Direct current fault isolation circuit, combiner box, and power converter

Abstract

The present application relates to the technical field of direct current (DC) combining, and discloses a DC fault isolation circuit, a combiner box, and a power converter. In the DC fault isolation circuit, among DC power sources connected to any positive-pole switch and DC power sources connected to any negative-pole switch, the number of DC power sources connected to both switches is less than two, so that no parallel connection exists between any two DC power sources; when any DC power source is connected in reverse, and corresponding switches are opened, no reverse currents will be generated between the DC power sources, so that the DC power source connected in reverse can be directly disconnected from the switches connected to both sides thereof without causing arcing, thereby reducing the risk of electric shock to persons and fire. In addition, by cross-connecting DC power sources between different DC / DC converters, the number of switches used can be reduced.

Description

DC fault isolation circuit, combiner box and power converter

[0001] This application claims priority to Chinese Patent Application No. 202411709790.0, filed on November 26, 2024, entitled "DC Fault Isolation Circuit, Combiner Box and Power Converter", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of DC combiner technology, and in particular to a DC fault isolation circuit, combiner box and power converter. Background Technology

[0003] On the DC side of a power converter, multiple DC power supplies are typically connected via corresponding DC switches. A situation exists where, after a DC switch is opened, abnormal currents can exist between the different DC power supplies. If the connection between one of these DC power supplies and its corresponding DC switches is disconnected, the interruption of these abnormal currents can cause arcing, potentially leading to electric shock and fire. Summary of the Invention

[0004] In view of the above problems, this 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:

[0005] The first aspect of this application provides a DC fault isolation circuit, comprising: at least two positive switches and at least two negative switches; wherein...

[0006] The first side of each positive switch is connected to a different positive input interface of the DC fault isolation circuit to connect to the positive terminal of at least one DC power supply; the second side of each positive switch is connected to the corresponding positive output interface of the DC fault isolation circuit to realize the connection of the DC fault isolation circuit to the positive input terminals of at least two DC / DC converters.

[0007] The first side of each negative switch is connected to a different negative input interface of the DC fault isolation circuit to connect to the negative terminal of at least one DC power supply; the second side of each negative switch is connected to the corresponding negative output interface of the DC fault isolation circuit to realize the connection of the DC fault isolation circuit to the negative input terminals of at least two DC / DC converters.

[0008] The number of DC power supplies connected to any of the positive switches and the DC power supplies connected to any of the negative switches that belong to the same DC power supply is less than 2.

[0009] There is at least one positive switch or the negative switch connected to a DC power supply greater than 1, and at least one of the DC power supplies has its other pole connected to a switch connected to the corresponding pole of the input terminal of another DC / DC converter. The positive and negative poles of the corresponding DC power supplies share a switch with different other DC power supplies.

[0010] In one possible implementation, when the DC / DC converter is a common negative topology, for the positive switch, if the number of DC power supplies connected to it is greater than 1, then the negative terminals of each DC power supply are respectively connected to different negative switches.

[0011] When the DC / DC converter is a common positive topology, for the negative switch, if the number of DC power supplies connected to it is greater than 1, then the positive terminals of each DC power supply are respectively connected to different positive switches.

[0012] In one possible implementation, when the first side of the positive switch is connected to a DC power supply, the negative terminal of the corresponding DC power supply is connected to the first side of any negative switch.

[0013] When a DC power supply is connected to the first side of the negative switch, the positive terminal of the corresponding DC power supply is connected to the first side of any positive switch.

[0014] In one possible implementation, there is at least one switch connected to more than one DC power supply, and the other pole of each DC power supply is connected to a different DC / DC converter through a corresponding switch.

[0015] In one possible implementation, the negative terminals of each DC power supply connected to the positive terminal of the DC / DC converter are respectively connected to different negative switches; or, the positive terminals of each DC power supply connected to the negative terminal of the DC / DC converter are respectively connected to different positive switches.

[0016] In one possible implementation, the negative terminals of each DC power supply connected to the positive terminal of the DC / DC converter are respectively connected to different negative switches; and the positive terminals of each DC power supply connected to the negative terminal of the DC / DC converter are respectively connected to different positive switches.

[0017] In one possible implementation, when the DC / DC converter is a common negative topology, the negative terminals of each DC power supply connected to the positive terminal of the DC / DC converter are respectively connected to different negative switches.

[0018] When the DC / DC converter is in a common positive topology, the positive terminals of the DC power supplies connected to the negative terminal of the DC / DC converter are respectively connected to different positive switches.

[0019] In one possible implementation, when the DC / DC converter is a common negative topology, if the number of DC power supplies connected to the negative switch is greater than 1, the positive terminals of each DC power supply are respectively connected to the positive input terminals of different DC / DC converters through the corresponding positive switches.

[0020] When the DC / DC converter is a common positive topology, if the number of DC power supplies connected to the positive switch is greater than 1, the negative terminals of each DC power supply are respectively connected to the negative input terminals of different DC / DC converters through the corresponding negative terminals.

[0021] In one possible implementation, when the number of DC / DC converters is M and all of them are common negative topologies, M is an integer greater than 1, there are at least M+1 negative switches, wherein the first side of each negative switch is connected to at least two DC power supplies, and the positive terminals of each DC power supply are respectively connected to different DC / DC converters.

[0022] When the number of DC / DC converters is M and all of them are common positive topologies, M is an integer greater than 1. There are at least M+1 positive switches, wherein the first side of each positive switch is connected to at least two DC power supplies, and the negative terminals of each DC power supply are respectively connected to different DC / DC converters.

[0023] In one possible implementation, when the DC / DC converter is a common negative topology, the positive terminal of the input terminal of the DC / DC converter and the negative terminal of each DC power supply connected thereto are respectively connected to different DC / DC converters through corresponding negative switches.

[0024] When the DC / DC converter is in a common positive topology, the negative terminal of the input terminal of the DC / DC converter and the positive terminal of each DC power supply connected to it are respectively connected to different DC / DC converters through corresponding positive switches.

[0025] In one possible implementation, when the DC / DC converter is a common negative topology, the positive terminal of the DC / DC converter is connected to each of the corresponding DC power supplies through at least one of the positive switches;

[0026] When the DC / DC converter is in a common positive topology, the negative input terminal of the DC / DC converter is connected to the corresponding DC power supply through at least one negative switch.

[0027] In one possible implementation, when the DC / DC converter is a common negative topology, the second sides of each negative switch are connected, and after being connected, they are respectively connected to the negative input terminals of different DC / DC converters.

[0028] When the DC / DC converter is in a common positive topology, the second sides of each positive switch are connected, and after being connected, they are respectively connected to the positive input terminals of different DC / DC converters.

[0029] In one possible implementation, after the switch is turned off, there is no parallel connection between any of the DC power supplies.

[0030] In one possible implementation, the switches are grouped and integrated into different interlocking switches, or all switches are integrated into the same interlocking switch.

[0031] In one possible implementation, each switch is disconnected manually or via a controller.

[0032] A second aspect of this 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 thereof;

[0033] Each positive input interface of the DC fault isolation circuit serves as the positive input terminal of the combiner box, used to connect to the positive terminal of the corresponding DC power supply.

[0034] Each negative input interface of the DC fault isolation circuit serves as the negative input terminal of the combiner box, and is used to connect to the negative terminal of the corresponding DC power supply.

[0035] Each positive and negative output interface of the DC fault isolation circuit is connected to the corresponding positive and negative input terminals of the DC / DC converter.

