Power module and modular multilevel converter

Abstract

The invention discloses a power module and a modular multilevel converter, and relates to the technical field of direct current transmission. The power module comprises a supporting capacitor, a clamping module, a half-bridge module and an auxiliary switch module. The clamping module comprises a clamping capacitor, the first end of the clamping capacitor is electrically connected with the second node, and the second end of the clamping capacitor is electrically connected with the second end of the clamping module; the first end of the half-bridge module is electrically connected with the first node, and the second end of the half-bridge module is electrically connected with the second end of the clamping module to the third node; the first end of the auxiliary switch module is electrically connected with the third node, the second end of the auxiliary switch module is electrically connected with the second node, and an auxiliary switch unit in the auxiliary switch module comprises an auxiliary power switch and an auxiliary diode; the midpoint of the bridge arm of the half-bridge module is electrically connected with the first end of the output port of the power module, and the second end of the auxiliary switch module is electrically connected with the second end of the output port of the power module. According to the embodiment of the invention, the fault clearing efficiency can be improved, and the loss is low.

Description

Technical Field

[0001] This application belongs to the field of DC power transmission technology, and in particular relates to a power module and a modular multilevel converter. Background Technology

[0002] Flexible DC-DC converter technology is a key technology for power system transformation. Among flexible DC-DC converter technologies, the Modular Multilevel Converter (MMC) exhibits advantages such as strong voltage scalability, high output waveform quality, and high power output capability due to its modular series connection. The power module of the MMC, as its most basic power unit, is formed by connecting various modules in series to create a single-phase bridge arm. The current-carrying capacity of the selected devices directly determines the upper limit of the system capacity. Power modules using integrated gate-commutated thyristors (IGCTs) not only have higher operating efficiency but also short-term overload operation capability.

[0003] With the continuous improvement of transmission distance and capacity, overhead lines have shown significant advantages over cable transmission in terms of economy and construction cost, strongly supporting the construction of ultra-high voltage flexible DC transmission projects. However, overhead lines are usually located in remote areas, and due to lightning strikes, pollution, and trees, bipolar short-circuit faults frequently occur on DC overhead lines. These faults generate extremely large DC-side currents, and due to the presence of DC-side inductance, the cost of interrupting them using circuit breakers is extremely high. Modular multilevel converters need to utilize their own topology and the capacitance of each power module in the converter to have corresponding DC line current absorption capabilities to achieve rapid DC-side fault clearing. However, at present, the industry still urgently needs a power module with rapid DC-side fault clearing capabilities to reliably ensure the safe and stable operation of the converter. Summary of the Invention

[0004] This application provides a power module and a modular multilevel converter that can improve fault clearing efficiency and reduce losses.

[0005] In a first aspect, embodiments of this application provide a power module, which includes a support capacitor, a clamping module, a half-bridge module, and an auxiliary switching module; The first end of the clamping module is electrically connected to the first pole of the supporting capacitor, the second end of the clamping module is electrically connected to the second end of the supporting capacitor, and the third end of the clamping module is electrically connected to the first node. The clamping module includes a clamping capacitor, the first end of which is electrically connected to the second node, and the second end of which is electrically connected to the second end of the clamping module. The first end of the half-bridge module is electrically connected to the first node, and the second end of the half-bridge module is electrically connected to the second end of the clamping module and the third node. The first terminal of the auxiliary switch module is electrically connected to the third node, and the second terminal of the auxiliary switch module is electrically connected to the second node. The auxiliary switch module includes at least one auxiliary switch unit, which includes an auxiliary power switch and an auxiliary diode connected in reverse parallel with the auxiliary power switch. The half-bridge module includes a bridge arm midpoint, which is electrically connected to the first end of the output port of the power module, and the second end of the auxiliary switch module is electrically connected to the second end of the output port of the power module.

[0006] In some possible implementations, the power module further includes: A unidirectional conduction module, the first end of which is electrically connected to the second end of the auxiliary switch module, and the second end of which is electrically connected to the second node. The second terminal of the auxiliary switch module is electrically connected to the second node via a unidirectional conduction module. The current flow direction of the unidirectional conduction module is from the second terminal of the auxiliary switch module to the second node.

[0007] In some possible implementations, the one-way conduction module includes: At least one target diode, the anode of any target diode is electrically connected to the second terminal of the auxiliary switching module, and the cathode of the target diode is electrically connected to the second node; The second terminal of the auxiliary switch module is electrically connected to the second node via the target diode.

[0008] In some possible implementations, the power module further includes: An overvoltage protection device, wherein the first terminal of the overvoltage protection device is electrically connected to the first terminal of a clamping capacitor, and the second terminal of the overvoltage protection device is electrically connected to the second terminal of a clamping capacitor; Overvoltage protection devices are used to provide a shunt path when the voltage difference across the clamping capacitor exceeds the overvoltage threshold.

[0009] In some possible implementations, the overvoltage protection device includes a metal oxide varistor.

[0010] In some possible implementations, the clamping module may also include an anode reactor, a clamping diode, and a clamping resistor; The first end of the anode reactor and the first end of the clamping resistor are electrically connected to the first pole of the supporting capacitor, respectively. The second end of the anode reactor is electrically connected to the anode of the clamping diode at the first node, and the cathode of the clamping diode and the second end of the clamping resistor are electrically connected to the second node, respectively.

[0011] In some possible implementations, the half-bridge module includes a first switching module and a second switching module, wherein the first switching module includes at least one first switching unit and the second switching module includes at least one second switching unit. The first end of the first switch module is electrically connected to the third end of the clamping module, the second end of the first switch module and the first end of the second switch module are electrically connected to the midpoint of the bridge arm, and the second end of the second switch module is electrically connected to the third node.

