Power conversion device

Abstract

The invention discloses power conversion equipment. The power conversion equipment comprises a switching device, a power conversion circuit and a controller, the switch device comprises multiple layers of switches which are stacked in the extending direction of the rotating shaft, the multiple layers of switches comprise first layer switches and second layer switches, and the number of the first layer switches is smaller than that of the second layer switches; the through-current capability of the first-layer switch is greater than that of the second-layer switch; the first-layer switch is used for being connected with the first poles of the N photovoltaic strings at the same time, and each second-layer switch is used for being connected with the second poles of part of the N photovoltaic strings; when faults exist in the N photovoltaic group strings, the multiple layers of switches are all switched off in a linkage mode, and at most two or three photovoltaic group strings in the N photovoltaic group strings are connected in parallel. Therefore, different numbers of connected photovoltaic strings are adapted, the number of switch layers is saved, and safety is ensured.

Description

[0001] This application is a divisional application. The application number of the original application is 202411269170.X, and the original application date is September 11, 2024. The entire content of the original application is incorporated herein by reference. Technical Field

[0002] This application relates to the technical field of photovoltaic power generation, and particularly to a power conversion device. Background Art

[0003] Currently, photovoltaic systems mainly include a single-stage power conversion mode and a two-stage power conversion mode. Among them, the single-stage power conversion mode means that the direct current of the photovoltaic array is directly converted into alternating current through a direct current / alternating current (DC / AC) circuit, while the two-stage power conversion mode means that the direct current of the photovoltaic array first undergoes a first-stage direct current / direct current (DC / DC) conversion through a DC / DC conversion circuit, and then undergoes a second-stage DC / AC conversion through a second-stage DC / AC conversion circuit to finally be converted into alternating current. 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.

[0004] Generally, the capacity of a single photovoltaic string is limited. To increase the capacity, multiple photovoltaic strings are connected in parallel to 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 reversely, the current of other photovoltaic strings will flow back into the reversely connected photovoltaic string. Since the current that the anti-parallel diodes in the photovoltaic panels of the photovoltaic string can withstand is limited, when the current of multiple photovoltaic strings flows back into one photovoltaic string, it will cause damage to the photovoltaic panels in the photovoltaic string.

[0005] In the prior art, usually a circuit breaker or a fuse is connected in series to each photovoltaic string so that when a certain photovoltaic string fails and is back-fed by other photovoltaic strings, the connection between this photovoltaic string and other photovoltaic strings can be disconnected. However, the number of circuit breakers or fuses in this solution is too large. As the number of currently connected photovoltaic strings increases, it is easy to cause the volume of the power conversion device to be too large and the cost to be too high. Summary of the Invention

[0006] This application provides a power conversion device that can timely isolate a fault when a photovoltaic string is reversely connected, ensure the safety of the photovoltaic string and complete isolation from the power circuit, and at the same time can save the number of switch layers in the switching device, reduce the volume and cost of the switching device.

[0007] 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.

[0008] In the above implementation solution, the switch includes a multi-layer switch. The multi-layer switch as a whole is a linked switch, that is, a multi-P (Pole) switch, and the multi-layer switch is disconnected or conducted simultaneously. When there is a reverse connection fault in N photovoltaic strings, the multi-layer switch is disconnected, that is, as long as there is a reverse connection fault in one of the photovoltaic strings, all pole switches in the switch device are disconnected. Among them, in the multi-layer switch of the embodiment of the present application, a first-layer switch and a second-layer switch with different current-carrying capacities are set. In this way, layer switches with different current-carrying capacities can be adapted to the access of different numbers of photovoltaic strings, so that the grouping and connection methods 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 N photovoltaic strings can share a first-layer switch together. It is equivalent to the first poles of N photovoltaic strings being integrally converged to a first-layer switch. When the number of accessed photovoltaic strings is increasing, the first-layer switch with a large current-carrying capacity can greatly reduce the number of layer switches required for the convergence of N photovoltaic strings, and there is no need to use multiple layer switches with a small current-carrying capacity for current sharing. In addition, N photovoltaic strings can be grouped according to the specifications of the photovoltaic strings or circuit design. 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 solution, it is not restricted that the second poles of all the photovoltaic strings in N photovoltaic strings are all connected to the second-layer switch of a switch device. For example, other groups in N photovoltaic strings can also implement turn-off control through other switch devices. However, no matter what connection relationship is adopted, when the multi-layer switch of the switch device is controlled to be disconnected in a linked manner, at most two or three photovoltaic strings in N photovoltaic strings are connected in parallel. In this way, when a reverse connection or short-circuit fault occurs in the photovoltaic string, at most only one or two photovoltaic strings will perform reverse injection on the faulty string, which will not affect the safety of the photovoltaic string. That is to say, the above implementation solution of the present application enhances the current-carrying capacity of the first-layer switch to enable more photovoltaic modules with a larger number or a larger output current to be commonly connected to a first-layer switch, thereby reducing the number of first-layer switches. Also, by connecting the second poles of N photovoltaic strings to different second-layer switches, flexible grouping of N photovoltaic strings is realized, and at the same time, it can be ensured that the photovoltaic string is not affected by excessive reverse injection current. That is, the above implementation solution can not only greatly reduce the number of layers of the multi-layer switch in the switch device, thereby reducing the volume and cost of the switch device and the power conversion equipment, but also ensure the safety of the photovoltaic string and the power circuit, and can also simplify the control and circuit connection.

[0009] In a possible implementation manner, along the extension direction of the rotation axis, the floor height of the first-layer switch is greater than or equal to the floor height of the second-layer switch.

[0010] In a possible implementation, the radial length of the first-layer switch is greater than or equal to the radial length of the second-layer switch, where the direction of the radial length is perpendicular to the extension direction of the rotation axis.

[0011] In the above two implementation solutions, since the current-carrying capacity of the first-layer switch is greater than that of the second-layer switch, the devices inside the layer switch of the first-layer switch also need to be adapted to the large current-carrying capacity. Therefore, the height of the first-layer switch can be greater than or equal to the 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 increase the volume of the first-layer switch to some extent, compared with using multiple layer switches with small current-carrying capacities to connect the first poles of N photovoltaic strings, since the number of layer switches is reduced, the overall volume of the switch device can still be greatly reduced.

[0012] In a possible implementation, the current-carrying capacities of at least two second-layer switches are the same, or the current-carrying capacities of at least two second-layer switches are different. Among them, when the current-carrying capacities of at least two second-layer switches are different, different numbers of second poles of photovoltaic strings can be adapted for access.

[0013] In the above implementation solution, the second-layer switches can all adopt unified layer switches with the same current-carrying capacity, or different layer switches with different current-carrying capacities can be adopted according to the grouping situation to adapt to the current-carrying capacities of different groups.

[0014] In a possible implementation, the 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. Among them, two of the at least two second-layer switches are connected to the second poles of two groups of the M groups of photovoltaic strings. That is, among all the second-layer switches, at least two second-layer switches are connected to the second poles of two groups of the M groups of photovoltaic strings in a one-to-one correspondence. For example, group A of photovoltaic strings is correspondingly connected to one second-layer switch, and group B of photovoltaic strings is correspondingly connected to another second-layer switch. If there are more groups of photovoltaic strings, they can be connected through more second-layer switches of this switch device, or through other switch devices, or other methods can also be used to achieve this.

[0015] In a possible implementation, 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 multiple second-layer switches of this switch device.

[0016] In the above two implementation solutions, 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 parallel-connected photovoltaic strings. In this way, if a faulty photovoltaic string appears in a certain group, after disconnecting the multi-layer switch, there will be at most one or two backflow currents of photovoltaic strings, 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, and further reduce the number of layer switches and the volume of the entire switching device.

[0017] In a possible implementation manner, when N is an even number, each group of photovoltaic strings includes two parallel-connected photovoltaic strings; when N is an odd number, each of the M - 1 groups of photovoltaic strings includes two parallel-connected photovoltaic strings, and the remaining group of photovoltaic strings includes one photovoltaic string.

[0018] In the above implementation solution, the number of photovoltaic strings in each group is limited to two or less and preferably two. That is, when N is an even number, the N photovoltaic strings are grouped in pairs; when N is an odd number, the other N - 1 photovoltaic strings are grouped in pairs, and the remaining one photovoltaic string forms a group by itself. In this way, when a fault occurs in the photovoltaic string, after the switching device is disconnected, the faulty string bears at most one backflow current, which further ensures the safety of the photovoltaic string. At the same time, it can minimize the number of groups of photovoltaic strings at this safety level, and thus minimize the number of second-layer switches and reduce the volume of the switching device.