[0036] The output terminal of the DC / DC converter serves as the output terminal of the combiner box.

[0037] A third aspect of this 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 thereof.

[0038] Each positive input interface of the DC fault isolation circuit serves as the positive input terminal of the power converter, used to connect to the positive terminal of the corresponding DC power supply.

[0039] Each negative input interface of the DC fault isolation circuit serves as the negative input terminal of the power converter, and is used to connect to the negative terminal of the corresponding DC power supply.

[0040] Each positive and negative output interface of the DC fault isolation circuit is connected to the corresponding positive and negative input terminals of the DC / DC converter.

[0041] The output terminal of the DC / DC converter is connected to the DC side of the DC / AC converter;

[0042] The AC side of the DC / AC converter serves as the output terminal of the power converter.

[0043] By employing the above technical solution, the DC fault isolation circuit provided in this 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. Furthermore, the number of DC power supplies connected to any positive switch and any negative switch that belong to the same DC power supply is less than two. This ensures that there is no parallel connection between any two DC power supplies after the switch is opened. In other words, no abnormal current will occur between any two DC power supplies after the switch is opened, allowing any DC power supply to be directly disconnected from its two adjacent switches without arcing, thereby reducing the risk of electric shock and fire. Additionally, at least one positive or negative switch connects to more than one DC power supply, and at least one of the corresponding DC power supplies has its other pole connected to the corresponding pole of another DC / DC converter input. This eliminates the need for a separate switch to avoid parallel connections when the DC power supply is connected to the same DC / DC converter input pole as other DC power supplies, reducing the number of switches required. Attached Figure Description

[0044] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote 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.

[0045] Figure 1 is a schematic diagram of a DC fault isolation circuit provided in an embodiment of this application;

[0046] Figure 2 is a schematic diagram of another structure of the DC fault isolation circuit provided in the embodiment of this application;

[0047] Figure 3 is a topology diagram of the Boost circuit provided in an embodiment of this application;

[0048] Figure 4 is a topology diagram of the high-voltage Boost circuit provided in an embodiment of this application;

[0049] Figure 5 is a mirror image of the topology shown in Figure 3;

[0050] Figure 6 is a schematic diagram of another structure of the DC fault isolation circuit provided in the embodiment of this application;

[0051] Figure 7 is a schematic diagram of another structure of the DC fault isolation circuit provided in the embodiment of this application;

[0052] Figure 8 is a schematic diagram of another structure of the DC fault isolation circuit provided in the embodiment of this application;

[0053] Figure 9 is a schematic diagram of another structure of the DC fault isolation circuit provided in the embodiment of this application;

[0054] Figure 10 is a schematic diagram of another structure of the DC fault isolation circuit provided in the embodiment of this application;

[0055] Figure 11 is a schematic diagram of another structure of the DC fault isolation circuit provided in the embodiment of this application;

[0056] Figure 12 is a schematic diagram of another structure of the DC fault isolation circuit provided in the embodiment of this application;

[0057] Figure 13 is a schematic diagram of another structure of the DC fault isolation circuit provided in the embodiment of this application;

[0058] Figure 14 is a schematic diagram of another structure of the DC fault isolation circuit provided in the embodiment of this application;

[0059] Figure 15 is a schematic diagram of a linkage switch provided in an embodiment of this application;

[0060] Figure 16 is a schematic diagram of a junction box provided in an embodiment of this application;

[0061] Figure 17 is a schematic diagram of a photovoltaic inverter provided in an embodiment of this application. Detailed Implementation

[0062] The embodiments of this application are described below with reference to the accompanying drawings. The terminology used in the implementation section of this application is for explaining specific embodiments only and is not intended to limit the scope of this application.

[0063] The embodiments of this application are described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Those skilled in the art will understand that with the development of technology and the emergence of new scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.

[0064] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms are interchangeable where appropriate; this is merely a way of distinguishing objects with the same attributes in the embodiments of this application. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of elements is not necessarily limited to those elements, but may include other elements not explicitly listed or inherent to those processes, methods, products, or apparatuses.

[0065] This application provides a DC fault isolation circuit to reduce the risk of electric shock and fire. The specific solution is as follows:

[0066] Referring to Figure 1, the DC fault isolation circuit 10 includes: at least two positive switches (Figure 1 shows two positive switches K1 and K4 as examples) and at least two negative switches (Figure 1 shows two negative switches K2 and K3 as examples); wherein:

[0067] Each positive switch has its first side connected to a different positive input interface of the DC fault isolation circuit 10, respectively, to connect to the positive terminal of at least one DC power source. In practical applications, the DC power source can refer to a photovoltaic unit, such as a photovoltaic module or photovoltaic string; it can also refer to an energy storage unit, such as a battery pack or battery cluster; there is no limitation here, depending on the specific application environment. Figure 1 and the related figures below all use a photovoltaic unit as an example for illustration. Referring to Figure 1, the first side of the positive switch K1 is connected to 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, on the first side of the positive switch K1, the positive terminal PV1+ of the photovoltaic unit PV1 is connected through one positive input interface A1 of the DC fault isolation circuit 10, and the positive terminal PV2+ of the photovoltaic unit PV2 is connected through the other positive input interface A2 of the DC fault isolation circuit 10; on the first side of the positive switch K4, the positive terminal PV4+ of the photovoltaic unit PV4 is connected through one positive input interface A3 of the DC fault isolation circuit 10, and the positive terminal PV3+ of the photovoltaic unit PV3 is connected through the other positive input interface A4 of the DC fault isolation circuit 10.

[0068] The second side of each positive switch is connected to the corresponding positive output interface of the DC fault isolation circuit 10, thereby enabling the DC fault isolation circuit 10 to connect to the positive input terminals of at least two DC / DC converters 20. Figure 1 illustrates an example with two DC / DC converters 20, as shown in Figure 1, namely DC / DC converter #1 and DC / DC converter #2. For instance, for positive switch K1 in Figure 1, its second side is connected to the positive input terminal of DC / DC converter #1 through one positive output interface B1 of the DC fault isolation circuit 10; for positive switch K4 in Figure 1, its second side is connected to the positive input terminal of DC / DC converter #2 through another positive output interface B2 of the DC fault isolation circuit 10.

[0069] Each negative switch has its first side connected to a different negative input interface of the DC fault isolation circuit 10, respectively, to connect to the negative terminal of at least one DC power supply. For example, referring to Figure 1, the first side of 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 negative switch K3 is connected to two other negative input interfaces A7 and A8 of the DC fault isolation circuit 10. Specifically, the first side of negative switch K2 is connected to the negative terminal PV1- of photovoltaic unit PV1 through one negative input interface A5 of the DC fault isolation circuit 10, and to the negative terminal PV3- of photovoltaic unit PV3 through the other negative input interface A6 of the DC fault isolation circuit 10; the first side of negative switch K3 is connected to the negative terminal PV2- of photovoltaic unit PV2 through one negative input interface A7 of the DC fault isolation circuit 10, and to the negative terminal PV4- of photovoltaic unit PV4 through the other negative input interface A8 of the DC fault isolation circuit 10.

