DC-DC converter, photovoltaic inverter and DC combiner box

Abstract

The utility model discloses a DC-DC converter, a photovoltaic inverter and a DC combiner box. The photovoltaic module comprises a first type of photovoltaic unit group and a second type of photovoltaic unit group; each first type of photovoltaic unit group comprises a photovoltaic unit, and each second type of photovoltaic unit group comprises two photovoltaic units; the positive output ports of the two photovoltaic units in each second-type photovoltaic unit group are connected in series with the same protection switch, and the negative output ports of the two photovoltaic units in each second-type photovoltaic unit group are connected in series with the same protection switch. According to the DC-DC converter provided by the utility model, the wiring mode of the photovoltaic unit and the tripping direct-current switch is reasonably arranged, so that the current of each pole of the switch is more balanced, and the maximum input current capability of the DC-DC converter can be improved while the current utilization rate of the tripping switch is effectively improved under the condition of not changing the type selection of the switch.

Description

Technical Field

[0001] The utility model belongs to the technical field of photovoltaic power generation, and specifically relates to a DC-DC converter, a photovoltaic inverter and a DC combiner box. Background Art

[0002] At present, in order to improve the DC ratio of photovoltaic power generation system (the ratio of the power of photovoltaic unit to the input power of photovoltaic inverter), each MPPT circuit is usually connected to at least two photovoltaic units. Take the case of a short circuit in one photovoltaic unit or a short circuit in the line where the photovoltaic unit is located as an example. At this time, the short-circuit current is the sum of the output currents of the photovoltaic units of other connected roads. When the number of photovoltaic units of other connected roads is only 1, the photovoltaic unit and the line can withstand this short-circuit current due to the small short-circuit current. However, when the number of photovoltaic units of other connected roads is 2 or more, the short-circuit current is large. In order to protect the photovoltaic unit and the line, a fuse can be connected in series at the positive output end or the negative output end of the photovoltaic unit to protect the photovoltaic unit and the line by blowing the fuse. However, since the fuse's fusing current is generally high and the output current of each photovoltaic unit is low, the sum of the short-circuit currents of multiple photovoltaic units may be difficult to reach the fuse's fusing current, making the fuse take a long time to blow, resulting in the fuse being unable to effectively protect the photovoltaic unit and the line, and the fuse failure rate is relatively high and the reliability is low.

[0003] In order to solve this problem, a remote trip switch is generally used to disconnect the fault current for protection. However, the current of each level of the trip switch is not balanced, and the current of a single pole will be too large, resulting in uneven heating, which limits the further expansion of the system capacity and thus limits the maximum input current capacity of the DC-DC converter. Summary of the invention

[0004] In view of the above technical problems, the utility model provides an improved DC-DC converter, a photovoltaic inverter and a DC combiner box.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] A DC-DC converter is used to access a photovoltaic module having M photovoltaic units, each of which includes one or more photovoltaic components;

[0007] The DC-DC converter includes a DC-DC circuit, a DC bus and a plurality of protection switches, wherein the DC bus is connected to the input end of the DC-DC circuit;

[0008] The photovoltaic unit is connected to the DC bus through the protection switch, and each protection switch is used to disconnect the corresponding photovoltaic unit from the DC bus when the reverse current of the photovoltaic unit connected to it is greater than a first current value or overcurrent occurs;

[0009] M is a positive integer greater than or equal to 5, and the output voltage of each branch where the photovoltaic unit is located is the same; the photovoltaic module includes a first type of photovoltaic unit group and a second type of photovoltaic unit group, the number of the first type of photovoltaic unit group is N, and the number of the second type of photovoltaic unit group is K, wherein N is a positive integer and K is a positive integer and Each of the first-type photovoltaic unit groups includes one photovoltaic unit, and each of the second-type photovoltaic unit groups includes two photovoltaic units;

