String type inverter

Abstract

The utility model provides a string type inverter, which relates to the technical field of inverters and comprises a main power loop, a switching power supply, an auxiliary switch power taking device and a current protection device. Wherein the switching power supply takes electricity from a direct-current bus in a main power loop; the auxiliary switch electricity taking device takes electricity from an external photovoltaic group string or an input side of a main power loop and supplies power to the direct current bus; and the current protection device is connected in series in a branch circuit where the auxiliary switch power taking device is located. The auxiliary switch power taking device can prevent devices in a loop where the auxiliary switch power taking device is located from being damaged due to overlarge current to a certain extent.

Description

Technical Field

[0001] The utility model relates to the technical field of inverters, and more specifically, to a string inverter. Background Art

[0002] At present, an auxiliary switch power supply device is provided on the DC side of the string inverter to avoid the problem of related circuits being burned out due to reverse connection of the connected photovoltaic strings when the string inverter is powered on for the first time.

[0003] However, the current string inverter has the problem that the circuit where the auxiliary switch power taking device is located is easily damaged due to excessive current. Utility Model Content

[0004] In order to solve the problem that the circuit where the auxiliary switch power taking device of the current string inverter is located is easily damaged due to excessive current, the utility model provides a string inverter.

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

[0006] The utility model provides a string inverter, including: a main power circuit, a switching power supply, an auxiliary switch power supply device and a current protection device; wherein,

[0007] The switching power supply is powered by a DC bus in the main power circuit;

[0008] The auxiliary switch power supply device takes power from an external photovoltaic string or the input side of the main power circuit, and supplies power to the DC bus;

[0009] The current protection device is connected in series in the branch where the auxiliary switch power taking device is located.

[0010] Optionally, the current protection device comprises: at least one of a first current protection module and a second current protection module;

[0011] The first current protection module is connected in series with the positive electrode of the auxiliary switch power taking device;

[0012] The second current protection module is connected in series with the negative electrode of the auxiliary switch power taking device.

[0013] Optionally, when the auxiliary switch power taking device takes power from an external photovoltaic string, the first current protection module is connected between the photovoltaic string and the input side of the auxiliary switch power taking device, or between the output side of the auxiliary switch power taking device and the DC bus;

[0014] The second current protection module is connected between the photovoltaic string and the input side of the auxiliary switch power taking device, or between the output side of the auxiliary switch power taking device and the DC bus;

[0015] When the auxiliary switch power taking device takes power from the input side of the main power circuit, the first current protection module is connected between the input side of the main power circuit and the input side of the auxiliary switch power taking device, or between the output side of the auxiliary switch power taking device and the DC bus;

[0016] The second current protection module is connected between the input side of the main power circuit and the input side of the auxiliary switch power taking device, or between the output side of the auxiliary switch power taking device and the DC bus.

[0017] Optionally, the first current protection module is: a first resistor, a first inductor, or a first resistor and a first inductor connected in series;

[0018] The second current protection module is: a second resistor, a second inductor, or a second resistor and a second inductor connected in series.

[0019] Optionally, the first current protection module is a first resistor, and the second current protection module is a second resistor;

[0020] Alternatively, the first current protection module is a first inductor, and the second current protection module is a second inductor;

[0021] Alternatively, the first current protection module is a first resistor and a first inductor connected in series, and the second current protection module is a second resistor and a second inductor connected in series.

[0022] Optionally, the current protection device is a surge current discharge device.

[0023] Optionally, the surge current discharge device is a lightning arrester, a varistor or a GAS tube.

[0024] Optionally, the current protection device is arranged outside the auxiliary switch power taking device, or,

[0025] The current protection device is integrated inside the auxiliary switch power taking device.

[0026] Optionally, the main power circuit includes: a DC / AC conversion circuit and at least one DC / DC conversion circuit;

[0027] The input side of each of the DC / DC conversion circuits is connected to the corresponding photovoltaic string through a corresponding fault isolation circuit;

[0028] The output side of each DC / DC conversion circuit is connected to the DC side of the DC / AC conversion circuit through the DC bus.

