Lightning protection circuit and inverter

Abstract

This utility model discloses a lightning protection circuit and an inverter, relating to the field of power electronics technology. The lightning protection circuit includes: multiple first lightning protection units, the first ends of which are connected to corresponding phase lines on the AC side of the inverter circuit; second lightning protection units, the first ends of which are connected to the second ends of the multiple first lightning protection units respectively, and the second ends of the second lightning protection units are grounded; and multiple first voltage divider units, connected in parallel to the multiple first lightning protection units one-to-one. This lightning protection circuit can reduce the risk of long-term overvoltage conduction failure of a single first lightning protection unit, improving the stability and reliability of the inverter.

Description

Technical Field

[0001] This utility model relates to the field of power electronics technology, and in particular to a lightning protection circuit and an inverter. Background Technology

[0002] In related technologies, to achieve lightning protection for inverters, a surge protector is connected to each phase line on the AC side of the inverter, converging at a common point, and then grounded through another surge protector. However, this technology can lead to uneven voltage distribution between the two surge protectors connected in series with ground on any phase line. This causes the surge protector with the higher voltage on the corresponding phase line to be constantly in an alternating on / off state, which can easily cause the surge protector to fail due to prolonged overvoltage conduction. Utility Model Content

[0003] The purpose of this invention is to propose a lightning protection circuit and inverter to reduce the risk of long-term overvoltage conduction failure of the lightning protection unit and improve the stability and reliability of the inverter.

[0004] In a first aspect, this utility model proposes a lightning protection circuit, comprising: a plurality of first lightning protection units, the first ends of which are connected to the corresponding phase lines on the AC side of an inverter circuit; a second lightning protection unit, the first ends of which are respectively connected to the second ends of the plurality of first lightning protection units, and the second ends of which are grounded; and a plurality of first voltage divider units, which are connected in parallel to the plurality of first lightning protection units one by one.

[0005] In some embodiments, the circuit further includes a second voltage divider unit connected in parallel with the second lightning protection unit.

[0006] In some embodiments, the first surge protection unit includes: a first varistor, a first end of the first varistor being connected to a corresponding phase line on the AC side of the inverter circuit, and a second end of the first varistor being connected to a first end of the second surge protection unit.

[0007] In some embodiments, the first lightning protection unit includes: a first gas discharge tube, a first end of which is connected to a corresponding phase line on the AC side of the inverter circuit, and a second end of which is connected to the first end of the second lightning protection unit.

[0008] In some embodiments, the first surge protection unit includes: a second varistor, the first end of which is connected to a corresponding phase line on the AC side of the inverter circuit, and the second end of which is connected to the first end of the second surge protection unit; and a second gas discharge tube, which is connected in parallel with the second varistor.

[0009] In some embodiments, the second surge protection unit includes a third varistor, the first end of which is connected to the second end of the plurality of first surge protection units respectively, and the second end of the third varistor is grounded.

[0010] In some embodiments, the second lightning protection unit includes: a third gas discharge tube, the first end of which is connected to the second end of the plurality of first lightning protection units respectively, and the second end of the third gas discharge tube is grounded.

[0011] In some embodiments, the second lightning protection unit includes: a fourth varistor, the first end of which is connected to the second end of the plurality of first lightning protection units respectively, and the second end of which is grounded; and a fourth gas discharge tube, which is connected in parallel with the fourth varistor.

[0012] In some embodiments, the first voltage divider unit includes a first voltage divider resistor, which is connected in parallel with a corresponding first surge protection unit.

[0013] In some embodiments, there are multiple first voltage divider resistors, which are connected in series and / or in parallel and then connected in parallel with the corresponding first surge protection unit.

[0014] In some embodiments, the second voltage divider unit includes a second voltage divider resistor, which is connected in parallel with the second lightning protection unit.

[0015] In some embodiments, the number of the second voltage-dividing resistors is multiple, and the multiple second voltage-dividing resistors are connected in series and / or in parallel and then connected in parallel with the second surge protection unit.

[0016] In some embodiments, the second voltage divider unit has the same structure as the first voltage divider unit.