[0012] In some possible implementations, the first switching unit includes a first power switch and a first diode connected in reverse parallel with the first power switch; The second switching unit includes a second power switch and a second diode connected in reverse parallel with the second power switch.

[0013] In some possible implementations, the power module is configured as follows: In response to the power module being in the active state, the first switch module and the auxiliary switch module are turned on, and the second switch module is turned off; and / or, In response to the power module being in the off state, the second switch module and the auxiliary switch module are turned on, and the first switch module is turned off; and / or, In response to the power module being in a locked state, the first switch module, the second switch module, and the auxiliary switch module are all turned off.

[0014] Based on the same inventive concept, embodiments of this application also provide a modular multilevel converter, which includes at least one power module as described in any of the first aspects of this application.

[0015] This application discloses a power module and a modular multilevel converter. The power module includes a support capacitor, a clamping module, a half-bridge module, and an auxiliary switching module. A first terminal of the clamping module is electrically connected to a first terminal of the support capacitor, a second terminal of the clamping module is electrically connected to a second terminal of the support capacitor, and a third terminal of the clamping module is electrically connected to a first node. The clamping module includes a clamping capacitor, the first terminal of which is electrically connected to a second node, and the second terminal of which is electrically connected to a second terminal of the clamping module. A first terminal of the half-bridge module is electrically connected to the first node, and a second terminal of the half-bridge module is electrically connected to the second terminal of the clamping module and to the third node. A first terminal of the auxiliary switching module is electrically connected to the third node, and a second terminal of the auxiliary switching module is electrically connected to the second node. The auxiliary switching module includes at least one auxiliary switching unit, which includes an auxiliary power switch and an auxiliary diode connected in anti-parallel to the auxiliary power switch. The half-bridge module includes a bridge arm midpoint, which is electrically connected to a first terminal of the output port of the power module, and the second terminal of the auxiliary switching module is electrically connected to a second terminal of the output port of the power module.

[0016] This application discloses a power module and a modular multilevel converter. The power module includes a support capacitor, a clamping module, a half-bridge module, and an auxiliary switching module. A first terminal of the clamping module is electrically connected to a first terminal of the support capacitor, a second terminal of the clamping module is electrically connected to a second terminal of the support capacitor, and a third terminal of the clamping module is electrically connected to a first node. The clamping module includes a clamping capacitor, the first terminal of which is electrically connected to a second node, and the second terminal of which is electrically connected to a second terminal of the clamping module. A first terminal of the half-bridge module is electrically connected to the first node, and a second terminal of the half-bridge module is electrically connected to the second terminal of the clamping module and to the third node. A first terminal of the auxiliary switching module is electrically connected to the third node, and a second terminal of the auxiliary switching module is electrically connected to the second node. The auxiliary switching module includes at least one auxiliary switching unit, which includes an auxiliary power switch and an auxiliary diode connected in anti-parallel to the auxiliary power switch. The half-bridge module includes a bridge arm midpoint, which is electrically connected to a first terminal of the output port of the power module, and the second terminal of the auxiliary switching module is electrically connected to a second terminal of the output port of the power module.

[0017] As described above, the power module and modular multilevel converter provided in this application have the following advantages. Firstly, in the event of a fault current on the DC side, the auxiliary switching module can provide a path for the fault current to flow to the clamping capacitor through the auxiliary power switch and its anti-parallel auxiliary diode in the auxiliary switching unit. This allows the clamping capacitor in the clamping module to absorb the fault current, achieving rapid fault clearing and reducing the impact of the fault current on the system. Simultaneously, using the clamping capacitor instead of the DC-side capacitor to absorb the fault current prevents overcharging of the power module, which could cause the power module to discharge and impact the system during system recovery. Secondly, the half-bridge module, as the core voltage output unit, works in conjunction with the auxiliary switching module. Under rated operating conditions, it does not significantly increase losses or costs compared to traditional half-bridge power modules, ensuring low losses and smooth power module state switching during normal operation. This provides an advantage over other full-bridge power modules with fault clearing capabilities. Therefore, this power module and modular multilevel converter, by adding an auxiliary switching module, achieves rapid fault clearing on the DC side without causing severe overvoltage to the power module. Furthermore, the collaborative operation of the half-bridge module and the auxiliary switching module ensures low losses during normal operation.

[0018] Furthermore, due to the low-loss and DC-side fault clearing capabilities of the aforementioned power modules, their application in modular multilevel converters offers several advantages. Firstly, the modular multilevel converter maintains high efficiency during normal operation, reducing energy consumption. Under rated operating conditions, it does not significantly increase losses or costs compared to traditional half-bridge power modules. Secondly, these power modules enable the converter to possess self-clearing capabilities for converter valves in the event of a DC-side fault. This allows for rapid response and fault clearing, reducing fault impact and ensuring the safe and stable operation of the converter. Thus, by employing these low-loss and DC-side fault clearing capabilities, the converter possesses the ability to quickly clear faults during DC-side faults. Moreover, it minimizes efficiency degradation during normal operation, improving the operating efficiency of the modular multilevel converter. This significantly enhances the performance and reliability of the modular multilevel converter, contributing to its safe and stable operation and providing reliable technical support for the development of flexible DC transmission systems. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of a power module provided in an embodiment of this application; Figure 2 This is a schematic diagram of the structure of a power module provided in another embodiment of this application; Figure 3 This is a schematic diagram illustrating the working principle of a power module provided in one embodiment of this application; Figure 4 This is a schematic diagram illustrating the working principle of a power module provided in another embodiment of this application; Figure 5 This is a schematic diagram illustrating the working principle of a power module provided in another embodiment of this application; Figure 6 This is a schematic diagram of the structure of a modular multilevel converter provided in one embodiment of this application. Detailed Implementation

[0021] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are intended only to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0022] It should be noted that, in this document, relational terms such as "first" and "second" are used only 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 other identical elements in the process, method, article, or apparatus that includes said element.

