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 original application has the application number 202411269170.X and the original application date is September 11, 2024. The entire contents of the original application are incorporated herein by reference. Technical Field

[0002] This application relates to the field of photovoltaic power generation technology, and in particular to a power conversion device. Background Technology

[0003] Currently, photovoltaic (PV) systems mainly include single-stage and two-stage power conversion modes. Single-stage power conversion refers to the PV array's direct current (DC) being directly converted to alternating current (AC) via a DC / AC (Direct Current / Alternating Current) circuit. Two-stage power conversion, on the other hand, involves the PV array's DC first undergoing a DC / DC (Direct Current / Direct Current) conversion, followed by a second-stage DC / AC conversion, ultimately converting the DC to AC. Because two-stage power conversion is more efficient than single-stage power conversion, its application in PV power generation systems is becoming increasingly widespread.

[0004] A single photovoltaic (PV) string typically has limited capacity. To increase capacity, multiple PV strings are connected in parallel to the input of a DC / DC converter circuit, meaning the positive terminals of multiple PV strings are connected together, and the negative terminals of multiple PV strings are connected together. However, if one PV string is reversed, the current from the other PV strings will flow back into the reversed PV string. Since the diodes connected in anti-parallel in the solar panels of a PV string can only withstand a limited current, when the current from multiple PV strings flows back into one PV string, it will damage the solar panels in that PV string.

[0005] In existing technologies, a circuit breaker or fuse is typically connected in series with each photovoltaic (PV) string to disconnect it from other PV strings in the event of a fault in one string and backfeeding from other strings. However, this approach requires too many circuit breakers or fuses, which, as the number of connected PV strings increases, can lead to excessively large and costly power conversion equipment. Summary of the Invention

[0006] This application provides a power conversion device that can promptly isolate the fault when a photovoltaic string is reverse-connected, ensuring the safety of the photovoltaic string and complete isolation between it and the power circuit. At the same time, it can also save the number of switching layers in the switching device, reducing the size and cost of the switching device.

[0007] This application provides a power conversion device, including: a switching device, a power conversion circuit, and a controller. The switching device is connected between photovoltaic strings and 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 of switches and at least two second layer switches, where the number of first layer switches is less than the number of second layer switches; the current-carrying capacity of the first layer switches is greater than the current-carrying capacity of the second layer switches. The first pole of each of the N photovoltaic strings is connected to a first layer switch, and the second pole of some of the N photovoltaic strings is connected to a second layer switch in the multiple layers of switches. The first pole is either positive or negative, and the second pole is the opposite pole; N is a positive integer greater than or equal to 2. The controller is used to: when a reverse connection fault exists in a photovoltaic string, or a short circuit fault exists in a photovoltaic string, or a short circuit fault occurs at the output of the power conversion circuit, control all the multiple layers of switches in the switching device to disconnect the positive and negative poles of the photovoltaic strings from the power conversion circuit, and allow at most two or three of the N photovoltaic strings to be connected in parallel.

[0008] In the above implementation scheme, the switch includes a multi-layer switch, which is a single linked switch, i.e., a multi-P (Pole) switch. The multi-layer switches are simultaneously open or closed. When a reverse connection fault exists in any of the N photovoltaic strings, all multi-layer switches are open; that is, if a reverse connection fault occurs in any one photovoltaic string, all pole switches in the switching device are open. In this embodiment, the multi-layer switch is configured with first-layer and second-layer switches with different current-carrying capacities. This allows the layer switches with different current-carrying capacities to adapt to the connection of different numbers of photovoltaic strings, thus making the grouping and connection methods of photovoltaic strings more flexible. Furthermore, 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 single first-layer switch. This is equivalent to the entire first pole of N photovoltaic strings being connected to a single first-layer switch. As the number of connected photovoltaic strings increases, this first-layer switch with a larger current-carrying capacity can significantly reduce the number of layer switches required when connecting N photovoltaic strings, eliminating the need for multiple layer switches with smaller current-carrying capacities for current distribution. Furthermore, the N photovoltaic strings can be grouped according to their specifications or circuit design. At least two groups of photovoltaic strings can have their second poles connected to corresponding second-level switches. That is, each second-level switch can be connected to the second poles of a subset of the N photovoltaic strings. In this implementation, it is not limited to all the photovoltaic strings in the N strings having their second poles connected to the second-level switch of a single switching device. For example, other groups of the N photovoltaic strings can also be shut down using other switching devices. However, regardless of the connection relationship, when the multi-level switches of the switching device are controlled to disconnect, at most two or three photovoltaic strings in the N strings will be connected in parallel. Thus, in the event of a reverse connection or short circuit fault in a photovoltaic string, at most one or two photovoltaic strings will provide reverse power to the faulty string, without affecting the safety of the photovoltaic strings. In other words, the above-mentioned implementation scheme of this application enhances the current-carrying capacity of the first-layer switch, enabling more photovoltaic modules or those with larger output currents to be connected to a single first-layer switch, thereby reducing the number of first-layer switches. Furthermore, by connecting the second poles of N photovoltaic strings to different second-layer switches, flexible grouping of the N photovoltaic strings is achieved, while ensuring that the photovoltaic strings are not subjected to excessive reverse current. That is, the above-mentioned implementation scheme can greatly reduce the number of multi-layer switches in the switching device, thereby reducing the size and cost of the switching device and power conversion equipment. At the same time, it can also ensure the safety of the photovoltaic strings and power circuits, and simplify control and circuit connections.

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

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

[0011] In both implementation schemes described above, the first-layer switch has a greater current-carrying capacity than the second-layer switch. Therefore, the internal components of the first-layer switch also need to be adapted to handle this larger current-carrying capacity. Consequently, 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 can be greater than or equal to the radial length of the second-layer switch. While this will increase the volume of the first-layer switch somewhat, compared to using multiple layer switches with smaller current-carrying capacities to connect the first poles of N photovoltaic strings, the reduced number of layer switches significantly reduces the overall size of the switching device.

[0012] In one possible implementation, at least two second-layer switches have the same current-carrying capacity, or at least two second-layer switches have different current-carrying capacities. Where the current-carrying capacities of at least two second-layer switches are different, it is possible to accommodate the connection of different numbers of photovoltaic strings to the second pole.

[0013] In the above implementation scheme, the second layer switches can all be uniform layer switches with the same current carrying capacity, or layer switches with different current carrying capacities can be used to adapt to the current carrying capacity of different groups according to the grouping situation.

[0014] In one possible implementation, N photovoltaic strings can be divided into M groups of photovoltaic strings. Each group of photovoltaic strings includes one photovoltaic string, or two or three photovoltaic strings connected in parallel. At least two of the two second-level switches are connected to the second poles of two photovoltaic strings in the M groups. That is, among all the second-level switches, at least two are connected one-to-one to the second poles of two photovoltaic strings in the M groups. For example, photovoltaic strings in group A are connected to one second-level switch, and photovoltaic strings in group B are connected to another second-level switch. If there are more groups of photovoltaic strings, they can be connected using more second-level switches of this switching device, or through other switching devices, or implemented in other ways.

[0015] In one possible implementation, at least two second-layer switches comprise M second-layer switches, each of which is connected one-to-one with the second pole of one of the M groups of photovoltaic strings. That is, the second poles of all groups of photovoltaic strings are connected to the power circuit through corresponding connections with the multiple second-layer switches of this switching device.

[0016] In both implementation schemes described above, the N photovoltaic strings can be rationally grouped and connected to the corresponding second-level switches, so that each group has at most two or three photovoltaic strings connected in parallel. This way, if a faulty photovoltaic string occurs in a group, after disconnecting the multi-level switches, there will be at most one or two photovoltaic strings experiencing backflow current, ensuring the safety of the photovoltaic strings. Simultaneously, increasing the number of photovoltaic strings within each group can reduce the number of second-level switches, thereby further reducing the number of layer switches and the overall size of the switching device.

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

[0018] In the above implementation scheme, the number of photovoltaic strings in each group is limited to two or less, and preferably two. That is, when N is even, N photovoltaic strings can be grouped in pairs. When N is odd, the other N-1 photovoltaic strings are grouped in pairs, and the remaining photovoltaic string is grouped alone. This ensures that when a photovoltaic string fails, the faulty string can withstand at most one reverse current after the switching device is disconnected, which further guarantees the safety of the photovoltaic string. At the same time, it can minimize the number of photovoltaic strings grouped under this safety level, thereby minimizing the number of second-level switches and reducing the size of the switching device.

[0019] In one possible implementation, the N photovoltaic strings can be connected with a common positive terminal or a common negative terminal. For example, when the N photovoltaic strings are connected with a common positive terminal, their positive terminals are connected together, and the positive terminals of the N photovoltaic strings are connected to the input terminal of the power conversion circuit through a first-level switch in a multilayer switch. The N photovoltaic strings are grouped in pairs, and the negative terminals of each group of photovoltaic strings are connected to the input terminal of the power conversion circuit through a second-level switch in a multilayer switch. For example, when the N photovoltaic strings are connected with a common negative terminal, their negative terminals are connected together, and the negative terminals of the N photovoltaic strings are connected to the input terminal of the power conversion circuit through a first-level switch in a multilayer switch. The N photovoltaic strings are grouped in pairs, and the positive terminals of each group of photovoltaic strings are connected to the input terminal of the power conversion circuit through a second-level switch in a multilayer switch.

[0020] In one possible implementation, to ensure reliable disconnection of the switches in the switching device when a reverse connection fault occurs in the photovoltaic string, the switching device provided in this application embodiment may further include a tripping device. A controller is configured to send a disconnection command to the tripping device when a reverse connection fault, a short circuit fault, or a short circuit fault occurs at the output of the power conversion circuit occurs in the photovoltaic string. The tripping device operates according to the disconnection command, causing all multi-layer switches to disconnect. Before the tripping device resets, all multi-layer switches remain in the open state. That is, before the tripping device resets, the multi-layer switches remain in the open state, thereby preventing the multi-layer switches from malfunctioning and closing before the fault is cleared.

