DC fault isolation circuit, combiner box and power converter

Abstract

The invention discloses a direct current fault isolation circuit, a combiner box and a power converter, and relates to the technical field of direct current convergence. In the direct-current fault isolation circuit, the number of direct-current power supplies connected with any positive electrode switch and the number of direct-current power supplies connected with any negative electrode switch are smaller than two, and therefore the direct-current power supplies are not connected in parallel in pairs; when the direct-current power supplies are reversely connected, after the corresponding switches are disconnected, reverse connection current cannot occur among the direct-current power supplies, so that the reverse connection direct-current power supplies can be directly disconnected from the switches on the two sides of the reverse connection direct-current power supplies, arc discharge cannot be caused, and the risks of personal electric shock and fire disasters can be further reduced. In addition, different DC / DC converters are in cross connection with the DC power supply, so that the use number of switches can be reduced.

Description

Technical Field

[0001] The present application relates to the field of direct current (DC) junction technology, and in particular to a DC fault isolation circuit, a junction box and a power converter. Background Art

[0002] On the DC side of the power converter, multiple DC power supplies are generally provided and connected through corresponding DC switches. In the related art, there is a situation that after the DC switch is disconnected, abnormal current exists between different DC power supplies; at this time, if the connection between one of the DC power supplies and the DC switches connected to both sides of itself is disconnected, the interruption of the abnormal current will cause arcing, thereby creating the risk of electric shock and fire. Summary of the invention

[0003] In view of the above problems, the present application provides a DC fault isolation circuit, a combiner box and a power converter to reduce the risk of electric shock and fire. The specific solution is as follows:

[0004] The first aspect of the present application provides a DC fault isolation circuit, comprising: at least two positive switches and at least two negative switches; wherein:

[0005] The first side of each of the positive switches is respectively connected to different positive input interfaces of the DC fault isolation circuit to respectively connect to the positive electrode of at least one corresponding DC power supply; the second side of each of the positive switches is respectively connected to the corresponding positive output interface of the DC fault isolation circuit to achieve the connection of the DC fault isolation circuit to the positive electrodes of the input ends of at least two DC / DC converters;

[0006] The first side of each of the negative pole switches is respectively connected to different negative pole input interfaces of the DC fault isolation circuit to respectively connect to the negative pole of at least one of the DC power supplies; the second side of each of the negative pole switches is respectively connected to the corresponding negative pole output interface of the DC fault isolation circuit to realize the connection of the DC fault isolation circuit to the negative poles of the input ends of at least two of the DC / DC converters;

[0007] The number of the same DC power sources connected to any of the positive switches and any of the negative switches is less than 2;

[0008] There is at least one of the positive pole switches or the negative pole switches, the number of the DC power supplies connected to it is greater than 1, and there is at least one of the corresponding DC power supplies whose other pole is connected to the switch connected to the corresponding pole of the input end of another DC / DC converter, and the positive and negative poles of the corresponding DC power supplies share switches with different other DC power supplies respectively.

[0009] In a possible implementation, when the DC / DC converter is a common cathode topology, for the positive electrode switch, if the number of the DC power supplies connected to it is greater than 1, the negative electrodes of the corresponding DC power supplies are respectively connected to different negative electrode switches;

[0010] When the DC / DC converter is of a common positive pole topology, for the negative pole switch, if the number of the DC power supplies connected to it is greater than 1, the positive poles of the corresponding DC power supplies are respectively connected to different positive pole switches.

[0011] In a possible implementation, when the first side of the positive switch is connected to one of the DC power supplies, the negative pole of the corresponding DC power supply is connected to the first side of any of the negative switches;

[0012] When the first side of the negative pole switch is connected to one of the DC power sources, the positive pole of the corresponding DC power source is connected to the first side of any of the positive pole switches.

[0013] In a possible implementation, there is at least one switch connected to a number of DC power supplies greater than 1, and the other pole of each DC power supply is connected to a different DC / DC converter through a corresponding switch.

[0014] In a possible implementation, each of the DC power supplies connected to the positive pole of the input end of the DC / DC converter has a negative pole connected to a different negative pole switch; or, each of the DC power supplies connected to the negative pole of the input end of the DC / DC converter has a positive pole connected to a different positive pole switch.

[0015] In a possible implementation, each of the DC power supplies connected to the positive pole of the input end of the DC / DC converter has a negative pole connected to a different negative pole switch; and each of the DC power supplies connected to the negative pole of the input end of the DC / DC converter has a positive pole connected to a different positive pole switch.

[0016] In a possible implementation, when the DC / DC converter is a common cathode topology, the cathodes of the DC power supplies connected to the positive electrodes of the input terminals of the DC / DC converter are respectively connected to different cathode switches;

[0017] When the DC / DC converter is of a common positive pole topology, the positive poles of the DC power supplies connected to the negative poles of the input terminals of the DC / DC converter are respectively connected to different positive pole switches.

[0018] In a possible implementation, when the DC / DC converter is a common cathode topology, when the number of the DC power supplies connected to the cathode switch is greater than 1, the positive electrodes of the corresponding DC power supplies are respectively connected to the positive electrodes of the input terminals of different DC / DC converters through the corresponding positive switches;

[0019] When the DC / DC converter is of a common positive pole topology, when the number of the DC power supplies connected to the positive pole switch is greater than 1, the negative poles of the corresponding DC power supplies are respectively connected to the negative poles of the input terminals of different DC / DC converters through the corresponding negative pole switches.

[0020] In a possible implementation, when the number of the DC / DC converters is M and all of them are common negative pole topologies, M is an integer greater than 1, and there are at least M+1 negative pole switches, wherein a first side of each of the negative pole switches is connected to at least two DC power supplies, and the positive poles of the corresponding DC power supplies are respectively connected to different DC / DC converters;

[0021] When the number of the DC / DC converters is M and all are common positive pole topologies, M is an integer greater than 1, and there are at least M+1 positive pole switches, wherein the first side of each of the positive pole switches is connected to at least two DC power supplies, and the negative poles of the corresponding DC power supplies are respectively connected to different DC / DC converters.

[0022] In a possible implementation, when the DC / DC converter is a common cathode topology, the positive electrode of the input end of the DC / DC converter, which is connected to the negative electrodes of each of the DC power supplies, is respectively connected to different DC / DC converters through corresponding negative electrode switches;

[0023] When the DC / DC converter is of a common positive pole topology, the negative pole of the input end of the DC / DC converter is connected to the positive poles of each of the DC power supplies and is connected to different DC / DC converters through corresponding positive pole switches.

[0024] In a possible implementation, when the DC / DC converter is a common cathode topology, the positive input terminal of the DC / DC converter is connected to the corresponding DC power supply through at least one positive switch;

[0025] When the DC / DC converter is of a common positive pole topology, the negative pole of the input terminal of the DC / DC converter is connected to the corresponding DC power source through at least one negative pole switch.

[0026] In a possible implementation, when the DC / DC converter is a common cathode topology, the second sides of the cathode switches are connected, and after being connected, they are respectively connected to the cathode input terminals of different DC / DC converters;

[0027] When the DC / DC converter is of a common positive pole topology, the second sides of the positive pole switches are connected to each other, and after being connected, they are respectively connected to the positive poles of the input ends of different DC / DC converters.

[0028] In a possible implementation, after the switch is turned off, there is no parallel connection relationship between any two of the DC power supplies.

[0029] In a possible implementation, the switches are grouped and integrated into different linkage switches, or all the switches are integrated into the same linkage switch.

[0030] In a possible implementation, each switch is disconnected and controlled manually or by a controller.

[0031] A second aspect of the present application provides a combiner box, comprising: at least two DC / DC converters and a DC fault isolation circuit as described in the first aspect or any implementation form of the first aspect;

[0032] Each positive input interface of the DC fault isolation circuit serves as a positive input terminal of the combiner box, and is used to connect the positive electrode of the corresponding DC power supply;

[0033] Each negative input interface of the DC fault isolation circuit serves as a negative input terminal of the combiner box, and is used to connect to the negative electrode of the corresponding DC power supply;

[0034] Each positive and negative output interface of the DC fault isolation circuit is connected to the positive and negative input terminals of the corresponding DC / DC converter respectively;

[0035] The output end of the DC / DC converter serves as the output end of the combiner box.

[0036] A third aspect of the present application provides a power converter, comprising: a DC / AC converter, at least two DC / DC converters, and at least one DC fault isolation circuit as described in the first aspect or any implementation form of the first aspect;

[0037] Each positive input interface of the DC fault isolation circuit serves as a positive input terminal of the power converter, and is used to connect the positive electrode of the corresponding DC power supply;

[0038] Each negative input interface of the DC fault isolation circuit serves as a negative input terminal of the power converter, and is used to connect to the negative electrode of the corresponding DC power supply;

[0039] Each positive and negative output interface of the DC fault isolation circuit is connected to the positive and negative input terminals of the corresponding DC / DC converter respectively;

[0040] The output end of the DC / DC converter is connected to the DC side of the DC / AC converter;

[0041] The AC side of the DC / AC converter serves as the output end of the power converter.