[0023] 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.

[0024] It should be noted that the transistors in the embodiments of this application can be either N-type or P-type transistors. For N-type transistors, the on-state level is high and the off-state level is low. That is, when the gate of an N-type transistor is high, its first and second terminals are connected; when the gate of an N-type transistor is low, its first and second terminals are off. For P-type transistors, the on-state level is low and the off-state level is high. That is, when the control terminal of a P-type transistor is low, its first and second terminals are connected; when the control terminal of a P-type transistor is high, its first and second terminals are off. In specific implementations, the gate of each transistor is used as its control terminal. Furthermore, depending on the signal and type of the gate of each transistor, its first terminal can be used as the source and its second terminal as the drain, or vice versa. No distinction is made here. Additionally, the on-state and off-state levels in the embodiments of this invention are general terms. The on-state level refers to any level that enables the transistor to conduct, and the off-state level refers to any level that enables the transistor to turn off / become off.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] Before describing the technical solutions provided in the embodiments of this application, in order to facilitate understanding of the embodiments of this application, this application first specifically explains the problems existing in the related technologies: As described in the background section, current modular multilevel converters need to utilize their own topology and the capacitors of each power module within the converter to possess corresponding DC line current absorption capabilities in order to achieve rapid DC-side fault clearing. Specifically, in existing flexible DC transmission converters, a scheme is typically adopted where all or part of the half-bridge power modules are replaced by full-bridge power modules. When a DC-side fault occurs, through a blocking mechanism, the full-bridge power modules provide a negative voltage to the DC side, causing energy in the line to transfer to the supporting capacitors of the full-bridge power modules, thereby clearing the DC-side fault.

[0029] However, such a solution has the following two problems: (1) The losses of the full-bridge power module are significantly higher than those of the half-bridge power module. Under normal operating conditions, since the full-bridge power module usually carries a series combination of two power devices in a full-bridge structure, its losses can be approximated as twice that of the half-bridge power module, which seriously degrades the operating efficiency of the modular multilevel converter. Therefore, the modular multilevel converter using the full-bridge power module has high losses and low operating efficiency.

[0030] (2) The way the full-bridge power module clears DC-side faults is by transferring line energy to the full-bridge power module. This causes the voltage of each full-bridge power module to deviate significantly from its rated value after absorption. When the modular multilevel converter resumes operation, it will generate a huge inrush current, which will seriously threaten the semiconductor devices in the converter valve. At the same time, it will also generate a huge capacitance overshoot (overvoltage) in the AC system. Although there are some additional treatment methods to suppress overvoltage, this method requires replacing more than 80% of the modules in the MMC with full-bridge power modules to achieve the same clearing efficiency as the blocking method. It is difficult to achieve a balance between rapid recovery and economy of the modular multilevel converter.

[0031] Therefore, compared with half-bridge power modules, full-bridge power modules have stronger fault clearing and voltage regulation capabilities, but they also bring higher losses and costs. Developing a power module with lower losses and DC-side fault clearing capabilities has become a pressing technical challenge. A power module with low losses and DC-side fault clearing capabilities is crucial for ensuring the safe and stable operation of modular multilevel converters.

[0032] In view of the above, in order to solve the problems of the prior art, embodiments of this application provide a power module and a modular multilevel converter, which have low loss and DC-side fault clearing capabilities. It should be noted that the embodiments provided in this application are not intended to limit the scope of this application.

[0033] The power module provided in the embodiments of this application will be described below.

[0034] Figure 1 A schematic diagram of the structure of a power module 100 provided in one embodiment of this application is shown. Figure 1 As shown, the power module 100 includes: a support capacitor C1, a clamping module 10, a half-bridge module 20, and an auxiliary switching module 30; The first end of the clamping module 10 is electrically connected to the first pole of the support capacitor C1, the second end of the clamping module 10 is electrically connected to the second end of the support capacitor C1, the third end of the clamping module 10 is electrically connected to the first node N1, the clamping module 10 includes a clamping capacitor Cs, the first end of the clamping capacitor Cs is electrically connected to the second node N2, and the second end of the clamping capacitor Cs is electrically connected to the second end of the clamping module 10. The first end of the half-bridge module 20 is electrically connected to the first node N1, and the second end of the half-bridge module 20 is electrically connected to the second end of the clamping module 10 and the third node N3. The first terminal of the auxiliary switch module 30 is electrically connected to the third node N3, and the second terminal of the auxiliary switch module 30 is electrically connected to the second node N2. The auxiliary switch module 30 includes at least one auxiliary switch unit 31, and the auxiliary switch unit 31 includes an auxiliary power switch T3 and an auxiliary diode D3 connected in reverse parallel with the auxiliary power switch T3. The half-bridge module 20 includes a bridge arm midpoint A, which is electrically connected to the first end of the output port of the power module 100, and the second end of the auxiliary switch module 30 is electrically connected to the second end of the output port of the power module 100.

[0035] Specifically, the power module 100 can be applied to the modular multilevel converter 1000, and the power module 100 can serve as the basic unit of the bridge arm of the modular multilevel converter 1000.

[0036] The aforementioned support capacitor C1 is used to stabilize the DC voltage and provide energy buffering. During the operation of the power module 100, the capacitor can store and release electrical energy, thereby balancing transient power fluctuations. Furthermore, the support capacitor C1, through its energy storage characteristics, can also maintain the stability of the DC bus voltage.

