitation fuse and the combiner box. It should be understood that since the output terminals of each combiner box include a positive output terminal and a negative output terminal, the excitation fuses connected to the output terminals of each combiner box can be a group, i.e., one excitation fuse for each positive output terminal and one for each negative output terminal. Alternatively, each combiner box may have only one excitation fuse connected to its output terminal, for example, only one excitation fuse connected to the positive output terminal or only one excitation fuse connected to the negative output terminal. The following description uses the example of connecting excitation fuses to both the positive and negative output terminals of each combiner box. For the sake of brevity, the description will be based on the first combiner box 21 corresponding to the first set of excitation fuses F1 and the second combiner box 22 corresponding to the second set of excitation fuses F2.
[0052] It should be understood that the current sensor and the switch inside the combiner box are both connected to the first controller of the combiner box (not shown in the figure).
[0053] The first end of the excitation fuse is connected to the DC side of the inverter 100, and the second end of the excitation fuse is connected to the first end of the DC switch 101. The second end of the DC switch 101 is connected to the power conversion circuit in the inverter 100, which includes a DC / AC circuit 102. As shown in Figure 2, the first end of the first set of excitation fuses F1 is connected to the second end of the first combiner box switch 10, which is connected to the first photovoltaic panel. The second end of the first set of excitation fuses F1 is connected to the first end of the DC / AC circuit 102. Similarly, the first end of the second set of excitation fuses F2 is connected to the second end of the second combiner box switch 11, which is connected to the second photovoltaic panel. The second end of the second set of excitation fuses F2 is connected to the first end of the DC / AC circuit 102.
[0054] It should be understood that Figure 2 is only an example of a photovoltaic system including two combiner boxes. In actual operation, the photovoltaic system can include a larger number of combiner boxes, i.e., N, where N is an integer greater than or equal to 2, as shown in Figure 3. Each combiner box is equipped with a combiner box switch, namely the first combiner box switch 10 to the Nth combiner box switch N0. The first excitation fuse corresponding to the first combiner box 21 is F1, and the Nth excitation fuse corresponding to the Nth combiner box 2N is FN. The current sensor CT1 is used to detect the input current of the first combiner box 21, and the current sensor CTN is used to detect the input current of the Nth combiner box 2N.
[0055] The specific working principle will be further explained below with reference to Figure 2. Current sensor CT11 is used to detect the current flowing through the first set of excitation fuses F1, and current sensor CT12 is used to detect the current flowing through the second set of excitation fuses F2.
[0056] In the event of a short circuit between the combiner box switch and the photovoltaic panel, the combiner box switch will open. For example, if a short circuit occurs between the first combiner box switch 10 and the first photovoltaic panel, simply opening the first combiner box switch 10 is sufficient. If the connection between the second combiner box switch 11 and the second photovoltaic panel is normal, the second combiner box switch 11 will remain closed, without affecting the power generation of the second photovoltaic panel. If a short circuit occurs between the first combiner box switch 10 and the first photovoltaic panel, and the current flowing through the first set of excitation fuses F1 exceeds the first current threshold, then the first set of excitation fuses F1 also needs to open.
[0057] In the event of a short circuit fault between the combiner box switch and the DC side of the inverter 100, the combiner box switch and the corresponding excitation fuse will disconnect. For example, if a short circuit fault occurs between the first combiner box switch 10 and the DC side of the inverter 100, then the first combiner box switch 10 and the corresponding first set of excitation fuses F1 must both disconnect.
[0058] In the event of a short-circuit fault inside inverter 100, the combiner box switch will open. The "inside" of the inverter refers to the inverter 100 as a whole; everything within the dashed box 100 is considered part of the inverter's internal structure. Specifically, a short-circuit fault inside inverter 100 includes a short circuit between DC switch 101 and the AC output terminal of inverter 100, i.e., a short circuit between DC switch 101 and the AC output terminal of DC / AC 102. When the photovoltaic system includes multiple combiner boxes, the combiner box switches in all combiner boxes need to be disconnected; both the first combiner box switch 10 and the second combiner box switch 11 in Figure 2 need to be disconnected.
[0059] The embodiments disclosed herein do not specifically limit the method of determining short circuit faults. For example, it can be determined by current or voltage. To improve accuracy, it can also be determined by a combination of current and voltage.
