High di / dt magnetic control thyristor switching device applied to field inversion and control method

Abstract

The invention provides a high di / dt magnetically controlled thyristor switching device applied to field inversion and a control method. The device comprises a high-voltage pulse capacitor, a main thyristor branch, a magnetic switch and a demagnetizing loop. Wherein the main thyristor branch comprises a main thyristor, and the anode of the main thyristor is connected to the anode of the high-voltage pulse capacitor. The magnetic switch is connected in series with the main thyristor and forms a main discharge loop together with a load; the magnetic switch is composed of at least one magnetic core with a rectangular hysteresis loop and a coil wound on the magnetic core. And the demagnetizing loop is coupled with the magnetic switch and is used for reversely demagnetizing the magnetic core before discharging so as to pull the magnetic induction intensity of the magnetic core to a reverse residual magnetism state. According to the invention, by adopting a mechanism of cooperation of magnetic switch delay buffering and reverse demagnetization presetting, while a conventional thyristor is protected from initial high di / dt impact, the inherent current rise rate limitation of a device is broken through, rapid-response large-current pulse output is realized, and the comprehensive cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of high-power pulse power technology, and in particular to a high di / dt magnetically controlled thyristor switching device and control method for field reversal. Background Technology

[0002] Field-reversed configuration (FRC) is a magnetic confinement fusion device with high specific pressure and a simple linear structure. FRC utilizes the interaction between the plasma's own magnetic field and an external magnetic field to form a closed-loop confinement structure, eliminating the need for a large number of toroidal magnets like a tokamak. In the typical formation and maintenance of an FRC, a pulsed current with a high rate of rise (e.g., on the order of 10 kA / µs) and a large amplitude (e.g., 100 kA) is usually applied to the external magnetizing coil. This pulse is used to establish or reverse the magnetic field, inducing a reversed plasma current layer, thereby forming the FRC configuration.

[0003] Currently, the mainstream switching elements for generating such large pulse currents are mostly conventional thyristors or integrated gate commutated thyristors (IGCTs). Among them, IGCTs have high di / dt tolerance (up to 20kA / µs), but their manufacturing cost is relatively high. Since large devices such as FRCs typically require a large number of semiconductor switches, using IGCTs makes it difficult to control the overall system cost. Conventional thyristors are relatively inexpensive, but they have inherent technical limitations: their current rise rate is limited (typically around 3kA / µs). If directly applied to high-power pulse discharge circuits, excessively high initial di / dt can easily cause the current to concentrate in a localized area of ​​the die during the initial conduction phase, leading to localized overheating or even die damage. This not only limits the rise rate of the pulse current but also affects the stable operation of the system. Furthermore, related experiments place high demands on the timing accuracy, stability, and repeatability of the pulse current.

[0004] To alleviate the di / dt limitation of thyristors, existing technical solutions mainly include: (1) Using multiple thyristors in parallel to share the total current, but this method faces the technical challenge of difficulty in sharing current among devices, which increases the circuit complexity and debugging cost of the system; (2) A magnetic switch or saturated reactor with a certain saturation inductance is connected in series in the main circuit of the thyristor to limit the di / dt of the initial step by utilizing its high impedance characteristics before saturation. However, although the traditional series saturated reactor scheme can protect the thyristor to a certain extent, it often significantly prolongs the overall rise time of the current, making it difficult to meet the requirements of rapid pulse current establishment in specific scenarios (such as FRC formation), and the working loss of the magnetic core is relatively large.

[0005] Therefore, there is an urgent need to develop a new type of switching technology that can output a higher and steeper pulse current than traditional solutions while ensuring the safe operation of the thyristor, in order to meet the requirements of advanced FRC devices for rapid magnetic field establishment. Summary of the Invention

[0006] The purpose of this invention is to provide a high di / dt magnetically controlled thyristor switching device and control method for field reversal, which can solve the following technical problem: how to significantly improve the final di / dt capability of the output current of the entire switching device while fully protecting the thyristor from high di / dt impact damage, making it far exceed the rated di / dt value of a single thyristor, and having a faster current build-up speed.

[0007] The core concept of this invention is to adopt a collaborative working mode of "magnetic switch preset current + thyristor dominant turn-on", which divides the current rise process into two stages. By utilizing the characteristics of the magnetic switch, which has a very large inductance before saturation and an extremely low impedance after saturation, a large current preset pulse is "instantly transferred" to the thyristor. This forces the thyristor to almost "instantly" bear the entire main current under the condition that there is already a large holding current, thereby bypassing its own di / dt limit and achieving an ultra-high rise rate of the total output current.

