A bus protection circuit and a photovoltaic system
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-26
- Publication Date
- 2026-08-14
AI Technical Summary
[0005]本实用新型提供一种汇流保护电路，旨在解决光伏系统中单个汇流箱支路短路时其他支路间电流倒灌导致故障扩大的问题
所述N个光伏板的输出端一一对应连接至所述N个汇流箱的输入端，所述N个汇流箱的输出端形成所述光伏系统的N路汇流箱支路；所述逆变电路的正输入端连接至所述汇流保护电路的母线电容的正极端，所述逆变电路的负输入端连接至所述母线电容的负极端，所述逆变电路的输出端连接至交流电网。本实用新型将N路汇流箱支路划分为m组，每组内的k路汇流箱支路的正极输出端短接后，通过对应的正极隔离开关以及隔离二极管接入母线电容的正极端；每组内的k路汇流箱支路的负极输出端与至少一个不同组的汇流箱支路的负极输出端短接后，通过对应的负极隔离开关接入母线电容的负极端。由于将汇流箱支路的正极输出端和负极输出端交错分组连接，配合隔离开关和防反二极管进行物理隔离，在单一汇流箱支路短路时，其他支路的正负极输出端无法通过短接点形成回路，从而能够有效阻断故障电流向其他支路扩散，有效防止故障范围的扩大。
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Figure CN224637743U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of photovoltaic technology, and in particular relates to a bus protection circuit and a photovoltaic system. Background Technology
[0002] In a grid-connected photovoltaic (PV) power generation system, the combiner box, as a key device connecting PV modules and inverters, is mainly used to collect the DC power output from multiple PV panels and transmit it to the inverter for inversion processing, ultimately achieving grid connection. As the scale of PV power plants expands, a single inverter often needs to be connected to multiple combiner boxes to improve power generation efficiency. Therefore, the combiner box's current collection method and protection mechanism directly affect the safety, stability, and reliability of the entire PV system.
[0003] Currently, the mainstream combiner scheme for the DC side of photovoltaic inverters is as follows: the output terminals of multiple combiner boxes are first protected against overcurrent by fuses, and then the positive output terminals of all combiner boxes are short-circuited and combined, and the negative output terminals are short-circuited and combined to form a total DC circuit; the combined circuit is then connected to the DC side of the photovoltaic inverter through a main disconnect switch for on / off control and fault protection.
[0004] However, since the positive and negative output terminals of all combiner boxes are directly short-circuited and combined, when a short circuit fault occurs in a DC cable or combiner box, the short-circuit point will become a node for energy conduction. The electrical energy of other normal combiner boxes will continuously transmit energy to the short-circuit point through this short-circuit point, affecting all photovoltaic panels and combiner boxes connected to the short-circuit point, causing the fault range to expand rapidly. In severe cases, it may even cause the entire photovoltaic subarray to shut down or cause safety accidents such as fires. Utility Model Content
[0005] This utility model provides a combiner protection circuit, which aims to solve the problem of fault expansion caused by backflow of current between other branches when a single combiner box branch is short-circuited in a photovoltaic system.
[0006] This utility model is implemented as follows: a combiner protection circuit is applied to a photovoltaic system, wherein the photovoltaic system includes N combiner box branches, the N combiner box branches are divided into m groups, each group includes k combiner box branches, where N is an integer ≥ 2, k is an integer ≥ 2, and m is an integer; The bus protection circuit includes a bus capacitor, at least one isolation diode, and m isolation switches, each isolation switch including a positive isolation switch and a negative isolation switch; After each positive output terminal of the k-way combiner box branch in each group is short-circuited, it is connected to the first terminal of the positive disconnect switch of the corresponding disconnect switch. The second terminal of the positive disconnect switch is connected to the positive terminal of the isolation diode, and the negative terminal of the isolation diode is connected to the positive terminal of the bus capacitor. Each negative output terminal of the k-way combiner branch in each group is short-circuited to the negative output terminal of at least one combiner branch in a different group, and then connected to the first terminal of the negative disconnect switch of the corresponding disconnect switch. The second terminal of all negative disconnect switches is connected to the negative terminal of the bus capacitor. Among them, the negative output terminals of the k-way combiner branches in the same group are not short-circuited to each other.