[0021] In one possible implementation, each layer switch of the switching device includes: a housing, a moving contact disposed on the housing, and at least one stationary contact, the moving contact rotating relative to the housing; the moving contact is fixed relative to a rotating shaft, the rotating shaft being used to drive the moving contact to rotate so as to separate from or make contact with the stationary contact; when the multi-layer switch is open, all moving contacts and stationary contacts in the multi-layer switch are separated; when the multi-layer switch is connected, all moving contacts and stationary contacts 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 adjacent moving contacts, for example, by interlocking with each other, thereby achieving simultaneous separation or contact of the moving contacts of all layer switches relative to the stationary contacts when the rotating shaft rotates.

[0022] In the above implementation scheme, each layer of the switching device is equipped with a moving contact and a stationary contact. The stationary contact can be positioned on the rotation path of the moving contact, thereby allowing the moving contact and the stationary contact to separate or make contact. The moving contact and the rotating shaft of each layer of the switch are relatively fixed, allowing them to rotate relative to the housing. Specifically, this can be achieved by directly fixing the moving contact to the rotating shaft or by fixing the moving contacts of adjacent layers. Therefore, the rotating shaft can drive the rotation of the moving contacts of all layers, thereby enabling all layers of switches to be linked together for disconnection or connection.

[0023] In one possible implementation, at least one stationary contact includes a first stationary contact and a second stationary contact, one end of a moving contact is used to contact or separate from the first stationary contact, and the other end of the moving contact is used to contact or separate from the second stationary contact; the first stationary contact is used to be electrically connected to the photovoltaic string, and the second stationary contact is used to be electrically connected to the power conversion circuit.

[0024] In the above implementation scheme, the two stationary contacts are electrically connected to the photovoltaic string and the power conversion circuit, respectively. When the two ends of the moving contact separate from the two stationary contacts, the electrical connection between the photovoltaic string and the power conversion circuit is broken. When the two ends of the moving contact contact the two stationary contacts, a circuit is formed, thus completing the electrical connection between the photovoltaic string and the power conversion circuit.

[0025] In one possible implementation, the first stationary contact of any layer switch includes a connecting portion extending out of the housing for electrical connection with 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.

[0026] In the above implementation scheme, since the current carrying capacity of the first layer switch is greater than that of the second layer switch, the connection part of the first stationary contact of the first layer switch also needs to be adapted to the large current carrying capacity. Therefore, the area of ​​the connection part of the first layer switch is larger than that of the connection part of the second layer switch.

[0027] In one possible implementation, the power conversion device further includes a circuit board on which the power conversion circuit is located; the second stationary contact of any layer switch includes a lead portion extending out of the housing for electrical connection with the circuit board to connect with the power conversion circuit.

[0028] In the above implementation scheme, the switching device can be directly plugged into the circuit board through the pin section, and then connected to the power conversion circuit through the circuit board traces. This can save the space occupied by the cable connection, thereby saving the internal space of the power conversion equipment and improving the power density.

[0029] In one possible implementation, the number of pins on the first layer switch is greater than the number of pins on the second layer switch.

[0030] In one possible implementation, the pin width of the first layer switch is greater than the pin width of the second layer switch.

[0031] In the two implementation schemes mentioned above, since the current carrying capacity of the first layer switch is greater than that of the second layer switch, the pins of the first layer switch also need to be adapted to the larger current carrying capacity. Therefore, the number of pins of the first layer switch is greater than the number of pins of the second layer switch, or the pin width of the first layer switch is greater than the pin width of the second layer switch.

[0032] In one possible implementation, the multilayer switch includes a plurality of first-layer switches, each of which is spaced apart by at least two second-layer switches.

[0033] In the above implementation, since the positive and negative terminals of the N photovoltaic strings are connected through the first layer switch and the second layer switch respectively, and the multiple first layer switches are separated by at least two second layer switches, that is, the first layer switches and multiple second layer switches are interleaved, which facilitates the connection of the positive and negative terminals of the photovoltaic strings with the first layer switches and the second layer switches, and avoids the tangling of cables.

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

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

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

[0037] One possible implementation 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 terminal of the first-layer switch and the first terminal of each of the M second-layer switches, obtaining M voltages; the controller, when at least one of the M voltages is less than a first voltage threshold and the current of at least one of the N photovoltaic strings is greater than a first current threshold, controls all multi-layer switches to open. If the voltage of any one set of photovoltaic strings is low, it indicates a possible short-circuit fault in some of the photovoltaic strings. It should be understood that when a short-circuit fault exists, the voltage of the photovoltaic string will decrease and the current will increase. To accurately determine a short-circuit fault, both voltage and current can be used for judgment. If a photovoltaic string has a short-circuit fault, all switches in the fault isolation circuit will open, thereby isolating the faulty photovoltaic string and protecting the downstream circuit from the harm of the short-circuit fault.

[0038] In one possible implementation, the power conversion circuit includes a DC / DC conversion circuit, wherein the photovoltaic string is connected to the input terminal of the DC / DC conversion circuit via a switching device, and the output terminal of the DC / DC conversion circuit is connected to the input terminal of the DC / AC conversion circuit.

[0039] In one possible implementation, this embodiment can detect not only whether a short circuit fault occurs at the input terminal of the DC / DC converter circuit, but also whether a short circuit fault occurs at the output terminal of the DC / DC converter circuit. When a short circuit fault occurs at the output terminal of the DC / DC converter circuit, in order to prevent the fault range from expanding and to play a protective role, it is also necessary to control all layer switches in the switching device to be disconnected, thereby playing a fault isolation role. That is, the photovoltaic system provided in this embodiment also includes: an output current detection circuit for detecting the current at the second terminal of the first layer switch; an output voltage detection circuit for detecting the output voltage of the DC / DC converter circuit; and a controller for controlling all layer switches to be disconnected when the current at the second terminal of the first layer switch is greater than a second current threshold and the voltage at the output terminal of the DC / DC converter circuit is less than a second preset voltage.

[0040] In one possible implementation, since any hardware may malfunction during operation, two controllers can be set up in the photovoltaic system to form a backup, i.e., to achieve redundant control, so that if one controller fails, normal control operation is not affected. That is, in the photovoltaic system provided in this embodiment, the controllers include: a main controller and a backup controller; both the main controller and the backup controller are used to control the multi-layer switches to disconnect when a reverse connection fault exists in N photovoltaic strings.

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

[0042] In one possible implementation, in order to reliably power the controller under any circumstances, the photovoltaic system provided in this application embodiment adopts a competitive power supply method, that is, it further includes: a first power supply circuit, used to draw power from the group with the highest voltage among the M groups of photovoltaic strings to supply power to the auxiliary source.

[0043] In one possible implementation, the first power supply 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 terminal of each of the M+1 layer switches is connected to the first terminal and the second terminal of the first capacitor through a forward bias diode and a reverse bias diode, respectively; the first terminal of each of the M+1 layer switches is connected to the corresponding photovoltaic string, and the second terminal of each of the M+1 layer switches is connected to the input terminal of the DC / DC conversion circuit.

[0044] In one possible implementation, the photovoltaic system provided in this application embodiment further includes a second power supply circuit for powering the main auxiliary source. The second power supply circuit includes: a first diode, a second diode, a third diode, a fourth diode, and a second capacitor. The cathode and anode of the first diode are respectively connected to the positive output terminal of the DC / DC converter 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 converter 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 converter circuit. The anode and cathode of the fourth diode are respectively connected to the negative output terminal of the DC / DC converter circuit and the second terminal of the second capacitor. The main auxiliary source is connected to the positive output terminal of the DC / DC converter circuit. Since the power source of the main auxiliary source comes from the output terminal of the DC / DC converter circuit, and since a typical photovoltaic system includes multiple DC / DC converter circuits with their output terminals connected in parallel, even if all layer switches in the switching device are disconnected, isolating all photovoltaic strings connected to the input terminals of the DC / DC converter circuit, the output terminal of the DC / DC converter circuit can still be powered, i.e., it comes from other parallel DC / DC converter circuits. This ensures the power supply to both the main and auxiliary power sources, thereby guaranteeing the power supply to the controller.

[0045] One possible implementation includes: multiple switching devices and multiple DC / DC conversion circuits; the multiple switching devices and multiple DC / DC conversion circuits correspond one-to-one.

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

[0047] Based on the power conversion device provided in the above embodiments, this application also provides a fault isolation method applied to the power conversion device, including: obtaining the current of each photovoltaic string in N photovoltaic strings; determining that the current of any one of the N photovoltaic strings is reversed based on the current of each photovoltaic string, and determining that there is a reverse connection fault in the N photovoltaic strings; when there is a reverse connection fault in the N photovoltaic strings, controlling the multi-layer switches in the switching device to disconnect all of them to disconnect the positive and negative terminals of the photovoltaic strings from the power conversion circuit. Attached Figure Description

[0048] Figure 1a A schematic diagram of a photovoltaic system provided in an embodiment of this application;

[0049] Figure 1b A schematic diagram of yet another photovoltaic system provided in this application embodiment;

[0050] Figure 2 A schematic diagram of another photovoltaic system provided in the embodiments of this application;

[0051] Figure 3 This is a schematic diagram of multiple photovoltaic modules connected in series and parallel at the input of a DC / DC converter circuit.

[0052] Figure 4 A schematic diagram of a photovoltaic system with a switching device provided in an embodiment of this application;

[0053] Figure 5 This is a schematic diagram illustrating the connection relationship between a switching device and a photovoltaic string, provided in an embodiment of this application.

[0054] Figure 6a This is a schematic diagram illustrating the connection relationship between another switching device and a photovoltaic string, provided in an embodiment of this application.

