Fusion magnet power supply bypass protection device

Abstract

The invention discloses a fusion magnet power supply bypass protection device which comprises a current-limiting energy-shifting resistor and a switch module. The current-limiting energy-shifting resistor is formed by connecting a plurality of resistor branches in parallel, each resistor branch is formed by connecting a plurality of resistors in series, interfaces are reserved among the resistors, and the resistor branches are the same in structure; the more than one switch module is connected in parallel and then is connected in series with the current-limiting energy-shifting resistor; the switch module is formed by connecting a plurality of arm branches in parallel, each arm branch is formed by connecting a silicon controlled rectifier element and a forced current-sharing resistor in series, the resistance value of the forced current-sharing resistor is larger than 10 times of the internal resistance of the silicon controlled rectifier element, and the silicon controlled rectifier element is strongly triggered by adopting a high-frequency pulse train. The device has the advantage of low cost of a half-control device, solves the problem of poor current sharing and triggering consistency of the devices in case of large current, and has good expansion capability and adjustment capability.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy fusion power system research and application, and particularly relates to a bypass protection device for a fusion magnet power supply. Background Art

[0002] Bypass switches have been studied and applied in high-voltage direct current transmission and the fusion field. For example, Li Hua summarized the latest research progress of mechanical switches, artificial current zero-crossing turn-off switches, and fully controlled device hybrid DC switches in fusion by combining domestic and foreign superconducting fusion devices, and pointed out that mechanical switches can be directly configured when the magnet coil current and energy storage are small, and artificial zero-crossing turn-off switches are the mainstream choice when the breaking current is large. Due to the limitations of their own parameters, although fully controlled devices have a future development trend, the technical challenges of improving the breaking voltage and current of the devices still need to be solved, and they have not been widely applied yet. Wen Jialiang designed a new type of high-power bidirectional DC fast 15kA thyristor energy transfer switch for the EAST superconducting tokamak power supply system. Bai Xiaolong proposed a new design idea for the DC switch of a fusion device based on the DC switch of the ITER magnet power system.

[0003] Domestically, the quench protection system of the EAST full-superconducting tokamak coil mainly adopts the mechanical switch method of parallel fuses, and the 15kA thyristor breaking switch developed by the Institute of Plasma Physics, Chinese Academy of Sciences has been successfully applied in the EAST device. The maximum current breaking capacity of the superconducting coil quench protection switch of the China fusion engineering test reactor (CFETR) is expected to be greater than 70kA. Internationally, the DC switch design current parameter of the ITER protection system is about 70kA. The Korea Superconducting Tokamak Advanced Research (KSTAR) device selects a semi-controlled hybrid DC switch with a vacuum circuit breaker in parallel with thyristors, and its current design capacity is nearly 40kA. Japan's JT-60SA uses IGCT as a solid-state switch, and its maximum current breaking capacity can reach 25.7kA.

[0004] Although there are various forms of bypass switches, generally speaking, the action time of the mechanical switch that plays a bypass role will increase with the increase of current, and its thermal stability is poor. The current capacity of a single mechanical switch is small (about 20kA); the cost of the semi-controlled hybrid DC switch is relatively low, but the current sharing and trigger consistency are poor at high currents; the fully controlled hybrid DC switch has controllable turn-off and fast action, but the device price is high, and the ability to withstand current and voltage shocks is insufficient. The method of series-parallel combination for boosting current and expanding current has extremely high expansion costs.

[0005] In addition, the current bypass switches are all custom-developed for a certain specific operating parameter and have no expansion ability, and their ability to adapt to the operation of fusion devices with high density, high specific pressure, and high bootstrap current is poor. Summary of the Invention

[0006] The object of the present invention is to provide a large-capacity bypass switch for fusion magnet power supply protection with relatively low cost and good triggering consistency, and this switch has good adaptability to the operation of fusion devices towards high density, high specific pressure, and high bootstrap current.