[0042] By means of the above technical scheme, the DC fault isolation circuit provided by the present application connects the corresponding poles of multiple DC power supplies through the first side of each positive and negative switch, and connects at least two DC / DC converters through the second side of each positive and negative switch; and the number of the DC power supplies connected to any positive switch and the DC power supplies connected to any negative switch belonging to the same DC power supply is less than 2, so that after the switch is disconnected, there is no parallel connection relationship between the DC power supplies; that is, after the switch is disconnected, no abnormal current will appear between any two DC power supplies, so that any DC power supply and the switches on both sides thereof can be directly disconnected without causing arcing, thereby reducing the risk of electric shock and fire. In addition, there is at least one positive switch or negative switch, the number of DC power supplies connected to it is greater than 1, and there is at least one DC power supply in each corresponding DC power supply, the other pole of which is connected to the switch connected to the corresponding pole of the input terminal of another DC / DC converter, so that the switch that needs to be separately equipped to avoid the parallel connection relationship when the DC power supply and other DC power supplies are connected to the corresponding pole of the same DC / DC converter input terminal can be omitted, and the number of switches used can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and the originals and elements are not necessarily drawn to scale.

[0044] Figure 1 A schematic diagram of a structure of a DC fault isolation circuit provided in an embodiment of the present application;

[0045] Figure 2 Another structural schematic diagram of a DC fault isolation circuit provided in an embodiment of the present application;

[0046] Figure 3 A topological structure diagram of a Boost circuit provided in an embodiment of the present application;

[0047] Figure 4 A topological structure diagram of a high-voltage Boost circuit provided in an embodiment of the present application;

[0048] Figure 5 for Figure 3 A mirror image of the topology shown;

[0049] Figure 6 Another structural schematic diagram of a DC fault isolation circuit provided in an embodiment of the present application;

[0050] Figure 7 Another structural schematic diagram of a DC fault isolation circuit provided in an embodiment of the present application;

[0051] Figure 8 Another structural schematic diagram of a DC fault isolation circuit provided in an embodiment of the present application;

[0052] Fig. 9 Another structural schematic diagram of a DC fault isolation circuit provided in an embodiment of the present application;

[0053] Fig.10 Another structural schematic diagram of a DC fault isolation circuit provided in an embodiment of the present application;

[0054] Fig.11 Another structural schematic diagram of a DC fault isolation circuit provided in an embodiment of the present application;

[0055] Fig.12 Another structural schematic diagram of a DC fault isolation circuit provided in an embodiment of the present application;

[0056] Fig.13 Another structural schematic diagram of a DC fault isolation circuit provided in an embodiment of the present application;

[0057] Fig.14 Another structural schematic diagram of a DC fault isolation circuit provided in an embodiment of the present application;

[0058] Fig.15 A schematic diagram of a structure of a linkage switch provided in an embodiment of the present application;

[0059] Fig.16 A schematic diagram of the structure of a combiner box provided in an embodiment of the present application;

[0060] Fig.17 A schematic diagram of the structure of a photovoltaic inverter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0061] The following describes the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. The terms used in the implementation method section of the present application are only used to explain the specific embodiments of the present application, and are not intended to limit the present application.

[0062] The embodiments of the present application are described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. It is known to ordinary technicians in this field that with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

[0063] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and need not be used to describe a specific order or sequential order. It should be understood that the terms used in this way can be interchangeable under appropriate circumstances, which is only to describe the distinction mode adopted by the objects of the same attributes when describing in the embodiments of the present application. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, so that the process, method, system, product or equipment comprising a series of units need not be limited to those units, but may include other units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0064] The embodiment of the present application provides a DC fault isolation circuit to reduce the risk of electric shock and fire. The specific scheme is as follows:

[0065] See also Figure 1 The DC fault isolation circuit 10 comprises: at least two positive switches ( Figure 1 Two positive switches K1 and K4 are used as examples) and at least two negative switches ( Figure 1 Two negative pole switches K2 and K3 are used as examples for demonstration); where:

[0066] The first side of each positive switch is connected to different positive input interfaces of the DC fault isolation circuit 10 to respectively connect to the positive electrode of at least one corresponding DC power source. In practical applications, the DC power source may refer to a photovoltaic unit, such as a photovoltaic module or a photovoltaic string; the DC power source may also refer to an energy storage unit, such as a battery pack or a battery cluster, etc. This is not limited here and depends on the specific application environment. Figure 1 The photovoltaic unit is used as an example in the following related figures. Figure 1 , the first side of the positive switch K1 is connected to the two positive input interfaces A1 and A2 of the DC fault isolation circuit 10, and the first side of the positive switch K4 is connected to the other two positive input interfaces A3 and A4 of the DC fault isolation circuit 10. Specifically, the first side of the positive switch K1 is connected to the positive electrode PV1+ of the photovoltaic unit PV1 through a positive input interface A1 of the DC fault isolation circuit 10, and is connected to the positive electrode PV2+ of the photovoltaic unit PV2 through another positive input interface A2 of the DC fault isolation circuit 10; the first side of the positive switch K4 is connected to the positive electrode PV4+ of the photovoltaic unit PV4 through a positive input interface A3 of the DC fault isolation circuit 10, and is connected to the positive electrode PV3+ of the photovoltaic unit PV3 through another positive input interface A4 of the DC fault isolation circuit 10.

[0067] The second side of each positive switch is connected to the corresponding positive output interface of the DC fault isolation circuit 10 , so as to realize the connection of the DC fault isolation circuit 10 to the positive input terminals of at least two DC / DC converters 20 . Figure 1 In the example, the number of DC / DC converters 20 is 2, such as DC / DC converter #1 and DC / DC converter #2 shown in the figure. Figure 1 The positive switch K1 in the DC fault isolation circuit 10 has a second side connected to the positive input terminal of the DC / DC converter #1 through a positive output interface B1 of the DC fault isolation circuit 10; Figure 1 The positive switch K4 in the DC fault isolation circuit 10 has a second side connected to the positive input terminal of the DC / DC converter #2 through another positive output interface B2 of the DC fault isolation circuit 10.

[0068] The first side of each negative switch is connected to different negative input interfaces of the DC fault isolation circuit 10 to respectively connect to the negative electrode of at least one corresponding DC power source. Figure 1 In the embodiment, the first side of the negative switch K2 is connected to two negative input interfaces A5 and A6 of the DC fault isolation circuit 10, and the first side of the negative switch K3 is connected to the other two negative input interfaces A7 and A8 of the DC fault isolation circuit 10. Specifically, the first side of the negative switch K2 is connected to the negative electrode PV1- of the photovoltaic unit PV1 through a negative input interface A5 of the DC fault isolation circuit 10, and is connected to the negative electrode PV3- of the photovoltaic unit PV3 through another negative input interface A6 of the DC fault isolation circuit 10; the first side of the negative switch K3 is connected to the negative electrode PV2- of the photovoltaic unit PV2 through a negative input interface A7 of the DC fault isolation circuit 10, and is connected to the negative electrode PV4- of the photovoltaic unit PV4 through another negative input interface A8 of the DC fault isolation circuit 10.

[0069] The second side of each negative switch is connected to the corresponding negative output interface of the DC fault isolation circuit 10, so as to realize the connection of the DC fault isolation circuit 10 to the negative input terminals of at least two DC / DC converters 20. Figure 1 The negative switch K2 in the DC fault isolation circuit 10 has a second side connected to the negative input terminal of the DC / DC converter #1 through a negative output interface B3 of the DC fault isolation circuit 10; Figure 1The negative switch K3 in the DC fault isolation circuit 10 has a second side connected to the negative input terminal of the DC / DC converter #2 through another negative output interface B4 of the DC fault isolation circuit 10. In application scenarios such as photovoltaic or energy storage, the output end of each DC / DC converter 20 is connected in parallel to the DC side of the DC / AC converter 30 through a DC bus (including a positive electrode BUS+ and a negative electrode BUS-), and the AC side of the DC / AC converter 30 can be used to connect to the power grid and / or load.

[0070] Furthermore, the number of the same DC power sources connected to any positive switch and any negative switch is less than 2. Figure 1 As shown in , the positive switch K1 and the negative switch K2 are only connected to one same photovoltaic unit PV1, the positive switch K1 and the negative switch K3 are only connected to one same photovoltaic unit PV2, the positive switch K4 and the negative switch K2 are only connected to one same photovoltaic unit PV3, and the positive switch K4 and the negative switch K3 are only connected to one same photovoltaic unit PV4. This setting ensures that there is no parallel connection between the DC power supplies after the switches are disconnected. In this case, if any DC power supply is reversely connected, that is, its positive pole is connected to the negative switch to which its negative pole should be connected, and its negative pole is connected to the positive switch to which its positive pole should be connected, then the connection between it and the subsequent circuit can be cut off by disconnecting the switches connected on both sides, such as disconnecting multiple switches including the switches connected on both sides or even all switches; moreover, when the corresponding switches are disconnected, since there is no parallel connection relationship between each DC power supply, the reverse-connected DC power supply will not generate reverse current with any other positively connected DC power supply, so that the reverse-connected DC power supply and the switches on both sides can be directly disconnected without causing arcing, thereby reducing the risk of electric shock and fire.