[0029] Optionally, a first voltage detection device is provided on the input side of the DC / DC conversion circuit connected to the auxiliary switch power taking device;

[0030] A second voltage detection device is provided on the DC bus;

[0031] The operating condition of the DC / AC conversion circuit includes: the first voltage detection device and the second voltage detection device both detect voltage.

[0032] The utility model adopts the above technical solution and has the following beneficial effects:

[0033] A string inverter includes: a main power circuit, a switching power supply, an auxiliary switch power supply device and a current protection device; wherein the switching power supply is powered by a DC bus in the main power circuit; the auxiliary switch power supply device is powered by an external photovoltaic string or the input side of the main power circuit, and supplies power to the DC bus; the current protection device is connected in series to the branch where the auxiliary switch power supply device is located. Based on this, due to the addition of a current protection device, the current protection device is connected in series to the branch where the auxiliary switch power supply device is located, so that the utility model can use the current protection device to avoid damage to the components in the circuit where the auxiliary switch power supply device is located due to excessive current to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0035] Figure 1 This is a schematic diagram of the circuit structure of a string inverter provided by an embodiment of the utility model;

[0036] Figure 2 This is a schematic diagram of the circuit structure of another string inverter provided by an embodiment of the utility model;

[0037] Figure 3 This is a schematic diagram of the circuit structure of another string inverter provided by an embodiment of the utility model;

[0038] Figure 4 This is a schematic diagram of the circuit structure of another string inverter provided by an embodiment of the utility model;

[0039] Figure 5 This is a schematic diagram of the direction of large currents such as surge current or lightning current of a string inverter provided by an embodiment of the utility model;

[0040] Figure 6 This is a schematic diagram of the circuit structure of another string inverter provided by an embodiment of the utility model;

[0041] Figure 7 It is a schematic diagram of the operation of a string inverter provided in an embodiment of the utility model.

[0042] Among them, 11 is a photovoltaic string, 12 is a fault isolation circuit, 13 is a DC / DC conversion circuit, 14 is a bus capacitor, 15 is an auxiliary switch power supply device, 16 is a switching power supply, and 17 is a current protection device. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0044] At present, an auxiliary switch power supply device is set on the DC side of the string inverter to avoid the problem of related circuits being burned out due to reverse connection of the photovoltaic strings connected to the string inverter when the string inverter is powered on for the first time. Specifically, the string inverter includes a fault isolation circuit, a DC / DC conversion circuit, a bus capacitor, an auxiliary switch power supply device and a switching power supply.

[0045] Among them, the DC / DC conversion circuit and the auxiliary switch power supply device are both used to draw power from the external photovoltaic string to supply power to the bus capacitor, the switching power supply is used to draw power from the bus capacitor, and the fault isolation circuit is controlled by the switching power supply. Assuming that the auxiliary switch power supply device is not set in the DC side of the string inverter, if there is at least one photovoltaic string that is reversely connected, after the fault isolation circuit is closed, the reversely connected photovoltaic string and the fault isolation circuit will form a short-circuit loop, and the short-circuit loop will make the DC / DC conversion circuit unable to draw power from the photovoltaic string to supply power to the bus capacitor, and then the switching power supply will not be powered. When the switching power supply is not powered (that is, when the switching power supply is not in working state), the switching power supply cannot disconnect the fault isolation circuit, resulting in the short-circuit loop existing for a long time, and the relevant circuits are burned by the corresponding short-circuit current.

[0046] Therefore, in order to prevent the relevant circuits from being burned out due to the long-term existence of the short-circuit loop, an auxiliary switch power supply is set on the DC side of the string inverter, so that when the photovoltaic string is reversely connected, the switching power supply can also be powered. The switching power supply can disconnect the fault isolation circuit when the photovoltaic string is detected to be reversely connected, thereby preventing the relevant circuits from being burned out.

[0047] However, in order to reduce the production cost of string inverters, the auxiliary switch power supply device uses an ordinary DC switch. When the string inverter is running, if it encounters a large current such as a surge current or a lightning current, part of the large current will flow into the branch where the auxiliary switch power supply device is located, which may cause damage to the auxiliary switch power supply device and / or other devices such as the switching power supply.

