Hybrid dc circuit breaker fast transfer structure and control method thereof

Abstract

The application discloses a hybrid DC circuit breaker rapid transfer structure and a control method thereof, which comprises a vacuum gap, a gas gap, an operating mechanism, a power electronic breaking unit and a controller, wherein the vacuum gap and the gas gap are sequentially connected in series from top to bottom through a pull rod assembly, vacuum contacts and gas contacts are respectively arranged in the vacuum gap and the gas gap, and the pull rod assembly can make the moving contacts of the vacuum contacts and the gas contacts link up under the action of the operating mechanism. The application utilizes the advantages of the fast recovery speed of the vacuum medium and the high arc pressure of the gas, arranges the vacuum gap and the gas gap in series in the main branch, effectively improves the transfer capacity of the fault current, and thus realizes simple and reliable natural commutation regulation; the application effectively reduces the product volume of the circuit breaker, the control mechanism is simpler, installation and maintenance are facilitated, and the reliability and stability of the circuit breaker control system are improved.

Description

Technical Field

[0001] This invention relates to the field of DC circuit breaker technology, and in particular to a hybrid DC circuit breaker fast transfer structure and its control method. Background Technology

[0002] DC circuit breakers are widely used in the protection and control of high-voltage direct current (HVDC) transmission and DC power systems, and are key equipment for the control, protection, and isolation of DC systems. DC circuit breakers are used to disconnect and connect DC circuits, reliably interrupting high current and high voltage under fault and normal operating conditions.

[0003] Currently, DC circuit breakers are mainly divided into three categories: traditional mechanical DC circuit breakers, solid-state DC circuit breakers, and hybrid DC circuit breakers that combine mechanical switches and solid-state power electronic devices. Traditional mechanical DC circuit breakers use AC circuit breaker contacts to interrupt fault currents. However, DC fault currents do not have a natural zero-crossing point, and the arc cannot be extinguished quickly. An LC auxiliary circuit is required to generate resonance when interrupting DC fault currents, creating an artificial current zero-crossing point for the contact. Although the breaking capacity is strong, capable of interrupting short-circuit currents above 40kA, its breaking time is relatively long, which cannot meet the requirements for high-speed short-circuit fault interruption.

[0004] Solid-state DC circuit breakers typically use power electronic devices such as insulated gate bipolar transistors (IGBTs), integrated gate commutated thyristors (IGCTs), and gate turn-off thyristors (GTOs) as main switches to interrupt fault short-circuit currents. Solid-state DC circuit breakers have advantages such as fast operating speed and arc-free operation; however, due to the need to consider structural complexity, voltage equalization, current equalization, and cooling issues, their application range is somewhat limited.

[0005] Hybrid DC circuit breakers are a new topology that combines fast mechanical switches with solid-state power electronic devices. Hybrid DC circuit breakers can be categorized into natural commutation type, resistance zero-crossing type, and voltage zero-crossing type. Combining the advantages of mechanical and solid-state DC circuit breakers, hybrid DC circuit breakers offer advantages such as arc-free breaking capability, low conduction losses, and no need for dedicated cooling equipment, making them widely used in DC power transmission and distribution. However, current hybrid DC circuit breakers generally suffer from complex structures, excessive size, and difficult maintenance. For example, Chinese invention patent application number 201510068612.9 discloses a new type of high-voltage circuit breaker based on a linear motor operating mechanism, which connects a CO2 gas gap and a vacuum gap in series. Its technical solution uses a linear motor to pull an insulating rod to drive the CO2 gas interrupter and simultaneously drives the vacuum interrupter through a sliding groove linkage crank arm. The overall structure is complex and bulky, and the coordination between the two gaps is difficult. Another example is Chinese invention patent application number 201610165074.X, which discloses a hybrid DC circuit breaker topology. This DC circuit breaker uses two mechanical switches and uses an LC auxiliary circuit to transfer the fault current when a fault occurs. The entire interruption process is cumbersome to control, requiring precise coordination between various actuators to ensure good interaction between mechanical and electronic components. This results in high requirements for system reliability and stability, and makes fault diagnosis and maintenance more complex.