[0019] In a possible implementation manner, the N photovoltaic strings can be connected with a common positive electrode or a common negative electrode. For example, when the N photovoltaic strings are connected with a common positive electrode, the positive electrodes of the N photovoltaic strings are connected together, and the positive electrodes 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 electrode of each group of photovoltaic strings 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 with a common negative electrode, the negative electrodes of the N photovoltaic strings are connected together, and the negative electrodes 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 electrode of each group of photovoltaic strings is connected to the input end of the power conversion circuit through a second-layer switch in the multi-layer switch.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] In a possible implementation, the first stationary contact of any layer of switches includes a connecting portion protruding from the housing, and the connecting portion is used for electrically connecting with 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.

[0026] In the above implementation, since the current-carrying capacity of the first layer of switches is greater than that of the second layer of switches, the connecting portion of the first stationary contact of the first layer of switches also needs to adapt to the large current-carrying capacity accordingly. Therefore, 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.

[0027] In a possible implementation, the power conversion device further includes a circuit board, and the power conversion circuit is located on the circuit board; the second stationary contact of any layer of switches includes a pin portion protruding from the housing, and the pin portion is used for electrically connecting with the circuit board to connect with the power conversion circuit.

[0028] In the above implementation, the switching 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 wiring. This can save the space occupied when connecting with cables, thereby saving the internal space of the power conversion device and improving the power density.

[0029] In a possible implementation, the number of pin portions of the first layer of switches is greater than the number of pin portions of the second layer of switches.

[0030] In a possible implementation, the width of the pin portion of the first layer of switches is greater than the width of the pin portion of the second layer of switches.

[0031] In the above two implementations, since the current-carrying capacity of the first layer of switches is greater than that of the second layer of switches, the pin portions of the first layer of switches also need to adapt to the large current-carrying capacity accordingly. Therefore, the number of pin portions of the first layer of switches is greater than the number of pin portions of the second layer of switches, or the width of the pin portion of the first layer of switches is greater than the width of the pin portion of the second layer of switches.

[0032] In a possible implementation, the multi-layer switches include a plurality of first-layer switches, and each of the first-layer switches is spaced apart by at least two second-layer switches.

[0033] In the above implementation, since the positive and negative poles of N photovoltaic strings are respectively connected through the first-layer switches and the second-layer switches, and the plurality of first-layer switches are spaced apart by at least two second-layer switches, that is, the first-layer switches and the plurality of second-layer switches are arranged alternately. This can facilitate the connection of the positive and negative poles of the photovoltaic strings to the first-layer switches and the second-layer switches, and avoid the entanglement of cables.

[0034] In a possible implementation, the multi-layer switches include a plurality of first-layer switches, and the plurality of first-layer switches are stacked along the rotation axis and adjacent to each other, and at least two second-layer switches are stacked along the rotation axis and adjacent to each other.

[0035] In the above implementation manner, since the first-layer switch and the second-layer switch are respectively used to connect the positive and negative poles of the photovoltaic string, by arranging multiple first-layer switches and multiple second-layer switches in a centralized manner respectively, the short-circuit risk caused by the too-close proximity of the positive and negative poles can be better avoided.

[0036] In a possible implementation manner, to determine that the photovoltaic string has a reverse connection fault, it can be determined by the current direction of the photovoltaic string. When the current direction of the photovoltaic string is reversed, it indicates that there is a reverse connection fault. That is, the photovoltaic system provided in this embodiment may further include: an input current detection circuit for detecting the current of each of the N photovoltaic strings; when the controller determines that the current of any one of the N photovoltaic strings is reversed based on the current of each photovoltaic string, it controls all the multi-layer switches to be disconnected.

[0037] In a possible implementation manner, it further includes: an input current detection circuit and an input voltage detection circuit; the input current detection circuit detects the current of each of 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 of the M second-layer switches to obtain M voltages; 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, the controller controls all the multi-layer switches to be disconnected. As long as the voltage of one group of photovoltaic strings is low, there may be a short-circuit fault in some photovoltaic strings. It should be understood that when there is a short-circuit fault, the voltage of the photovoltaic string will drop and the current will rise. To accurately determine the short-circuit fault, double judgment of voltage and current can be used. As long as there is a short-circuit fault in the photovoltaic string, all the 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.

[0038] In a possible implementation manner, 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.

[0039] 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 switching device to disconnect, so as to play a role in fault isolation. That is, the photovoltaic system provided in this embodiment further 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; and a controller for controlling all the multi - layer switches to disconnect 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.

[0040] In a possible implementation, since any hardware may fail during operation, in order to ensure the safe and reliable operation of the photovoltaic system, two controllers can be set in the photovoltaic system to form a backup, that is, to achieve redundant control. When one of the controllers has a problem, it does not affect the normal control operation. That is, for the photovoltaic system provided in this embodiment, the controller includes: a main controller and a standby controller; both the main controller and the standby controller are used to control all the multi - layer switches to disconnect when there is a reverse - connection fault in the N photovoltaic strings.

[0041] In a possible implementation, in order to ensure the reliability of power supply, the embodiment of the present application provides two auxiliary power sources to supply power to the controller. That is, the photovoltaic system provided in this embodiment further includes: a main auxiliary power source and a secondary auxiliary power source; both the main auxiliary power source and the secondary auxiliary power source are used to supply power to the main controller and the standby controller; the main auxiliary power source is connected to the output end of the DC / DC conversion circuit; the secondary auxiliary power source is connected to the first end of the switching device.

[0042] In a possible implementation, in order to reliably supply power to the controller in any case, the photovoltaic system provided in the embodiment of the present application adopts a competitive power - taking method, that is, it further includes: a first power - taking circuit for taking power from the group of photovoltaic strings with the highest voltage among the M groups of photovoltaic strings to supply power to the secondary auxiliary power source.

[0043] In a possible implementation, the first power - taking circuit includes: 2(M + 1) diodes and a first capacitor; each of the M + 1 layer switches corresponds to two of the 2(M + 1) diodes; the first end of each of the M + 1 layer switches is connected to the first end and the second end of the first capacitor through a forward - biased diode and a reverse - biased diode respectively; the first end of each of the M + 1 layer switches is connected to the corresponding photovoltaic string, and the second end of each of the M + 1 layer switches is connected to the input end of the DC / DC conversion circuit.

[0044] In a possible implementation, the photovoltaic system provided by the embodiments of the present application further includes a second power-taking circuit for supplying power to the main auxiliary source; the second power-taking 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 terminal of the DC / DC conversion circuit and the first terminal of the second capacitor; the anode and cathode of the second diode are respectively connected to the positive output terminal of the DC / DC conversion circuit and the second terminal of the second capacitor; the anode and cathode of the third diode are respectively connected to the first terminal of the second capacitor and the negative output terminal of the DC / DC conversion circuit, and the anode and cathode of the fourth diode are respectively connected to the negative output terminal of the DC / DC conversion circuit and the second terminal of the second capacitor; the main auxiliary source is connected to the positive output terminal of the DC / DC conversion circuit. Since the power source of the main auxiliary source comes from the output terminal of the DC / DC conversion circuit, and generally a photovoltaic system includes multiple DC / DC conversion circuits, and the output terminals of the multiple DC / DC conversion circuits are connected in parallel, therefore, even if all the layer switches in the switching device are disconnected, isolating all the photovoltaic strings connected to the input terminal of the DC / DC conversion circuit, there is still power at the output terminal of the DC / DC conversion circuit, that is, from other parallel DC / DC conversion circuits. This can ensure the power supply of the main auxiliary source, and thus ensure the power supply of the controller.

[0045] In a possible implementation, it includes: multiple switching devices and multiple DC / DC conversion circuits; the multiple switching devices and the multiple DC / DC conversion circuits correspond one by one.

[0046] In a possible implementation, the power conversion circuit includes: a DC / AC conversion circuit.