[0071] In addition, when the number of the same DC power source connected to any positive switch and any negative switch is less than 2, the number can be 1 or 0; for example, see Figure 2 The positive switch K4 is connected to the photovoltaic units PV3 and PV4, while the negative switch K2' is connected to the photovoltaic unit PV2. The DC power supplies connected to the two are different, and there is no parallel connection relationship between the DC power supplies, which is also within the protection scope of this application.

[0072] If different DC power supplies are connected in parallel after the switch is disconnected, abnormal current may exist between these DC power supplies. For example, when the DC power supply is reversed, reverse current will exist between the reversed DC power supply and other parallel DC power supplies. When the voltages between different DC power supplies are inconsistent, the DC power supply with a lower voltage will accept the reverse current from other parallel DC power supplies. The following text uses reverse current as an example to illustrate that when a DC power supply is reversed, in order to ensure the safety of the DC power supply, the switches on both sides of the reversed DC power supply or more switches including it can be controlled to be disconnected. However, after the corresponding switch is disconnected, reverse current will exist between the reversed DC power supply and other parallel DC power supplies. At this time, if the connection between the reversed DC power supply and the switches connected to both sides of it is disconnected, arcing will occur due to the interruption of the reverse current, thereby creating the risk of electric shock and fire.

[0073] The DC fault isolation circuit 10 provided in this embodiment is connected to the corresponding poles of multiple DC power supplies through the first side of each positive and negative switch, and is connected to at least two DC / DC converters 20 through the second side of each positive and negative switch; and the number of the same DC power supplies connected to any positive switch and any negative switch is less than 2, so that there is no parallel connection relationship between the DC power supplies after the switches are disconnected; that is, when the switches are disconnected, no abnormal current such as reverse current and reverse injection current will appear between any two DC power supplies, so that the reverse-connected DC power supply or other DC power supplies and the switches on both sides of them can be directly disconnected without causing arcing, thereby reducing the risk of electric shock and fire.

[0074] It is worth mentioning that in order to avoid arcing caused by reverse current disconnection in the existing technical solutions, in the photovoltaic inverter application scenario, you can wait until the light on the photovoltaic site is very low and the current of the photovoltaic unit is less than the limit value, and then disconnect the connection between the reverse photovoltaic unit and the switches on both sides of it; however, this will result in the inability to perform maintenance in time when a reverse fault occurs on site, thereby causing a loss of power generation.

[0075] In this embodiment, since there is no parallel connection relationship between the DC power supplies after the switch is disconnected, when a reverse connection fault occurs, after the corresponding switch is disconnected, the connection between the reverse-connected DC power supply and the switches connected on both sides can be directly disconnected, and then the reverse-connected DC power supply can be connected in the forward direction to achieve maintenance; in the photovoltaic inverter application scenario, there is no need to wait for the light at the photovoltaic site to become smaller, so the loss of power generation can be avoided.

[0076] In addition, in this embodiment, there is also a configuration that: there is at least one positive switch or negative switch, the number of DC power supplies connected to it is greater than 1, and there is at least one DC power supply in each corresponding DC power supply whose other pole is connected to the switch connected to the corresponding pole of the input terminal of another DC / DC converter 20, and the positive and negative poles of the corresponding DC power supply share switches with different other DC power supplies. Figure 1 As shown in, for the positive pole switch K1 connected to the positive pole of the input end of the DC / DC converter #1, the negative pole PV1- of the photovoltaic cell PV1 connected thereto is still connected to the DC / DC converter #1 through the negative pole switch K2, while the negative pole PV2- of the photovoltaic cell PV2 connected thereto is connected to the negative pole switch K3 connected to the negative pole of the input end of the DC / DC converter #2; for the negative pole switch K2 connected to the negative pole of the input end of the DC / DC converter #1, the positive pole PV1+ of the photovoltaic cell PV1 connected thereto is still connected to the DC / DC converter #1 through the positive pole switch K1, while the positive pole PV3+ of the photovoltaic cell PV3 connected thereto is connected to the positive pole switch K4 connected to the positive pole of the input end of the DC / DC converter #2; for the positive pole switch K4 connected to the positive pole of the input end of the DC / DC converter #2, the negative pole PV4- of the photovoltaic cell PV4 connected thereto is still connected to the DC / DC Converter #2, and the negative pole PV3- of the photovoltaic cell PV3 connected to it is connected to the negative pole switch K2 connected to the negative pole of the input end of the DC / DC converter #1; for the negative pole switch K3 connected to the negative pole of the input end of the DC / DC converter #2, the positive pole PV4+ of the photovoltaic cell PV4 connected to it is still connected to the DC / DC converter #2 through the positive pole switch K4, and the positive pole PV2+ of the photovoltaic cell PV2 connected to it is connected to the positive pole switch K1 connected to the positive pole of the input end of the DC / DC converter #1; under this structure, the positive pole PV2+ of the photovoltaic cell PV2 shares the positive pole switch K1 with the photovoltaic cell PV1, and the negative pole PV2- of the photovoltaic cell PV2 shares the negative pole switch K3 with the photovoltaic cell PV4; the positive pole PV3+ of the photovoltaic cell PV3 shares the positive pole switch K4 with the photovoltaic cell PV4, and the negative pole PV3- of the photovoltaic cell PV3 shares the negative pole switch K2 with the photovoltaic cell PV1.

[0077] That is, for Figure 1As for the structure shown, when the positive pole of the input end of the DC / DC converter #1 is connected to the photovoltaic units PV1 and PV2, and the positive pole of the input end of the DC / DC converter #2 is connected to the photovoltaic units PV3 and PV4, the negative pole of the input end of the DC / DC converter #1 is connected to both the photovoltaic unit PV1 connected to the positive pole of its own input end and the photovoltaic unit PV3 connected to the positive pole of the input end of the other DC / DC converter #2 through the same negative pole switch K2; in addition, the negative pole of the input end of the DC / DC converter #2 is connected to both the photovoltaic unit PV4 connected to the positive pole of its own input end and the photovoltaic unit PV2 connected to the positive pole of the input end of the other DC / DC converter #1 through the same negative pole switch K3.

[0078] The above arrangement enables cross-connection of DC power supplies between different DC / DC converters 20, and thus makes it unnecessary for the DC power supply with one pole directly connected due to a shared switch to be equipped with a different switch connected to the same DC / DC converter 20 for the other pole to avoid parallel connection. Instead, parallel connection can be avoided by connecting the corresponding pole switches of different DC / DC converters 20. Therefore, this arrangement can reduce the number of switches used.

[0079] It is worth mentioning that Figure 1 In the figure, the number of DC / DC converters 20 is 2, the number of positive and negative switches is also 2, and the number of DC power supplies connected to each switch is also 2. In actual applications, the number of DC / DC converters 20 can be more, the number of positive and negative switches can also be more and do not need to be equal, the number of DC power supplies connected to each switch can also be more and do not need to be equal, and other optional quantity settings will be shown below, but they are not intended to limit the present application. In actual applications, the number of each device or component can be determined according to actual conditions, as long as there is no parallel connection between the DC power supplies, and there is a cross-connected DC power supply between at least one DC / DC converter 20 and other DC / DC converters 20, it is within the protection scope of the present application.

[0080] For example, see Figure 2 , and Figure 1Compared with the above, a negative switch K2' is added. At this time, for photovoltaic units PV1 and PV2, although their positive poles are connected due to the common positive switch K1, their negative poles are connected to different negative switches K2 and K2', respectively, so the two still do not form a parallel connection relationship; and for photovoltaic units PV3 and PV4, although their positive poles are connected due to the common positive switch K4, their negative poles are connected to different negative switches K2 and K3, respectively, so the two do not form a parallel connection relationship; and, although photovoltaic units PV1 and On the basis of connecting PV2 to the same DC / DC converter #1, it is necessary to equip the photovoltaic unit PV2 with another negative pole switch K2' so that there is no parallel connection relationship between the two. However, the photovoltaic unit PV3 is not equipped with a separate negative pole switch to connect to the same DC / DC converter #2 as the photovoltaic unit PV4. Instead, the negative pole switch K2 connected to the DC / DC converter #1 is used to make the photovoltaic units PV3 and PV4 not form a parallel connection relationship. Therefore, one negative pole switch can still be omitted, which also has the advantage of reducing the number of switches used.

