A unit bypass control circuit of a cascade topology and a power electronic device

Abstract

The application provides a unit bypass control circuit of a cascade topology and a power electronic device. The circuit comprises a medium-voltage power supply, a low-voltage unit and a bypass control component. The bypass control component is arranged in one-to-one correspondence with the low-voltage unit and is arranged between the medium-voltage power supply and the low-voltage unit and comprises: a disconnecting module which is disconnectably connected in series between the medium-voltage power supply and the low-voltage unit; and a semiconductor bypass module which is connected in parallel with the low-voltage unit and is connected across the disconnecting module on the side close to the medium-voltage power supply. The circuit further comprises a detection circuit for detecting the operating state of the low-voltage unit. When a fault occurs, the detection circuit controls the semiconductor bypass module to conduct to divert the fault current and controls the disconnecting module to disconnect the electrical connection between the medium-voltage power supply and the low-voltage unit. Thus, the protection lag problem is solved by combining the physical isolation of the disconnecting module and the rapid diversion of the fault current by the semiconductor, the unit damage and the further expansion of the fault are effectively avoided, and the circuit can continue to stably provide voltage to the outside.

Description

Technical Field

[0001] This invention relates to the field of power electronics, and more particularly to a cascaded topology unit bypass control circuit and power electronic equipment. Background Technology

[0002] In the field of medium- and high-voltage power electronic conversion, cascaded topologies are widely used due to their excellent performance at high voltage levels. As a core component of such systems, unit bypass technology plays a crucial role in ensuring continuous equipment operation. When a power unit in a cascaded system fails, the bypass control mechanism effectively isolates and bypasses the faulty unit, enabling the power electronic equipment to maintain the continuity of main circuit power transmission even with partial component failure. This is an important guarantee for improving system redundancy and operational safety.

[0003] However, existing unit bypass technologies still face significant challenges when dealing with complex operating conditions. Conventional solutions often employ a single mechanical switching logic, whose response characteristics frequently lag behind the failure process of power electronic devices, making it difficult to complete current transfer in the early stages of a fault and easily leading to the expansion of damage to internal components. Furthermore, when facing extreme potential difference conditions such as unit grounding, the insulation architecture design of existing mechanisms often fails to guarantee the safety between the main circuit and the control circuit, posing risks of arcing and insulation failure. In addition, due to the lack of effective commutation mechanisms and integrated design, the system experiences heavy losses during bypass operation, and the overall structural compactness is insufficient.

[0004] Therefore, there is an urgent need for a unit bypass control scheme that takes into account response speed, insulation reliability and operating efficiency, in order to solve the technical bottleneck of existing cascaded systems in terms of fault redundancy. Summary of the Invention

[0005] In order to overcome the above-mentioned technical defects, the purpose of this invention is to provide a cascaded topology unit bypass control circuit and power electronic equipment.

[0006] This invention discloses a cascaded topology unit bypass control circuit, including a medium-voltage power supply, a low-voltage unit, and a bypass control component; The bypass control component is configured in a one-to-one correspondence with the low-voltage unit and is located between the medium-voltage power supply and the low-voltage unit. The bypass control component includes: Disconnect module, which can be disconnected in series between the medium-voltage power supply and the low-voltage unit; The semiconductor bypass module is connected in parallel with the low-voltage unit and is connected across the side of the disconnect module closest to the medium-voltage power supply. The unit bypass control circuit also includes at least one detection circuit, which is communicatively connected to the semiconductor bypass module and electrically connected to the low-voltage unit, for detecting the operating status of the low-voltage unit. When a low-voltage unit fails, at least one detection circuit controls the semiconductor bypass module to turn on to transfer the fault current, while simultaneously controlling the disconnect module to disconnect the electrical connection between the medium-voltage power supply and the low-voltage unit.

[0007] Preferably, the disconnect module includes a pair of normally open mechanical switches; A pair of normally open mechanical switches are connected in series on the line between the medium-voltage power supply and the low-voltage unit, respectively, to disconnect the medium-voltage power supply and the low-voltage unit when the low-voltage unit fails.

[0008] Preferably, the semiconductor bypass module includes a pair of anti-parallel thyristors.