[0060] The photovoltaic system provided in this disclosure includes a combiner box and an inverter. The combiner box contains a combiner box switch, and the inverter contains an excitation fuse and a DC switch. Since the combiner box switch, excitation fuse, and DC switch are all controllable devices, different controllable devices can be flexibly controlled to disconnect when a short-circuit fault occurs at different locations. This minimizes the fault range and allows for timely protection, preventing damage to the photovoltaic panels, combiner box, or inverter caused by the short-circuit fault.
[0061] The following section, with reference to the accompanying diagrams, details the protective measures in case of short-circuit faults at different locations.
[0062] First, let's describe the situation where a short circuit occurs in the front stage of the combiner box.
[0063] Referring to Figure 4, this figure is a schematic diagram of the current flow of the photovoltaic system when a short circuit fault occurs between the combiner box switch and the photovoltaic panel according to an embodiment of this disclosure.
[0064] The photovoltaic system provided in this disclosure embodiment, for example, has a combiner box and an inverter 100 each having a controller (not shown), and the combiner boxes can communicate with each other. For ease of understanding, this disclosure embodiment continues to take the photovoltaic system including at least the following two combiner boxes as an example: a first combiner box 21 and a second combiner box 22.
[0065] The combiner box includes a first controller (not shown in the figure). It should be understood that each combiner box includes one first controller, and the term "first controller" is used generically. The inverter 100 includes a second controller (not shown in the figure). It should be understood that the current sensor and combiner box switch inside the combiner box are connected to the first controller of the combiner box.
[0066] For any one of the combiner boxes, the first controller determines that a short circuit fault has occurred between the combiner box switch and the photovoltaic panel when the input voltage of the combiner box is less than a first voltage threshold and / or the input current of the combiner box flows from the combiner box to the photovoltaic panel and is greater than a second current threshold, and controls the corresponding combiner box switch to open. Here, forward current is defined as flowing from the photovoltaic panel to the corresponding combiner box, and reverse current is defined as flowing from the combiner box to the corresponding photovoltaic panel; the first current threshold is greater than the second current threshold. It should be understood that, to improve the accuracy of short circuit fault detection, a short circuit fault between the combiner box switch and the photovoltaic panel can be determined when the input voltage of the combiner box is less than the first voltage threshold and the input current of the combiner box flows from the combiner box to the photovoltaic panel and is greater than the second current threshold.
[0067] For example, regarding the first combiner box 21, if the input current of the first combiner box 21 detected by the first current sensor CT1 is reversed and greater than the second current threshold, a short circuit fault is determined to have occurred between the first combiner box switch 10 and the first photovoltaic panel. To avoid erroneous operation, if the short circuit fault still exists after a preset delay time, the first combiner box switch 10 needs to be disconnected. Since the second combiner boxes connected to the second photovoltaic panel are all normal, they can operate normally and continue photovoltaic power generation, and the inverter 100 operates normally.
[0068] The photovoltaic system provided in this disclosure includes an inverter 100 that includes a second controller (not shown).
[0069] The second controller is used to determine that a short circuit fault has occurred between the combiner box switch connected to the excitation fuse and the photovoltaic panel when the direction of the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than the second current threshold, and the input voltage of the inverter 100 is less than the second voltage threshold; when the direction of the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than the first current threshold, the controller controls the excitation fuse to open.
[0070] It should be understood that when a short-circuit fault occurs in the front end of the combiner box, for the safety of the inverter 100, the second controller of the inverter 100 needs to determine whether the current flowing through the excitation fuse exceeds the first current threshold. If it does, the excitation fuse needs to be disconnected. If a short-circuit fault occurs in the front end of the first combiner box 21, the second controller will control the first set of excitation fuses F1 to disconnect, thereby protecting the safety of the DC switch 101 and DC / AC 102. This does not affect the normal operation of the branch where the second combiner box is located. That is, the second combiner box switch 20 is normally closed, the second set of excitation fuses F2 is normally conducting, the DC switch 101 is working normally, and the DC / AC 102 can work normally for photovoltaic power generation.