[0047] Based on a power conversion device provided by the above embodiments, the embodiments of the present application further provide a fault isolation method, which is applied to the above power conversion device and includes: obtaining the current of each photovoltaic string among N photovoltaic strings; judging that the current of any one of the N photovoltaic strings is reversed according to the current of each photovoltaic string, and judging that there is a reverse connection fault among the N photovoltaic strings; when there is a reverse connection fault among the N photovoltaic strings, controlling all the layer switches in the switching device to be disconnected in a linkage manner to disconnect the connection between the positive and negative poles of the photovoltaic string and the power conversion circuit. Description of the Drawings

[0048] Figure 1a It is a schematic diagram of a photovoltaic system provided by the embodiments of the present application;

[0049] Figure 1b It is a schematic diagram of another photovoltaic system provided by the embodiments of the present application;

[0050] Figure 2 It is a schematic diagram of another photovoltaic system provided by the embodiments of the present application;

[0051] Figure 3 It is a schematic diagram of multiple photovoltaic strings connected in parallel to the input end of a DC / DC conversion circuit;

[0052] Figure 4 It is a schematic diagram of a photovoltaic system with a switching device provided by an embodiment of the present application;

[0053] Figure 5 It is a schematic diagram of the connection relationship between a switching device and a photovoltaic string provided by an embodiment of the present application;

[0054] Figure 6a It is another schematic diagram of the connection relationship between a switching device and a photovoltaic string provided by an embodiment of the present application;

[0055] Figure 6b It is another schematic diagram of the connection relationship between a switching device and a photovoltaic string provided by an embodiment of the present application;

[0056] Figure 6c It is another schematic diagram of the connection relationship between a switching device and a photovoltaic string provided by an embodiment of the present application;

[0057] Figure 7 It is another schematic diagram of the connection relationship between a switching device and a photovoltaic string provided by an embodiment of the present application;

[0058] Figure 8a It is a schematic diagram of the connection relationship between multiple switching devices and a photovoltaic string provided by an embodiment of the present application;

[0059] Figure 8b It is another schematic diagram of the connection relationship between multiple switching devices and a photovoltaic string provided by an embodiment of the present application;

[0060] Figure 9 It is a schematic diagram of the structure of a switching device provided by an embodiment of the present application;

[0061] Figure 10 It is an exploded view of a switching device provided by an embodiment of the present application;

[0062] Figure 11 It is a schematic diagram of the structure of a first-layer switch provided by an embodiment of the present application;

[0063] Figure 12 It is a schematic diagram of the structure of a second-layer switch provided by an embodiment of the present application;

[0064] Figure 13 It is another schematic diagram of the structure of a second-layer switch provided by an embodiment of the present application;

[0065] Figure 14 For the present application Figure 9Another perspective structural schematic diagram of a switching device provided by the embodiment;

[0066] Figure 15 Structural schematic diagram of another switching device provided by the embodiment of the present application;

[0067] Figure 16 For the present application Figure 15 Another perspective structural schematic diagram of a switching device provided by the embodiment;

[0068] Figure 17 Schematic diagram of another photovoltaic system provided by the embodiment of the present application;

[0069] Figure 18 Schematic diagram of yet another photovoltaic system provided by the embodiment of the present application;

[0070] Figure 19 Schematic diagram of still another photovoltaic system provided by the embodiment of the present application;

[0071] Figure 20 Schematic diagram of another photovoltaic system provided by the embodiment of the present application;

[0072] Figure 21 Schematic diagram of a photovoltaic system including multiple DC / DC conversion circuits provided by the present application;

[0073] Figure 22 Schematic diagram of a DC busbar box provided by the present application. Detailed implementation manners

[0074] In the following description, terms such as "first" and "second" are used only for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "a plurality" is two or more.

[0075] In addition, in the present application, orientation terms such as "upper" and "lower" may include but are not limited to being defined relative to the schematic placement orientation of components in the drawings. It should be understood that these directional terms may be relative concepts, and they are used for relative description and clarification, and they may change accordingly with the change of the orientation of the components placed in the drawings.

[0076] In this application, unless otherwise clearly specified or limited, the term "connection" shall be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral one; it can be directly connected or indirectly connected through an intermediate medium. In addition, the term "coupling" can be a way of realizing electrical connection for signal transmission. "Coupling" can be a direct electrical connection or an indirect electrical connection through an intermediate medium.

[0077] Embodiments of this application relate to a photovoltaic system, which can include two-stage power conversion or single-stage power conversion. First, the photovoltaic system including two-stage power conversion circuit will be introduced below. To enable those skilled in the art to better understand the technical solutions provided by the embodiments of this application, the photovoltaic system provided by the embodiments of this application will be introduced below with reference to the drawings.

[0078] See Figure 1a , which is a schematic diagram of a photovoltaic system provided by an embodiment of this application.

[0079] The photovoltaic system provided by the embodiments of this application includes a DC / DC conversion circuit 200 and a DC / AC conversion circuit 300. 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, where the photovoltaic array 100 includes a plurality of photovoltaic strings. Figure 1a Four photovoltaic strings are taken as an example for introduction, namely photovoltaic string PV1 to photovoltaic string PV4. Photovoltaic strings PV1 to PV4 can be connected in parallel at 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.

[0080] Among them, the DC / DC conversion circuit 200 is used to complete the DC-DC conversion, and the DC / AC conversion circuit 300 completes the DC-AC conversion. The output end of the DC / AC conversion circuit 300 can be connected to a transformer, that is, connected to the power grid through the transformer.

[0081] In addition, Figure 1a The figure shown is only a schematic diagram of one DC / DC conversion circuit 200 connected to the DC / AC conversion circuit 300. Generally, in order to increase the output power of the DC / AC conversion circuit 300, a plurality of 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 a plurality of photovoltaic strings.

[0082] 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. Additionally, in the photovoltaic system provided by the embodiments of the present application, the power conversion circuit may also only include a DC / AC conversion circuit and not include a DC / DC conversion circuit. Refer to Figure 1b As shown, this figure is a schematic diagram of another photovoltaic system provided by the embodiments of the present application.

[0083] Compare Figure 1a and Figure 1b It can be seen that Figure 1b in 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, it can be Figure 1a the power conversion circuit shown includes a DC / DC conversion circuit 200 and a DC / AC conversion circuit 300, or it can be Figure 1b the power conversion circuit shown only includes a DC / AC conversion circuit 300. Hereinafter, the case where the power conversion circuit includes a DC / DC conversion circuit will be mainly introduced.

[0084] Refer to Figure 2 This figure is a schematic diagram of another photovoltaic system provided by the embodiments of the present application.

[0085] Figure 2 Taking the case where the output ends of two DC / DC conversion circuits are both connected to the DC / AC conversion circuit 300 as an example for introduction, 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. Among them, the first DC / DC conversion circuit 200a and the second DC / DC conversion circuit 200b can be integrated in the DC busbar box 1000, and this DC busbar box 1000 can have the function of maximum power point tracking.

[0086] Figure 2 Taking the input end of the first DC / DC conversion circuit 200a being connected to the photovoltaic strings PV1 and PV2 as an example, the input end of the second DC / DC conversion circuit 200b is connected to the photovoltaic strings PV3 and PV4.

[0087] 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 connected reversely, the current of other photovoltaic strings will flow back into the reversely connected photovoltaic string. Since the current that the anti-parallel diodes in the photovoltaic string can withstand is limited, when the currents of multiple photovoltaic strings flow back into one photovoltaic string, the batteries in this photovoltaic string will be damaged.

[0088] See Figure 3 , which is a schematic diagram of multiple photovoltaic strings connected in parallel to the input end of the DC / DC conversion circuit.

[0089] Continuing to take four photovoltaic strings as an example for introduction, Figure 3 equivalent the photovoltaic string to the form of a battery in it. Traditionally, the positive poles PV1+—PV4+ of the four photovoltaic strings are connected together to connect to the positive input end of the DC / DC conversion circuit 200, and the negative poles PV1-—PV4- of the four photovoltaic strings are connected together to connect to the negative input end 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 end of the DC / DC conversion circuit 200, while the positive pole of PV4 is connected to the negative input end of the DC / DC conversion circuit 200. Figure 3 The situation where one photovoltaic string PV4 is reversely connected is shown, Figure 3 It can be seen from it that the currents of PV1-PV3 are shown by dotted lines with arrows, and the current of PV4 is shown by a solid line with an arrow, that is, the currents of PV1-PV3 will flow back into PV4 and damage PV4 because the current is too large. On the other hand, Figure 3 fuses are added to each photovoltaic string in it, that is, the four photovoltaic strings are respectively connected in series with fuses F1-F4. The fuses will increase the loss of the circuit. On the other hand, the disconnection of the fuses requires twice the input current, and the reliability is relatively low and the cost is relatively high.

[0090] To solve the problems caused by the reverse connection of the above photovoltaic strings, an embodiment of the present application provides a power conversion device 10, which is applied to the above photovoltaic system and can specifically be an inverter. See Figure 4, this figure is a schematic diagram of a photovoltaic system with a switching device provided by an embodiment of the present application. Specifically, the power conversion device 10 in the embodiment of the present application includes a switching 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. N photovoltaic strings (for example, PV1 to PV4) are connected to the input end of the power conversion circuit through the switching device 400. When a fault occurs in the photovoltaic string, the controller 600 can control the switching device 400 to disconnect from the input end of the power conversion circuit to achieve fault isolation. Among them, the switching device 400 includes a rotating shaft and multiple layers of switches stacked along the extension direction of the rotating shaft. The multiple layers of switches in the embodiment of the present application can achieve simultaneous linkage actions (disconnection or closing) through the rotation of the rotating shaft. As long as one or more of the photovoltaic strings connected to the multiple layers of switches have reverse connection faults, all the switches of the multiple layers of switches will be driven to disconnect simultaneously through the drive of the rotating shaft.