[0048] Based on this, in order to avoid damage to the components in the circuit where the auxiliary switch power taking device is located due to excessive current to a certain extent, the utility model provides a string inverter. The technical solution of the utility model is described in detail below in conjunction with the accompanying drawings.

[0049] Figure 1 Schematic diagram of the circuit structure of a string inverter provided by the embodiment of the utility model. Figure 1 As shown, the string inverter includes: a main power circuit, a switching power supply 16 , an auxiliary switch power supply 15 and a current protection device 17 .

[0050] Among them, the main power circuit includes: DC / AC conversion circuit ( Figure 1 ) and at least one DC / DC conversion circuit 13 ( Figure 1 In the description, the number of DC / DC conversion circuits 13 is taken as 1 as an example).

[0051] The input side of each DC / DC conversion circuit 13 is connected to the corresponding photovoltaic string 11 through a corresponding fault isolation circuit 12 .

[0052] The output side of each DC / DC conversion circuit 13 is connected to the DC side of the DC / AC conversion circuit via a DC bus.

[0053] The switching power supply 16 draws power from the DC bus in the main power circuit.

[0054] The auxiliary switch power supply device 15 takes power from the external photovoltaic string 11 or the input side of the main power circuit, and supplies power to the DC bus.

[0055] The current protection device 17 is connected in series in the branch where the auxiliary switch power taking device 15 is located.

[0056] The embodiment of the utility model adopts the above-mentioned technical solution. Since a current protection device is added and the current protection device is connected in series in the branch where the auxiliary switch power supply device is located, the utility model can, through the current protection device, to a certain extent prevent the devices in the circuit where the auxiliary switch power supply device is located from being damaged due to excessive current.

[0057] In the embodiment of the present invention, the current protection device 17 includes: at least one of a first current protection module and a second current protection module.

[0058] The first current protection module is connected in series with the positive electrode of the auxiliary switch power taking device.

[0059] The second current protection module is connected in series with the negative electrode of the auxiliary switch power taking device.

[0060] In an embodiment of the utility model, when the auxiliary switch power taking device takes power from an external photovoltaic string, the first current protection module is connected between the photovoltaic string and the input side of the auxiliary switch power taking device, or between the output side of the auxiliary switch power taking device and the DC bus.

[0061] The second current protection module is connected between the photovoltaic string and the input side of the auxiliary switch power taking device, or between the output side of the auxiliary switch power taking device and the DC bus.

[0062] When the auxiliary switch power device draws power from the input side of the main power circuit, the first current protection module is connected between the input side of the main power circuit and the input side of the auxiliary switch power device, or between the output side of the auxiliary switch power device and the DC bus.

[0063] The second current protection module is connected between the input side of the main power circuit and the input side of the auxiliary switch power taking device, or between the output side of the auxiliary switch power taking device and the DC bus.

[0064] refer to Figure 1 , which is explained by taking the example that the first current protection module and the second current protection module are both connected between the input side of the main power circuit and the input side of the auxiliary switch power taking device.

[0065] In an embodiment of the utility model, the first current protection module includes: a first resistor, a first inductor, or a first resistor and a first inductor connected in series.

[0066] The second current protection module includes: a second resistor, a second inductor, or a second resistor and a second inductor connected in series.

[0067] In a specific example, Figure 2 Schematic diagram of the circuit structure of another string inverter provided by the embodiment of the utility model. Figure 2As shown, the first current protection module is a first resistor R1, and the second current protection module is a second resistor R2.

[0068] In another specific example, Figure 3 Schematic diagram of the circuit structure of another string inverter provided by the embodiment of the utility model. Figure 3 As shown, the first current protection module is a first inductor L1, and the second current protection module is a second inductor L2.

[0069] In another specific example, Figure 4 Schematic diagram of the circuit structure of another string inverter provided by the embodiment of the utility model. Figure 4 As shown, the first current protection module is a first resistor R1 and a first inductor L1 connected in series, and the second current protection module is a second resistor R2 and a second inductor L2 connected in series.