[0007] The object of the present invention is achieved through the following technical solution: A bypass protection device for fusion magnet power supply, comprising a current-limiting energy-transferring resistor and a switch module;

[0008] The current-limiting energy-transferring resistor is formed by parallel connection of several (more than two) resistor branches, and each resistor branch is formed by series connection of several resistors. Interfaces are reserved between these resistors, and each resistor branch has the same structure;

[0009] One or more of the above-mentioned switch modules are connected in parallel and then connected in series with the current-limiting energy-transferring resistor;

[0010] The switch module is formed by parallel connection of multiple arm branches. The arm branch is formed by series connection of a thyristor element and a forced current-sharing resistor. The resistance value of the forced current-sharing resistor is greater than 10 times the internal resistance of the thyristor element. The thyristor element is strongly triggered by a high-frequency pulse train, that is, during the transport time period of the thyristor turn-on characteristic particles, it is strongly triggered multiple times to improve the success rate of simultaneous triggering of multiple parallel elements.

[0011] The bypass protection device for fusion magnet power supply of the present invention as a whole belongs to a semi-controlled hybrid DC switch, which has the advantage of low cost of semi-controlled devices. At the same time, by strongly triggering the thyristor devices with high-frequency pulse trains, the success rate of simultaneous triggering of multiple parallel elements is ensured, and the problems of poor current sharing and triggering consistency of semi-controlled devices under large current are solved. In addition, the present invention adopts adjustable resistor current-limiting energy transfer (the resistance value can be adjusted by connecting to the reserved interfaces in the current-limiting energy-transferring resistor) and modular switch units that are convenient for expansion, so that after adding or reducing switch modules, the current exponential decay time of the circuit can be controlled by adjusting the resistance value of the current-limiting energy-transferring resistor, thereby ensuring smooth attenuation of the impact energy and no damage to the fusion device coil and excitation power supply. The good expansion ability and adjustment ability of the bypass protection device of the present invention can well meet the different-stage protection configuration difference requirements of controllable fusion devices towards high density, high specific pressure, and high bootstrap current operation, and realize the flexible supporting application of large-capacity bypass switches in fusion.

[0012] The bypass protection device further includes an anode row and a cathode row. The anode row is connected to the output end of the current-limiting energy-transferring resistor, and there are n (n is greater than or equal to 2) switch module installation positions between the anode row and the cathode row, including at least one reserved position. This structure is designed to facilitate the user to expand the bypass protection device.

[0013] Preferably, the switch module is formed by paralleling one or more than two arms. Each arm includes a positive and a negative busbar and multiple arm branches. The positive busbar is arranged in the middle of the negative busbar, forming a mountain-shaped structure as a whole. The arm branches are symmetrically press-fitted in multiple layers (more than 2 layers) up and down between the positive busbar and the negative busbars on its two sides. The upper end of the positive busbar and the negative busbar opposite to its lower end respectively form positive and negative connection points.

[0014] In the high-current working area, the difference in the on-state volt-ampere characteristics will cause unbalanced component current distribution. Therefore, it is necessary to strictly screen the on-state (forward) peak voltage drop of the parallel components, and try to make the on-state (forward) peak voltage drop difference of the directly parallel thyristors less than 5 mV. When matching the on-state (forward) volt-ampere characteristics of the components, the characteristics in the high-current area are preferably considered. As Figure 1 shown, the thyristor characteristics of the components in different layers from top to bottom of the same arm are arranged in a U shape or a saddle shape to ensure good current sharing in the high-current area.

[0015] Preferably, the current capacity of each switch module is configured to be 100 kA, with 10 arm branches for each arm, press-fitted symmetrically in 5 layers up and down on both sides, and the component current rating ≥ 5000 A.

[0016] The switch module is also equipped with an isolation protection box, and the parallel switch modules are integrated and reinforced through an outer frame to form a high-strength whole.

[0017] Advantageous effects:

[0018] When the bypass protection device of the present invention is in use, as Figure 2 shown, it is integrally connected in parallel to the circuit of the fusion magnet power supply and the fusion device. When a fault occurs or protection is required, the bypass protection device is activated to quickly release the main energy in the fusion device coil. It has the advantages of low cost of semi-controlled devices and solves the problems of poor current sharing and trigger consistency of such devices at high currents. In addition, due to the good expansion ability and regulation ability of the present invention, it can well adapt to the protection strategies of fusion research parameters at each stage, and realize the flexible supporting application of large-capacity bypass protection devices in fusion. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Used to show the influence of the volt-ampere characteristics of thyristor components on current distribution;

[0020] Figure 2 Schematic connection diagram when the bypass protection device of the present invention is in use;

[0021] Figure 3 Schematic structural diagram of the bypass protection device according to the preferred embodiment of the present invention;

[0022] Figure 4Schematic diagram of the current-limiting and energy-transferring resistor R1 of the bypass protection device according to the preferred embodiment of the present invention;

[0023] Figure 5 Schematic diagram of the arm of the switch module of the bypass protection device according to the preferred embodiment of the present invention. Detailed implementation manners

[0024] The present invention will be further described below in conjunction with specific embodiments. It should be noted that the following embodiments are only the preferred embodiments of the present invention and should not limit the scope of implementation of the present invention.