[0006] Therefore, the present invention provides a new solution to this problem. Summary of the Invention

[0007] The purpose of this invention is to provide a fast transfer structure and control method for a hybrid DC circuit breaker. By increasing the arc voltage through the series connection of the vacuum gap and the gas gap, the current transfer time is reduced and the current transfer capability is improved, thus solving the problems of complex structure and cumbersome control process of hybrid DC circuit breakers.

[0008] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0009] A hybrid DC circuit breaker fast transfer structure includes a vacuum gap, a gas gap, an operating mechanism, a power electronic breaking unit, and a controller. The vacuum gap, the gas gap, and the operating mechanism are connected in series from top to bottom via a pull rod assembly. Vacuum contacts and gas contacts are respectively provided in the vacuum gap and the gas gap. Under the action of the operating mechanism, the pull rod assembly can cause the moving contacts of the vacuum contacts and the gas contacts to move up and down in linkage.

[0010] As a preferred embodiment of the present invention, the pull rod assembly includes a first pull rod, an insulating column, and a second pull rod connected sequentially from top to bottom. The stationary contact of the gas contact is fixedly disposed at the top of the gas gap. The insulating column passes through the top of the gas gap and through the stationary contact of the gas contact to the upper surface of the moving contact of the gas contact. The top of the insulating column is connected to the moving contact of the vacuum contact through the first pull rod. The bottom of the insulating column is connected to the operating mechanism through the second pull rod and through the bottom of the gas gap. The center of the moving contact of the gas contact is fixedly disposed on the second pull rod.

[0011] As a preferred embodiment of the present invention, the first pull rod is provided with a first overtravel, and the second pull rod is provided with a second overtravel.

[0012] As a preferred embodiment of the present invention, the stationary contact of the gas contact includes a first working part, a second working part, and a connecting part. The first working part includes an arc-shaped plate, and one end of the arc-shaped plate is provided with an arc-shaped terminal that fits against the outer side of the arc-shaped plate. The second working part is mirror-image of the first working part, and the connecting part is provided at the other end of the outer side of the arc-shaped plate to form an electrical connection between the first working part and the second working part.

[0013] As a preferred embodiment of the present invention, the connecting part is an arc-shaped connector and is in contact with the outer surface of the arc-shaped plates of the first working part and the second working part.

[0014] As a preferred embodiment of the present invention, an arc traction device is snapped into place at the connection between the arc plate and the arc terminal and the connecting part.

[0015] As a preferred embodiment of the present invention, the arc traction device is an arc-shaped permanent magnet of the same size and polarity.

[0016] As a preferred embodiment of the present invention, the moving contact of the gas contact is provided with chamfers at both ends, and the inner sides of both ends of the arc plate, the outer sides of both ends of the connecting part, and the outer side of the arc terminal are all provided with chamfer grooves at their bottom that match the chamfers, and an arc traction zone is formed between the chamfers and the chamfer grooves.

[0017] As a preferred embodiment of the present invention, an insulating partition is provided between the arc-shaped terminal and the connecting part, as well as between the ports of the two arc-shaped plates.

[0018] A control method for a fast transfer structure of a hybrid DC circuit breaker includes the following steps:

[0019] 1) When a short circuit fault occurs, the controller issues a control command to cause the operating mechanism to pull the lever assembly. At this time, the second overtravel first changes from the compression state to the tension state, the gas contacts separate first, the gas arc is generated, and the arc voltage begins to increase.

[0020] 2) Due to the pulling effect of the second overtravel, the first overtravel also changes from a compression state to a tension state, the vacuum contacts separate, and a vacuum arc is generated. At this time, the arc voltage of the fast transfer structure of the hybrid DC circuit breaker is the sum of the arc voltage of the gas contacts and the arc voltage of the vacuum contacts.

[0021] 3) When the vacuum gap reaches its maximum, the switch is fully open, and the arc voltage of the fast transfer structure of the hybrid DC circuit breaker accelerates the current to the power electronic breaking unit, completing the breaking process.