[0071] In order to minimize the need to replace the excitation fuse in the inverter 100 and reduce costs, when a short circuit fault occurs in the front end of the combiner box, if the short circuit current is small, for example, if the current flowing through the excitation fuse is less than the first current threshold, then the excitation fuse can be disconnected and only the combiner box switch can be turned off.
[0072] The following description, with reference to the attached diagram, illustrates a short-circuit fault between the combiner box output and the inverter input.
[0073] Referring to Figure 5, this figure is a schematic diagram of a short circuit occurring between the combiner box and the inverter provided in an embodiment of this disclosure.
[0074] The photovoltaic system provided in this embodiment includes a first controller configured to determine a short-circuit fault between the combiner box switch and the DC side of the inverter 100 when the input voltage of the combiner box is less than a third voltage threshold and the input current flowing from the photovoltaic panel to the combiner box is greater than a third current threshold, and then control the corresponding combiner box switch to disconnect. The DC side of the inverter 100 refers to the input terminal of the inverter 100.
[0075] It should be understood that the current sensor and the switch inside the combiner box are both connected to the first controller of the combiner box.
[0076] For example, if the input current detected by the first current sensor CT1 of the first combiner box 21 is positive but greater than the third current threshold, then a short circuit fault is determined to have occurred between the combiner box switch and the DC side of the inverter 100. This disclosure does not specifically limit the relationship between the second and third current thresholds. To protect the first combiner box 21 and the first photovoltaic panel, and to avoid misoperation, a preset time can be set. If the short circuit fault persists after the preset time, the first combiner box switch 10 needs to be disconnected. That is, if a short circuit fault occurs in the downstream stage of the combiner box, the combiner box switch inside the combiner box also needs to be disconnected.
[0077] The photovoltaic system provided in this embodiment of the present disclosure includes a second controller, which determines that a short circuit fault has occurred between the combiner box switch and the DC side of the inverter 100 when the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than a third current threshold, and the input voltage of the inverter 100 is less than a fourth voltage threshold, and controls the excitation fuse to open.
[0078] Since the excitation fuses are located inside the inverter 100, the second controller of the inverter 100 is needed to determine whether a short circuit fault has occurred between the DC side of the inverter 100 and the combiner box. Taking a short circuit fault between the first combiner box 21 and the inverter 100 as an example, the direction of the current flowing through the first set of excitation fuses F1 is from the first set of excitation fuses F1 to the first combiner box 21. When the current exceeds the third current threshold, and the input voltage of the inverter 100 is less than the fourth voltage threshold, it is determined that a short circuit fault has occurred between the combiner box and the inverter 100. The inverter 100 needs to disconnect the faulty branch, that is, disconnect the first set of excitation fuses F1. At this time, since the branch where the second combiner box 22 is located is normal, the DC switch 101 remains closed and can operate normally without affecting the power generation of the normal branch, thus minimizing the scope of the fault. Since DC switch 101 serves as a combiner for multiple combiner boxes, it can continue to operate as long as a normal combiner box branch exists. The faulty combiner box branch can be disconnected using the excitation fuse.
[0079] The following describes the protection measures for short-circuit faults inside the inverter 100.
[0080] Referring to Figure 6, this figure is a schematic diagram of a short circuit occurring inside the inverter provided in an embodiment of this disclosure.
[0081] The photovoltaic system provided in this disclosure includes a first controller (not shown) in each combiner box; the first controllers of all combiner boxes communicate with each other.
[0082] For any first controller, if the input voltage of all combiner boxes is less than the fifth voltage threshold, and the input current of all combiner boxes flows from the corresponding photovoltaic panel to the combiner box and is greater than the fourth current threshold, it is determined that there is a fault inside the inverter 100, and all combiner box switches are controlled to be disconnected.
[0083] Continuing with the example of two combiner boxes, internal faults in inverter 100 include short-circuit faults between the excitation fuse and DC / AC 102. When a short-circuit fault occurs inside inverter 100, since all combiner boxes are connected in parallel to the input terminal of inverter 100, the input voltages of both the first combiner box 21 and the second combiner box 22 will drop, and the currents in both combiner boxes 21 and 22 will be positive, i.e., flowing from the photovoltaic panel to the combiner box. If the current is large, for example, greater than the fourth current threshold, then a short-circuit fault is confirmed to have occurred inside inverter 100. To avoid erroneous operation, if the short-circuit fault persists after a preset time, the first controller of the first combiner box 21 controls the first combiner box switch 10 to open. The first controller of the second combiner box 22 controls the second combiner box switch 20 to open.