[0055] Figure 6b This is a schematic diagram illustrating the connection relationship between another switching device and a photovoltaic string provided in an embodiment of this application;

[0056] Figure 6c This is a schematic diagram illustrating the connection relationship between another switching device and a photovoltaic string, provided in an embodiment of this application.

[0057] Figure 7 This is a schematic diagram illustrating the connection relationship between another switching device and a photovoltaic string, provided in an embodiment of this application.

[0058] Figure 8a This application provides a schematic diagram illustrating the connection relationship between multiple switching devices and a photovoltaic string.

[0059] Figure 8b This is a schematic diagram illustrating the connection relationship between multiple switching devices and a photovoltaic string, as provided in an embodiment of this application.

[0060] Figure 9 This is a schematic diagram of the structure of a switching device provided in an embodiment of this application;

[0061] Figure 10 An exploded view of a switching device provided in an embodiment of this application;

[0062] Figure 11 This is a schematic diagram of the structure of a first-layer switch provided in an embodiment of this application;

[0063] Figure 12 This is a schematic diagram of the structure of a second-layer switch provided in an embodiment of this application;

[0064] Figure 13 This is a schematic diagram of another second-layer switch provided in an embodiment of this application;

[0065] Figure 14 For this application Figure 9An embodiment provides a schematic diagram of another angle of a switching device;

[0066] Figure 15 This is a schematic diagram of another switching device provided in an embodiment of this application;

[0067] Figure 16 For this application Figure 15 An embodiment provides a schematic diagram of another angle of a switching device;

[0068] Figure 17 A schematic diagram of another photovoltaic system provided in the embodiments of this application;

[0069] Figure 18 A schematic diagram of yet another photovoltaic system provided in this application embodiment;

[0070] Figure 19 A schematic diagram of another photovoltaic system provided in the embodiments of this application;

[0071] Figure 20 A schematic diagram of another photovoltaic system provided in the embodiments of this application;

[0072] Figure 21 A schematic diagram of a photovoltaic system including multiple DC / DC conversion circuits provided in this application;

[0073] Figure 22 This is a schematic diagram of a DC combiner box provided in this application. Detailed Implementation

[0074] The terms "first," "second," etc., used in the following description are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature specified with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "multiple" means two or more.

[0075] Furthermore, in this application, directional terms such as "upper" and "lower" may be defined relative to the orientation in which the components are schematically placed in the accompanying drawings. It should be understood that these directional terms can be relative concepts, used for relative description and clarification, and can change accordingly depending on the orientation in which the components are placed in the accompanying drawings.

[0076] In this application, unless otherwise expressly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, the term "coupled" can refer to a method of electrical connection for signal transmission. "Coupled" can be a direct electrical connection or an indirect electrical connection through an intermediate medium.

[0077] This application relates to a photovoltaic system, which may include a two-stage power conversion or a single-stage power conversion. The photovoltaic system including a two-stage power conversion circuit is described first. In order to enable those skilled in the art to better understand the technical solution provided by the embodiments of this application, the photovoltaic system provided by the embodiments of this application is described below with reference to the accompanying drawings.

[0078] See Figure 1a The figure is a schematic diagram of a photovoltaic system provided in an embodiment of this application.

[0079] The photovoltaic system provided in this application embodiment includes a DC / DC converter circuit 200 and a DC / AC converter circuit 300. The input terminal of the DC / DC converter circuit 200 is connected to multiple photovoltaic strings, and the input terminal of the DC / DC converter circuit 200 is connected to a photovoltaic array 100, wherein the photovoltaic array 100 includes multiple photovoltaic strings. Figure 1a This example uses four photovoltaic strings, PV1 to PV4. PV1 to PV4 can be connected in parallel to the input of the DC / DC converter 200, thereby increasing the input current of the DC / DC converter 200. The output of the DC / DC converter 200 is connected to the DC / AC converter 300.

[0080] The DC / DC converter circuit 200 performs DC-DC conversion, and the DC / AC converter circuit 300 performs DC-AC conversion. The output of the DC / AC converter circuit 300 can be connected to a transformer, i.e., connected to the power grid through the transformer.

[0081] in addition, Figure 1a The diagram shown is only a schematic of one DC / DC converter circuit 200 connected to a DC / AC converter circuit 300. Generally, in order to increase the output power of the DC / AC converter circuit 300, multiple DC / DC converter circuits 200 can be connected to the input terminal of the DC / AC converter circuit 300, and multiple photovoltaic strings can be connected to the input terminal of each DC / DC converter circuit 200.

[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. Alternatively, the photovoltaic system provided in this embodiment may also include only a DC / AC conversion circuit, excluding the DC / DC conversion circuit. See also... Figure 1b As shown in the figure, this figure is a schematic diagram of another photovoltaic system provided in the embodiment of this application.

[0083] Compare Figure 1a and Figure 1b It can be seen that, Figure 1b The photovoltaic strings PV1-PV4 are directly connected to the input terminal of the DC / AC conversion circuit 300. The technical solutions provided in the following embodiments of this application do not limit the specific implementation of the power conversion circuit; that is, they can be... Figure 1a The power conversion circuit shown includes a DC / DC converter 200 and a DC / AC converter 300, and can also be... Figure 1b The power conversion circuit shown only includes the DC / AC conversion circuit 300. The following description primarily uses a power conversion circuit that includes a DC / DC conversion circuit as an example.

[0084] See Figure 2 This figure is a schematic diagram of another photovoltaic system provided in an embodiment of this application.

[0085] Figure 2 The example described uses two DC / DC converter circuits, both with their outputs connected to a DC / AC converter circuit 300. Specifically, the outputs of the first DC / DC converter circuit 200a and the second DC / DC converter circuit 200b are connected in parallel to the input of the DC / AC converter circuit 300. The first DC / DC converter circuit 200a and the second DC / DC converter circuit 200b can be integrated into a DC combiner box 1000, which provides maximum power point tracking (MPPT) functionality.

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

[0087] Figure 1a , Figure 1b or Figure 2In the photovoltaic system shown, since the input terminal of the DC / DC converter circuit is connected to multiple photovoltaic strings, which are usually connected in parallel, when one of the photovoltaic strings is reversed (i.e., the positive and negative terminals are reversed), the current from the other photovoltaic strings will flow back into the reversed photovoltaic string. Since the diodes connected in anti-parallel in the photovoltaic string can only withstand a limited amount of current, when the current from multiple photovoltaic strings flows back into one photovoltaic string, it will cause damage to the batteries in that photovoltaic string.

[0088] See Figure 3 The figure shows a schematic diagram of multiple photovoltaic modules connected in series and parallel at the input of a DC / DC converter circuit.

[0089] Continuing with the example of four photovoltaic strings, Figure 3 In this circuit, a photovoltaic (PV) string is considered equivalent to a single battery. Traditionally, the positive terminals PV1+ through PV4+ of the four PV strings are connected together to the positive input terminal of the DC / DC converter circuit 200, and the negative terminals PV1- through PV4- of the four PV strings are connected together to the negative input terminal of the DC / DC converter circuit 200. For example, when PV4 is reversed (i.e., the positive and negative terminals are reversed), it can be seen that the positive terminals of PV1-PV3 are connected to the positive input terminal of the DC / DC converter circuit 200, while the positive terminal of PV4 is connected to the negative input terminal of the DC / DC converter circuit 200. Figure 3 This shows the reverse connection of one photovoltaic string PV4. Figure 3 As can be seen, the currents of PV1-PV3 are represented by dashed lines with arrows, while the current of PV4 is represented by solid lines with arrows. This means that the currents of PV1-PV3 will flow back into PV4, potentially damaging PV4 due to excessive current. On the other hand, Figure 3 A fuse is added to each photovoltaic string, that is, the four photovoltaic strings are connected in series with fuses F1-F4 respectively. The fuse will increase the circuit loss. On the other hand, the fuse requires twice the input current to break, and the reliability is relatively low and the cost is high.

[0090] To address the problems caused by reverse connection of photovoltaic strings, this application provides a power conversion device 10 for use in the aforementioned photovoltaic system, specifically an inverter. (See also...) Figure 4This figure is a schematic diagram of a photovoltaic system with a switching device provided in an embodiment of this application. Specifically, the power conversion device 10 of this embodiment includes a switching device 400, a power conversion circuit (e.g., a DC / DC conversion circuit 200 and a DC / AC conversion circuit 300), and a controller 600. N photovoltaic strings (e.g., PV1 to PV4) are connected to the input terminal of the power conversion circuit through the switching device 400. When a photovoltaic string malfunctions, the controller 600 can control the switching device 400 to disconnect from the input terminal of the power conversion circuit to achieve fault isolation. The switching device 400 includes a rotating shaft and multiple layers of switches stacked along the extension direction of the rotating shaft. In this embodiment, the multiple layers of switches can achieve simultaneous linkage action (opening or closing) through the rotation of the rotating shaft. As long as one or more photovoltaic strings connected to the multiple layers of switches experience a reverse connection fault, all switches of the multiple layers of switches will be linked and disconnected through the rotation of the rotating shaft.

[0091] Specifically, the multi-layer switch in this embodiment includes a first-layer switch and at least two second-layer switches, with the number of first-layer switches being less than the number of second-layer switches. The first-layer switches are used to connect simultaneously to the first poles of N photovoltaic strings, and each second-layer switch is used to connect to the second poles of a portion of the N photovoltaic strings. The first pole is either positive or negative, and the second pole is the opposite pole to the first pole. For example, if the first pole is positive, the second pole is negative; if the first pole is negative, the second pole is positive. The controller 600 is used to: when a reverse connection fault exists in any of the N photovoltaic strings, or a short-circuit fault exists in any of the N photovoltaic strings, or a short-circuit fault occurs at the output of the power conversion circuit, control all multi-layer switches in the switching device 400 to disconnect the positive and negative poles of the N photovoltaic strings from the power conversion circuit, and to connect at most two or three photovoltaic strings in parallel.