[0037] When applied to MMC, the support capacitor C1 serves as a voltage support in the power module 100. During normal operation, the voltage of the support capacitor C1 provides a reference for the output voltage of the power module 100. By controlling the charging and discharging process of the support capacitor C1, the power of the power module 100 can be regulated.

[0038] The clamping module 10 described above can be used to prevent overvoltage in the bridge arm portion of the half-bridge module 20 during device commutation, protecting the devices in the power module 100. The clamping module 10 includes clamping devices such as clamping capacitors Cs. Through the clamping capacitors Cs, the clamping module 10 can effectively clamp overvoltages in fault conditions, protecting the devices in the power module 100 from damage.

[0039] The aforementioned half-bridge module 20 typically consists of an upper half-bridge arm and a lower half-bridge arm, connected at a node known as the midpoint A of the bridge arm. The upper and lower half-bridge arms may include switching devices and their anti-parallel diodes to achieve positive and negative voltage switching.

[0040] During actual operation of the power module 100, the midpoint A of the bridge arm is electrically connected to the first end of the output port of the power module 100, and the second end of the auxiliary switch module 30 is electrically connected to the second end of the output port of the power module 100. The half-bridge module 20 can serve as the core voltage output unit, working in conjunction with the auxiliary switch module 30 to ensure low loss and smooth state switching of the power module 100 during normal operation.

[0041] Furthermore, please combine Figure 2 , Figure 2 This is a schematic diagram of the structure of a power module 100 provided in another embodiment of this application. For example... Figure 2 As shown, the auxiliary switching unit 31 includes an auxiliary power switch T3 and an auxiliary diode D3.

[0042] The auxiliary power switch T3 is, for example, a fully controlled power switch. The aforementioned fully controlled power switch can be selected from integrated gate commutated thyristors (IGCTs), insulated gate bipolar transistors (IGBTs), injection enhanced gate transistors (IEGTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), or gate turn-off thyristors (GTOs), etc., without strict limitations.

[0043] The auxiliary switch module 30 may include only one auxiliary switch unit 31, or it may include multiple auxiliary switch units 31 connected in series, parallel, or a combination of series and parallel connections. It should be noted that... Figure 2 The auxiliary switch module 30 in this paper is only a single auxiliary switch unit 31. However, in other embodiments, the auxiliary switch module 30 can also be implemented by a connection structure of multiple auxiliary switch units 31 connected in series, thereby improving the pressure resistance. This application does not strictly limit the specific topology of the auxiliary switch module 30.

[0044] The aforementioned auxiliary switch module 30, through the auxiliary power switch T3 in the auxiliary switch unit 31 and its anti-parallel auxiliary diode D3, helps to absorb fault current through the clamping capacitor Cs, thereby achieving rapid clearing. For example, in the event of a DC-side fault, the half-bridge module 20 is locked, and the fault current flows to the clamping capacitor Cs through the auxiliary diode D3 of the auxiliary switch module 30. The clamping capacitor Cs absorbs the fault current, thereby clamping the voltage to protect the devices from overvoltage damage.

[0045] This application discloses a power module 100 and a modular multilevel converter 1000. The power module 100 includes a support capacitor C1, a clamping module 10, a half-bridge module 20, and an auxiliary switching module 30. The first terminal of the clamping module 10 is electrically connected to the first terminal of the support capacitor C1, the second terminal of the clamping module 10 is electrically connected to the second terminal of the support capacitor C1, and the third terminal of the clamping module 10 is electrically connected to a first node N1. The clamping module 10 includes a clamping capacitor Cs, the first terminal of which is electrically connected to a second node N2, and the second terminal of which is electrically connected to the second terminal of the clamping module 10. The first terminal of the half-bridge module 20 is electrically connected to the first node N1, and the second terminal of the half-bridge module 20 is electrically connected to the second terminal of the clamping module 10 and the third node N3. The first terminal of the auxiliary switch module 30 is electrically connected to the third node N3, and the second terminal of the auxiliary switch module 30 is electrically connected to the second node N2. The auxiliary switch module 30 includes at least one auxiliary switch unit 31, which includes an auxiliary power switch T3 and an auxiliary diode D3 connected in anti-parallel to the auxiliary power switch T3. The half-bridge module 20 includes a bridge arm midpoint A, which is electrically connected to the first terminal of the output port of the power module 100. The second terminal of the auxiliary switch module 30 is electrically connected to the second terminal of the output port of the power module 100.

[0046] As described above, the power module 100 and modular multilevel converter provided in this application embodiment have the following advantages. Firstly, in the event of a fault current on the DC side, the clamping module 10, through the clamping capacitor Cs, can effectively clamp overvoltages and protect power devices from damage. The auxiliary switching module 30, through the auxiliary power switch T3 in the auxiliary switching unit 31 and its anti-parallel auxiliary diode D3, provides a path for the fault current to flow to the clamping capacitor Cs. This allows the clamping capacitor Cs in the clamping module 10 to absorb the fault current, achieving rapid fault clearing and reducing the impact of the fault current on the system. Simultaneously, using the clamping capacitor Cs instead of the DC-side capacitor to absorb the fault current prevents overcharging of the power module 100, which could cause the power module 100 to discharge and impact the system during system recovery. Secondly, the half-bridge module 20 works in conjunction with the auxiliary switching module 30. Under rated operating conditions, it does not significantly increase losses or costs compared to traditional half-bridge power modules, ensuring low losses and smooth state switching of the power module 100 during normal operation. This provides an advantage over other full-bridge power modules with fault clearing capabilities. Therefore, the power module 100 and the modular multilevel converter, by adding the auxiliary switch module 30, achieve the function of quickly clearing DC side faults without causing serious overvoltage to the power module 100. At the same time, through the coordinated work of the half-bridge module 20 and the auxiliary switch module 30, low loss can be guaranteed during normal operation.