[0007] Furthermore, the value of k is 2, and each group includes 2 combiner box branches.
[0008] Furthermore, the value of k is 3, and each group includes 3 combiner box branches.
[0009] Furthermore, the value of k is 4, and each group includes 4 combiner box branches.
[0010] Furthermore, the isolation diode is of one type, and the positive terminal of each isolation switch is short-circuited and connected to the positive terminal of the isolation diode, while the negative terminal of the isolation diode is connected to the positive terminal of the bus capacitor.
[0011] Furthermore, the number of the isolation diodes is m; The positive terminal of each isolating switch is connected to the positive terminal of an isolating diode, and the negative terminals of the m isolating diodes are short-circuited and connected to the positive terminal of the bus capacitor.
[0012] This utility model also provides a photovoltaic system, which includes the bus protection circuit as described in any of the preceding claims.
[0013] Furthermore, the photovoltaic system also includes an inverter circuit, N photovoltaic panels, and N combiner boxes; The output terminals of the N photovoltaic panels are connected one-to-one to the input terminals of the N combiner boxes, and the output terminals of the N combiner boxes form the N combiner box branches of the photovoltaic system. The positive input terminal of the inverter circuit is connected to the positive terminal of the bus capacitor of the combiner protection circuit, the negative input terminal of the inverter circuit is connected to the negative terminal of the bus capacitor, and the output terminal of the inverter circuit is connected to the AC power grid. This invention divides the N combiner box branches into m groups. The positive output terminals of k combiner box branches within each group are short-circuited and connected to the positive terminal of the bus capacitor through a corresponding positive isolating switch and an isolation diode. The negative output terminals of k combiner box branches within each group are short-circuited to the negative output terminals of at least one combiner box branch from a different group and connected to the negative terminal of the bus capacitor through a corresponding negative isolating switch. By interleaving the positive and negative output terminals of the combiner box branches together and using disconnect switches and reverse protection diodes for physical isolation, when a single combiner box branch is short-circuited, the positive and negative output terminals of other branches cannot form a loop through the short-circuit point. This effectively blocks the fault current from spreading to other branches and prevents the fault range from expanding. Attached Figure Description
[0014] Figure 1 This is a schematic diagram of the circuit structure of the first embodiment of the bus protection circuit provided by this utility model; Figure 2 This is a schematic diagram of the circuit structure of the second embodiment of the bus protection circuit provided by this utility model; Figure 3 This is a schematic diagram of the circuit structure of the third embodiment of the bus protection circuit provided by this utility model; Figure 4 This is a schematic diagram of the circuit structure of the fourth embodiment of the bus protection circuit provided by this utility model. Detailed Implementation
[0015] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.
[0016] This invention divides N combiner box branches into m groups. The positive output terminals of k combiner box branches within each group are short-circuited and connected to the positive terminal of the bus capacitor via a corresponding positive isolating switch and an isolation diode. The negative output terminals of k combiner box branches within each group are short-circuited to the negative output terminals of at least one combiner box branch from a different group and connected to the negative terminal of the bus capacitor via a corresponding negative isolating switch. By alternately connecting the positive and negative output terminals of the combiner box branches, and using isolating switches and reverse protection diodes for physical isolation, when a single combiner box branch is short-circuited, the positive and negative output terminals of other branches cannot form a loop through the short-circuit point. This effectively blocks the spread of fault current to other branches and prevents the expansion of the fault range. This solves the problem in existing technologies where the direct convergence of the positive and negative output terminals of all combiner box branches leads to current backflow and fault expansion during short circuits.
[0017] Example 1 Reference Figure 1 This utility model discloses a combiner protection circuit applied to a photovoltaic system. The photovoltaic system includes an inverter circuit, N photovoltaic panels, and N combiner boxes. The output terminals of the N photovoltaic panels are connected one-to-one to the input terminals of the N combiner boxes. The output terminals of the N combiner boxes serve as N combiner box branches of the photovoltaic system. The positive input terminal of the inverter circuit is connected to the positive terminal of the bus capacitor C1 of the combiner protection circuit, and the negative input terminal of the inverter circuit is connected to the negative terminal of the bus capacitor C1. The output terminal of the inverter circuit is connected to the AC power grid.