[0091] Specifically, the multiple layers of switches in the embodiment of the present application include a first-layer switch and at least two second-layer switches, and the number of first-layer switches is less than the number of second-layer switches. The first-layer switch is used to connect to the first pole of the N photovoltaic strings simultaneously, and each second-layer switch is used to connect to the second pole of some of the N photovoltaic strings. Among them, the first pole is the positive pole or the negative pole, and the second pole is the other pole opposite to the first pole. For example, if the first pole is the positive pole, the second pole is the negative pole; if the first pole is the negative pole, the second pole is the positive pole. The controller 600 is used to: when there is a reverse connection fault in the N photovoltaic strings, or there is a short-circuit fault in the N photovoltaic strings, or there is a short-circuit fault at the output end of the power conversion circuit, control all the multiple layers of switches in the switching device 400 to disconnect simultaneously, so as to disconnect the connection between the positive and negative poles of the N photovoltaic strings and the power conversion circuit, and make at most two or three of the N photovoltaic strings in parallel.

[0092] Equivalently, the N photovoltaic strings can be grouped according to the specifications of the photovoltaic strings or circuit design. 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, the first-layer switches and the second-layer switches with different current-carrying capacities are arranged in the multiple layers of switches. In this way, the layer switches with different current-carrying capacities can be adapted to the access of different numbers of photovoltaic strings, so that the grouping and connection methods of the photovoltaic strings can be more flexible to adapt to more scenarios and product requirements.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] The following is an example of N photovoltaic strings, with every two photovoltaic strings being grouped together.

[0100] 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;

[0101] or,

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] In the previous implementation methods, the current-carrying capacity of each layer of switches in the multi-layer switch is the same. Therefore, under the requirement of continuously increasing the number of currently connected photovoltaic strings, the first-layer switch cannot access more photovoltaic modules. For example, when the current-carrying capacity of each layer of switches can only reach a maximum of connecting less than N photovoltaic modules, it is impossible to connect the positive poles of all N photovoltaic strings only through 1 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.

[0111] Therefore, in the embodiments of the present application, by increasing 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, it is possible to ensure the safety of the photovoltaic string while enabling only one first-layer switch to connect to a certain pole of all N photovoltaic strings, further saving the number of layer switches.

[0112] Figure 5 The connection relationship with N = 4 is exemplified, and further refer to Figure 6a and Figure 6b , Figure 6a FIG. Figure 6b is a schematic diagram of the connection relationship between another switch device provided by the embodiment of the present application and a photovoltaic string. Figure 6a and Figure 6b are respectively schematic diagrams of the connection relationship of a photovoltaic system when N = 6 and N = 5. Among them, the positive poles of N photovoltaic strings are all connected to the first-layer switch S1 at the same time. In the embodiment of Figure 6a , N photovoltaic strings are divided into three groups of photovoltaic strings, each group includes two parallel-connected photovoltaic strings, and the negative poles of each group of photovoltaic strings correspond to the second-layer switches S2 to S4. That is to say, in the embodiment shown in Figure 6a , 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. Similarly, in the embodiment shown in Figure 6b , N photovoltaic strings are divided into three groups of photovoltaic strings, two groups include two parallel-connected photovoltaic strings, and one group includes one photovoltaic string, and the negative poles of each group of photovoltaic strings correspond to the second-layer switches S2 to S4. That is to say, in the embodiment shown in Figure 6b , 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 to 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.

[0113] In the embodiments 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 the N strings is increasing, connecting the first poles through only one first-layer switch for busbar connection may exceed the current-carrying capacity of one first-layer switch. In this case, multiple first-layer switches can also be used for connection. Refer to Figure 6c , Figure 6c which is a schematic diagram of the connection relationship between another switching device and photovoltaic strings provided by the embodiments of the present application. In Figure 6c the illustrated embodiment, the first poles of N photovoltaic strings can be respectively connected to the DC / DC conversion circuit through two first-layer switches S1 and S2.

[0114] It should be understood that the above several embodiments are only examples. The embodiments of the present application are not limited to the above number of photovoltaic strings. In practical applications, it can also support the access of more photovoltaic strings. Of course, the embodiments of the present application can also support the access of fewer photovoltaic strings.

[0115] Figure 7 which is a schematic diagram of the connection relationship between another switching device 400 and photovoltaic strings provided by the embodiments of the present application. Figure 7 is a schematic diagram of the connection relationship of a photovoltaic system when N = 3. Among them, the positive poles of N photovoltaic strings are all connected to the first-layer switch S1 at the same time. In Figure 7 the illustrated embodiment, the N photovoltaic strings are divided into two groups of photovoltaic strings. One group includes two parallel-connected photovoltaic strings, and the other group includes one photovoltaic string. The second-layer switches S2 to S3 correspond to the negative poles of each group of photovoltaic strings. In Figure 7 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.

[0116] It should be noted that the access of fewer photovoltaic strings does not necessarily mean less current input, and thus does not necessarily mean that the current-carrying capacity of the corresponding connected layer switch is necessarily smaller. In fact, this is related to the power output capacity of the photovoltaic strings and the architecture of the entire photovoltaic system. Therefore, Figure 7 the current-carrying capacity of the first-layer switch S1 in the illustrated embodiment is not necessarily less than Figures 5 to 6b the current-carrying capacity of the first-layer switch in the illustrated embodiment. For example, when the output power of the photovoltaic strings reaches a larger level, the input current after the busbar connection of the first poles of 3 photovoltaic strings (such as PV1+ to PV3+) may be similar to the input current after the busbar connection of the first poles of 6 photovoltaic strings (PV1+ to PV6+). That is to say, Figure 7 the current-carrying capacity of the first-layer switch S1 in the illustrated embodiment may be the same as that ofFigure 6b The current-carrying capacity of the first-layer switch S1 in the illustrated embodiment is similar.

[0117] In the embodiment of the present application, the current-carrying capacities of multiple second-layer switches can be the same to simplify the design. For example, multiple second-layer switches can all adopt standardized layer switches with the same current-carrying capacity, which can support the current input of two parallel-connected photovoltaic strings. Even if some second-layer switches are only connected to one photovoltaic string, layer switches that support the current input of two parallel-connected photovoltaic strings can still be used. Of course, the current-carrying capacities of multiple second-layer switches can also be different, and second-layer switches with corresponding current-carrying capacities can be configured according to each grouping situation, which can make the product design more flexible. For example, for the second-layer switch connecting two parallel-connected photovoltaic modules, a layer switch that supports the current input of two parallel-connected photovoltaic strings is adopted, and for the second-layer switch connecting three parallel-connected photovoltaic modules, a layer switch that supports the current input of three parallel-connected photovoltaic strings is adopted.

[0118] As mentioned above, the embodiment of the present application does not limit that the second poles of all the photovoltaic strings in N photovoltaic strings are respectively connected to the second-layer switches of the same switching device. Therefore, it is also possible that the second poles of some of the N photovoltaic strings adopt other connection methods. For example, when there are multiple switching devices, the second poles of some strings can be connected to other switching devices.

[0119] Reference Figure 8a , Figure 8a is a schematic diagram of the connection relationship between multiple switching devices and photovoltaic strings provided by the embodiment of the present application. Taking a possible implementation manner when N = 5 as an example for illustration, but the connection method and the number of photovoltaic strings of the present application are not limited thereto. It can be seen that it is basically similar to the Figure 6b illustrated embodiment. 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 switching device 400, but is connected through the second-layer switch S4' of another switching device 400'. That is, the second-layer switches of other switching devices can be reused to achieve joint control. For example, in a scenario, the second-layer switch S4' in another switching 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 access two photovoltaic strings. Then, PV5- and PV12- can be commonly connected to this second-layer switch S4' of the switching device 400'. In this way, the number of second-layer switches of the switching device can be further reduced by reusing the layer switches of different switching devices.

[0120] It should be noted that when the second-layer switch is connected to the negative electrode, the second-layer switch S4' of the switch device 400' can be connected to the negative electrode 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 electrode of another DC / DC conversion circuit. Since multiple DC / DC conversion circuits generally share the same negative electrode, both of these connection methods are acceptable.