[0025] As Figure 3 shown, the fusion magnet power supply bypass protection device of this embodiment includes a current-limiting and energy-transferring resistor R1, an anode row 11, a cathode row 12, and more than one switch module K connected in parallel between the anode row 11 and the cathode row 12. The anode row 11 is connected to the output terminal a of the current-limiting and energy-transferring resistor R1. Except for the switch module k assembly stations actually occupied between the anode row 11 and the cathode row 12, usually at least one station is reserved to facilitate the expansion of the bypass protection device. Usually, n (n is greater than or equal to 2) switch module k assembly stations are preset between the anode row 11 and the cathode row 12, and it is recommended that n take values from 4 to 5.

[0026] As Figure 4 shown, in this embodiment, the current-limiting and energy-transferring resistor R1 is composed of 4 resistor branches connected in parallel, and each resistor branch is composed of 4 resistors R0 connected in series. Interfaces A, B, and C are reserved between these resistors R0. The composition of each resistor branch in the figure is the same. The resistance value of the current-limiting and energy-transferring resistor R1 can be changed by connecting the reserved interfaces at the same position on each resistor branch, so that when the fault current of the fusion device is large, a larger shunt can be achieved by reducing the resistance value of R1, thereby better protecting the fusion magnet power supply and the fusion device.

[0027] In this embodiment, the current capacity of each switch module is configured to be 100 kA. As Figure 3 shown, each switch module K is composed of 20 arm branches b connected in parallel. The arm branch b is composed of a thyristor element c and a forced current-sharing resistor R connected in series. The resistance value of the forced current-sharing resistor R is greater than 10 times the internal resistance of the thyristor element c. The thyristor element c is strongly triggered by a high-frequency pulse train, that is, during the transport time period of the particles with the turn-on characteristics of the thyristor, multiple strong triggers are performed to improve the success rate of simultaneous triggering of multiple parallel elements. For the thyristor, pay attention to reserving an external optical signal driving interface so that the switch module can be switched on and off by an external comprehensive control.

[0028] If the resistance value of the forced current-sharing resistor is about 10 times different from the slope resistance of the thyristor element, the total resistance value of the inherent slope resistance of the bypass element and the press-fitting influence (contact resistance) can account for about 1 / 11 in a single series branch, which can effectively reduce the element resistance value and the press-fitting influence.

[0029] As Figure 3 、 5 shown, in this embodiment, the 20 arm branches b in each switch module K are paralleled in the following way:

[0030] The switch module K is formed by paralleling two arms K1 and K2. The arms K1 and K2 include positive and negative busbars 13 and 14 and multiple arm branches b. The positive busbar 13 is arranged in the middle of the negative busbar 14, forming a mountain-shaped structure as a whole. 10 arm branches b are symmetrically press-fitted in 5 layers up and down between the positive busbar 13 and the negative busbars 14 on both sides thereof. The upper end of the positive busbar 13 and the negative busbar 14 opposite to its lower end respectively form positive and negative connection points.

[0031] Component selection in the bypass protection device of this embodiment:

[0032] First, clarify the energy parameters of the fusion magnet, the peak value of the impact voltage and the magnitude of the impact peak current.

[0033] For the resistor R0 in the current-limiting and energy-transferring resistor R1, it is wound with a high-resistivity metal.

[0034] Select the switching voltage level of the thyristor element according to the peak value of the impact voltage multiplied by the margin coefficient Kv. In this embodiment, the current capacity of each switch module is configured as 100 kA, with 10 elements per arm, and 2 arms are symmetrically arranged up and down, and the element current level ≥ 5000 A.

[0035] Secondly, try to make the difference in the on-state (forward) peak voltage drop of directly paralleled thyristor elements small, preferably less than 5 mV, and make the forward on-state volt-ampere characteristics of each thyristor element in the large-current region arranged in a U shape or a saddle shape, as Figure 1 shown.