[0018] The N combiner box branches are pre-divided into m groups, each group including k combiner box branches, where N is an integer ≥ 2, k is an integer ≥ 2, m is an integer, and m = N / k.
[0019] The bus protection circuit includes a bus capacitor C1, at least one isolation diode D1, and m isolation switches S1~Sn, each isolation switch including a positive isolation switch and a negative isolation switch; Each positive output terminal of a k-way combiner branch within each group is short-circuited and connected to the first terminal of the corresponding positive disconnect switch. The second terminal of the positive disconnect switch is connected to the positive terminal of the isolation diode D1, and the negative terminal of the isolation diode D1 is connected to the positive terminal of the bus capacitor C1. Each negative output terminal of a k-way combiner branch within each group is short-circuited with the negative output terminal of at least one combiner branch from a different group and connected to the first terminal of the corresponding negative disconnect switch. The second terminal of the negative disconnect switch is connected to the negative terminal of the bus capacitor C1. The negative output terminals of k-way combiner branches within the same group are not short-circuited; that is, the negative output terminals of k-way combiner branches within the same group are not connected to each other and have no short-circuit points.
[0020] In this embodiment, the number of isolation diodes can be one, and it can be set between the convergence point of the positive terminals of each disconnecting switch and the positive terminal of the bus capacitor C1; that is, the second terminals of the positive terminals of each disconnecting switch are short-circuited to form a convergence point, which is connected to the positive terminal of the isolation diode, and the negative terminal of the isolation diode is connected to the positive terminal of the bus capacitor C1. Alternatively, the number of isolation diodes can be m, with one isolation diode connected to the second terminal of the positive terminal of each disconnecting switch, and then connected to the positive terminal of the bus capacitor C1; that is, the second terminal of the positive terminal of each disconnecting switch is connected to the positive terminal of one isolation diode, and the negative terminals of the m isolation diodes are short-circuited and connected to the positive terminal of the bus capacitor C1.
[0021] In this embodiment, each group of combiner box branches corresponds to a disconnecting switch. Each disconnecting switch integrates a positive disconnecting switch and a negative disconnecting switch, which are used to control the on / off state of the positive and negative circuits of the corresponding group respectively, so as to achieve precise isolation in case of fault.
[0022] In this embodiment, the positive output terminals of the k-way combiner box branches within each group are short-circuited together. That is, the positive output terminals of all the k-way combiner box branches within the same group converge to a single node. This node is connected to the first terminal of the positive disconnect switch of the corresponding disconnect switch in this group. The second terminal of this positive disconnect switch is connected to the anode of the isolation diode D1, and finally, through the cathode of the isolation diode D1, it is connected to the positive terminal of the bus capacitor C1. This configuration achieves current convergence at the positive output terminals of the combiner box branches within the group, while also utilizing the unidirectional conduction characteristic of the isolation diode D1 to cut off the current reverse flow path.
[0023] The negative output terminals of the k-way combiner branches within each group are not short-circuited, meaning that the negative output terminals of combiner branches within the same group are not short-circuited. Furthermore, each negative output terminal of a k-way combiner branch within the same group is short-circuited to the negative output terminal of at least one combiner branch from a different group. The combiner node after cross-group short-circuiting is connected to the negative terminal of the bus capacitor C1 via the negative isolating switch of the corresponding isolating switch. This differentiated structure, where the negative output terminals of combiner branches within the same group are not short-circuited and cross-group short-circuiting is staggered, prevents direct conduction of the negative output terminals of combiner branches within the same group, structurally blocking the path for fault propagation within the group. Simultaneously, cross-group short-circuiting still achieves the negative combiner function, balancing the circuit's combiner and protection requirements. It should be understood that the negative output terminals of each combiner box branch within the same group need to be short-circuited across groups with the negative output terminals of combiner box branches in other groups, and the total number of negative output terminals of combiner box branches that are short-circuited across groups can be consistent with the number of combiner box branches in its group, such as the value k.
