Power conversion equipment

Abstract

The present application discloses a power conversion device, including: a switch device, a power conversion circuit and a controller; the switch device includes a multi-layer switch stacked along the extension direction of the rotating shaft, the multi-layer switch includes a first layer switch and a second layer switch, the number of the first layer switches is less than the number of the second layer switches; the current carrying capacity of the first layer switch is greater than the current carrying capacity of the second layer switch; the first layer switch is used to connect to the first pole of N photovoltaic strings at the same time, and each second layer switch is used to connect to the second pole of some of the N photovoltaic strings; when there is a fault in the N photovoltaic strings, the multi-layer switches are all disconnected in linkage, and at most two or three photovoltaic strings in the N photovoltaic strings are connected in parallel. In this way, different access numbers of photovoltaic strings can be adapted, the number of switch layers can be saved and safety can be ensured.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic power generation, and in particular to a power conversion device. Background Art

[0002] At present, photovoltaic systems mainly include single-stage power conversion mode and two-stage power conversion mode. The single-stage power conversion mode refers to the direct current of the photovoltaic array being directly converted into alternating current through a direct current / alternating current (DC / AC) circuit, while the two-stage power conversion mode refers to the direct current of the photovoltaic array being first converted into alternating current through a direct current / direct current (DC / DC) conversion circuit, and then converted into alternating current through a second-stage DC / AC conversion circuit. Since the two-stage power conversion mode is more efficient than the single-stage power conversion mode, the two-stage power conversion mode is increasingly widely used in photovoltaic power generation systems.

[0003] Generally, the capacity of a single photovoltaic string is limited. In order to increase the capacity, multiple photovoltaic strings are connected in parallel at the input end of the DC / DC conversion circuit, that is, the positive poles of multiple photovoltaic strings are connected together, and the negative poles of multiple photovoltaic strings are connected together. However, when one of the photovoltaic strings is connected in reverse, the current of other photovoltaic strings will be fed back into the reversed photovoltaic string. Since the anti-parallel diodes of the solar panels in the photovoltaic string can withstand a limited current, when the current of multiple photovoltaic strings is fed back into one photovoltaic string, it will cause damage to the solar panels in the photovoltaic string.

[0004] In the prior art, a circuit breaker or fuse is usually connected in series with each photovoltaic string, so that when a photovoltaic string fails and is back-fed by other photovoltaic strings, the connection between the photovoltaic string and other photovoltaic strings can be disconnected. However, this solution has too many circuit breakers or fuses. As the number of photovoltaic strings currently connected increases, it is easy to cause the power conversion equipment to be too large and the cost to be too high. Summary of the invention

[0005] The present application provides a power conversion device that can isolate the fault in time when reverse connection occurs in a photovoltaic string, thereby ensuring the safety of the photovoltaic string and complete isolation from the power circuit, while also saving the number of switch layers in the switch device and reducing the size and cost of the switch device.

[0006] The embodiment of the present application provides a power conversion device, including: a switch device, a power conversion circuit and a controller, wherein the switch device is connected between a photovoltaic string and a power conversion circuit. The switch device includes a rotating shaft and a multi-layer switch stacked along the extension direction of the rotating shaft, wherein the multi-layer switch includes a first-layer switch and at least two second-layer switches, wherein the number of the first-layer switches is less than the number of the second-layer switches; and the current carrying capacity of the first-layer switch is greater than the current carrying capacity of the second-layer switch. The first poles of N photovoltaic strings are each connected to a first-layer switch, and the second poles of some photovoltaic strings in the N photovoltaic strings are connected to the second-layer switches in the multi-layer switch. The first pole is a positive pole or a negative pole, and the second pole is another pole opposite to the first pole; and N is a positive integer greater than or equal to 2. The controller is used to: when there is a reverse connection fault in the photovoltaic string, or when there is a short circuit fault in the photovoltaic string, or when there is a short circuit fault at the output end of the power conversion circuit, control the multi-layer switches in the switch device to be disconnected in a linkage manner to disconnect the positive and negative poles of the photovoltaic string from the power conversion circuit, and connect at most two or three photovoltaic strings in the N photovoltaic strings in parallel.

[0007] In the above implementation scheme, the switch includes a multi-layer switch, and the multi-layer switch is a linkage switch as a whole, that is, a multi-P (Pole) switch, and the multi-layer switches are disconnected or turned on at the same time. When there is a reverse connection fault in N photovoltaic strings, the multi-layer switches are all disconnected, that is, as long as a reverse connection fault occurs in one of the photovoltaic strings, all pole switches in the switch device are disconnected. Among them, the multi-layer switch of the embodiment of the present application is provided with a first layer switch and a second layer switch of different current carrying capacity, so that the layer switches with different current carrying capacity can be adapted to the access of different numbers of photovoltaic strings, so that the grouping and connection mode of the photovoltaic strings can be more flexible. Further, since the current carrying capacity of the first layer switch in the multi-layer switch is greater than that of the second layer switch, the first poles of the N photovoltaic strings can share a first layer switch, which is equivalent to the one pole of the N photovoltaic strings being integrated into one first layer switch. When the number of photovoltaic strings connected increases day by day, the first layer switch with large current carrying capacity can greatly reduce the number of layer switches required to be connected when the N photovoltaic strings are integrated, and there is no need to use multiple layer switches with small current carrying capacity for shunting. In addition, N photovoltaic strings can be grouped according to the specifications or circuit design of the photovoltaic strings, wherein the second poles of at least two groups of photovoltaic strings can be connected to the corresponding second-layer switches, that is, each second-layer switch can be connected to the second poles of a part of the N photovoltaic strings. In the above implementation scheme, it is not limited that the second poles of all the photovoltaic strings in the N photovoltaic strings are connected to the second-layer switches of a switching device. For example, other groups in the N photovoltaic strings can also be shut off through other switching devices. However, no matter what connection relationship is adopted, when the multi-layer switches of the switching device are controlled to be disconnected, at most two or three photovoltaic strings in the N photovoltaic strings are connected in parallel. In this way, when a reverse connection or short circuit fault occurs in the photovoltaic strings, at most only one or two photovoltaic strings will reverse the faulty string, which will not affect the safety of the photovoltaic strings. That is to say, the above-mentioned implementation scheme of the present application enhances the current-carrying capacity of the first-layer switch, thereby enabling more photovoltaic modules or those with larger output currents to be connected to one first-layer switch together, thereby reducing the number of first-layer switches, and by connecting the second poles of N photovoltaic strings to different second-layer switches, flexible grouping of N photovoltaic strings is achieved, while ensuring that the photovoltaic strings are not subjected to excessive backflow current. That is, the above-mentioned implementation scheme can greatly reduce the number of layers of multi-layer switches in the switching device, thereby reducing the size and cost of the opening device and the power conversion equipment, while also ensuring the safety of the photovoltaic strings and power circuits, and simplifying the control and circuit connection.

[0008] In a possible implementation, along the extension direction of the rotation axis, the height of the switches at the first layer is greater than or equal to the height of the switches at the second layer.

[0009] In a possible implementation manner, the radial length of the switches of the first layer is greater than or equal to the radial length of the switches of the second layer, wherein the direction of the radial length is perpendicular to the extension direction of the rotation axis.

[0010] In the above two implementation schemes, since the current carrying capacity of the first layer switch is greater than that of the second layer switch, the components inside the layer switch of the first layer switch also need to adapt to the large current carrying capacity. Therefore, the layer height of the first layer switch can be greater than or equal to the layer height of the second layer switch, or the radial length of the first layer switch is greater than or equal to the radial length of the second layer switch. Although this will partially increase the volume of the first layer switch, compared with the connection of the first poles of N photovoltaic strings through multiple layer switches with small current carrying capacity, the number of layer switches is reduced, so the overall volume of the switch device can still be greatly reduced.

[0011] In a possible implementation, the current carrying capacity of at least two second-layer switches is consistent, or the current carrying capacity of at least two second-layer switches is different. When the current carrying capacity of at least two second-layer switches is different, different numbers of second poles of photovoltaic strings can be adapted for access.

[0012] In the above implementation scheme, the second layer switches may all adopt a unified layer switch with the same flow capacity, or may adopt layer switches with different flow capacities to adapt to the flow capacities of different groups according to the grouping situation.

[0013] In a possible implementation, N photovoltaic strings can be divided into M groups of photovoltaic strings, any group of photovoltaic strings includes one photovoltaic string, or two or three photovoltaic strings connected in parallel, wherein two second-layer switches of at least two second-layer switches are connected to the second poles of two photovoltaic strings of the M groups of photovoltaic strings. That is, among all the second-layer switches, at least two second-layer switches are connected one-to-one with the second poles of two photovoltaic strings of the M groups of photovoltaic strings. For example, a second-layer switch is connected to a photovoltaic string group A, and another second-layer switch is connected to a photovoltaic string group B. If there are more groups of photovoltaic strings, they can be connected through more second-layer switches of the present switch device, or through other switch devices, or can be implemented in other ways.

[0014] In a possible implementation, the at least two second-layer switches include M second-layer switches, and the M second-layer switches are connected to the second poles of the M groups of photovoltaic strings in a one-to-one correspondence. That is, the second poles of all grouped photovoltaic strings are connected to the power circuit through corresponding connections with the multiple second-layer switches of the switch device.

[0015] In the above two implementation schemes, N photovoltaic strings can be reasonably grouped and connected to the corresponding second-layer switches, so that each group has at most two or three photovoltaic strings connected in parallel. In this way, if a faulty photovoltaic string occurs in a group, after disconnecting the multi-layer switch, there will be at most one or two photovoltaic strings with reverse current, which can ensure the safety of the photovoltaic strings. At the same time, the increase in the number of photovoltaic strings in each group can also reduce the number of second-layer switches, thereby further reducing the number and volume of layer switches of the entire switch device.

[0016] In a possible implementation, when N is an even number, each group of photovoltaic strings includes two photovoltaic strings connected in parallel; when N is an odd number, each group of photovoltaic strings in M-1 groups of photovoltaic strings includes two photovoltaic strings connected in parallel, and the remaining group of photovoltaic strings includes one photovoltaic string.

[0017] In the above implementation scheme, the number of photovoltaic strings in each group is limited to two and is as close to two as possible, that is, when N is an even number, the N photovoltaic strings can be grouped in pairs, and when N is an odd number, the other N-1 photovoltaic strings are grouped in pairs, and the remaining 1 photovoltaic string forms a group by itself. In this way, when a photovoltaic string fails, after the switch device is disconnected, the faulty string can withstand at most one reverse current, which further ensures the safety of the photovoltaic string, while minimizing the number of photovoltaic string groupings under this safety level, thereby minimizing the number of second-layer switches and reducing the size of the switch device.

[0018] In a possible implementation, N photovoltaic strings can be connected to a common positive pole or a common negative pole. For example, when the N photovoltaic strings are connected to a common positive pole, the positive poles of the N photovoltaic strings are connected together, and the positive poles of the N photovoltaic strings are connected to the input end of the power conversion circuit through a first-layer switch in the multi-layer switch; the N photovoltaic strings are grouped in pairs, and the negative pole of each photovoltaic string is connected to the input end of the power conversion circuit through a second-layer switch in the multi-layer switch; for example, when the N photovoltaic strings are connected to a common negative pole, the negative poles of the N photovoltaic strings are connected together, and the negative poles of the N photovoltaic strings are connected to the input end of the power conversion circuit through a first-layer switch in the multi-layer switch, and the N photovoltaic strings are grouped in pairs, and the positive pole of each photovoltaic string is connected to the input end of the power conversion circuit through a second-layer switch in the multi-layer switch.