[0070] The second side of each negative switch is connected to the corresponding negative output interface of the DC fault isolation circuit 10, thereby enabling the DC fault isolation circuit 10 to connect to the negative input terminals of at least two DC / DC converters 20. For example, for negative switch K2 in Figure 1, its second side is connected to the negative input terminal of DC / DC converter #1 through one negative output interface B3 of the DC fault isolation circuit 10; for negative switch K3 in Figure 1, its second side is connected to the negative input terminal of DC / DC converter #2 through another negative output interface B4 of the DC fault isolation circuit 10. In applications such as photovoltaics or energy storage, the output terminals of each DC / DC converter 20 are connected in parallel to the DC side of DC / AC converter 30 through DC buses (including positive BUS+ and negative BUS-), and the AC side of DC / AC converter 30 can be used to connect to the power grid and / or loads.

[0071] Furthermore, the number of DC power supplies connected to any positive switch and any negative switch that are the same type of DC power supply is less than two. As shown in Figure 1, positive switch K1 and negative switch K2 are connected to only one identical photovoltaic unit PV1, positive switch K1 and negative switch K3 are connected to only one identical photovoltaic unit PV2, positive switch K4 and negative switch K2 are connected to only one identical photovoltaic unit PV3, and positive switch K4 and negative switch K3 are connected to only one identical photovoltaic unit PV4. This configuration ensures that there is no parallel connection between any two DC power supplies after the switches are opened. In this situation, if any DC power supply is reverse-connected, that is, its positive terminal is connected to the negative switch that its negative terminal should be connected to, and its negative terminal is connected to the positive switch that its positive terminal should be connected to, then the connection between it and the subsequent circuit can be cut off by disconnecting the switches connected to both sides of it, such as disconnecting multiple switches or even all switches including the switches connected to both sides of it. Moreover, when the corresponding switches are disconnected, since there is no parallel connection between each pair of DC power supplies, 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 can be directly disconnected from the switches on both sides without causing arcing, thereby reducing the risk of electric shock and fire.

[0072] In addition, when the number of DC power supplies connected to any positive switch and any negative switch that belong to the same DC power supply is less than 2, this number can be 1 or 0; for example, referring to Figure 2, positive switch K4 is connected to photovoltaic units PV3 and PV4, while negative switch K2' is connected to photovoltaic unit PV2. The DC power supplies connected to the two are different, and there is no parallel connection between the DC power supplies. This is also within the scope of protection of this application.

[0073] If different DC power supplies are connected in parallel after the switch is turned off, there may be abnormal currents between these DC power supplies. For example, when a DC power supply is reversed, there will be a reverse current between the reversed DC power supply and other parallel DC power supplies; when the voltages of different DC power supplies are inconsistent, the DC power supply with the lower voltage will receive reverse current from other parallel DC power supplies. The following explanation uses reverse current as an example. When a DC power supply is found to be 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 turned off. However, after the corresponding switches are turned off, there will still be a reverse current 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 its two sides is disconnected, arcing will occur due to the interruption of the reverse current, which will lead to the risk of electric shock and fire.

[0074] The DC fault isolation circuit 10 provided in this embodiment connects to the corresponding poles of multiple DC power supplies through the first side of each positive and negative switch, and connects to at least two DC / DC converters 20 through the second side of each positive and negative switch. Furthermore, the number of DC power supplies connected to any positive switch and any negative switch that belong to the same DC power supply is less than 2. This ensures that there is no parallel connection between any two DC power supplies after the switches are opened. In other words, when the switches are opened, no abnormal current such as reverse connection current or reverse current will occur between any two DC power supplies. This allows the reverse DC power supply or other DC power supplies to be directly disconnected from the switches on both sides without causing arcing, thereby reducing the risk of electric shock and fire.

[0075] It is worth noting that, in order to avoid arcing caused by reverse connection current interruption in existing technical solutions, in photovoltaic inverter application scenarios, the connection between the reverse-connected photovoltaic unit and the switches connected to its two sides can be disconnected when the irradiance at the photovoltaic site is very low and the current of the photovoltaic unit is less than the limit. However, this will result in the inability to carry out timely maintenance when a reverse connection fault occurs on site, thus causing a loss of power generation.

[0076] In this embodiment, since there is no parallel connection between any two DC power supplies after the switch is turned off, when a reverse connection fault occurs, the connection between the reverse DC power supply and the switches connected to its two sides can be directly disconnected after the corresponding switch is turned off, and then the reverse DC power supply can be connected in the forward direction to achieve maintenance. In photovoltaic inverter application scenarios, there is no need to wait for the sunlight at the photovoltaic site to decrease, which can avoid the loss of power generation.

[0077] In addition, this embodiment also includes: there is at least one positive switch or negative switch, the number of DC power supplies connected to it is greater than 1, and at least one of the DC power supplies has its other pole 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 supplies share the same switch with different other DC power supplies. As shown in Figure 1, for the positive switch K1 connected to the positive terminal of the input of DC / DC converter #1, the negative terminal PV1- of the photovoltaic unit PV1 connected to it is still connected to DC / DC converter #1 through negative switch K2, while the negative terminal PV2- of the photovoltaic unit PV2 connected to it is connected to negative switch K3 connected to the negative terminal of the input of DC / DC converter #2; for the negative switch K2 connected to the negative terminal of the input of DC / DC converter #1, the positive terminal PV1+ of the photovoltaic unit PV1 connected to it is still connected to DC / DC converter #1 through positive switch K1, while the positive terminal PV3+ of the photovoltaic unit PV3 connected to it is connected to positive switch K4 connected to the positive terminal of the input of DC / DC converter #2; for the positive switch K4 connected to the positive terminal of the input of DC / DC converter #2, the negative terminal PV4- of the photovoltaic unit PV4 connected to it is still connected to DC / DC converter #1 through negative switch K3. The DC / DC converter #2 is connected to a photovoltaic unit PV3, whose negative terminal PV3- is connected to the negative switch K2 connected to the negative terminal of the input of DC / DC converter #1. For the negative switch K3 connected to the negative terminal of the input of DC / DC converter #2, the positive terminal PV4+ of the photovoltaic unit PV4 is still connected to DC / DC converter #2 via positive switch K4, while the positive terminal PV2+ of the photovoltaic unit PV2 is connected to the positive switch K1 connected to the positive terminal of the input of DC / DC converter #1. In this structure, the positive terminal PV2+ of photovoltaic unit PV2 shares positive switch K1 with photovoltaic unit PV1, while the negative terminal PV2- of photovoltaic unit PV2 shares negative switch K3 with photovoltaic unit PV4; the positive terminal PV3+ of photovoltaic unit PV3 shares positive switch K4 with photovoltaic unit PV4, while the negative terminal PV3- of photovoltaic unit PV3 shares negative switch K2 with photovoltaic unit PV1.

[0078] That is, for the structure shown in Figure 1, when the positive input terminal of DC / DC converter #1 is connected to photovoltaic units PV1 and PV2, and the positive input terminal of DC / DC converter #2 is connected to photovoltaic units PV3 and PV4, the negative input terminal of DC / DC converter #1 is connected to both the photovoltaic unit PV1 connected to its own positive input terminal and the photovoltaic unit PV3 connected to the positive input terminal of another DC / DC converter #2 through the same negative switch K2; in addition, the negative input terminal of DC / DC converter #2 is connected to both the photovoltaic unit PV4 connected to its own positive input terminal and the photovoltaic unit PV2 connected to the positive input terminal of another DC / DC converter #1 through the same negative switch K3.

[0079] The above configuration allows for cross-connection of DC power supplies between different DC / DC converters 20. Consequently, DC power supplies that are directly connected to one pole due to a shared switch do not need to be equipped with different switches connected to the same DC / DC converter 20 to avoid parallel connection. Instead, parallel connection can be avoided by connecting the corresponding pole switches of different DC / DC converters 20. Therefore, this configuration can reduce the number of switches used.

