Rail voltage limiting circuit and system

Abstract

The embodiment of the application provides a rail voltage limiting circuit and system, and belongs to the technical field of power equipment, which comprises a first port and a second port, a first switch module connected between the first port and the second port, a second switch module connected in parallel with the first switch module, and a third switch module connected in parallel with the second switch module, wherein the first switch module comprises a bidirectional conducting thyristor, the second switch module comprises a contactor, and the third switch module comprises a mechanical switch. The rail voltage limiting circuit provided by the application sets different types of the first switch module, the second switch module and the third switch module, thereby improving the closing and tolerance capacity of the limiting circuit, meeting the use requirement of large current, and realizing fast and reliable closing in the case of large current fault, meeting the three-stage / multi-stage protection requirement of rail potential, and realizing the protection of the DC power supply system and personnel safety.

Description

Technical Field

[0001] This application relates to the field of power equipment technology, and in particular to a rail voltage limiting circuit and system. Background Technology

[0002] Urban rail transit traction DC power supply systems are generally ungrounded systems, using rails as return current devices. During normal train operation or when a fault occurs in the traction DC power supply system, a certain voltage to ground will be generated on the rails. To protect the safety of passengers and staff, a rail voltage limiting system is needed to limit this voltage. Currently, the rail voltage limiting system used in rail transit DC power supply systems typically consists of thyristors and contactors connected in parallel. However, this type of rail limiting system has low closing and withstand capabilities, and a slow closing response speed, making it unsuitable for high-current applications. Utility Model Content

[0003] This application provides a rail voltage limiting circuit and system to solve the above-mentioned technical problems.

[0004] In a first aspect, embodiments of this application provide a rail voltage limiting circuit, including:

[0005] First port and second port; and

[0006] A first switch module, wherein the two ends of the first switch module are respectively connected to the first port and the second port;

[0007] A second switch module is connected in parallel with the first switch module;

[0008] A third switch module, wherein the third switch module is connected in parallel with the second switch module;

[0009] The first switching module includes a bidirectional thyristor, the second switching module includes a contactor, and the third switching module includes a mechanical switch.

[0010] In conjunction with the first aspect, the first switching module includes a plurality of bidirectional thyristors, which are connected in parallel.

[0011] In conjunction with the first aspect, the first switching module includes at least one anti-parallel unidirectional thyristor, and when there are multiple anti-parallel unidirectional thyristors, the multiple anti-parallel unidirectional thyristors are connected in parallel.

[0012] In conjunction with the first aspect, the anti-parallel unidirectional thyristor comprises two anti-parallel unidirectional thyristors.

[0013] In conjunction with the first aspect, the contactor includes either a gas-type DC mechanical contactor or a vacuum DC mechanical contactor.

[0014] In conjunction with the first aspect, the mechanical switch includes either a gas-type fast-closing mechanical switch or a vacuum-type fast-closing mechanical switch.

[0015] In conjunction with the first aspect, the mechanical switch includes any one of the following: a fast-closing mechanical switch based on electromagnetic repulsion, a fast-closing mechanical switch based on permanent magnet repulsion, a fast-closing mechanical switch based on a permanent magnet mechanism, and a fast-closing mechanical switch driven by a high-speed motor.

[0016] In conjunction with the first aspect, the short-circuit current making and withstand capability of the mechanical switch is greater than or equal to 50kA / 250ms.

[0017] In conjunction with the first aspect, the closing time of the mechanical switch is less than or equal to 10ms.

[0018] Secondly, this application provides a rail voltage limiting system, comprising:

[0019] Protection and control devices, current transmitters, voltage transmitters, and rail voltage limiting circuits as described in any one of the first aspects;

[0020] The current transmitter is connected to the second port via a shunt, and the voltage transmitter is connected to the first port;

[0021] The protection and control device is connected to the voltage transmitter, the current transmitter, the second switch module, and the third switch module. The first port is also used to connect to the rail, and the second port is grounded through the shunt.