[0010] The positive output ports of the two photovoltaic units in each of the second-type photovoltaic unit groups are connected in series with the same protection switch, and the negative output ports of the two photovoltaic units in each of the second-type photovoltaic unit groups are connected in series with the same protection switch;

[0011] The positive output port of a photovoltaic cell in the first type of photovoltaic cell group and the positive output port of a photovoltaic cell in one of the second type of photovoltaic cell groups are connected in series with the same protection switch; the negative output port of a photovoltaic cell in the second type of photovoltaic cell group and the negative output port of a photovoltaic cell in another of the second type of photovoltaic cell groups are connected in series with the same protection switch.

[0012] Preferably, when N is a positive integer greater than or equal to 2, the protection switches connected in series to the positive output ports of the photovoltaic units in different groups of the first-type photovoltaic units are different, and the protection switches connected in series to the negative output ports of the photovoltaic units in different groups of the first-type photovoltaic units are different.

[0013] Preferably, the number of the protection switches is P.

[0014] Preferably, each of the protection switches corresponds to one pole number of a DC isolating switch, and the DC isolating switch comprises a handle and P poles.

[0015] Further, when M=5, P=4, N=1, K=2, the negative output ports of the first two photovoltaic units in the second type photovoltaic unit group are connected in series to the first protection switch, and the positive output ports of the first two photovoltaic units in the second type photovoltaic unit group are connected in series to the second protection switch;

[0016] The negative output ports of the two photovoltaic units in the second photovoltaic unit group of the second type are connected in series to the third protection switch, and the positive output ports of the two photovoltaic units in the second photovoltaic unit group of the second type are connected in series to the fourth protection switch;

[0017] The positive output port of the photovoltaic unit in the first type photovoltaic unit group is connected in series to the second protection switch, and the negative output port of the photovoltaic unit in the first type photovoltaic unit group is connected in series to the third protection switch;

[0018] Among them, the first protection switch is located at a shorter distance from the handle than the second protection switch, the second protection switch is located at a shorter distance from the handle than the third protection switch, and the third protection switch is located at a shorter distance from the handle than the fourth protection switch.

[0019] Further, when M=5, P=4, N=1, K=2, the positive output ports of the first two photovoltaic units in the second type photovoltaic unit group are connected in series to the first protection switch, and the negative output ports of the first two photovoltaic units in the second type photovoltaic unit group are connected in series to the second protection switch;

[0020] The positive output ports of the two photovoltaic units in the second photovoltaic unit group of the second type are connected in series to the third protection switch, and the negative output ports of the two photovoltaic units in the second photovoltaic unit group of the second type are connected in series to the fourth protection switch;

[0021] The positive output port of the photovoltaic unit in the first type photovoltaic unit group is connected in series to the first protection switch, and the negative output port of the photovoltaic unit in the first type photovoltaic unit group is connected in series to the fourth protection switch;

[0022] Among them, the first protection switch is located at a shorter distance from the handle than the second protection switch, the second protection switch is located at a shorter distance from the handle than the third protection switch, and the third protection switch is located at a shorter distance from the handle than the fourth protection switch.

[0023] Preferably, a plurality of said DC-DC converters and DC-AC converters form an inverter;

[0024] The positive output ports of the multiple DC-DC converters are connected in parallel to the positive input port of the DC-AC converter, and the negative output ports of the multiple DC-DC converters are connected in parallel to the negative input port of the DC-AC converter.

[0025] Preferably, multiple DC-DC converters form a DC combiner box; the positive output ports of multiple DC-DC converters are connected in parallel to form the positive output port of the DC combiner box; and the negative output ports of multiple DC-DC converters are connected in parallel to form the negative output port of the DC combiner box.

[0026] A photovoltaic inverter comprises a DC-AC converter, wherein the photovoltaic inverter further comprises the DC-DC converter as described above; a plurality of positive output ports of the DC-DC converters are connected in parallel to a positive input port of the DC-AC converter, and a plurality of negative output ports of the DC-DC converters are connected in parallel to a negative input port of the DC-AC converter.