[0092] Essentially, N photovoltaic (PV) strings can be grouped according to their specifications or circuit design. At least two groups of PV strings can have their second terminals connected to corresponding second-layer switches. In other words, each second-layer switch can connect to the second terminals of a subset of the N PV strings. In this implementation, the multi-layer switches include first-layer and second-layer switches with different current-carrying capacities. This allows the switches with different current-carrying capacities to accommodate different numbers of PV strings, making the grouping and connection of PV strings more flexible and adaptable to various scenarios and product requirements.

[0093] It should be noted that the embodiments of this application do not limit the second poles of all photovoltaic strings in N photovoltaic strings to be connected to the second-level switches of the same switching device. For example, other groups in the N photovoltaic strings can also be turned off through other switching devices. However, regardless of the connection relationship, when the multi-layer switches of the switching device are controlled to disconnect, at most two or three photovoltaic strings in the N photovoltaic strings can be connected in parallel. This ensures the safety of the photovoltaic strings while allowing for flexible grouping. The following description will take the case where the second poles of all photovoltaic strings in N photovoltaic strings are connected to the second-level switches of the same switching device as an example. That is, the N photovoltaic strings are divided into M groups of photovoltaic strings, and there are also M second-level switches, with each of the M second-level switches connected to the second pole of one of the M groups of photovoltaic strings.

[0094] Specifically, N photovoltaic (PV) strings are divided into at least two groups of PV strings. The first pole of each of the N PV strings is connected to a first-layer switch, and the second pole of each group of PV strings is connected to a second-layer switch. Understandably, in this connection method, the first-layer switches connect to all N PV strings, while each second-layer switch connects to a portion of the N PV strings.

[0095] When grouping N photovoltaic (PV) strings, the same number of N PV strings can be grouped in different ways, but the grouping must meet the requirement of the reverse current that the PV strings can withstand. For example, if the specifications of the PV strings can only withstand the reverse current of one PV string, then each group can only include a maximum of two parallel PV strings, or only one PV string. As another example, if the specifications of the PV strings can withstand the reverse current of two PV strings, then each group can include a maximum of two or three parallel PV strings, or only one PV string.

[0096] For example, when N is 5, the N photovoltaic strings can be divided into two groups: one group contains 2 parallel photovoltaic strings, and the other group contains 3 parallel photovoltaic strings. Alternatively, the N photovoltaic strings can be divided into three groups: the first group contains 1 photovoltaic string, and the second and third groups each contain 2 parallel photovoltaic strings. Of course, each group can also contain only one photovoltaic string, in which case the N photovoltaic strings are divided into 5 groups.

[0097] It is understood that in this embodiment, the number of groups is consistent with the number of second-layer switches. The fewer the groups, the fewer the number of second-layer switches in the switching device, thus reducing cost and size. Therefore, while ensuring safety, fewer groups can be set to save on the number of layer switches. The following embodiments are mainly illustrated by pairwise parallel connections, but it should be understood that this embodiment is not limited to this, and the grouping method can be more flexible according to the scenario and product requirements.

[0098] To better protect the photovoltaic strings from excessive current during reverse connection, two photovoltaic strings can be grouped together, with the second pole of each group of photovoltaic strings corresponding one-to-one with a second-layer switch in a multilayer switch.

[0099] The following example uses N photovoltaic strings, with each pair of photovoltaic strings forming a group.

[0100] N photovoltaic strings share a common positive terminal, and the positive terminals of the N photovoltaic strings are connected to the input terminal of the power conversion circuit through a first-level switch in a multilayer switch; the N photovoltaic strings are paired up, and the negative terminals of each pair of photovoltaic strings are connected to the input terminal of the power conversion circuit through a second-level switch in a multilayer switch.

[0101] or,

[0102] N photovoltaic strings share a common negative terminal. The negative terminals of the N photovoltaic strings are connected to the input terminal of the power conversion circuit through a first-level switch in a multilayer switch. The N photovoltaic strings are paired up, and the positive terminals of each pair of photovoltaic strings are connected to the input terminal of the power conversion circuit through a second-level switch in a multilayer switch.

[0103] N photovoltaic strings can be divided into M groups. When N is even, M = N / 2; when N is odd, M = (N+1) / 2. Each of the M-1 groups consists of two photovoltaic strings connected in parallel, and the remaining group consists of one photovoltaic string. The switching device includes M+1 layers of switches (one first-layer switch and M second-layer switches). The M+1 layers of switches are linked, meaning they close or open simultaneously. The first pole of each of the N photovoltaic strings is connected to the input of the DC / DC converter circuit through a first-layer switch; the second pole of each of the N photovoltaic strings is connected to the input of the DC / DC converter circuit through M layers of switches.

[0104] The connection method in the above embodiments can ensure that when a reverse connection or short circuit fault occurs in the photovoltaic string, the photovoltaic string will not be subjected to excessive reverse current after the switching device is disconnected, thereby ensuring the safety of the photovoltaic string. At the same time, it can save the number of layer switches, thereby reducing the size and cost.

[0105] For further reference, please see below. Figure 5 , Figure 5 This is a schematic diagram illustrating the connection relationship between a switching device 400 and a photovoltaic string in one embodiment of this application. Figure 5 In the embodiment shown, taking N as 4 as an example, that is, N photovoltaic strings include PV1 to PV4, where S1 is a schematic of the first layer switch, and S2 and S3 are schematics of two second layer switches respectively.

[0106] Understandable, Figure 5In this implementation, the first electrode is the positive electrode of the photovoltaic module, the second electrode is the negative electrode of the photovoltaic module, the first-layer switch S1 is connected to the positive electrodes (first electrodes) of all four photovoltaic strings, and the two second-layer switches S2 and S3 are respectively connected to the negative electrodes (second electrodes) of two of the four photovoltaic strings. Figure 5 As shown, when one of the four photovoltaic strings (e.g., PV4) has a reverse connection or short circuit fault, the controller 600 will control the multilayer switches S1, S2, and S3 in the switching device 400 to disconnect, thereby disconnecting the positive and negative terminals of the four photovoltaic strings from the power conversion circuit and preventing the fault from spreading to other circuits. Continuing with the example of PV4 reverse connection, since PV1- and PV2- are not connected to PV4-, when PV4 is reverse connected, only the current from PV3 flows back into PV4. Therefore, the current flowing back into PV4 is small, and since PV4 can withstand the reverse current of one string, it will not be damaged. This is different from other components. Figure 3 This connection method can ensure the safety of the photovoltaic string and greatly reduce the number of layer switches.

[0107] It should be noted that in this embodiment, the first electrode is not limited to being either positive or negative. That is, N photovoltaic strings can be connected with a common positive electrode or a common negative electrode. For ease of description, the following embodiments use the example of N photovoltaic strings connected with a common positive electrode. When N photovoltaic strings are connected with a common positive electrode, the positive electrodes of the N photovoltaic strings are connected together and then connected to the positive input terminal of the power conversion circuit via a first-layer switch. The negative electrodes of the N photovoltaic strings are each connected to the negative input terminal of the power conversion circuit via corresponding second-layer switches.

[0108] It should be understood that the photovoltaic string reverse connection fault in all embodiments of this application means that at least one photovoltaic string is reverse connected. That is, as long as one photovoltaic string is reverse connected, the connection between N photovoltaic strings and the power conversion circuit needs to be disconnected.

[0109] As can be seen, in this embodiment, the first-layer switch needs to connect to the positive or negative terminals of all N photovoltaic strings, while the second-layer switch only connects to the positive or negative terminals of a portion of the N photovoltaic strings. Therefore, the first-layer switch requires a larger current-carrying capacity than the second-layer switch. Thus, in this embodiment, the current-carrying capacity of the first-layer switch is greater than that of the second-layer switch.

[0110] In traditional implementations, each layer of switches in a multi-layer switch system has the same current-carrying capacity. Therefore, with the increasing number of photovoltaic (PV) strings being connected, the first-layer switch cannot accommodate more PV modules. For example, if the current-carrying capacity of each layer switch is only sufficient to connect a maximum of fewer than N PV modules, it becomes impossible to connect all N PV strings to their positive terminals using only one first-layer switch. This necessitates more first-layer switches, thus increasing the number of layer switches or limiting the number of PV strings that can be connected.

[0111] Therefore, this embodiment of the application increases the current-carrying capacity of the first layer switch, making the current-carrying capacity of the first layer switch greater than that of the second layer switch, so as to ensure the safety of the photovoltaic string and enable that only one first layer switch can connect a certain pole of all N photovoltaic strings, further saving the number of layer switches.

[0112] Figure 5 The example shows a connection relationship where N=4. Further reference is available. Figure 6a and Figure 6b , Figure 6a This is a schematic diagram illustrating the connection relationship between another switching device and a photovoltaic string, provided in an embodiment of this application. Figure 6b This is a schematic diagram illustrating the connection relationship between another switching device and a photovoltaic string, provided in an embodiment of this application. It can be seen that... Figure 6a and Figure 6b The diagrams illustrate the connection relationships of photovoltaic systems with N=6 and N=5, respectively. In these systems, the positive terminals of all N photovoltaic strings are simultaneously connected to the first-level switch S1. Figure 6a In this embodiment, the N photovoltaic strings are divided into three groups, each group consisting of two parallel photovoltaic strings, and the negative terminal of each group corresponds to the second-layer switches S2 to S4. That is, in... Figure 6a In the illustrated embodiment, the current-carrying capacity of the first-layer switch S1 needs to be sufficient to handle the current input of six or more photovoltaic strings, and the current-carrying capacity of the second-layer switches S2-S4 needs to be sufficient to handle the current input of two or more photovoltaic strings. Similarly, in Figure 6b In the illustrated embodiment, the N photovoltaic strings are divided into three groups: two groups consisting of two parallel photovoltaic strings, and one group consisting of one photovoltaic string. The negative terminal of each group corresponds to the second-layer switches S2 to S4. That is, in... Figure 6b In the illustrated embodiment, 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 this embodiment, the first poles of N photovoltaic strings can also be connected to the power conversion circuit through multiple first-layer switches. For example, as the number of N strings increases, connecting the first poles through only one first-layer switch may exceed the current-carrying capacity of that single switch; in this case, multiple first-layer switches can be used for connection. (Reference) Figure 6c , Figure 6c This is a schematic diagram illustrating the connection relationship between another switching device and a photovoltaic string, provided as an embodiment of this application. Figure 6c In the embodiment shown, the first poles of the N photovoltaic strings can be connected to the DC / DC conversion circuit through two first-layer switches S1 and S2, respectively.