[0047] Furthermore, because the aforementioned power module 100 possesses low loss and DC-side fault clearing capabilities, its application in modular multilevel converters offers several advantages. Firstly, the modular multilevel converter maintains high efficiency during normal operation, reducing converter energy consumption. Under rated operating conditions, it does not significantly increase losses or costs compared to traditional half-bridge power modules. Secondly, the power module 100 enables the converter to possess self-clearing capabilities for converter valves in the event of a DC-side fault. This allows for rapid response and fault clearing, reducing fault impact and ensuring the safe and stable operation of the converter. Thus, by employing the aforementioned power module with DC fault clearing capabilities and low loss, the converter possesses the ability to quickly clear faults during DC-side faults. Furthermore, it minimizes efficiency degradation during normal operation, improving the operating efficiency of the modular multilevel converter. This significantly enhances the performance and reliability of the modular multilevel converter, thereby contributing to its safe and stable operation.

[0048] Alternatively, according to some embodiments of this application, please continue to refer to... Figure 2 The power module 100 also includes: One-way conduction module 40, the first end of the one-way conduction module 40 is electrically connected to the second end of the auxiliary switch module 30, and the second end of the one-way conduction module 40 is electrically connected to the second node N2; The second end of the auxiliary switch module 30 is electrically connected to the second node N2 via the unidirectional conduction module 40. The current flow direction of the unidirectional conduction module 40 is from the second end of the auxiliary switch module 30 to the second node N2.

[0049] In this embodiment, by introducing a unidirectional conduction module 40, the power module 100 can effectively block the discharge path of the clamping capacitor Cs during normal operation, thereby maintaining the stable operation of the module. Specifically, the clamping capacitor Cs is mainly used to absorb transient overvoltages during normal operation, and its discharge may have a negative impact on the voltage stability of the power module 100.

[0050] Therefore, under normal operating conditions of the power module 100, the unidirectional conduction module 40 can block the discharge of the first end of the clamping capacitor Cs to the second end of the output port of the power module 100, which helps to maintain the stable operation of the power module 100 and avoids the discharge of the clamping capacitor Cs leading to a decrease in operating performance.

[0051] Optionally, according to some embodiments of this application, the one-way conduction module 40 includes: At least one target diode D4, the anode of any target diode D4 is electrically connected to the second terminal of the auxiliary switch module 30, and the cathode of the target diode D4 is electrically connected to the second node N2; The second terminal of the auxiliary switch module 30 is electrically connected to the second node N2 via the target diode D4.

[0052] In this embodiment, the unidirectional conduction module 40 is implemented by at least one target diode D4. This can fully realize the unidirectional conduction function while saving the system cost increase caused by adding a new module, thus optimizing cost-effectiveness.

[0053] In some examples, by connecting multiple target diodes D4 in parallel, the current carrying capacity along the path when fault current flows can be enhanced, preventing surge damage to the device when a single target diode D4 is connected. This also improves the overall fault tolerance of the power module 100, enhancing the overall performance and reliability of the system.

[0054] Optionally, according to some embodiments of this application, the power module 100 further includes: Overvoltage protection device 50, the first terminal of overvoltage protection device 50 is electrically connected to the first terminal of clamping capacitor Cs, and the second terminal of overvoltage protection device 50 is electrically connected to the second terminal of clamping capacitor Cs; The overvoltage protection device 50 is used to provide a shunt path when the voltage difference across the clamping capacitor Cs is greater than the overvoltage threshold.

[0055] The overvoltage protection device 50 is connected in parallel with the clamping capacitor Cs. When the voltage difference across the clamping capacitor Cs exceeds the overvoltage threshold, the overvoltage protection device 50 will conduct to absorb some of the current and release a small portion of the fault current through shunt, thereby reducing the voltage across the clamping capacitor Cs and preventing overvoltage damage to the clamping capacitor Cs. This helps maintain the long-term stable and reliable operation of the power module 100.

[0056] In a specific implementation, for example, when a DC-side fault occurs, the half-bridge module 20 is locked out, and the fault current flows to the clamping capacitor Cs through the auxiliary diode D3 in the auxiliary switching unit 31. The clamping capacitor Cs absorbs the fault current, thereby clamping the voltage to protect the devices from overvoltage damage.

[0057] In this situation, if the voltage exceeds the withstand capacity of the clamping capacitor Cs, the overvoltage protection device 50 will conduct, further clamping the voltage and protecting the device from overvoltage damage. Thus, through the synergistic effect of the clamping capacitor Cs and the overvoltage protection device 50, the fault current can be quickly absorbed, the DC-side fault cleared, and overvoltage caused by overcharging of the clamping capacitor Cs can be prevented.

[0058] In practical applications, the overvoltage protection device 50 can be a varistor, such as a metal oxide varistor M1 (MOV) or a silicon carbide varistor. Alternatively, the overvoltage protection device 50 can also be a surge arrester or other protection device, and the specific choice can be made flexibly according to actual needs and application scenarios.

[0059] Optionally, according to some embodiments of this application, the overvoltage protection device 50 includes a metal oxide varistor M1.