[0009] Preferably, the bypass control component further includes a mechanical bypass module, which includes a normally closed mechanical switch; The mechanical bypass module and the semiconductor bypass module are connected in parallel so that when the semiconductor bypass module is turned on, the mechanical bypass module is closed, realizing the commutation from the semiconductor bypass module to the mechanical bypass module, thereby reducing the on-state voltage drop of the bypass control component.

[0010] Preferably, the bypass control component further includes a coil module; the coil module is electrically connected to the low-voltage unit for power supply and is communicatively connected to at least one detection circuit to receive control signals; The coil module includes multiple coils, which are used to drive normally open mechanical switches and normally closed mechanical switches respectively.

[0011] Preferably, at least one detection circuit includes an overvoltage detection circuit and / or a desaturation detection circuit.

[0012] Preferably, the disconnect module, the semiconductor bypass module, and the normally closed mechanical switch constitute the primary side main circuit, and the coil module constitutes the secondary side control circuit. The insulation withstand voltage level between the primary main circuit and the secondary control circuit is compatible with the voltage level of the medium-voltage power supply.

[0013] Preferably, the bypass control assembly further includes a housing, the housing forming a receiving space; The disconnect module, semiconductor bypass module, normally closed mechanical switch and coil module are all housed within the housing space to form an integrated package structure.

[0014] A second aspect of this application provides a power electronic device comprising a plurality of cascaded topologies of any one of the foregoing; wherein, the medium-voltage power supplies in any two adjacent cascaded topologies of the unit bypass control circuits are connected in series with each other, and the low-voltage units are connected in parallel with each other.

[0015] Preferably, the power electronic equipment is a solid-state transformer, a medium-voltage frequency converter, an active power filter, or a static var compensator.

[0016] Compared with existing technologies, the above technical solution has the following advantages: 1. The core of the cascaded topology unit bypass control circuit provided in this application lies in the introduction of a bypass control component including a disconnect module and a semiconductor bypass module, as well as a detection circuit. When a fault occurs inside the low-voltage unit, if it cannot be handled in time, the fault will not only damage the unit itself but also affect the entire cascaded topology main circuit. Through real-time monitoring of the low-voltage unit's operating status by the detection circuit, once an anomaly is detected, the detection circuit can instantly control the parallel semiconductor bypass module to conduct. Utilizing the extremely fast response speed of semiconductor devices, the system can preemptively transfer the destructive fault current to the branch where the semiconductor bypass module is located, preventing damage to the internal components of the low-voltage unit due to the inability to shut off the fault current. At the same time, the detection circuit controls the series disconnect module to operate, thereby physically disconnecting the connection between the medium-voltage power supply and the low-voltage unit. This combination of rapid current transfer and physical isolation successfully solves the protection hysteresis problem caused by the slow action of traditional mechanical methods, effectively preventing further expansion of the fault and allowing the circuit to continue to stably supply voltage. 2. Furthermore, in terms of specific hardware implementation and collaborative action mechanism, this application significantly enhances the overall protection capability of the system through refined module selection and time-sharing control. In the instant a short circuit or severe overvoltage occurs in the low-voltage unit, the overvoltage detection circuit or desaturation detection circuit can keenly detect the anomaly and trigger a pair of anti-parallel thyristors to act as a rapid discharge channel, meeting the AC bidirectional conduction requirements and completing transient action in a very short time. Subsequently, the electromagnetic force generated by the coil module drives the normally closed mechanical switch in the mechanical bypass module to close, utilizing its extremely low contact resistance to take over the thyristor branch and achieve natural commutation, thereby significantly reducing the steady-state on-state voltage drop and long-term operating losses of the bypass control components. Simultaneously, the coil module drives a pair of normally open mechanical switches connected in series at the input and output ends to open synchronously, completely physically isolating the faulty unit. This achieves a combination of fast semiconductor response and low-loss, high-isolation mechanical switches, further improving safety performance. 3. To address the high-voltage insulation safety hazards of cascaded topologies under extreme operating conditions, this application also makes a breakthrough in the insulation design of the bypass control component. Traditional designs often only arrange insulation based on the voltage of the low-voltage unit itself, which is prone to breakdown and arcing when the low-voltage unit is grounded and short-circuited due to the high voltage of the entire medium-voltage power grid. This application defines the disconnect module, semiconductor bypass module, and normally closed mechanical switch as the primary side main circuit, and the coil module as the secondary side control circuit, and mandates that the insulation withstand voltage level between the two be compatible with the voltage level of the medium-voltage power supply, thus constructing a robust high-voltage safety barrier. In addition, by introducing a housing and integrating the above-mentioned core components within the housing space for integrated packaging, not only is the overall physical size of the component significantly reduced and the system integration improved, but the fixed physical form also strictly ensures high-standard insulation withstand voltage requirements, improving the industrial-grade protection level of the bypass control component; 4. Finally, this application also provides a power electronic device based on the aforementioned cascaded topology. By incorporating a highly reliable bypass control component in the circuit, this device structure inherently possesses strong design redundancy. When individual low-voltage units fail and are bypassed and isolated, the remaining normally operating units can still maintain their original topology connection and continue outputting power. Applying this architecture, which features fast bypass, low-loss commutation, and high insulation withstand voltage characteristics, to heavy equipment such as solid-state transformers, medium-voltage frequency converters, or active power filters enables the equipment to quickly and safely perform self-healing isolation and non-stop switching when faced with sudden failures of internal components, greatly satisfying the stringent engineering requirements for high safety and stability of high-voltage converter equipment in industrial settings. Attached Figure Description