[0080] It is worth noting that Figure 1 illustrates an example with 2 DC / DC converters 20, 2 positive and 2 negative switches, and 2 DC power supplies connected to each switch. In actual applications, the number of DC / DC converters 20 can be more, the number of positive and negative switches can be more and do not need to be equal, and the number of DC power supplies connected to each switch can be more and do not need to be equal. Other optional quantity settings will be shown below, but none of them are intended to limit this application. In actual applications, the number of each device or component can be determined according to the actual situation. As long as there is no parallel connection between any two DC power supplies and there is a cross-connection of DC power supplies between at least one DC / DC converter 20 and other DC / DC converters 20, it is within the scope of protection of this application.

[0081] For example, referring to Figure 2, compared to Figure 1, an additional negative switch K2' is added. In this case, for photovoltaic units PV1 and PV2, although their positive terminals are connected due to sharing the positive switch K1, their negative terminals are connected to different negative switches K2 and K2', therefore they still do not form a parallel connection. Similarly, for photovoltaic units PV3 and PV4, although their positive terminals are connected due to sharing the positive switch K4, their negative terminals are connected to different negative switches K2 and K3, therefore they also do not form a parallel connection. Furthermore, although photovoltaic... Since photovoltaic units PV1 and PV2 are connected to the same DC / DC converter #1, another negative switch K2' is required for photovoltaic unit PV2 to ensure that there is no parallel connection between them. However, photovoltaic unit PV3 is not equipped with a separate negative switch and is connected to the same DC / DC converter #2 as photovoltaic unit PV4. Instead, it uses the negative switch K2 connected to DC / DC converter #1 to ensure that photovoltaic units PV3 and PV4 are not connected in parallel. Therefore, one negative switch can still be omitted, which also has the advantage of reducing the number of switches used.

[0082] From another perspective, for the structure shown in Figure 2, only two DC power supplies share switches with different other DC power supplies: photovoltaic unit PV1 and photovoltaic unit PV3. Specifically, the positive terminal PV1+ of photovoltaic unit PV1 shares positive switch K1 with photovoltaic unit PV2, and the negative terminal PV1- of photovoltaic unit PV1 shares negative switch K2 with photovoltaic unit PV3. The positive terminal PV3+ of photovoltaic unit PV3 shares positive switch K4 with photovoltaic unit PV4, and the negative terminal PV3- of photovoltaic unit PV3 shares negative switch K2 with photovoltaic unit PV1. To further reduce the number of switches, the structure shown in Figure 1 can be adopted, that is, the negative electrode PV2- of photovoltaic unit PV2 and the negative electrode PV4- of photovoltaic unit PV4 share the negative electrode switch K3. In this case, photovoltaic units PV2 and PV4 also meet the condition that the positive and negative electrodes share switches with different other photovoltaic units respectively: the positive electrode PV2+ of photovoltaic unit PV2 shares the positive electrode switch K1 with photovoltaic unit PV1, and the negative electrode PV2- of photovoltaic unit PV2 shares the negative electrode switch K3 with photovoltaic unit PV4; the positive electrode PV4+ of photovoltaic unit PV4 shares the positive electrode switch K4 with photovoltaic unit PV3, and the negative electrode PV4- of photovoltaic unit PV4 shares the negative electrode switch K3 with photovoltaic unit PV2. Therefore, the negative electrode switch K2' shown in Figure 2 can be omitted.

[0083] In practical applications, to avoid parallel connections between DC power supplies, for each DC power supply connected at one pole, its other pole can be connected to the same DC / DC converter 20 via its corresponding switch, or its other pole can be connected to switches for connecting to different DC / DC converters 20. As long as two DC power supplies adopt the latter connection method, one switch required for the former connection method can be eliminated. That is, in practical applications, it can be set such that at least one switch connects to more than one DC power supply, and the other pole of each DC power supply is connected to different DC / DC converters 20 via corresponding switches.

[0084] In one example, within the DC fault isolation circuit 10: for any switch, if the number of DC power supplies connected to it is greater than 1, then the other pole of each DC power supply is connected to a different DC / DC converter 20 through the corresponding switch.

[0085] In practical applications, within this DC fault isolation circuit 10, for each DC power supply connected to one pole, if the number is two, then its other pole is connected to switches for connecting to different DC / DC converters 20. If the number is greater than two, its other pole can be set to connect to switches for connecting to different DC / DC converters 20 to save as many switches as possible. Alternatively, only at least one of them can be connected to another DC / DC converter 20, still reducing the corresponding number of switches. That is, for each DC power supply connected to one pole, if the number is greater than two, the DC / DC converters 20 connected to its other pole can be all different or partially different, all within the scope of protection of this application.

[0086] Based on the above embodiments, this embodiment provides some detailed descriptions of the structure of the DC fault isolation circuit. For example, the DC / DC converter 20 has various optional topologies, but according to the connection relationship of its internal components, it can be divided into two types: common positive and common negative topologies. For example, the Boost circuit shown in Figure 3 and the high-voltage Boost circuit shown in Figure 4 are both common negative topologies. As can be seen from the figures, the negative terminal of the input terminal and the negative terminal 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 with common negative terminals, so it can be called a common negative topology. The topology in which the input terminal and the output terminal are connected with common positive terminals is the common positive topology, such as shown in Figure 5, which is a mirror structure of the topology shown in Figure 3. Figures 3 to 5 are only exemplary illustrations of the optional topologies of the DC / DC converter 20, and other topologies in the prior art are also within the protection scope of this application.

[0087] The following examples illustrate the structure of the DC fault isolation circuit 10 in the two topologies described above for the DC / DC converter 20:

[0088] When the DC / DC converter 20 is in a common negative topology, for any positive switch in the DC fault isolation circuit 10, if the number of DC power supplies connected to it is greater than 1, then the negative terminals of each DC power supply are connected to different negative switches. Figure 6 illustrates an example where there are 2 DC / DC converters 20, 4 positive switches, and 2 negative switches, and each DC / DC converter 20 is connected to 3 photovoltaic units; wherein, the positive input terminal 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 input terminal 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 electrode PV1+ of the first photovoltaic unit PV1 is connected to the first switch K11. The positive electrodes PV2+ of the second photovoltaic unit PV2 and PV3+ of the third photovoltaic unit PV3 are both connected to the second switch K12. The negative electrodes PV1- of the first photovoltaic unit PV1 and PV2- of the second photovoltaic unit PV2 are both connected to the third switch K13. The negative electrode PV3- of the third photovoltaic unit PV3 is connected to the fourth switch K14. The positive electrodes PV4+ of the fourth photovoltaic unit PV4 and PV5+ of the fifth photovoltaic unit PV5 are both connected to the sixth switch K16. The positive electrode PV6+ of the sixth photovoltaic unit PV6 is connected to the fifth switch K15. The negative electrode PV4- of the fourth photovoltaic unit PV4 is connected to the third switch K13. The negative electrodes PV5- of the fifth photovoltaic unit PV5 and PV6- of the sixth photovoltaic unit PV6 are both connected to the fourth switch K14. That is, the second switch K12 connects two photovoltaic units PV2 and PV3. The negative terminal of the second photovoltaic unit PV2 (PV2-) is connected to the negative input terminal of DC / DC converter #1 via the third switch K13, and the negative terminal of the third photovoltaic unit PV3 (PV3-) is connected to the negative input terminal of DC / DC converter #2 via the fourth switch K14. The sixth switch K16 connects two photovoltaic units PV4 and PV5. The negative terminal of the fourth photovoltaic unit PV4 (PV4-) is connected to the negative input terminal of DC / DC converter #1 via the third switch K13, and the negative terminal of the fifth photovoltaic unit PV5 (PV5-) is connected to the negative input terminal of DC / DC converter #2 via the fourth switch K14. For the structure shown in Figure 6, after each switch is disconnected, there is no parallel connection between any two photovoltaic units. When a photovoltaic unit is reverse-connected, after the corresponding switch is disconnected, there is no reverse current in any photovoltaic unit. The connection between the reverse-connected photovoltaic unit and the switches on both sides can be directly disconnected, preventing arcing and eliminating the risk of electric shock and fire.