[0022] The beneficial effects of the present invention through the above technical solutions are as follows:

[0023] 1. This invention utilizes the advantages of fast recovery speed of vacuum medium and high gas arc pressure, and sets the vacuum gap and gas gap in series in the main branch to effectively improve the fault current transfer capability, thereby realizing simple and reliable natural commutation control;

[0024] 2. This invention connects the vacuum gap, gas gap, and operating mechanism in series from top to bottom via a tie rod assembly, effectively reducing the size of the circuit breaker product and simplifying the control mechanism for easier installation and maintenance; it also improves the reliability and stability of the circuit breaker control system.

[0025] 3. By setting two overtravels on the tie rod assembly to form a linkage, the opening and closing process of the two gaps is made faster and more stable;

[0026] 4. The gas contact adopts an eight-contact disc structure, and a spatial magnetic field is formed in the arc traction area through the arc traction device. Under the action of the magnetic field, the arc pressure of the gas contact is stretched and bent, which not only effectively increases the arc voltage, but also makes the spatial layout more concentrated and effectively reduces the assembly volume.

[0027] 5. The moving and stationary contacts of the gas contact are chamfered to increase the contact area, which not only improves the service life of the gas contact, but also facilitates the movement and elongation of the arc to carry a larger short-circuit current. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the structure of the hybrid DC circuit breaker of the present invention.

[0030] Figure 2 This is a top view of the gas contact of the present invention.

[0031] Figure 3 for Figure 2 Cross-sectional view along the AA direction.

[0032] Figure 4 This is a force analysis diagram of the gas contact arc pressure in a magnetic field.

[0033] Figure 5 This is a graph showing the effect of different numbers of gas contacts on the arc voltage.

[0034] Figure 6 This is a schematic diagram showing the current flow direction when the gas contact is disconnected.

[0035] Figure 7 This is a topology diagram of the hybrid DC circuit breaker of the present invention.

[0036] Figure 8 This is a graph showing the arc voltage curve of a vacuum-gas contact short circuit.

[0037] Figure 9 This is a schematic diagram of the arc current transfer model of the hybrid DC circuit breaker of the present invention.

[0038] Figure 10a The waveform diagram shows the breaking time of a traditional hybrid DC circuit breaker.

[0039] Figure 10b The waveform diagram shows the breaking time of the hybrid DC circuit breaker of the present invention.

[0040] Figure 11 This is a graph showing the arc voltage of the gas contact under different gas media.

[0041] In the diagram: 1-vacuum gap, 2-gas gap, 3-operating mechanism, 4-vacuum contact, 5-gas contact, 6-first pull rod, 7-insulating column, 8-second pull rod, 9-first overtravel, 10-second overtravel, 11-insulating pull rod, 51-connecting part, 52-arc plate, 53-arc terminal, 54-arc traction device, 55-insulating partition, 56-chamfered groove, 57-arc traction area. Detailed Implementation

[0042] The foregoing and other technical contents, features and effects of the present invention are described in conjunction with the appendix below. Figure 1 To be continued Figure 11 The detailed description will clearly illustrate this. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the scope of the invention.

[0043] The application principle of the present invention will be described in detail below with reference to the following embodiments.

[0044] like Figure 1 As shown, a hybrid DC circuit breaker fast transfer structure includes a vacuum gap 1, a gas gap 2, an operating mechanism 3, a power electronic breaking unit, and a controller. The vacuum gap 1, gas gap 2, and operating mechanism 3 are connected in series from top to bottom via a pull rod assembly. Vacuum contacts 4 and gas contacts 5 are respectively installed in the vacuum gap 1 and gas gap 2. Under the action of the operating mechanism 3, the pull rod assembly can make the moving contacts of the vacuum contacts 4 and gas contacts 5 move up and down in linkage.

[0045] Specifically, in this invention, the pull rod assembly includes a first pull rod 6, an insulating column 7, and a second pull rod 8 connected sequentially from top to bottom. The stationary contact of the gas contact 5 is fixedly disposed at the top of the gas gap 2. The insulating column 7 passes through the top of the gas gap 2 and through the stationary contact of the gas contact 5 to reach the upper surface of the moving contact of the gas contact 5. The top of the insulating column 7 is connected to the moving contact of the vacuum contact 4 through the first pull rod 6. The bottom of the insulating column 7 is connected to the operating mechanism 3 through the second pull rod 8 and through the bottom of the gas gap 2. The center of the moving contact of the gas contact 5 is fixedly disposed on the second pull rod 8.