[0027] A DC combiner box comprises a plurality of DC-DC converters as described above; the plurality of DC-DC converters are used to connect to photovoltaic modules; the positive output ports of the plurality of DC-DC converters are connected in parallel to form the positive output port of the DC combiner box; the negative output ports of the plurality of DC-DC converters are connected in parallel to form the negative output port of the DC combiner box.

[0028] The utility model adopts the above solution, which has the following advantages compared with the prior art:

[0029] The DC-DC converter in the utility model makes the current of each pole of the switch more balanced by reasonably setting the wiring mode of the photovoltaic unit and the tripping DC switch. Without changing the switch selection, the current utilization rate of the tripping switch is effectively improved. At the same time, the maximum input current capacity of the DC-DC converter can be improved, which is convenient for expanding the system capacity.

[0030] In a further preferred solution, by reasonably setting the positions of the protection switches at different distances from the handle, when a fault occurs and the protection switch is disconnected, the voltage difference between adjacent protection switches becomes smaller, thereby solving the problem of high withstand voltage between two adjacent protection switches. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 is a wiring diagram of a known DC-DC converter;

[0033] Figure 2 This is a wiring diagram of a DC-DC converter in an embodiment of the utility model;

[0034] Figure 3 for Figure 2 Schematic diagram of voltage distribution after PV3 is reversely connected;

[0035] Figure 4 Another wiring diagram of the DC-DC converter in the embodiment of the utility model;

[0036] Figure 5 for Figure 4 Schematic diagram of voltage distribution after PV3 is reversely connected;

[0037] Figure 6 This is another wiring diagram of the DC-DC converter in the embodiment of the utility model;

[0038] Figure 7 for Figure 6 Schematic diagram of voltage distribution after PV3 is reversely connected;

[0039] Figure 8 This is another wiring diagram of the DC-DC converter in the embodiment of the utility model;

[0040] Fig. 9 for Figure 8 Schematic diagram of voltage distribution after PV3 is reversely connected;

[0041] Fig.10 A schematic diagram of a photovoltaic inverter in an embodiment of the utility model;

[0042] Fig.11 It is a schematic diagram of a DC combiner box in an embodiment of the utility model;

[0043] Among them, 1. Photovoltaic module; 2. DC-DC converter; 3. Photovoltaic unit; 4. Photovoltaic assembly; 5. Protection switch; 6. DC-DC circuit; 7. First type of photovoltaic unit group; 8. Second type of photovoltaic unit group; 9. DC-AC converter; 10. Photovoltaic inverter; 11. DC junction box. DETAILED DESCRIPTION

[0044] In order to solve the problem of relatively high fuse failure rate, a remote trip switch is generally used to interrupt the fault current. Figure 1 The following is a wiring diagram of a known DC-DC converter, where S1'-S4' is a pole number of a DC isolating switch, PV1'-PV5' is a photovoltaic unit, and once a PV short circuit or reverse connection is found, the control system will issue a trip command to disconnect the corresponding switch (any one or more of S1'-S4'). However, in this wiring method, the current of each pole on S1'-S4' is not balanced, and the current of a single pole will be too large, which limits the further expansion of the system capacity.

[0045] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0046] In this embodiment, the electrical parameters of a single photovoltaic module are not specifically limited, and those skilled in the art can set them according to actual needs. In this embodiment, the output voltages of multiple photovoltaic units connected to the same DC-DC converter are the same.