[0070] refer to Figures 2 to 4 Since the impedance in the main power circuit is relatively low, a resistor and / or inductor is set in the branch where the auxiliary switch power device 15 is located, so that when the string inverter is running, if a large current such as a surge current or a lightning current is encountered, all or most of the large current will flow into the main power circuit, thereby preventing the components in the circuit where the auxiliary switch power device 15 is located from being damaged due to excessive current. Figure 5 As shown, the second current I2 in the main power circuit is much larger than the first current I1 in the branch where the auxiliary switch power taking device 15 is located.

[0071] In the embodiment of the utility model, Figure 6 As shown, the current protection device may be a surge current discharge device.

[0072] Specifically, when the string inverter is running, if it encounters a large current such as a surge current or a lightning current, since a surge current discharge device is provided in the branch where the auxiliary switch power supply device 15 is located, the surge current discharge device will prevent the large current such as the surge current or the lightning current from flowing into the auxiliary switch power supply device 15 and the switching power supply 16 at the subsequent stage, thereby avoiding to a certain extent the damage of the components in the circuit where the auxiliary switch power supply device 15 is located due to excessive current.

[0073] In the embodiment of the utility model, the surge current discharge device can be any surge current discharge device in the prior art, and the embodiment of the utility model is not specifically limited here. For example, the surge current discharge device is a lightning arrester, a varistor or a GAS tube (gas discharge tube). Among them, the lightning arrester is a surge protector SPD, also known as a lightning arrester and a lightning arrester.

[0074] In the embodiment of the utility model, the current protection device can be arranged outside the auxiliary switch power taking device, so that it is convenient to perform maintenance and other operations on the current protection device at a later stage.

[0075] Secondly, the current protection device can also be integrated inside the auxiliary switch power taking device, which is helpful to prevent the current protection device from being damaged by the external environment.

[0076] During the operation of the string inverter, when the fault isolation circuit 12 connected to the auxiliary switch power taking device 15 is disconnected, the photovoltaic module 11 supplies power to the bus capacitor 14 through the auxiliary switch power taking device 15, and the DC / AC conversion circuit will continue to extract power from the bus capacitor 14. In this case, the auxiliary switch power taking device 15 will continue to supply power to the bus capacitor 14, and the direction of the corresponding power flow P is as follows: Figure 7 As shown. Since the auxiliary switch power taking device 15 is a common DC switch without a tripping function, the design margin of the power device in the circuit is very small. Therefore, when the auxiliary switch power taking device 15 supplies power to the bus capacitor 14 for a long time, the auxiliary switch power taking device 15 is prone to fail due to overcurrent or overheating.

[0077] Therefore, in order to prevent the auxiliary switch power device 15 from failing due to overcurrent or overheating, the string inverter can be prohibited from operating when it is detected that the fault isolation circuit 12 connected to the auxiliary switch power device 15 is disconnected. When the fault isolation circuit 12 connected to the auxiliary switch power device 15 is disconnected, there is no voltage on the input side of the DC / DC conversion circuit connected to the fault isolation circuit 12, but there is voltage on the DC bus.

[0078] Based on this, in the embodiment of the utility model, a first voltage detection device is provided on the input side of the DC / DC conversion circuit connected to the auxiliary switch power taking device.

[0079] A second voltage detection device is arranged on the DC bus.

[0080] The operating conditions of the DC / AC conversion circuit include: the first voltage detection device and the second voltage detection device both detect voltage.

[0081] In actual application, after starting the string inverter, it is determined whether the second voltage detection device detects a voltage. If the second voltage detection device detects a voltage, it is determined whether the first voltage detection device detects a voltage. If the first voltage detection device detects a voltage, the DC / AC conversion circuit is allowed to operate. If the first voltage detection device does not detect a voltage, the DC / AC conversion circuit is prohibited from operating and a preset alarm action is executed.

[0082] It should be noted that each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referenced to each other. The modules and submodules in the devices and terminals of each embodiment of the utility model can be merged, divided and deleted according to actual needs, and the features recorded in each embodiment can be replaced or combined.