[0060] In this embodiment, when the voltage across the metal oxide varistor M1 (and the voltage across the clamping capacitor Cs) is at the normal operating voltage, the resistance of the metal oxide varistor M1 is very high, and the current is very small, almost negligible. When the voltage exceeds a certain threshold, the resistance of the metal oxide varistor M1 drops sharply, thus providing a shunt path for the fault current. This keeps the overvoltage of the clamping capacitor Cs within a safe range. Correspondingly, after absorbing the overvoltage energy, the metal oxide varistor M1 gradually returns to a high-resistance state, which helps the system return to normal operation.

[0061] It should be added that when higher energy absorption capacity and shunt capacity under overvoltage conditions are required, multiple metal oxide varistors M1 can be used in parallel. This can effectively protect the circuit devices from overvoltage damage, thereby helping to maintain the long-term stable and reliable operation of the power module 100.

[0062] Optionally, according to some embodiments of this application, the clamping module 10 further includes an anode reactance Ls, a clamping diode Ds, and a clamping resistor Rs; The first end of the anode reactance Ls and the first end of the clamping resistor Rs are electrically connected to the first pole of the supporting capacitor C1, respectively. The second end of the anode reactance Ls is electrically connected to the anode of the clamping diode Ds at the first node N1, and the cathode of the clamping diode Ds and the second end of the clamping resistor Rs are electrically connected to the second node N2, respectively.

[0063] The clamping module 10, through the synergistic clamping action of the anode reactance Ls, clamping diode Ds, and clamping resistor Rs, effectively limits overvoltage and protects the devices in the power module 100 from damage. Specifically, during the commutation transient, the anode reactance Ls limits the di / dt during the turn-on process of the power switch in the half-bridge module 20 or auxiliary switching module 30, thereby protecting the devices from overcurrent surges. The clamping diode Ds conducts during the reverse recovery phase of the anti-parallel diode corresponding to the power switch and when the power switch is turned off, connecting the clamping capacitor Cs into the circuit, thereby protecting the devices from overvoltage.

[0064] Specifically, when the power switch in the power module 100 is an IGCT, the IGCT, as a high-voltage, high-current power device, requires an effective clamping circuit to prevent overvoltage damage due to its fast switching characteristics. In this case, by setting this clamping circuit, the clamping protection of the circuit components can be effectively achieved. When other types of power switches are selected, such as IGBTs, the clamping circuit can also be configured as follows: Figure 2 The structure shown is configured to ensure the safe operation of the power module 100 and improve its reliability.

[0065] It should be noted that the topology used in the above clamping circuit is only an example topology, and there are many other topologies that can be used.

[0066] Optionally, according to some embodiments of this application, the half-bridge module 20 includes a first switch module and a second switch module, the first switch module including at least one first switch unit 21, and the second switch module including at least one second switch unit 22; The first end of the first switch module is electrically connected to the third end of the clamping module 10, the second end of the first switch module and the first end of the second switch module are electrically connected to the midpoint A of the bridge arm, and the second end of the second switch module is electrically connected to the third node N3.

[0067] In this embodiment, the first switch module may include only one first switch unit 21, or it may include multiple first switch units 21 connected in series, parallel, or a combination of series and parallel. The second switch module may include only one second switch unit 22, or it may include multiple second switch units 22 connected in series, parallel, or a combination of series and parallel.

[0068] During the actual operation of the power module 100, the switching of the power module 100 into, out of, and locked states can be achieved by the alternating conduction and shutdown of the first switching unit 21, the second switching unit 22, and the auxiliary switching unit 31, thereby realizing voltage and power regulation.

[0069] It should be noted that the half-bridge module 20 in the figure only uses a single first switch unit 21 as the upper half-bridge arm and a single second switch unit 22 as the lower half-bridge arm. However, in other embodiments, the above-mentioned bridge arms can also be implemented in the form of a switch valve string or other switch connection structures. This application does not strictly limit the specific topology of the half-bridge module 20.

[0070] Optionally, according to some embodiments of this application, the first switching unit 21 includes a first power switch T1 and a first diode D1 connected in reverse parallel with the first power switch T1; The second switching unit 22 includes a second power switch T2 and a second diode D2 connected in reverse parallel with the second power switch T2.

[0071] The first power switch T1 and the second power switch T2 mentioned above can be power switches, such as fully controllable power switches. Fully controllable power switches are gate turn-off thyristors, high-power transistors, power MOSFETs, or insulated-gate bipolar transistors.

[0072] During the actual operation of the power module 100, the switching of the power module 100's on, off, and locked states can be realized by alternating the conduction and cutoff of the first power switch T1, the second power switch T2, and the auxiliary power switch T3, combined with the freewheeling channel provided by the anti-parallel headphone tube, thereby achieving voltage and power regulation.

[0073] It should be noted that the half-bridge module 20 in the figure uses only a single switch unit as the upper or lower half-bridge arm. However, in other embodiments, the bridge arm can also be implemented in the form of a switch valve string or other switch connection structure. This application does not strictly limit the specific topology of the half-bridge module 20.

[0074] Please see below. Figure 3 , Figure 4 as well as Figure 5 , Figure 3This is a schematic diagram illustrating the working principle of a power module 100 provided in one embodiment of this application; Figure 4 This is a schematic diagram illustrating the working principle of a power module 100 provided in another embodiment of this application; Figure 5 This is a schematic diagram illustrating the working principle of a power module 100 according to another embodiment of this application. Optionally, according to some embodiments of this application, the power module 100 is configured as follows: In response to the power module 100 being in the active state, the first switch module and the auxiliary switch module 30 are turned on, and the second switch module is turned off; and / or, In response to the power module 100 being in the off state, the second switch module and the auxiliary switch module 30 are turned on, and the first switch module is turned off; and / or, In response to the power module 100 being in a locked state, the first switch module, the second switch module, and the auxiliary switch module 30 are all turned off.