[0089] In addition, when the DC / DC converter 20 is a common negative topology, if the first side of the positive switch is connected to a DC power supply, the negative terminal of the corresponding DC power supply is connected to the first side of any negative switch. For example, in Figure 6, the negative terminal PV1- of the first photovoltaic unit PV1 can be connected to the first side of the third switch K13 (as shown in Figure 6) or the first side of the fourth switch K14 (not shown); the negative terminal PV6- of the sixth photovoltaic unit PV6 can be connected to the first side of the fourth switch K14 (as shown in Figure 6) or the first side of the third switch K13 (not shown).

[0090] In practical applications, to reduce the number of switches, each DC / DC converter 20 can be equipped with only one negative switch at its negative terminal. That is, if the number of DC / DC converters 20 is M, where M is an integer greater than 1, then the number of negative switches is also M, and the second side of each of the M negative switches is connected to the negative input terminals of different DC / DC converters 20. In this case, the number of DC power supplies connected to the first side of each positive switch is less than or equal to M; when at least two DC power supplies are connected to the first side of a positive switch, the negative terminals of each DC power supply are connected to the first side of a different negative switch. Figure 6 illustrates this with M=2 as an example.

[0091] Figure 7 shows another example when M=2, where the positive 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 turned off, there is no parallel connection between any two photovoltaic units.

[0092] Figure 8 shows another example when M=2, where the positive input terminal of DC / DC converter #1 is connected to 9 photovoltaic units, the positive input terminal of DC / DC converter #2 is connected to 8 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 17; after all switches are turned off, there is no parallel connection between any two photovoltaic units.

[0093] When the DC / DC converter 20 is in a common positive topology, for any negative switch, if the number of DC power supplies connected to it is greater than 1, then the positive terminals of each DC power supply are connected to different positive switches. Figure 9 illustrates this with an example of 2 DC / DC converters 20, 2 positive switches, 4 negative switches, and each DC / DC converter 20 connected to 3 photovoltaic units; where the negative input terminal 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 input terminal 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 electrode PV1- of the first photovoltaic unit PV1 is connected to the first switch K21. The negative electrodes PV2- of the second photovoltaic unit PV2 and PV3- of the third photovoltaic unit PV3 are connected to the second switch K22. The positive electrodes PV1+ of the first photovoltaic unit PV1 and PV2+ of the second photovoltaic unit PV2 are connected to the third switch K23. The positive electrode PV3+ of the third photovoltaic unit PV3 is connected to the fourth switch K24. The negative electrodes PV4- of the fourth photovoltaic unit PV4 and PV5- of the fifth photovoltaic unit PV5 are connected to the sixth switch K26. The negative electrode PV6- of the sixth photovoltaic unit PV6 is connected to the fifth switch K25. The positive electrode PV4+ of the fourth photovoltaic unit PV4 is connected to the third switch K23. The positive electrodes PV5+ of the fifth photovoltaic unit PV5 and PV6+ of the sixth photovoltaic unit PV6 are connected to the fourth switch K24. That is, the second switch K22 connects two photovoltaic units PV2 and PV3. The positive terminal PV2+ of the second photovoltaic unit PV2 is connected to the positive input terminal of DC / DC converter #1 via the third switch K23, and the positive terminal PV3+ of the third photovoltaic unit PV3 is connected to the positive input terminal of DC / DC converter #2 via the fourth switch K24. The sixth switch K26 connects two photovoltaic units PV4 and PV5. The positive terminal PV4+ of the fourth photovoltaic unit PV4 is connected to the positive input terminal of DC / DC converter #1 via the third switch K23, and the positive terminal PV5+ of the fifth photovoltaic unit PV5 is connected to the positive input terminal of DC / DC converter #2 via the fourth switch K24. For the structure shown in Figure 9, after each switch is disconnected, there is no parallel connection between any two photovoltaic units. When a photovoltaic unit is reverse-connected, after the corresponding switch is disconnected, there is no reverse current in any photovoltaic unit. The connection between the reverse-connected photovoltaic unit and the switches on both sides can be directly disconnected, preventing arcing and eliminating the risk of electric shock and fire.

[0094] In addition, when the DC / DC converter 20 is in a common positive topology, if the first side of the negative switch is connected to a DC power supply, the positive terminal of the corresponding DC power supply is connected to the first side of any positive switch. For example, in Figure 9, the positive terminal PV1+ of the first photovoltaic unit PV1 can be connected to the first side of the third switch K23 (as shown in Figure 9) or the first side of the fourth switch K24 (not shown); the positive terminal PV6+ of the sixth photovoltaic unit PV6 can be connected to the first side of the fourth switch K24 (as shown in Figure 9) or the first side of the third switch K23 (not shown).

[0095] In practical applications, to reduce the number of switches, if the number of DC / DC converters 20 is M, the number of positive switches can also be M. The second side of each of the M positive switches is 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 at least two DC power supplies are connected to the first side of a negative switch, the positive terminals of each DC power supply are connected to the first side of a different positive switch. Figure 9 illustrates this with M=2 as an example. Cases with more switches and / or photovoltaic units when M=2 are not shown separately, but the principle is the same as in the common negative topology.

[0096] Furthermore, Figures 6 to 9 only show a partial representation based on M=2. When M=2, the number of switches and / or photovoltaic units can be even greater, but these will not be shown further. Moreover, the value of M can also be greater than 2. The cases where M>2 can be deduced from the above description and will not be shown separately.

[0097] In practical applications, if there is no cross-connection of DC power supply between a DC / DC converter and other DC / DC converters, when a reverse-connected DC power supply appears among the DC power supplies connected to the DC / DC converter, after the corresponding switch is disconnected, the reverse-connected DC power supply may form a series connection with other DC power supplies at its two poles due to sharing a switch. This will result in a series connection branch between the DC power supply and the DC power supply connected to its two poles. The two switches at both ends of this branch will be subjected to three times the DC power supply voltage, which places very high demands on the voltage design of the switches.

[0098] To address the aforementioned issues, this embodiment implements the following configuration for each DC power supply connected to the same DC / DC converter: when the positive or negative terminals of two DC power supplies are not connected to the same switch, their opposite terminals 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 be at most two DC power supplies in the series-connected branch. Therefore, the switches on both sides of the series-connected branch can withstand a maximum of twice the DC power supply voltage.

[0099] That is, based on the above embodiments, it is possible to configure the following: the negative terminals of each DC power supply connected to the positive terminal of the DC / DC converter 20 are connected to different negative switches; or, the positive terminals of each DC power supply connected to the negative terminal of the DC / DC converter 20 are connected to different positive switches. In other words, there exists a situation where, for a DC / DC converter 20, regardless of whether there is a connection point between the corresponding terminals of the DC power supplies connected to its positive or negative terminals, the opposite terminals 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 a maximum of twice the DC power supply voltage.

