Power switch circuit based on parallel connection of switching devices

Abstract

The invention relates to a power switch circuit based on parallel connection of switching devices. The power switch circuit comprises a connection structure and a switch module. The connecting structure comprises a first connecting structure, a second connecting structure, a third connecting structure and a fourth connecting structure; the switch module comprises a first switch unit and a second switch unit; the first connecting structure is connected between the first end and the input end of the first switch unit; the second connecting structure is connected between the first end and the input end of the second switch unit; the third connecting structure is connected between the second end of the first switch unit and the output end; the fourth connection structure is connected between the second end of the second switch unit and the output end. The first connection structure and the second connection structure are symmetrical, and the third connection structure and the fourth connection structure are symmetrical, so that the circuit structures where the first switch unit and the second switch unit are located are symmetrical, dynamic current balance between the first switch unit and the second switch unit is further realized, and the current sharing capability of the power switch circuit is improved.

Description

A power switching circuit based on parallel switching devices Technical Field

[0001] This disclosure relates to the field of power module technology, and in particular to a power switching circuit based on parallel connection of switching devices. Background Technology

[0002] Modular multilevel converters (MMCs) have become the most mature topology for flexible DC transmission due to their excellent waveform quality, modular structure, and easy scalability. As a key component of the MMC commutation arm, the performance of the power switching module directly affects the MMC's safe operating boundary and dynamic response capability. In conventional technologies, power switching circuits typically use multiple devices connected in parallel to increase the module's current capacity. However, due to insufficient current sharing capability, power switching circuits are prone to current unevenness during dynamic operation. This can lead to problems such as stress concentration, temperature rise deviation, and efficiency degradation, and may even cause device failure or damage.

[0003] Therefore, how to improve the current sharing capability of power switching circuits has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] To solve the above-mentioned technical problems, or at least partially solve them, this disclosure provides a power switching circuit based on parallel connection of switching devices. By setting the first connection structure to be symmetrical with the second connection structure, and the third connection structure to be symmetrical with the fourth connection structure, the circuit structures of the first switching unit and the second switching unit are symmetrical, thereby achieving dynamic current balance between the first switching unit and the second switching unit and improving the current sharing capability of the power switching circuit.

[0005] This disclosure provides a power switching circuit based on parallel connection of switching devices. The power switching circuit includes a connection structure and a switching module.

[0006] The connection structure includes a first connection structure, a second connection structure, a third connection structure, and a fourth connection structure; the switch module includes a first switch unit and a second switch unit; the first connection structure is connected between the first end and the input end of the first switch unit; the second connection structure is connected between the first end and the input end of the second switch unit; the third connection structure is connected between the second end and the output end of the first switch unit; the fourth connection structure is connected between the second end and the output end of the second switch unit; wherein, the number of switching devices included in the first switch unit and the second switch unit is the same, and the connection structure meets at least one of the following conditions: the first connection structure is symmetrical to the second connection structure, and the third connection structure is symmetrical to the fourth connection structure.

[0007] Optionally, the switching module includes 2n switching devices; the 2n switching devices include n first switching devices and n second switching devices; the first switching unit includes n first switching devices; the second switching unit includes n second switching devices; the connection structure also includes n fifth connection structures and n sixth connection structures; the first end of the first switching device is connected to the first end of the first switching unit through the corresponding fifth connection structure, and the second end of the first switching device is connected to the second end of the first switching unit; the first end of the second switching device is connected to the first end of the second switching unit through the corresponding sixth connection structure, and the second end of the second switching device is connected to the second end of the second switching unit; where n is a positive integer; the fifth connection structure and the sixth connection structure are symmetrical.

[0008] Optionally, the switching module includes 2n+1 switching devices; the 2n+1 switching devices include n third switching devices, n fourth switching devices, and 1 fifth switching device; the first switching unit includes n third switching devices; the second switching unit includes n fourth switching devices; the connection structure also includes n seventh connection structures, n eighth connection structures, ninth connection structures, and tenth connection structures; the first end of the third switching device is connected to the first end of the first switching unit through the corresponding seventh connection structure, and the second end of the third switching device is connected to the second end of the first switching unit; the first end of the fourth switching device is connected to the first end of the second switching unit through the corresponding eighth connection structure, and the second end of the fourth switching device is connected to the second end of the second switching unit; the first end of the fifth switching device is connected to the input terminal through the ninth connection structure, and the second end of the fifth switching device is connected to the output terminal through the tenth connection structure; where n is a positive integer; the seventh connection structure and the eighth connection structure are symmetrical.

[0009] Optionally, the switching device includes an IGCT.

[0010] Optionally, multiple switching devices may be devices of the same model.

[0011] Optionally, the power switching circuit also includes a freewheeling module; the first end of the freewheeling module is connected to the input end, and the second end of the freewheeling module is connected to the output end.

[0012] Optionally, the freewheeling module includes at least one diode; the negative terminal of the diode is connected to the input terminal, and the positive terminal of the diode is connected to the output terminal.