[0008] To achieve the above objectives, the present invention provides a high di / dt magnetically controlled thyristor switching device for field reversal, comprising, High-voltage pulse capacitor; The main thyristor branch includes a main thyristor, the anode of which is connected to the positive terminal of the high-voltage pulse capacitor; A magnetic switch is connected in series with the main thyristor and together with the load forms the main discharge circuit; the magnetic switch consists of at least one magnetic core with a rectangular hysteresis loop and a coil wound thereon. A demagnetizing circuit, coupled to the magnetic switch, is used to reverse demagnetize the magnetic core before discharge, so as to pull the magnetic induction intensity of the magnetic core to a reverse residual magnetization state.

[0009] In one embodiment of the present invention, the specific structure of the demagnetizing circuit includes: DC power supply, current-limiting resistor, isolation inductor, and capacitor; During the discharge process in the main discharge circuit, the isolation inductor serves to isolate the voltage, and the capacitor is used to clamp the voltage of the DC power supply and the current-limiting resistor in series.

[0010] In one embodiment of the present invention, a pre-charge power supply is connected to the high-voltage pulse capacitor for charging the high-voltage pulse capacitor to a specified high voltage.

[0011] In one embodiment of the present invention, a driving circuit is connected to the main thyristor and is used to output a driving signal to turn on the main thyristor. The magnetic switch is configured such that its inductance increases during the forward magnetization step to withstand the partial voltage of the high-voltage pulse capacitor, thereby reserving 1-3µs of conduction time for the main thyristor.

[0012] In one embodiment of the present invention, the magnetic switch provides a reserved conduction time for the main thyristor. The formula for the volt-second characteristic of magnetic components is satisfied:

[0013] in, The number of coil turns. The cross-sectional area of ​​the magnetic core is... This represents the change in magnetic flux density obtained by the magnetic core. This refers to the voltage that the magnetic switch can withstand.

[0014] In one embodiment of the present invention, the reverse remanent magnetization state of the magnetic core is such that the magnetic flux density of the magnetic core is pulled to a certain value. Place; The reverse demagnetizing effect of the demagnetizing circuit results in an increase in magnetic flux obtained by the magnetic core. The range is 1.8-2.7T; The initial inductance of the magnetic switch during the forward magnetization step is not less than 100uH.

[0015] In one embodiment of the present invention, the core material with a rectangular hysteresis loop is an iron-based amorphous or nanocrystalline alloy.

[0016] In one embodiment of the present invention, the device is applied to the plasma formation and maintenance system of a field inversion configuration device in the field of controlled nuclear fusion, for injecting pulsed current into the external magnetization coil of the system.

[0017] A control method for a high di / dt magnetically controlled thyristor switch device applied to a field-reverse position is implemented based on the aforementioned high di / dt magnetically controlled thyristor switch device applied to a field-reverse position. The method includes the following steps: S1. Reverse demagnetization step: The demagnetization circuit starts working, demagnetizes the magnetic core, and pulls the magnetism to the reverse residual magnetism state; S2. Forward magnetization step: The drive circuit gives a signal to drive the main thyristor to conduct. At this time, the magnetic switch is in the forward magnetization step and has a large inductance, which can withstand the voltage of the high voltage pulse capacitor, and reserve 1-3us conduction time for the main thyristor.

[0018] S3. Switching and High di / dt Output Steps: After the conduction time, the magnetic core is fully saturated, the magnetic switch is close to short-circuited, and the current preset pulse is instantly transferred to the main thyristor, forcing the main thyristor to bear the entire main current, thereby realizing high di / dt pulse current output.

[0019] In one embodiment of the present invention, in the S2 forward magnetization step, the magnetic switch reserves a preset delay time of 1-3 μs for the main thyristor; Before implementation, the magnetic core cross-sectional area and coil turns of the magnetic switch are pre-configured according to the volt-second characteristic formula, so that the magnetic core does not saturate within the preset delay time.