[0022] One of the above technical solutions has the following advantages or beneficial effects:

[0023] This application provides a rail voltage limiting circuit, including: a first port and a second port; a first switch module, with its two ends connected to the first port and the second port respectively; a second switch module connected in parallel with the first switch module; and a third switch module connected in parallel with the second switch module. The first switch module includes a bidirectional thyristor, the second switch module includes a contactor, and the third switch module includes a mechanical switch. The rail voltage limiting circuit provided by this application improves the closing and withstand capabilities of the limiting circuit by setting the first, second, and third switch modules, meeting the requirements for high current applications. Simultaneously, the use of a mechanical switch enables rapid and reliable closing during high current faults, while also meeting the three-stage / multi-stage protection requirements for rail potential, thus protecting the DC power supply system and personnel safety. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0026] Figure 1 A schematic diagram of the circuit connection of the rail voltage limiting circuit provided in the embodiments of this application;

[0027] Figure 2 A schematic diagram of the circuit connection of the bidirectional thyristor in the rail voltage limiting circuit provided in the embodiments of this application;

[0028] Figure 3 A schematic diagram of the circuit connection of the unidirectional thyristor in the rail voltage limiting circuit provided in the embodiments of this application;

[0029] Figure 4 This is a circuit connection diagram of the rail voltage limiting system provided in an embodiment of this application;

[0030] Figure 5 A schematic diagram illustrating the steps of a control method for a rail voltage limiting circuit provided in an embodiment of this application;

[0031] Figure 6 A schematic diagram of the control strategy of the switching module in the control method of the rail voltage limiting circuit provided in the embodiments of this application;

[0032] Figure 7 A schematic diagram of the voltage difference judgment process of the control method for the rail voltage limiting circuit provided in the embodiment of this application;

[0033] Figure 8 This is a first conduction schematic diagram of the rail voltage limiting circuit provided in an embodiment of this application;

[0034] Figure 9 This is a second conduction schematic diagram of the rail voltage limiting circuit provided in the embodiments of this application;

[0035] Figure 10 A schematic diagram of the system current determination method in the control method of the rail voltage limiting circuit provided in the embodiments of this application;

[0036] Figure 11 This is a third conduction schematic diagram of the rail voltage limiting circuit provided in the embodiments of this application.

[0037] Explanation of reference numerals in the attached figures:

[0038] 100 - First switch module; 200 - Second switch module; 300 - Third switch module; A - First port; B - Second port. Detailed Implementation

[0039] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0040] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application 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 application.

[0041] In the embodiments of this application, "at least one" refers to one or more; "multiple" refers to two or more. In the description of this application, the terms "first," "second," "third," etc., are used only for the purpose of distinguishing descriptions and should not be construed as indicating or implying relative importance, nor should they be construed as indicating or implying order.

[0042] References such as “one embodiment” or “some embodiments” as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the terms “comprising,” “including,” “having,” and variations thereof, as used in this specification, mean “including, but not limited to,” unless otherwise specifically emphasized.

[0043] It should be noted that in the embodiments of this application, "and / or" describes the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. In addition, the character " / ", unless otherwise specified, generally indicates that the associated objects before and after it are in an "or" relationship.

[0044] It should be noted that in the embodiments of this application, "connection" can be understood as electrical connection. The connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0045] It should be noted that the rail voltage limiting system is connected between the negative terminal of the traction power supply system (the negative busbar of the traction station or the return rail) and the ground. When the absolute value of the voltage between the negative terminal of the traction power supply system and the ground is higher than the safe voltage for the human body, the rail voltage limiting system will quickly conduct, limiting the negative terminal potential to the ground potential, thereby ensuring the personal safety of passengers and staff.

[0046] Rail voltage limiting systems typically have three protection stages. Stage 1 protection closes the contactor only when the rail voltage is low (usually 120V), and then opens it after a delay to prevent prolonged use of the grounding grid for return current, which can lead to severe corrosion. Stage 2 protection closes the contactor only when the rail voltage is high (usually 150V), and then locks it. Stage 3 protection handles extremely high rail voltage (usually 600V), first controlling the thyristor to conduct within 0.1ms to rapidly reduce the rail voltage, and then controlling the contactor to close, preventing failure caused by prolonged thyristor current flow.

[0047] With the increasing capacity of DC power supply systems for urban rail transit, the near-end short-circuit current has reached 100kA, and traditional rail potential limiting systems cannot meet the requirements for closing and withstand capabilities. Currently, the short-circuit closing and withstand capabilities of existing rail potential limiting systems are generally less than 50kA / 250ms, mainly due to the poor closing and withstand capabilities of the contactors. Some solutions use multiple sets of thyristors connected in parallel to improve the closing and withstand capabilities. However, since thyristors cannot turn off automatically, they can only meet the closing requirements under short-circuit conditions and cannot meet the self-reset requirements of the first-stage rail potential protection. Furthermore, thyristors require a large footprint, a large number of power electronic devices, complex control, and high cost.