[0013] Optionally, the power switching circuit also includes a voltage equalization module; the first end of the voltage equalization module is connected to the input end, and the second end of the voltage equalization module is connected to the output end.

[0014] Optionally, the voltage equalization module includes a resistor and a capacitor; the first end of the resistor is connected to the input terminal, and the second end of the resistor is connected to the output terminal; the first end of the capacitor is connected to the input terminal, and the second end of the capacitor is connected to the output terminal.

[0015] Optionally, the power switching circuit also includes a clamping module; the first end of the clamping module is connected to the input end, and the second end of the clamping module is connected to the first end of the voltage equalization module.

[0016] This disclosure provides a power switching circuit based on parallel connection of switching devices. The power switching circuit includes a connection structure and a switching module. The connection structure includes a first connection structure, a second connection structure, a third connection structure, and a fourth connection structure. The switching module includes a first switching unit and a second switching unit. The first connection structure is connected between a first terminal and an input terminal of the first switching unit; the second connection structure is connected between a first terminal and an input terminal of the second switching unit; the third connection structure is connected between a second terminal and an output terminal of the first switching unit; and the fourth connection structure is connected between a second terminal and an output terminal of the second switching unit. The first and second switching units include the same number of switching devices, and the connection structures meet at least one of the following conditions: the first connection structure is symmetrical to the second connection structure, and the third connection structure is symmetrical to the fourth connection structure. This disclosure achieves dynamic current balancing between the first and second switching units by setting the same number of switching devices in the first and second switching units, and by making the first and second connection structures symmetrical, and the third and fourth connection structures symmetrical. The symmetry between the first and second connection structures ensures that the stray inductances on the paths from the input terminal to the first and second switching units are the same, and the symmetry between the third and fourth connection structures ensures that the stray inductances on the paths from the first and second switching units to the output terminal are the same. Therefore, during the conduction or cutoff of the first and second switching units, the branches where the first and second switching units are located have the same current change, thus achieving dynamic current balancing between the first and second switching units and improving the current sharing capability of the power switching circuit. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 is a schematic diagram of a power switching circuit based on parallel switching devices provided in an embodiment of this disclosure.

[0019] Figure 2 is a schematic diagram of another power switching circuit based on parallel connection of switching devices provided in an embodiment of this disclosure.

[0020] Figure 3 is a schematic diagram of the structure of a switch module provided in an embodiment of this disclosure.

[0021] Figure 4 is a schematic diagram of another power switching circuit based on parallel switching devices provided in an embodiment of this disclosure.

[0022] Figure 5 is an experimental waveform diagram provided in an embodiment of this disclosure.

[0023] Figure 6 is a schematic diagram of the electrical connection structure of a switch module provided in an embodiment of this disclosure. Detailed Implementation

[0024] The features and exemplary embodiments of various aspects of this application will now be described in detail. Numerous specific details are set forth in the following detailed description in order to provide a comprehensive understanding of this application. However, it will be apparent to those skilled in the art that this application can be implemented without some of these specific details. The following description of embodiments is merely intended to provide a better understanding of this application by illustrating examples thereof.

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The embodiments will now be described in detail with reference to the accompanying drawings.

[0026] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0027] It should be understood that when describing the structure of a component, when referring to a layer or region as being "above" or "on top of" another layer or region, it can mean that it is directly above the other layer or region, or that it contains other layers or regions between it and the other layer or region. Furthermore, if the component is flipped over, that layer or region will be located "below" or "under" the other layer or region.

[0028] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0029] In the embodiments of this application, the term "electrical connection" can refer to a direct electrical connection between two components, or it can refer to an electrical connection between two components via one or more other components.

[0030] In the embodiments of this application, the first node, the second node, and the third node are defined only for the convenience of describing the circuit structure, and the first node, the second node, and the third node are not actual circuit units.

[0031] Various modifications and variations can be made to this application without departing from its spirit or scope, which will be apparent to those skilled in the art. Therefore, this application is intended to cover modifications and variations falling within the scope of the corresponding claims (the claimed technical solutions) and their equivalents. It should be noted that the implementation methods provided in the embodiments of this application can be combined with each other without contradiction.

[0032] Modular multilevel converters (MMCs) have become the most mature topology for flexible DC transmission due to their excellent waveform quality, modular structure, and easy scalability. As a key component of the MCC commutation arm, the performance of the power switching module directly affects the MMC's safe operating boundary and dynamic response capability. In conventional technologies, power switching circuits typically use multiple devices connected in parallel to increase the module's current capacity. However, due to insufficient current sharing capability, power switching circuits are prone to current unevenness during dynamic operation. This can lead to stress concentration, temperature rise deviation, efficiency degradation, and even device failure or damage.

[0033] Therefore, how to improve the current sharing capability of power switching circuits has become a technical problem that urgently needs to be solved by those skilled in the art.