[0084] The photovoltaic system provided in this disclosure includes an inverter 100 that includes a second controller (not shown).
[0085] The second controller is used to determine that a short circuit fault has occurred inside the inverter 100 when the current direction of the excitation fuse corresponding to each combiner box is from the corresponding combiner box to the excitation fuse and is greater than the fourth current threshold, and the input voltage of the inverter 100 is less than the sixth voltage threshold. The controller controls the DC switch 101 of the inverter 100 to open. When the DC switch 101 is opened, the connection between the DC / AC 102 and all the front-end circuits is disconnected, thereby protecting the devices in the DC / AC 102.
[0086] As shown in Figure 6, a short circuit fault occurs between DC switch 101 and DC / AC 102. It should be understood that a short circuit fault could also occur between the excitation fuse and DC switch 101.
[0087] Based on the photovoltaic system provided in the above embodiments, this disclosure also provides a control method for the photovoltaic system, which will be described in detail below with reference to the accompanying drawings.
[0088] Referring to Figure 7, this figure is a flowchart of a control method for a photovoltaic system provided in an embodiment of this disclosure.
[0089] The control method for a photovoltaic system provided in this disclosure includes:
[0090] S701: In the event of a short circuit fault between the combiner box switch and the photovoltaic panel, the combiner box switch in the control system opens, and the current flowing through the excitation fuse exceeds the first current threshold, causing the excitation fuse to open. The combiner box switch is connected in series between the input and output terminals of the combiner box; the excitation fuse is connected between the DC side of the inverter and the power conversion circuit.
[0091] S702: In the event of a short circuit fault between the combiner box switch and the DC side of the inverter, the combiner box switch and the corresponding excitation fuse are disconnected.
[0092] S703: In the event of a short circuit fault inside the inverter, the control combiner box switch is disconnected.
[0093] The embodiments disclosed herein do not specifically limit the method of determining short circuit faults. For example, it can be determined by current or voltage. To improve accuracy, it can also be determined by a combination of current and voltage.
[0094] The photovoltaic system provided in this disclosure includes a combiner box and an inverter. The combiner box contains a combiner box switch, and the inverter contains an excitation fuse and a DC switch. Since the combiner box switch, excitation fuse, and DC switch are all controllable devices, different controllable devices can be flexibly controlled to disconnect when a short-circuit fault occurs at different locations. This minimizes the fault range and allows for timely protection, preventing damage to the combiner box or inverter caused by the short-circuit fault.
[0095] One possible implementation further includes: if the input voltage of the combiner box is less than a first voltage threshold, and / or the input current of the combiner box flows from the combiner box to the photovoltaic panel and is greater than a second current threshold, then a short circuit fault is determined to have occurred between the combiner box switch and the photovoltaic panel; the first current threshold is greater than the second current threshold.
[0096] One possible implementation further includes: if the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than a second current threshold, and the input voltage of the inverter is less than a second voltage threshold, then a short circuit fault is determined between the combiner box switch connected to the excitation fuse and the photovoltaic panel; when the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than a first current threshold, the excitation fuse is controlled to open; the first current threshold is greater than the second current threshold.
[0097] One possible implementation also includes: if the input voltage of the combiner box is less than a third voltage threshold and the input current of the combiner box flows from the photovoltaic panel to the combiner box and is greater than a third current threshold, then a short circuit fault is determined to have occurred between the combiner box switch and the DC side of the inverter.
[0098] One possible implementation also includes: if the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than the third current threshold, and the input voltage of the inverter is less than the fourth voltage threshold, then a short circuit fault is determined to have occurred between the combiner box switch and the DC side of the inverter.
[0099] One possible implementation also includes: if the input voltage of all combiner boxes is less than the fifth voltage threshold, and the input current of all combiner boxes flows from the corresponding photovoltaic panel to the combiner box and is greater than the fourth current threshold, then a fault is determined to have occurred inside the inverter, and the corresponding combiner box switch is controlled to disconnect.