[0047] The following is an example of a DC-DC converter:

[0048] like Figures 2 to 9 As shown, the DC-DC converter is used to access a photovoltaic module 1 having M photovoltaic units 3, each of which includes one or more photovoltaic components 4 (see Figure 2 PV1-PV5 in the figure), in this embodiment, each photovoltaic unit 3 includes a photovoltaic assembly 4 as an example for specific description. The DC-DC converter 2 includes multiple protection switches 5, a DC bus and a DC-DC circuit 6. The DC bus is connected to the input end of the DC-DC circuit 6, and the output end of the DC-DC circuit 6 is the output end of the DC-DC converter 2. The photovoltaic unit 3 is connected to the DC bus through the protection switch 5, and each protection switch 5 is used to disconnect the corresponding photovoltaic unit and the DC bus when the reverse current of the photovoltaic unit 3 connected to it is greater than the first current value (the first current value specifically refers to a preset safety current value) or there is an overcurrent in the line. The DC-DC circuit 201 can specifically be a boost circuit, a buck circuit or a buck-boost circuit.

[0049] Specifically, M is a positive integer greater than or equal to 5, and the output voltage of each branch where the photovoltaic unit 3 is located is the same. The photovoltaic module 1 includes a first type photovoltaic unit group 7 and a second type photovoltaic unit group 8. The number of the first type photovoltaic unit group 7 is N, and the number of the second type photovoltaic unit group 8 is K. Wherein, N is a positive integer and satisfies K is a positive integer and satisfies Each first-type photovoltaic unit group 7 includes one photovoltaic unit 3 , and each second-type photovoltaic unit group 8 includes two photovoltaic units 3 , therefore, M=N+2K.

[0050] The positive output ports of the two photovoltaic cells 3 in each second type photovoltaic cell group 8 are connected in series with the same protection switch 5, and the negative output ports of the two photovoltaic cells 3 in each second type photovoltaic cell group 8 are connected in series with the same protection switch 5. Figure 2 For example, PV1 and PV2 both belong to the photovoltaic module 4 in the photovoltaic unit 3 in the same second-type photovoltaic unit group 8, and the positive output ports of PV1 and PV2 are connected in series with the same protection switch S1, and the negative output ports of PV1 and PV2 are connected in series with the same protection switch S2. PV4 and PV5 belong to the photovoltaic module 4 in the photovoltaic unit 3 in another second-type photovoltaic unit group 8, and the positive output ports of PV4 and PV5 are connected in series with the same protection switch S3, and the negative output ports of PV4 and PV5 are connected in series with the same protection switch S4.

[0051] The positive output port of the photovoltaic unit 3 in the first type photovoltaic unit group 7 and the positive output port of the photovoltaic unit in one of the second type photovoltaic unit groups are connected in series with the same protection switch 5, and the negative output port of the photovoltaic unit 3 in the second type photovoltaic unit group 7 and the negative output port of the photovoltaic unit 3 in another second type photovoltaic unit group 7 are connected in series with the same protection switch 5. Figure 2 For example, PV3 belongs to the photovoltaic component 4 in the photovoltaic unit 3 in the first type photovoltaic unit group 7. The positive output port of PV3 and the positive output ports of PV1 and PV2 are connected in series with the same protection switch S1, and the negative output port of PV3 and the negative output ports of PV4 and PV5 are connected in series with the same protection switch S4.

[0052] When N is a positive integer greater than or equal to 2, the protection switches 5 connected in series to the positive output ports of the photovoltaic units 3 in different first-type photovoltaic unit groups 7 are different, and the protection switches 5 connected in series to the negative output ports of the photovoltaic units 3 in different first-type photovoltaic unit groups 7 are different. Figure 6 For example, PV3 and PV6 belong to different first-class photovoltaic unit groups 7, wherein the protection switch connected in series to the positive output port of PV3 is S1, the protection switch connected in series to the positive output port of PV6 is S3, the protection switch connected in series to the negative output port of PV3 is S4, and the protection switch connected in series to the negative output port of PV6 is S6.