[0100] Taking the structure shown in Figure 6 as an example, it is required that the three photovoltaic units PV1 to PV3 connected to the positive terminal of the DC / DC converter #1 be connected to different negative switches. Referring to Figure 10, based on the structure shown in Figure 6, a negative switch K13' can be added to the first photovoltaic unit PV1, so that it is connected to different negative switches along with the other two photovoltaic units PV2 and PV3. This ensures that each switch can withstand a maximum of twice the DC power supply voltage in the event of a photovoltaic unit reverse connection fault. Similarly, a negative switch K14' can be added to the sixth photovoltaic unit PV6, so that it is connected to different negative switches along with the other two photovoltaic units PV4 and PV5. For the structure shown in Figure 10, for any terminal of the DC / DC converter 20 input, the other terminal of each DC power supply connected to it is connected to a different switch. In other words, in practical applications, it can also be configured such that the negative terminals of each DC power supply connected to the positive terminal of the DC / DC converter 20 are connected to different negative switches; and the positive terminals of each DC power supply connected to the negative terminal of the DC / DC converter 20 are connected to different positive switches.

[0101] For the two negative switches K13' and K14' added in Figure 10, as shown in Figure 10, their second sides can be connected to the DC / DC converter 20 connected to the positive terminal of their respective photovoltaic units; or, their second sides can also be connected to other DC / DC converters 20, for example, the second side of negative switch K13' can also be connected to the negative input terminal of DC / DC converter #2 shown in Figure 10; there is no limitation here, the connection relationship shown in Figure 10 is only an optional example. As long as there is no parallel connection between each pair of DC power supplies and there is a cross connection between different DC / DC converters 20, and each DC / DC converter 20 has a pole in its input terminal, and the other pole of each DC power supply connected to it is connected to different switches, each switch can withstand a maximum of 2 times the DC power supply voltage when a DC power supply reverse connection fault occurs.

[0102] Specifically, when the DC / DC converter 20 is a common negative topology, for any DC / DC converter 20, the negative terminals of the DC power supplies connected to its positive input terminals are respectively connected to different negative switches. Figures 11 to 13 all illustrate different structures of the DC fault isolation circuit 10 with the number of DC / DC converters M=2 as an example; in Figures 11 to 13, PVj+ represents the positive terminal of the j-th photovoltaic unit, PVj- represents the negative terminal of the j-th photovoltaic unit, j is any value from 1 to 10 in Figure 11, and j is any value from 1 to 12 in Figures 12 and 13.

[0103] In this configuration, when the number of DC power supplies connected to any negative switch is greater than one, the positive terminals of each DC power supply are connected to the positive input terminals of different DC / DC converters 20 via their respective positive switches. In Figure 11, K41, K42, K49, and K410 are all positive switches, and K43 to K48 are all negative switches. As shown in Figure 11, negative switches K44 to K47 each correspond to two photovoltaic units, with their positive terminals connected to DC / DC converter #1 and DC / DC converter #2, respectively. In Figure 12, K51, K52, K59, and K510 are all positive switches, and K53 to K58 are all negative switches. As shown in Figure 12, negative switches K53 to K58 each correspond to two photovoltaic units, with their positive terminals connected to DC / DC converter #1 and DC / DC converter #2, respectively. In Figure 13, K61 and K68 are both positive switches, and K62 to K67 are all negative switches. As shown in Figure 13, each of the negative switches K62 to K67 corresponds to one of the two photovoltaic units connected to it, and their positive terminals are connected to DC / DC converter #1 and DC / DC converter #2, respectively. That is, when the negative terminals of the DC power supplies are connected, their positive terminals are no longer connected and are connected to different DC / DC converters 20. This not only ensures that there is no parallel connection between any two DC power supplies, but also maximizes the number of DC / DC converters 20 that have cross-connected DC power supplies.

[0104] In practical applications, 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 maximized. For example, the negative terminals of the DC power supplies connected to the positive terminals of each DC / DC converter 20 can be connected to the negative terminals of different DC / DC converter 20. For instance, if another DC / DC converter #3 is added in Figure 10, the negative terminal PV1- of the first photovoltaic unit PV1 does not need to have a separate negative terminal switch K13', but can be connected to the negative terminal switch of the DC / DC converter #3, thus eliminating the need for the negative terminal switch K13'.

[0105] Alternatively, the cross-connection of DC power supplies between different DC / DC converters 20 can be maximized; for example, in the structure shown in Figure 10, the negative terminal PV1- of the first photovoltaic unit PV1 and the negative terminal PV6- of the sixth photovoltaic unit can share the same negative terminal switch, that is, the negative terminal switches K13' and K14' in Figure 10 can be combined into a single negative terminal switch K134' as shown in Figure 14, which can further reduce the number of switches.

[0106] That is, assuming the number of DC / DC converters 20 is M, where M is an integer greater than 1, at least M+1 negative switches can be set, each of which has at least two positive terminals connected to the DC power supplies of different DC / DC converters 20 on its first side; for example, any one of the negative switches K44 to K47 shown in Figure 11, whose first side is connected to the positive terminals of the DC power supplies of 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 switches, and the more negative switches shared, the more the number of negative switches can be reduced.

[0107] In one example, all negative switches can be configured such that the first side of each negative switch is connected to at least two positive terminals connected to different DC / DC converters 20; for example, negative switches K53 to K58 in Figure 12, or negative switches K62 to K67 in Figure 13, wherein the positive terminals of the DC power supplies connected to the first side of each negative switch are connected to different DC / DC converters 20, namely DC / DC converter #1 and DC / DC converter #2.

[0108] That is, based on Figure 6, the structure shown in Figure 10 allows each switch to withstand a maximum of twice the DC power supply voltage when a DC power supply reverse connection fault occurs, and Figure 14 further reduces the number of switches used. Similarly, the negative switches K43 and K48 in Figure 11 can be combined into one, and one more negative switch can be removed from the structure shown in Figure 11.

[0109] Furthermore, since the negative output terminals of each DC / DC converter 20 are connected to the negative terminal BUS- of the DC bus, in a common negative topology, the negative input terminals of each DC / DC converter 20 can also be connected. That is, the second sides of each negative switch are connected, and the equidistant points after the second sides of each negative switch are connected are respectively connected to the negative input terminals of different DC / DC converters 20. As shown in Figure 11, the second sides of each negative switch K43 to K48 are connected, and the voltage is equal at any point after connection; these can be called equidistant points. That is, the negative input terminals of each DC / DC converter 20 can be connected to any point after the negative switches K43 to K48 are connected, as long as the second sides of each negative switch K43 to K48 are connected to the negative input terminals of both DC / DC converters. As shown in Figure 12, the second sides of each negative switch K53 to K58 and the negative input terminals of both DC / DC converters are connected. As shown in Figure 13, the second sides of each negative switch K62 to K67, as well as the negative input terminals of the two DC / DC converters, are connected together. This connection allows the corresponding ports of the involved devices to be connected nearby, facilitating wiring.

[0110] Furthermore, under the above configuration, the positive input terminal of any DC / DC converter 20 can be connected to the corresponding DC power supply through at least one positive switch. For each DC power supply connected to the positive input terminal of each DC / DC converter 20, since their negative terminals are connected to different negative switches, even if their positive terminals have connection points, they will not be connected in parallel. In this case, the positive input terminal of the DC / DC converter 20 only needs one positive switch to ensure the positive terminal disconnection function. Of course, the positive input terminal of the DC / DC converter 20 can also be equipped with two or more positive switches, depending on the number of DC power supplies connected to it, which is not limited here. As shown in Figures 11, 12, and 14, the positive input terminal of each DC / DC converter 20 is connected to two positive switches; as shown in Figure 13, the positive input terminal of each DC / DC converter 20 is connected to one positive switch.