[0048] To address the aforementioned technical problems that urgently need to be solved in this field, this application provides a rail voltage limiting circuit that meets the short-circuit current closing and withstand requirements of over 50kA / 250m, enabling rapid and reliable closing during high-current faults, while also meeting the three-stage / multi-stage protection requirements for rail potential, thus protecting the DC power supply system and personnel safety.

[0049] The specific implementation methods of this application are illustrated below through examples:

[0050] like Figure 1As shown in the figure, this application provides a rail voltage limiting circuit, including: a first port A and a second port B; a first switch module 100, with its two ends connected to the first port A and the second port B respectively; a second switch module 200, connected in parallel with the first switch module 100; and a third switch module 300, connected in parallel with the second switch module 200. The first switch module 100 includes a bidirectional thyristor, the second switch module 200 includes a contactor, and the third switch module 300 includes a mechanical switch. Specifically, the bidirectional thyristor includes two anti-parallel ordinary thyristor integrated circuits, and its switching is controlled by a gate trigger signal. The on / off time of the bidirectional thyristor is in the microsecond range, typically less than 0.1ms. Therefore, when there is a large voltage between the first port A and the second port B, the bidirectional thyristor can quickly turn on, thereby grounding the rail and reducing the rail potential to ground potential. A contactor is an electromagnetic switch that uses electromagnetic force to drive the contacts to close or open. It is mainly used to control the bidirectional current flow between the first port A and the second port B. A mechanical switch is a switch that relies entirely on a mechanical structure to control the circuit's on / off state. It is used to quickly switch on when a large current flows due to a circuit fault, thereby protecting the contactor and thyristor.

[0051] Understandably, by setting a bidirectional thyristor as the first switching module 100, the turn-off response speed of the limiting circuit is improved; by setting a contactor as the second switching module 200, the bidirectional conduction and disconnection of the limiting circuit are realized; and by setting a mechanical switch as the third switching module 300, the closing and withstand capabilities of the limiting circuit are improved, meeting the requirements for high current use, realizing fast and reliable closing in the event of a high current fault, and simultaneously meeting the three-stage / multi-stage protection requirements of the rail potential, thereby protecting the DC power supply system and personnel safety.

[0052] like Figure 2 As shown in this embodiment, the first switching module 100 includes at least one bidirectional thyristor. When there are multiple bidirectional thyristors, they are connected in parallel. Specifically, a single bidirectional thyristor has a maximum current-carrying capacity limit. When the operating current in the actual circuit exceeds the carrying capacity of a single bidirectional thyristor, it may cause the bidirectional thyristor to burn out. Therefore, by connecting multiple bidirectional thyristors in parallel, each bidirectional thyristor can bear a portion of the total current, allowing the overall circuit to carry a larger current and thus overcome the current bottleneck of a single bidirectional thyristor.

[0053] It is understandable that connecting multiple bidirectional thyristors in parallel can improve the current carrying capacity of the circuit. When a single bidirectional thyristor carries a large current, the loss is concentrated and it is prone to overheating. After being connected in parallel, the total current is distributed among multiple bidirectional thyristors, the current of each bidirectional thyristor is reduced, the loss is reduced, the heat dissipation pressure is also reduced, and it helps to extend the life of the device.

[0054] like Figure 3 As shown in the embodiment of this application, the first switching module 100 includes at least one anti-parallel unidirectional thyristor. When there are multiple anti-parallel unidirectional thyristors, they are connected in parallel. Specifically, the anti-parallel unidirectional thyristors can also achieve bidirectional current conduction.

[0055] The maximum rated current of a single anti-parallel unidirectional thyristor is limited. When the operating current in an actual circuit exceeds the carrying capacity of a single anti-parallel unidirectional thyristor, it may burn out. Therefore, by connecting multiple anti-parallel unidirectional thyristors in parallel, each anti-parallel unidirectional thyristor can bear a portion of the total current, allowing the overall circuit to handle a larger current and thus overcome the current bottleneck of a single anti-parallel unidirectional thyristor. Furthermore, with multiple anti-parallel unidirectional thyristors connected in parallel, even if one of them fails due to a fault, the other normal anti-parallel unidirectional thyristors can temporarily share its current, thereby preventing an immediate interruption of the entire circuit.

[0056] It is understandable that connecting multiple anti-parallel unidirectional thyristors in parallel can improve the current carrying capacity of the circuit. When a single anti-parallel unidirectional thyristor carries a large current, the loss is concentrated and it is prone to overheating. After being connected in parallel, the total current is distributed among multiple anti-parallel unidirectional thyristors, the current of each anti-parallel unidirectional thyristor is reduced, the loss is reduced, the heat dissipation pressure is also reduced, and it helps to extend the life of the device.