[0020] The present invention has the following beneficial effects: (1) Effectively improves the current rise rate and reduces the risk of device damage: This invention adopts a mechanism that combines magnetic switch delay buffering with reverse demagnetization preset. It utilizes the large inductance characteristic of the magnetic switch during the forward magnetization stage to reserve an appropriate conduction time for the thyristor. After the thyristor conducts, the magnetic switch saturates and presents low impedance, transferring the preset large current pulse to the thyristor, forcing it to bear the main current under the condition that a large holding current already exists. This mechanism significantly improves the di / dt of the device's output current, which can reach 10kA / us and above in experimental tests. At the same time, it effectively avoids the overheating or burnout phenomenon caused by the current concentration in a local area of ​​the die during the initial conduction of conventional thyristors.

[0021] (2) Improved response speed of pulse current: Compared with the technical solution of connecting a traditional saturated reactor in series in the main circuit, the magnetic switch in this invention is almost short-circuited after saturation at a preset time, which alleviates the defect that the overall current rise time is significantly prolonged in the traditional solution. Under the premise of ensuring the safe operation of the thyristor, this design can output a higher and steeper pulse current than the traditional solution, which better meets the timing and performance requirements of the field inversion device for the rapid establishment of the magnetic field.

[0022] (3) Optimization of device size and material cost: This invention introduces a demagnetizing circuit to pull the magnetism of the magnetic core to a reverse remanent state before the main discharge stage. Based on the volt-second characteristic principle of magnetic elements, this reverse pre-setting operation enables the magnetic core to obtain a larger magnetic flux increment ΔB during the forward magnetization stage. Under the condition of meeting the requirements of the same withstand voltage and reserved conduction time, the larger magnetic flux increment helps to reduce the required magnetic core cross-sectional area, thereby optimizing the physical volume of the magnetic switch.

[0023] (4) Reduced system complexity and construction cost: The present invention can achieve high di / dt pulse output using conventional thyristors, avoiding the problem of high system cost caused by the extensive use of gate commutated thyristors (IGCT), and can reduce the cost by about 60%. In addition, compared with the existing solution of sharing the current by connecting multiple thyristors in parallel, the topology of the present invention avoids the current sharing problem caused by parallel connection, which helps to reduce the circuit complexity and overall cost of the entire pulse discharge system.

[0024] In summary, by employing a mechanism that combines magnetic switch delay buffering with reverse demagnetization preset, this invention effectively protects conventional thyristors from initial high di / dt impacts and reduces overall system costs, while overcoming the inherent current rise rate limitation of devices, achieving fast-response high-current pulse output, and optimizing the overall physical size of the device. Attached Figure Description

[0025] Figure 1 A block diagram of a high di / dt magnetically controlled thyristor switching device applied to a field-reversed position, according to an embodiment of the present invention, is disclosed. Figure 2 A flowchart of a control method for a high di / dt magnetically controlled thyristor switch device applied to a field-reversed position, according to an embodiment of the present invention, is disclosed. Figure 3 This diagram illustrates a second embodiment of a high di / dt magnetically controlled thyristor switching device applied to a field-reverse position according to an embodiment of the present invention. Figure 4 The invention discloses a magnetic core BH curve for a high di / dt magnetically controlled thyristor switching device applied to a field-reverse position according to an embodiment of the present invention; Figure 5 A schematic diagram of experimental results for a high di / dt magnetically controlled thyristor switching device applied to a field-reversed position according to an embodiment of the present invention is shown. Figure 6 The present invention discloses a timing diagram of a high di / dt magnetically controlled thyristor switch device applied to the field inversion position according to an embodiment of the present invention.

[0026] Figure Labels

[0027] 1. Pre-charge power supply; 2. Drive circuit; 3. High voltage pulse capacitor; 4. Main thyristor; 5. Magnetic switch; 6. Load; 7. Demagnetizing circuit; 71. DC power supply; 72. Current limiting resistor; 73. Isolation inductor; 74. Capacitor. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0029] In the first embodiment of the present invention, as Figure 1 As shown, a high di / dt magnetically controlled thyristor switching device applied to the field inversion position includes a high-voltage pulse capacitor 3, a main thyristor branch, a magnetic switch 5, and a demagnetizing circuit 7. In this preferred embodiment, di / dt represents the rate of change of current, i.e., the speed at which the current rises or falls. i represents current, typically measured in amperes (A) or kiloamperes (kA). t represents time, typically measured in seconds (s) or microseconds (μs). D represents the derivative. di / dt is the derivative of current i with respect to time t, representing how much the current changes per unit time. Its commonly used units are A / μs or kA / μs.

[0030] The main thyristor branch includes a main thyristor 4, whose anode is connected to the positive terminal of the high-voltage pulse capacitor 3.