[0017] Figure 1 This application provides a schematic diagram of the structural principle of the power electronic equipment; Figure 2 A schematic diagram of the circuit structure for one implementation of the unit bypass control circuit of the cascaded topology provided in this application; Figure 3 A schematic diagram of the circuit structure for another implementation of the unit bypass control circuit of the cascaded topology provided in this application; Figure 4 A schematic diagram of the circuit structure for another implementation of the unit bypass control circuit of the cascaded topology provided in this application. Detailed Implementation

[0018] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0019] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0020] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0021] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0022] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0024] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0025] Please see Figures 1-2 , Figure 1 This application provides a schematic diagram of the structural principle of the power electronic equipment; Figure 2 A schematic diagram of the circuit structure for one implementation of the unit bypass control circuit of the cascaded topology provided in this application.

[0026] like Figures 1-2 As shown, the first aspect of the present invention discloses a cascaded topology unit bypass control circuit, including a medium-voltage power supply, a low-voltage unit, and a bypass control component. The bypass control component is configured in a one-to-one correspondence with the low-voltage unit and is located between the medium-voltage power supply and the low-voltage unit. The bypass control component includes: Disconnect module, which can be disconnected in series between the medium-voltage power supply and the low-voltage unit; The semiconductor bypass module is connected in parallel with the low-voltage unit and is connected across the side of the disconnect module closest to the medium-voltage power supply. The unit bypass control circuit also includes at least one detection circuit, which is communicatively connected to the semiconductor bypass module and electrically connected to the low-voltage unit, for detecting the operating status of the low-voltage unit. When a low-voltage unit fails, at least one detection circuit controls the semiconductor bypass module to turn on to transfer the fault current, while simultaneously controlling the disconnect module to disconnect the electrical connection between the medium-voltage power supply and the low-voltage unit.

[0027] This can be understood as follows: The core of the cascaded topology unit bypass control circuit provided in this application lies in the introduction of a bypass control component including a disconnect module and a semiconductor bypass module, as well as a detection circuit. Under normal operating conditions, the medium-voltage power supply is electrically connected to the low-voltage unit for power conversion. When a fault occurs inside the low-voltage unit, if it cannot be handled in time, the fault will not only damage the unit itself but also affect the entire cascaded topology main circuit. Through real-time monitoring of the low-voltage unit's operating status by the detection circuit, once an anomaly is detected, the detection circuit can instantly control the parallel semiconductor bypass module to conduct. Utilizing the extremely fast response speed of semiconductor devices, the system can preemptively transfer the destructive fault current to the branch where the semiconductor bypass module is located, preventing damage to the internal components of the low-voltage unit due to the inability to shut off the fault current. Simultaneously, the detection circuit controls the series disconnect module to operate, thereby physically disconnecting the connection between the medium-voltage power supply and the low-voltage unit. This combination of rapid current transfer and physical isolation successfully solves the protection hysteresis problem caused by the slow action of traditional mechanical methods, effectively preventing further expansion of the fault and allowing the circuit to continue to stably supply voltage.