[0114] It should be understood that the above embodiments are merely examples, and the embodiments of this application are not limited to the number of photovoltaic strings mentioned above. In practical applications, more photovoltaic strings can be connected. Of course, the embodiments of this application can also support fewer photovoltaic strings.

[0115] Figure 7 This is a schematic diagram illustrating the connection relationship between a switching device 400 and a photovoltaic string, as provided in another embodiment of this application. Figure 7 This diagram illustrates the connection relationship of a photovoltaic system with N=3. In this system, the positive terminals of all N photovoltaic strings are simultaneously connected to the first-level switch S1. Figure 7 In this embodiment, the N photovoltaic strings are divided into two groups of photovoltaic strings. One group includes two photovoltaic strings connected in parallel, and the other group includes one photovoltaic string. The negative terminal of each group of photovoltaic strings corresponds to the second layer switches S2 to S3. Figure 7 In the illustrated embodiment, the current carrying capacity of the first-layer switch S1 can reach the current input of three or more photovoltaic strings, the current carrying capacity of the second-layer switch S2 needs to reach the current input of two or more photovoltaic strings, and the current carrying capacity of the second-layer switch S3 needs to reach the current input of one or more photovoltaic strings.

[0116] It's important to note that fewer photovoltaic (PV) strings connected do not necessarily mean less current input, and therefore do not imply a lower current-carrying capacity for the corresponding layer switches. In reality, this depends on the power output capacity of the PV strings and the overall architecture of the PV system. Figure 7 The current-carrying capacity of the first-layer switch S1 in the illustrated embodiment is not necessarily less than that of the second-layer switch S1. Figures 5-6b 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 higher level, the input current after the first poles of three photovoltaic strings (e.g., PV1+ to PV3+) are combined may be similar to the input current after the first poles of six photovoltaic strings (PV1+ to PV6+) are combined. That is to say, Figure 7 In the embodiment shown, the current-carrying capacity of the first-layer switch S1 may be similar to... Figure 6b The current-carrying capacity of the first-layer switch S1 in the illustrated embodiment is similar.

[0117] In this embodiment, the current-carrying capacity of multiple second-layer switches can be consistent to simplify design. For example, all second-layer switches can be standardized layer switches with consistent current-carrying capacity, supporting the current input of two photovoltaic strings connected in parallel. Even if some second-layer switches only connect to one photovoltaic string, layer switches supporting the current input of two photovoltaic strings connected in parallel can still be used. Of course, the current-carrying capacity of multiple second-layer switches can also be inconsistent. Second-layer switches with corresponding current-carrying capacity can be configured according to each group, which makes product design more flexible. For example, for second-layer switches connecting two photovoltaic modules in parallel, layer switches supporting the current input of two photovoltaic strings connected in parallel are used; for second-layer switches connecting three photovoltaic modules in parallel, layer switches supporting the current input of three photovoltaic strings connected in parallel are used.

[0118] As mentioned above, the embodiments of this application do not limit the second poles of all photovoltaic strings in the N photovoltaic strings to be 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 can be connected in other ways. For example, when there are multiple switching devices, the second poles of some strings can be connected to other switching devices.

[0119] refer to Figure 8a , Figure 8a This diagram illustrates the connection relationship between multiple switching devices and a photovoltaic string, as provided in an embodiment of this application. An example of a possible implementation with N=5 is given, but the connection method and the number of photovoltaic strings are not limited to this. It can be seen that... Figure 6b The illustrated embodiments are basically similar, with the main difference being that in one of the N photovoltaic strings, the second pole (PV5-) of one string is not connected to the DC / DC converter circuit through the second-layer switch of the switching device 400, but rather through the second-layer switch S4' of another switching device 400'. This means that the second-layer switches of other switching devices can be reused to achieve joint control. For example, in one scenario, the second-layer switch S4' of another switching device 400' is only connected to the second pole of one photovoltaic string, such as PV12-, but its current-carrying capacity is sufficient to connect two photovoltaic strings. In this case, PV5- and PV12- can be jointly connected to this second-layer switch S4' of the switching device 400'. This further reduces the number of layer switches in the switching device 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 terminal, the second layer switch S4' of the switching device 400' can be connected to the negative terminal of the same DC / DC converter circuit, just like the second layer switches S2 and S3 of the switching device 400', or it can be connected to the negative terminal of another DC / DC converter circuit. Since multi-channel DC / DC converter circuits generally share a common negative terminal, both connection methods are acceptable.

[0121] Further reference Figure 8b , Figure 8b This is a schematic diagram illustrating another connection relationship between multiple switching devices and photovoltaic strings provided in an embodiment of this application. In this embodiment, the power converter has two switching devices 400 and 400', which are connected between N+M photovoltaic strings and their corresponding DC / DC conversion circuits 200 and 200'. In this embodiment, N is 6, 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~PV6), the switching device 400, and the DC / DC conversion circuit 200 in this embodiment is similar to... Figure 6a Similarly, the connection method between the K photovoltaic strings (PV7~PV12), the switching device 400', and the DC / DC conversion circuit 200' is also the same as... Figure 6a Similarly, the main difference lies in the connection of the second pole of one of the photovoltaic strings across the switching device. For example, PV1- is connected across the switching device; that is, instead of connecting PV1- to the second-level switch S2 of the switching device 400, PV1- is connected to the second-level switch S6' of the switching device 400', and instead of connecting PV7- to the second-level switch S6' of the switching device 400', PV7- is connected to the second-level switch S2 of the switching device 400. It is understandable that this connection method is applicable not only to the case where N and K are equal, but also to the case where they are not equal, for example, N=6 and K=5. Furthermore, this connection method is not only applicable to the case where only one photovoltaic string is connected across the switching device, but also to multiple photovoltaic strings. For example, PV1- and PV2- can both be connected across the switching device 400', or PV1- to PV3- can all be connected across the switching device 400'. This application does not impose any limitations on this.

[0122] The following describes the structural design of a switching device 400 adapted to the above embodiments, which has a multilayer switch with different current carrying capacity.

[0123] refer to Figure 9 and Figure 10 , Figure 9 This is a schematic diagram of the structure of a switching device 400 provided in an embodiment of this application. Figure 10This is an exploded view of a switching device 400 provided in an embodiment of this application. The switching device 400 includes a rotating shaft 101 and multiple layers of switches P1 to Pn stacked along the extending direction O of the rotating shaft 101. P1 is the first layer switch in the above embodiment of this application, and P2, P3, and P4 are the second layer switches in the above embodiment of this application, respectively. (In conjunction with...) Figure 6a In the illustrated embodiment, the positive terminals of all six photovoltaic strings can be connected to P1, and the negative terminals of the six photovoltaic strings can be connected in pairs to P2, P3, and P4 respectively. In this embodiment, the current carrying capacity of P1 is greater than that of P2, P3, and P4. Therefore, along the extension direction O of the rotation axis 101, the layer height h1 of the first layer switch P1 is greater than the layer height h2 / h3 / h4 of the second layer 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 height h2 / h3 / h4 of the second layer switches P2 / P3 / P4. Further, except... Figure 9 In addition to the embodiment shown, in some other possible implementations, 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 length of the second layer switches P2 / P3 / P4, wherein the first direction is perpendicular to the extension direction O of the rotation axis 101.

[0124] It is understood that, in addition to the examples P1 to P4 mentioned above, the switching device 400 of this application embodiment may also include more layers of switches P5 to Pn. These layer switches can all be designed with a similar structure to P1 to P4 to realize the connection of one switching device 400 to more photovoltaic strings and / or multiple DC / DC conversion circuits 200. The following description of this application mainly uses the first or second layer switch of a certain layer as an example, and the structure of the other layer switches will not be described in detail.

[0125] To ensure reliable disconnection of the switches in the switching device 400 when a reverse connection fault occurs in the photovoltaic string, the switching device 400 provided in this application embodiment may further include a tripping device 102. The tripping device 102 may include a transmission mechanism controlled by the controller 600. When a reverse connection fault or short circuit fault exists in the photovoltaic string, or when a short circuit fault occurs at the output terminal of the power conversion circuit, the controller 600 may send a disconnection command to the tripping device 102. The tripping device 102 operates according to the disconnection command, causing all multilayer switches P1 to Pn to disconnect.

[0126] In addition to the tripping device 102 described above, the switching device 400 of this embodiment may also include a knob 103, which is fixed to the rotating shaft 101. Thus, by manually rotating the knob 103, the multi-layer switches P1 to Pn can also be disconnected. That is, the switching device 400 of this embodiment can be automatically disconnected under the control of the controller 600, or it can be manually disconnected under human control.

[0127] The following is combined Figure 10 as well as Figures 11-13 The structure of each layer of switches is described. Figure 11 This is a schematic diagram of the structure of a first-layer switch P1 provided in an embodiment of this application. Figure 12 This is a schematic diagram of the structure of a second-layer switch P2 provided in an embodiment of this application. Figure 13 This is a schematic diagram of another second-layer switch P3 provided in an embodiment of this application. Each layer switch includes a housing and a moving contact and a stationary contact located within the housing. The moving contact rotates relative to the housing, while the stationary contact is fixed relative to the housing. Specifically, the moving contact can be fixed relative to a rotating shaft 101, which drives the moving contact to rotate to separate from or make contact with the stationary contact. When the multilayer switches P1 to Pn are connected, the moving and stationary contacts in the multilayer switches P1 to Pn are all in contact to achieve electrical connection. When the multilayer switches P1 to Pn are disconnected, the moving and stationary contacts in the multilayer switches P1 to Pn are all separated to disconnect the electrical connection.