[0053] The number of protection switches 5 is P. That is, P = K × 2. Each protection switch 5 corresponds to one pole of the DC isolating switch. The DC isolating switch includes a handle and P poles. The P protection switches 5 are controlled by the handle. Figure 2As shown, when M=5, P=4, N=1, and K=2. The positive output ports of the two photovoltaic cells 3 (i.e., PV1 and PV2) in the first second-class photovoltaic cell group 8 are connected in series to the first protection switch S1, and the negative output ports of the two photovoltaic cells 3 in the first second-class photovoltaic cell group 8 are connected in series to the second protection switch S2. The positive output ports of the two photovoltaic cells 3 (i.e., PV4 and PV5) in the second second-class photovoltaic cell group 8 are connected in series to the third protection switch S3, and the negative output ports of the two photovoltaic cells 3 in the second second-class photovoltaic cell group 8 are connected in series to the fourth protection switch S4. The positive output port of the photovoltaic cell 3 (i.e., PV3) in the first-class photovoltaic cell group 7 is connected in series to the first protection switch S1, and the negative output port of the photovoltaic cell 3 in the first-class photovoltaic cell group 7 is connected in series to the fourth protection switch S4. Among them, the distance between the first protection switch S1 and the handle is smaller than that between the second protection switch S2 and the handle, the distance between the second protection switch S2 and the handle is smaller than that between the third protection switch S3, and the distance between the third protection switch S3 and the handle is smaller than that between the fourth protection switch S4. The handle is specifically an electric control handle, and a control signal is sent to the coil inside the handle through a controller, so that the coil triggers a component for tripping the switch to achieve control of the trip switch. In some other embodiments, the tripping of the switch can also be manually controlled directly through the handle. Furthermore, in actual use, the protection switch close to the handle is more likely to trip.

[0054] like Figure 2 As shown, the working current of each PV is In, so the total current processed by the DC-DC circuit 6 is 5×In. Different from the existing wiring method, the current of each switch is 2 times In or 3 times In, which effectively reduces the current flowing through the protection switch and makes the current more evenly distributed. The positive poles of PV1, PV2 and PV3 are connected to S1 together, the negative poles of PV1 and PV2 are connected to S2 together, the positive poles of PV4 and PV5 are connected to S3 together, and the negative poles of PV3, PV4 and PV5 are connected to S4 together. In this way, the current flowing through S1 is 3 times the PV current (3×In), the current flowing through S2 is 2 times the PV current (2×In), the current flowing through S3 is (2×In), and the current flowing through S4 is 3 times the PV current (3×In). When a short circuit or reverse connection fault occurs in the photovoltaic module 4 in one of the photovoltaic units 3, the system detects the fault and the protection switch will be controlled to be disconnected in time. At this time, if the short-circuited or reverse-connected PV module is one of PV1, PV2, PV4 and PV5, then one PV will still form a loop current with it, but because there are only two PV strings, only one PV short-circuit current can be formed, so there is no risk of damage. If the short-circuited or reverse-connected PV module is PV3, the short-circuit path is cut off, and no current will be generated on all PV strings, which is also safe.

[0055] Figure 3The schematic diagram of PV3 being reversed is given, and the relative potential on the left side of each switch can be seen. Assuming that the negative poles of PV1 and PV2 are at 0 level (0×V), that is, the potential on the left side of S2 is 0V; then the positive poles of PV1 and PV2 are 1 times the photovoltaic voltage (1×V), that is, the potential on the left side of S1 is 1×V; the positive pole of PV3 is 2×V when the photovoltaic voltage is superimposed on the positive poles of PV1 and PV2, that is, the potential on the left side of S4 is 2×V; the positive poles of PV4 and PV5 are 3×V when the photovoltaic voltage is superimposed on the positive pole of PV3, that is, the potential on the left side of S3 is 3×V. If S2 and S3 are adjacent, facing the withstand voltage of 3×V, the voltage difference is large.