[0081] From another perspective, Figure 2 In the structure shown, only the positive and negative poles of two DC power sources share switches with different other DC power sources, namely: photovoltaic unit PV1 and photovoltaic unit PV3; among them, the positive pole PV1+ of photovoltaic unit PV1 shares the positive pole switch K1 with photovoltaic unit PV2, and the negative pole PV1- of photovoltaic unit PV1 shares the negative pole switch K2 with photovoltaic unit PV3; the positive pole PV3+ of photovoltaic unit PV3 shares the positive pole switch K4 with photovoltaic unit PV4, and the negative pole PV3- of photovoltaic unit PV3 shares the negative pole switch K2 with photovoltaic unit PV1. In order to further reduce the number of switches, it can be adopted Figure 1 The structure shown, that is, the negative pole PV2- of the photovoltaic unit PV2 and the negative pole PV4- of the photovoltaic unit PV4 share the negative pole switch K3; at this time, the photovoltaic unit PV2 and the photovoltaic unit PV4 also meet the situation that the positive and negative poles share switches with different other photovoltaic units respectively: the positive pole PV2+ of the photovoltaic unit PV2 shares the positive pole switch K1 with the photovoltaic unit PV1, and the negative pole PV2- of the photovoltaic unit PV2 shares the negative pole switch K3 with the photovoltaic unit PV4; the positive pole PV4+ of the photovoltaic unit PV4 shares the positive pole switch K4 with the photovoltaic unit PV3, and the negative pole PV4- of the photovoltaic unit PV4 shares the negative pole switch K3 with the photovoltaic unit PV2; furthermore, the Figure 2 The negative pole switch K2' is shown in FIG.

[0082] In practical applications, in order to avoid parallel connection between each DC power supply, for each DC power supply connected at one pole, the other pole can be set to be connected to the same DC / DC converter 20 through the corresponding switch, or the other pole can be set to be connected to the switch for connecting to different DC / DC converters 20; as long as there are two DC power supplies using the latter connection, the switch equipped for the former connection can be reduced; that is, in practical applications, it can be set that: the number of DC power supplies connected to at least one switch is greater than 1, and the other poles of the corresponding DC power supplies are connected to different DC / DC converters 20 through the corresponding switches.

[0083] In one example, in the DC fault isolation circuit 10: for any switch, if the number of DC power sources connected to it is greater than 1, the other poles of the corresponding DC power sources are connected to different DC / DC converters 20 through corresponding switches.

[0084] In practical applications, in the DC fault isolation circuit 10, for each DC power supply connected at one pole, if the number is 2, the other poles are respectively connected to switches for accessing different DC / DC converters 20; and if the number is greater than 2, the other poles can be set to be respectively connected to switches for accessing different DC / DC converters 20 to save as many switches as possible; or, only at least one of them can be set to access another DC / DC converter 20, which can still reduce the corresponding number of switches. That is, for each DC power supply connected at one pole, if the number is greater than 2, the DC / DC converters 20 connected to the other poles can be all different or partially different, all within the protection scope of the present application.

[0085] On the basis of the above-mentioned embodiment, this embodiment gives some detailed descriptions of the structure of the DC fault isolation circuit. For example, the DC / DC converter 20 has a variety of optional topologies, but according to the connection relationship of its internal components, it can be divided into two topologies: common positive pole and common negative pole. For example, Figure 3 The boost circuit shown and Figure 4 The high-voltage Boost circuits shown are all common cathode topologies. As can be seen from the figure, the negative electrode of the input terminal and the negative electrode of the output terminal of this circuit are directly connected inside the circuit, that is, the input terminal and the output terminal of this circuit are connected to the common cathode, so it can be called a common cathode topology; and the topology in which the input terminal and the output terminal are connected to the common positive electrode is a common positive topology, such as Figure 5 As shown, it is Figure 3 Mirror image of the topology shown. Figures 3 to 5 This is only an exemplary description of the optional topology of the DC / DC converter 20 , and other topologies in the prior art are also within the protection scope of this application.

[0086] The structures of the DC fault isolation circuit 10 when the DC / DC converter 20 adopts the above two topologies are respectively described by way of examples:

[0087] When the DC / DC converter 20 is a common cathode topology, for any positive switch in the DC fault isolation circuit 10, if the number of DC power sources connected to it is greater than 1, the negative electrodes of the corresponding DC power sources are connected to different negative switches. Figure 6 Take the case where the number of DC / DC converters 20 is 2, the number of positive switches is 4, the number of negative switches is 2, and each DC / DC converter 20 is connected to 3 photovoltaic units respectively as an example for demonstration; wherein the positive pole of the input end of DC / DC converter #1 is connected to the first photovoltaic unit PV1, the second photovoltaic unit PV2 and the third photovoltaic unit PV3, and the positive pole of the input end of DC / DC converter #2 is connected to the fourth photovoltaic unit PV4, the fifth photovoltaic unit PV5 and the sixth photovoltaic unit PV6. The positive pole PV1+ of the first photovoltaic unit PV1 is connected to the first switch K11, the positive pole PV2+ of the second photovoltaic unit PV2 and the positive pole PV3+ of the third photovoltaic unit PV3 are both connected to the second switch K12, the negative pole PV1- of the first photovoltaic unit PV1 and the negative pole PV2- of the second photovoltaic unit PV2 are both connected to the third switch K13, and the negative pole PV3- of the third photovoltaic unit PV3 is connected to the fourth switch K14. The positive pole PV4+ of the fourth photovoltaic unit PV4 and the positive pole PV5+ of the fifth photovoltaic unit PV5 are both connected to the sixth switch K16, the positive pole PV6+ of the sixth photovoltaic unit PV6 is connected to the fifth switch K15, the negative pole PV4- of the fourth photovoltaic unit PV4 is connected to the third switch K13, and the negative pole PV5- of the fifth photovoltaic unit PV5 and the negative pole PV6- of the sixth photovoltaic unit PV6 are both connected to the fourth switch K14. That is, the second switch K12 connects two photovoltaic cells PV2 and PV3, wherein the negative electrode PV2- of the second photovoltaic cell PV2 is connected to the negative electrode of the input terminal of the DC / DC converter #1 through the third switch K13, and the negative electrode PV3- of the third photovoltaic cell PV3 is connected to the negative electrode of the input terminal of the DC / DC converter #2 through the fourth switch K14; the sixth switch K16 connects two photovoltaic cells PV4 and PV5, wherein the negative electrode PV4- of the fourth photovoltaic cell PV4 is connected to the negative electrode of the input terminal of the DC / DC converter #1 through the third switch K13, and the negative electrode PV5- of the fifth photovoltaic cell PV5 is connected to the negative electrode of the input terminal of the DC / DC converter #2 through the fourth switch K14. Figure 6 In the structure shown, after each switch is disconnected, there is no parallel connection relationship between each photovoltaic unit; when there is a reverse connection of the photovoltaic unit, after the corresponding switch is disconnected, there is no reverse current in each photovoltaic unit, and the connection between the reverse-connected photovoltaic unit and the switches on both sides of it can be directly disconnected, without arcing, and there is no risk of electric shock or fire.

[0088] In addition, when the DC / DC converter 20 is a common cathode topology, when the first side of a positive switch is connected to a DC power source, the negative electrode of the corresponding DC power source is connected to the first side of any negative electrode switch; for example, Figure 6 In the embodiment, the negative electrode PV1- of the first photovoltaic unit PV1 can be connected to the first side of the third switch K13 (such as Figure 6 ), or it can be connected to the first side of the fourth switch K14 (not shown); the negative electrode PV6- of the sixth photovoltaic unit PV6 can be connected to the first side of the fourth switch K14 (as shown in Figure 6 ), and the first side of the third switch K13 may also be connected (not shown).

[0089] In practical applications, in order to reduce the number of switches, each negative electrode of the DC / DC converter 20 can be provided with only one negative electrode switch, that is, if the number of DC / DC converters 20 is M, M is an integer greater than 1, then the number of negative electrode switches is also M, and the second sides of the M negative electrode switches are respectively connected to the negative electrodes of the input terminals of different DC / DC converters 20. At this time, the number of DC power supplies connected to the first side of each positive electrode switch is less than or equal to M; when there are at least two DC power supplies connected to the first side of the positive electrode switch, the negative electrodes of the corresponding DC power supplies are respectively connected to the first sides of different negative electrode switches; Figure 6 That is, the demonstration is carried out using M=2 as an example.

[0090] Figure 7 Another example when M=2 is shown, in which the positive input terminals of DC / DC converter #1 and DC / DC converter #2 are each connected to 6 photovoltaic units, PVj+ represents the positive terminal of the j-th photovoltaic unit, PVj- represents the negative terminal of the j-th photovoltaic unit, and j is any value from 1 to 12; after all switches are disconnected, there is no parallel connection relationship between any two photovoltaic units.

[0091] Figure 8 Another example when M=2 is shown, in which the positive pole of the input end of DC / DC converter #1 is connected to 9 photovoltaic units, and the positive pole of the input end of DC / DC converter #2 is connected to 8 photovoltaic units, PVj+ represents the positive pole of the j-th photovoltaic unit, PVj- represents the negative pole of the j-th photovoltaic unit, and j is any value from 1 to 17; after all switches are disconnected, there is no parallel connection relationship between each photovoltaic unit.