[0019] In a possible implementation, in order to reliably disconnect the switch in the switch device when a reverse connection fault occurs in a photovoltaic string, the switch device provided in the embodiment of the present application may also include a trip device. The controller is used to send a disconnection instruction to the trip device when there is a reverse connection fault in the photovoltaic string, or when there is a short circuit fault in the photovoltaic string, or when there is a short circuit fault at the output end of the power conversion circuit, and the trip device operates according to the disconnection instruction and drives all the multi-layer switches to disconnect; before the trip device is reset, the multi-layer switches remain in the disconnected state. That is, before the trip device is reset, the multi-layer switches remain in the disconnected state, thereby avoiding the multi-layer switches from erroneously operating and closing before the fault is resolved.

[0020] In a possible implementation, any layer switch of the switch device includes: a housing, a moving contact and at least one stationary contact arranged in the housing, the moving contact rotates relative to the housing; the moving contact is relatively fixed to the rotating shaft, and the rotating shaft is used to drive the moving contact to rotate so as to separate from or contact the stationary contact; when the multi-layer switch is disconnected, the moving contact and the stationary contact in the multi-layer switch are separated; when the multi-layer switch is connected, the moving contact and the stationary contact in the multi-layer switch are in contact. In some possible implementations, the layer switch closest to the rotating shaft can be directly fixed to the rotating shaft, and the moving contacts between the remaining layer switches can be fixedly connected to the adjacent moving contacts, for example, mutually clamped, so as to achieve that when the rotating shaft rotates, the moving contacts of all layer switches are simultaneously driven to separate from or contact the stationary contacts.

[0021] In the above implementation scheme, each layer of switch device is provided with a moving contact and a stationary contact, and the stationary contact can be arranged on the rotation path of the moving contact, so that the moving contact and the stationary contact can be separated or contacted. The moving contact and the rotating shaft of each layer of switch are relatively fixed, and can be rotated relative to the housing. Specifically, they can be fixed directly to the rotating shaft, or can be achieved by fixing the moving contacts of adjacent layers. Therefore, the rotating shaft can drive the rotation of the moving contacts of all layers, so that the switches of all layers can be disconnected or connected in a linked manner.

[0022] In one possible implementation, at least one static contact includes a first static contact and a second static contact, one end of the moving contact is used to contact or separate with the first static contact, and the other end of the moving contact is used to contact or separate with the second static contact; the first static contact is used to be electrically connected to the photovoltaic string, and the second static contact is used to be electrically connected to the power conversion circuit.

[0023] In the above implementation scheme, the two static contacts are electrically connected to the photovoltaic string and the power conversion circuit respectively, and when the two ends of the moving contact are separated from the two static contacts, the electrical connection between the photovoltaic string and the power conversion circuit is disconnected, and when the two ends of the moving contact are in contact with the two static contacts, a loop is formed, thereby completing the electrical connection between the photovoltaic string and the power conversion circuit.

[0024] In a possible implementation, the first static contact of any layer of switches includes a connecting portion extending out of the housing, the connecting portion being used to be electrically connected to the photovoltaic string; the area of ​​the connecting portion of the first layer of switches is larger than the area of ​​the connecting portion of the second layer of switches.

[0025] In the above implementation scheme, since the current carrying capacity of the first layer switch is greater than that of the second layer switch, the connecting part of the first static contact of the first layer switch also needs to adapt to the large current carrying capacity. Therefore, the area of ​​the connecting part of the first layer switch is greater than the area of ​​the connecting part of the second layer switch.

[0026] In one possible implementation, the power conversion device also includes a circuit board, and the power conversion circuit is located on the circuit board; the second static contact of any layer of switches includes a pin portion extending out of the shell, and the pin portion is used to electrically connect to the circuit board to connect to the power conversion circuit.

[0027] In the above implementation scheme, the switch device can be directly plugged into the circuit board through the pin portion, and then connected to the power conversion circuit through the circuit board routing. This can save the space occupied by cable connection, thereby saving the internal space of the power conversion equipment and improving the power density.

[0028] In a possible implementation, the number of pins of the first-layer switch is greater than the number of pins of the second-layer switch.

[0029] In a possible implementation, the width of the pin portion of the first layer switch is greater than the width of the pin portion of the second layer switch.

[0030] In the above two implementation schemes, since the current-carrying capacity of the first-layer switch is greater than that of the second-layer switch, the pins of the first-layer switch also need to adapt to the large current-carrying capacity. Therefore, the number of pins of the first-layer switch is greater than the number of pins of the second-layer switch, or the pin width of the first-layer switch is greater than the pin width of the second-layer switch.

[0031] In a possible implementation, the multi-layer switch includes a plurality of first-layer switches, and each of the first-layer switches is spaced apart by at least two second-layer switches.

[0032] In the above implementation, since the positive and negative poles of the N photovoltaic strings are connected through the first layer switches and the second layer switches respectively, the multiple first layer switches are separated by at least two second layer switches, that is, the first layer switches and the multiple second layer switches are interspersed, which can facilitate the connection of the positive and negative poles of the photovoltaic strings with the first layer switches and the second layer switches, and avoid the entanglement of cables.

[0033] In a possible implementation, the multi-layer switch includes a plurality of first-layer switches, the plurality of first-layer switches are stacked and arranged adjacent to each other along the rotation axis, and at least two second-layer switches are stacked and arranged adjacent to each other along the rotation axis.

[0034] In the above implementation, since the first-layer switches and the second-layer switches are used to connect the positive and negative poles of the photovoltaic string respectively, the risk of short circuit caused by the positive and negative poles being too close can be better avoided by centrally arranging multiple first-layer switches and multiple second-layer switches.

[0035] In one possible implementation, the presence of a reverse connection fault in a photovoltaic string can be determined by the current direction of the photovoltaic string. When the current direction of the photovoltaic string is reversed, it indicates that a reverse connection fault exists. That is, the photovoltaic system provided in this embodiment may also include: an input current detection circuit for detecting the current of each photovoltaic string in the N photovoltaic strings; when the controller determines that the current of any photovoltaic string in the N photovoltaic strings is reversed based on the current of each photovoltaic string, the controller controls the multi-layer switches to be disconnected.

[0036] In a possible implementation, it also includes: an input current detection circuit and an input voltage detection circuit; the input current detection circuit detects the current of each photovoltaic string in the N photovoltaic strings; the input voltage detection circuit detects the voltage between the first end of the first layer switch and the first end of each switch in the M second layer switches to obtain M voltages; the controller is used to control the multi-layer switches to be disconnected when at least one of the M voltages is less than the first voltage threshold and the current of at least one photovoltaic string in the N photovoltaic strings is greater than the first current threshold. As long as the voltage of a group of photovoltaic strings is low, some photovoltaic strings may have a short circuit fault. It should be understood that when a short circuit fault exists, the voltage of the photovoltaic string will drop and the current will rise. In order to accurately judge the short circuit fault, the voltage and current can be double judged. As long as there is a short circuit fault in the photovoltaic string, all switches in the fault isolation circuit are disconnected, thereby isolating the faulty photovoltaic string and protecting the subsequent circuit from the harm of the short circuit fault.

[0037] In a possible implementation, the power conversion circuit includes: a DC / DC conversion circuit, that is, the photovoltaic string is connected to the input end of the DC / DC conversion circuit through a switching device, and the output end of the DC / DC conversion circuit is connected to the input end of the DC / AC conversion circuit.

[0038] In a possible implementation, the embodiment of the present application can not only detect whether a short circuit fault occurs at the input end of the DC / DC conversion circuit, but also detect whether a short circuit fault occurs at the output end of the DC / DC conversion circuit. When a short circuit fault occurs at the output end of the DC / DC conversion circuit, in order to avoid the expansion of the fault range and play a protective role, it is also necessary to control all layer switches in the switch device to be disconnected to play a role in fault isolation. That is, the photovoltaic system provided by this embodiment also includes: an output current detection circuit for detecting the current at the second end of the first layer switch; an output voltage detection circuit for detecting the output voltage of the DC / DC conversion circuit; a controller for controlling the disconnection of multiple layers of switches when the current at the second end of the first layer switch is greater than the second current threshold and the voltage at the output end of the DC / DC conversion circuit is less than the second preset voltage.

[0039] In a possible implementation, since any hardware may fail during operation, in order to ensure that the photovoltaic system operates safely and reliably, two controllers may be set in the photovoltaic system to form a backup, that is, to achieve redundant control, so that when one of the controllers fails, normal control operation is not affected. That is, the photovoltaic system provided in this embodiment, the controller includes: a main controller and a backup controller; the main controller and the backup controller are both used to control the disconnection of multiple layers of switches when there is a reverse connection fault in N photovoltaic strings.

[0040] In one possible implementation, in order to ensure the reliability of power supply, the embodiment of the present application provides two auxiliary sources to power the controller, that is, the photovoltaic system provided in this embodiment also includes: a main auxiliary source and a secondary auxiliary source; the main auxiliary source and the secondary auxiliary source are both used to power the main controller and the backup controller; the main auxiliary source is connected to the output end of the DC / DC conversion circuit; the secondary auxiliary source is connected to the first end of the switching device.

[0041] In one possible implementation, in order to reliably power the controller under any circumstances, the photovoltaic system provided in the embodiment of the present application adopts a competitive power supply method, that is, it also includes: a first power supply circuit, which is used to obtain power from the group with the highest voltage among M groups of photovoltaic strings to provide power for the auxiliary auxiliary source.

[0042] In a possible implementation, the first power supply circuit includes: 2 (M+1) diodes and a first capacitor; each switch in the M+1 layer switches corresponds to two diodes in the 2 (M+1) diodes; the first end of each switch in the M+1 layer switches is respectively connected to the first end and the second end of the first capacitor through a forward biased diode and a reverse biased diode; the first end of each switch in the M+1 layer switches is connected to the corresponding photovoltaic string, and the second end of each switch in the M+1 layer switches is connected to the input end of the DC / DC conversion circuit.

[0043] In a possible implementation, the photovoltaic system provided in the embodiment of the present application also includes a second power supply circuit for the main auxiliary source; the second power supply circuit includes: a first diode, a second diode, a third diode, a fourth diode and a second capacitor; the cathode and anode of the first diode are respectively connected to the positive output end of the DC / DC conversion circuit and the first end of the second capacitor; the anode and cathode of the second diode are respectively connected to the positive output end of the DC / DC conversion circuit and the second end of the second capacitor; the anode and cathode of the third diode are respectively connected to the first end of the second capacitor and the negative output end of the DC / DC conversion circuit, and the anode and cathode of the fourth diode are respectively connected to the negative output end of the DC / DC conversion circuit and the second end of the second capacitor; the main auxiliary source is connected to the positive output end of the DC / DC conversion circuit. Since the power supply of the main auxiliary source comes from the output end of the DC / DC conversion circuit, and the general photovoltaic system includes multiple DC / DC conversion circuits, and the output ends of the multiple DC / DC conversion circuits are connected in parallel, therefore, even if all layer switches in the switch device are disconnected and all photovoltaic strings connected to the input end of the DC / DC conversion circuit are isolated, the output end of the DC / DC conversion circuit can also have electricity, that is, from other parallel DC / DC conversion circuits. This ensures the power supply of the main auxiliary source, thereby ensuring the power supply of the controller.

[0044] In a possible implementation, it includes: a plurality of switch devices and a plurality of DC / DC conversion circuits; the plurality of switch devices and the plurality of DC / DC conversion circuits correspond one to one.

[0045] In a possible implementation, the power conversion circuit includes: a DC / AC conversion circuit.