[0057] like Figure 3 As shown in the embodiment of this application, the anti-parallel unidirectional thyristor includes two anti-parallel unidirectional thyristors. Specifically, a unidirectional thyristor is a semiconductor device with unidirectional conductivity, which can only conduct when a positive voltage is applied to the anode and a trigger signal is applied to the gate. Turning off requires the anode voltage to reverse or the current to drop below the holding current. By cross-connecting the anodes and cathodes of the two unidirectional thyristors (the anode of one is connected to the cathode of the other, and vice versa), a bidirectional current path is formed, which is the anti-parallel unidirectional thyristor. When triggered to conduct, a trigger signal needs to be provided to each of the two unidirectional thyristors separately (one is triggered during the positive half-cycle, and the other during the negative half-cycle), that is, each unidirectional thyristor is controlled independently. By matching and controlling the parameters of the two unidirectional thyristors, the symmetry problem between the first port A and the second port B can be improved.

[0058] It is understandable that by selecting high-power unidirectional thyristors for anti-parallel connection, a larger current flow (tens of kiloamps or more) can be achieved; and by selecting unidirectional thyristors with good characteristics for anti-parallel connection, the withstand performance can be improved.

[0059] In this embodiment, the contactor includes either a gas-type DC mechanical contactor or a vacuum-type DC mechanical contactor. Specifically, both gas-type and vacuum-type DC mechanical contactors are key electrical components used for DC circuit switching control. Their core function is to achieve safe and reliable circuit switching in high-voltage, high-current DC scenarios, while providing overload or short-circuit protection. Gas-type DC mechanical contactors rely on a sealed cavity filled with nitrogen / hydrogen or inert gas for arc extinguishing. Gas-type DC mechanical contactors have excellent arc-extinguishing performance, quickly extinguishing the arc, preventing contact burn-out, and ensuring safe circuit disconnection. Gas-type DC mechanical contactors are suitable for DC scenarios with voltages from hundreds to thousands of volts or currents from tens to hundreds of amps. Vacuum-type DC mechanical contactors mainly rely on the insulating properties of a vacuum environment to extinguish the arc. Because there are almost no gas molecules in a vacuum environment, the arc is difficult to maintain, the arc extinguishing speed is extremely fast, effectively reducing contact wear and thus extending the contactor's service life.

[0060] It is understandable that by selecting gas-type DC mechanical contactors or vacuum-type DC mechanical contactors as the closing and opening switches for the first port A and the second port B, safe and reliable on / off control can be provided for the limiting circuit under medium and high voltage environments, solving the problem of the difficulty in extinguishing DC arcs, and improving the service life of the contactors.

[0061] In this embodiment, the mechanical switch includes either a gas-type fast-closing mechanical switch or a vacuum-type fast-closing mechanical switch. Specifically, the contacts of the gas-type fast-closing mechanical switch are placed in a sealed cavity filled with a high-pressure inert gas (such as sulfur hexafluoride SF6, dry air, or nitrogen), and arc extinguishing is achieved through the gas. Due to the excellent arc-extinguishing capability of the gas medium, the gas-type fast-closing mechanical switch can handle short-time currents of thousands to tens of thousands of amperes, ensuring stable closing even under high current and reducing contact burn-out. The contacts of the vacuum-type fast-closing mechanical switch are sealed in a high-vacuum arc-extinguishing chamber, relying on vacuum for arc extinguishing.

[0062] It is understandable that by selecting a gas-type fast-closing mechanical switch as the mechanical switch, rapid fault isolation of medium and high voltage circuits, rapid switching in high current scenarios, and reliable switching of medium and high voltage operating conditions can be achieved; by selecting a vacuum-type fast-closing mechanical switch as the mechanical switch, high-frequency rapid switching, reliable protection in extreme environments, and low-maintenance long-life operation can be achieved.

[0063] In some embodiments of this application, the mechanical switch includes a fast-closing mechanical switch based on permanent magnet repulsion. The working principle of this fast-closing mechanical switch based on permanent magnet repulsion combines the static holding force of a permanent magnet with the dynamic driving force of electromagnetic repulsion. When the contacts are closed, the permanent magnet provides the holding force; when the contacts are open, a repulsive force is generated by a reverse pulse current. Because the holding force is provided by the permanent magnet, opening and closing require only a short pulse current, resulting in extremely low energy consumption and minimal contact wear. This fast-closing mechanical switch based on permanent magnet repulsion combines the rapid action characteristics of electromagnetic repulsion (opening and closing time of 5-10 milliseconds) with the stable holding capability of a permanent magnet, ensuring reliable triggering and state maintenance in power system protection. Furthermore, the permanent magnet force of this fast-closing mechanical switch is unaffected by external vibrations or electromagnetic interference, exhibiting high stability.