[0092] When the DC / DC converter 20 is in a common positive pole topology, for any negative pole switch, if the number of DC power sources connected to it is greater than 1, the positive poles of the corresponding DC power sources are connected to different positive pole switches. Fig. 9Take the case where the number of DC / DC converters 20 is 2, the number of positive switches is 2, the number of negative switches is 4, and each DC / DC converter 20 is connected to 3 photovoltaic units respectively as an example for demonstration; wherein the negative pole of the input end of DC / DC converter #1 is connected to the first photovoltaic unit PV1, the second photovoltaic unit PV2 and the third photovoltaic unit PV3, and the negative pole of the input end of DC / DC converter #2 is connected to the fourth photovoltaic unit PV4, the fifth photovoltaic unit PV5 and the sixth photovoltaic unit PV6. The negative pole PV1- of the first photovoltaic unit PV1 is connected to the first switch K21, the negative pole PV2- of the second photovoltaic unit PV2 and the negative pole PV3- of the third photovoltaic unit PV3 are connected to the second switch K22, the positive pole PV1+ of the first photovoltaic unit PV1 and the positive pole PV2+ of the second photovoltaic unit PV2 are connected to the third switch K23, and the positive pole PV3+ of the third photovoltaic unit PV3 is connected to the fourth switch K24. The negative pole PV4- of the fourth photovoltaic unit PV4 and the negative pole PV5- of the fifth photovoltaic unit PV5 are connected to the sixth switch K26, the negative pole PV6- of the sixth photovoltaic unit PV6 is connected to the fifth switch K25, the positive pole PV4+ of the fourth photovoltaic unit PV4 is connected to the third switch K23, the positive pole PV5+ of the fifth photovoltaic unit PV5 and the positive pole PV6+ of the sixth photovoltaic unit PV6 are connected to the fourth switch K24. That is, the second switch K22 connects two photovoltaic cells PV2 and PV3, wherein the positive pole PV2+ of the second photovoltaic cell PV2 is connected to the positive pole of the input terminal of the DC / DC converter #1 through the third switch K23, and the positive pole PV3+ of the third photovoltaic cell PV3 is connected to the positive pole of the input terminal of the DC / DC converter #2 through the fourth switch K24; the sixth switch K26 connects two photovoltaic cells PV4 and PV5, wherein the positive pole PV4+ of the fourth photovoltaic cell PV4 is connected to the positive pole of the input terminal of the DC / DC converter #1 through the third switch K23, and the positive pole PV5+ of the fifth photovoltaic cell PV5 is connected to the positive pole of the input terminal of the DC / DC converter #2 through the fourth switch K24. Fig. 9 In the structure shown, after each switch is disconnected, there is no parallel connection relationship between each photovoltaic unit; when there is a reverse connection of the photovoltaic unit, after the corresponding switch is disconnected, there is no reverse current in each photovoltaic unit, and the connection between the reverse-connected photovoltaic unit and the switches on both sides of it can be directly disconnected, without arcing, and there is no risk of electric shock or fire.

[0093] In addition, when the DC / DC converter 20 is a common positive pole topology, when there is a first side of a negative pole switch connected to a DC power source, the positive pole of the corresponding DC power source is connected to the first side of any positive pole switch; for example, Fig. 9 In the embodiment, the positive electrode PV1+ of the first photovoltaic unit PV1 can be connected to the first side of the third switch K23 (such as Fig. 9), or it can be connected to the first side of the fourth switch K24 (not shown); the positive electrode PV6+ of the sixth photovoltaic unit PV6 can be connected to the first side of the fourth switch K24 (as shown in Fig. 9 ), and the first side of the third switch K23 may also be connected (not shown).

[0094] In practical applications, in order to reduce the number of switches, if the number of DC / DC converters 20 is M, the number of positive switches can be set to M, and the second sides of the M positive switches are respectively connected to the positive input terminals of different DC / DC converters 20; the number of DC power supplies connected to the first side of each negative switch is less than or equal to M; when the first side of a negative switch is connected to at least two DC power supplies, the positive poles of the corresponding DC power supplies are respectively connected to the first sides of different positive switches. Fig. 9 That is, the demonstration is performed using M=2 as an example; when M=2, the case where the number of switches and / or the number of photovoltaic units is greater is no longer demonstrated separately, and the principle is the same as that of the common negative pole topology.

[0095] in addition, Figures 6 to 9 This is only a partial display based on M=2. When M=2, the number of switches and / or photovoltaic units can be greater, so no further display is given. Furthermore, the value of M can also be greater than 2. The situation when M>2 can be inferred from the above description and no further display is given.

[0096] In practical applications, if there is no cross-connection of DC power between a DC / DC converter and other DC / DC converters, then when a reverse-connected DC power appears in the DC power supplies connected to the DC / DC converter, after the corresponding switch is disconnected, the reverse-connected DC power may form a series connection relationship with other DC power supplies at its two poles due to the shared switch, thereby causing it to form a branch connected in series with the DC power supplies connected to its two poles; the two switches at both ends of the branch will withstand three times the DC power supply voltage, which places very high requirements on the voltage design of the switch.

[0097] To solve the above problem, in this embodiment, the following settings are made for each DC power supply connected to the same DC / DC converter: when the positive or negative poles of the two DC power supplies are not connected to the same switch, their opposite poles are also connected to different switches; in this case, if a DC power supply reverse connection fault occurs, even if the corresponding reverse-connected DC power supply is connected in series with other DC power supplies, there will only be at most two DC power supplies in the series-connected branch, so the switches on both sides of the series branch can withstand at most twice the DC power supply voltage.

[0098] That is, on the basis of the above embodiment, it can be set that: the negative poles of each DC power supply connected to the positive pole of the input end of the DC / DC converter 20 are connected to different negative pole switches; or, the positive poles of each DC power supply connected to the negative pole of the input end of the DC / DC converter 20 are connected to different positive pole switches. In other words, there is a situation that: for a DC / DC converter 20, regardless of whether there is a connection point between the corresponding poles of each DC power supply connected to the positive pole or negative pole of its input end, the opposite poles of these DC power supplies are connected to different switches. If a DC power supply reverse connection fault occurs, after the corresponding reverse-connected DC power supply is connected in series with other DC power supplies, the switches on both sides can withstand at most twice the DC power supply voltage.

[0099] by Figure 6 The structure shown in the figure is used as an example to illustrate that at this time, the three photovoltaic units PV1 to PV3 connected to the positive pole of the input end of the DC / DC converter #1 are required to be connected to different negative pole switches respectively, see Fig.10 , you can Figure 6 On the basis of the structure shown, a negative pole switch K13' is added to the first photovoltaic unit PV1, so that it and the other two photovoltaic units PV2 and PV3 are respectively connected to different negative pole switches, so that when a photovoltaic unit reverse connection fault occurs, each switch can withstand a maximum of 2 times the DC power supply voltage; similarly, a negative pole switch K14' can be added to the sixth photovoltaic unit PV6, so that it and the other two photovoltaic units PV4 and PV5 are respectively connected to different negative pole switches. Fig.10 In the structure shown, any pole of the input end of the DC / DC converter 20, the other pole of each DC power source connected thereto is connected to a different switch. That is, in practical applications, it can also be arranged that: the negative poles of each DC power source connected to the positive pole of the input end of the DC / DC converter 20 are connected to different negative pole switches; and the positive poles of each DC power source connected to the negative pole of the input end of the DC / DC converter 20 are connected to different positive pole switches.

[0100] for Fig.10 The two negative switches K13' and K14' added in Fig.10 As shown in , the second side thereof is respectively connected to the DC / DC converter 20 connected to the positive pole of each corresponding photovoltaic unit; or, the second side thereof can also be respectively connected to another DC / DC converter 20, for example, the second side of the negative pole switch K13' can also be connected Fig.10 The negative input terminal of the DC / DC converter #2 is shown in FIG. ; no limitation is made here. Fig.10The connection relationship shown in is only an optional example. As long as there is no parallel connection relationship between each DC power supply and there is a cross-connected DC power supply between different DC / DC converters 20, it is set that there is a pole in the input end of each DC / DC converter 20, and the other pole connected to each DC power supply is connected to different switches respectively, so that each switch can withstand a maximum of twice the DC power supply voltage when a DC power supply reverse connection fault occurs.

[0101] Specifically, when the DC / DC converter 20 is of a common cathode topology, for any DC / DC converter 20 , the negative electrodes of the DC power sources to which the positive electrodes of the input terminals thereof are connected are respectively connected to different cathode switches. Figures 11 to 13 Taking the number of DC / DC converters 20 M=2 as an example, different structures of the DC fault isolation circuit 10 are shown; Figures 11 to 13 In the equation, PVj+ represents the positive electrode of the j-th photovoltaic unit, PVj- represents the negative electrode of the j-th photovoltaic unit, and j is Fig.11 is any value between 1 and 10, j is Fig.12 and Fig.13 Any value between 1 and 12.