[0046] Based on a power conversion device provided in the above embodiment, an embodiment of the present application further provides a fault isolation method, which is applied to the above power conversion device, including: obtaining the current of each photovoltaic string in N photovoltaic strings; judging the current reverse of any photovoltaic string in the N photovoltaic strings according to the current of each photovoltaic string, and judging the presence of a reverse connection fault in the N photovoltaic strings; when a reverse connection fault exists in the N photovoltaic strings, controlling the multi-layer switches in the switch device to disconnect in conjunction to disconnect the positive and negative poles of the photovoltaic strings from the power conversion circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1a A schematic diagram of a photovoltaic system provided in an embodiment of the present application;

[0048] Figure 1b A schematic diagram of another photovoltaic system provided in an embodiment of the present application;

[0049] Figure 2 A schematic diagram of another photovoltaic system provided in an embodiment of the present application;

[0050] Figure 3 A schematic diagram of a plurality of photovoltaic strings connected in parallel at the input end of a DC / DC conversion circuit;

[0051] Figure 4 A schematic diagram of a photovoltaic system with a switch device provided in an embodiment of the present application;

[0052] Figure 5 A schematic diagram of the connection relationship between a switch device and a photovoltaic string provided in an embodiment of the present application;

[0053] Figure 6a A schematic diagram of the connection relationship between another switch device and a photovoltaic string provided in an embodiment of the present application;

[0054] Figure 6b A schematic diagram of the connection relationship between another switch device and a photovoltaic string provided in an embodiment of the present application;

[0055] Figure 6c A schematic diagram of the connection relationship between another switch device and a photovoltaic string provided in an embodiment of the present application;

[0056] Figure 7 A schematic diagram of the connection relationship between another switch device and a photovoltaic string provided in an embodiment of the present application;

[0057] Figure 8a A schematic diagram of the connection relationship between a plurality of switch devices and a photovoltaic string provided in an embodiment of the present application;

[0058] Figure 8b A schematic diagram of another connection relationship between multiple switch devices and photovoltaic strings provided in an embodiment of the present application;

[0059] Fig. 9 A schematic diagram of the structure of a switch device provided in an embodiment of the present application;

[0060] Fig.10 An exploded diagram of a switch device provided in an embodiment of the present application;

[0061] Fig.11 A schematic diagram of the structure of a first-layer switch provided in an embodiment of the present application;

[0062] Fig.12 A schematic diagram of the structure of a second layer switch provided in an embodiment of the present application;

[0063] Fig.13 A schematic diagram of the structure of another second layer switch provided in an embodiment of the present application;

[0064] Fig.14 For this application Fig. 9A schematic structural diagram of a switch device provided in an embodiment from another angle;

[0065] Fig.15 A schematic diagram of the structure of another switch device provided in an embodiment of the present application;

[0066] Fig.16 For this application Fig.15 A schematic structural diagram of a switch device provided in an embodiment from another angle;

[0067] Fig.17 A schematic diagram of another photovoltaic system provided in an embodiment of the present application;

[0068] Fig.18 A schematic diagram of another photovoltaic system provided in an embodiment of the present application;

[0069] Fig.19 A schematic diagram of another photovoltaic system provided in an embodiment of the present application;

[0070] Fig. 20 A schematic diagram of another photovoltaic system provided in an embodiment of the present application;

[0071] Fig.21 A schematic diagram of a photovoltaic system including multiple DC / DC conversion circuits provided in the present application;

[0072] Fig. 22 A schematic diagram of a DC combiner box provided in this application. DETAILED DESCRIPTION

[0073] The terms "first", "second", etc. in the following description are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0074] In addition, in the present application, directional terms such as "upper" and "lower" may be defined including but not limited to the orientation relative to the schematic placement of the components in the drawings. It should be understood that these directional terms may be relative concepts, which are used for relative description and clarification, and may change accordingly according to the change in the orientation of the components in the drawings.

[0075] In this application, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. In addition, the term "coupling" can be a way of achieving electrical connection for signal transmission. "Coupling" can be a direct electrical connection or an indirect electrical connection through an intermediate medium.

[0076] An embodiment of the present application relates to a photovoltaic system, which may include two-stage power conversion or single-stage power conversion. A photovoltaic system including a two-stage power conversion circuit is first introduced below. In order to enable those skilled in the art to better understand the technical solution provided by the embodiment of the present application, the photovoltaic system provided by the embodiment of the present application is introduced below in conjunction with the accompanying drawings.

[0077] See also Figure 1a , which is a schematic diagram of a photovoltaic system provided in an embodiment of the present application.

[0078] The photovoltaic system provided in the embodiment of the present application includes a DC / DC conversion circuit 200 and a DC / AC conversion circuit 300, wherein the input end of the DC / DC conversion circuit 200 is connected to a plurality of photovoltaic strings, and the input end of the DC / DC conversion circuit 200 is connected to a photovoltaic array 100, wherein the photovoltaic array 100 includes a plurality of photovoltaic strings. Figure 1a Four photovoltaic strings are used as an example for introduction, namely photovoltaic strings PV1 to PV4. Photovoltaic strings PV1 to PV4 can be connected in parallel to the input end of the DC / DC conversion circuit 200, thereby increasing the input current of the DC / DC conversion circuit 200. The output end of the DC / DC conversion circuit 200 is connected to the DC / AC conversion circuit 300.

[0079] The DC / DC conversion circuit 200 is used to complete the conversion from DC to DC, and the DC / AC conversion circuit 300 completes the conversion from DC to AC. The output end of the DC / AC conversion circuit 300 can be connected to a transformer, that is, connected to a power grid through a transformer.

[0080] in addition, Figure 1a What is shown is only a schematic diagram of one DC / DC conversion circuit 200 connected to a DC / AC conversion circuit 300. Generally, in order to increase the output power of the DC / AC conversion circuit 300, multiple DC / DC conversion circuits 200 can be connected to the input end of the DC / AC conversion circuit 300, and the input end of each DC / DC conversion circuit 200 can be connected to multiple photovoltaic strings.

[0081] It should be understood that Figure 1aThe power conversion circuit in the photovoltaic system shown includes a DC / DC conversion circuit 200 and a DC / AC conversion circuit 300. In addition, the photovoltaic system provided in the embodiment of the present application may also include a power conversion circuit that only includes a DC / AC conversion circuit, but does not include a DC / DC conversion circuit. Figure 1b As shown, this figure is a schematic diagram of another photovoltaic system provided in an embodiment of the present application.

[0082] Compare Figure 1a and Figure 1b It can be seen that Figure 1b The photovoltaic strings PV1-PV4 are directly connected to the input end of the DC / AC conversion circuit 300. The technical solutions provided in the following embodiments of the present application do not limit the specific implementation form of the power conversion circuit, that is, Figure 1a The power conversion circuit shown includes a DC / DC conversion circuit 200 and a DC / AC conversion circuit 300, which can also be Figure 1b The power conversion circuit shown only includes a DC / AC conversion circuit 300. The following mainly introduces the power conversion circuit including a DC / DC conversion circuit as an example.

[0083] See also Figure 2 , which is a schematic diagram of another photovoltaic system provided in an embodiment of the present application.

[0084] Figure 2 In the description, the output ends of the two DC / DC conversion circuits are connected to the DC / AC conversion circuit 300 as an example, that is, the output end of the first DC / DC conversion circuit 200a and the output end of the second DC / DC conversion circuit 200b are connected in parallel to the input end of the DC / AC conversion circuit 300. The first DC / DC conversion circuit 200a and the second DC / DC conversion circuit 200b can be integrated in a DC combiner box 1000, and the DC combiner box 1000 can have a maximum power point tracking function.

[0085] Figure 2 In the example, the input end of the first DC / DC conversion circuit 200a is connected to the photovoltaic string PV1 and the photovoltaic string PV2, and the input end of the second DC / DC conversion circuit 200b is connected to the photovoltaic string PV3 and the photovoltaic string PV4.

[0086] Figure 1a , Figure 1b or Figure 2In the photovoltaic system shown, since the input end of the DC / DC conversion circuit is connected to multiple photovoltaic strings, generally multiple photovoltaic strings are connected in parallel. When one of the photovoltaic strings is reversely connected, that is, the positive and negative poles are reversed, the current of other photovoltaic strings will be fed back into the reversed photovoltaic string. Since the anti-parallel diodes in the photovoltaic strings can withstand a limited current, when the current of multiple photovoltaic strings is fed back into one photovoltaic string, it will cause damage to the batteries in the photovoltaic string.

[0087] See also Figure 3 , which is a schematic diagram of a plurality of photovoltaic strings connected in parallel at the input end of a DC / DC conversion circuit.

[0088] Let's continue with the example of four photovoltaic strings. Figure 3 The photovoltaic string is equivalent to a battery. Traditionally, the positive poles PV1+-PV4+ of the four photovoltaic strings are connected together to the positive input terminal of the DC / DC conversion circuit 200, and the negative poles PV1--PV4- of the four photovoltaic strings are connected together to the negative input terminal of the DC / DC conversion circuit 200. For example, when PV4 is reversely connected, that is, the positive and negative poles are reversed, it can be seen that the positive poles of PV1-PV3 are connected to the positive input terminal of the DC / DC conversion circuit 200, and the positive pole of PV4 is connected to the negative input terminal of the DC / DC conversion circuit 200. Figure 3 The picture shows the reverse connection of PV string PV4. Figure 3 It can be seen that the current of PV1-PV3 is represented by a dotted line with an arrow, and the current of PV4 is represented by a solid line with an arrow, that is, the current of PV1-PV3 will be reversed into PV4, and PV4 will be damaged because of the large current. Figure 3 In the process, fuses are added to each photovoltaic string, that is, fuses F1-F4 are connected in series to four photovoltaic strings. Fuses will increase circuit losses. On the other hand, the disconnection of fuses requires twice the input current, and the reliability is relatively low and the cost is high.

[0089] In order to solve the problem caused by the reverse connection of the above photovoltaic strings, the present application embodiment provides a power conversion device 10, which is applied to the above photovoltaic system, and can be specifically an inverter. Figure 4, which is a schematic diagram of a photovoltaic system with a switch device provided in an embodiment of the present application. Specifically, the power conversion device 10 in the embodiment of the present application includes a switch device 400, a power conversion circuit (for example, a DC / DC conversion circuit 200 and a DC / AC conversion circuit 300) and a controller 600, and N photovoltaic strings (for example, PV1~PV4) are connected to the input end of the power conversion circuit through the switch device 400. When a photovoltaic string fails, the controller 600 can control the switch device 400 to disconnect from the input end of the power conversion circuit to achieve fault isolation. Among them, the switch device 400 includes a rotating shaft and a multi-layer switch stacked along the extension direction of the rotating shaft. The multi-layer switch in the embodiment of the present application can realize simultaneous linkage action (opening or closing) through the rotation of the rotating shaft. As long as one of the photovoltaic strings or multiple photovoltaic strings connected to the multi-layer switch has a reverse connection fault, all switches of the multi-layer switch will be disconnected in a linkage manner through the driving of the rotating shaft.

[0090] Specifically, the multi-layer switch in the embodiment of the present application includes a first-layer switch and at least two second-layer switches, and the number of the first-layer switches is less than the number of the second-layer switches. The first-layer switch is used to simultaneously connect to the first poles of N photovoltaic strings, and each second-layer switch is used to connect to the second poles of some photovoltaic strings in the N photovoltaic strings. Among them, the first pole is a positive pole or a negative pole, and the second pole is another pole opposite to the first pole. For example, if the first pole is a positive pole, the second pole is a negative pole; if the first pole is a negative pole, the second pole is a positive pole. The controller 600 is used to: when there is a reverse connection fault in the N photovoltaic strings, or when there is a short circuit fault in the N photovoltaic strings, or when a short circuit fault occurs at the output end of the power conversion circuit, the multi-layer switches in the control switch device 400 are all disconnected in a linkage manner to disconnect the positive and negative poles of the N photovoltaic strings from the power conversion circuit, and connect at most two or three photovoltaic strings in the N photovoltaic strings in parallel.

[0091] This means that N photovoltaic strings can be grouped according to the specifications or circuit design of the photovoltaic strings, wherein the second poles of at least two groups of photovoltaic strings can be connected to the corresponding second-layer switches, that is, each second-layer switch can be connected to the second poles of a portion of the N photovoltaic strings. In the above implementation scheme, first-layer switches and second-layer switches with different current carrying capacities are set in the multi-layer switch, so that layer switches with different current carrying capacities can adapt to the access of different numbers of photovoltaic strings, thereby making the grouping and connection of photovoltaic strings more flexible to adapt to more scenarios and product requirements.