[0100] One possible implementation also includes: the current direction of the excitation fuse corresponding to each combiner box is from the corresponding combiner box to the excitation fuse and is greater than the fourth current threshold, and the input voltage of the inverter is less than the sixth voltage threshold, to determine that a short circuit fault has occurred inside the inverter.
[0101] In one possible implementation, see Figure 8, which is a schematic diagram of a control device provided in an embodiment of this disclosure.
[0102] The control device may include a memory 1011 and a processor 1012. The processor 1012 can be connected to the combiner box and inverter in the photovoltaic system and can control the operation of the excitation fuse in the inverter. As shown in Figure 8, the memory may be random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (EEPROM), registers, hard disk, removable disk, etc.
[0103] The memory 1011 can store computer instructions. When the computer instructions stored in the memory 1011 are executed by the processor 1012, the processor 1012 can be used to execute the control method of the photovoltaic system. The memory 1011 can also store data, such as information like the first current threshold involved in the above embodiments.
[0104] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this disclosure is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape) or a semiconductor medium (e.g., solid-state disk (SSD)).
[0105] This disclosure also provides a readable storage medium for storing the methods provided in the above embodiments. Examples include random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (EPROM), registers, hard disks, removable disks, or any other form of storage medium in the art.
[0106] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the methods disclosed in the embodiments, since they correspond to the product embodiments disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the description of the product embodiments.
[0107] The above description of the disclosed embodiments enables those skilled in the art to make or use this disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A photovoltaic system, comprising: A combiner box and an inverter, wherein the combiner box includes a combiner box switch and the inverter includes an excitation fuse and a power conversion circuit; The input terminal of the combiner box is used to connect to the corresponding photovoltaic panel, the output terminal of the combiner box is connected to the DC side of the inverter, and the combiner box switch is connected in series between the input terminal and the output terminal of the combiner box; the first end of the excitation fuse is connected to the DC side of the inverter, and the second end of the excitation fuse is connected to the power conversion circuit. In the event of a short circuit fault between the combiner box switch and the photovoltaic panel, the combiner box switch is opened, and the current flowing through the excitation fuse exceeds a first current threshold, causing the excitation fuse to open; in the event of a short circuit fault between the combiner box switch and the DC side of the inverter, the combiner box switch and the corresponding excitation fuse are opened; in the event of a short circuit fault inside the inverter, the combiner box switch is opened.
2. The photovoltaic system according to claim 1, wherein, The junction box includes a first controller; The first controller is configured to determine that a short circuit fault has occurred between the combiner box switch and the photovoltaic panel if the input voltage of the combiner box is less than a first voltage threshold and / or the input current of the combiner box flows from the combiner box to the photovoltaic panel and is greater than a second current threshold, and control the corresponding combiner box switch to open. The first current threshold is greater than the second current threshold.
3. The photovoltaic system according to claim 1 or 2, wherein, The inverter includes a second controller; The second controller is configured to determine that a short circuit fault has occurred between the combiner box switch connected to the excitation fuse and the photovoltaic panel when the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than a second current threshold, and the input voltage of the inverter is less than a second voltage threshold; and when the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than a first current threshold, the controller controls the excitation fuse to open; the first current threshold is greater than the second current threshold.
4. The photovoltaic system according to claim 1, wherein, The combiner box includes a first controller; the first controller is configured to determine that a short circuit fault has occurred between the combiner box switch and the DC side of the inverter when the input voltage of the combiner box is less than a third voltage threshold and the input current of the combiner box flows from the photovoltaic panel to the combiner box and is greater than a third current threshold, and control the corresponding combiner box switch to open.
5. The photovoltaic system according to claim 4, wherein, The inverter includes a second controller; the second controller is configured to determine that a short circuit fault has occurred between the combiner box switch and the DC side of the inverter when the current flowing through the excitation fuse is from the excitation fuse to the combiner box and is greater than the third current threshold, and the input voltage of the inverter is less than the fourth voltage threshold, and then control the excitation fuse to open.
6. The photovoltaic system according to any one of claims 1-5, wherein, The photovoltaic system includes at least two combiner boxes; the input terminal of each combiner box is connected to the corresponding photovoltaic panel, and the output terminal of each combiner box is connected in parallel to the DC side of the inverter; The inverter is equipped with a corresponding excitation fuse for each of the combiner boxes.