[0028] The above is an explanation of the basic concept of this application. The specific implementation methods of each component will be explained below.

[0029] First, let's explain the disconnected module.

[0030] In one possible implementation, the disconnect module comprises a pair of normally open mechanical switches; A pair of normally open mechanical switches are connected in series on the line between the medium-voltage power supply and the low-voltage unit, respectively, to disconnect the medium-voltage power supply and the low-voltage unit when the low-voltage unit fails.

[0031] In conventional converter topologies, if only single-sided isolation or no physical isolation is used, a faulty unit may still be affected by the high voltage of the main circuit, leading to continuous internal breakdown. By introducing paired normally open mechanical switches, these switches can synchronously disconnect when a low-voltage unit fails. This completely disconnects the faulty low-voltage unit at both its input and output, achieving true electrical isolation and ensuring the safe operation of the remaining healthy units in the cascaded topology.

[0032] Next, the semiconductor bypass module will be explained.

[0033] In one possible implementation, the semiconductor bypass module includes a pair of anti-parallel thyristors.

[0034] In a cascaded topology AC system, the direction of the main circuit current alternates periodically. By specifically selecting an anti-parallel thyristor as the semiconductor bypass module, the requirement for bidirectional conduction of the positive and negative half-waves of the AC circuit can be met. More importantly, the anti-parallel thyristor can conduct within microseconds after receiving a trigger signal. In the instant of a short circuit or severe overvoltage in the low-voltage unit, the anti-parallel thyristor acts as a high-speed bleed channel, completing its action before the power devices inside the low-voltage unit are damaged, greatly improving the system's transient protection capability against sudden faults.

[0035] However, although semiconductor bypass modules have extremely fast response times, a forward voltage drop is unavoidable when semiconductor devices are turned on. Therefore, the bypass control component provided in this application can be supplemented with corresponding components to eliminate the adverse effects of the forward voltage drop.

[0036] For example, in one possible implementation, the bypass control component further includes a mechanical bypass module, which includes a normally closed mechanical switch; The mechanical bypass module and the semiconductor bypass module are connected in parallel so that when the semiconductor bypass module is turned on, the mechanical bypass module is closed, realizing the commutation from the semiconductor bypass module to the mechanical bypass module, thereby reducing the on-state voltage drop of the bypass control component.

[0037] While semiconductor bypass modules offer extremely fast response, semiconductor devices inevitably experience forward voltage drops during conduction, leading to significant heat generation over prolonged periods. By connecting a mechanical bypass module in parallel with a semiconductor bypass module, the normally closed mechanical switch closes after the anti-parallel thyristor completes its transient fault current transfer. Due to the extremely low contact resistance of the mechanical switch, current naturally commutates and flows through the mechanical bypass module. This mechanism perfectly combines the fast response of semiconductor devices with the low impedance of mechanical switches, effectively taking over the thyristor branch and significantly reducing the steady-state on-state voltage drop and long-term operating losses of the bypass control components.

[0038] Furthermore, based on the selection of the above mechanical bypass module and disconnect module, the control method of these modules can be further designed.

[0039] In one possible implementation, the bypass control component further includes a coil module; the coil module is electrically connected to the low-voltage unit for power supply and is communicatively connected to at least one detection circuit to receive control signals; The coil module includes multiple coils, which are used to drive normally open mechanical switches and normally closed mechanical switches respectively.

[0040] This can be understood as follows: the technical solution here introduces a coil module as the direct drive source for mechanical actions. To achieve mechanical isolation of the high-voltage main circuit and effective conversion of low-voltage control commands, the coil module is electrically connected to the low-voltage unit to obtain the electrical energy required for drive, and receives control signals from the detection circuit via a communication connection. The multiple coils contained within the coil module correspond to normally open and normally closed mechanical switches, respectively. When a signal is received, the coil generates electromagnetic force to drive the corresponding mechanical contacts to perform open or closed actions. This structural design streamlines the signal and energy flow of the system, making the actions of the mechanical bypass module and the disconnect module more precise and reliable.

[0041] It will be understood by those skilled in the art that the specific selection of at least one of the aforementioned detection circuits is not limited.

[0042] In one possible implementation, at least one detection circuit includes an overvoltage detection circuit and / or a desaturation detection circuit.