[0092] It should be noted that the embodiments of the present application do not limit the second poles of all the N photovoltaic strings to be connected to the second-layer switches of the same switching device. For example, other groups in the N photovoltaic strings can also be shut down by other switching devices. However, no matter what connection relationship is adopted, when the multi-layer switches of the switching device are controlled to be disconnected, at most two or three photovoltaic strings in the N photovoltaic strings are connected in parallel. In this way, the safety of the photovoltaic strings can be ensured, and the photovoltaic strings can be flexibly grouped. The following text will first take the case where the second poles of all the photovoltaic strings in the N photovoltaic strings are connected to the second-layer switches of the same switching device as an example. That is, the N photovoltaic strings are divided into M groups of photovoltaic strings, and the second-layer switches also include M, and the M second-layer switches are connected one-to-one with the second poles of the M groups of photovoltaic strings.

[0093] Specifically, the N photovoltaic strings are divided into at least two groups of photovoltaic strings, wherein the first poles of the N photovoltaic strings are connected to the first layer switches, and the second poles of each group of photovoltaic strings are connected to the second layer switches. It can be understood that in this connection mode, the first layer switches are connected to all the N photovoltaic strings, and each second layer switch is connected to part of the N photovoltaic strings.

[0094] When grouping N photovoltaic strings, the same number of N photovoltaic strings can have different grouping methods, but the size of the reverse injection current that the photovoltaic strings can withstand must be met. For example, if the specifications of the photovoltaic strings can only withstand the reverse injection current of one photovoltaic string, then each group can only include at most two parallel photovoltaic strings, or only one photovoltaic string. For another example, if the specifications of the photovoltaic strings can withstand the reverse injection current of two photovoltaic strings, then each group can include at most two or three parallel photovoltaic strings, or only one photovoltaic string.

[0095] For example, when N is 5, the N photovoltaic strings can be divided into two groups, one group includes 2 photovoltaic strings in parallel, and the other group includes 3 photovoltaic strings in parallel; the N photovoltaic strings can also be divided into three groups, the first group includes 1 photovoltaic string, and the second and third groups each include 2 photovoltaic strings in parallel. Of course, each group can also include only one photovoltaic string, so the N photovoltaic strings are divided into 5 groups.

[0096] It can be understood that in the embodiment of the present application, the number of groups is consistent with the number of second-layer switches. The fewer the number of groups, the fewer the number of second-layer switches in the switch device, and the cost and volume will also be reduced. Therefore, while ensuring safety, fewer groups can be set to save the number of layer switches. The following embodiments are mainly illustrated by two-by-two parallel connections as a group, but it should be understood that the embodiments of the present application are not limited to this, and the grouping method can be more flexible according to the scene and product requirements.

[0097] In order to better protect the photovoltaic strings from being subjected to too much current when reversely connected, every two photovoltaic strings can be divided into a group, and the second pole of each photovoltaic string group corresponds one-to-one to a second-layer switch in the multi-layer switch.

[0098] The following is an example of N photovoltaic strings, with every two photovoltaic strings being grouped together.

[0099] N photovoltaic strings share a common positive pole, and the positive poles of the N photovoltaic strings are connected to the input end of the power conversion circuit through a first-layer switch in the multi-layer switch; N photovoltaic strings are grouped in pairs, and the negative pole of each photovoltaic string group is connected to the input end of the power conversion circuit through a second-layer switch in the multi-layer switch;

[0100] or,

[0101] N photovoltaic strings share a common negative pole, and the negative poles of the N photovoltaic strings are connected to the input end of the power conversion circuit through a first-layer switch in the multi-layer switch. The N photovoltaic strings are grouped in pairs, and the positive pole of each photovoltaic string is connected to the input end of the power conversion circuit through a second-layer switch in the multi-layer switch.

[0102] N photovoltaic strings can be divided into M groups. When N is an even number, M=N / 2; when N is an odd number, M=(N+1) / 2. Each photovoltaic string in the M-1 photovoltaic strings includes two photovoltaic strings connected in parallel, and the remaining photovoltaic string includes one photovoltaic string. The switch device includes M+1 layers of switches (one first layer switch and M second layer switches). The M+1 layers of switches are linked, that is, closed or opened at the same time. The first poles of the N photovoltaic strings are connected to the input end of the DC / DC conversion circuit through a first layer switch. The second poles of the N photovoltaic strings are connected to the input end of the DC / DC conversion circuit through M layers of switches.

[0103] The connection method in the above embodiment can ensure that when a reverse connection or short circuit fault occurs in the photovoltaic string, after the switch device is disconnected, the photovoltaic string will not be subjected to excessive reverse current, thereby ensuring the safety of the photovoltaic string, while saving the number of layer switches, thereby reducing the volume and cost.

[0104] For easier understanding, refer to Figure 5 , Figure 5 Schematic diagram of the connection relationship between a switch device 400 and a photovoltaic string in an embodiment of the present application. Figure 5 In the illustrated embodiment, N is taken as 4 for example, that is, N photovoltaic strings include PV1 to PV4, wherein S1 is a schematic diagram of a first-layer switch, and S2 and S3 are schematic diagrams of two second-layer switches, respectively.

[0105] Understandably, in Figure 5In the implementation mode, the first pole is the positive pole of the photovoltaic module, the second pole is the negative pole of the photovoltaic module, the first layer switch S1 is connected to the positive poles (first poles) of the four photovoltaic strings at the same time, and the two second layer switches S2 and S3 are respectively connected to the negative poles (second poles) of two of the four photovoltaic strings. Figure 5 As shown, when one of the four photovoltaic strings (such as PV4) has a reverse connection or short circuit fault, the controller 600 will control the multi-layer switches S1, S2 and S3 in the switch device 400 to disconnect in a coordinated manner to disconnect the positive and negative poles of the four photovoltaic strings from the power conversion circuit to prevent the fault from spreading to other circuits. Continuing with the reverse connection of the photovoltaic string PV4 as an example, since PV1- and PV2- are not connected to PV4-, when PV4 is reversely connected, only the current of PV3 is reversed into PV4. Therefore, the current reversed into PV4 is small. Since PV4 can withstand the reverse current of a string, PV4 will not be damaged. This is different from Figure 3 This connection method can not only ensure the safety of photovoltaic strings, but also greatly save the number of layer switches.

[0106] It should be noted that the embodiments of the present application do not limit whether the first pole is a positive pole or a negative pole, that is, N photovoltaic strings can be connected to a common positive pole or a common negative pole. For the convenience of description, the following embodiments are introduced by taking N photovoltaic strings connected to a common positive pole as an example. When N photovoltaic strings are connected to a common positive pole, the positive poles of the N photovoltaic strings are connected together and connected to the positive input terminal of the power conversion circuit through the first layer of switches. The negative poles of the N photovoltaic strings are respectively connected to the negative input terminal of the power conversion circuit through the corresponding second layer of switches.

[0107] It should be understood that the reverse connection fault of the photovoltaic strings in all the embodiments of the present application means that at least one photovoltaic string is reversely connected, that is, as long as there is a reverse connection of one photovoltaic string, it is necessary to disconnect the connection between the N photovoltaic strings and the power conversion circuit.

[0108] It can be seen that in the embodiment of the present application, the first layer of switches needs to connect the positive or negative poles of all N photovoltaic strings, while the second layer of switches only connects the positive or negative poles of a portion of the N photovoltaic strings, so the first layer of switches requires a larger current capacity than the second layer of switches. Therefore, in the embodiment of the present application, the current capacity of the first layer of switches is greater than the current capacity of the second layer of switches.

[0109] In the previous implementation, the current carrying capacity of each layer of switches in the multi-layer switch is the same. Therefore, under the current increasing demand for the number of connected photovoltaic strings, the first layer switch cannot connect more photovoltaic modules. For example, if the current carrying capacity of each layer switch can only connect less than N photovoltaic modules, it is impossible to connect the positive poles of all N photovoltaic strings with only one first layer switch, and more first layer switches are required, which will increase the number of layer switches or limit the number of connected photovoltaic strings.

[0110] Therefore, the embodiment of the present application increases the current carrying capacity of the first-layer switch so that the current carrying capacity of the first-layer switch is greater than that of the second-layer switch, so as to ensure the safety of the photovoltaic strings while enabling only one layer of the first-layer switch to connect a certain pole of all N photovoltaic strings, thereby further saving the number of layer switches.

[0111] Figure 5 The example shows the connection relationship of N=4. For further reference Figure 6a and Figure 6b , Figure 6a A schematic diagram of the connection relationship between another switch device and a photovoltaic string provided in an embodiment of the present application, Figure 6b This is a schematic diagram of the connection relationship between another switch device and a photovoltaic string provided in an embodiment of the present application. It can be seen that: Figure 6a and Figure 6b The following are schematic diagrams of the connection relationship of a photovoltaic system when N=6 and N=5. The positive poles of the N photovoltaic strings are all connected to the first layer switch S1 at the same time. Figure 6a In the embodiment of , N photovoltaic strings are divided into three groups of photovoltaic strings, each group includes two photovoltaic strings connected in parallel, and the negative pole of each photovoltaic string group corresponds to the second layer switches S2 to S4. That is, in Figure 6a In the embodiment shown, the current carrying capacity of the first layer switch S1 needs to reach the current input of 6 or more photovoltaic strings, and the current carrying capacity of the second layer switches S2 to S4 needs to reach the current input of 2 or more photovoltaic strings. Figure 6b In the embodiment shown, N photovoltaic strings are divided into three groups of photovoltaic strings, two groups include two photovoltaic strings connected in parallel, and one group includes one photovoltaic string. The negative pole of each photovoltaic string group corresponds to the second layer switches S2 to S4. That is, Figure 6b In the embodiment shown, the current carrying capacity of the first layer switch S1 needs to reach the current input of 5 or more photovoltaic strings, the current carrying capacity of the second layer switches S2~S3 needs to reach the current input of 2 or more photovoltaic strings, and the current carrying capacity of the second layer switch S4 needs to reach the current input of 1 or more photovoltaic strings.

[0112] In the embodiment of the present application, the first poles of N photovoltaic strings can also be connected to the power conversion circuit through multiple first-layer switches. For example, when the number of N strings increases, the first poles connected by only one first-layer switch may exceed the current carrying capacity of one first-layer switch. In this case, multiple first-layer switches can also be used for connection. Figure 6c , Figure 6c A schematic diagram of the connection relationship between another switch device and a photovoltaic string provided in an embodiment of the present application. Figure 6c In the illustrated embodiment, the first poles of the N photovoltaic strings may be connected to the DC / DC conversion circuit via two first-layer switches S1 and S2 , respectively.

[0113] It should be understood that the above embodiments are only examples, and the embodiments of the present application are not limited to the above number of photovoltaic strings. In practical applications, a larger number of photovoltaic strings can be supported. Of course, the embodiments of the present application can also support the access of fewer photovoltaic strings.

[0114] Figure 7 A schematic diagram of the connection relationship between another switch device 400 and a photovoltaic string provided in an embodiment of the present application. Figure 7 The figure is a schematic diagram of the connection relationship of a photovoltaic system when N=3. The positive poles of N photovoltaic strings are all connected to the first layer switch S1 at the same time. Figure 7 In the embodiment, N photovoltaic strings are divided into two groups of photovoltaic strings, one group includes two photovoltaic strings connected in parallel, and the other group includes one photovoltaic string, and the negative pole of each photovoltaic string corresponds to the second layer switches S2-S3. Figure 7 In the illustrated embodiment, the current carrying capacity of the first-layer switch S1 can reach the current input of 3 or more photovoltaic strings, the current carrying capacity of the second-layer switch S2 needs to reach the current input of 2 or more photovoltaic strings, and the current carrying capacity of the second-layer switch S3 needs to reach the current input of 1 or more photovoltaic strings.