[0102] Under this setting, when the number of DC power sources connected to any negative switch is greater than 1, the positive poles of the corresponding DC power sources are connected to the positive poles of the input terminals of different DC / DC converters 20 through the corresponding positive switches. Fig.11 In the example, K41, K42, K49 and K410 are positive switches, and K43 to K48 are negative switches; Fig.11 As shown in , the negative pole switches K44 to K47 correspond to two connected photovoltaic units respectively, and their positive poles are connected to DC / DC converter #1 and DC / DC converter #2 respectively. Fig.12 In the example, K51, K52, K59 and K510 are positive switches, and K53 to K58 are negative switches; Fig.12 As shown in , the negative pole switches K53 to K58 correspond to two connected photovoltaic units respectively, and their positive poles are connected to DC / DC converter #1 and DC / DC converter #2 respectively. Fig.13 In the example, K61 and K68 are positive switches, and K62 to K67 are negative switches; Fig.13 As shown in , the negative pole switches K62 to K67 correspond to two connected photovoltaic units respectively, and their positive poles are connected to DC / DC converter #1 and DC / DC converter #2 respectively. That is, when the negative poles of the DC power sources are connected, their positive poles are no longer connected and are connected to different DC / DC converters 20 respectively. This not only ensures that there is no parallel connection between the DC power sources, but also maximizes the number of DC / DC converters 20 with cross-connected DC power sources.

[0103] In practical applications, in order to reduce the number of switches, as described in the above embodiments, the number of DC / DC converters with cross-connected DC power supplies can be increased as much as possible. For example, it can be configured that the negative poles of the DC power supplies connected to the positive poles of the input terminals of the DC / DC converters 20 are respectively connected to the negative pole switches connected to the negative poles of the input terminals of different DC / DC converters 20. For example, Fig.10 If a DC / DC converter #3 is added, the negative pole PV1- of the first photovoltaic unit PV1 may not need to add the negative pole switch K13', but can be connected to the negative pole switch of the DC / DC converter #3, and thus the negative pole switch K13' can be omitted.

[0104] Alternatively, the DC power supplies of different DC / DC converters 20 may be cross-connected as many times as possible; for example, Fig.10 In the structure shown in FIG. 1 , the negative electrode PV1- of the first photovoltaic unit PV1 and the negative electrode PV6- of the sixth photovoltaic unit can also share the same negative electrode switch, that is, Fig.10 The negative switches K13' and K14' in Fig.14 The negative pole switch K134' shown in FIG. 1 can further reduce the number of switches.

[0105] That is, assuming that the number of DC / DC converters 20 is M, where M is an integer greater than 1, at least M+1 negative pole switches may be provided, each of which has a first side connected to at least two positive poles connected to a DC power source of different DC / DC converters 20; for example Fig.11 For any one of the negative pole switches K44 to K47 shown in the figure, the positive poles of the DC power supplies connected to the first side thereof are respectively connected to different DC / DC converters 20, namely DC / DC converter #1 and DC / DC converter #2. In this case, M DC / DC converters 20 can share at least M+1 negative pole switches, and the more the number of shared negative pole switches is, the more the number of negative pole switches that can be reduced is.

[0106] In one example, the first sides of all negative switches may be respectively connected to at least two positive DC power supplies connected to different DC / DC converters 20; for example Fig.12 Negative switches K53 to K58 in, or Fig.13 The negative pole switches K62 to K67 in the embodiment, wherein the positive poles of the DC power sources connected to the first side of each negative pole switch are respectively connected to different DC / DC converters 20, namely DC / DC converter #1 and DC / DC converter #2.

[0107] That is, in Figure 6 On the basis of Fig.10The structure shown can make each switch withstand up to 2 times the DC power supply voltage when a DC power supply reverse connection fault occurs. Fig.14 This further reduces the number of switches used. Fig.11 The negative switches K43 and K48 in the circuit can also be combined into one, and can also be used in Fig.11 On the basis of this, one more negative switch is added.

[0108] In addition, since the negative poles of the output terminals of each DC / DC converter 20 are connected to the negative pole BUS- of the DC bus, the negative poles of the input terminals of each DC / DC converter 20 can also be connected under the common negative pole topology; that is, the second sides of the negative pole switches are connected, and the equipoints after the second sides of the negative pole switches are connected are respectively connected to the negative poles of the input terminals of different DC / DC converters 20. Fig.11 As shown in , the second sides of the negative switches K43 to K48 are connected, and the voltage at any position after the connection is equal, which can be called an equipoint; that is, the negative input terminal of each DC / DC converter 20 can be connected to any position after the negative switches K43 to K48 are connected, as long as the second side of each negative switch K43 to K48 is connected to the negative input terminals of the two DC / DC converters. Fig.12 As shown in , the second side of each negative switch K53 to K58 and the negative input terminals of the two DC / DC converters are connected. Fig.13 As shown in , the second side of each negative switch K62 to K67 and the negative input terminals of the two DC / DC converters are connected. With this connection relationship, the corresponding ports of each device involved can be connected nearby, which is convenient for wiring.

[0109] Furthermore, under the above settings, the positive pole of the input terminal of any DC / DC converter 20 can be connected to the corresponding DC power supplies through at least one positive switch. For each DC power supply connected to the positive pole of the input terminal of each DC / DC converter 20, since their negative poles will be connected to different negative switches respectively, even if there are connection points at their positive poles, they will not be connected in parallel with each other; at this time, the positive pole of the input terminal of the DC / DC converter 20 only needs to have one positive pole switch to ensure that the positive pole disconnection function can be realized; of course, the positive pole of the input terminal of the DC / DC converter 20 can also be provided with two or more positive pole switches, which can be determined according to the number of DC power supplies it is connected to, and is not limited here. Fig.11 , Fig.12 and Fig.14 As shown in , the positive input terminal of each DC / DC converter 20 is connected to two positive switches respectively; Fig.13 As shown in FIG. 1 , the positive input terminal of each DC / DC converter 20 is respectively connected to a positive switch.

[0110] Figures 11 to 14 The different structures of the DC fault isolation circuit 10 are shown by taking the number M=2 of DC / DC converters 20 as an example. The number of switches and the number of photovoltaic units can also use other values ​​and are not shown one by one. The situation when M>2 can be deduced by analogy and is not shown again.

[0111] Similarly, when the DC / DC converter 20 is a common positive pole topology, its principle is the same as the above content, that is, it can also be set that: the positive poles of the DC power supplies connected to the negative poles of the input end of each DC / DC converter 20 are respectively connected to different positive pole switches. Under this setting, when the number of DC power supplies connected to the positive pole switches is greater than 1, the negative poles of the corresponding DC power supplies are respectively connected to the negative poles of the input ends of different DC / DC converters 20 through the corresponding negative pole switches. Further, in order to further reduce the number of switches, it can be set that: when the number of DC / DC converters 20 is M, there are at least M+1 positive pole switches, each of which has a first side connected to at least two DC power supplies with negative poles connected to different DC / DC converters 20; it can also be set that: the positive poles of the DC power supplies connected to the negative poles of the input end of the DC / DC converter 20 are respectively connected to different DC / DC converters 20 through corresponding positive pole switches. In addition, the second sides of the positive pole switches are connected, and the equipotential points after connection are respectively connected to the positive poles of the input ends of different DC / DC converters 20. Furthermore, the negative input terminal of any DC / DC converter 20 is connected to the corresponding DC power source through at least one negative switch.

[0112] This embodiment can not only avoid the parallel connection relationship between the DC power supplies to avoid the reverse current, but also avoid the problem that two switches bear 3 times the DC power supply voltage after the switches are disconnected; in addition, the number of DC / DC converters with cross-connected DC power supplies can be increased as much as possible, or the number of cross-connected DC power supplies between different DC / DC converters 20 can be increased as much as possible, so as to share more switches, thereby further reducing the number of switches.

[0113] On the basis of the above embodiments, this embodiment provides some examples of implementation forms of the switches in the DC fault isolation circuit 10, such as:

[0114] The switches in the DC fault isolation circuit 10 can be grouped and integrated into different linkage switches; a group of switches set in the same linkage switch will act at the same time, that is, they will maintain the same open and break state. The number of linkage switches used in the DC fault isolation circuit 10 and how the switches are grouped can be determined according to actual application requirements and are not limited here.

[0115] Alternatively, all switches in the DC fault isolation circuit 10 may be integrated into the same linkage switch, thereby saving the structural cost of the DC fault isolation circuit 10 .

[0116] In addition, in practical applications, each switch in the DC fault isolation circuit 10 can be disconnected and controlled manually, or can be disconnected and controlled by a controller. The controller can be a controller in the device where the DC fault isolation circuit 10 is located. For example, when the DC fault isolation circuit 10 is applied to a photovoltaic inverter, the controller can be a controller in the photovoltaic inverter; when the DC fault isolation circuit 10 is applied to an energy storage converter, the controller can be a controller in the energy storage converter; or, the controller can also refer to other controllers such as a host computer, which is not limited here.