[0111] Figures 11 to 14 show different structures of the DC fault isolation circuit 10 with the number of DC / DC converters 20 M=2 as an example. The number of switches and the number of photovoltaic units can also be other values, which will not be shown one by one. The case when M>2 can be deduced by analogy and will not be shown.

[0112] Similarly, when the DC / DC converter 20 is in a common positive topology, the principle is the same as described above. That is, it can also be configured such that the positive terminals of each DC power supply connected to the negative input terminal of each DC / DC converter 20 are connected to different positive switches. In this configuration, when the number of DC power supplies connected to a positive switch is greater than one, the negative terminals of each DC power supply are connected to the negative input terminals of different DC / DC converters 20 through their respective negative switches. Furthermore, to further reduce the number of switches, it can be configured such that when the number of DC / DC converters 20 is M, there are at least M+1 positive switches, each with its first side connected to at least two negative terminals connected to the DC power supplies of different DC / DC converters 20; alternatively, the positive terminals of each DC power supply connected to the negative input terminal of the DC / DC converter 20 are connected to different DC / DC converters 20 through their respective positive switches. Additionally, the second sides of each positive switch are connected, and the corresponding points are connected to the positive input terminals of different DC / DC converters 20. Furthermore, the negative input terminal of any DC / DC converter 20 is connected to the corresponding DC power supply through at least one negative switch.

[0113] This embodiment not only avoids parallel connections between DC power supplies to prevent reverse current, but also avoids the problem of two switches bearing three times the DC power supply voltage after the switch is disconnected. In addition, by maximizing the number of DC / DC converters with cross-connected DC power supplies, or maximizing the number of cross-connected DC power supplies between different DC / DC converters 20, more switches can be shared, thereby further reducing the number of switches.

[0114] Based on the above embodiments, this embodiment provides some examples of the implementation of the switches in the DC fault isolation circuit 10, such as:

[0115] 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 operate simultaneously, that is, they will maintain a state of being open and closed at the same time. 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.

[0116] Alternatively, all the switches in the DC fault isolation circuit 10 can be integrated into the same linkage switch, which can save on the structural cost of the DC fault isolation circuit 10.

[0117] In practical applications, the switches in the DC fault isolation circuit 10 can be manually disconnected or controlled by a controller. This controller can be a controller within the device housing the DC fault isolation circuit 10; for example, when the DC fault isolation circuit 10 is used in a photovoltaic inverter, the controller can be the controller within the photovoltaic inverter; when the DC fault isolation circuit 10 is used in an energy storage converter, the controller can be the controller within the energy storage converter; or, the controller can also refer to a host computer or other controllers, without limitation here.

[0118] The aforementioned linkage switch can be a rotary DC switch. Referring to Figure 15, the knob 103, connecting rod 102, and P-level linkage switch 101 are arranged along a first direction. 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 connects the knob 103 and the P-level linkage switch 101. The P-level linkage switch 101 includes a first-level switch 111, a second-level switch 112, ..., a P-level switch 11P, where P is an integer greater than or equal to 1. Each level switch can be used as one switch as described in the above embodiment, and it has two pins to achieve separate connections between its two sides to the DC power supply and the DC / DC converter 20. Specifically, one pin can be used to connect to the positive or negative terminal of the DC power supply, and the other pin can be used to connect to the corresponding input terminal of the DC / DC converter 20. The P switches are stacked along the first direction. When the connecting rod 102 rotates, the P switches are linked to close or open, realizing the connection or disconnection between the DC power supply and the DC / DC converter.

[0119] In practical applications, other structures can also be used for this interlocking switch. Figure 15 is only one possible example and is not limited to it. In addition, schemes where each switch is independent are also within the scope of protection of this application.

[0120] Another embodiment of this application also provides a combiner box, referring to FIG16, including: at least two DC / DC converters 20 (DC / DC converters #1 to #M as shown in the figure) and a DC fault isolation circuit 10 as described in any of the above embodiments; wherein:

[0121] Each positive input interface of the DC fault isolation circuit 10 serves as the corresponding positive input terminal of the combiner box, used to connect to the positive terminal 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 combiner box, used to connect to the negative terminal 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. In Figure 16, photovoltaic units (PV1 to PVN1, ..., and PV1 to PVN) are shown. MTaking any one of them as an example, in Figure 16, 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 less than or equal to N1 to N2. M The maximum value in the range. Each positive and negative output interface of the DC fault isolation circuit 10 is connected to the corresponding positive and negative input terminals of the DC / DC converter 20. The DC fault isolation circuit 10 is connected to each DC power supply (PV1 to PVN1, ..., PV1 to PVN as shown in the figure). M The connection relationship between each DC / DC converter 20 and the working principle of the DC fault isolation circuit 10 can be found in the above embodiments, and will not be repeated here.

[0122] The output of the DC / DC converter 20 serves as the output of the combiner box and can be connected to the power grid and / or load via a DC / AC converter.

[0123] In practical applications, the DC / DC converter 20 has various selectable topologies. For example, when the DC power supply is a photovoltaic unit, the DC / DC converter 20 can use a Boost circuit, Buck circuit, Buck-Boost circuit, etc.; while 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 interleaved parallel DC-DC converter 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 be found in the prior art, and will not be elaborated here. The selection of the topology of the DC / DC converter 20 depends on its specific application environment, and all are within the protection scope of this application.

[0124] The combiner box provided in this embodiment, by employing the DC fault isolation circuit 10 described in the above embodiment, can avoid parallel connections between DC power supplies after the switch is disconnected. Therefore, in the event of a reverse DC power connection, there will be no reverse current after the switch is disconnected, and the connection between the reverse DC power supply and the switches on both sides can be directly disconnected, preventing arcing and eliminating the risk of electric shock and fire. Furthermore, cross-connecting DC power supplies between different DC / DC converters can reduce the number of switches used. Additionally, by allocating the positive and negative terminals of the DC power supplies connected to each DC / DC converter 20, the situation where two switches are subjected to three times the DC power supply voltage can be avoided. Moreover, sharing a corresponding switch at the negative or positive input terminal of the DC / DC converter 20 can further reduce the number of switches.

[0125] Another embodiment of this application also provides a power converter, referring to FIG17, including: a DC / AC converter 30, at least two DC / DC converters 20 (DC / DC converters #1 to #M as shown in the figure), and at least one DC fault isolation circuit 10 as described in any of the above embodiments; wherein:

[0126] Each positive input interface of the DC fault isolation circuit 10 serves as the corresponding positive input terminal of the power converter, used to connect to the positive terminal 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, used to connect to the negative terminal 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. In Figure 17, photovoltaic units (PV1 to PVN1, ..., and PV1 to PVN) are shown. M Taking any one of them as an example, in Figure 17, 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 less than or equal to N1 to N2. M The maximum value in the range. When the DC power supply is a photovoltaic unit, the power converter is a photovoltaic inverter (as shown in Figure 17); when the DC power supply is an energy storage unit, the power converter is an energy storage converter (not shown).

[0127] 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 supply (PV1 to PVN1, ..., PV1 to PVN as shown in the figure). M The connection relationship between each DC / DC converter 20 and the working principle of the DC fault isolation circuit 10 can be found in the above embodiments, and will not be repeated here.