[0034] Therefore, this disclosure provides a power switching circuit based on parallel connection of switching devices. By setting the first connection structure to be symmetrical with the second connection structure, and the third connection structure to be symmetrical with the fourth connection structure, the connection structure between the first switching unit and the second switching unit is made symmetrical, thereby realizing dynamic current balance between the first switching unit and the second switching unit and improving the current sharing capability of the power switching circuit.

[0035] The embodiments will now be described in detail with reference to the accompanying drawings.

[0036] Figure 1 is a schematic diagram of a power switching circuit based on parallel connection of switching devices provided in an embodiment of this disclosure. As shown in Figure 1, the power switching circuit includes: a connection structure and a switching module 20.

[0037] The connection structure includes a first connection structure 101, a second connection structure 102, a third connection structure 103, and a fourth connection structure 104.

[0038] The switch module 20 includes a first switch unit 21 and a second switch unit 22.

[0039] The first connection structure 101 is connected between the first end and the input end 31 of the first switching unit 21.

[0040] The second connection structure 102 is connected between the first end and the input end 31 of the second switching unit 22.

[0041] The third connection structure 103 is connected between the second end and the output end 32 of the first switching unit 21.

[0042] The fourth connection structure 104 is connected between the second end of the second switch unit 22 and the output end 32.

[0043] The first switching unit 21 and the second switching unit 22 include the same number of switching devices.

[0044] For example, the first switching unit 21 and the second switching unit 22 are connected in parallel, thereby improving the current-carrying capacity of the power switching circuit. Furthermore, both the first switching unit 21 and the second switching unit 22 include at least one switching device. When multiple switching devices are included in the first switching unit 21 and the second switching unit 22, these multiple switching devices can be connected in parallel, thereby improving the current-carrying capacity of each of the first switching unit 21 and the second switching unit 22, and thus further improving the current-carrying capacity of the power switching circuit. Alternatively, the multiple switching devices can be connected in series, thereby improving the high-voltage withstand capability of each of the first switching unit 21 and the second switching unit 22, and thus further improving the high-voltage withstand capability of the power switching circuit.

[0045] Furthermore, in order to minimize the impact of differences in the turn-on and turn-off characteristics between various switching devices on dynamic current balancing, it is necessary to test and screen the turn-on and turn-off delays of the switching devices and match them. In the same switching module, switching devices with smaller turn-off delay time deviations should be selected and connected in parallel to improve the dynamic current sharing performance of the switching module.

[0046] The first connecting structure 101, the second connecting structure 102, the third connecting structure 103, and the fourth connecting structure 104 meet at least one of the following conditions: the first connecting structure 101 is symmetrical to the second connecting structure 102, and the third connecting structure 103 is symmetrical to the fourth connecting structure 104.

[0047] For example, the symmetry between the first connection structure 101 and the second connection structure 102 means that the first connection structure 101 and the second connection structure 102 have conductive paths of the same length, and the conductive paths of the two are axially symmetrical. The symmetry between the third connection structure 103 and the fourth connection structure 104 means that the third connection structure 103 and the fourth connection structure 104 have conductive paths of the same length, and the conductive paths of the two are axially symmetrical.

[0048] The first switching unit 21 and the second switching unit 22 are provided with the same number of switching devices of the same model.

[0049] The first connecting structure 101, the second connecting structure 102, the third connecting structure 103, and the fourth connecting structure 104 may be such that only the first connecting structure 101 and the second connecting structure 102 are symmetrical, while the third connecting structure 103 and the fourth connecting structure 104 are asymmetrical. This allows the first switching unit 21 and the second switching unit 22 to have the same circuit connection structure with the input terminal. The first connection structure 101 and the second connection structure 102 are the same connection structure in the power switching circuit, only their positions are different. The first connection structure 101 and the second connection structure 102 can be, for example, copper busbars in a printed circuit board. Therefore, if the first connection structure 101 and the second connection structure 102 have the same length and are symmetrically positioned, then the first connection structure 101 and the second connection structure 102 will have the same stray inductance. That is, the stray inductance between the first switching unit 21 and the input terminal 31 is the same as the stray inductance between the second switching unit 22 and the input terminal 31. This ensures that the first switching unit 21 and the second switching unit 22 input the same dynamic current during the conduction or turn-off process, thus achieving dynamic current balance between the first switching unit 21 and the second switching unit 22.

[0050] The first connecting structure 101, the second connecting structure 102, the third connecting structure 103, and the fourth connecting structure 104 can also be such that the first connecting structure 101 and the second connecting structure 102 are asymmetrical, and the third connecting structure 103 and the fourth connecting structure 104 are symmetrical. This allows the first switching unit 21 and the second switching unit 22 to have the same circuit connection structure with the output terminal. The third connection structure 103 and the fourth connection structure 104 are the same connection structure in the power switching circuit, only their positions are different. The third connection structure 103 and the fourth connection structure 104 can be, for example, copper busbars in a printed circuit board. Therefore, if the third connection structure 103 and the fourth connection structure 104 have the same length and are symmetrically positioned, then the third connection structure 103 and the fourth connection structure 104 will have the same stray inductance. That is, the stray inductance between the first switching unit 21 and the output terminal 32 is the same as the stray inductance between the second switching unit 22 and the output terminal 32. This ensures that the first switching unit 21 and the second switching unit 22 output the same dynamic current during the conduction or turn-off process, thus achieving dynamic current balance between the first switching unit 21 and the second switching unit 22.