[0064] In some embodiments of this application, the mechanical switch includes a fast-closing mechanical switch based on a permanent magnet mechanism. The working principle of this fast-closing mechanical switch is to utilize the synergistic effect of a permanent magnet and an electromagnetic coil to achieve rapid contact movement and position holding. It replaces traditional spring mechanisms in medium-voltage circuit breakers and contactors, reducing mechanical wear and jamming risks. The opening and closing time is typically 10-30 milliseconds, resulting in high operational reliability. Furthermore, the fast-closing mechanical switch based on a permanent magnet mechanism has a simple component structure, few moving parts, low operating noise, and long maintenance cycles, making it suitable for noise-sensitive environments. Notably, by optimizing the parameters of the permanent magnet and coil, the fast-closing mechanical switch based on a permanent magnet mechanism can precisely control the opening and closing time, meeting the requirements of power system automation.

[0065] In some embodiments of this application, the mechanical switch includes a fast-closing mechanical switch driven by a high-speed motor. The working principle of this fast-closing mechanical switch is that a high-speed rotating motor (such as a permanent magnet synchronous motor) drives the contact movement through a transmission mechanism such as gears and cams. By controlling the motor speed, the fast-closing mechanical switch can flexibly adjust the contact closing speed (closing and opening time 10-50 milliseconds), adapting to different load types. The smoothness of the motor drive reduces contact impact, making it suitable for operating conditions requiring frequent start-stop cycles. Furthermore, the fast-closing mechanical switch driven by a high-speed motor can integrate position sensors and a control system to achieve precise feedback and closed-loop control of the contact position, supporting adaptive protection strategies for smart grids.

[0066] It is understood that the embodiments of this application can achieve different functions by selecting the type of mechanical switch. When a fast-closing mechanical switch based on electromagnetic repulsion is used as the mechanical switch, ultra-high-speed fault isolation, high-frequency fast switching, and high-precision synchronous control of the limiting circuit can be achieved. When a fast-closing mechanical switch based on permanent magnet repulsion is used as the mechanical switch, low-power long-life operation, fast response and reliable holding, and resistance to vibration and interference of the limiting circuit can be achieved. When a fast-closing mechanical switch based on a permanent magnet mechanism is used as the mechanical switch, high-reliability opening and closing, low noise, easy maintenance, and precise time control of the limiting circuit can be achieved. When a fast-closing mechanical switch based on high-speed motor drive is used as the mechanical switch, adjustable-speed fast action, durability under frequent operation, and intelligent control and feedback of the limiting circuit can be achieved.

[0067] In this embodiment, the short-circuit current making and withstand capability of the mechanical switch is greater than or equal to 50kA / 250ms. Specifically, the short-circuit current making and withstand capability includes current making capability and current withstand capability. Current making capability refers to the maximum current value that the switch can safely close at the moment of closing, especially in cases of existing short-circuit faults in the circuit. Under normal circumstances, when a short-circuit fault exists in the circuit, if the switch receives a closing command at this time, it will face an inrush current far exceeding the rated value (the peak short-circuit current can reach 10-30 times the rated current). If the current making capability is insufficient, it may cause the switch contacts to weld or even the casing to explode. Current withstand capability refers to the ability of the switch to continuously withstand the fault current without damage before opening, and is usually divided into short-time withstand capability and peak withstand capability. Among them, short-time withstand capability refers to the AC effective value or DC current value that the switch can withstand within a specified time, mainly resisting the thermal effect of the current and preventing the switch contacts or coils from overheating and burning out. Peak withstand current refers to the maximum peak current that the switch can withstand at the moment of short circuit, mainly resisting the electrodynamic effect, thereby preventing conductive parts from deforming or breaking due to electrodynamic forces. It is worth noting that in the 50kA / 250ms provided in this application embodiment, 50kA represents the maximum short-circuit current intensity that can be turned off, and 250ms represents the duration that the short-circuit current can be withstood. That is to say, the maximum short-circuit current intensity that the mechanical switch can turn off is not less than 50kA, and the duration that it can withstand the short-circuit current is not less than 250ms.

[0068] It is understandable that by setting up mechanical switches, the circuit can withstand larger short-circuit currents and longer short-circuit current durations during use, thereby enabling the system circuit to cope with various complex operating conditions and emergency situations, and thus improving the safety and stability of the system circuit.