[0056] Preferably, refer to Figure 4 As shown, when M=5, P=4, N=1, and K=2. The negative output ports of the two photovoltaic cells 3 (i.e., PV1 and PV2) in the first second-class photovoltaic cell group 8 are connected in series to the first protection switch S1, and the positive output ports of the two photovoltaic cells 3 in the first second-class photovoltaic cell group 8 are connected in series to the second protection switch S2. The negative output ports of the two photovoltaic cells 3 (i.e., PV4 and PV5) in the second second-class photovoltaic cell group 8 are connected in series to the third protection switch S3, and the positive output ports of the two photovoltaic cells 3 in the second second-class photovoltaic cell group 8 are connected in series to the fourth protection switch S4. The positive output port of the photovoltaic cell 3 in the first-class photovoltaic cell group 7 is connected in series to the second protection switch S2, and the negative output port of the photovoltaic cell 3 in the first-class photovoltaic cell group 7 is connected in series to the third protection switch S3. Among them, the distance between the first protection switch S1 and the handle is smaller than that between the second protection switch S2 and the handle, the distance between the second protection switch S2 and the handle is smaller than that between the third protection switch S3, and the distance between the third protection switch S3 and the handle is smaller than that between the fourth protection switch S4.

[0057] Figure 4 Wiring method in Figure 2 The difference is that the connection sequence of the protection switches is changed, so that after PV3 is reversely connected, the withstand voltage of the adjacent switches is reduced. Figure 5 The voltage distribution diagram after PV3 is connected is given. Assume that the negative poles of PV1 and PV2 are at 0 level (0×V), that is, the potential on the left side of S1 is 0V; then the positive poles of PV1 and PV2 are 1 times the photovoltaic voltage (1×V), that is, the potential on the left side of S2 is 1×V; the positive pole of PV3 is 2×V with one times the photovoltaic voltage superimposed on the positive poles of PV1 and PV2, that is, the potential on the left side of S3 is 2×V; the positive poles of PV4 and PV5 are 3×V with one times the photovoltaic voltage superimposed on the positive pole of PV3, that is, the potential on the left side of S4 is 3×V. From Figure 5 It can be seen that the withstand voltage between adjacent switches is 1 times the photovoltaic voltage, which solves the problem of high withstand voltage between two adjacent protection switches.

[0058] Figures 6 to 9Two wiring methods are given when M=8. Figure 8 The corresponding wiring method is better than Figure 6 The corresponding wiring method, because Figure 8 After PV3 is reversed (i.e. Fig. 9 ), the voltage difference between two adjacent protection switches is small. By further optimizing the position of the protection switch, the voltage difference between adjacent protection switches can be controlled to be smaller when the protection switch is disconnected due to a fault, further improving the safety of the DC-DC converter.

[0059] In this embodiment, the multi-channel DC-DC converter 2 and the DC-AC converter 9 form an inverter. The positive output ports of the multi-channel DC-DC converter 2 are connected in parallel to the positive input port of the DC-AC converter 9, and the negative output ports of the multi-channel DC-DC converter 2 are connected in parallel to the negative input port of the DC-AC converter 9. The multi-channel DC-DC converter 2 forms a DC combiner box 11, and the positive output ports of the multi-channel DC-DC converter 2 are connected in parallel to form the positive output port of the DC combiner box 11, and the negative output ports of the multi-channel DC-DC converter 2 are connected in parallel to form the negative output port of the DC combiner box 11.

[0060] This embodiment also includes a photovoltaic inverter 10, such as Fig.10 As shown, the photovoltaic inverter 10 includes the above-mentioned DC-DC converter 2 and DC-AC converter 9. Specifically, the positive output ports of the multi-channel DC-DC converter 2 are connected in parallel to the positive input port of the DC-AC converter 9, and the negative output ports of the multi-channel DC-DC converter 2 are connected in parallel to the negative input port of the DC-AC converter 9. The specific composition mechanism of the photovoltaic module and the structure of the protection switch are as described above, and the details are not repeated here.