[0051] The first connection structure 101, the second connection structure 102, the third connection structure 103, and the fourth connection structure 104 can also be symmetrical between the first connection structure 101 and the second connection structure 102, and between the third connection structure 103 and the fourth connection structure 104. This allows the first switching unit 21 and the second switching unit 22 to have the same circuit connection structure with the input terminal, and the first switching unit 21 and the second switching unit 22 to have the same circuit connection structure with the output terminal. The first connection structure 101 and the second connection structure 102 are the same connection structure in the power switching circuit, and the third connection structure 103 and the fourth connection structure 104 are the same connection structure in the power switching circuit. The only difference between the first connection structure 101 and the second connection structure 102 and between the third connection structure 103 and the fourth connection structure 104 is their different positions. The first connection structure 101, the second connection structure 102, the third connection structure 103 and the fourth connection structure 104 can be, for example, copper busbars in a printed circuit board. Therefore, if the first connection structure 101 and the second connection structure 102 have the same length and are symmetrically positioned, then the first connection structure 101 and the second connection structure 102 will have the same stray inductance. That is, the stray inductance between the first switching unit 21 and the input terminal 31 is the same as the stray inductance between the second switching unit 22 and the input terminal 31. If the third connection structure 103 and the fourth connection structure 104 have the same length and are symmetrically positioned, then the third connection structure 103 and the fourth connection structure 104 will have the same stray inductance. That is, the stray inductance between the first switching unit 21 and the output terminal 32 is the same as the stray inductance between the second switching unit 22 and the output terminal 32. This ensures that during the on or off process of the first switching unit 21 and the second switching unit 22, the first switching unit 21 and the second switching unit 22 receive the same dynamic current and output the same dynamic current, thus achieving a balance between the dynamic currents input and output of the first switching unit 21 and the second switching unit 22.

[0052] This disclosure achieves dynamic current balancing between the first switching unit 21 and the second switching unit 22 by setting the same number of switching devices in the first switching unit 21 and the second switching unit 22, and by symmetrically aligning the first connection structure 101 with the second connection structure 102, and the third connection structure 103 with the fourth connection structure 104. The symmetry between the first connection structure 101 and the second connection structure 102 ensures that the stray inductances on the paths from the input terminal 31 to the first switching unit 21 and the second switching unit 22 are the same, and the symmetry between the third connection structure 103 and the fourth connection structure 104 ensures that the stray inductances on the paths from the first switching unit 21 and the second switching unit 22 to the output terminal 32 are the same. Therefore, during the conduction or cutoff of the first switching unit 21 and the second switching unit 22, the branches where the first switching unit 21 and the second switching unit 22 are located have the same current change, thereby achieving improved current sharing capability of the power switching circuit.

[0053] It should be noted that the above physical quantities are the same, such as the stray inductance between the first connection structure 101 and the second connection structure 102 being the same, and the dynamic current of the input and output being the same, etc. It should be understood that the difference between each physical quantity is within a reasonable threshold range. Specifically, when the difference between two physical quantities is within ±3%, or within the normal fluctuation range known to those skilled in the art, the physical quantities can be considered to be the same. Such a small difference is acceptable and does not have a substantial impact on the beneficial effects of the present invention.

[0054] In some embodiments, FIG2 is a schematic diagram of another power switching circuit based on parallel connection of switching devices provided in the present disclosure. As shown in FIG2, the switching module 20 includes 2n switching devices; the 2n switching devices include n first switching devices 211 and n second switching devices 221.

[0055] The first switching unit 21 includes n first switching devices 211; the second switching unit 22 includes n second switching devices 221; the connection structure also includes n fifth connection structures 105 and n sixth connection structures 106.

[0056] The first end of the first switching device 211 is connected to the first end of the first switching unit 21 through the corresponding fifth connection structure 105, and the second end of the first switching device 211 is connected to the second end of the first switching unit 21.

[0057] The first end of the second switching device 221 is connected to the first end of the second switching unit 22 through the corresponding sixth connection structure 106, and the second end of the second switching device 221 is connected to the second end of the second switching unit 22.

[0058] Where n is a positive integer; the fifth connection structure 105 is symmetrical to the sixth connection structure 106.

[0059] For example, the number of first switching devices 211 and second switching devices 221 is the same, so the number of fifth connection structures 105 and sixth connection structures 106 is the same. Figure 2 shows, for example, that the switch module 20 includes 4 switching devices, i.e., n is 2. The first switch unit 21 includes 2 first switching devices 211, the second switch unit 22 includes 2 second switching devices 221, and the connection structure also includes 2 fifth connection structures 105 and 2 sixth connection structures 106.