[0017] Secondly, this utility model proposes an inverter, comprising: an inverter circuit; and the lightning protection circuit described in the first aspect, wherein the lightning protection circuit is connected to the AC side of the inverter circuit.

[0018] This utility model discloses a surge protection circuit and inverter. One end of multiple first surge protection units is connected to the corresponding phase line on the AC side of the inverter circuit, and the other end is grounded through a second surge protection unit. Multiple first voltage divider units are connected in parallel with each of the first surge protection units. Since each first surge protection unit corresponds to a first voltage divider unit in parallel, the impedance across the corresponding first surge protection unit is lowered, thereby lowering the voltage across the corresponding first surge protection unit. This allows the voltage division between the two surge protection units on each phase line to be relatively uniform, sharing the AC voltage. This reduces the risk of long-term overvoltage conduction of the first surge protection units and improves the stability and reliability of the inverter.

[0019] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the lightning protection circuit according to one embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the lightning protection circuit according to another embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the lightning protection circuit of another embodiment of this utility model;

[0023] Figure 4 This is the topology diagram of the lightning protection circuit of the first example of this utility model;

[0024] Figure 5 This is a topology diagram of the lightning protection circuit of the second example of this utility model;

[0025] Figure 6 This is the topology diagram of the lightning protection circuit of the third example of this utility model;

[0026] Figure 7 This is a schematic diagram of the structure of an inverter system according to an embodiment of the present invention;

[0027] Figure 8 This is a schematic diagram of the structure of an inverter system according to an example of this utility model;

[0028] Figure 9 This is a schematic diagram of the inverter system of another example of this utility model. Detailed Implementation

[0029] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0030] The lightning protection circuit and inverter of this utility model are described below with reference to the accompanying drawings.

[0031] In related technologies, to achieve lightning protection for inverters, a surge protector is connected to each phase line on the AC side of the inverter, converging at a common point, and then grounded through another surge protector. However, this technology can lead to uneven voltage distribution between the two surge protectors connected in series with ground on any phase line. This causes the individual surge protector between the corresponding phase line and the common point to be constantly in an alternating on / off state, which can easily lead to surge protector failure due to prolonged overvoltage.

[0032] Therefore, this utility model proposes a lightning protection circuit to reduce the risk of long-term overvoltage conduction of the lightning protection unit and improve the stability and reliability of the inverter.

[0033] Figure 1 This is a schematic diagram of the lightning protection circuit according to one embodiment of the present invention.

[0034] like Figure 1 As shown, the lightning protection circuit 100 includes: multiple first lightning protection units 10, second lightning protection units 20, and multiple voltage divider units 30.

[0035] Among them, the first end of multiple first lightning protection units 10 is connected to the corresponding phase line on the AC side of inverter circuit 60; the first end of second lightning protection unit 20 is connected to the second end of multiple first lightning protection units 10 respectively, and the second end of second lightning protection unit 20 is grounded; multiple first voltage divider units 30 are connected in parallel with multiple first lightning protection units 10 in a one-to-one correspondence.

[0036] In this embodiment, the inverter circuit 60 may be a three-phase inverter circuit (such as...). Figure 1 (as shown) or single-phase inverter circuit (such as) Figure 2 (As shown).

[0037] Taking a three-phase inverter circuit as an example, see Figure 1A first surge protection unit 10 and a second surge protection unit 20 are connected in series between any one phase line and ground. The first surge protection unit 10 is connected in parallel with a first voltage divider unit 30. When the inverter in the three-phase inverter circuit is not struck by lightning, the phase voltage of the three AC phases to ground is applied to the second surge protection unit 20 and the first surge protection unit 10 of each phase. At this time, the three first voltage dividers 30 connected in parallel with the three first surge protection units 10 can lower the impedance at both ends of the corresponding first surge protection unit 10, thereby forcibly lowering the voltage at both ends of the corresponding first surge protection unit 10. This makes the voltage division of the two series surge protection units to ground relatively uniform, and they jointly bear the AC three-phase voltage in each operating mode. This reduces the risk of long-term overvoltage conduction of the first surge protection unit 10 and improves the stability and reliability of the inverter. When a lightning strike occurs on the inverter, the lightning voltage exceeds the conduction voltage of the first surge protection unit 10 of each of the three phases of the AC circuit. The first surge protection unit 10 is turned on instantly, and its impedance instantly becomes ohmic. The parallel voltage divider unit 30 is bypassed, and all the lightning energy is discharged to the ground through the surge protection unit, thus protecting the inverter from lightning strikes.