[0117] The above linkage switch can be a rotary DC switch, see Fig.15 , the knob 103, the connecting rod 102 and the P-stage linkage switch 101 are arranged along the first direction, wherein the knob 103 is connected to the connecting rod 102 and can be used to drive the connecting rod 102 to rotate; the connecting rod 102 is used to connect the knob 103 and the P-stage linkage switch 101. The P-stage linkage switch 101 includes a first-stage switch 111, a second-stage switch 112, ..., and a P-stage switch 11P, where P is an integer greater than or equal to 1; each stage switch can be used as a switch described in the above embodiment, and two pins are arranged on it to realize the connection of the DC power supply and the DC / DC converter 20 on both sides thereof; specifically, one pin can be arranged to connect the positive or negative pole of the DC power supply, and another pin can be arranged to connect the corresponding pole of the input end of the DC / DC converter 20. The P switches are stacked along the first direction, and when the connecting rod 102 rotates, the P switches are linked to close or disconnect, so as to realize the connection or disconnection between the DC power supply and the DC / DC converter.

[0118] In practical applications, the linkage switch may also use other structures. Fig.15 This is only an optional example and is not limited thereto. In addition, solutions in which each switch is independent of each other are also within the protection scope of this application.

[0119] Another embodiment of the present application further provides a combiner box, see Fig.16 , comprising: at least two DC / DC converters 20 (such as DC / DC converter #1 to DC / DC converter #M as shown in the figure) and a DC fault isolation circuit 10 as described in any of the above embodiments; wherein:

[0120] Each positive input interface of the DC fault isolation circuit 10 is used as the corresponding positive input terminal of the combiner box, and is used to connect the positive electrode of the corresponding DC power supply; each negative input interface of the DC fault isolation circuit 10 is used as the corresponding negative input terminal of the combiner box, and is used to connect the negative electrode of the corresponding DC power supply. As described in the above embodiment, the DC power supply can refer to a photovoltaic unit or an energy storage unit, which is not limited here. Fig.16 The photovoltaic units (PV1 to PVN1, ..., and PV1 to PVN as shown in the figure) M Any one of them) is used as an example to demonstrate; Fig.16 In the above equation, PVj+ represents the positive pole of the j-th photovoltaic unit, PVj- represents the negative pole of the j-th photovoltaic unit, and j is less than or equal to N1 to N M The positive and negative output interfaces of the DC fault isolation circuit 10 are respectively connected to the positive and negative input terminals of the corresponding DC / DC converter 20. The DC fault isolation circuit 10 is connected to each DC power source (PV1 to PVN1, ..., PV1 to PVN1 shown in the figure) M ) and the connection relationship between each DC / DC converter 20, as well as the working principle of the DC fault isolation circuit 10, can be found in the above embodiments, which will not be described in detail here.

[0121] The output end of the DC / DC converter 20 serves as the output end of the combiner box and can be connected to a power grid and / or a load through a DC / AC converter.

[0122] In practical applications, the DC / DC converter 20 has a variety of optional topologies; for example, when the DC power supply is a photovoltaic unit, the DC / DC converter 20 can use a Boost circuit, a Buck circuit, a Buck-Boost circuit, etc.; and when the DC power supply is an energy storage unit, the DC / DC converter 20 can use a bidirectional Buck-Boost circuit, a bidirectional Boost-Buck circuit, a bidirectional Cuk circuit, a bidirectional Sepic-Zeta circuit, a bidirectional two-bridge arm Buck-Boost circuit, a three-phase staggered parallel DC-DC conversion topology, a phase-shifted full-bridge topology, a full-bridge isolated voltage source topology, a full-bridge isolated current source topology, etc.; the specific structure of each circuit can refer to the prior art, and will not be repeated here. The topology selection of the DC / DC converter 20 depends on its specific application environment, and is within the protection scope of this application.

[0123] The junction box provided in this embodiment can avoid the existence of a parallel connection relationship between DC power supplies after the switch is disconnected by adopting the DC fault isolation circuit 10 described in the above embodiment. Furthermore, when the DC power supply is reversely connected, there will be no reverse current after the switch is disconnected. The connection between the reverse DC power supply and the switches on both sides can be directly disconnected, and arcing will not be generated, and there is no risk of electric shock and fire. Moreover, by cross-connecting DC power supplies between different DC / DC converters, the number of switches used can be reduced. In addition, by allocating the positive and negative poles of each DC power supply connected to each DC / DC converter 20, the situation where two switches bear 3 times the DC power supply voltage can be avoided. Furthermore, the corresponding switch is shared at the negative pole of the input end or the positive pole of the input end of the DC / DC converter 20, which can further reduce the number of switches.

[0124] Another embodiment of the present application further provides a power converter, see Fig.17 , comprising: a DC / AC converter 30, at least two DC / DC converters 20 (such as DC / DC converter #1 to DC / DC converter #M as shown in the figure) and at least one DC fault isolation circuit 10 as described in any of the above embodiments; wherein:

[0125] Each positive input interface of the DC fault isolation circuit 10 serves as the corresponding positive input terminal of the power converter, and is used to connect the positive electrode of the corresponding DC power supply; each negative input interface of the DC fault isolation circuit 10 serves as the corresponding negative input terminal of the power converter, and is used to connect the negative electrode of the corresponding DC power supply. As described in the above embodiment, the DC power supply can refer to a photovoltaic unit or an energy storage unit, which is not limited here. Fig.17 The photovoltaic units (PV1 to PVN1, ..., and PV1 to PVN as shown in the figure) M Any one of them) is used as an example to demonstrate; Fig.17 In the above equation, PVj+ represents the positive pole of the j-th photovoltaic unit, PVj- represents the negative pole of the j-th photovoltaic unit, and j is less than or equal to N1 to N M When the DC power source is a photovoltaic unit, the power converter is a photovoltaic inverter (such as Fig.17 ); when the DC power supply is an energy storage unit, the power converter is an energy storage converter (not shown in the figure).

[0126] The positive and negative output interfaces of the DC fault isolation circuit 10 are respectively connected to the positive and negative input terminals of the corresponding DC / DC converter 20. The DC fault isolation circuit 10 is connected to each DC power source (PV1 to PVN1, ..., PV1 to PVN1 shown in the figure) M) and the connection relationship between each DC / DC converter 20, as well as the working principle of the DC fault isolation circuit 10, can be found in the above embodiments, which will not be described in detail here.

[0127] The output end of each DC / DC converter 20 is connected to the DC side of the DC / AC converter 30; the AC side of the DC / AC converter 30 serves as the output end of the power converter and can be used to connect to the power grid and / or the load.

[0128] Figure 1 , Figure 2 , Figures 6 to 14 In the figure, the DC side of the DC / AC converter 30 is connected to two DC / DC converters 20 as an example for demonstration, except that the number of switches in the DC fault isolation circuit 10 is different, or the connection method of each DC / DC converter 20 and the switch in the DC fault isolation circuit 10 is different; in actual application, the number of each device in the power converter and the number of DC power supplies connected to it can be determined according to the application environment, and the specific connection structure can also have various forms, which are no longer shown one by one.

[0129] As described in the above embodiments, the DC / DC converter 20 has multiple optional topologies, which will not be described here. When the DC / DC converter 20 is a common negative pole topology, the negative poles of the input and output terminals of each DC / DC converter 20 are connected, and the power converter can be called a common negative pole converter; when the DC / DC converter 20 is a common positive pole topology, the positive poles of the input and output terminals of each DC / DC converter 20 are connected, and the power converter can be called a common positive pole converter.

[0130] In addition, the DC / AC converter 30 may also have a variety of optional topologies, such as an H-bridge inverter topology, a three-phase neutral point clamped inverter topology, etc., which are not limited here and can be determined according to the specific application environment.

[0131] When a fault occurs in the system where the power converter is located, some or all switches in the DC fault isolation circuit 10 can be disconnected manually or by a controller to achieve fault isolation between the DC power supply and the power converter. Possible faults in the system include, but are not limited to: reverse connection of the DC power supply, short circuit of the DC power supply, short circuit of the DC / DC converter 20, and short circuit of the DC / AC converter 30.

[0132] The power converter provided in this embodiment can avoid the parallel connection relationship of the DC power supply after the switch is disconnected. When the DC power supply is reversely connected, after the corresponding switch is disconnected, there is no reverse current in each DC power supply, and the connection between the reverse DC power supply and the switches on both sides thereof can be directly disconnected, and arcing will not be generated, and there is no risk of electric shock and fire. When a DC power supply reverse connection failure occurs on site, timely maintenance can be carried out to avoid power generation loss. Moreover, by cross-connecting DC power supplies between different DC / DC converters, the number of switches used can also be reduced. In addition, by allocating the positive and negative poles of each DC power supply connected to each DC / DC converter 20, it is also possible to avoid the situation where two switches bear 3 times the DC power supply voltage, so that each switch can bear 2 times the DC power supply voltage at most. Furthermore, the corresponding switch is shared at the negative pole of the input end or the positive pole of the input end of the DC / DC converter 20, which can further reduce the number of switches.