[0069] In this embodiment, the closing time of the mechanical switch is less than or equal to 10ms. Specifically, the closing time refers to the duration taken by the mechanical switch from receiving the closing command to the complete closure of the contacts. By setting the closing time of the mechanical switch, the system circuit can control the mechanical switch to quickly perform the closing action in the event of a fault, thereby avoiding shortening the fault duration of the system circuit and improving the stability of the system circuit.

[0070] Understandably, by controlling the closing time of the mechanical switch to less than 10ms, the mechanical switch can quickly short-circuit the fault point, thereby suppressing the residual current, ensuring the success rate of closing, and improving the safety and stability of the system circuit.

[0071] In summary, by connecting multiple bidirectional thyristors in parallel or anti-parallel and then connecting unidirectional thyristors in parallel as the first switch module 100, the current carrying capacity and turn-off response speed of the limiting circuit are improved. By using a contactor as the second switch module 200, the limiting circuit achieves bidirectional conduction and disconnection. By selecting different types of mechanical switches as the third switch module 300, not only are the different application scenarios of the limiting circuit met, but the closing and withstand capabilities of the limiting circuit are also improved. This provides the limiting circuit with safe and reliable on / off control in medium and high voltage environments, and can solve the problem of difficult DC arc extinguishing. It also enables rapid and reliable closing during high current faults, thereby enabling the system circuit to cope with various complex working conditions and emergencies, thus improving the safety and stability of the system circuit. At the same time, it meets the three-stage / multi-stage protection requirements of rail potential, achieving protection for the DC power supply system and personnel safety.

[0072] like Figure 4As shown in the embodiments of this application, a rail voltage limiting system is also provided, including: a protection control device, a current transmitter, a voltage transmitter, and a rail voltage limiting circuit as provided in any of the above embodiments; the current transmitter is connected to a second port via a shunt, and the voltage transmitter is connected to a first port; the protection control device is connected to the voltage transmitter, the current transmitter, a second switch module, and a third switch module, the first port is also used to connect to the rail, and the second port is grounded via a shunt. Specifically, the shunt converts the large current flowing through the rail into a measurable voltage signal; the current transmitter converts the voltage signal from the shunt into a standard electrical signal for processing by the protection control device; the voltage transmitter directly measures the voltage between the rail and ground and converts it into a signal recognizable by the protection control device. For example, when the rail voltage exceeds a safety threshold, the voltage transmitter outputs a corresponding electrical signal, triggering the protection logic; the protection control device coordinates the actions of each component to achieve multiple protection functions. By receiving signals from the current and voltage transmitters, the voltage and current status of the rail is analyzed. For example, when the voltage transmitter detects that the rail potential exceeds 150V, the protection control device immediately triggers the switching module. Based on a preset threshold (e.g., voltage > 90V and lasting 800ms), it controls the second or third switching module to close. The rail voltage limiting circuit's function is to directly ground the rail when an overvoltage is detected, thereby limiting the rail potential and ensuring the safety of personnel and equipment.

[0073] In this embodiment, the rail, as a core component of rail transit, serves dual functions: train traction return (traction current returns to the substation via the rail) and track circuit signal transmission. In some scenarios, excessively high voltages can easily occur between the rails, such as induced overvoltages caused by sudden changes in traction current during train start / brake; instantaneous overvoltages under abnormal conditions like lightning strikes or short-circuit faults; and localized voltage increases due to poor rail surface contact (such as rust or oil contamination). By installing a rail voltage limiting system between the rails, the voltage difference between them can be monitored. When the voltage exceeds a safe threshold, the built-in rail voltage limiting circuit responds quickly, clamping the inter-rail voltage below a safe human body voltage through conduction and current diversion. This prevents excessively high inter-rail voltage from damaging the track insulation components and further prevents the risk of electric shock to maintenance personnel when touching the rails, eliminating safety hazards at the source.

[0074] Understandably, by integrating the rail voltage limiting circuit into the rail voltage limiting system, the current carrying capacity and turn-off response speed of the limiting system are improved. At the same time, it meets the needs of different application scenarios of the limiting system, provides the limiting circuit with safe and reliable on-off control in medium and high voltage environments, enables the system circuit to cope with various complex working conditions and emergency situations, thereby improving the safety and stability of the system circuit and achieving protection for the DC power supply system and personnel safety.