[0075] Combination Figure 3 , Figure 4 as well as Figure 5 As shown, Figure 3 A schematic diagram showing the power module 100 in the activated state is shown. Figure 4 A schematic diagram showing the power module 100 in the cut-out state is shown. Figure 5 A schematic diagram is shown of the power module 100 in a locked state.

[0076] In this embodiment, combined with Figure 3 and Figure 4 As shown, during steady-state operation, the power module 100 operates in two states: on and off. The half-bridge module 20 and the auxiliary switching module 30 output the required voltage under the control of the power switching devices. Specifically, in... Figure 3 and Figure 4 In the diagram, the red dashed line represents the current inflow path, and the blue dashed line represents the current outflow path.

[0077] Specifically, such as Figure 3 As shown, when the power module 100 is in the active state, the first switch module and the auxiliary switch module 30 are turned on, and the second switch module is turned off. Referring to the path shown by the red dashed line, when current flows into the power module 100, it flows in from the first terminal of the power module 100's output port, passes sequentially through the first diode D1, the anode reactance Ls, the supporting capacitor C1, and the auxiliary power switch T3, and flows out from the first terminal of the power module 100's output port. Referring to the path shown by the blue dashed line, when current flows out of the power module 100, it starts from the second terminal of the power module 100's output port, passes sequentially through the auxiliary diode D3, the supporting capacitor C1, the anode reactance Ls, and the first power switch T1, and flows out from the second terminal of the power module 100's output port.

[0078] When power module 100 is in the off state, the second switch module and auxiliary switch module 30 are turned on, and the first switch module is turned off. As shown by the red dashed line, when current flows into power module 100, it enters from the first terminal of the power module 100's output port, passes sequentially through the second power switch T2 and the auxiliary power switch T3, and exits from the first terminal of the power module 100's output port. As shown by the blue dashed line, when current flows out of power module 100, it begins from the second terminal of the power module 100's output port, passes sequentially through the second diode D2 and the auxiliary diode D3, and exits from the second terminal of the power module 100's output port.

[0079] It should be added that when the power module 100 is in the on or off state, the clamping module 10 is in the standby state, and the clamping capacitor Cs does not participate in the operation. The auxiliary power switch T3 in the auxiliary switching module 30 remains in the on state. The polarity of the output voltage of the power module 100 is determined by the complementary pulse situation of the first power switch T1 and the second power switch T2. The specific devices through which the current flows depend on the current flow direction in a certain switching state (the current flow direction shown by the red or blue dashed lines). When the power module 100 is running normally, the operating current only passes through the first switching module or the second switching arm in the half-bridge module 20, and only causes losses to half of the bridge arm in the half-bridge module 20. The losses are similar to those of a traditional half-bridge power module 100. The additional components in this embodiment do not cause additional conduction losses.

[0080] Combination Figure 5 As shown, when a DC-side fault occurs, the power module 100 enters a locked state, and the first switch module, the second switch module, and the auxiliary switch module 30 are all turned off. The fault current flows through the auxiliary diode D3 and the target diode D4 of the auxiliary switch module 30 to the clamping capacitor Cs. The clamping capacitor Cs absorbs the fault current, thereby clamping the voltage. If the voltage across the clamping capacitor Cs exceeds its withstand capability, the metal oxide varistor M1 will conduct, further clamping the voltage and protecting the device from overvoltage damage.

[0081] Overall, the power module 100 provided in this application embodiment, by setting an auxiliary switching module 30 including an auxiliary switching transistor and an auxiliary diode D3 below a conventional half-bridge structure, and adding an overvoltage protection device 50 connected in parallel with the clamping capacitor Cs, and setting a unidirectional conduction module 40 connected in series with the clamping capacitor Cs, achieves DC-side fault clearing by using the clamping capacitor Cs instead of the DC-side capacitor to absorb fault current with only a few additional components. This prevents the power module 100 from being overcharged and causing the system to discharge and impact the system during recovery, while maintaining a DC-side fault clearing capability with essentially the same loss characteristics as a conventional half-bridge power module 100 under steady-state operation. During the DC-side fault clearing process, only a passive blocking mode is needed for rapid clearing, and the use of the clamping capacitor Cs and the overvoltage protection device 50 connected in parallel with it to absorb fault energy prevents severe overvoltage from being applied to the clamping capacitor Cs. This feature not only significantly improves fault clearing efficiency but also reduces the impact of faults on system operation, enabling the system to quickly resume operation after fault clearing, while also providing reactive power support capabilities.

[0082] It is understood that the above are all examples and do not serve as a substantial limitation on the power module 100 protected by this application.

[0083] Based on the power module 100 provided in the above embodiments, and using the same inventive concept, this application also provides a modular multilevel converter 1000 corresponding to the power module 100. Please refer to the following. Figure 6 , Figure 6 This is a schematic diagram of the structure of a modular multilevel converter 1000 provided in one embodiment of this application.

[0084] like Figure 6 As shown, the modular multilevel converter 1000 includes at least one power module 100 as described in any of the foregoing embodiments of this application. The power module 100 can be applied to the modular multilevel converter 1000 as a basic unit of the bridge arm. A single-phase bridge arm is constructed by connecting multiple power modules 100 in series, thereby realizing high-voltage direct current transmission. Each power module 100 can be independently controlled, and the required high-voltage direct current voltage can be synthesized by adjusting the module's output voltage.

[0085] Because the aforementioned power module 100 has low loss and DC-side fault clearing capabilities, its application in the modular multilevel converter 1000 can significantly improve the performance and reliability of the modular multilevel converter 1000, increase its operating efficiency, and quickly clear faults in the event of DC-side faults. Therefore, it helps to achieve safe and stable operation of the modular multilevel converter 1000, enhances its adaptability and reliability under complex operating conditions, and provides strong technical support for the development of flexible DC transmission systems.