[0121] Further refer to Figure 8b , Figure 8b FIG. is a schematic diagram showing another connection relationship between multiple switch devices and a photovoltaic string provided by an embodiment of the present application. In this embodiment, the power converter has two switch devices 400 and 400'. The switch devices 400 and 400' are connected between N+M photovoltaic strings and their corresponding DC / DC conversion circuits 200 and 200'. Among them, in this embodiment, N is 6, and K is also 6, for a total of 12 photovoltaic strings. It can be seen that the connection method between the N photovoltaic strings (PV1 to PV6), the switch device 400, and the DC / DC conversion circuit 200 in this embodiment is similar to Figure 6a , and the connection method between the K photovoltaic strings (PV7 to PV12), the switch device 400', and the DC / DC conversion circuit 200' is also similar to Figure 6a . 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, originally PV1- was connected to the second-layer switch S2 of the switch device 400, and now it is changed to connect PV1- to the second-layer switch S6' of the switch device 400'. Originally, PV7- was connected to the second-layer switch S6' of the switch device 400', and now it is changed to connect PV7- 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 is equal to K, but also applicable to the case where they are not equal, such as N = 6 and 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 applicable to more photovoltaic strings. For example, it can be that both PV1- and PV2- are cross-connected to the switch device 400', or it can be that PV1- to PV3- are all cross-connected to the switch device 400'. The present application does not make any limitations.

[0122] Next, the structural design of the switch device 400 with multi-layer switches having different current-carrying capacities adapted to the above embodiment will be further introduced.

[0123] Refer to Figure 9 and Figure 10 , Figure 9 FIG. is a schematic structural diagram of a switch device 400 provided by an embodiment of the present application. Figure 10An exploded view of a switch device 400 provided by 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 switch in the above embodiment of the present application, and P2, P3, and P4 are the second-layer switches in the above embodiment of the present application, respectively. In combination with Figure 6a the illustrated embodiment, the positive electrodes of 6 photovoltaic strings can all be connected to P1, and the negative electrodes of the 6 photovoltaic strings can be grouped in pairs and connected 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 rotating shaft 101, the layer height h1 of the first-layer switch P1 is greater than the layer heights h2 / h3 / h4 of the second-layer switches P2 / P3 / P4. In some possible embodiments, the layer height h1 of the first-layer switch P1 can also be equal to the layer heights h2 / h3 / h4 of the second-layer switches P2 / P3 / P4. Further, in addition to Figure 9 the illustrated embodiment, in some other possible implementation manners, the current-carrying capacity of P1 is greater than that of P2, P3, and P4. Therefore, along the first direction, the radial length of the first-layer switch P1 can be greater than or equal to the radial lengths of the second-layer switches P2 / P3 / P4, where the first direction is perpendicular to the extension direction O of the rotating shaft 101.

[0124] It can be understood that in addition to the above-exemplified P1 to P4, the switch device 400 of the embodiment of the present application can also include more layers of switches P5 to Pn, and the structures of these layers of switches can all be designed in a similar manner to P1 to P4 to realize that one switch device 400 is connected to more photovoltaic strings or / and multiple DC / DC conversion circuits 200. In the following text of the present application, the first-layer switch or the second-layer switch of a certain layer is mainly used as an example for description, and the structures of the remaining layer switches will not be elaborated.

[0125] In order to reliably disconnect the switches in the switch device 400 when a reverse connection fault occurs in the photovoltaic string, the switch device 400 provided by the embodiment of the present application can also include a tripping device 102. The tripping device 102 can include a transmission mechanism controlled by a controller 600. When a reverse connection fault or a short-circuit fault exists in the photovoltaic string, or a short-circuit fault occurs at the output end of the power conversion circuit, the controller 600 can send a disconnection instruction to the tripping device 102, and the tripping device 102 acts according to the disconnection instruction and drives the multiple layers of switches P1 to Pn to disconnect.

[0126] In addition to the above tripping device 102, the switch device 400 of the embodiment of the present application can also include a knob 103, and the knob 103 is fixed to the rotating shaft 101. In this way, by manually rotating the knob 103, the multiple layers of switches P1 to Pn can also be driven to disconnect. 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.

[0127] The following will describe the structure in each layer of switches in conjunction with Figure 10 and Figures 11 to 13 explain the structure in each layer of switches. Figure 11 FIG. is a schematic structural diagram of a first-layer switch P1 provided by an embodiment of the present application, Figure 12 FIG. is a schematic structural diagram of a second-layer switch P2 provided by an embodiment of the present application, Figure 13 FIG. is a schematic structural diagram of another second-layer switch P3 provided by an embodiment of the present application. Each layer of switch includes a housing and a moving contact and a static contact located inside the housing. The moving contact rotates relative to the housing, and the static contact is fixed relative to the housing. Specifically, the moving contact can be fixedly connected to a rotating shaft 101, and the rotating shaft 101 is used to drive the moving contact to rotate to separate or contact the static contact. When the multi-layer switches P1 to Pn are connected, the moving contacts and the static contacts in the multi-layer switches P1 to Pn are all in contact to achieve electrical connection. When the multi-layer switches P1 to Pn are disconnected, the moving contacts and the static contacts in the multi-layer switches P1 to Pn are all separated to disconnect the electrical connection.

[0128] First, take the first-layer switch P1 as an example for explanation. As Figure 11 shown in the 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 trajectory 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, currently Figure 11 what is shown is the state where 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 for electrical connection with a photovoltaic string, and the second static contact 13 is used for electrical connection with a power conversion circuit. Specifically, in combination with the above embodiment, the first static contact 12 of the first-layer switch P1 is used to connect to the first pole (such as the positive pole) of N photovoltaic strings, and the second static contact 13 of the first-layer switch P1 is used to connect to the input end of the DC / DC conversion circuit 200.

[0129] In some possible implementation manners, the first static contact 12 may include a connection portion 121 extending out of the housing 11, and the connection portion 121 is used for electrical connection with a photovoltaic string. Specifically, it can be as Figure 11As shown, fastening and electrical connection are achieved through the connection holes 1210 on the connection part 121 and the connector connecting the photovoltaic string.

[0130] In some possible implementation manners, when the switching device 400 is connected to the power conversion circuit, it can be connected by a cable or directly plugged onto a circuit board with a power conversion circuit to achieve board connection. In the case of board connection, the second static contact 13 may include a pin part 131 extending out of the housing 11, and the pin part 131 is used for electrical connection with the circuit board to achieve connection with the power conversion circuit. In Figure 11 the embodiment of, the pin part 131 of the first-layer switch P1 includes two, namely 131A and 131B. It can be understood that in some possible implementation manners, 1 wider pin part 131 can also be set to adapt to the first-layer switch P1 with such a high current-carrying capacity.

[0131] Furthermore, the first-layer switch P1 may further 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 at both ends of the moving contact 14, so as to extinguish the arc between the moving contact 14 and the first static contact 12 and the second static contact 13 when the moving contact 14 contacts or separates from the first static contact 12 and the second static contact 13 respectively, and ensure the safety of the switching device 400.

[0132] The structures of the second-layer switch P2 and the second-layer switch P3 will be specifically described below. Combining Figures 9 to 13 it can be seen that most of the structures of the second-layer switch P2 and the second-layer switch P3 are similar to those of the first-layer switch P1. The main difference is that, referring to Figure 9 and Figure 10 , since the first-layer switch P1 has a large current-carrying capacity, the area of its connection part 121 is larger, and the number of its pin parts 131 is more or wider. While the current-carrying capacity of the second-layer switch is smaller than that of the first-layer switch, so the area of its connection parts (221, 321, 421) is smaller, and the number of its pin parts is less or narrower.

[0133] As Figure 12In the illustrated embodiment, the second - layer switch P2 includes a housing 21, a first stationary contact 22, a second stationary contact 23, and a moving contact 24. The first stationary contact 22, the second stationary contact 23, and the moving contact 24 are disposed on the housing 21. The moving contact 24 is rotatable relative to the housing, and the first stationary contact 22 and the second stationary contact 23 are fixed relative to the housing 21. The moving contact 24 includes two ends 24A and 24B. The first stationary contact 22 and the second stationary contact 23 can be distributed on the rotation trajectory 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 stationary contact 22, and the other end 24B of the moving contact 24 can contact or separate from the second stationary contact 23. For example, currently Figure 12 what is shown is the state where one end 24A of the moving contact 24 can contact the first stationary contact 22, and the other end 24B of the moving contact 24 can contact the second stationary contact 23. Among them, the first stationary contact 22 is used for electrically connecting with a photovoltaic string, and the second stationary contact 23 is used for electrically connecting with a power conversion circuit. Specifically, in combination with the above - mentioned embodiment, the first stationary contact 22 of the first - layer switch P2 is used for connecting to the second pole (such as the negative pole) of a part of the N photovoltaic strings (for example, one group of the N photovoltaic strings), and the second stationary contact 23 of the first - layer switch P2 is used for connecting to the input end of the DC / DC conversion circuit 200.

[0134] In some possible implementation manners, the first stationary contact 22 may include a connecting portion 221 protruding from the housing 21, and the connecting portion 221 is used for electrically connecting with a photovoltaic string. Specifically, it can be as Figure 12 shown, and fastening and electrical connection are achieved through the connection hole 2210 on the connecting portion 221 and a connector connecting the photovoltaic string.