[0115] It should be noted that fewer PV strings connected does not necessarily mean less current input, nor does it mean that the current capacity of the corresponding layer switches must be smaller. In fact, this is related to the power output capacity of the PV strings and the architecture of the entire PV system. Figure 7 The current carrying capacity of the first layer switch S1 in the embodiment shown is not necessarily less than Figure 5~Figure 6b The current carrying capacity of the first layer switch of the embodiment shown. For example, when the output power of the photovoltaic string reaches a higher level, the input current after the first poles of three photovoltaic strings (such as PV1+~PV3+) are combined may be similar to the input current after the first poles of six photovoltaic strings (PV1+~PV6+) are combined, that is, Figure 7 In the embodiment shown, the current carrying capacity of the first layer switch S1 may be Figure 6b The current carrying capacity of the first layer switches S1 in the illustrated embodiment is similar.

[0116] In an embodiment of the present application, the current carrying capacity of multiple second-layer switches can be consistent to simplify the design. For example, multiple second-layer switches can all use standardized layer switches with consistent current carrying capacity, which can support the current input of two photovoltaic strings in parallel. Even if some second-layer switches are only connected to one photovoltaic string, a layer switch that supports the current input of two photovoltaic strings in parallel can be used. Of course, the current carrying capacity of multiple second-layer switches can also be inconsistent. The second-layer switches with corresponding current carrying capacity are configured according to each grouping situation, which can make the product design more flexible. For example, for the second-layer switch connecting two parallel photovoltaic components, a layer switch that supports the current input of two photovoltaic strings in parallel is used. For the second-layer switch connecting three parallel photovoltaic components, a layer switch that supports the current input of three photovoltaic strings in parallel is used.

[0117] As mentioned above, the embodiment of the present application does not limit the second poles of all the N photovoltaic strings to be connected to the second-layer switches of the same switch device, so it is also possible that the second poles of some of the N photovoltaic strings are connected in other ways. For example, when there are multiple switch devices, the second poles of some of the strings can be connected to other switch devices.

[0118] refer to Figure 8a , Figure 8a A schematic diagram of the connection relationship between multiple switch devices and photovoltaic strings provided in an embodiment of the present application. A possible implementation method when N=5 is used as an example for illustration, but the connection method and the number of photovoltaic strings in the present application are not limited to this. It can be seen that Figure 6b The embodiments shown are basically similar, the main difference is that among the N photovoltaic strings, the second pole (PV5-) of one of the strings is not connected to the DC / DC conversion circuit through the second layer switch of the switch device 400, but is connected through the second layer switch S4' of another switch device 400'. That is, the second layer switches of other switch devices can be reused to achieve joint control. For example, in one scenario, the second layer switch S4' in another switch device 400' is only connected to the second pole of one photovoltaic string, such as PV12-, and its current carrying capacity has the ability to connect to two photovoltaic strings, then PV5- and PV12- can be connected together to the second layer switch S4' of the switch device 400'. In this way, the number of layer switches of the switch device can be further reduced by reusing the layer switches of different switch devices.

[0119] It should be noted that when the second-layer switch is connected to the negative pole, the second-layer switch S4' of the switch device 400' can be connected to the negative pole of the same DC / DC conversion circuit as the second-layer switches S2 and S3 of the switch device 400', or can be connected to the negative pole of another DC / DC conversion circuit. Since multiple DC / DC conversion circuits generally share a common negative pole, both connection methods are possible.

[0120] Further references Figure 8b , Figure 8b Another schematic diagram of the connection relationship between multiple switch devices and photovoltaic strings provided in an embodiment of the present application. In this embodiment, the power converter has two switch devices 400 and 400', and the switch device 400 and the switch device 400' are connected between N+M photovoltaic strings and their corresponding DC / DC conversion circuits 200 and 200', wherein, in this embodiment, N is 6, K is also 6, and there are 12 photovoltaic strings in total. It can be seen that the connection method between the N photovoltaic strings (PV1~PV6), the switch device 400 and the DC / DC conversion circuit 200 in this embodiment is the same as Figure 6a Similarly, the connection between the K photovoltaic strings (PV7-PV12), the switch device 400' and the DC / DC conversion circuit 200' is also the same as Figure 6a Similarly, the main difference is that the second pole of one of the photovoltaic strings is connected across the switch device, for example, PV1- is connected across the switch device, that is, PV1- was originally connected to the second layer switch S2 of the switch device 400, but PV1- is connected to the second layer switch S6' of the switch device 400', and PV7- was originally connected to the second layer switch S6' of the switch device 400', but PV7- is connected to the second layer switch S2 of the switch device 400. It can be understood that this connection method is not only applicable to the case where N and K are equal, but also to the case where they are not equal, such as N=6, K=5. In addition, this connection method is not only applicable to the case where only one photovoltaic string is connected across the switch device, but also to more photovoltaic strings, for example, PV1- and PV2- can be connected across the switch device 400', or PV1-~PV3- can be connected across the switch device 400'. This application is not limited to this.

[0121] The structural design of the switch device 400 having different current carrying capacities adapted to the above-mentioned embodiment is further described below.

[0122] refer to Fig. 9 and Fig.10 , Fig. 9 A schematic diagram of the structure of a switch device 400 provided in an embodiment of the present application is shown in FIG. Fig.10The exploded diagram of a switch device 400 provided in an embodiment of the present application. The switch device 400 includes a rotating shaft 101 and multiple layers of switches P1 to Pn stacked along the extension direction O of the rotating shaft 101. Among them, P1 is the first layer of switches in the above embodiment of the present application, and P2, P3 and P4 are the second layer of switches in the above embodiment of the present application. Figure 6a In the embodiment shown, the positive poles of the six photovoltaic strings can all be connected to P1, and the negative poles of the six photovoltaic strings can be connected in pairs to P2, P3 and P4 respectively. In the embodiment of the present application, the current carrying capacity of P1 is greater than that of P2, P3 and P4. Therefore, along the extension direction O of the rotation axis 101, the layer height h1 of the first layer switch P1 is greater than the layer height h2 / h3 / h4 of the second layer switch P2 / P3 / P4. In some possible embodiments, the layer height h1 of the first layer switch P1 may also be equal to the layer height h2 / h3 / h4 of the second layer switch P2 / P3 / P4. Furthermore, except Fig. 9 In addition to the embodiments shown, in some other possible implementations, the flow capacity of P1 is greater than that of P2, P3 and P4, so that along the first direction, the radial length of the first layer switch P1 can be greater than or equal to the radial length of the second layer switch P2 / P3 / P4, wherein the first direction is perpendicular to the extension direction O of the rotation axis 101.

[0123] It is understandable that the switch device 400 of the embodiment of the present application may include more layers of switches P5-Pn in addition to the above-mentioned examples P1-P4, and these layers of switches may be designed in a similar structure to P1-P4, so as to realize that one switch device 400 is connected to more photovoltaic strings or / and multiple DC / DC conversion circuits 200. The following text of the present application mainly takes the first layer switch or the second layer switch of a certain layer as an example for explanation, and the structures of the other layers of switches are not repeated.

[0124] In order to reliably disconnect the switch in the switch device 400 when a reverse connection fault occurs in the photovoltaic string, the switch device 400 provided in the embodiment of the present application may further include a trip device 102. The trip device 102 may include a transmission mechanism controlled by the controller 600. When a reverse connection fault or a short circuit fault occurs in the photovoltaic string, or a short circuit fault occurs at the output end of the power conversion circuit, the controller 600 may send a disconnection instruction to the trip device 102, and the trip device 102 operates according to the disconnection instruction and drives the multi-layer switches P1~Pn to be disconnected.

[0125] In addition to the above-mentioned tripping device 102, the switch device 400 of the embodiment of the present application may also include a knob 103, which is fixed to the rotating shaft 101, so that the multi-layer switches P1 to Pn can be driven to disconnect by manually rotating the knob 103. That is, the switch device 400 of the embodiment of the present application can be automatically disconnected under the control of the controller 600, or manually disconnected under manual control.

[0126] Combine the following Fig.10 as well as Figure 11~Figure 13 The structure of each switch layer is described. Fig.11 A schematic diagram of the structure of a first layer switch P1 provided in an embodiment of the present application is shown in FIG. Fig.12 A schematic diagram of the structure of a second layer switch P2 provided in an embodiment of the present application is shown in FIG. Fig.13 A schematic diagram of the structure of another second-layer switch P3 provided in an embodiment of the present application. Each layer of the switch includes a housing and a moving contact and a stationary contact located in the housing, the moving contact rotates relative to the housing, and the stationary contact is fixed relative to the housing. Specifically, the moving contact can be relatively fixed to the rotating shaft 101, and the rotating shaft 101 is used to drive the moving contact to rotate to separate from or contact the stationary contact. When the multi-layer switches P1~Pn are connected, the moving contacts and stationary contacts in the multi-layer switches P1~Pn are in contact to achieve electrical connection. When the multi-layer switches P1~Pn are disconnected, the moving contacts and stationary contacts in the multi-layer switches P1~Pn are separated to disconnect the electrical connection.

[0127] Let's take the first layer switch P1 as an example. Fig.11 In the illustrated embodiment, the first layer switch P1 includes a housing 11, a first static contact 12, a second static contact 13 and a moving contact 14. The first static contact 12, the second static contact 13 and the moving contact 14 are arranged on the housing 11. The moving contact 14 can rotate relative to the housing. The first static contact 12 and the second static contact 13 are fixed relative to the housing 11. The moving contact 14 includes two ends 14A and 14B. The first static contact 12 and the second static contact 13 can be distributed on the rotation track of the moving contact 14. When the moving contact 14 is driven to rotate by the rotating shaft 101, one end 14A of the moving contact 14 can contact or separate from the first static contact 12, and the other end 14B of the moving contact 14 can contact or separate from the second static contact 13. For example, at present Fig.11 The state shown in the figure is that one end 14A of the moving contact 14 can contact the first static contact 12, and the other end 14B of the moving contact 14 can contact the second static contact 13. Among them, the first static contact 12 is used to be electrically connected to the photovoltaic string, and the second static contact 13 is used to be electrically connected to the power conversion circuit. Specifically, in combination with the above embodiment, the first static contact 12 of the first layer switch P1 is used to be connected to the first pole (for example, the positive pole) of the N photovoltaic strings, and the second static contact 13 of the first layer switch P1 is used to be connected to the input end of the DC / DC conversion circuit 200.

[0128] In some possible implementations, the first static contact 12 may include a connection portion 121 extending out of the housing 11, and the connection portion 121 is used to be electrically connected to the photovoltaic string. Fig.11As shown, the connection hole 1210 on the connection part 121 is used to achieve fastening and electrical connection with the connector connected to the photovoltaic string.

[0129] In some possible implementations, the switch device 400 can be connected to the power conversion circuit through a cable, or can be directly plugged into a circuit board with a power conversion circuit to achieve an upper board connection. In the case of an upper board connection, the second static contact 13 can include a pin portion 131 extending out of the housing 11, and the pin portion 131 is used to electrically connect to the circuit board to achieve connection with the power conversion circuit. Fig.11 In the embodiment, the pin portion 131 of the first layer switch P1 includes two pin portions, namely 131A and 131B. It can be understood that in some possible implementations, a wider pin portion 131 can also be set to adapt to the first layer switch P1, which has a high current capacity.

[0130] Furthermore, the first layer switch P1 may also include a first arc extinguishing chamber 15 and a second arc extinguishing chamber 16. The first arc extinguishing chamber 15 and the second arc extinguishing chamber 16 are arranged on both sides of the moving contact 14 along the rotation trajectory of the two ends of the moving contact 14, so that when the moving contact 14 contacts or separates from the first static contact 12 and the second static contact 13 respectively, the arc between the moving contact 14 and the first static contact 12 and the second static contact 13 is extinguished to ensure the safety of the switching device 400.