[0083] In the several embodiments provided by the present utility model, it should be understood that the disclosed terminals and devices can be implemented in other ways. For example, the division of modules or submodules is only a logical function division, and there may be other division methods in actual implementation, such as multiple submodules or modules can be combined or integrated into another module, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or modules, which can be electrical, mechanical or other forms.

[0084] The modules or submodules described as separate components may or may not be physically separated, and the components of the modules or submodules may or may not be physical modules or submodules, that is, they may be located in one place, or they may be distributed on multiple network modules or submodules. Some or all of the modules or submodules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0085] In addition, each functional module or sub-module in each embodiment of the present invention may be integrated into one processing module, or each module or sub-module may exist physically separately, or two or more modules or sub-modules may be integrated into one module.

[0086] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such article or device. In the absence of further restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the article or device including the elements.

[0087] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A string inverter, characterized in that: include: Main power circuit, switching power supply, auxiliary switch power supply and current protection device; among which, The switching power supply is powered by a DC bus in the main power circuit; The auxiliary switch power supply device takes power from an external photovoltaic string or the input side of the main power circuit, and supplies power to the DC bus; The current protection device is connected in series in the branch where the auxiliary switch power taking device is located.

2. The string inverter according to claim 1, characterized in that: The current protection device comprises: at least one of a first current protection module and a second current protection module; The first current protection module is connected in series with the positive electrode of the auxiliary switch power taking device; The second current protection module is connected in series with the negative electrode of the auxiliary switch power taking device.

3. The string inverter according to claim 2, characterized in that: When the auxiliary switch power taking device takes power from an external photovoltaic string, the first current protection module is connected between the photovoltaic string and the input side of the auxiliary switch power taking device, or between the output side of the auxiliary switch power taking device and the DC bus; The second current protection module is connected between the photovoltaic string and the input side of the auxiliary switch power taking device, or between the output side of the auxiliary switch power taking device and the DC bus; When the auxiliary switch power taking device takes power from the input side of the main power circuit, the first current protection module is connected between the input side of the main power circuit and the input side of the auxiliary switch power taking device, or between the output side of the auxiliary switch power taking device and the DC bus; The second current protection module is connected between the input side of the main power circuit and the input side of the auxiliary switch power taking device, or between the output side of the auxiliary switch power taking device and the DC bus.

4. The string inverter according to claim 2, characterized in that: The first current protection module is: a first resistor, a first inductor, or a first resistor and a first inductor connected in series; The second current protection module is: a second resistor, a second inductor, or a second resistor and a second inductor connected in series.

5. The string inverter according to claim 2, characterized in that: The first current protection module is a first resistor, and the second current protection module is a second resistor; Alternatively, the first current protection module is a first inductor, and the second current protection module is a second inductor; Alternatively, the first current protection module is a first resistor and a first inductor connected in series, and the second current protection module is a second resistor and a second inductor connected in series.

6. The string inverter according to claim 1, characterized in that: The current protection device is a surge current discharge device.

7. The string inverter according to claim 6, characterized in that: The surge current discharge device is a lightning arrester, a varistor or a GAS tube.

8. The string inverter according to any one of claims 1 to 7, characterized in that: The current protection device is arranged outside the auxiliary switch power taking device, or, The current protection device is integrated inside the auxiliary switch power taking device.

9. The string inverter according to any one of claims 1 to 7, characterized in that: The main power circuit includes: a DC / AC conversion circuit and at least one DC / DC conversion circuit; The input side of each of the DC / DC conversion circuits is connected to the corresponding photovoltaic string through a corresponding fault isolation circuit; The output side of each DC / DC conversion circuit is connected to the DC side of the DC / AC conversion circuit through the DC bus.

10. The string inverter according to claim 9, characterized in that: A first voltage detection device is provided on the input side of the DC / DC conversion circuit connected to the auxiliary switch power taking device; A second voltage detection device is provided on the DC bus; The operating condition of the DC / AC conversion circuit includes: the first voltage detection device and the second voltage detection device both detect voltage.

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