[0060] The first switching unit 21 has two first switching devices 211 connected in parallel, each connected to the first end of the first switching unit 21 via a corresponding fifth connection structure 105. The second switching unit 22 has two second switching devices 221 connected in parallel, each connected to the first end of the second switching unit 22 via a corresponding sixth connection structure 106. The first switching devices 211 and 221 are of the same model. Therefore, the fifth connection structure 105 and the sixth connection structure 106 are symmetrical, ensuring that the conductive path from the first end of the first switching unit 21 to each of the first switching devices 211 has the same length as the conductive path from the first end of the second switching unit 22 to each of the second switching devices 221, and that the conductive paths are axially symmetrical. Therefore, the stray inductance between the first terminal of the first switching unit 21 and each of the first switching devices 211 is the same as the stray inductance between the first terminal of the second switching unit 22 and each of the second switching devices 221. Thus, when the dynamic current input to each of the first switching devices 211 and each of the second switching devices 221 is the same, the dynamic current flowing through each of the first switching devices 211 and each of the second switching devices 221 is also the same, thereby achieving dynamic current balance between the first switching unit 21 and the second switching unit 22.

[0061] Furthermore, since the branch formed by the first connection structure 101, the first switching unit 21, and the third connection structure 103 is symmetrical with the branch formed by the second connection structure 102, the second switching unit 22, and the fourth connection structure 104, when multiple first switching devices 211 and multiple second switching devices 221 are turned on or off, the first switching unit 21 and the second switching unit 22 receive the same dynamic current due to the symmetry between the first connection structure 101 and the second connection structure 102. Because each first switching device 211 and each second switching device 221 receives the same dynamic current, and because each fifth connection structure 105 and each sixth connection structure 106 are symmetrical, the dynamic current flowing through the first switching unit 21 and the second switching unit 22 is the same. Finally, because the third connection structure 103 and the fourth connection structure 104 are symmetrical, the dynamic current output by the first switching unit 21 and the second switching unit 22 is also the same. Therefore, this disclosure achieves dynamic current balancing of the first switching unit 21 and the second switching unit 22, thereby improving the current sharing capability of the power switching circuit.

[0062] It should be noted that the diagram in Figure 2 showing the switch module 20 including 4 switching devices is for illustrative purposes only. The number of switching devices can be set according to the actual situation and is not specifically limited here.

[0063] It should be noted that the above physical quantities being the same should be understood as the difference between each physical quantity being within a reasonable threshold range. Specifically, when the difference between two physical quantities is, for example, within ±3%, or within the normal fluctuation range known to those skilled in the art, the physical quantities can be considered to be the same. Such a small difference is acceptable and does not have a substantial impact on the beneficial effects of the present invention.

[0064] Figure 3 is a schematic diagram of a switching module provided in an embodiment of this disclosure. As shown in Figure 3, the first connection structure 101 and the second connection structure 102 are symmetrical, therefore the stray inductances of the first connection structure 101 and the second connection structure 102 are the same, both being Ls1. The third connection structure 103 and the fourth connection structure 104 are symmetrical, therefore the stray inductances of the third connection structure 103 and the fourth connection structure 104 are the same, both being Ls3. The fifth connection structure 105 and the sixth connection structure 106 are symmetrical, therefore the stray inductances of the fifth connection structure 105 and the sixth connection structure 106 are the same, both being Ls2.

[0065] It should be noted that Ls1, Ls2, and Ls3 in Figure 3 are not specific inductors in the connection structure, but rather the inductance values ​​of stray inductors present in each connection structure, serving only as examples of one inductance parameter.

[0066] In some embodiments, FIG4 is a schematic diagram of another power switching circuit based on parallel connection of switching devices provided in this disclosure. As shown in FIG4, the switching module includes 2n+1 switching devices.

[0067] The 2n+1 switching devices include n third switching devices 212, n fourth switching devices 222, and 1 fifth switching device 23.

[0068] The first switching unit 21 includes n third switching devices 212; the second switching unit 22 includes n fourth switching devices 222; the connection structure also includes n seventh connection structures 107, n eighth connection structures 108, n ninth connection structures 109 and a tenth connection structure 110.

[0069] The first end of the third switching device 212 is connected to the first end of the first switching unit 21 through the corresponding seventh connection structure 107, and the second end of the third switching device 212 is connected to the second end of the first switching unit 21; the first end of the fourth switching device 222 is connected to the first end of the second switching unit 22 through the corresponding eighth connection structure 108, and the second end of the fourth switching device 222 is connected to the second end of the second switching unit 22; the first end of the fifth switching device 23 is connected to the input terminal 31 through the ninth connection structure 109, and the second end of the fifth switching device 23 is connected to the output terminal 32 through the tenth connection structure 110.

[0070] Where n is a positive integer; the seventh connection structure 107 is symmetrical to the eighth connection structure 108.