[0031] A magnetic switch 5, connected in series with the main thyristor 4, forms the main discharge circuit together with the load 6. The magnetic switch 5 consists of at least one magnetic core with a rectangular hysteresis loop and a coil wound on it. The magnetic switch 5 is configured such that, in the initial step when the main thyristor 4 is triggered to conduct, the magnetic core is in a positively magnetized and unsaturated state, presenting a high impedance to limit the initial current rise rate flowing through the main thyristor 4; after a preset delay time, the magnetic core enters a saturated state, presenting a low impedance, to output a pulse current with a high current rise rate. The preset delay time matches the full conduction time of the main thyristor 4.

[0032] The demagnetizing circuit 7, coupled to the magnetic switch 5, is used to demagnetize the magnetic core in the reverse direction before discharge, so as to pull the magnetic induction intensity of the magnetic core to the reverse residual magnetism state.

[0033] In this embodiment, the specific structure of the demagnetizing circuit 7 includes: DC power supply 71, current limiting resistor 72, isolation inductor 73, and capacitor 74; During the discharge process in the main discharge circuit, the isolation inductor 73 serves as a voltage isolation device, and the capacitor 74 is used to clamp the voltage of the DC power supply 71 and the current-limiting resistor 72 in series.

[0034] In this embodiment, the pre-charging power supply 1 is connected to the high-voltage pulse capacitor 3 and is used to charge the high-voltage pulse capacitor 3 to a specified high voltage. Preferably, in this embodiment, the pre-charging power supply 1 also includes a charging switch.

[0035] In this embodiment, the driving circuit 2 is connected to the main thyristor 4 and is used to output a driving signal to turn on the main thyristor 4. The magnetic switch 5 is configured such that its inductance increases during the forward magnetization step to withstand the voltage of the high-voltage pulse capacitor 3, thereby reserving a 1-3µs turn-on time for the main thyristor 4. In this embodiment, the magnetic switch 5 is used to reserve a turn-on time for the main thyristor 4. The formula for the volt-second characteristic of magnetic components is satisfied:

[0036] in, The number of coil turns. The cross-sectional area of ​​the magnetic core is... This represents the change in magnetic flux density obtained by the magnetic core. This refers to the voltage that the magnetic switch 5 withstands. Preferably, in this embodiment, based on the approximately 3 µs full conduction time requirement of the main thyristor 4, the reserved buffer time for the forward magnetization step of the magnetic switch 5 is set to 3 µs. According to the above formula, under a given operating voltage and required delay, the change in magnetic induction intensity is achieved through reverse demagnetization. Maximizing this can significantly reduce the required core cross-sectional area. This optimizes the overall size and cost of the switching device while ensuring the effectiveness of hardware protection.

[0037] In this embodiment, The reverse remanence of the magnetic core is when the magnetic flux density of the core is pulled to... Place.

[0038] The reverse demagnetizing effect of demagnetizing circuit 7 results in a magnetic flux increment ΔB of 1.8-2.7T for the magnetic core. Preferably, ΔB is 2.7T. Demagnetizing circuit 7 pre-positions the amorphous magnetic core at the reverse remanence point, causing its magnetic flux increment ΔB (i.e., from...) to The change in ΔB reaches 2.7T, where ΔB = =2.7T. Based on the physical formula... Increasing the value of ΔB can effectively reduce the cross-sectional area of ​​the magnetic core.

[0039] The initial inductance of the magnetic switch 5 during the forward magnetization step is not less than 100uH. Preferably, the initial inductance is 200uH. This large inductance design effectively blocks the initial energy surge released by the high-voltage pulse capacitor 3 during the initial conduction period of the main thyristor 4. Theoretical calculations have verified that when the initial inductance reaches 200uH, the peak current of the circuit in the early stage of the pulse can be safely clamped to 10A. Simultaneously, the demagnetizing branch utilizes an LC circuit structure composed of the isolation inductor 73 and capacitor 74 to absorb the transient reverse high voltage generated during the large discharge of the main circuit. The LC circuit can stably clamp the voltage across capacitor 74 below 20V, thereby ensuring the safe operation of the underlying DC power supply 71 and the control hardware.

[0040] In this embodiment, the core material with a rectangular hysteresis loop is an iron-based amorphous or nanocrystalline alloy.

[0041] In this embodiment, the device is applied to the plasma formation and maintenance system of a field inversion configuration device in the field of controlled nuclear fusion, and is used to inject pulsed current into the external magnetization coil of the system.