[0131] The structures of the second layer switch P2 and the second layer switch P3 are described in detail below. Figure 9~Figure 13 It can be seen that most structures of the second layer switch P2 and the second layer switch P3 are similar to the first layer switch P1, and the main difference is that Fig. 9 and Fig.10 Since the first layer switch P1 has a large current carrying capacity, the area of ​​its connection portion 121 is larger, and the number of its pin portions 131 is more or wider. The current carrying capacity of the second layer switch is smaller than that of the first layer switch, so the area of ​​its connection portion (221, 321, 421) is smaller, and the number of its pin portions is less or narrower.

[0132] like Fig.12In the illustrated embodiment, the second layer switch P2 includes a housing 21, a first static contact 22, a second static contact 23 and a moving contact 24. The first static contact 22, the second static contact 23 and the moving contact 24 are arranged on the housing 21. The moving contact 24 can rotate relative to the housing. The first static contact 22 and the second static contact 23 are fixed relative to the housing 21. The moving contact 24 includes two ends 24A and 24B. The first static contact 22 and the second static contact 23 can be distributed on the rotation track of the moving contact 24. When the moving contact 24 is driven to rotate by the rotating shaft 101, one end 24A of the moving contact 24 can contact or separate from the first static contact 22, and the other end 24B of the moving contact 24 can contact or separate from the second static contact 23. For example, at present Fig.12 The state shown in the figure is that one end 24A of the moving contact 24 can contact the first static contact 22, and the other end 24B of the moving contact 24 can contact the second static contact 23. Among them, the first static contact 22 is used to be electrically connected to the photovoltaic string, and the second static contact 23 is used to be electrically connected to the power conversion circuit. Specifically, in combination with the above embodiment, the first static contact 22 of the first layer switch P2 is used to connect to the second pole (for example, the negative pole) of some photovoltaic strings (for example, one photovoltaic string among N), and the second static contact 23 of the first layer switch P2 is used to connect to the input end of the DC / DC conversion circuit 200.

[0133] In some possible implementations, the first static contact 22 may include a connection portion 221 extending out of the housing 21, and the connection portion 221 is used to be electrically connected to the photovoltaic string. Fig.12 As shown, the connection hole 2210 on the connection part 221 is used to achieve fastening and electrical connection with the connector connected to the photovoltaic string.

[0134] In the case of upper board connection, the second static contact 13 may include a pin portion 231 extending out of the housing 21 , and the pin portion 231 is used to be electrically connected to the circuit board to achieve connection with the power conversion circuit.

[0135] Furthermore, the first layer switch P2 may also include a first arc extinguishing chamber 25 and a second arc extinguishing chamber 26, which are arranged on both sides of the moving contact 24 along the rotation trajectory of the two ends of the moving contact 24, so that when the moving contact 24 contacts or separates from the first static contact 22 and the second static contact 23 respectively, the arc between the moving contact 24 and the first static contact 22 and the second static contact 23 is extinguished, thereby ensuring the safety of the switching device 400.

[0136] like Fig.13In the illustrated embodiment, the second layer switch P3 includes a housing 31, a first static contact 32, a second static contact 33 and a moving contact 34. The first static contact 32, the second static contact 33 and the moving contact 34 are arranged on the housing 31. The moving contact 34 can rotate relative to the housing. The first static contact 32 and the second static contact 33 are fixed relative to the housing 31. The moving contact 34 includes two ends 34A and 34B. The first static contact 32 and the second static contact 33 can be distributed on the rotation track of the moving contact 34. When the moving contact 34 is driven to rotate by the rotating shaft 101, one end 34A of the moving contact 34 can contact or separate from the first static contact 32, and the other end 34B of the moving contact 34 can contact or separate from the second static contact 33. For example, at present Fig.13 The state shown in the figure is that one end 34A of the moving contact 34 can contact the first static contact 32, and the other end 34B of the moving contact 34 can contact the second static contact 33. Among them, the first static contact 32 is used to be electrically connected to the photovoltaic string, and the second static contact 33 is used to be electrically connected to the power conversion circuit. Specifically, in combination with the above embodiment, the first static contact 32 of the first layer switch P3 is used to connect to the second pole (for example, the negative pole) of some photovoltaic strings (for example, another photovoltaic string among the N), and the second static contact 33 of the first layer switch P3 is used to connect to the input end of the DC / DC conversion circuit 200.

[0137] In some possible implementations, the first static contact 32 may include a connection portion 321 extending out of the housing 31, and the connection portion 321 is used to be electrically connected to the photovoltaic string. Fig.13 As shown, the connection hole 3210 on the connection part 321 is used to achieve fastening and electrical connection with the connector connected to the photovoltaic string.

[0138] In the case of upper board connection, the second static contact 33 may include a pin portion 331 extending out of the housing 31 , and the pin portion 331 is used to be electrically connected to the circuit board to achieve connection with the power conversion circuit.

[0139] Furthermore, the first layer switch P3 may also include a first arc extinguishing chamber 35 and a second arc extinguishing chamber 36. The first arc extinguishing chamber 35 and the second arc extinguishing chamber 36 are arranged on both sides of the moving contact 34 along the rotation trajectory of the two ends of the moving contact 34, so that when the moving contact 34 contacts or separates from the first static contact 32 and the second static contact 33 respectively, the arc between the moving contact 34 and the first static contact 32 and the second static contact 33 is extinguished to ensure the safety of the switching device 400.

[0140] The above uses a first-layer switch P1 and two second-layer switches P2 and P3 as an example to illustrate the specific structure of the first-layer switch and the second-layer switch. It should be understood that in the switch device 400, the structures of other first-layer switches (such as P5) and other second-layer switches (such as P4) are similar to those of the first-layer switch P1 and the two second-layer switches P2 and P3, so this application will not repeat them.

[0141] Combine the following Fig. 9 and Fig.14 Further explain the structure of the connection and pins between the switches of each layer. Fig. 9 In the embodiment of the present application, the connection part 121 of the first layer switch P1 and the connection parts 221, 321, 421 of the second layer switches P2~P4 can be staggered, that is, the connection part 121 of the first layer switch P1 is arranged at one end of the side wall of the shell layer, and the connection parts 221, 321, 421 of the second layer switches P2~P4 are arranged at the other end of the side wall of each layer of the shell, so that the creepage distance between the connection parts connecting the positive pole and the connection parts connecting the negative pole can be increased to achieve better electrical isolation. Fig.14 For this application Fig. 9 Another perspective structural diagram of a switch device provided in the embodiment. Combined with the above, it can be seen that Fig.14 In the embodiment of the present invention, the first layer switch P1 has two pins 131A and 131B, and the second layer switches P2 to P4 each have one pin (231, 331, 431). That is, the number of pins of the first layer switch is greater than the number of pins of the second layer switch. Furthermore, the pins of the switches of each layer can be staggered to increase the creepage distance of the pins of each layer and improve the safety requirements. For example, in Fig.14 In the embodiment shown, the two pins 131A and 131B of the first layer switch P1 extend outward from the middle of the side wall of the housing 11, and the pins of the second layer switches P2 to P4 extend outward from the ends of the side walls of their respective housings, and the pins between two adjacent second layer switches are not at the same end. For example, the pin 231 of the second layer switch P2 is located at one end of the side wall of its housing 21, and the pin 331 of the second layer switch P3 is located at the other end of the side wall of its housing 31.

[0142] It should be noted that the above structure is mainly described by taking one first-layer switch P1 and three second-layer switches P2~P5 as an example. When there are more first-layer switches and second-layer switches, the arrangement can be arranged by at least two second-layer switches between each first-layer switch. For example, P1 and P5 are separated by second-layer switches P2~P4, and other first-layer switches are similar. The advantage of such an arrangement is that the positive and negative poles of the photovoltaic string can correspond to the positions of the first-layer switches and the second-layer switches, which is convenient for wiring and avoids cable entanglement.

[0143] In other embodiments, the plurality of first-layer switches and the plurality of second-layer switches may also be arranged in a centralized manner.

[0144] refer to Fig.15 and Fig.16 , Fig.15 A schematic diagram of the structure of another switch device 400 provided in an embodiment of the present application, Fig.16 For this application Fig.15 Another schematic diagram of the structure of another switch device provided in the embodiment. It can be understood that Fig.15 and Fig.16 The embodiment shown is similar to the above Figure 9~Figure 14 The principle and structure of the switch device 400 of the embodiment shown are generally similar, and the main difference is that Fig.15 and Fig.16 In the embodiment shown, a plurality of first-layer switches are stacked and arranged adjacent to each other along the rotation axis, and a plurality of second-layer switches are stacked and arranged adjacent to each other along the rotation axis. Fig.15 As shown, the switch device 400 includes a rotating shaft 101' and a plurality of switches P1'~Pn' stacked along the extending direction O' of the rotating shaft 101'. Among them, P1'~P3' are respectively the first layer switches in the above-mentioned embodiments of the present application, and P5'~Pn' are respectively the second layer switches in the above-mentioned embodiments of the present application. It can be seen that the plurality of first layer switches are stacked in sequence first, and then the plurality of second layer switches are stacked in sequence. For further reference Fig.16 The pin design of Fig.16 In the embodiment, the first layer switches P1'~P3' each have two pin parts, namely 131A' and 131B', 231A' and 231B', 331A' and 331B', and the second layer switches P5'~Pn' each have one pin part (431', 531'...). That is, the number of pin parts of the first layer switches is greater than the number of pin parts of the second layer switches. Furthermore, the pin parts of the second layer switches can be staggered to increase the creepage distance of the pin parts of each layer and improve the safety requirements. In this embodiment, by arranging multiple first layer switches and multiple second layer switches in a centralized manner, the risk of short circuit caused by the positive and negative poles being too close can be better avoided.

[0145] The power supply method of the controller 600 in the embodiment of the present application is further described below.

[0146] See also Fig.17 , which is a schematic diagram of another photovoltaic system provided in an embodiment of the present application.

[0147] The controller 600 provided in the embodiment of the present application requires a power supply, and therefore, may include a first power circuit 500. The first power circuit 500 provided in the embodiment of the present application adopts a competitive power supply method, that is, the first power circuit 500 is used to supply power to the controller 600 from the group with the highest voltage among the M groups of photovoltaic strings, and does not need to supply power from each group of photovoltaic strings.

[0148] Fig.17 A method for implementing competitive power extraction is provided, that is, a circuit for implementing a first power extraction circuit, the first power extraction circuit includes 2 (M+1) diodes and a first capacitor; wherein M is the number of second-layer switches in the switch device 400 or the number of groups of photovoltaic strings, for example, when N is 4 photovoltaic strings, according to the connection method of the embodiment of the present application and grouping in pairs, the number of first-layer switches is 1 and the number of second-layer switches is 2. Then the first power extraction circuit includes 6 diodes and a capacitor.

[0149] The first end of each layer of switches in the M+1 layers of switches is connected to the first end and the second end of the first capacitor respectively through a forward biased diode and a reverse biased diode; the first end of each layer of switches is connected to the corresponding photovoltaic string, and the second end of each layer of switches is connected to the input end of the DC / DC conversion circuit.

[0150] from Fig.17 It can be seen that the switch device includes three layers of switches S1-S3, and each layer of switches corresponds to two diodes, that is, the first end of the first layer switch S1 is connected to the two ends of the first capacitor C1 through the corresponding forward biased diode D2 and the reverse biased diode D1, the first end of the second layer switch S2 is connected to the two ends of the first capacitor C1 through the corresponding forward biased diode D4 and the reverse biased diode D3, and the first end of the third layer switch S3 is connected to the two ends of the first capacitor C1 through the corresponding forward biased diode D6 and the reverse biased diode D5. PV1+—PV4+ are connected together, that is, point A, the cathode of D1 is connected to point A, and similarly, the anode of D2 is connected to point A. PV1- and PV2- are connected together, that is, point B, the cathode of D3 is connected to point B, and similarly, the anode of D4 is connected to point B. PV3- and PV4- are connected together, that is, point C, the cathode of D5 is connected to point C, and similarly, the anode of D6 is connected to point C.