[0071] For example, the fifth switching device 23 is connected in parallel with the first switching unit 21 and the second switching unit 22 through the ninth connection structure 109 and the tenth connection structure 110. When both the first switching unit 21 and the second switching unit 22 have only one switching device, the seventh connection structure 107 is symmetrical with the first connection structure 101 or the second connection structure 102, and the eighth connection structure 108 is symmetrical with the third connection structure 103 or the fourth connection structure 104, which can achieve current balancing between the fifth switching device 23 and the first switching unit 21 and the second switching unit 22. When both the first switching unit 21 and the second switching unit 22 have more than one switching device, the fifth switching device 23 shuns part of the current input to its input terminal, and the remaining current is shunted to the first switching unit 21 and the second switching unit 22. Through the dynamic current balancing of the first switching unit 21 and the second switching unit 22, the current sharing capability of the power switching circuit is improved.

[0072] The number of third switching devices 212 and fourth switching devices 222 is the same, therefore the number of seventh connection structures 107 and eighth connection structures 108 is the same. Figure 4 shows an exemplary switch module 20 including 5 switching devices, i.e., n is 2. The first switch unit 21 includes 2 third switching devices 212, the second switch unit 22 includes 2 fourth switching devices 222, and the connection structure also includes 2 seventh connection structures 107 and 2 eighth connection structures 108.

[0073] In the first switching unit 21, there are two third switching devices 212 connected in parallel, each connected to the first end of the first switching unit 21 via a corresponding seventh connection structure 107. In the second switching unit 22, there are two fourth switching devices 222 connected in parallel, each connected to the first end of the second switching unit 22 via a corresponding eighth connection structure 108. The third switching devices 212 and the fourth switching devices 222 are of the same type. Therefore, the seventh connection structure 107 and the eighth connection structure 108 are symmetrical, ensuring that the conductive path from the first end of the first switching unit 21 to each of the third switching devices 212 has the same length as the conductive path from the first end of the second switching unit 22 to each of the second switching devices 221, and that the conductive paths are axially symmetrical. Therefore, the stray inductance between the first terminal of the first switching unit 21 and each of the third switching devices 212 is the same as the stray inductance between the first terminal of the second switching unit 22 and each of the second switching devices 221. Thus, when the dynamic current input to each of the third switching devices 212 and each of the second switching devices 221 is the same, the dynamic current flowing through each of the third switching devices 212 and each of the second switching devices 221 is also the same, thereby achieving dynamic current balance between the first switching unit 21 and the second switching unit 22.

[0074] Furthermore, since the branch formed by the first connection structure 101, the first switching unit 21, and the third connection structure 103 is symmetrical to the branch formed by the second connection structure 102, the second switching unit 22, and the fourth connection structure 104, when multiple third switching devices 212 and multiple second switching devices 221 are turned on or off, the first switching unit 21 and the second switching unit 22 receive the same dynamic current due to the symmetry between the first connection structure 101 and the second connection structure 102. Because each third switching device 212 and each second switching device 221 receives the same dynamic current, and because each seventh connection structure 107 and each eighth connection structure 108 are symmetrical, the dynamic current flowing through the first switching unit 21 and the second switching unit 22 is the same. Finally, because the third connection structure 103 is symmetrical to the fourth connection structure 104, the dynamic current output by the first switching unit 21 and the second switching unit 22 is also the same. Thus, this disclosure achieves dynamic current balancing between the first switching unit 21 and the second switching unit 22.

[0075] It should be noted that the five switching devices shown in Figure 4 for the switch module 20 are only examples. The number of switching devices can be set according to the actual situation and is not specifically limited here.

[0076] It should be noted that the above physical quantities being the same should be understood as the difference between each physical quantity being within a reasonable threshold range. Specifically, when the difference between two physical quantities is, for example, within ±3%, or within the normal fluctuation range known to those skilled in the art, the physical quantities can be considered to be the same. Such a small difference is acceptable and does not have a substantial impact on the beneficial effects of the present invention.

[0077] In some embodiments, continuing to refer to Figures 2 and 4, the switching device includes an integrated gate-commutated thyristor (IGCT).

[0078] For example, IGCTs have high withstand voltage characteristics. Therefore, using IGCTs for each switching device in a switching module can improve the high voltage withstand capability of the switching module, thereby improving the high voltage withstand capability of the power switching circuit. Furthermore, the IGCT should be selected one whose on-state voltage drop characteristics exhibit a positive temperature coefficient at larger currents, such as more than half of the IGCT's rated current, to ensure current balance among the parallel switching devices when the power switching circuit operates near its rated current.

[0079] Based on the power switch circuit corresponding to Figure 2, with all four switching devices using IGCTs, the rated voltage of the power switch circuit is 6500V, and the maximum turn-off current is 3800A. Figure 5 is an experimental waveform diagram provided by an embodiment of this disclosure. As shown in Figure 5, the waveform diagram obtained after a large current pulse experiment based on the power switch circuit corresponding to Figure 2 shows that the power switch circuit provided by this disclosure can successfully achieve turn-off when the maximum current is 11kA. Among them, the maximum current value of the four IGCTs is 3.05kA, and the maximum current imbalance (the deviation between the maximum current and the average value) is 11%, which verifies the effectiveness and engineering feasibility of this disclosure.