7. The photovoltaic system according to claim 6, wherein, Each of the junction boxes includes the first controller; the first controllers of all junction boxes communicate with each other; For any of the first controllers, if the input voltage of all the combiner boxes is less than the fifth voltage threshold, and the input current of all the combiner boxes flows from the corresponding photovoltaic panel to the combiner box and is greater than the fourth current threshold, then if a fault is determined to have occurred inside the inverter, the controller will control all the combiner box switches to disconnect.
8. The photovoltaic system according to claim 7, wherein, The inverter includes a second controller and a DC switch; the second end of the excitation fuse is connected to the first end of the DC switch, and the second end of the DC switch is connected to the power conversion circuit; The second controller is configured to determine that a short-circuit fault has occurred inside the inverter when the current direction of the excitation fuse corresponding to each combiner box is from the corresponding combiner box to the excitation fuse and is greater than the fourth current threshold, and the input voltage of the inverter is less than the sixth voltage threshold, and then control the DC switch of the inverter to open.
9. A control method for a photovoltaic system, The method includes: In the event of a short circuit fault between the combiner box switch and the photovoltaic panel, the combiner box switch in the combiner box is controlled to open, and the current flowing through the excitation fuse exceeds a first current threshold, thereby controlling the excitation fuse to open; the combiner box switch is connected in series between the input terminal and the output terminal of the combiner box; the excitation fuse is connected between the DC side of the inverter and the power conversion circuit; In the event of a short circuit fault between the combiner box switch and the DC side of the inverter, the combiner box switch and the corresponding excitation fuse are controlled to disconnect. In the event of a short circuit fault inside the inverter, the combiner box switch is disconnected.
10. The method according to claim 9, wherein, The method further includes: If the input voltage of the combiner box is less than a first voltage threshold, and / or the input current of the combiner box flows from the combiner box to the photovoltaic panel and is greater than a second current threshold, then a short circuit fault is determined to have occurred between the combiner box switch and the photovoltaic panel; the first current threshold is greater than the second current threshold.
11. The method according to claim 9 or 10, wherein, The method further includes: If the current flowing through the excitation fuse is directed from the excitation fuse to the combiner box and is greater than the second current threshold, and the input voltage of the inverter is less than the second voltage threshold, then a short circuit fault is determined between the combiner box switch connected to the excitation fuse and the photovoltaic panel; if the current flowing through the excitation fuse is directed from the excitation fuse to the combiner box and is greater than the first current threshold, the excitation fuse is controlled to open; the first current threshold is greater than the second current threshold.
12. The method according to claim 9, wherein, The method further includes: If the input voltage of the combiner box is less than the third voltage threshold, and the input current of the combiner box flows from the photovoltaic panel to the combiner box and is greater than the third current threshold, then a short circuit fault is determined to have occurred between the combiner box switch and the DC side of the inverter.
13. The method according to claim 12, wherein, The method further includes: If the current flowing through the excitation fuse is directed from the excitation fuse to the combiner box and is greater than the third current threshold, and the input voltage of the inverter is less than the fourth voltage threshold, then a short circuit fault is determined to have occurred between the combiner box switch and the DC side of the inverter.
14. The method according to claim 9, wherein, The method further includes: If the input voltage of all the combiner boxes is less than the fifth voltage threshold, and the input current of all the combiner boxes flows from the corresponding photovoltaic panel to the combiner box and is greater than the fourth current threshold, it is determined that there is a fault inside the inverter, and the corresponding combiner box switch is controlled to open.
15. The method according to claim 14, wherein, The method further includes: If the current direction of the excitation fuse corresponding to each combiner box is from the corresponding combiner box to the excitation fuse and is greater than the fourth current threshold, and the input voltage of the inverter is less than the sixth voltage threshold, it is determined that a short circuit fault has occurred inside the inverter.
16. A control device comprising a processor and a memory, the memory for storing programs, instructions or code, and the processor for executing the programs, instructions or code in the memory to perform the control method as described in any one of claims 9-15.
17. A computer-readable storage medium storing a computer program, said computer program being loaded by a processor to execute the control method as described in any one of claims 9-15.