[0038] This surge protection circuit 100 can meet the requirements of increased inverter voltage levels without increasing the number of surge protection units or significantly increasing the voltage specifications of the surge protection units. This ensures low cost, solves the overvoltage risk of surge protection units during normal inverter operation (without lightning strikes), and also ensures the safety of the inverter during lightning strikes.

[0039] In some embodiments of this utility model, such as Figure 3 As shown, the lightning protection circuit 100 also includes a second voltage divider unit 40, which is connected in parallel with the second lightning protection unit 20.

[0040] Similar to the first voltage divider unit 30, the second voltage divider unit 40 can lower the impedance across the second surge protection unit 20, thereby forcibly lowering the voltage across the second surge protection unit 20 and reducing the risk of overvoltage conduction of the second surge protection unit 20.

[0041] In some examples, such as Figure 4 As shown, the first surge protection unit 10 includes: a first varistor Z1, the first end of the first varistor Z1 is connected to the corresponding phase line on the AC side of the inverter circuit 60, and the second end of the first varistor Z1 is connected to the first end of the second surge protection unit 20.

[0042] In other examples, such as Figure 5 As shown, the first lightning protection unit 10 includes a first gas discharge tube G1. The first end of the first gas discharge tube G1 is connected to the corresponding phase line on the AC side of the inverter circuit 60, and the second end of the first gas discharge tube G1 is connected to the first end of the second lightning protection unit 20.

[0043] In some other examples, such as Figure 6 As shown, the first surge protection unit 10 includes: a second varistor Z2 and a second gas discharge tube G2. The first end of the second varistor Z2 is connected to the corresponding phase line on the AC side of the inverter circuit 60, and the second end of the second varistor Z2 is connected to the first end of the second surge protection unit 20; the second gas discharge tube G2 is connected in parallel with the second varistor Z2.

[0044] As one implementation method, see Figure 4 , Figure 5 , Figure 6 The second lightning protection unit 20 has the same structure as the first lightning protection unit 10.

[0045] Specifically, in some examples, see Figure 4 The second surge protection unit 20 includes a third varistor Z3. The first end of the third varistor Z3 is connected to the second end of a plurality of first surge protection units 10 respectively, and the second end of the third varistor Z3 is grounded.

[0046] In other examples, see Figure 5 The second lightning protection unit 20 includes a third gas discharge tube G3. The first end of the third gas discharge tube G3 is connected to the second end of a plurality of first lightning protection units 10 respectively, and the second end of the third gas discharge tube G3 is grounded.

[0047] In yet another example, see Figure 6 The second lightning protection unit 20 includes a fourth varistor Z4 and a fourth gas discharge tube G4. The first end of the fourth varistor Z4 is connected to the second end of a plurality of first lightning protection units 10 respectively. The second end of the fourth varistor Z4 is grounded. The fourth gas discharge tube G4 is connected in parallel with the fourth varistor Z4.

[0048] It should be noted that the structure of the second surge protection unit 20 may also be different from that of the first surge protection unit 10. For example, the second surge protection unit 20 may only include the third varistor Z3, while the first surge protection unit 10 may only include the second gas discharge tube G2; or the second surge protection unit 20 may only include the third varistor Z3, while the first surge protection unit 10 may include both the second varistor Z2 and the second gas discharge tube G2, etc.

[0049] In some examples, such as Figure 4 As shown, the first voltage divider unit 30 includes a first voltage divider resistor R1, which is connected in parallel with the corresponding first lightning protection unit 10.

[0050] In other examples, such as Figure 5 , Figure 6 As shown, the first voltage divider unit 30 includes: a plurality of first voltage divider resistors R1 ( Figure 6 Two R1s are shown. Figure 5(Two or more R1 are shown). Multiple first voltage divider resistors R1 are connected in series and then connected in parallel with the corresponding first lightning protection unit 10.