[0042] A control method for a high di / dt magnetically controlled thyristor switch device applied to the field inversion position is implemented based on the aforementioned high di / dt magnetically controlled thyristor switch device applied to the field inversion position, as follows: Figure 2 As shown, the method includes the following steps: S1. Reverse Demagnetization Step: Demagnetization circuit 7 starts working, demagnetizing the magnetic core and pulling the magnetism to a reverse remanent magnetization state. Preferably, the reverse remanent magnetization state is... .

[0043] S2, Forward Magnetization Step: The drive circuit 2 sends a signal to drive the main thyristor 4 to conduct. At this time, the magnetic switch 5 is in the forward magnetization step and has a large inductance, bearing the voltage of the high-voltage pulse capacitor 3, reserving 1-3µs of conduction time for the main thyristor 4. Preferably, in this embodiment, the magnetic switch 5 is in the forward magnetization step and has a large inductance, bearing almost all the voltage of the high-voltage pulse capacitor 3. Preferably, "almost all the voltage" means that most of the voltage on the high-voltage pulse capacitor 3 (e.g., more than 99.9% of the voltage) is dropped across the magnetic switch 5, which has high impedance. "Almost all the voltage" in the following description can be interpreted as meaning expressed here.

[0044] S3, Switch On and High di / dt Output Steps: After the on-time, the magnetic core is fully saturated, the magnetic switch 5 is close to short-circuited, and the current preset pulse is instantly transferred to the main thyristor 4, forcing the main thyristor 4 to bear the entire main current, thus realizing the high di / dt pulse current output.

[0045] In this embodiment, during the forward magnetization step S2, the magnetic switch 5 has a preset delay time of 1-3 µs reserved for the main thyristor 4.

[0046] Before implementation, the cross-sectional area of ​​the magnetic core and the number of coil turns of the magnetic switch 5 are configured in advance according to the volt-second characteristic formula so that the magnetic core does not saturate within the preset delay time.

[0047] In a second embodiment of the invention, the hardware structure of the device is shown. For example... Figure 3 As shown, the high di / dt switching device in this embodiment mainly comprises two parts: a main discharge circuit and a demagnetizing circuit. The main discharge circuit includes a pre-charged DC power supply (U_pre), a high-voltage pulse capacitor (C1), a main thyristor (Q1), a magnetic switch (MS), and a load. The high-voltage pulse capacitor C1 has a capacitance of 100uF. The main thyristor Q1 is an SCR (Signaled Rectifier). The load is equivalent to an inductor L1 (2uH) and a resistor R1 (1mΩ) connected in series. The anode of the main thyristor Q1 is connected to the positive terminal of the high-voltage pulse capacitor C1, and the cathode of the main thyristor Q1 is connected in series with the magnetic switch MS, forming a closed main discharge circuit with the high-voltage pulse capacitor C1 and the load. The gate of the main thyristor Q1 is connected to a drive circuit. Preferably, the high-voltage pulse capacitor C1 serves as the pulse power supply. The load represents the magnetizing coil of the FRC device. Preferably, the magnetic switch MS is made of an iron-based amorphous magnetic ring with a rectangular hysteresis loop. Through material selection and demagnetization coordination, the magnetic flux density change ΔB available to the magnetic switch MS reaches 2.7T.

[0048] Demagnetizing circuit: Connected to the primary side (or independent demagnetizing winding) of the magnetic switch MS. The demagnetizing circuit includes a DC power supply providing reverse bias, a current-limiting resistor R2 (1mΩ), an isolation inductor L2, and a clamping capacitor C2.

[0049] In the third embodiment of the present invention, a hardware platform was built and a discharge test was conducted to verify the actual effect of the present invention. For example... Figure 3 and Figure 4 As shown in the figure, this embodiment will demonstrate the working process of a high di / dt magnetically controlled thyristor switch device applied to the field inversion position, based on specific experimental data.

[0050] S1. Reverse Demagnetization Step: The host computer controls the pre-charge DC power supply (U_pre) to charge the high-voltage pulse capacitor C1 to a preset high voltage. Preferably, the preset high voltage is 10kV. Simultaneously, as... Figure 4 As shown, the demagnetizing circuit starts working. The demagnetizing circuit demagnetizes through the current-limiting resistor R2 and the isolation inductor L2, pulling the magnetic core operating point of the magnetic switch MS from the initial state to the reverse residual magnetization point. This allows the magnetic core to obtain a large increase in magnetic flux during subsequent forward operation, i.e., from arrive This effectively reduces the required magnetic core cross-sectional area.