[0046] Specifically, the first pull rod 6 is equipped with a first overtravel 9, and the second pull rod 8 is equipped with a second overtravel 10. It can be understood that the two overtravels not only ensure the pressure of the vacuum contact 4 and the gas contact 5 in the normally closed state, but also provide a faster opening speed, ensuring more stable system linkage control.

[0047] Specifically, such as Figure 2 As shown, the stationary contact of the gas contact 5 includes a first working part, a second working part, and a connecting part 51. The first working part includes an arc-shaped plate 52, and an arc-shaped terminal 53 that fits against the outer surface of the arc-shaped plate 52 is provided at one end of the arc-shaped plate 52. The second working part is mirrored with the first working part, and the connecting part 51 is provided at the other end of the outer side of the arc-shaped plate 52 for forming an electrical connection between the first working part and the second working part.

[0048] To ensure the stability of the electrical connection between the first working part and the second working part, the connecting part 51 is configured as an arc-shaped connector and is attached to the outer surface of the arc-shaped plate 52 of the first working part and the second working part.

[0049] It is understandable that, in order to increase the arc voltage of the gas contact 5, an arc traction device 54 is snapped into place at the connection between the arc plate 52 and the arc terminal 53 and the connecting part 51.

[0050] Furthermore, such as Figure 3As shown, the moving contact of the gas contact 5 has chamfers at both ends. The inner sides of both ends of the arc plate 52, the outer sides of both ends of the connecting part 51, and the outer side of the arc terminal 53 are all provided with chamfer grooves 56 at their bottom that match the chamfers. An arc traction zone 57 is formed between the chamfers and the chamfer grooves 56.

[0051] The arc traction device 54 is configured as an arc-shaped permanent magnet of the same size and polarity. Taking an arc-shaped permanent magnet with the outer side as the N pole and the inner side as the S pole as an example, the specific working principle is as follows: the magnetic field lines of the arc-shaped permanent magnet spread outward from the N pole surface and finally reach the S pole surface. Therefore, the arc-shaped permanent magnet will form a spatial magnetic field within the arc traction zone 57. (Refer to...) Figure 4 As shown, when the moving and stationary contacts of the gas contact 5 are opened, an electric arc is generated on both sides of the moving contact. At this time, the charged particles in the electric arc are deflected in their trajectory due to the Lorentz force F in the arc traction zone. The direction of the force follows the left-hand rule, which causes the entire electric arc to be stretched and bent under the action of the Lorentz force, thereby increasing the length of the electric arc and thus increasing the arc voltage.

[0052] It is understandable that by matching the chamfer with the chamfer groove, the contact surface of the moving and stationary contacts of the gas contact 5 is increased, which can not only improve the service life of the gas contact 5, but also facilitate the movement and elongation of the arc, thereby allowing a larger short-circuit current to flow.

[0053] In this embodiment, the gas contact 5 forms an eight-contact structure by matching four moving contacts with four stationary contacts. When the gas contact 5 is open, the chamfers on both sides of each moving contact form two arc segments between them and their corresponding stationary contacts, thus generating a total of eight arc segments. These eight arc segments are connected in series within the eight-contact structure, significantly increasing the arc voltage when the gas contact 5 is open. The effect of different contact numbers on the arc voltage of the gas contact 5 is as follows: Figure 5 As shown. At the same time, the first working part, the second working part, and the connecting part 51 of the gas contact 5 form a disc-shaped structure, thereby realizing a more concentrated layout of the eight-contact structure and reducing the product size.

[0054] During the opening and closing of the gas contact 5, the electric arcs on both sides of the adjacent contacts may come into contact, causing secondary conduction. Therefore, insulating partitions 55 are provided between the arc terminal 53 and the connecting part 51, as well as between the ports of the two arc plates 52.