[0043] In power electronic conversion processes, the most critical failure modes for low-voltage units are often overvoltage breakdown of internal electrolytic capacitors or shoot-through short circuits in internal silicon carbide power modules. Overvoltage detection circuits can sensitively detect abnormal voltage spikes in the unit and trigger thyristors, while desaturation detection circuits are specifically designed to identify short-circuit overcurrent characteristics of power devices and trigger thyristors. By configuring dedicated detection circuits for these two core failure modes, bypass control components can act promptly before destructive consequences occur, preventing physical damage to internal components and even impacting external systems.

[0044] Of course, those skilled in the art can choose at least one or both of the overvoltage detection circuit and the desaturation detection circuit as needed. This application does not impose any restrictions here, and those skilled in the art can design it themselves as needed.

[0045] Finally, there are no restrictions on the specific implementation method of the insulation design of the unit bypass control circuit of the cascaded topology.

[0046] In one possible implementation, the disconnect module, the semiconductor bypass module, and the normally closed mechanical switch constitute the primary side main circuit, and the coil module constitutes the secondary side control circuit. The insulation withstand voltage level between the primary main circuit and the secondary control circuit is compatible with the voltage level of the medium-voltage power supply.

[0047] The principle needs to be explained here: In existing technologies, insulation is often arranged only according to the voltage level of the low-voltage unit itself. However, this poses a serious hidden danger: once a low-voltage unit experiences a short circuit to ground, because it is connected to the high-voltage side, its two ends will directly bear the high voltage of the entire medium-voltage power grid, which can easily lead to insulation breakdown and arcing. Therefore, this application defines the disconnect module, semiconductor bypass module, and normally closed mechanical switch as the primary side main circuit, and the coil module as the secondary side control circuit, and mandates that the insulation withstand voltage level between the two be compatible with the voltage level of the medium-voltage power supply, thereby constructing a robust high-voltage safety barrier. Even under extreme conditions of a low-voltage unit grounding fault, the system can still operate safely without series breakdown between the high and low voltage sides.

[0048] Furthermore, in one possible implementation, the bypass control component also includes a housing that forms a receiving space; The disconnect module, semiconductor bypass module, normally closed mechanical switch and coil module are all housed within the housing space to form an integrated package structure.

[0049] This can be understood as follows: By introducing a housing into the bypass control component and integrating each core module into an integrated packaging structure, on the one hand, the problems of large volume and difficulty in strictly controlling insulation distance are prevented, the overall physical size of the bypass control component is significantly reduced, and the system integration is improved. On the other hand, the integrated packaging structure can strictly ensure the high standard of insulation withstand voltage level requirements by using a fixed physical form during the manufacturing stage, thereby improving the industrial-grade reliability and protection level of the bypass control component.

[0050] Please see Figures 3-4 , Figure 3 A schematic diagram of the circuit structure for another implementation of the unit bypass control circuit of the cascaded topology provided in this application; Figure 4 A schematic diagram of the circuit structure for another implementation of the unit bypass control circuit of the cascaded topology provided in this application.

[0051] Those skilled in the art will understand that the aforementioned technical solutions can be used in any combination without requiring all of them to be used in the unit bypass control circuit of the cascaded topology. For example... Figures 3-4 As shown, in one possible implementation, the cascaded topology's unit bypass control circuit is only provided with [specific configuration], while in another possible implementation, the cascaded topology's unit bypass control circuit is only provided with [specific configuration]. This application makes no limitations herein.

[0052] The above is a complete description of the unit bypass control circuit of the cascaded topology provided in this application.

[0053] A second aspect of this application provides a power electronic device comprising a plurality of cascaded topologies of any one of the foregoing; wherein, the medium-voltage power supplies in any two adjacent cascaded topologies of the unit bypass control circuits are connected in series with each other, and the low-voltage units are connected in parallel with each other.

[0054] By incorporating highly reliable bypass control components in the aforementioned circuitry, this device architecture inherently possesses strong design redundancy. Even if individual low-voltage units fail and are isolated by bypass, the remaining normally functioning units can maintain their original topology and continue outputting power.

[0055] It is understandable that the specific types of the aforementioned power electronic equipment are not limited.