[0151] The specific working principle of competitive power supply is described below with examples in conjunction with the accompanying drawings.

[0152] For example, when the voltage of PV1 and PV2 connected in parallel is higher than the voltage of PV3 and PV4 connected in parallel, the voltage at point B is lower than the voltage at point C, and the current flows back to PV1 and PV2 through point B. Conversely, when the voltage of PV1 and PV2 connected in parallel is lower than the voltage of PV3 and PV4 connected in parallel, the voltage at point B is higher than the voltage at point C, and the current flows back to PV3 and PV4.

[0153] When PV1-PV4 are all reversed, the voltage of PV1 / PV2 connected in parallel is greater than the voltage of PV3 and PV4 connected in parallel, then the voltage at point B is higher than the voltage at point C, and the current flows out from PV1 and PV2, and vice versa from PV3 and PV4.

[0154] The following introduces a specific implementation method for determining whether a PV string is reversely connected.

[0155] See also Fig.18 , which is a schematic diagram of another photovoltaic system provided in an embodiment of the present application.

[0156] The photovoltaic system provided in this embodiment may further include: an input current detection circuit 700;

[0157] The input current detection circuit 700 is used to detect the current of each photovoltaic string in the N photovoltaic strings; it should be understood that each photovoltaic string can be connected in series with a current sensor to detect the current of each photovoltaic string. Since the directions of the currents of the photovoltaic strings are the same under normal circumstances, if there is reverse connection, the current direction of the reversed photovoltaic string will be opposite to the direction of other normal photovoltaic strings. Therefore, it is possible to judge whether the connection is reversed by the current direction. For example, the current is positive under normal circumstances, and when reversed, the detected current is negative, thereby judging the reverse connection.

[0158] The controller 600 is used to control the multiple layers of switches in the switch device 400 to disconnect when the current of any one of the N photovoltaic strings is reversed according to the current of each photovoltaic string. That is, the controller 600 sends a disconnection instruction to the trip device, and the trip device drives the three-layer switches S1-S3 to disconnect. As long as there is a reverse connection fault in all photovoltaic strings, it is necessary to disconnect all photovoltaic strings from the DC / DC conversion circuit 200.

[0159] The switch device 400 provided in the embodiment of the present application can not only be disconnected when a reverse connection fault occurs in the photovoltaic string to play a protective role, but can also be disconnected when a short circuit fault occurs in the photovoltaic string to play a protective role, which is described in detail below.

[0160] The photovoltaic system provided in this embodiment may include not only the input current detection circuit 700 , but also an input voltage detection circuit 800 .

[0161] The input voltage detection circuit 800 is used to detect the voltage between the first end of the first layer switch S1 and the first end of each of the two second layer switches (S2 and S3). Assuming there are M second layer switches, M voltages are obtained; that is, the voltage detected by the input voltage detection circuit 800 is the voltage of each group in the M photovoltaic strings. As long as the voltage of one photovoltaic string is low, there may be a short circuit fault in some photovoltaic strings. It should be understood that when a short circuit fault exists, the voltage of the photovoltaic string will drop and the current will rise. In order to accurately judge the short circuit fault, both voltage and current can be judged. Fig.18 In the embodiment, the input voltage detection circuit 800 needs to detect the voltage between point A where PV1+-PV4+ are connected together and point B where PV1- and PV2- are connected together. The input voltage detection circuit 800 also needs to detect the voltage between point A where PV1+-PV4+ are connected together and point C where PV3- and PV4- are connected together.

[0162] In a specific implementation, the controller 600 is used to control the M+1 layer switches to be disconnected when at least one of the M voltages is less than the first voltage threshold and the current of at least one of the N photovoltaic strings is greater than the first current threshold. That is, as long as there is a short circuit fault in the photovoltaic string, all switches in the switch device 400 are disconnected, thereby isolating the faulty photovoltaic string and protecting the subsequent circuit from the harm of the short circuit fault.

[0163] The above-described embodiment is for detecting a short-circuit fault at the input end of a DC / DC conversion circuit. The following describes a short-circuit fault at the output end of a DC / DC conversion circuit.

[0164] See also Fig.19 , which is a schematic diagram of another photovoltaic system provided in an embodiment of the present application.

[0165] The embodiments of the present application can not only detect whether a short circuit fault occurs at the input end of the DC / DC conversion circuit, but also detect whether a short circuit fault occurs at the output end of the DC / DC conversion circuit. When a short circuit fault occurs at the output end of the DC / DC conversion circuit, in order to avoid the expansion of the fault range and play a protective role, it is also necessary to control all layer switches in the switch device to be disconnected to play a role of fault isolation.

[0166] The photovoltaic system provided in this embodiment further includes: an output current detection circuit 901 and an output voltage detection circuit 902;

[0167] The output current detection circuit 901 is used to detect the current at the second end of the first layer switch S1 , that is, to detect the input current of the DC / DC conversion circuit 200 .

[0168] The output voltage detection circuit 902 is used to detect the output voltage of the DC / DC conversion circuit 200 .

[0169] In order to accurately determine whether a short circuit fault occurs at the output end of the DC / DC conversion circuit 200, dual judgments of voltage and current are also required. When both meet the corresponding judgment conditions, a short circuit fault is determined. That is, the controller 600 controls the multi-layer switches to be disconnected when the current at the second end of the first-layer switch S1 is greater than the second current threshold and the voltage at the output end of the DC / DC conversion circuit 200 is less than the second preset voltage. Since the first-layer switch S1 connects all photovoltaic strings, the output voltage detection circuit 902 only needs to detect the current flowing through the first-layer switch S1.

[0170] It should be understood that both the input current detection circuit and the output current detection circuit can be implemented by a current sensor. When there is reverse connection in the photovoltaic string, the current of the photovoltaic string is opposite to the current direction of the normal photovoltaic string. Therefore, it is possible to determine whether there is a reverse connection fault by detecting the direction of the current. For example, when the current of the normal photovoltaic string is positive, the current of the reverse-connected photovoltaic string is negative, that is, less than zero, then it is judged that the current is reversed, or it can be less than a preset threshold, then it is considered to be reversed and a reverse connection fault occurs. A current sensor can be set in each photovoltaic string to detect the current of the photovoltaic string. In addition, for example, if four photovoltaic strings are included, three of the photovoltaic strings can be provided with current sensors, and a current sensor is provided for the output current. Then the current of another photovoltaic string can be obtained by subtracting the sum of the currents of the three photovoltaic strings from the output current, so that one less current sensor can be provided.

[0171] The photovoltaic system provided in the embodiment of the present application can, in order to more comprehensively protect the safe and reliable operation of the photovoltaic system, not only disconnect all layer switches in the switch device 400 when a reverse connection fault occurs in the photovoltaic string, but also disconnect all layer switches in the switch device 400 when a short circuit fault occurs in the photovoltaic string, and can also disconnect all layer switches in the switch device 400 when a short circuit fault occurs at the output end of the DC / DC conversion circuit 200, so as to prevent the short circuit fault at the output end of the DC / DC conversion circuit 200 from causing damage to the photovoltaic string.

[0172] The above embodiment introduces the situation of taking power from the photovoltaic string to power the controller. In order to ensure that the controller can continue to work when the photovoltaic string is disconnected or the photovoltaic string has no power output, the embodiment of the present application also includes another power taking method, which can be used as the main power supply method of the controller. The following is a detailed introduction with reference to the accompanying drawings.

[0173] See also Fig. 20 , which is a schematic diagram of another photovoltaic system provided in an embodiment of the present application.

[0174] Since any hardware may fail during operation, in order to ensure that the photovoltaic system operates safely and reliably, two controllers may be set in the photovoltaic system to form a backup, that is, to achieve redundant control. When one of the controllers fails, it does not affect the normal control operation. That is, in the photovoltaic system provided in this embodiment, the controller 600 includes: a main controller 600a and a backup controller 600b;

[0175] The main controller 600a and the backup controller 600b are both used to control the M+1 layer switches to be disconnected when there is a reverse connection fault in N photovoltaic strings. That is, in the embodiment of the present application, the main controller 600a and the backup controller 600b work simultaneously, and the main controller 600a and the backup controller 600b can simultaneously receive the detection signals sent by the input voltage detection circuit 800, the input current detection circuit 700, the output current detection circuit 901 and the output voltage detection circuit 902, that is, the two controllers can simultaneously receive the input voltage, input current, output current and output voltage, and can use the received signals to determine whether it is necessary to control all the layer switches in the switch device 400 to be disconnected. In this way, it can be ensured that when one of the controllers fails and cannot accurately send a disconnection instruction to the switch device, the other normal controller can accurately and reliably control all the layer switches to be disconnected.

[0176] In addition, in order to ensure the reliability of power supply, the embodiment of the present application provides two auxiliary sources, namely, including: a main auxiliary source 903 and a secondary auxiliary source 904;

[0177] The main auxiliary source 903 and the secondary auxiliary source 904 are both used to supply power to the main controller 600a and the standby controller 600b;

[0178] The main auxiliary source 903 is connected to the output end of the DC / DC conversion circuit 200 ; that is, the power supply of the main auxiliary source 903 comes from the output end of the DC / DC conversion circuit 200 .

[0179] The auxiliary source 904 is connected to a first end of the switch device 400 , that is, the power source of the auxiliary source 904 comes from a photovoltaic string.

[0180] Since the photovoltaic system provided in the embodiment of the present application includes two auxiliary sources, when one of the auxiliary sources fails, the other normal auxiliary source can supply power to the controller as usual to ensure the normal operation of the controller.

[0181] The second power supply circuit that provides power source for the main auxiliary power source 903 is introduced below.

[0182] The second power supply circuit includes: a first diode D7, a second diode D8, a third diode D9, a fourth diode D10 and a second capacitor C2;

[0183] The cathode and anode of the first diode D7 are respectively connected to the positive output end of the DC / DC conversion circuit 200 and the first end of the second capacitor C2; the anode and cathode of the second diode D8 are respectively connected to the positive output end of the DC / DC conversion circuit 200 and the second end of the second capacitor C2;

[0184] The anode and cathode of the third diode D9 are respectively connected to the first end of the second capacitor C2 and the negative output end of the DC / DC conversion circuit 200, and the anode and cathode of the fourth diode D10 are respectively connected to the negative output end of the DC / DC conversion circuit 200 and the second end of the second capacitor C2;

[0185] The main auxiliary source 903 is connected to the positive output end of the DC / DC conversion circuit 200 through the second power extraction circuit. Since the power supply of the main auxiliary source 903 comes from the output end of the DC / DC conversion circuit 200, and the photovoltaic system generally includes multiple DC / DC conversion circuits, and the output ends of the multiple DC / DC conversion circuits are connected in parallel, even if all layer switches in the switch device 400 are disconnected and all photovoltaic strings connected to the input end of the DC / DC conversion circuit 200 are isolated, the output end of the DC / DC conversion circuit 200 can also have electricity, that is, from other parallel DC / DC conversion circuits. In this way, the power supply of the main auxiliary source 903 can be guaranteed, thereby ensuring the power supply of the controller.

[0186] The specific implementation form of the DC / DC conversion circuit in each of the above photovoltaic systems is not limited in the embodiments of the present application, and can be, for example, a boost circuit with a bypass relay, i.e., a Boost circuit. When the bypass relay is closed, the Boost circuit can be bypassed, i.e., there is no need to boost the voltage, and the photovoltaic string is directly connected to the DC / AC conversion circuit of the subsequent stage through the bypass relay.

[0187] Generally, in order to increase the output power of a power conversion device, a plurality of DC / DC conversion circuits are connected to the input end of a DC / AC conversion circuit.

[0188] See also Fig.21 , which is a schematic diagram of a photovoltaic system including multiple DC / DC conversion circuits provided in an embodiment of the present application.