[0075] like Figure 5 As shown, this application embodiment also provides a control method for a rail voltage limiting circuit, used to control the rail voltage limiting circuit provided in any of the above embodiments, including:

[0076] S1: Determine the voltage difference between port A and port B. Specifically, port A connects to the first rail, and port B connects to the second rail. The voltage difference between port A and port B is essentially the potential difference between the first and second rails. The potential difference between the rails is measured by connecting a digital multimeter, oscilloscope, rail voltage detector, and millivoltmeter to the first and second rails. During measurement, it is essential to ensure that no trains are passing through the measurement section and that there are no contaminants on the rails that could interfere with the potential difference.

[0077] S2: Based on the comparison results of the voltage difference with the first voltage threshold, the second voltage threshold and the third voltage threshold, determine the opening and closing control strategy of the first switch module 100, the second switch module 200 and the third switch module 300.

[0078] Specifically, such as Figure 6 and Figure 7 As shown, the control strategy includes:

[0079] S21: When the voltage difference is less than a first voltage threshold, control the first switch module 100, the second switch module 200, and the third switch module 300 to disconnect. Specifically, the first voltage threshold is a safety threshold. When the voltage difference is less than the first voltage threshold, it indicates that the rail potential is within a safe range, and there is no need to discharge current. Therefore, the first switch module 100, the second switch module 200, and the third switch module 300 are in the disconnected state. This avoids unnecessary grounding connections that could generate stray currents that corrode the track bed structure, and reducing the number of switching operations can also extend the service life of the equipment.

[0080] It is worth noting that the first voltage threshold is usually 120V, that is, when the voltage difference between the first rail and the second rail is less than 120V, the first switch module 100, the second switch module 200 and the third switch module 300 are kept in the off state.

[0081] S22: When the voltage difference is greater than or equal to the first voltage threshold and less than the second voltage threshold, the second switch module 200 is closed, and the first switch module 100 and the third switch module 300 are opened. Specifically, when the train starts or brakes, a transient current is generated on the rail. This type of current has a short duration. To avoid this type of current from causing harm to personal safety, the current is discharged by controlling the second switch module 200 to close (conduction state as shown). Figure 8 As shown, Figure 8(The red portion represents a closed circuit, and the black portion represents a closed circuit). It is important to note that after the second switch module 200 completes grounding, it is also necessary to determine the system current of the traction power supply system connected to the rail voltage limiting circuit. If the system current is less than the first current threshold, the second switch module 200 is disconnected. At this time, the first switch module 100, the second switch module 200, and the third switch module 300 are all in the open state. The instantaneous current generated on the rail can be completely discharged after a short period of closure of the second switch module 200. After the second switch module 200 has been closed for a period of time, it is confirmed whether the system current of the traction power supply system is less than the first current threshold. If so, it indicates that the instantaneous current on the rail has been completely released. At this time, the second switch module 200 is disconnected, returning the circuit to its normal connection state.

[0082] It is worth noting that the second voltage threshold is usually 150V. That is, when the voltage difference between the first rail and the second rail is greater than or equal to 120V and less than 150V, the second switch module 200 is controlled to close, and the first switch module 100 and the third switch module 300 are controlled to remain open. After running for a period of time, when it is determined that the voltage difference is less than 120V, the second switch module 200 is controlled to open.

[0083] S23: When the voltage difference is greater than or equal to the second voltage threshold and less than the third voltage threshold, control the second switch module 200 to close and control the first switch module 100 and the third switch module 300 to open. Specifically, when the power supply system of the track fails or multiple trains draw current densely, the voltage difference between the first and second tracks may rise abnormally. If the voltage difference is between the second and third voltage thresholds, control the second switch module 200 to close and lock the tripping, that is, prohibit the second switch module 200 from automatically tripping (conduction state as shown). Figure 8 As shown, Figure 8 (The red part represents the circuit, and the black part represents the non-circuit). In this case, the track needs to discharge current for a long time, and the locked state needs to be reset by maintenance personnel after troubleshooting, so as to avoid damage to maintenance personnel caused by excessive voltage.

[0084] It is worth noting that the second voltage threshold is usually 150V and the third voltage threshold is usually 600V. That is, when the voltage difference between the first rail and the second rail is greater than or equal to 150V and less than 600V, the second switch module 200 is controlled to close and the circuit breaker is locked, while the first switch module 100 and the third switch module 300 are controlled to remain in the open state until the fault is resolved and the maintenance personnel manually open the second switch module 200.