[0128] The output terminals of each DC / DC converter 20 are connected to the DC side of the DC / AC converter 30; the AC side of the DC / AC converter 30 serves as the output terminal of the power converter and can be used to connect to the power grid and / or load.

[0129] Figures 1, 2, and 6 to 14 illustrate the example of connecting two DC / DC converters 20 to the DC side of DC / AC converter 30. The only difference is the number of switches in the DC fault isolation circuit 10, or the connection method between each DC / DC converter 20 and the switches in the DC fault isolation circuit 10. In actual applications, the number of devices in this power converter and the number of DC power supplies connected to it can be determined according to the application environment. There are also many other connection structures, which will not be shown one by one.

[0130] As described in the above embodiments, the DC / DC converter 20 has several selectable topologies, which will not be elaborated here. When the DC / DC converter 20 is a common negative topology, the negative terminals of the input and output terminals of each DC / DC converter 20 are connected, and this power converter can be called a common negative converter; when the DC / DC converter 20 is a common positive topology, the positive terminals of the input and output terminals of each DC / DC converter 20 are connected, and this power converter can be called a common positive converter.

[0131] In addition, the DC / AC converter 30 can also have a variety of optional topologies, such as H-bridge inverter topology, three-phase neutral point clamping inverter topology, etc. There is no limitation here, and it depends on the specific application environment.

[0132] When a fault occurs in the system containing the power converter, some or all of the switches in the DC fault isolation circuit 10 can be disconnected manually or by the controller, thereby isolating the DC power supply from the power converter. Possible faults in this 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.

[0133] The power converter provided in this embodiment avoids parallel connections of DC power supplies after the switches are disconnected. When a DC power supply is reverse-connected, there is no reverse current in any DC power supply after the corresponding switch is disconnected. The connection between the reverse-connected DC power supply and the switches on both sides can be directly disconnected without arcing, eliminating the risk of electric shock and fire. In the event of a DC power supply reverse connection fault on-site, timely maintenance can be performed to avoid power generation loss. Furthermore, cross-connecting DC power supplies between different DC / DC converters reduces the number of switches required. Additionally, by allocating the positive and negative terminals of each DC power supply connected to each DC / DC converter 20, the situation where two switches bear three times the DC power supply voltage can be avoided, ensuring that each switch bears a maximum of twice the DC power supply voltage. Moreover, sharing a corresponding switch at the negative or positive input terminal of the DC / DC converter 20 further reduces the number of switches required.

[0134] It is worth noting that the naming of the input and output terminals of each device in this application is only for distinguishing their two sides and is not a restriction on the direction of power transmission. For example, when the DC power supply is an energy storage unit, its discharge process will cause the electrical energy to be transmitted to the power grid and / or load in sequence through the corresponding DC / DC converter 20 and the DC / AC converter 30, or to supply power to the DC load after being transmitted to the DC bus through the corresponding DC / DC converter 20; while its charging process will cause the electrical energy to be charged by the DC / AC converter 30 and the corresponding DC / DC converter 20 in reverse from the power grid, or by other power sources through the DC bus in reverse from the DC bus through the corresponding DC / DC converter 20.

[0135] Similar or identical parts between the various embodiments in this specification can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the description of the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment solution according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0136] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0137] The features described above regarding the disclosed embodiments can be substituted for or combined with each other to enable those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded 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 positive switch is connected to a different positive input interface of the DC fault isolation circuit to connect to the positive terminal of at least one DC power supply; the second side of each positive switch is connected to the corresponding positive output interface of the DC fault isolation circuit to realize the connection of the DC fault isolation circuit to the positive input terminals of at least two DC / DC converters. The first side of each negative switch is connected to a different negative input interface of the DC fault isolation circuit to connect to the negative terminal of at least one DC power supply; the second side of each negative switch is connected to the corresponding negative output interface of the DC fault isolation circuit to realize the connection of the DC fault isolation circuit to the negative input terminals of at least two DC / DC converters. The number of DC power supplies connected to any of the positive switches and the DC power supplies connected to any of the negative switches that belong to the same DC power supply is less than 2. There is at least one positive switch or the negative switch connected to a DC power supply greater than 1, and at least one of the DC power supplies has its other pole connected to a switch connected to the corresponding pole of the input terminal of another DC / DC converter. The positive and negative poles of the corresponding DC power supplies share a switch with different other DC power supplies.

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

3. The DC fault isolation circuit according to claim 1, characterized in that, When a DC power supply is connected to the first side of the positive switch, the negative terminal of the corresponding DC power supply is connected to the first side of any negative switch. When a DC power supply is connected to the first side of the negative switch, the positive terminal of the corresponding DC power supply is connected to the first side of any positive switch.

4. The DC fault isolation circuit according to claim 1, characterized in that, There is at least one switch connected to a DC power supply with a number greater than 1, and the other pole of each DC power supply is connected to a different DC / DC converter through a corresponding switch.

5. The DC fault isolation circuit according to claim 1, characterized in that, The negative terminals of each DC power supply connected to the positive terminal of the DC / DC converter are respectively connected to different negative terminals; or, the positive terminals of each DC power supply connected to the negative terminal of the DC / DC converter are respectively connected to different positive terminals.

6. The DC fault isolation circuit according to claim 1, characterized in that, Each of the DC power supplies connected to the positive terminal of the DC / DC converter has its negative terminal connected to a different negative terminal switch; and each of the DC power supplies connected to the negative terminal of the DC / DC converter has its positive terminal connected to a different positive terminal switch.

7. The DC fault isolation circuit according to claim 1, characterized in that, When the DC / DC converter is a common negative topology, the negative terminals of each DC power supply connected to the positive terminal of the DC / DC converter are respectively connected to different negative switches. When the DC / DC converter is in a common positive topology, the positive terminals of the DC power supplies connected to the negative terminal of the DC / DC converter are respectively connected to different positive switches.

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

9. The DC fault isolation circuit according to claim 7, characterized in that, When the number of DC / DC converters is M and all of them are common negative topologies, M is an integer greater than 1. There are at least M+1 negative switches, wherein the first side of each negative switch is connected to at least two DC power supplies, and the positive terminals of each DC power supply are respectively connected to different DC / DC converters. When the number of DC / DC converters is M and all of them are common positive topologies, M is an integer greater than 1. There are at least M+1 positive switches, wherein the first side of each positive switch is connected to at least two DC power supplies, and the negative terminals of each DC power supply 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 a common negative topology, the positive terminal of the input terminal of the DC / DC converter and the negative terminal of each DC power supply connected to it are respectively connected to different DC / DC converters through the corresponding negative terminal switches. When the DC / DC converter is in a common positive topology, the negative terminal of the input terminal of the DC / DC converter and the positive terminal of each DC power supply connected to it are respectively connected to different DC / DC converters through corresponding positive switches.

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

12. The DC fault isolation circuit according to claim 7, characterized in that, When the DC / DC converter is a common negative topology, the second sides of each negative switch are connected, and after being connected, they are respectively connected to the negative input terminals of different DC / DC converters. When the DC / DC converter is in a common positive topology, the second sides of each positive switch are connected, and after being connected, they are respectively connected to the positive input terminals 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 between any of the DC power supplies.

14. The DC fault isolation circuit according to any one of claims 1 to 12, characterized in that, Each switch group is integrated into a different linkage switch, or all 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 can be manually operated or controlled by a controller to disconnect or disconnect.

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

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