[0056] For example, such as Figure 1 As shown, the power electronic device is a solid-state transformer.

[0057] In another possible implementation, the power electronic device can also be one of a medium-voltage frequency converter, an active power filter, or a static var compensator.

[0058] All of the above types of equipment are infrastructure for high-power power conversion, and have extremely high requirements for continuous operation. Applying circuits with high-speed bypass, low-loss commutation, and high insulation withstand voltage characteristics to these heavy-duty equipment enables them to quickly and safely self-heal and switch off without downtime in the event of sudden internal component failures. This greatly meets the stringent engineering requirements for high safety and stability of high-voltage converter equipment in industrial settings. It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A unit bypass control circuit for a cascaded topology, characterized in that, The unit bypass control circuit includes a medium-voltage power supply, a low-voltage unit, and a bypass control component. The bypass control component is configured in a one-to-one correspondence with the low-voltage unit and is located between the medium-voltage power supply and the low-voltage unit. The bypass control component includes: A disconnect module, which can be disconnected in series between the medium-voltage power supply and the low-voltage unit; A semiconductor bypass module, wherein the semiconductor bypass module is connected in parallel with the low-voltage unit and is connected across the disconnect module on the side closest to the medium-voltage power supply; The unit bypass control circuit further includes at least one detection circuit, which is communicatively connected to the semiconductor bypass module and electrically connected to the low-voltage unit, for detecting the operating status of the low-voltage unit. When the low-voltage unit fails, the at least one detection circuit controls the semiconductor bypass module to turn on to transfer the fault current, and at the same time controls the disconnection module to disconnect the electrical connection between the medium-voltage power supply and the low-voltage unit.

2. The unit bypass control circuit of the cascaded topology as described in claim 1, characterized in that, The disconnect module includes a pair of normally open mechanical switches; The pair of normally open mechanical switches are connected in series in the line between the medium-voltage power supply and the low-voltage unit, respectively, and are used to disconnect the medium-voltage power supply and the low-voltage unit when the low-voltage unit fails.

3. The unit bypass control circuit of the cascaded topology as described in claim 1, characterized in that, The semiconductor bypass module includes a pair of anti-parallel thyristors.

4. The unit bypass control circuit of the cascaded topology as described in claim 2, characterized in that, The bypass control component also includes a mechanical bypass module, which includes a normally closed mechanical switch; The mechanical bypass module is connected in parallel with the semiconductor bypass module so that when the semiconductor bypass module is turned on, the mechanical bypass module is closed, realizing the commutation from the semiconductor bypass module to the mechanical bypass module, thereby reducing the on-state voltage drop of the bypass control component.

5. The unit bypass control circuit of the cascaded topology as described in claim 4, characterized in that, The bypass control component also includes a coil module; the coil module is electrically connected to the low-voltage unit for power supply and is communicatively connected to the at least one detection circuit to receive control signals. The coil module includes multiple coils, which are used to drive the normally open mechanical switch and the normally closed mechanical switch respectively.

6. The unit bypass control circuit of the cascaded topology as described in claim 5, characterized in that, The at least one detection circuit includes an overvoltage detection circuit and / or a desaturation detection circuit.

7. The unit bypass control circuit of the cascaded topology as described in claim 6, characterized in that, The disconnect module, the semiconductor bypass module, and the normally closed mechanical switch constitute the primary side main circuit, and the coil module constitutes the secondary side control circuit. The insulation withstand voltage level between the primary side main circuit and the secondary side control circuit is adapted to the voltage level of the medium-voltage power supply.

8. The unit bypass control circuit of the cascaded topology as described in claim 7, characterized in that, The bypass control assembly also includes a housing that forms a receiving space; The disconnect module, the semiconductor bypass module, the normally closed mechanical switch, and the coil module are all disposed within the accommodating space to form an integrated package structure.

9. A power electronic device, characterized in that, It includes multiple unit bypass control circuits of cascaded topologies as described in any one of claims 1-8; wherein, the medium-voltage power supplies in any two adjacent unit bypass control circuits of the cascaded topology are connected in series with each other, and the low-voltage units are connected in parallel with each other.

10. The power electronic device as described in claim 9, characterized in that, The power electronic equipment is a solid-state transformer, a medium-voltage frequency converter, an active power filter, or a static var compensator.

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