[0135] In the case of upper - board connection, the second stationary contact 13 may include a pin portion 231 protruding from the housing 21, and the pin portion 231 is used for electrically connecting with a circuit board to achieve connection with the power conversion circuit.

[0136] Furthermore, the first - layer switch P2 may further include a first arc - extinguishing chamber 25 and a second arc - extinguishing chamber 26. The first arc - extinguishing chamber 25 and the second arc - extinguishing chamber 26 are disposed on both sides of the moving contact 24 along the rotation trajectory of the two ends of the moving contact 24, so as to extinguish the arc between the moving contact 24 and the first stationary contact 22 and the second stationary contact 23 when the moving contact 24 contacts or separates from the first stationary contact 22 and the second stationary contact 23 respectively, and ensure the safety of the switching device 400.

[0137] As Figure 13In the illustrated embodiment, the second - layer switch P3 includes a housing 31, a first stationary contact 32, a second stationary contact 33, and a moving contact 34. The first stationary contact 32, the second stationary contact 33, and the moving contact 34 are disposed on the housing 31. The moving contact 34 can rotate relative to the housing, and the first stationary contact 32 and the second stationary contact 33 are fixed relative to the housing 31. The moving contact 34 includes two ends 34A and 34B. The first stationary contact 32 and the second stationary contact 33 can be distributed on the rotation trajectory 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 stationary contact 32, and the other end 34B of the moving contact 34 can contact or separate from the second stationary contact 33. For example, currently Figure 13 shown is the state where one end 34A of the moving contact 34 can contact the first stationary contact 32 and the other end 34B of the moving contact 34 can contact the second stationary contact 33. Among them, the first stationary contact 32 is used for electrically connecting with the photovoltaic string, and the second stationary contact 33 is used for electrically connecting with the power conversion circuit. Specifically, in combination with the above - mentioned embodiment, the first stationary contact 32 of the first - layer switch P3 is used to connect to the second pole (such as the negative pole) of some of the N photovoltaic strings (for example, another group of photovoltaic strings among the N), and the second stationary contact 33 of the first - layer switch P3 is used to connect to the input end of the DC / DC conversion circuit 200.

[0138] In some possible implementation manners, the first stationary contact 32 may include a connection portion 321 protruding from the housing 31, and the connection portion 321 is used for electrically connecting with the photovoltaic string. Specifically, as Figure 13 shown, fastening and electrical connection are achieved through the connection hole 3210 on the connection portion 321 and the connector connecting the photovoltaic string.

[0139] In the case of upper - board connection, the second stationary contact 33 may include a pin portion 331 protruding from the housing 31, and the pin portion 331 is used for electrically connecting with the circuit board to achieve connection with the power conversion circuit.

[0140] Furthermore, the first - layer switch P3 may further 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 disposed on both sides of the moving contact 34 along the rotation trajectory of the two ends of the moving contact 34, so as to extinguish the arcs between the moving contact 34 and the first stationary contact 32 and the second stationary contact 33 when the moving contact 34 contacts or separates from the first stationary contact 32 and the second stationary contact 33 respectively, and ensure the safety of the switching device 400.

[0141] The specific structures of the first-layer switch P1 and the second-layer switches P2 and P3 are described above by taking one first-layer switch P1 and two second-layer switches P2 and P3 as examples. 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. Therefore, they will not be elaborated in this application.

[0142] Next, in conjunction with Figure 9 and Figure 14 the structures of the connection parts and pin parts between the switches of each layer will be further described. Referring to Figure 9 , in the embodiment of this application, the connection part 121 of the first-layer switch P1 and the connection parts 221, 321, and 421 of the second-layer switches P2 to P4 can be staggeredly distributed. That is, the connection part 121 of the first-layer switch P1 is arranged at one end of the side wall of the housing of this layer, while the connection parts 221, 321, and 421 of the second-layer switches P2 to P4 are arranged at the other end of the side wall of each housing layer. In this way, the creepage distance between the connection parts for connecting the positive electrode and the connection parts for connecting the negative electrode can be increased, achieving better electrical isolation. Figure 14 This is Figure 9 another perspective structural schematic diagram of a switch device provided by the embodiment of this application. Combining the above, it can be seen that in the Figure 14 embodiment, the first-layer switch P1 has two pin parts 131A and 131B, and the second-layer switches P2 to P4 each have one pin part (231, 331, 431). That is, the number of pin parts of the first-layer switch is greater than that of the second-layer switch. Further, the pin parts of the switches of each layer can be staggeredly distributed to increase the creepage distance of the pin parts of each layer and improve the safety requirements. For example, in the Figure 14 shown embodiment, the two pin parts 131A and 131B of the first-layer switch P1 extend outwards from the middle of the side wall of the housing 11, and the pin parts of the second-layer switches P2 to P4 extend outwards from the ends of the side walls of their respective housings, and the pin parts between two adjacent second-layer switches are not at the same end. For example, the pin part 231 of the second-layer switch P2 is located at one end of the side wall of its housing 21, and the pin part 331 of the second-layer switch P3 is located at the other end of the side wall of its housing 31.

[0143] It should be noted that in the above structure, one first-layer switch P1 and three second-layer switches P2 to P5 are mainly used as examples for description. When there are more first-layer switches and second-layer switches, the arrangement method can be that at least two second-layer switches are arranged at intervals between each first-layer switch. For example, P1 and P5 are separated by the second-layer switches P2 to P4, and other first-layer switches are similar. The advantage of this 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 the entanglement of cables.

[0144] In some other embodiments, the multiple first-layer switches and the multiple second-layer switches may also be arranged in a respective centralized manner.

[0145] Reference Figure 15 and Figure 16 , Figure 15 FIG. 10 is a schematic structural diagram of another switch device 400 provided by an embodiment of the present application. Figure 16 This is Figure 15 another perspective structural diagram of another switch device provided by an embodiment of the present application. It can be understood that Figure 15 and Figure 16 The embodiments shown in FIGS. 10 and 11 are generally similar in principle and structure to the switch device 400 in the above-mentioned Figures 9 to 14 embodiments shown in FIGS. 8 and 9. The main difference is that, in the Figure 15 and Figure 16 embodiments shown in FIGS. 10 and 11, the multiple first-layer switches are stacked along the rotation axis and adjacent to each other, and the multiple second-layer switches are stacked along the rotation axis and adjacent to each other. As shown in Figure 15 FIG. 10, the switch device 400 includes a rotation axis 101' and multiple layers of switches P1' to Pn' stacked along the extension direction O' of the rotation axis 101'. Among them, P1' to P3' are respectively the first-layer switches in the above embodiments of the present application, and P5' to Pn' are respectively the second-layer switches in the above embodiments of the present application. It can be seen that the multiple first-layer switches are stacked in sequence first, and then the multiple second-layer switches are stacked in sequence. Further referring to Figure 16 the pin design in Figure 16 the embodiment shown in FIG. 11, in the

[0146] embodiment shown in FIG. 11, each of the first-layer switches P1' to P3' has two pin portions, namely 131A' and 131B', 231A' and 231B', 331A' and 331B', and each of the second-layer switches P5' to Pn' has one pin portion (431', 531'...). That is, the number of pin portions of the first-layer switches is greater than the number of pin portions of the second-layer switches. Further, the pin portions of the second-layer switches can be staggeredly distributed to increase the creepage distance of each layer of pin portions and improve the safety requirements. In this embodiment, by arranging the multiple first-layer switches and the multiple second-layer switches in a respective centralized manner, the short-circuit risk caused by the positive and negative poles being too close can be better avoided.

[0147] The power supply method of the controller 600 in the embodiment of the present application will be further described below. Figure 17 Referring to

[0148] The controller 600 provided in the embodiment of the present application needs power supply, so it may include a first power acquisition circuit 500. The first power acquisition circuit 500 provided in the embodiment of the present application adopts a competitive power acquisition method, that is, the first power acquisition circuit 500 is used to supply power to the controller 600 by taking power from the group with the highest voltage among M groups of photovoltaic strings, and it is not necessary to take power from each group of photovoltaic strings.

[0149] Figure 17 A realization method of competitive power acquisition is given, that is, a realization circuit of a first power acquisition circuit. The first power acquisition circuit includes 2(M + 1) diodes and a first capacitor; where M is the number of second-layer switches in the switching device 400 or the number of groups of photovoltaic strings. For example, when there are 4 photovoltaic strings, according to the connection method in the embodiment of the present application and grouped in pairs, the number of first-layer switches is 1, and the number of second-layer switches is 2. Then the first power acquisition circuit includes 6 diodes and a capacitor.