[0086] The functional blocks shown in the above-described structural diagram can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, they can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this application are programs or code segments used to perform the required tasks. Programs or code segments can be stored on a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried on a carrier wave. "Machine-readable medium" can include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio frequency (RF) links, etc. Code segments can be downloaded via computer networks such as the Internet, intranets, etc.

[0087] It should be noted that, in this document, 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 process, method, article, or apparatus.

[0088] It should be clarified that the various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. According to the embodiments described above, these embodiments do not exhaustively describe all details, nor do they limit this application to only the specific embodiments described. Obviously, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this application, thereby enabling those skilled in the art to make good use of this application and modifications based on it. This application is limited only by the claims and their full scope and equivalents.

[0089] Those skilled in the art will understand that the above embodiments are exemplary and not restrictive. Different technical features appearing in different embodiments can be combined to achieve beneficial effects. Based on a study of the drawings, specification, and claims, those skilled in the art should be able to understand and implement other variations of the disclosed embodiments. In the claims, the term "comprising" does not exclude other structures; the quantity refers to "one" but does not exclude multiple; the terms "first" and "second" are used to identify names and not to indicate any particular order. Any reference numerals in the claims should not be construed as limiting the scope of protection. The appearance of certain technical features in different dependent claims does not mean that these technical features cannot be combined to achieve beneficial effects.

[0090] This document uses specific examples to illustrate the principles and implementation methods of this application. The examples are merely for the purpose of helping to understand the method and core ideas of this application. The above are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, and the existence of an infinite number of specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the concept and technical solution of this application to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A power module, characterized in that, The power module includes a support capacitor, a clamping module, a half-bridge module, and an auxiliary switching module; The first end of the clamping module is electrically connected to the first pole of the supporting capacitor, the second end of the clamping module is electrically connected to the second end of the supporting capacitor, the third end of the clamping module is electrically connected to the first node, the clamping module includes a clamping capacitor, the first end of the clamping capacitor is electrically connected to the second node, and the second end of the clamping capacitor is electrically connected to the second end of the clamping module. The first end of the half-bridge module is electrically connected to the first node, and the second end of the half-bridge module is electrically connected to the second end of the clamping module to the third node; The first terminal of the auxiliary switch module is electrically connected to the third node, and the second terminal of the auxiliary switch module is electrically connected to the second node. The auxiliary switch module includes at least one auxiliary switch unit, and the auxiliary switch unit includes an auxiliary power switch and an auxiliary diode connected in reverse parallel with the auxiliary power switch. The half-bridge module includes a bridge arm midpoint, which is electrically connected to the first end of the output port of the power module, and the second end of the auxiliary switch module is electrically connected to the second end of the output port of the power module.

2. The power module according to claim 1, characterized in that, The power module also includes: A unidirectional conduction module, wherein the first end of the unidirectional conduction module is electrically connected to the second end of the auxiliary switch module, and the second end of the unidirectional conduction module is electrically connected to the second node; The second end of the auxiliary switch module is electrically connected to the second node via the unidirectional conduction module, and the current flow direction of the unidirectional conduction module is from the second end of the auxiliary switch module to the second node.

3. The power module according to claim 2, characterized in that, The unidirectional conduction module includes: At least one target diode, wherein the anode of any target diode is electrically connected to the second terminal of the auxiliary switching module, and the cathode of the target diode is electrically connected to the second node; The second terminal of the auxiliary switch module is electrically connected to the second node via the target diode.

4. The power module according to claim 1, characterized in that, The power module also includes: An overvoltage protection device, wherein a first terminal of the overvoltage protection device is electrically connected to a first terminal of the clamping capacitor, and a second terminal of the overvoltage protection device is electrically connected to a second terminal of the clamping capacitor; The overvoltage protection device is used to provide a shunt path when the voltage difference across the clamping capacitor is greater than the overvoltage threshold.

5. The power module according to claim 4, characterized in that, The overvoltage protection device includes a metal oxide varistor.

6. The power module according to claim 1, characterized in that, The clamping module also includes an anode reactor, a clamping diode, and a clamping resistor; The first end of the anode reactor and the first end of the clamping resistor are respectively electrically connected to the first pole of the supporting capacitor. The second end of the anode reactor is electrically connected to the anode of the clamping diode at the first node. The cathode of the clamping diode and the second end of the clamping resistor are respectively electrically connected to the second node.

7. The power module according to claim 1, characterized in that, The half-bridge module includes a first switch module and a second switch module. The first switch module includes at least one first switch unit, and the second switch module includes at least one second switch unit. The first end of the first switch module is electrically connected to the third end of the clamping module, the second end of the first switch module and the first end of the second switch module are electrically connected to the midpoint of the bridge arm, and the second end of the second switch module is electrically connected to the third node.

8. The power module according to claim 7, characterized in that, The first switching unit includes a first power switch and a first diode connected in reverse parallel with the first power switch; The second switching unit includes a second power switch and a second diode connected in reverse parallel with the second power switch.

9. The power module according to claim 7, characterized in that, The power module is configured as follows: In response to the power module being in the active state, the first switch module and the auxiliary switch module are turned on, and the second switch module is turned off; and / or, In response to the power module being in the off state, the second switch module and the auxiliary switch module are turned on, and the first switch module is turned off; and / or, In response to the power module being in a locked state, the first switch module, the second switch module, and the auxiliary switch module are all turned off.

10. A modular multilevel converter, characterized in that, It includes at least one power module as described in any one of claims 1-9.

Images