[0055] It is understandable that, in order to prevent the current generated when the operating mechanism 3 is opened and closed from flowing into the gas gap 2 and the vacuum gap 1, an insulating rod 11 is provided between the second rod 8 and the operating mechanism 3, so as to form insulation between the operating mechanism 3 and the two gaps.

[0056] The control method for the fast transfer structure of a hybrid DC circuit breaker includes the following steps:

[0057] 1) When a short circuit fault occurs, the controller issues a control command to cause the operating mechanism 3 to pull the lever assembly. At this time, the second overtravel 10 first changes from a compressed state to a stretched state, the gas contact 5 separates first, and the fault current flows in from one arc-shaped terminal 53 of the gas contact 5 and flows out from the other arc-shaped terminal 53. Figure 6 As shown, a gas arc is generated, and the arc voltage begins to increase;

[0058] 2) Due to the pulling effect of the second overtravel 10, the first overtravel 9 also changes from a compressed state to a stretched state, the vacuum contact 4 separates, and a vacuum arc is generated. At this time, the arc voltage of the fast transfer structure of the hybrid DC circuit breaker is the arc voltage U of the gas contact 5. arc-g With vacuum contact 4 arc pressure U arc-v sum;

[0059] 3) such as Figure 6 As shown, when vacuum gap 1 reaches its maximum, the switch is fully open. The arc voltage of the fast transfer structure of the hybrid DC circuit breaker accelerates the current to the power electronic breaking unit. The vacuum and gas gaps enter the dielectric recovery stage. After the dielectric recovery is completed, the vacuum gap mainly bears the transient recovery voltage. At this time, the IGBT in the power electronic breaking unit is turned off, and the current is transferred to the energy-absorbing component MOV. The energy-absorbing component MOV absorbs the energy stored in the fault system inductor until the current crosses zero, completing the entire breaking process. Because the dielectric recovery of vacuum gap 1 is fast, the vacuum gap 1 bears the main transient breaking voltage in the transient recovery stage after disconnection.

[0060] In the above control process, such as Figure 8 As shown, the hybrid DC circuit breaker's fast transfer structure uses a series connection of a vacuum gap and a gas gap to effectively increase the arc voltage. By setting the series connection of the vacuum gap and the gas gap in the main branch, it enables the switching of circuit current and the reliable protection and control of the DC circuit.

[0061] This structure increases the arc voltage by connecting a vacuum gap and a gas gap in series, and transfers the current to the power electronic switching unit through natural commutation, thereby achieving the transfer and absorption of fault current. Its current transfer rate dI g The formula for calculating / dt is as follows:

[0062]

[0063] In equation (1), U s For the on-state voltage drop of the power electronic switch, L HSS L is the equivalent inductance of the hybrid DC circuit breaker. s The equivalent inductance of a power electronic switch is shown in the arc current transfer model as follows: Figure 9 As shown. Under the same electrical environment, U s L HSS With L s Since it is a fixed value, when the gas contact arc pressure U arc-g With vacuum contact arc voltage U arc-v The larger the sum, the greater dI. g The larger / dt is, the faster the arc current transfer rate.

[0064] Therefore, see Figure 10a , 10b As shown, compared with traditional hybrid DC circuit breakers, the fast transfer structure of the hybrid DC circuit breaker of this invention can effectively reduce the transfer time of short-circuit current and improve the current transfer capability.

[0065] In practice, the arc voltage of the gas contact can be adjusted by changing the medium within the gas gap. For example, different gases can be introduced, such as CO2, dry air, N2, or a hydrogen-nitrogen mixture (H2:N2 = 2:3). The arc voltage varies depending on the gas medium. Figure 11 As shown.

[0066] In summary, this invention utilizes the advantages of fast vacuum medium recovery speed and high gas arc pressure, and sets the vacuum gap and gas gap in series in the main branch to effectively improve the fault current transfer capability. By setting the vacuum gap, gas gap and operating mechanism in series from top to bottom through a pull rod assembly, the size of the circuit breaker product is effectively reduced, and the control mechanism is simpler, making it easier to install and maintain. At the same time, it improves the reliability and stability of the circuit breaker control system, thereby achieving simple and reliable natural commutation control.