[0150] The first end of each layer of switches in M + 1 layers of 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 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.

[0151] From Figure 17 it can be seen that the switching 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 respectively connected to both ends of the first capacitor C1 through the corresponding forward-biased diode D2 and reverse-biased diode D1, the first end of the second-layer switch S2 is respectively connected to both ends of the first capacitor C1 through the corresponding forward-biased diode D4 and reverse-biased diode D3, and the first end of the third-layer switch S3 is respectively connected to both ends of the first capacitor C1 through the corresponding forward-biased diode D6 and 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.

[0152] The following takes the accompanying drawings as an example to introduce the specific working principle of competitive power supply.

[0153] 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 less than the voltage at point C, and the current flows back to PV1 and PV2 through point B. On the contrary, when the voltage of PV1 and PV2 connected in parallel is less 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.

[0154] When PV1 - PV4 are all reversely connected, 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.

[0155] The following introduces a specific implementation method for judging the reverse connection of photovoltaic strings.

[0156] See Figure 18 , this figure is a schematic diagram of another photovoltaic system provided by the embodiment of the present application.

[0157] The photovoltaic system provided by this embodiment may further include: an input current detection circuit 700;

[0158] The input current detection circuit 700 is used to detect the current of each photovoltaic string in N photovoltaic strings; it should be understood that a current sensor can be connected in series with each photovoltaic string to detect the current of each photovoltaic string. Since normally, the current directions of photovoltaic strings are the same, if there is a reverse connection, the current direction of the reversely connected photovoltaic string will be opposite to that of other normal photovoltaic strings. Therefore, it is possible to judge whether there is a reverse connection through the current direction. For example, when the current is positive normally, when there is a reverse connection, the detected current is negative, so as to judge the reverse connection.

[0159] The controller 600 is used to control all the multi - layer switches in the switch device 400 to disconnect when judging that 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 tripping device, and the tripping device acts to drive the three - layer switches S1 - S3 to disconnect. As long as there is a reverse connection fault in any one of all the photovoltaic strings, it is necessary to disconnect the connection between all the photovoltaic strings and the DC / DC conversion circuit 200.

[0160] The switch device 400 provided by the embodiment of the present application can not only disconnect when there is a reverse connection fault in the photovoltaic string to play a protective role, but also disconnect when there is a short - circuit fault in the photovoltaic string to play a protective role. The following will introduce it specifically.

[0161] The photovoltaic system provided by this embodiment, in addition to including the input current detection circuit 700, may further include an input voltage detection circuit 800.

[0162] The input voltage detection circuit 800 is used to detect the voltages between the first end of the first - layer switch S1 and the first ends of each two second - layer switches (S2 and S3). Assuming there are M second - layer switches, M voltages are obtained. That is, the voltages detected by the input voltage detection circuit 800 are the voltages of each group in M groups of photovoltaic strings. As long as the voltage of one group of photovoltaic strings is too low, there may be a short - circuit fault in some photovoltaic strings. It should be understood that when there is a short - circuit fault, the voltage of the photovoltaic string will drop and the current will rise. To accurately judge the short - circuit fault, double - judgment of voltage and current can be used. For example Figure 18 In [figure number not provided], 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.

[0163] A specific implementation is that the controller 600, when at least one of the M voltages is less than the first voltage threshold and at least one of the N photovoltaic strings has a current greater than the first current threshold, controls all M + 1 - layer switches to disconnect. That is, as long as there is a short - circuit fault in the photovoltaic string, all switches in the switching device 400 are disconnected, thereby isolating the faulty photovoltaic string and protecting the subsequent circuit from the harm of the short - circuit fault.

[0164] The above - introduced embodiments are for detecting short - circuit faults at the input end of the DC / DC conversion circuit. The following introduces short - circuit faults at the output end of the DC / DC conversion circuit.

[0165] See Figure 19 This figure is a schematic diagram of another photovoltaic system provided by the embodiment of the present application.

[0166] The embodiment of the present application can not only detect whether there is a short - circuit fault at the input end of the DC / DC conversion circuit, but also detect whether there is a short - circuit fault at the output end of the DC / DC conversion circuit. When there is a short - circuit fault 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 switching device to disconnect, playing a role of fault isolation.

[0167] The photovoltaic system provided in this embodiment further includes: an output current detection circuit 901 and an output voltage detection circuit 902;

[0168] 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.

[0169] The output voltage detection circuit 902 is used to detect the output voltage of the DC / DC conversion circuit 200.

[0170] In order to accurately determine whether a short - circuit fault occurs at the output end of the DC / DC conversion circuit 200, dual - judgment of voltage and current is also required. When both meet the corresponding judgment conditions, it is determined that a short - circuit fault occurs. That is, the controller 600 is used to control all multi - layer switches to disconnect 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 is connected to all photovoltaic strings, the output voltage detection circuit 902 only needs to detect the current flowing through the first - layer switch S1.

[0171] It should be understood that both the input current detection circuit and the output current detection circuit can be implemented by current sensors. When there is a reverse connection in the photovoltaic string, the current direction of the photovoltaic string is opposite to that of a normal photovoltaic string. Therefore, the presence of a reverse - connection fault can be determined by detecting the current direction. For example, when the current of a normal photovoltaic string is positive, the current of the reversely - connected photovoltaic string is negative, that is, less than zero, then it is determined that the current is reversed. Or if it is less than a preset threshold, it is considered reversed and a reverse - connection fault occurs. Current sensors can be set in each photovoltaic string to detect the current of the photovoltaic string. Additionally, for example, if there are four photovoltaic strings, current sensors can be set in three of them, and a current sensor is set for the output current. Then the current of the other photovoltaic string can be obtained by subtracting the sum of the currents of the three photovoltaic strings from the output current, so that one current sensor can be set less.

[0172] For the photovoltaic system provided by the embodiments of the present application, in order to more comprehensively protect the safe and reliable operation of the photovoltaic system, not only can all layer switches in the switch device 400 be disconnected when a reverse - connection fault occurs in the photovoltaic string, but also all layer switches in the switch device 400 can be disconnected when a short - circuit fault occurs in the photovoltaic string, and all layer switches in the switch device 400 can also be disconnected 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 harm to the photovoltaic string.

[0173] The above embodiments introduce the situation of powering the controller by taking power from the photovoltaic string. In order to ensure that the controller can continue to work when the photovoltaic string is disconnected or when the photovoltaic string has no power output, the embodiments of the present application also include another power - taking method, which can be used as the main power - supply method for the controller. The following is a detailed introduction with reference to the drawings.

[0174] See Figure 20 , which is a schematic diagram of another photovoltaic system provided by the embodiments of the present application.

[0175] Since any hardware may malfunction during operation, in order to ensure the safe and reliable operation of the photovoltaic system, two controllers can be set up in the photovoltaic system to form a backup, that is, redundant control is achieved. When one of the controllers has a problem, 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 standby controller 600b;

[0176] Both the main controller 600a and the standby controller 600b are used to control all the switches in the M + 1 layers to disconnect when there is a reverse connection fault in the N photovoltaic strings. That is, in the embodiment of the present application, the main controller 600a and the standby controller 600b work simultaneously. The main controller 600a and the standby controller 600b can 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 at the same time. That is, the two controllers can receive the input voltage, input current, output current, and output voltage at the same time, and can use the received signals to determine whether to control all the switches in the switching device 400 to disconnect. This can ensure that when one of the controllers fails and cannot accurately send a disconnection instruction to the switching device, the other normal controller can accurately and reliably control all the switches to disconnect.

[0177] In addition, in order to ensure the reliability of power supply, the embodiment of the present application provides two auxiliary power sources, that is, including: a main auxiliary power source 903 and a secondary auxiliary power source 904;

[0178] Both the main auxiliary power source 903 and the secondary auxiliary power source 904 are used to supply power to the main controller 600a and the standby controller 600b;

[0179] The main auxiliary power source 903 is connected to the output terminal of the DC / DC conversion circuit 200; that is, the power source of the main auxiliary power source 903 comes from the output terminal of the DC / DC conversion circuit 200.

[0180] The secondary auxiliary power source 904 is connected to the first end of the switching device 400, that is, the power source of the secondary auxiliary power source 904 comes from the photovoltaic string.

[0181] Since the photovoltaic system provided in the embodiment of the present application includes two auxiliary power sources, when one of the auxiliary power sources fails, the other normal auxiliary power source can still supply power to the controller to ensure the normal operation of the controller.

[0182] The following introduces the second power extraction circuit that provides the power source for the main auxiliary power source 903.