[0036] For the forced current-sharing resistor R, select a stainless steel outer shape with a matching cross-sectional area and length.

[0037] As Figure 3 described, in this embodiment, the current-limiting and energy-transferring resistor R1 and the switch modules are both provided with isolation protection boxes, and each switch module is integrated and reinforced through an outer frame to form a high-strength whole.

[0038] Application Example 1

[0039] The magnet coil of the fusion device is excited by a ±240 kA / 750 V power supply. The impact current of the bypass protection device is expected to be greater than 220 kA, the total time of current exponential decay is less than 10 s, and the peak value of the impact voltage is less than 2000 V. Three 100 kA switch modules are selected, connected to the positive and negative poles respectively, and the outer frame is integrated and strengthened to form a high-strength whole.

[0040] Application Example 2

[0041] A magnet coil in the north is excited by a DC 150 kA / 500 V power supply. The designed capacity of the impact current of the bypass switch is expected to be greater than 150 kA, the total time of current exponential decay is less than 10 s, and the peak value of the impact voltage is less than 1000 V.

[0042] Two 100 kA switch modules are selected, connected to the positive and negative poles respectively, and the outer frame is integrated and strengthened to form a high-strength whole. For the target current decay in each test stage, current-limiting and energy-transferring resistors with different resistances are used to match the line parameters for rapid discharge. When the magnet coil current is in the operating sections of 100 kA and 120 kA, the internal contacts of the current-limiting and energy-transferring resistor R1 are adjusted to adjust the line constant, ensuring smooth decay of the impact energy and no damage to both the coil and the excitation power supply.

[0043] The technology of the present invention is simple and easy to implement. By adopting the combination of adjustable-resistance current-limiting and energy-transferring and switch modules, it can adapt to the protection strategies of fusion research parameters at various stages and realize the flexible supporting application of large-capacity bypass protection devices in fusion. At present, the bypass protection device of the present invention has been successfully applied in the protection of a 160 kA-class fusion magnet power supply.

Claims

1. A bypass protection device for a fusion magnet power supply, characterized in that, It includes a current-limiting energy-transferring resistor and a switching module; The current-limiting energy-transferring resistor is formed by paralleling several resistor branches, and each resistor branch is formed by connecting several resistors in series. There are interfaces reserved between these resistors, and each resistor branch has the same structure; One or more of the above-mentioned switching modules are connected in parallel and then connected in series with the current-limiting energy-transferring resistor; The switching module is formed by paralleling multiple arm branches. The arm branch is formed by connecting a thyristor element in series with a forced current-sharing resistor. The resistance value of the forced current-sharing resistor is greater than 10 times the internal resistance of the thyristor element, and the thyristor element is strongly triggered by a high-frequency pulse train.

2. The bypass protection device according to claim 1, characterized in that, The bypass protection device further includes an anode row and a cathode row. The anode row is connected to the output end of the current-limiting energy-transferring resistor. There are n switching module installation stations between the anode row and the cathode row, including at least one reserved station.

3. The bypass protection device according to claim 2, wherein The switching module is formed by paralleling one or two or more arms. The arm includes a positive and negative busbar and multiple arm branches. The positive busbar is arranged in the middle of the negative busbar, forming a mountain-shaped structure as a whole. The arm branches are symmetrically pressed in m layers up and down between the positive busbar and the negative busbars on its two sides. The upper end of the positive busbar and the negative busbar opposite to its lower end respectively form positive and negative connection points.

4. The bypass protection device according to claim 3, characterized in that, The difference in the forward conduction peak voltage drop of the thyristors, which are the parallel elements in the switching module, is less than 5 mV.

5. The bypass protection device according to claim 4, wherein The forward conduction volt-ampere characteristics of the thyristors in different layers from top to bottom in the same arm show a U-shaped or saddle-shaped arrangement in the large current region.

6. The bypass protection device according to claim 3, characterized in that The current capacity of each switching module is configured to be 100 kA, with 10 arm branches per arm, symmetrically pressed in 5 layers on both sides up and down, and the element current grade ≥ 5000 A.

7. The bypass protection device according to claim 3, wherein, The switching module is also equipped with an isolation protection box, and the parallel switching modules are integrated and reinforced through an outer frame to form a high-strength whole.

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