[0080] Figure 6 is a schematic diagram of the electrical connection structure of a switch module provided in an embodiment of this disclosure. As shown in Figure 6, heat sinks 24 are connected to both ends of the IGCT, and insulating blocks 25 are provided between adjacent heat sinks 24. The heat sinks 24 are used to dissipate heat from the IGCT, and the insulating blocks 25 are used to prevent damage caused by excessive current flowing through the IGCT due to short circuits between adjacent heat sinks 24.

[0081] In some embodiments, the multiple switching devices are devices of the same model.

[0082] Specifically, all the switching devices are of the same model and from the same batch, so their electrical properties are similar. After the switching devices are turned on or off, the static current flowing through them is the same, which ensures the balance of static current among the switching devices and thus improves the current sharing capability of the power switching circuit.

[0083] In some embodiments, continuing to refer to Figures 2 and 4, the power switching circuit further includes a freewheeling module 40.

[0084] The first end of the current continuing module 40 is connected to the input end 31, and the second end of the current continuing module 40 is connected to the output end 32.

[0085] Specifically, the freewheeling module 40 provides a freewheeling path to the circuit when the first switching unit 21 and the second switching unit 22 are disconnected, thereby preventing peak voltage from damaging the first switching unit 21 and the second switching unit 22. Furthermore, the freewheeling module 40 also ensures that the current in the circuit will not be suddenly interrupted when the first switching unit 21 and the second switching unit 22 switch between their on and off states, resulting in a smooth current waveform.

[0086] In some embodiments, the freewheeling module 40 includes at least one diode D1.

[0087] For example, the number of diodes D1 may be the same as or different from the number of switching devices. For instance, the switching module may include two switching devices, and the freewheeling module 40 may include one diode D1, or it may include two or three diodes D1.

[0088] Referring to Figures 2 and 4, the negative terminal of diode D1 is connected to input terminal 31, and the positive terminal of diode D1 is connected to output terminal 32.

[0089] For example, Figures 2 and 4 illustrate at least one diode D1 comprising four diodes D1, with a connection structure including an eleventh connection structure 111, a twelfth connection structure 112, a thirteenth connection structure 113, and a fourteenth connection structure 114. The number of twelfth connection structures 112 and thirteenth connection structures 113 is the same as the number of diodes D1. The negative terminal of diode D1 is connected to the eleventh connection structure 111 via the corresponding twelfth connection structure 112. The first end of the eleventh connection structure 111 is connected to the input terminal 31. The positive terminal of diode D1 is connected to the fourteenth connection structure 114 via the corresponding thirteenth connection structure 113. The second end of the fourteenth connection structure 114 is connected to the output terminal 32. The twelfth connection structures 112 of each diode D1 are symmetrical to each other, and the thirteenth connection structures 113 of each diode D1 are symmetrical to each other. Furthermore, all diodes D1 are of the same model and from the same batch. Because the thirteenth connection structures 113 of each diode D1 are symmetrical, the stray inductance between the positive terminal of each diode D1 and the first end of the fourteenth connection structure 114 is the same, resulting in the same dynamic current flowing from the first end of the fourteenth connection structure 114 to each diode D1. Since all diodes D1 are of the same model and batch, the dynamic current flowing through each diode D1 is also the same. Furthermore, because the twelfth connection structures 112 of each diode D1 are symmetrical, the stray inductance between the negative terminal of each diode D1 and the second end of the eleventh connection structure 111 is the same, resulting in the same dynamic current flowing from the negative terminal of each diode D1 to the second end of the eleventh connection structure 111. Therefore, this disclosure enables dynamic current balancing among the diodes D1 within the freewheeling module 40, thereby improving the current sharing capability of the power switching circuit.

[0090] Furthermore, diode D1 should be selected that exhibits a positive temperature coefficient characteristic at larger currents, such as more than half of the rated current of diode D1, to ensure current balance among the parallel switching devices when the power switching circuit operates near the rated current.

[0091] Referring again to Figure 6, a heat sink 24 is connected to both ends of diode D1, and an insulating block 25 is provided between adjacent heat sinks 24. The heat sink 24 is used to dissipate heat from diode D1, and the insulating block 25 is used to prevent damage to diode D1 due to excessive current flowing through it caused by a short circuit between adjacent heat sinks 24.

[0092] In some embodiments, referring again to Figures 2 and 4, the power switching circuit further includes a voltage equalization module 50.

[0093] The first end of the voltage equalization module 50 is connected to the input end 31, and the second end of the voltage equalization module 50 is connected to the output end 32.

[0094] Specifically, the voltage equalization module 50 is used to perform static voltage equalization and dynamic voltage equalization when the power switching circuit is connected in series with other power switching circuits in the MMC.

[0095] The voltage equalization module includes a resistor R1 and a capacitor C1.

[0096] The first end of resistor R1 is connected to the input terminal 31, and the second end of resistor R1 is connected to the output terminal 32.

[0097] The first end of capacitor C1 is connected to the input terminal 31, and the second end of capacitor C1 is connected to the output terminal 32.