[0085] S24: When the voltage difference is greater than or equal to the third voltage threshold, control the first switch module 100 and the second switch module 200 to close, and control the third switch module 300 to open. Specifically, when the voltage difference is greater than or equal to the third voltage threshold, it indicates severe overvoltage on the track. At this time, the voltage surge is strong and the instantaneous energy is large, requiring a millisecond-level response to avoid circuit burnout. By controlling the first switch module 100 to conduct at the microsecond level, the overvoltage is clamped instantly, blocking the instantaneous high-energy surge to cope with such sudden risks. Because the thyristor will experience losses due to long-term flow, the second switch module 200 is subsequently turned on, and the second switch module 200 continuously conducts current to ground (conduction state as follows). Figure 9 As shown, Figure 9 (The red part represents the closed circuit, and the black part represents the closed circuit). By using the first switch module 100 and the second switch module 200 together, the fast conduction speed of the thyristor is utilized, while the long-term stability of the contactor is also taken advantage of.

[0086] like Figure 10 As shown in the embodiment of this application, the method further includes: determining the system current of the traction power supply system connected to the rail voltage limiting circuit; and, if the system current is determined to be greater than a second current threshold at any time, controlling the second switch module 200 and the third switch module 300 to close, and controlling the first switch module 100 to open. Specifically, when the system current exceeds the second current threshold, the core risk is overcurrent burnout of the device: only the second switch module 200 being turned on may cause damage to the second switch module 200. Therefore, by controlling the third switch module 300 to close and bypass the second switch module 200, a large current flows through the third switch module 300, thereby protecting the second switch module 200 and preventing damage (conduction state as shown). Figure 11 As shown, Figure 11 The red areas represent pathways, and the black areas represent non-pathways.

[0087] In summary, the first switch module 100 is a thyristor, which has a fast turn-on response speed and can quickly conduct to clamp the voltage and block instantaneous high-energy impacts; the second switch module 200 is a contactor, which has stable performance and low loss after continuous conduction; the third switch module 300 is a mechanical switch, which has fast closing capability and strong current carrying capacity, and can quickly close and withstand the flow of large current when the track encounters a large current impact, thereby avoiding damage to the thyristor and contactor.

[0088] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Although this application has disclosed preferred embodiments as above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A rail voltage limiting circuit, characterized in that, include: First port and second port; as well as A first switch module, wherein the two ends of the first switch module are respectively connected to the first port and the second port; A second switch module is connected in parallel with the first switch module; A third switch module, wherein the third switch module is connected in parallel with the second switch module; The first switching module includes a bidirectional thyristor, the second switching module includes a contactor, and the third switching module includes a mechanical switch.

2. The rail voltage limiting circuit according to claim 1, characterized in that, The first switching module includes multiple bidirectional thyristors, which are connected in parallel.

3. The rail voltage limiting circuit according to claim 1, characterized in that, The first switching module includes at least one anti-parallel unidirectional thyristor. When there are multiple anti-parallel unidirectional thyristors, the multiple anti-parallel unidirectional thyristors are connected in parallel.

4. The rail voltage limiting circuit according to claim 3, characterized in that, The anti-parallel unidirectional thyristor comprises two unidirectional thyristors connected in anti-parallel.

5. The rail voltage limiting circuit according to claim 1, characterized in that, The contactor includes either a gas-type DC mechanical contactor or a vacuum DC mechanical contactor.

6. The rail voltage limiting circuit according to claim 1, characterized in that, The mechanical switch includes either a gas-type fast-closing mechanical switch or a vacuum-type fast-closing mechanical switch.

7. The rail voltage limiting circuit according to claim 1, characterized in that, The mechanical switch includes any one of the following: a fast-closing mechanical switch based on electromagnetic repulsion, a fast-closing mechanical switch based on permanent magnet repulsion, a fast-closing mechanical switch based on a permanent magnet mechanism, and a fast-closing mechanical switch driven by a high-speed motor.

8. The rail voltage limiting circuit according to claim 1, characterized in that, The short-circuit current making and withstand capability of the mechanical switch is greater than or equal to 50kA / 250ms.

9. The rail voltage limiting circuit according to claim 1, characterized in that, The closing time of the mechanical switch is less than or equal to 10ms.

10. A rail voltage limiting system, characterized in that, include: Protection and control device, current transmitter, voltage transmitter, and rail voltage limiting circuit as described in any one of claims 1-9; The current transmitter is connected to the second port via a shunt, and the voltage transmitter is connected to the first port; The protection and control device is connected to the voltage transmitter, the current transmitter, the second switch module, and the third switch module. The first port is also used to connect to the rail, and the second port is grounded through the shunt.

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