[0067] The above is a further detailed description of the present invention in conjunction with specific embodiments. It should not be considered that the specific implementation of the present invention is limited to this. For those skilled in the art to which the present invention pertains and related fields, any extensions, operation methods, and data substitutions made based on the technical solution concept of the present invention should fall within the protection scope of the present invention.

Claims

1. A hybrid DC circuit breaker fast transfer structure, comprising a vacuum gap (1), a gas gap (2), an operating mechanism (3), a power electronic breaking unit, and a controller, characterized in that: The vacuum gap (1), the gas gap (2) and the operating mechanism (3) are connected in series from top to bottom through a pull rod assembly. Vacuum contacts (4) and gas contacts (5) are respectively provided in the vacuum gap (1) and the gas gap (2). Under the action of the operating mechanism (3), the pull rod assembly can make the moving contacts of the vacuum contacts (4) and the gas contacts (5) move up and down in linkage. The pull rod assembly includes a first pull rod (6), an insulating column (7), and a second pull rod (8) connected sequentially from top to bottom. The stationary contact of the gas contact (5) is fixedly disposed at the top of the gas gap (2). The insulating column (7) passes through the top of the gas gap (2) and through the stationary contact of the gas contact (5) to the upper surface of the moving contact of the gas contact (5). The top of the insulating column (7) is connected to the moving contact of the vacuum contact (4) through the first pull rod (6). The bottom of the insulating column (7) is connected to the operating mechanism (3) through the second pull rod (8) and through the bottom of the gas gap (2). The center of the moving contact of the gas contact (5) is fixedly disposed on the second pull rod (8). The first pull rod (6) is provided with a first overtravel (9), and the second pull rod (8) is provided with a second overtravel (10). The stationary contact of the gas contact (5) includes a first working part, a second working part, and a connecting part (51). The first working part includes an arc plate (52), and one end of the arc plate (52) is provided with an arc terminal (53) that fits against the outer side of the arc plate (52). The second working part is mirror-image of the first working part, and the connecting part (51) is provided at the other end of the outer side of the arc plate (52) for forming an electrical connection between the first working part and the second working part. The connecting part (51) is an arc-shaped connector and is attached to the outer surface of the arc plate (52) of the first working part and the second working part; an arc traction device (54) is snapped into the connection between the arc plate (52) and the arc terminal (53) and the connecting part (51); the arc traction device (54) is an arc-shaped permanent magnet of the same size and polarity.

2. The hybrid DC circuit breaker fast transfer structure according to claim 1, characterized in that: The moving contact of the gas contact (5) has chamfers at both ends. The inner sides of both ends of the arc plate (52), the outer sides of both ends of the connecting part (51) and the outer side of the arc terminal (53) are all provided with chamfer grooves (56) matching the chamfers at their bottom. An arc traction zone (57) is formed between the chamfer and the chamfer groove (56).

3. The hybrid DC circuit breaker fast transfer structure according to claim 2, characterized in that: An insulating partition (55) is provided between the arc-shaped terminal (53) and the connecting part (51), and between the ports of the two arc-shaped plates (52).

4. The control method for a hybrid DC circuit breaker fast transfer structure according to any one of claims 1-3, characterized in that, Includes the following steps: 1) When a short circuit fault occurs, the controller issues a control command to make the operating mechanism (3) pull the lever assembly. At this time, the second overtravel (10) first changes from the compression state to the tension state, the gas contact (5) separates first, the gas arc is generated, and the arc voltage begins to increase. 2) Under the pulling action of the second overtravel (10), the first overtravel (9) also changes from the compression state to the tension state, the vacuum contact (4) separates, and a vacuum arc is generated. At this time, the arc voltage of the fast transfer structure of the hybrid DC circuit breaker is the sum of the arc voltage of the gas contact (5) and the arc voltage of the vacuum contact (4). 3) When the vacuum gap (1) reaches its maximum, the switch is fully opened, and the arc voltage of the fast transfer structure of the hybrid DC circuit breaker accelerates the current to the power electronic breaking unit, thus completing the breaking process.

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