[0128] Let's take the first-level switch P1 as an example for explanation. Figure 11 In the illustrated embodiment, the first-layer switch P1 includes a housing 11, a first stationary contact 12, a second stationary contact 13, and a moving contact 14. The first stationary contact 12, the second stationary contact 13, and the moving contact 14 are disposed on the housing 11. The moving contact 14 is rotatable relative to the housing, while the first stationary contact 12 and the second stationary contact 13 are fixed relative to the housing 11. The moving contact 14 includes two ends 14A and 14B. The first stationary contact 12 and the second stationary contact 13 can be distributed along the rotation trajectory of the moving contact 14. When the moving contact 14 is rotated by the rotating shaft 101, one end 14A of the moving contact 14 can contact or separate from the first stationary contact 12, and the other end 14B of the moving contact 14 can contact or separate from the second stationary contact 13. For example, currently... Figure 11 The diagram shows a state where one end 14A of the moving contact 14 can contact the first stationary contact 12, and the other end 14B of the moving contact 14 can contact the second stationary contact 13. The first stationary contact 12 is used for electrical connection to the photovoltaic string, and the second stationary contact 13 is used for electrical connection to the power conversion circuit. Specifically, in conjunction with the above embodiment, the first stationary contact 12 of the first layer switch P1 is used to connect to the first pole (e.g., the positive pole) of the N photovoltaic strings, and the second stationary contact 13 of the first layer switch P1 is used to connect to the input terminal of the DC / DC conversion circuit 200.

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

[0130] In some possible implementations, when connecting the power conversion circuit, the switching device 400 can be connected via a cable or directly plugged into a circuit board containing the power conversion circuit for board-side connection. In the case of board-side connection, the second stationary contact 13 may include a pin portion 131 extending out of the housing 11, the pin portion 131 for electrical connection with the circuit board to achieve connection with the power conversion circuit. Figure 11 In the embodiments, the pin portion 131 of the first layer switch P1 includes two pins, namely 131A and 131B. It is understood that in some possible implementations, a wider pin portion 131 may also be provided to accommodate the high current-carrying capacity of the first layer switch P1.

[0131] Furthermore, the first-level switch P1 may also include a first arc-extinguishing chamber 15 and a second arc-extinguishing chamber 16. The first arc-extinguishing chamber 15 and the second arc-extinguishing chamber 16 are arranged on both sides of the moving contact 14 along the rotation trajectory of both ends of the moving contact 14, so as to extinguish the arc between the moving contact 14 and the first stationary contact 12 and the second stationary contact 13 when the moving contact 14 contacts or separates from the first stationary contact 12 and the second stationary contact 13 respectively, thus ensuring the safety of the switching device 400.

[0132] The structure of the second-layer switch P2 and the second-layer switch P3 is explained in detail below. (Combined with...) Figures 9-13 It can be seen that the structure of the second-layer switch P2 and the second-layer switch P3 is largely similar to that of the first-layer switch P1. The main difference lies in the reference... Figure 9 and Figure 10 Because the first-layer switch P1 has a large current-carrying capacity, its connection portion 121 has a larger area, and its pin portion 131 has more or is wider. The second-layer switch has a smaller current-carrying capacity than the first-layer switch, so its connection portion (221, 321, 421) has a smaller area, and its pin portion has fewer or is narrower.

[0133] like 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, while 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 along the rotation trajectory of the moving contact 24. When the moving contact 24 is rotated 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 The diagram shows a 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. The first stationary contact 22 is used for electrical connection to the photovoltaic string, and the second stationary contact 23 is used for electrical connection to the power conversion circuit. Specifically, in conjunction with the above embodiment, the first stationary contact 22 of the first-layer switch P2 is used to connect to the second terminal (e.g., the negative terminal) of a portion of the N photovoltaic strings (e.g., a group of N photovoltaic strings), and the second stationary contact 23 of the first-layer switch P2 is used to connect to the input terminal of the DC / DC conversion circuit 200.

[0134] In some possible implementations, the first stationary contact 22 may include a connecting portion 221 extending out of the housing 21, the connecting portion 221 being used for electrical connection with the photovoltaic string. Specifically, it may be as follows... Figure 12 As shown, fastening and electrical connection are achieved through the connection hole 2210 on the connection part 221 and the connector for connecting the photovoltaic string.

[0135] In the case of upper board connection, the second stationary contact 13 may include a pin portion 231 extending out of the housing 21, the pin portion 231 being used for electrical connection with the circuit board to achieve connection with the power conversion circuit.

[0136] Furthermore, the first-level switch P2 may also 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 arranged on both sides of the moving contact 24 along the rotation trajectory of both 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, thus ensuring the safety of the switching device 400.

[0137] like 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 is rotatable relative to the housing, while 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 along the rotation trajectory of the moving contact 34. When the moving contact 34 is rotated 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 The diagram shows a 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. The first stationary contact 32 is used for electrical connection to the photovoltaic string, and the second stationary contact 33 is used for electrical connection to the power conversion circuit. Specifically, in conjunction with the above embodiment, the first stationary contact 32 of the first-layer switch P3 is used to connect to the second terminal (e.g., the negative terminal) of a portion of the N photovoltaic strings (e.g., another set of N photovoltaic strings), and the second stationary contact 33 of the first-layer switch P3 is used to connect to the input terminal of the DC / DC conversion circuit 200.

[0138] In some possible implementations, the first stationary contact 32 may include a connecting portion 321 extending out of the housing 31, the connecting portion 321 being used for electrical connection with the photovoltaic string. Specifically, it may be as follows... Figure 13 As shown, fastening and electrical connection are achieved through the connection hole 3210 on the connection part 321 and the connector for connecting the photovoltaic string.

[0139] In the case of upper board connection, the second stationary contact 33 may include a pin portion 331 extending out of the housing 31, the pin portion 331 being used for electrical connection with the circuit board to achieve connection with the power conversion circuit.

[0140] Furthermore, the first-layer switch P3 may also include a first arc-extinguishing chamber 35 and a second arc-extinguishing chamber 36. The first arc-extinguishing chamber 35 and the second arc-extinguishing chamber 36 are arranged on both sides of the moving contact 34 along the rotation trajectory of both ends of the moving contact 34, so as to extinguish the arc 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, thus ensuring the safety of the switching device 400.

[0141] The above example illustrates the specific structure of the first-level switch and the second-level switch using a first-level switch P1 and two second-level switches P2 and P3. It should be understood that in the switching device 400, the structures of other first-level switches (e.g., P5) and other second-level switches (e.g., P4) are similar to those of the first-level switch P1 and the two second-level switches P2 and P3, so they will not be described in detail here.

[0142] The following is combined Figure 9 and Figure 14 Further explanation of the structure of the connection and pin sections between each layer of switches. See [link / reference] Figure 9 In this embodiment of the application, the connection portion 121 of the first layer switch P1 and the connection portions 221, 321, 421 of the second layer switches P2 to P4 can be staggered. That is, the connection portion 121 of the first layer switch P1 is disposed at one end of the side wall of the housing, while the connection portions 221, 321, 421 of the second layer switches P2 to P4 are disposed at the other end of the side wall of each housing. This increases the creepage distance between the connection portions connecting the positive and negative terminals, thereby achieving better electrical isolation. Figure 14 For this application Figure 9 This embodiment provides a schematic diagram of a switching device from another angle. Combined with the above, it can be seen that... Figure 14 In the embodiment, the first-layer switch P1 has two pin portions 131A and 131B, and the second-layer switches P2 to P4 each have one pin portion (231, 331, 431). That is, the number of pin portions in the first-layer switch is greater than the number of pin portions in the second-layer switch. Furthermore, the pin portions of each layer of switches can be staggered to increase the creepage distance of each layer's pin portions and improve safety requirements. For example, in... Figure 14 In the illustrated embodiment, the two pin portions 131A and 131B of the first-layer switch P1 extend outward from the middle of the side wall of the housing 11, while the pin portions of the second-layer switches P2 to P4 extend outward from the ends of their respective housing side walls, and the pin portions of adjacent second-layer switches are not at the same end. For example, the pin portion 231 of the second-layer switch P2 is located at one end of the side wall of its housing 21, and the pin portion 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 the above structure is mainly illustrated using one first-level switch P1 and three second-level switches P2 to P5 as an example. When there are more first-level and second-level switches, the arrangement can be such that each first-level switch is separated by at least two second-level switches. For example, P1 and P5 are separated by second-level switches P2 to P4, and the other first-level switches are similarly arranged. The advantage of this arrangement is that the positive and negative terminals of the photovoltaic string can correspond to the positions of the first-level and second-level switches, which facilitates wiring and avoids cable tangling.