[0051] It should be noted that the connection method of multiple first voltage divider resistors R1 is not limited to... Figure 5 , Figure 6 The series connection method shown can be configured according to specific needs. For example, multiple first voltage divider resistors R1 can also be connected in parallel and then connected in parallel with the corresponding first surge protection unit 10; or, multiple first voltage divider resistors R1 can also be connected in series and parallel (such as three first voltage divider resistors, two of which are connected in series and then the other is connected in parallel) and then connected in parallel with the corresponding first surge protection unit 10.

[0052] As one implementation method, see Figure 4 , Figure 5 , Figure 6 The second voltage divider unit 40 has the same structure as the first voltage divider unit 30.

[0053] Specifically, in some examples, see Figure 4 The second voltage divider unit 40 includes a second voltage divider resistor R2.

[0054] In other examples, the second voltage divider unit 40 includes a plurality of second voltage divider resistors R2 connected in series. Figure 6 Two R2 values ​​are shown. Figure 5 (Show more than two R2s).

[0055] Similar to the second surge protection unit 20 and the first surge protection unit 10, the structures of the second voltage divider unit 40 and the first voltage divider unit 30 can also differ. For example, the second voltage divider unit 40 may include only one second voltage divider resistor R2, while the first surge protection unit 10 may include two first voltage divider resistors R1 connected in series; or, the second voltage divider unit 40 may include two second voltage divider resistors R2 connected in series, while the first surge protection unit 10 may include only one first voltage divider resistor R1. Of course, when the second voltage divider unit 40 includes multiple second voltage divider resistors R2, these resistors can be connected in parallel or in a series-plus-parallel connection. Various combinations are possible for different structures, depending on the number of voltage divider resistors, the connection method, etc. It should be understood that there can also be multiple combinations of two surge protection units with the first voltage divider unit 30, or combinations of two surge protection units with two voltage divider units.

[0056] The following is based on Figure 4 The working principle of the lightning protection circuit 100 of this utility model embodiment is explained using the example shown below:

[0057] When the inverter is not struck by lightning, the phase voltage of the three AC phases to ground is applied to the two varistors of each phase. At this time, the three first voltage divider resistors R1 connected in parallel on the three first varistors Z1 of the three phases pull down the impedance across the corresponding first varistor Z1, thereby forcibly pulling down the voltage across the corresponding first varistor Z1. This makes the voltage division of the two series-connected varistors of each phase to ground relatively uniform, and they jointly bear the AC three-phase voltage in each operating mode, thereby reducing the long-term overvoltage conduction risk of the first lightning protection unit 10.

[0058] When the inverter is struck by lightning, the lightning voltage exceeds the conduction voltage of the first varistor Z1 of each of the three phases of AC. The first varistor Z1 conducts instantaneously, and its impedance instantly becomes ohmic. The first voltage divider resistor R1 connected in parallel is bypassed, and all the lightning energy is discharged to the ground through the two varistors of each phase, which plays a role in lightning protection for the system.

[0059] As described above, the surge protection circuit 100 of this utility model embodiment, through the first surge protection unit 10 and the first voltage divider unit 30, can reduce the risk of long-term overvoltage conduction of the first surge protection unit 10 caused by uneven voltage division of each surge protection unit connected in series with ground. It does not require increasing the number of additional surge protection units or improving the voltage specifications of individual surge protection units, thereby improving the stability and reliability of surge protection of the inverter system, and is low in cost.

[0060] Figure 7 This is a schematic diagram of the inverter structure according to one embodiment of the present invention.

[0061] like Figure 7 As shown, the inverter 1000 includes an inverter circuit 60 and a surge protection circuit 100 as described in the above embodiment. The surge protection circuit 100 is connected to the AC side of the inverter circuit 60.

[0062] See Figure 7 The DC side of the inverter circuit 60 is connected to the photovoltaic module, and the AC side of the inverter 200 is connected to the power grid. The first terminals of multiple first lightning protection units 10 in the lightning protection circuit 100 are connected to the corresponding phase lines on the AC side of the inverter circuit 60.

[0063] In some embodiments of this utility model, such as Figure 8 As shown, the inverter 1000 also includes an AC switch 50, the first end of which is connected to the AC side of the inverter circuit 60, and the second end of which is connected to the power grid.