[0189] The photovoltaic system provided in this embodiment includes: a plurality of switch devices and a plurality of DC / DC conversion circuits;

[0190] The multiple switch devices correspond to the multiple DC / DC conversion circuits one by one, that is, the input end of each DC / DC conversion circuit is connected to a corresponding switch device. The output ends of the multiple DC / DC conversion circuits are all connected to the input end of the DC / AC conversion circuit 300.

[0191] The following example takes the case where the input end of the DC / AC conversion circuit is connected to at least two DC / DC conversion circuits: the first DC / DC conversion circuit 200a and the second DC / DC conversion circuit 200b. The input ends of the first DC / DC conversion circuit 200a and the second DC / DC conversion circuit 200b are connected to the corresponding photovoltaic arrays, that is, the first DC / DC conversion circuit 200a corresponds to the photovoltaic array 100a, and the second DC / DC conversion circuit 200b corresponds to the photovoltaic array 100b. The photovoltaic array 100a and the photovoltaic array 100b both include multiple photovoltaic strings. For details, please refer to the introduction of the above embodiment. The photovoltaic strings in the photovoltaic array are not illustrated in detail in this embodiment. In this embodiment, a switch device 400a is connected between the input end of the photovoltaic array 100a and the first DC / DC conversion circuit 200a, and a switch device 400b is connected between the input end of the photovoltaic array 100b and the second DC / DC conversion circuit 200b. The functions of the switch device 400a and the switch device 400b are the same as those of the switch device in the photovoltaic system described in the above embodiment, and will not be repeated here.

[0192] For example, when a reverse connection fault occurs in the photovoltaic strings in the photovoltaic array 100a, all switches in the switch device 400a are disconnected, that is, the photovoltaic array 100a stops working, and there is no power supply to the input end of the first DC / DC conversion circuit 200a. However, since the photovoltaic strings in the photovoltaic array 100b are normal, the operation of the DC / AC conversion circuit 300 is not affected, and the DC / AC conversion circuit 300 can output electrical energy normally.

[0193] In addition, the photovoltaic system provided in the embodiment of the present application may include a combiner box, that is, a DC combiner box, in which multiple switch devices and multiple DC / DC conversion circuits are integrated.

[0194] The DC combiner box includes: multiple switch devices and multiple DC / DC conversion circuits; the multiple switch devices and the multiple DC / DC conversion circuits correspond one to one; the first end of each switch device is connected to N photovoltaic strings, and the second end of each switch device is connected to the input end of the DC / DC conversion circuit; each switch device includes a multi-layer switch, and each photovoltaic string in the N photovoltaic strings is connected to the input end of the corresponding power conversion circuit through the same layer of switches in the multi-layer switch; when there is a reverse connection fault in the N photovoltaic strings, the corresponding multi-layer switches are all disconnected.

[0195] The following is an introduction using two power conversion circuits as examples, wherein the power conversion circuit is introduced using a DC / DC conversion circuit as an example. The working principles and advantages of the above photovoltaic system embodiments are also applicable to the DC combiner box provided in this embodiment, and the same parts are not repeated here.

[0196] See also Fig. 22, which is a schematic diagram of a DC combiner box provided in an embodiment of the present application.

[0197] The first DC / DC conversion circuit 200 a , the second DC / DC conversion circuit 200 b , the switch device 400 a and the switch device 400 b are all integrated in the DC combiner box 1000 .

[0198] Since the DC junction box provided in the embodiment of the present application includes a switch device, wherein the switch device includes multiple layers of switches, the multiple layers of switches are linked, that is, they are closed or opened at the same time. The number of layers of switches depends on the number of photovoltaic strings. N photovoltaic strings are divided into M groups, and the switch device includes M+1 layers of switches. The first ends of the N photovoltaic strings are connected to the input end of the DC / DC conversion circuit through the first layer of switches in the M+1 layer of switches; the M groups of photovoltaic strings are respectively connected to the input end of the DC / DC conversion circuit through the M layer switches in the M+1 layer of switches; when there is a reverse connection fault in the N photovoltaic strings, the M+1 layer switches are all disconnected, that is, as long as a reverse connection fault occurs in one of the photovoltaic strings, all layer switches in the switch device are disconnected.

[0199] In the embodiments of the present application, it is not limited whether the first end of the photovoltaic string is a positive layer or a negative layer, that is, N photovoltaic strings can be connected to a common positive layer or a common negative layer. For the convenience of description, the following embodiments are introduced by taking the connection of N photovoltaic strings to a common positive layer as an example. When N photovoltaic strings are connected to a common positive layer, the positive layers of the N photovoltaic strings are connected together and connected to the positive input end of the DC / DC conversion circuit through a layer of switches. The negative layers of the N photovoltaic strings are grouped in pairs and connected to the negative input end of the DC / DC conversion circuit through corresponding layer switches. Since the positive layers of the N photovoltaic strings are connected together, the input current of the DC / DC conversion circuit can be increased. In addition, since the negative layers of the N photovoltaic strings are grouped in pairs, the number of layers of switches in the switching device is reduced to a certain extent, thereby reducing the complexity of the hardware structure and reducing costs.

[0200] The embodiments described above are all described by taking the example that the power conversion circuit includes a DC / DC conversion circuit and a DC / AC conversion circuit. The following describes the implementation of the power conversion circuit including only a DC / AC conversion circuit in conjunction with the accompanying drawings.

[0201] Based on a photovoltaic system provided in the above embodiment, an embodiment of the present application further provides a fault isolation method.

[0202] The fault isolation method provided in this embodiment is applied to the photovoltaic system introduced in any of the above embodiments, and the photovoltaic system includes: a switch device and a power conversion circuit; the first end of the switch device is connected to N photovoltaic strings, and the second end of the switch device is connected to the power conversion circuit; the switch device includes a rotating shaft and a multi-layer switch stacked along the extension direction of the rotating shaft, and the multi-layer switch includes a first-layer switch and at least two second-layer switches; the current carrying capacity of the first-layer switch is greater than the current carrying capacity of the second-layer switch. The input end of the power conversion circuit is connected to the switch device; the first-layer switch is simultaneously connected to the first poles of the N photovoltaic strings, and each second-layer switch is connected to the second poles of some of the N photovoltaic strings; wherein the first pole is a positive pole or a negative pole, and the second pole is another pole opposite to the first pole.

[0203] The method includes:

[0204] It is determined that there is a reverse connection fault in N photovoltaic strings, and all multi-layer switches are controlled to be disconnected.

[0205] Determine whether there is a reverse connection fault in N photovoltaic strings, including:

[0206] Obtaining the current of each photovoltaic string among the N photovoltaic strings;

[0207] According to the current of each photovoltaic string, it is determined that the current of any photovoltaic string among the N photovoltaic strings is reversed, and it is determined that a reverse connection fault exists in the N photovoltaic strings.

[0208] When there is reverse connection in the photovoltaic string, the current of the photovoltaic string is opposite to the current direction of the normal photovoltaic string. Therefore, it is possible to determine whether there is a reverse connection fault by detecting the direction of the current. For example, when the current of the normal photovoltaic string is positive, the current of the reverse-connected photovoltaic string is negative, that is, less than zero, then it is determined that the current is reversed, or it can be less than a preset threshold, then it is considered to be reversed and a reverse connection fault occurs. A current sensor can be set in each photovoltaic string to detect the current of the photovoltaic string. In addition, for example, if four photovoltaic strings are included, three of the photovoltaic strings can be provided with current sensors, and a current sensor is provided for the output current. Then the current of another photovoltaic string can be obtained by subtracting the sum of the currents of the three photovoltaic strings from the output current, so that one less current sensor can be provided.

[0209] It should be understood that in this application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0210] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A power conversion device, characterized in that: include: Switching devices, power conversion circuits and controllers; The power conversion circuit input terminal is connected to the switch device; The switch device comprises a rotating shaft and a multi-layer switch stacked along the extending direction of the rotating shaft, wherein the multi-layer switch comprises a first layer switch and at least two second layer switches; the number of the first layer switches is less than the number of the second layer switches, and the current carrying capacity of the first layer switches is greater than the current carrying capacity of the second layer switches; the first layer switches are used to be connected to the first poles of N photovoltaic strings at the same time, and each of the second layer switches is used to be connected to the second poles of some photovoltaic strings in the N photovoltaic strings; wherein the first pole is a positive pole or a negative pole, the second pole is another pole opposite to the first pole, and N is a positive integer greater than or equal to 2; Along the extension direction of the rotation axis, the layer height of the first layer switches is greater than the layer height of any of the second layer switches; Any layer switch of the switch device comprises: a shell and a moving contact and at least one static contact arranged on the shell, the moving contact rotates relative to the shell; the at least one static contact comprises a first static contact and a second static contact, one end of the moving contact is used to contact or separate with the first static contact, and the other end of the moving contact is used to contact or separate with the second static contact; the first static contact is used to be electrically connected to the photovoltaic string, and the second static contact is used to be electrically connected to the power conversion circuit; the first static contact of any layer switch comprises a connecting portion extending from the shell, and the connecting portion is used to be electrically connected to the photovoltaic string; the area of ​​the connecting portion of the first layer switch is larger than the area of ​​the connecting portion of the second layer switch; The power conversion device further includes a circuit board, and the power conversion circuit is located on the circuit board; the second static contact of any layer of switches includes a pin portion extending from the housing, and the pin portion is used to be electrically connected to the circuit board to connect with the power conversion circuit; the number of the pin portions of the first layer of switches is greater than the number of the pin portions of the second layer of switches, or the width of the pin portions of the first layer of switches is greater than the width of the pin portions of the second layer of switches; The controller is used to: when there is a reverse connection fault in the photovoltaic string, or a short circuit fault in the photovoltaic string, or a short circuit fault occurs at the output end of the power conversion circuit, control the rotating shaft to drive the moving contact in the multi-layer switch to rotate to separate from the static contact, so that the multi-layer switches in the switch device are all disconnected in conjunction, so as to disconnect the positive and negative poles of the photovoltaic string from the power conversion circuit, and connect at most two or three photovoltaic strings out of the N photovoltaic strings in parallel.

2. The power conversion device according to claim 1, characterized in that: The radial length of the first layer of switches is greater than or equal to the radial length of the second layer of switches.

3. The power conversion device according to claim 1, characterized in that: The at least two second-layer switches have different current carrying capacities, and the at least two second-layer switches are connected to different numbers of second poles of photovoltaic strings.

4. The power conversion device according to claim 1, characterized in that: The N photovoltaic strings are divided into M groups of photovoltaic strings, and any group of photovoltaic strings includes one photovoltaic string, or two or three photovoltaic strings connected in parallel; Two second-layer switches of the at least two second-layer switches are used to be connected to the second poles of two groups of photovoltaic strings of the M groups of photovoltaic strings.

5. The power conversion device according to claim 4, characterized in that: The at least two second-layer switches include M second-layer switches; the M second-layer switches are used to be connected to the second poles of the M groups of photovoltaic strings in a one-to-one correspondence.

6. The power conversion device according to claim 4 or 5, characterized in that: When N is an even number, each photovoltaic string group includes two photovoltaic strings connected in parallel; When N is an odd number, each of the M-1 photovoltaic strings includes two photovoltaic strings connected in parallel, and the remaining photovoltaic string includes one photovoltaic string.

7. The power conversion device according to claim 1, characterized in that: The switch device also includes a trip device; The controller is used to send a disconnection instruction to the tripping device when there is a reverse connection fault in the photovoltaic string, or a short circuit fault in the photovoltaic string, or a short circuit fault occurs at the output end of the power conversion circuit. The tripping device operates according to the disconnection instruction and drives all the multi-layer switches to disconnect.

8. The power conversion device according to claim 1, characterized in that: The multi-layer switch includes a plurality of first-layer switches, and each of the first-layer switches is spaced apart by at least two second-layer switches.

9. The power conversion device according to claim 1, characterized in that: The multi-layer switch includes a plurality of first-layer switches, the plurality of first-layer switches are stacked and adjacent to each other along the rotation axis, and the at least two second-layer switches are stacked and adjacent to each other along the rotation axis.

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