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

[0145] refer to Figure 15 and Figure 16 , Figure 15 This is a schematic diagram of another switching device 400 provided in an embodiment of this application. Figure 16 For this application Figure 15 This embodiment provides a schematic diagram of another switching device from another angle. It is understood that... Figure 15 and Figure 16 The embodiments shown are the same as those described above. Figures 9-14 The principle and structure of the switching device 400 in the illustrated embodiment are largely similar, with the main difference being that... Figure 15 and Figure 16 In the illustrated embodiment, multiple first-layer switches are stacked adjacent to each other along the rotation axis, and multiple second-layer switches are stacked adjacent to each other along the rotation axis. Figure 15 As shown, the switching device 400 includes a rotating shaft 101' and multiple layers of switches P1' to Pn' stacked along the extending direction O' of the rotating shaft 101'. P1' to P3' are the first layer switches in the above embodiments of this application, and P5' to Pn' are the second layer switches in the above embodiments of this application. It can be seen that multiple first layer switches are first stacked sequentially, and then multiple second layer switches are stacked sequentially. Further reference... Figure 16 The pin design, in Figure 16 In this embodiment, the first-layer switches P1' to P3' each have two pins, namely 131A' and 131B', 231A' and 231B', and 331A' and 331B', while the second-layer switches P5' to Pn' each have one pin (431', 531', ...). That is, the number of pins in the first-layer switches is greater than the number of pins in the second-layer switches. Furthermore, the pins of the second-layer switches can be staggered to increase the creepage distance of the pins in each layer and improve safety requirements. In this embodiment, by arranging multiple first-layer switches and multiple second-layer switches in a concentrated manner, the risk of short circuits caused by the positive and negative poles being too close together can be better avoided.

[0146] The power supply method of the controller 600 in this embodiment will be further described below.

[0147] See Figure 17 This figure is a schematic diagram of another photovoltaic system provided in an embodiment of this application.

[0148] The controller 600 provided in this application embodiment requires a power supply, therefore, it may include a first power-harvesting circuit 500. The first power-harvesting circuit 500 provided in this application embodiment adopts a competitive power-harvesting method, that is, the first power-harvesting circuit 500 is used to draw power from the group with the highest voltage among the M groups of photovoltaic strings to power the controller 600, and does not need to draw power from each group of photovoltaic strings.

[0149] Figure 17 A method for competitive power extraction is provided, namely, a first power extraction circuit comprising 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 N is 4 photovoltaic strings, according to the connection method of this embodiment and grouped in pairs, there is 1 first-layer switch and 2 second-layer switches. Therefore, the first power extraction circuit comprises 6 diodes and one capacitor.

[0150] In the M+1 layer switches, the first terminal of each layer switch is connected to the first and second terminals of the first capacitor through a forward bias diode and a reverse bias diode, respectively; the first terminal of each layer switch is connected to the corresponding photovoltaic string, and the second terminal of each layer switch is connected to the input terminal of the DC / DC conversion circuit.

[0151] from Figure 17 As can be seen, the switching device includes three layers of switches S1-S3. Each layer of switches corresponds to two diodes. Specifically, the first terminal of the first layer switch S1 is connected to the two ends of the first capacitor C1 via the corresponding forward-biased diode D2 and reverse-biased diode D1. The first terminal of the second layer switch S2 is connected to the two ends of the first capacitor C1 via the corresponding forward-biased diode D4 and reverse-biased diode D3. The first terminal of the third layer switch S3 is connected to the two ends of the first capacitor C1 via the corresponding forward-biased diode D6 and reverse-biased diode D5. PV1+—PV4+ are connected together, i.e., 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, i.e., 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, i.e., 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 example, with reference to the accompanying diagram, illustrates 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. Conversely, 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 all PV1-PV4 are reversed, the voltage of PV1 / PV2 connected in parallel is greater than the voltage of PV3 and PV4 connected in parallel. Therefore, the voltage at point B is higher than the voltage at point C, and the current flows out from PV1 and PV2. Conversely, the current flows out from PV3 and PV4.

[0155] The following describes a specific method for determining reverse connection of photovoltaic strings.

[0156] See Figure 18 This figure is a schematic diagram of another photovoltaic system provided in an embodiment of this application.

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

[0158] The input current detection circuit 700 is used to detect the current in each of the N photovoltaic strings. It should be understood that each photovoltaic string can be connected in series with a current sensor to detect the current in each string. Normally, the current in each photovoltaic string flows in the same direction. If there is a reverse connection, the current in the reversed photovoltaic string will flow in the opposite direction to the other normal photovoltaic strings. Therefore, the current direction can be used to determine if there is a reverse connection. For example, the current is positive under normal conditions, but negative under reverse connection, thus indicating a reverse connection.

[0159] The controller 600 determines, based on the current of each of the N photovoltaic strings, that if the current in any one of the photovoltaic strings is reversed, all multi-layer switches in the control switching device 400 should be disconnected. Specifically, the controller 600 sends a disconnect command to the tripping device, which then activates, causing all three layers of switches S1-S3 to disconnect. If even one photovoltaic string has a reverse connection fault, all photovoltaic strings must be disconnected from the DC / DC converter circuit 200.

[0160] The switching device 400 provided in this application embodiment can not only disconnect when there is a reverse connection fault in the photovoltaic string, thus playing a protective role, but also disconnect when there is a short circuit fault in the photovoltaic string, thus playing a protective role. It will be described in detail below.

[0161] The photovoltaic system provided in this embodiment includes not only an input current detection circuit 700, but may also include an input voltage detection circuit 800.

[0162] The input voltage detection circuit 800 is used to detect the voltage between the first terminal of the first-layer switch S1 and the first terminals of each of the two second-layer switches (S2 and S3). Assuming there are M second-layer switches, M voltages are obtained; that is, the input voltage detection circuit 800 detects the voltage of each of the M photovoltaic strings. If the voltage of any one photovoltaic string is low, there may be a short circuit fault in some of the photovoltaic strings. It should be understood that when a short circuit fault exists, the voltage of the photovoltaic string will drop and the current will increase. To accurately determine a short circuit fault, both voltage and current can be used for judgment. Figure 18 In the input voltage detection circuit 800, it 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] One specific implementation involves a controller 600 that, when at least one of the M voltages is less than a first voltage threshold and the current of at least one of the N photovoltaic strings is greater than a first current threshold, controls all switches on layer M+1 to open. That is, if a short-circuit fault exists in a photovoltaic string, all switches in the switching device 400 will open, thereby isolating the faulty photovoltaic string and protecting the downstream circuitry from the short-circuit fault.

[0164] The above-described embodiments are for detecting short-circuit faults at the input terminal of a DC / DC converter circuit. The following describes short-circuit faults at the output terminal of a DC / DC converter circuit.

[0165] See Figure 19 This figure is a schematic diagram of another photovoltaic system provided in an embodiment of this application.

[0166] This application embodiment can detect not only whether a short circuit fault occurs at the input terminal of the DC / DC converter circuit, but also whether a short circuit fault occurs at the output terminal of the DC / DC converter circuit. When a short circuit fault occurs at the output terminal of the DC / DC converter circuit, in order to prevent the fault range from expanding and to play a protective role, it is also necessary to control all layer switches in the switching device to be disconnected, thereby playing a fault isolation role.

[0167] The photovoltaic system provided in this embodiment also 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 terminal of the first layer switch S1; that is, to detect the input current of the DC / DC converter circuit 200.

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

[0170] To accurately determine whether a short circuit fault has occurred at the output of the DC / DC converter circuit 200, both voltage and current conditions need to be considered. A short circuit fault is determined to have occurred when both conditions are met. Specifically, the controller 600 controls all multi-layer switches to disconnect when the current at the second terminal of the first-layer switch S1 exceeds a second current threshold and the voltage at the output of the DC / DC converter circuit 200 is less than a second preset voltage. Since the first-layer switch S1 connects all photovoltaic strings, the output voltage detection circuit 902 only needs to detect the current flowing through the first-layer switch S1.

[0171] It should be understood that both the input current detection circuit and the output current detection circuit can be implemented using current sensors. When there is a reverse connection in the photovoltaic string, the current in the photovoltaic string is in the opposite direction to the current in the normal photovoltaic string. Therefore, the presence of a reverse connection fault can be determined by detecting the direction of the current. For example, if the current in the normal photovoltaic string is positive, then the current in the reverse-connected photovoltaic string will be negative, i.e., less than zero, indicating a current reversal. Alternatively, the current may be less than a preset threshold, also indicating a reverse connection fault. A current sensor can be installed in each photovoltaic string to detect its current. Furthermore, for example, with four photovoltaic strings, current sensors can be installed in three of them, and a current sensor can be used for the output current. The current in the remaining photovoltaic string can then be obtained by subtracting the sum of the currents in the three photovoltaic strings from the output current, thus reducing the need for one current sensor.

[0172] The photovoltaic system provided in this application embodiment, in order to more comprehensively protect the safe and reliable operation of the photovoltaic system, can not only disconnect all layer switches in the switching device 400 when a reverse connection fault occurs in the photovoltaic string, but also disconnect all layer switches in the switching device 400 when a short circuit fault occurs in the photovoltaic string, and also disconnect all layer switches in the switching device 400 when a short circuit fault occurs at the output terminal of the DC / DC conversion circuit 200, so as to prevent the short circuit fault at the output terminal of the DC / DC conversion circuit 200 from causing damage to the photovoltaic string.

[0173] The above embodiments describe the scenario where power is drawn from the photovoltaic string to supply power to the controller. To ensure that the controller continues to operate when the photovoltaic string is disconnected or has no power output, this application embodiment also includes another power drawing method, which can serve as the main power supply method for the controller. A detailed description is provided below with reference to the accompanying drawings.

[0174] See Figure 20 This figure is a schematic diagram of another photovoltaic system provided in an embodiment of this application.

[0175] Since any hardware may malfunction during operation, 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, to achieve redundant control. When one controller fails, it does not affect the normal control operation. That is, in the photovoltaic system provided in this embodiment, the controller 600 includes: a main controller 600a and a backup controller 600b;

[0176] Both the main controller 600a and the backup controller 600b are used to control the M+1 layer switches to disconnect when a reverse connection fault exists in N photovoltaic strings. That is, in this embodiment, the main controller 600a and the backup controller 600b operate simultaneously. Both controllers can simultaneously receive detection signals from 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. In other words, both controllers can simultaneously receive input voltage, input current, output current, and output voltage, and can use the received signals to determine whether to control all layer switches in the switching device 400 to disconnect. This ensures that if one controller fails and cannot accurately send a disconnect command to the switching device, the other normal controller can accurately and reliably control all layer switches to disconnect.