[0064] To meet higher safety requirements, two AC switches can be connected in series and closed sequentially to complete the grid connection of inverter 100.

[0065] In some examples, such as Figure 9As shown, the inverter 1000 also includes a boost circuit 70, the first DC side of which is connected to the photovoltaic module, and the second DC side of which is connected to the DC side of the inverter circuit 60.

[0066] The boost circuit 70 can boost the DC power output from the photovoltaic module, such as from a first voltage to a second voltage; then, the inverter circuit 60 converts the second voltage DC power into AC power and feeds it into the power grid. Compared to Figure 8 The example shown, Figure 9 The example shown adds a boost circuit 70 to better meet grid connection requirements.

[0067] Furthermore, in some examples, such as Figure 9 As shown, the inverter 1000 also includes a bus capacitor C, which is connected between the positive and negative terminals of the DC bus.

[0068] Through the energy storage function of the bus capacitor C, power fluctuations can be buffered, high-frequency and low-frequency ripples of DC bus voltage can be suppressed, and instantaneous energy compensation can be provided when load changes or grid disturbances occur, thereby improving the grid connection performance of the inverter system 1000.

[0069] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0070] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0071] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0072] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0073] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A lightning protection circuit, characterized in that, include: Multiple first lightning protection units, the first end of which is connected to the corresponding phase line on the AC side of the inverter circuit; The second lightning protection unit has a first end connected to the second end of the plurality of first lightning protection units, and the second end of the second lightning protection unit is grounded. Multiple first voltage divider units are connected in parallel to the multiple first lightning protection units, one by one.

2. The lightning protection circuit of claim 1, wherein, The circuit also includes: The second voltage divider unit is connected in parallel with the second lightning protection unit.

3. The lightning protection circuit of claim 1, wherein, The first lightning protection unit includes: The first varistor has its first end connected to the corresponding phase line on the AC side of the inverter circuit, and its second end connected to the first end of the second lightning protection unit.

4. The lightning protection circuit according to claim 1, characterized in that, The first lightning protection unit includes: The first gas discharge tube has its first end connected to the corresponding phase line on the AC side of the inverter circuit, and its second end connected to the first end of the second lightning protection unit.

5. The lightning protection circuit of claim 1, wherein, The first lightning protection unit includes: The second varistor has its first end connected to the corresponding phase line on the AC side of the inverter circuit, and its second end connected to the first end of the second lightning protection unit. The second gas discharge tube is connected in parallel with the second varistor.

6. The lightning protection circuit according to any of claims 1-5, characterized in that, The second lightning protection unit includes: The third varistor has its first end connected to the second end of each of the plurality of first lightning protection units, and its second end is grounded.

7. The lightning protection circuit according to any one of claims 1-5, characterized in that, The second lightning protection unit includes: The third gas discharge tube has its first end connected to the second end of each of the plurality of first lightning protection units, and its second end is grounded.

8. The lightning protection circuit according to any one of claims 1-5, characterized in that, The second lightning protection unit includes: The fourth varistor has its first terminal connected to the second terminal of each of the plurality of first lightning protection units, and its second terminal grounded. The fourth gas discharge tube is connected in parallel with the fourth varistor.

9. The lightning protection circuit of claim 1, wherein, The first voltage divider unit includes: The first voltage divider resistor is connected in parallel with the corresponding first lightning protection unit.

10. The lightning protection circuit of claim 9, wherein, The number of the first voltage divider resistors is multiple, and the multiple first voltage divider resistors are connected in series and / or in parallel and then connected in parallel with the corresponding first lightning protection unit.

11. The lightning protection circuit of claim 2, wherein, The second voltage divider unit includes: The second voltage divider resistor is connected in parallel with the second lightning protection unit.

12. The lightning protection circuit of claim 11, wherein, The number of the second voltage divider resistors is multiple, and the multiple second voltage divider resistors are connected in series and / or in parallel and then connected in parallel with the second lightning protection unit.

13. An inverter, characterized by comprising: include: Inverter circuit; The lightning protection circuit as described in any one of claims 1-12, wherein the lightning protection circuit is connected to the AC side of the inverter circuit.

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