[0024] In other words, by interleaving the positive and negative output terminals of the combiner box branches and using disconnect switches and anti-reverse diodes to achieve physical isolation, when a single combiner box branch is short-circuited, the positive and negative output terminals of other branches cannot form a loop through the short-circuit point, thereby effectively blocking the spread of fault current to other branches and preventing the expansion of the fault range.
[0025] Example 2 In one embodiment, k is 2, and each group includes 2 combiner box branches. That is, the N combiner box branches of the photovoltaic system are divided into m groups, each group including 2 combiner box branches. For example, if the system has 64 combiner box branches, these 64 combiner box branches are divided into 32 groups, each group containing 2 combiner box branches. This embodiment provides a specific connection structure example to facilitate understanding of the technical concept of this utility model.
[0026] Reference Figure 2 PV1+ and PV1- are the positive and negative output terminals of the first combiner box branch; PV2+ and PV2- are the positive and negative output terminals of the second combiner box branch; PV3+ and PV3- are the positive and negative output terminals of the third combiner box branch; PV4+ and PV4- are the positive and negative output terminals of the fourth combiner box branch, and so on. Taking the above four combiner box branches as an example, the first and second branches are divided into the first group, and the third and fourth branches are divided into the second group.
[0027] On the positive connection, the positive output terminals of each combiner box branch in the same group are short-circuited: PV1+ and PV2+ of the first group are short-circuited to form a node and connected to the first terminal of the positive disconnect switch of disconnect switch S1; PV3+ and PV4+ of the second group are short-circuited to form a node and connected to the first terminal of the positive disconnect switch of disconnect switch S2.
[0028] In the negative connection, the negative output terminals of each combiner box branch in the same group are not short-circuited, and are summarized by cross-group staggered short-circuiting: PV1 of the first group and PV3 of the second group are short-circuited to form a node connected to the first terminal of the negative disconnect switch of disconnect switch S1, and PV2 of the first group and PV4 of the second group are short-circuited to form another node connected to the first terminal of the negative disconnect switch of disconnect switch S2.
[0029] By short-circuiting the positive output terminals of each combiner box branch within the same group, and ensuring that the negative output terminals of each combiner box branch within the group are not short-circuited and are interconnected across groups, combined with the on / off control of the disconnecting switch and the unidirectional conductivity of the isolation diode, physical fault isolation can be achieved. When a short circuit occurs in one combiner box branch, the positive and negative output terminals of other normal branches cannot form a conductive loop through the short-circuit point, thereby effectively blocking the spread of fault current to other branches and preventing the fault range from expanding. It should be noted that the specific grouping method (such as the combination and division of combiner box branches) and the cross-group connection objects of the negative output terminals within the group are not fixed and can be flexibly set according to the actual scale and layout requirements of the photovoltaic system. The above is only an example of cross-group connection and is not intended to limit this utility model.
[0030] Example 3 In one embodiment, k is 3, and each group includes 3 combiner box branches. That is, the N combiner box branches of the photovoltaic system are divided into m groups, and each group includes 3 combiner box branches. This embodiment provides a specific connection structure example to facilitate understanding of the technical concept of this utility model.
[0031] Reference Figure 3 Similarly to the above embodiments, PV1+ and PV1- are the positive and negative output terminals of the first combiner box branch; PV2+ and PV2- are the positive and negative output terminals of the second combiner box branch; PV3+ and PV3- are the positive and negative output terminals of the third combiner box branch; PV4+ and PV4- are the positive and negative output terminals of the fourth combiner box branch; PV5+ and PV5- are the positive and negative output terminals of the fifth combiner box branch; PV6+ and PV6- are the positive and negative output terminals of the sixth combiner box branch; PV7+ and PV7- are the positive and negative output terminals of the seventh combiner box branch; PV8+ and PV8- are the positive and negative output terminals of the eighth combiner box branch; PV9+ and PV9- are the positive and negative output terminals of the ninth combiner box branch, and so on.
[0032] Taking the above-mentioned 9-way combiner box branch as an example, the first, fourth and seventh routes are divided into the first group; the second, fifth and eighth routes are divided into the second group; and the third, sixth and ninth routes are divided into the third group.