[0098] Specifically, resistor R1 is used for static voltage equalization when the power switching circuit is connected in series with other power switching circuits in the MMC. Capacitor C1 is used for self-powering the secondary circuit of the power switching circuit and for dynamic voltage equalization when the power switching circuit is connected in series with other power switching circuits in the MMC. Capacitor C1 is typically in the range of tens to hundreds of microfarads.

[0099] In some embodiments, referring again to Figures 2 and 4, the power switch circuit further includes a clamping module 60; a first end of the clamping module 60 is connected to the input terminal 31, and a second end of the clamping module 60 is connected to the first end of the voltage equalization module 50.

[0100] For example, the clamping module 60 includes a clamping diode D2, the positive terminal of which is connected to the input terminal 31, and the negative terminal of which is connected to the first terminal of the voltage equalization module 50. The clamping diode D2 is used to clamp the voltage of the switching device, and since the effective current of the clamping diode D2 during operation is extremely small, a device with a small current rating is selected. The current rating of the clamping diode D2 is typically less than one-tenth of the current rating of the switching device.

[0101] The above are merely specific embodiments of this disclosure, enabling those skilled in the art to understand or implement this disclosure. Various modifications to these embodiments will be readily 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 this disclosure. Therefore, this disclosure is not to be limited to these embodiments, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power switching circuit based on parallel connection of switching devices, characterized in that, The power switching circuit includes: a connection structure, including a first connection structure, a second connection structure, a third connection structure, and a fourth connection structure; a switching module, including a first switching unit and a second switching unit; the first connection structure is connected between a first end and an input end of the first switching unit; the second connection structure is connected between a first end and an input end of the second switching unit; the third connection structure is connected between a second end and an output end of the first switching unit; and the fourth connection structure is connected between a second end and an output end of the second switching unit; wherein the first switching unit and the second switching unit include the same number of switching devices, and the connection structure meets at least one of the following conditions: the first connection structure is symmetrical to the second connection structure, and the third connection structure is symmetrical to the fourth connection structure.

2. The power switching circuit according to claim 1, characterized in that, The switching module includes 2n switching devices; the 2n switching devices include n first switching devices and n second switching devices; the first switching unit includes n first switching devices; the second switching unit includes n second switching devices; the connection structure further includes n fifth connection structures and n sixth connection structures; the first end of the first switching device is connected to the first end of the first switching unit through the corresponding fifth connection structure, and the second end of the first switching device is connected to the second end of the first switching unit; the first end of the second switching device is connected to the first end of the second switching unit through the corresponding sixth connection structure, and the second end of the second switching device is connected to the second end of the second switching unit; wherein, n is a positive integer; the fifth connection structure and the sixth connection structure are symmetrical.

3. The power switching circuit according to claim 1, characterized in that, The switching module includes 2n+1 switching devices; the 2n+1 switching devices include n third switching devices, n fourth switching devices, and 1 fifth switching device; the first switching unit includes n third switching devices; the second switching unit includes n fourth switching devices; the connection structure further includes n seventh connection structures, n eighth connection structures, ninth connection structures, and tenth connection structures; the first end of the third switching device is connected to the first end of the first switching unit through the corresponding seventh connection structure, and the second end of the third switching device is connected to the second end of the first switching unit; the first end of the fourth switching device is connected to the first end of the second switching unit through the corresponding eighth connection structure, and the second end of the fourth switching device is connected to the second end of the second switching unit; the first end of the fifth switching device is connected to the input terminal through the ninth connection structure, and the second end of the fifth switching device is connected to the output terminal through the tenth connection structure; wherein, n is a positive integer; the seventh connection structure and the eighth connection structure are symmetrical.

4. The power switching circuit according to any one of claims 1-3, characterized in that, The switching device includes an IGCT.

5. The power switching circuit according to any one of claims 1-3, characterized in that, The multiple switching devices are devices of the same model.

6. The power switching circuit according to claim 1, characterized in that, The power switching circuit further includes a freewheeling module; the first end of the freewheeling module is connected to the input end, and the second end of the freewheeling module is connected to the output end.

7. The power switching circuit according to claim 6, characterized in that, The freewheeling module includes at least one diode; the negative terminal of the diode is connected to the input terminal, and the positive terminal of the diode is connected to the output terminal.

8. The power switching circuit according to claim 1, characterized in that, The power switching circuit also includes a voltage equalization module; the first end of the voltage equalization module is connected to the input end, and the second end of the voltage equalization module is connected to the output end.

9. The power switching circuit according to claim 8, characterized in that, The voltage equalization module includes a resistor and a capacitor; the first end of the resistor is connected to the input terminal, and the second end of the resistor is connected to the output terminal; the first end of the capacitor is connected to the input terminal, and the second end of the capacitor is connected to the output terminal.

10. The power switching circuit according to claim 8, characterized in that, The power switch circuit also includes a clamping module; the first end of the clamping module is connected to the input end, and the second end of the clamping module is connected to the first end of the voltage equalization module.

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