[0061] This embodiment also includes a DC combiner box 11, such as Fig.11 As shown, the DC combiner box 11 includes multiple DC-DC converters 2 as described above, and the multiple DC-DC converters 2 are used to connect to the photovoltaic module 1. The positive output ports of the multiple DC-DC converters 2 are connected in parallel to form the positive output port of the DC combiner box 11, and the negative output ports of the multiple DC-DC converters 2 are connected in parallel to form the negative output port of the DC combiner box 11.

[0062] In summary, the DC-DC converter, photovoltaic inverter and DC combiner box in this embodiment have at least the following advantages:

[0063] 1. By reasonably setting the connection mode between the photovoltaic unit and the tripping DC switch, the current of each pole of the switch can be more balanced. Without changing the switch selection, the current utilization rate of the tripping switch can be effectively improved, and the maximum input current capacity of the DC-DC converter can be increased, which is convenient for expanding the system capacity;

[0064] 2. By reasonably setting the position of the protection switch at different distances from the handle, when a fault occurs and the protection switch is disconnected, the voltage difference between adjacent protection switches becomes smaller, thus solving the problem of high withstand voltage between two adjacent protection switches.

[0065] As shown in this specification and claims, the terms "comprises" and "include" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list, and the method or device may also include other steps or elements. The term "and / or" as used herein includes any combination of one or more of the relevant listed items.

[0066] It should be noted that, unless otherwise specified, when a feature is referred to as being "fixed" or "connected" to another feature, it can be directly fixed or connected to the other feature, or it can be indirectly fixed or connected to the other feature. In addition, the descriptions of up, down, left, right, etc. used in the present invention are only relative to the relative positional relationship of the components of the present invention in the accompanying drawings.

[0067] The above embodiment is only for illustrating the technical concept and features of the utility model, and is a preferred embodiment. Its purpose is to enable people familiar with the technology to understand the content of the utility model and implement it accordingly, and it cannot be used to limit the protection scope of the utility model. Any equivalent transformation or modification made according to the principle of the utility model should be included in the protection scope of the utility model.

Claims

1. A DC-DC converter, which is used to access a photovoltaic module having M photovoltaic units, each of which includes one or more photovoltaic components; The DC-DC converter includes a DC-DC circuit, a DC bus and a plurality of protection switches, wherein the DC bus is connected to the input end of the DC-DC circuit; The photovoltaic unit is connected to the DC bus through the protection switch, and each protection switch is used to disconnect the corresponding photovoltaic unit from the DC bus when the reverse current of the photovoltaic unit connected to it is greater than a first current value or overcurrent occurs; It is characterized in that M is a positive integer greater than or equal to 5, and the output voltage of each branch where the photovoltaic unit is located is the same; The photovoltaic module includes a first type of photovoltaic unit group and a second type of photovoltaic unit group, the number of the first type of photovoltaic unit group is N, and the number of the second type of photovoltaic unit group is K, wherein N is a positive integer and K is a positive integer and Each of the first-type photovoltaic unit groups includes one photovoltaic unit, and each of the second-type photovoltaic unit groups includes two photovoltaic units; The positive output ports of the two photovoltaic units in each of the second-type photovoltaic unit groups are connected in series with the same protection switch, and the negative output ports of the two photovoltaic units in each of the second-type photovoltaic unit groups are connected in series with the same protection switch; The positive output port of a photovoltaic cell in the first type of photovoltaic cell group and the positive output port of a photovoltaic cell in one of the second type of photovoltaic cell groups are connected in series with the same protection switch; the negative output port of a photovoltaic cell in the second type of photovoltaic cell group and the negative output port of a photovoltaic cell in another of the second type of photovoltaic cell groups are connected in series with the same protection switch.