[0033] In the positive connection, the positive output terminals of the junction box branches in the same group are short-circuited: PV1+, PV4+ and PV7+ of the first group are short-circuited to form a node connected to the first terminal of the positive disconnect switch of disconnect switch S1; PV2+, PV5+ and PV8+ of the second group are short-circuited to form a node connected to the first terminal of the positive disconnect switch of disconnect switch S2; PV3+, PV6+ and PV9+ of the third group are short-circuited to form a node connected to the first terminal of the positive disconnect switch of disconnect switch S3.
[0034] In the negative connection, the negative output terminals of the combiner box branches in the same group are not short-circuited, and cross-group staggered short-circuiting is adopted: PV1- of the first group, PV6- of the third group and PV8- of the second group are short-circuited to form a node connected to the first terminal of the negative disconnect switch of disconnect switch S1; PV2- of the second group, PV4- of the first group and PV9- of the third group are short-circuited to form a node connected to the first terminal of the negative disconnect switch of disconnect switch S2; PV3- of the third group, PV5- of the second group and PV7- of the first group are short-circuited to form a node connected to the first terminal of the negative disconnect switch of disconnect switch S3.
[0035] By short-circuiting the positive output terminals of the current collector branch within a group, isolating the negative output terminals of the current collector branch within a group, and interleaving the negative output terminals across groups, combined with the on / off control of the disconnecting switch and the unidirectional conductivity of the isolation diode, physical fault isolation can be achieved. When a short circuit occurs in one current collector branch, the positive and negative output terminals of other normal branches cannot form a conductive loop through the short-circuit point, thereby effectively blocking the spread of fault current to other branches and preventing the fault range from expanding. It is understood that the above-mentioned method of short-circuiting each negative output terminal with the negative output terminals of two different groups is only an example of cross-group connection and is not intended to limit this utility model.
[0036] Example 4 In one embodiment, k is 4, and each group includes 4 combiner box branches. That is, the N combiner box branches of the photovoltaic system are divided into m groups, and each group includes 4 combiner box branches. This embodiment provides a specific connection structure example to facilitate understanding of the technical concept of this utility model.
[0037] Reference Figure 4 Similarly to the above embodiments, in the positive connection: the positive output terminals PV1+, PV5+, PV9+ and PV13+ of each combiner box branch in the same group are shorted to form a node and connected to the first terminal of the positive disconnect switch of disconnect switch S1; PV2+, PV6+, PV10+ and PV14+ of the same group are shorted to form a node and connected to the first terminal of the positive disconnect switch of disconnect switch S2; PV3+, PV7+, PV11+ and PV15+ of the same group are shorted to form a node and connected to the first terminal of the positive disconnect switch of disconnect switch S3; PV4+, PV8+, PV12+ and PV16+ of the same group are shorted to form a node and connected to the first terminal of the positive disconnect switch of disconnect switch S4...
[0038] For the negative connection, the negative output terminals of each combiner box branch within the same group are not short-circuited, and cross-group staggered short-circuiting is used. Short-circuiting the negative output terminals PV1-, PV8-, PV11-, and PV14- of four combiner box branches in different groups forms a node connected to the first terminal of the negative disconnect switch of disconnect switch S1; short-circuiting the negative output terminals PV2-, PV5-, PV12-, and PV15- of four combiner box branches in different groups forms a node connected to the first terminal of the negative disconnect switch of disconnect switch S2; short-circuiting the negative output terminals PV3-, PV6-, PV9-, and PV16- of four combiner box branches in different groups forms a node connected to the first terminal of the negative disconnect switch of disconnect switch S3; short-circuiting the negative output terminals PV4-, PV7-, PV10-, and PV13- of four combiner box branches in different groups forms a node connected to the first terminal of the negative disconnect switch of disconnect switch S4, and so on.
[0039] By short-circuiting the positive output terminals of the combiner box branches within a group, while ensuring that the negative output terminals of the combiner box branches within a group are not short-circuited and that the negative output terminals are staggered across groups, combined with the on / off control of the disconnecting switch and the unidirectional conductivity of the isolation diode, physical fault isolation can be achieved. When a short circuit occurs in one combiner box branch, the positive and negative output terminals of other normal branches cannot form a conductive loop through the short-circuit point, thereby effectively blocking the spread of fault current to other branches and preventing the fault range from expanding. It is understood that the above-mentioned method of short-circuiting each negative output terminal to three negative output terminals located in different groups is only an example of cross-group connection and is not intended to limit this utility model.