[0183] The second power extraction circuit includes: a first diode D7, a second diode D8, a third diode D9, a fourth diode D10, and a second capacitor C2;

[0184] The cathode and anode of the first diode D7 are respectively connected to the positive output terminal of the DC / DC conversion circuit 200 and the first terminal of the second capacitor C2; the anode and cathode of the second diode D8 are respectively connected to the positive output terminal of the DC / DC conversion circuit 200 and the second terminal of the second capacitor C2;

[0185] The anode and cathode of the third diode D9 are respectively connected to the first terminal of the second capacitor C2 and the negative output terminal of the DC / DC conversion circuit 200, and the anode and cathode of the fourth diode D10 are respectively connected to the negative output terminal of the DC / DC conversion circuit 200 and the second terminal of the second capacitor C2;

[0186] The main auxiliary power source 903 is connected to the positive output terminal of the DC / DC conversion circuit 200 through the second power extraction circuit. Since the power source of the main auxiliary power source 903 comes from the output terminal of the DC / DC conversion circuit 200, and generally a photovoltaic system includes multiple DC / DC conversion circuits, and the output terminals of the multiple DC / DC conversion circuits are connected in parallel. Therefore, even if all the layer switches in the switching device 400 are turned off to isolate all the photovoltaic strings connected to the input terminal of the DC / DC conversion circuit 200, the output terminal of the DC / DC conversion circuit 200 can still be powered, that is, from other parallel DC / DC conversion circuits. This can ensure the power supply of the main auxiliary power source 903, thereby ensuring the power supply of the controller.

[0187] In the embodiments of the present application, the specific implementation form of the DC / DC conversion circuit in each of the above photovoltaic systems is not limited. For example, it can be a boost circuit with a bypass relay, that is, a Boost circuit. When the bypass relay is closed, the Boost circuit can be bypassed, that is, there is no need for boosting, and the photovoltaic string is directly connected to the subsequent DC / AC conversion circuit through the bypass relay.

[0188] Generally, in order to increase the output power of the power conversion device, the input terminal of the DC / AC conversion circuit is connected to multiple DC / DC conversion circuits.

[0189] See Figure 21 , which is a schematic diagram of a photovoltaic system including multiple DC / DC conversion circuits provided by an embodiment of the present application.

[0190] The photovoltaic system provided in this embodiment includes: multiple switching devices and multiple DC / DC conversion circuits;

[0191] The multiple switching devices and the multiple DC / DC conversion circuits correspond one by one, that is, the input terminal of each DC / DC conversion circuit is connected to a corresponding switching device. The output terminals of the multiple DC / DC conversion circuits are all connected to the input terminal of the DC / AC conversion circuit 300.

[0192] 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.

[0193] 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.

[0194] 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.

[0195] 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.

[0196] 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.

[0197] See also Figure 22, this figure is a schematic diagram of a DC busbar box provided by an embodiment of the present application.

[0198] The first DC / DC conversion circuit 200a, the second DC / DC conversion circuit 200b, the switching device 400a, and the switching device 400b are all integrated in the DC busbar box 1000.

[0199] Since the DC busbar box provided by the embodiment of the present application includes a switching device, and the switching device includes multiple layers of switches, the multiple layers of switches are interlocked, that is, they are closed or opened simultaneously. The number of layers of the switches depends on the number of photovoltaic strings. If N photovoltaic strings are divided into M groups, the switching device includes M + 1 layers of switches. The first ends of the N photovoltaic strings are all connected to the input end of the DC / DC conversion circuit through the first layer of switches in the M + 1 layers of switches; the M groups of photovoltaic strings are respectively connected to the input end of the DC / DC conversion circuit through the M layers of switches in the M + 1 layers of switches; when there is a reverse connection fault in the N photovoltaic strings, the M + 1 layers of switches are all opened, that is, as long as there is a reverse connection fault in one of the photovoltaic strings, all layers of switches in the switching device are opened.

[0200] In the embodiment of the present application, it is not limited whether the first end of the photovoltaic string is the positive layer or the negative layer, that is, the N photovoltaic strings can be connected in a common positive layer or a common negative layer. For the convenience of description, in the following embodiments, the case where the N photovoltaic strings are connected in a common positive layer is taken as an example for introduction. When the N photovoltaic strings are connected in 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 one layer of switches. The negative layers of the N photovoltaic strings are grouped in pairs and respectively connected to the negative input end of the DC / DC conversion circuit through the corresponding layer of 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 the switches in the switching device is reduced to a certain extent, thereby reducing the complexity of the hardware structure and the cost.

[0201] The above-described embodiments are all introduced by taking the power conversion circuit including a DC / DC conversion circuit and a DC / AC conversion circuit as an example. The implementation of the power conversion circuit including only a DC / AC conversion circuit is introduced below with reference to the accompanying drawings.

[0202] Based on a photovoltaic system provided by the above embodiments, the embodiment of the present application further provides a fault isolation method.

[0203] The fault isolation method provided in this embodiment is applied to the photovoltaic system introduced in any of the above embodiments. The photovoltaic system includes: a switching device and a power conversion circuit; the first end of the switching device is connected to N photovoltaic strings, and the second end of the switching device is connected to the power conversion circuit; the switching device includes a rotating shaft and multiple layers of switches stacked along the extension direction of the rotating shaft. The multiple layers of switches include a first-layer switch and at least two second-layer switches; the current-carrying capacity of the first-layer switch is greater than that of the second-layer switch. The input end of the power conversion circuit is connected to the switching 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; where the first pole is the positive pole or the negative pole, and the second pole is the other pole opposite to the first pole.

[0204] The method includes:

[0205] Judge that there is a reverse connection fault in the N photovoltaic strings, and control all the multi-layer switches to disconnect.

[0206] Judging that there is a reverse connection fault in the N photovoltaic strings specifically includes:

[0207] Obtain the current of each of the N photovoltaic strings.

[0208] Judge that the current of any one of the N photovoltaic strings is reversed according to the current of each photovoltaic string, and judge that there is a reverse connection fault in the N photovoltaic strings.

[0209] When there is a reverse connection in the photovoltaic string, the current direction of the photovoltaic string is opposite to that of the normal photovoltaic string. Therefore, it is possible to judge whether there is a reverse connection fault by detecting the current direction. For example, when the current of the normal photovoltaic string is positive, the current of the reversely connected photovoltaic string is negative, that is, less than zero, then it is judged that the current is reversed, or it is less than a preset threshold, then it is considered reversed and a reverse connection fault occurs. Current sensors can be set in each photovoltaic string to detect the current of the photovoltaic string. In addition, for example, including four photovoltaic strings, current sensors can be set in three of the photovoltaic strings, and a current sensor can be set for the output current. Then the current of the other photovoltaic string can be obtained by subtracting the sum of the currents of the three photovoltaic strings from the output current, so that one current sensor can be set less.

[0210] It should be understood that in this application, "at least one (item)" means one or more, and "a plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: only A exists, only B exists, and both A and B exist simultaneously. Among them, A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one (item) of the following" or its similar expression refers to any combination of these items, including any combination of single items (items) or plural items (items). For example, at least one (item) 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, and c can be single or multiple.

[0211] As described above, the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit them; although this application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this 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, a multi-layer switch stacked along the extending direction of the rotating shaft, and a tripping device, 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 of 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; 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 a short circuit fault occurs at the output end of the power conversion circuit, control the trip device to drive the multi-layer switches to disconnect in a linked manner, 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 in parallel among the N photovoltaic strings.

2. The power conversion device according to claim 1, wherein Along the extension direction of the rotation axis, the layer height of the first layer switches is greater than or equal to the layer height of any one of the second layer switches.

3. 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.

4. 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.

5. 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.

6. The power conversion device according to claim 5, 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.

7. The power conversion device according to claim 5 or 6, 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.

8. The power conversion device according to claim 1, characterized in that, The controller is specifically used to send a disconnection instruction to the trip 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, and the trip device operates according to the disconnection instruction and drives all the multi-layer switches to disconnect.

9. The power conversion device according to claim 1, wherein, Any layer switch of the switch device comprises: a housing, a moving contact and at least one stationary contact arranged on 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 turned off, the moving contact and the static contact in the multi-layer switch are both separated; When the multi-layer switch is turned on, the moving contact and the static contact in the multi-layer switch are both in contact.

10. The power conversion device according to claim 9, characterized in that, The 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 from the first static contact, and the other end of the moving contact is used to contact or separate from 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.

11. The power conversion device according to claim 10, wherein, The first static contact of any layer of the switch includes a connecting portion protruding from the housing, 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.

12. The power conversion device according to claim 10, characterized in that, 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 the switch includes a pin portion protruding from the housing, and the pin portion is used to be electrically connected to the circuit board to be connected to the power conversion circuit.

13. The power conversion device according to claim 12, characterized in that, The number of pin portions of the first layer switch is greater than the number of pin portions of the second layer switch.

14. The power conversion device according to claim 12, characterized in that, 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.

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

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

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