[0177] In addition, to ensure the reliability of power supply, this application embodiment provides two auxiliary sources, namely: a main auxiliary source 903 and a secondary auxiliary source 904;

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

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

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

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

[0182] The second power supply circuit that provides power to the main auxiliary power source 903 is described below.

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

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

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

[0186] The main auxiliary power source 903 is connected to the positive output terminal of the DC / DC converter circuit 200 via a second power supply circuit. Since the main auxiliary power source 903 is powered by the output terminal of the DC / DC converter circuit 200, and since a typical photovoltaic system includes multiple DC / DC converter circuits with their output terminals connected in parallel, even if all layer switches in the switching device 400 are disconnected, isolating all photovoltaic strings connected to the input terminal of the DC / DC converter circuit 200, the output terminal of the DC / DC converter circuit 200 can still be powered, i.e., it receives power from other parallel DC / DC converter circuits. This ensures the power supply to the main auxiliary power source 903, thereby ensuring the power supply to the controller.

[0187] This application does not limit the specific implementation of the DC / DC conversion circuit in the above photovoltaic systems. For example, it can be a boost circuit with a bypass relay. When the bypass relay is closed, the boost circuit can be bypassed, that is, the boost circuit does not need to be boosted, and the photovoltaic string is directly connected to the subsequent DC / AC conversion circuit through the bypass relay.

[0188] To increase the output power of power conversion equipment, multiple DC / DC conversion circuits are typically connected to the input of a DC / AC conversion circuit.

[0189] See Figure 21 The figure is a schematic diagram of a photovoltaic system including multiple DC / DC conversion circuits provided in an embodiment of this application.

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

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

[0192] The following example illustrates a DC / AC converter circuit whose input is connected to at least two DC / DC converter circuits: a first DC / DC converter circuit 200a and a second DC / DC converter circuit 200b. The inputs of the first DC / DC converter circuit 200a and the second DC / DC converter circuit 200b are connected to their respective photovoltaic arrays; that is, the first DC / DC converter circuit 200a corresponds to photovoltaic array 100a, and the second DC / DC converter circuit 200b corresponds to photovoltaic array 100b. Both photovoltaic arrays 100a and 100b include multiple photovoltaic strings, as detailed in the above embodiments. This embodiment does not provide a detailed illustration of the photovoltaic strings within the photovoltaic arrays. In this embodiment, a switching device 400a is connected between the inputs of photovoltaic array 100a and the first DC / DC converter circuit 200a, and a switching device 400b is connected between the inputs of photovoltaic array 100b and the second DC / DC converter circuit 200b. The functions of the switching devices 400a and 400b are the same as those of the switching devices in the photovoltaic system described in the above embodiments, and will not be repeated here.

[0193] For example, when there is a reverse connection fault in the photovoltaic strings in the photovoltaic array 100a, all switches in the switching device 400a are disconnected, that is, the photovoltaic array 100a stops working and there is no power supply to the input terminal 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 this application embodiment may include a combiner box, i.e. a DC combiner box, in which multiple switching devices and multiple DC / DC conversion circuits are integrated.

[0195] The DC combiner box includes: multiple switching devices and multiple DC / DC conversion circuits; the multiple switching devices and multiple DC / DC conversion circuits correspond one-to-one; the first terminal of each switching device is connected to N photovoltaic strings, and the second terminal of each switching device is connected to the input terminal of the DC / DC conversion circuit; each switching device includes multiple layers of switches, and each group of photovoltaic strings in the N photovoltaic strings is connected to the input terminal of the corresponding power conversion circuit through the same layer of switches in the multiple layers of switches; when there is a reverse connection fault in the N photovoltaic strings, the corresponding multiple layers of switches will all be disconnected in a coordinated manner.

[0196] The following description uses two power conversion circuits as examples, with the DC / DC conversion circuit being used as an example. The working principle and advantages of the photovoltaic system embodiments described above are also applicable to the DC combiner box provided in this embodiment; the same parts will not be repeated here.

[0197] See Figure 22The figure is a schematic diagram of a DC combiner box provided in an embodiment of this application.

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

[0199] The DC combiner box provided in this application includes a switching device, which comprises multiple layers of switches that are linked, meaning they close or open simultaneously. The number of switch layers 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 terminals of the N photovoltaic strings are all connected to the input terminal of the DC / DC conversion circuit through the first layer of switches in the M+1 layers. The M groups of photovoltaic strings are respectively connected to the input terminal of the DC / DC conversion circuit through the M layers of switches in the M+1 layers. When a reverse connection fault exists in any of the N photovoltaic strings, all M+1 layer switches are disconnected. That is, if a reverse connection fault occurs in any one of the photovoltaic strings, all layer switches in the switching device are disconnected.

[0200] In this embodiment, it is not limited whether the first end of the photovoltaic string is a positive or negative layer. That is, N photovoltaic strings can be connected together on a shared positive layer or a shared negative layer. For ease of description, the following embodiments use the connection of N photovoltaic strings on a shared positive layer as an example. When N photovoltaic strings are connected together on a shared positive layer, the positive layers of the N photovoltaic strings are connected together and connected to the positive input terminal of the DC / DC converter circuit through a single layer switch. The negative layers of the N photovoltaic strings are paired up and connected to the negative input terminal of the DC / DC converter circuit through corresponding layer switches. Since the positive layers of the N photovoltaic strings are connected together, the input current of the DC / DC converter circuit can be increased. In addition, since the negative layers of the N photovoltaic strings are paired up, the number of switch layers in the switching device is reduced to a certain extent, thereby reducing the complexity of the hardware structure and reducing costs.

[0201] The embodiments described above are all based on power conversion circuits including DC / DC conversion circuits and DC / AC conversion circuits. The following describes the implementation of a power conversion circuit that only includes a DC / AC conversion circuit, with reference to the accompanying drawings.

[0202] Based on the photovoltaic system provided in the above embodiments, this application also provides a fault isolation method.

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

[0204] The method includes:

[0205] If a reverse connection fault is detected in any of the N photovoltaic strings, all multi-layer switches will be disconnected.

[0206] Determining if a reverse connection fault exists in N photovoltaic strings specifically includes:

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

[0208] If the current in any one of the N photovoltaic strings is reversed based on the current in each photovoltaic string, then a reverse connection fault is determined to exist in the N photovoltaic strings.

[0209] When a photovoltaic (PV) string is reverse-connected, the current in that PV string flows in the opposite direction to the current in a normal PV string. Therefore, the presence of a reverse-connection fault can be determined by detecting the direction of the current. For example, if the current in a normal PV string is positive, the current in the reverse-connected PV string will be negative (less than zero), indicating a reverse current. The current may also be less than a preset threshold, indicating a reverse connection fault. A current sensor can be installed in each PV string to detect the current. Alternatively, for example, with four PV strings, current sensors can be installed in three of them, and a current sensor can be installed in the output current. The current in the remaining PV string can then be obtained by subtracting the sum of the currents in the three PV strings from the output current, thus reducing the need for a separate current sensor.

[0210] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: 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] The above-described 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 skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions 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 input terminal of the power conversion circuit is connected to the switching device; The switching device includes a rotating shaft and multiple layers of switches stacked along the extending direction of the rotating shaft. Each multiple layer of switches includes a first layer of switches and at least two second layer switches. The number of first layer switches is less than the number of second layer switches, and the current-carrying capacity of the first layer switches is greater than that of the second layer switches. The first layer switches are used to simultaneously connect to the first pole of N photovoltaic strings. The N photovoltaic strings are divided into M groups of photovoltaic strings, each group including one photovoltaic string, or two or three photovoltaic strings connected in parallel. Two of the at least two second layer switches are used to connect to the second pole of two groups of photovoltaic strings in the M groups of photovoltaic strings. The first pole is either positive or negative, and the second pole is the opposite pole to the first pole. 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 a short circuit fault in the photovoltaic string, or a short circuit fault at the output terminal of the power conversion circuit, control all the multi-layer switches in the switching device to disconnect the positive and negative terminals of the photovoltaic string from the power conversion circuit, and make up to two or three photovoltaic strings in parallel among the N photovoltaic strings.

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

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

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 in the 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. Each group of photovoltaic strings includes one photovoltaic string, or two or three photovoltaic strings connected in parallel. Two of the at least two second-layer switches are used to connect to the second poles of two photovoltaic strings in 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 connect one-to-one with the second pole of the M sets of photovoltaic strings.

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 odd, each of the M-1 groups of photovoltaic strings includes two photovoltaic strings connected in parallel, and the remaining group of photovoltaic strings includes one photovoltaic string.

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

9. The power conversion device according to claim 1, characterized in that, Each layer of the switching device includes: a housing, a moving contact and at least one stationary contact disposed on the housing, the moving contact rotating relative to the housing; the moving contact being fixed relative to the rotating shaft, the rotating shaft being used to drive the moving contact to rotate so as to separate from or contact the stationary contact; When the multilayer switch is disconnected, the moving contact and the stationary contact in the multilayer switch are separated. When the multi-layer switch is connected, both the moving contact and the stationary contact in the multi-layer switch are in contact.

10. The power conversion device according to claim 9, characterized in that, The at least one stationary contact includes a first stationary contact and a second stationary contact, one end of the moving contact is used to contact or separate from the first stationary contact, and the other end of the moving contact is used to contact or separate from the second stationary contact; The first stationary contact is used for electrical connection with the photovoltaic string, and the second stationary contact is used for electrical connection with the power conversion circuit.

11. The power conversion device according to claim 10, characterized in that, The first stationary contact of any layer switch includes a connecting portion extending out of the housing, the connecting portion being used for electrical connection with the photovoltaic array string; The area of ​​the connection part of the first layer switch is larger than the area of ​​the connection part 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 stationary contact of any layer switch includes a pin portion extending out of the housing, the pin portion being used for electrical connection with the circuit board to connect with the power conversion circuit.

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

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

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

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

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