[0040] This utility model also provides a photovoltaic system, which includes the bus protection circuit as described in any of the preceding claims. The detailed structure of the bus protection circuit can be found in the above embodiments and will not be repeated here. It is understood that since the above-described bus protection circuit is used in the photovoltaic system of this utility model, the embodiments of the photovoltaic system of this utility model include all the technical solutions of all embodiments of the above-described bus protection circuit, and the achieved technical effects are completely the same, and will not be repeated here.
[0041] Furthermore, the photovoltaic system also includes an inverter circuit, N photovoltaic panels, and N combiner boxes; The output terminals of the N photovoltaic panels are connected one-to-one to the input terminals of the N combiner boxes, and the output terminals of the N combiner boxes serve as the N combiner box branches of the photovoltaic system. The positive input terminal of the inverter circuit is connected to the positive terminal of the bus capacitor of the combiner protection circuit, the negative input terminal of the inverter circuit is connected to the negative terminal of the bus capacitor, and the output terminal of the inverter circuit is connected to the AC power grid.
[0042] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.
Claims
1. A bus protection circuit, characterized by, The method is applied to a photovoltaic system, wherein the photovoltaic system includes N combiner box branches, the N combiner box branches are divided into m groups, each group includes k combiner box branches, where N is an integer ≥ 2, k is an integer ≥ 2, and m is an integer; The bus protection circuit includes a bus capacitor, at least one isolation diode, and m isolation switches, each isolation switch including a positive isolation switch and a negative isolation switch; After each positive output terminal of the k-way combiner box branch in each group is short-circuited, it is connected to the first terminal of the positive disconnect switch of the corresponding disconnect switch. The second terminal of the positive disconnect switch is connected to the positive terminal of the isolation diode, and the negative terminal of the isolation diode is connected to the positive terminal of the bus capacitor. Each negative output terminal of the k-way combiner branch in each group is short-circuited to the negative output terminal of at least one combiner branch in a different group, and then connected to the first terminal of the negative disconnect switch of the corresponding disconnect switch. The second terminal of all negative disconnect switches is connected to the negative terminal of the bus capacitor. Among them, the negative output terminals of the k-way combiner branches in the same group are not short-circuited to each other.
2. The bus protection circuit of claim 1, wherein, The value of k is 2, and each group includes 2 combiner box branches.
3. The bus protection circuit of claim 1, wherein, The value of k is 3, and each group includes 3 junction box branches.
4. The bus protection circuit of claim 1, wherein, The value of k is 4, and each group includes 4 combiner box branches.
5. The bus protection circuit according to any one of claims 1 to 4, wherein The isolation diode is of one type. The positive terminal of each isolation switch is short-circuited and connected to the positive terminal of the isolation diode. The negative terminal of the isolation diode is connected to the positive terminal of the bus capacitor.
6. The bus protection circuit according to any one of claims 1 to 4, wherein The number of isolation diodes is m; The positive terminal of each isolating switch is connected to the positive terminal of an isolating diode, and the negative terminals of the m isolating diodes are short-circuited and connected to the positive terminal of the bus capacitor.
7. A photovoltaic system characterized by, The photovoltaic system includes a bus protection circuit as described in any one of claims 1-6.
8. The photovoltaic system of claim 7, wherein, The photovoltaic system also includes an inverter circuit, N photovoltaic panels, and N combiner boxes; The output terminals of the N photovoltaic panels are connected one-to-one to the input terminals of the N combiner boxes, and the output terminals of the N combiner boxes form the N combiner box branches of the photovoltaic system; the positive input terminal of the inverter circuit is connected to the positive terminal of the bus capacitor of the combiner protection circuit, the negative input terminal of the inverter circuit is connected to the negative terminal of the bus capacitor, and the output terminal of the inverter circuit is connected to the AC power grid.