[0133] It is worth noting that the naming of the input and output ends of each device in this application is only to distinguish between the two sides, and does not limit the direction of its power transmission. For example, when the DC power supply is an energy storage unit, its discharge process will cause the electric energy to be transmitted to the power grid and / or load through the corresponding DC / DC converter 20 and the DC / AC converter 30 in sequence, or to be transmitted to the DC bus through the corresponding DC / DC converter 20 and then supply power to the DC load; and its charging process will cause the electric energy to be charged from the power grid through the DC / AC converter 30 and the corresponding DC / DC converter 20 in reverse, or to be charged from other power sources through the DC bus through the corresponding DC / DC converter 20 in reverse.

[0134] The same and similar parts between the various embodiments in this specification can refer to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment. The system and system embodiments described above are only schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative work.

[0135] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0136] For the above description of the disclosed embodiments, the features described in the embodiments in this specification may be replaced or combined with each other, so that professionals in the field can implement or use the present application. Various modifications to these embodiments will be obvious to professionals in the field, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A DC fault isolation circuit, characterized in that: include: At least two positive switches and at least two negative switches; wherein, The first side of each of the positive switches is respectively connected to different positive input interfaces of the DC fault isolation circuit to respectively connect to the positive electrode of at least one corresponding DC power supply; the second side of each of the positive switches is respectively connected to the corresponding positive output interface of the DC fault isolation circuit to achieve the connection of the DC fault isolation circuit to the positive electrodes of the input ends of at least two DC / DC converters; The first side of each of the negative pole switches is respectively connected to different negative pole input interfaces of the DC fault isolation circuit to respectively connect to the negative pole of at least one of the DC power supplies; the second side of each of the negative pole switches is respectively connected to the corresponding negative pole output interface of the DC fault isolation circuit to realize the connection of the DC fault isolation circuit to the negative poles of the input ends of at least two of the DC / DC converters; The number of the same DC power sources connected to any of the positive switches and any of the negative switches is less than 2; There is at least one of the positive pole switches or the negative pole switches, the number of the DC power supplies connected to it is greater than 1, and there is at least one of the corresponding DC power supplies whose other pole is connected to the switch connected to the corresponding pole of the input end of another DC / DC converter, and the positive and negative poles of the corresponding DC power supplies share switches with different other DC power supplies respectively.

2. The DC fault isolation circuit according to claim 1, characterized in that: When the DC / DC converter is of a common negative pole topology, for the positive pole switch, if the number of the DC power supplies connected to it is greater than 1, the negative poles of the corresponding DC power supplies are respectively connected to different negative pole switches; When the DC / DC converter is of a common positive pole topology, for the negative pole switch, if the number of the DC power supplies connected to it is greater than 1, the positive poles of the corresponding DC power supplies are respectively connected to different positive pole switches.

3. The DC fault isolation circuit according to claim 1, characterized in that: When the first side of the positive switch is connected to one of the DC power supplies, the negative pole of the corresponding DC power supply is connected to the first side of any of the negative switches; When the first side of the negative pole switch is connected to one of the DC power sources, the positive pole of the corresponding DC power source is connected to the first side of any of the positive pole switches.

4. The DC fault isolation circuit according to claim 1, characterized in that: There is at least one switch connected to a number of DC power supplies greater than 1, and the other poles of the corresponding DC power supplies are connected to different DC / DC converters through corresponding switches.

5. The DC fault isolation circuit according to claim 1, characterized in that: The negative poles of the DC power supplies connected to the positive pole of the input end of the DC / DC converter are respectively connected to different negative pole switches; or, the positive poles of the DC power supplies connected to the negative pole of the input end of the DC / DC converter are respectively connected to different positive pole switches.

6. The DC fault isolation circuit according to claim 1, characterized in that: The negative poles of the DC power supplies connected to the positive pole of the input end of the DC / DC converter are respectively connected to different negative pole switches; and the positive poles of the DC power supplies connected to the negative pole of the input end of the DC / DC converter are respectively connected to different positive pole switches.

7. The DC fault isolation circuit according to claim 1, characterized in that: When the DC / DC converter is of a common cathode topology, the cathodes of the DC power supplies connected to the positive electrodes of the input terminals of the DC / DC converter are respectively connected to different cathode switches; When the DC / DC converter is of a common positive pole topology, the positive poles of the DC power supplies connected to the negative poles of the input terminals of the DC / DC converter are respectively connected to different positive pole switches.

8. The DC fault isolation circuit according to claim 7, characterized in that: When the DC / DC converter is of a common cathode topology, when the number of the DC power supplies connected to the cathode switch is greater than 1, the positive electrodes of the corresponding DC power supplies are connected to the positive electrodes of the input terminals of different DC / DC converters through the corresponding positive switches; When the DC / DC converter is of a common positive pole topology, when the number of the DC power supplies connected to the positive pole switch is greater than 1, the negative poles of the corresponding DC power supplies are respectively connected to the negative poles of the input terminals of different DC / DC converters through the corresponding negative pole switches.

9. The DC fault isolation circuit according to claim 7, characterized in that: When the number of the DC / DC converters is M and all of them are of a common negative pole topology, M is an integer greater than 1, and there are at least M+1 negative pole switches, wherein the first side of each of the negative pole switches is connected to at least two DC power supplies, and the positive poles of the corresponding DC power supplies are respectively connected to different DC / DC converters; When the number of the DC / DC converters is M and all are common positive pole topologies, M is an integer greater than 1, and there are at least M+1 positive pole switches, wherein the first side of each of the positive pole switches is connected to at least two DC power supplies, and the negative poles of the corresponding DC power supplies are respectively connected to different DC / DC converters.

10. The DC fault isolation circuit according to claim 7, characterized in that: When the DC / DC converter is of a common cathode topology, the positive electrode of the input end of the DC / DC converter, which is connected to the negative electrodes of each of the DC power supplies, is respectively connected to different DC / DC converters through the corresponding negative electrode switches; When the DC / DC converter is of a common positive pole topology, the negative pole of the input end of the DC / DC converter is connected to the positive poles of each of the DC power supplies and is connected to different DC / DC converters through corresponding positive pole switches.

11. The DC fault isolation circuit according to claim 7, characterized in that: When the DC / DC converter is of a common cathode topology, the positive input terminal of the DC / DC converter is connected to the corresponding DC power supply through at least one positive switch; When the DC / DC converter is of a common positive pole topology, the negative pole of the input terminal of the DC / DC converter is connected to the corresponding DC power source through at least one negative pole switch.

12. The DC fault isolation circuit according to claim 7, characterized in that: When the DC / DC converter is of a common cathode topology, the second sides of the cathode switches are connected to each other, and after being connected, they are respectively connected to the cathode of the input end of different DC / DC converters; When the DC / DC converter is of a common positive pole topology, the second sides of the positive pole switches are connected to each other, and after being connected, they are respectively connected to the positive poles of the input ends of different DC / DC converters.

13. The DC fault isolation circuit according to any one of claims 1 to 12, characterized in that: After the switch is turned off, there is no parallel connection relationship between any two of the DC power supplies.

14. The DC fault isolation circuit according to any one of claims 1 to 12, characterized in that: The switches are grouped and integrated into different linkage switches, or all the switches are integrated into the same linkage switch.

15. The DC fault isolation circuit according to any one of claims 1 to 12, characterized in that: Each switch is disconnected and controlled manually or by a controller.

16. A combiner box, characterized in that: include: At least two DC / DC converters and a DC fault isolation circuit as claimed in any one of claims 1 to 15; Each positive input interface of the DC fault isolation circuit serves as a positive input terminal of the combiner box, and is used to connect the positive electrode of the corresponding DC power supply; Each negative input interface of the DC fault isolation circuit serves as a negative input terminal of the combiner box, and is used to connect to the negative electrode of the corresponding DC power supply; Each positive and negative output interface of the DC fault isolation circuit is connected to the positive and negative input terminals of the corresponding DC / DC converter respectively; The output end of the DC / DC converter serves as the output end of the combiner box.

17. A power converter, characterized in that: include: A DC / AC converter, at least two DC / DC converters and at least one DC fault isolation circuit according to any one of claims 1 to 15; Each positive input interface of the DC fault isolation circuit serves as a positive input terminal of the power converter, and is used to connect the positive electrode of the corresponding DC power supply; Each negative input interface of the DC fault isolation circuit serves as a negative input terminal of the power converter, and is used to connect to the negative electrode of the corresponding DC power supply; Each positive and negative output interface of the DC fault isolation circuit is connected to the positive and negative input terminals of the corresponding DC / DC converter respectively; The output end of the DC / DC converter is connected to the DC side of the DC / AC converter; The AC side of the DC / AC converter serves as the output end of the power converter.

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