2. The DC-DC converter according to claim 1, characterized in that: When N is a positive integer greater than or equal to 2, the protection switches connected in series to the positive output ports of the photovoltaic units in different first-type photovoltaic unit groups are different, and the protection switches connected in series to the negative output ports of the photovoltaic units in different first-type photovoltaic unit groups are different.

3. The DC-DC converter according to claim 1, characterized in that: The number of the protection switches is P.

4. The DC-DC converter according to claim 1, characterized in that: Each of the protection switches corresponds to one pole of a DC isolating switch, and the DC isolating switch includes a handle and P poles.

5. The DC-DC converter according to claim 4, characterized in that: When M=5, P=4, N=1, K=2, The negative output ports of the two photovoltaic units in the first photovoltaic unit group of the second type are connected in series to the first protection switch, and the positive output ports of the two photovoltaic units in the first photovoltaic unit group of the second type are connected in series to the second protection switch; The negative output ports of the two photovoltaic units in the second photovoltaic unit group of the second type are connected in series to the third protection switch, and the positive output ports of the two photovoltaic units in the second photovoltaic unit group of the second type are connected in series to the fourth protection switch; The positive output port of the photovoltaic unit in the first type photovoltaic unit group is connected in series to the second protection switch, and the negative output port of the photovoltaic unit in the first type photovoltaic unit group is connected in series to the third protection switch; Among them, the first protection switch is located at a shorter distance from the handle than the second protection switch, the second protection switch is located at a shorter distance from the handle than the third protection switch, and the third protection switch is located at a shorter distance from the handle than the fourth protection switch.

6. The DC-DC converter according to claim 4, characterized in that: When M=5, P=4, N=1, K=2, the positive output ports of the first two photovoltaic units in the second type photovoltaic unit group are connected in series to the first protection switch, and the negative output ports of the first two photovoltaic units in the second type photovoltaic unit group are connected in series to the second protection switch; The positive output ports of the two photovoltaic units in the second photovoltaic unit group of the second type are connected in series to the third protection switch, and the negative output ports of the two photovoltaic units in the second photovoltaic unit group of the second type are connected in series to the fourth protection switch; The positive output port of the photovoltaic unit in the first type photovoltaic unit group is connected in series to the first protection switch, and the negative output port of the photovoltaic unit in the first type photovoltaic unit group is connected in series to the fourth protection switch; Among them, the first protection switch is located at a shorter distance from the handle than the second protection switch, the second protection switch is located at a shorter distance from the handle than the third protection switch, and the third protection switch is located at a shorter distance from the handle than the fourth protection switch.

7. The DC-DC converter according to claim 1, characterized in that: The multiple DC-DC converters and DC-AC converters form an inverter; The positive output ports of the multiple DC-DC converters are connected in parallel to the positive input port of the DC-AC converter, and the negative output ports of the multiple DC-DC converters are connected in parallel to the negative input port of the DC-AC converter.

8. The DC-DC converter according to claim 1, characterized in that: A plurality of the DC-DC converters form a DC combiner box; the positive output ports of the plurality of DC-DC converters are connected in parallel to form the positive output port of the DC combiner box; and the negative output ports of the plurality of DC-DC converters are connected in parallel to form the negative output port of the DC combiner box.

9. A photovoltaic inverter, comprising a DC-AC converter, characterized in that: The photovoltaic inverter also includes a DC-DC converter as described in any one of claims 1 to 8; the positive output ports of multiple DC-DC converters are connected in parallel to the positive input port of the DC-AC converter, and the negative output ports of multiple DC-DC converters are connected in parallel to the negative input port of the DC-AC converter.

10. A DC combiner box, characterized in that: It comprises a plurality of DC-DC converters as described in any one of claims 1 to 8, wherein the plurality of DC-DC converters are used to connect to a photovoltaic module; the positive output ports of the plurality of DC-DC converters are connected in parallel to form a positive output port of the DC combiner box; and the negative output ports of the plurality of DC-DC converters are connected in parallel to form a negative output port of the DC combiner box.

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