[0051] S2, Forward magnetization step: The drive circuit sends a drive signal, and the main thyristor Q1 starts to conduct.

[0052] At this point, the magnetic switch MS enters the positive magnetization stage. For example... Figure 4 As shown, the positive magnetization stage is as follows: The process of climbing along the curve on the right towards point S. During this stage, the magnetic switch exhibits extremely high inductance, bearing almost all the voltage across the high-voltage pulse capacitor C1, while the voltage across the main thyristor Q1 drops to an extremely low level. Preferably, the initial inductance is 200uH.

[0053] The forward magnetization stage provides a buffer conduction time for the thyristor. Preferably, it is known that the thyristor requires approximately 3 µs to fully conduct. Based on the volt-second characteristic formula... The cross-sectional area and number of turns of the magnetic core should be designed appropriately. Among these, The number of coil turns. The cross-sectional area of ​​the magnetic core is... This represents the change in magnetic flux density obtained by the magnetic core. This is the voltage that the magnetic switch withstands. Therefore, under the condition of ΔB = 2.7T, the reserved saturation time Δt of the magnetic switch is set to 3µs.

[0054] S3, Switch On and High di / dt Output Steps: After 3µs, the die of the main thyristor Q1 has achieved uniform conduction over a large area.

[0055] At this point, the magnetic core of the magnetic switch is fully saturated, such as Figure 4 As shown, point S is reached. The impedance of the magnetic switch collapses instantaneously, almost short-circuiting. The main circuit current rises sharply, and the large current preset pulse that was originally blocked by the magnetic switch is instantly transferred to the fully conducting thyristor. The thyristor thus bypasses the physical limitation of the initial di / dt. Experimental tests show that the thyristor remains undamaged even at ≥10kA / µs. Preferably, the physical limitation of the initial di / dt of the thyristor is ≤3kA / µs.

[0056] This device also includes a hardware protection mechanism. During the charging process of the high-voltage pulse capacitor C1, the demagnetizing circuit demagnetizes the magnetism through the current-limiting resistor R2 and the isolation inductor L2, pulling the B value of the magnetic ring to a certain value. During the discharge process of the high-voltage pulse capacitor C1, the isolation inductor L2 in the demagnetizing circuit can effectively isolate the high-voltage transient impact and prevent damage to the demagnetizing DC power supply. At the same time, the clamping capacitor C2 clamps the voltage on the demagnetizing branch (the power supply and R2 series branch) at 20V, ensuring the safe operation of the underlying hardware.

[0057] In the fourth embodiment of the present invention, as Figure 4As shown, the experimental theoretical basis of the third embodiment is illustrated by the BH curve of the magnetic core. This curve describes the hysteresis phenomenon of the magnetic flux density B changing with the magnetic field strength H. The horizontal axis (H) represents the magnetic field strength, one of the variables causing the hysteresis phenomenon due to the external current flowing through the magnetic switch coil. The vertical axis (B) represents the magnetic flux density, reflecting the degree of magnetization within the magnetic core. This represents the saturation magnetic flux density. When the operating point reaches this point, the magnetic core has been saturated with magnetic flux, and the inductance will drop sharply to an extremely low level. Corresponding saturation magnetic induction intensity The magnetic field strength at that time. This represents coercivity, which is the strength of the reverse magnetic field that must be applied to bring the magnetic flux density inside the core back to zero. Represents remanence, which is the magnetic field strength that remains inside the core when the externally applied magnetic field is completely removed (i.e., H = 0), i.e., point R or R' in the figure.

[0058] The conventional initial magnetization process is as follows: (1) Initial stage: Point 0 represents the initial state of the magnetic material when it is completely unmagnetized. At this time, the magnetic induction intensity B = 0 and the magnetic field intensity H = 0. (2) Rising stage: After the coil is energized, as the external magnetic field intensity H increases, the magnetic induction intensity B will rise from point O along the initial magnetization curve, passing through point a and point b in sequence, and finally reaching the positive saturation point S.

[0059] The magnetization process in this embodiment is as follows: (1) Reverse demagnetization stage. In this embodiment, before the formal discharge, the demagnetization circuit works first, forcibly pulling the working point of the magnetic core to the reverse residual magnetization point in the third quadrant. That is, near point R' in the figure. (2) During the forward magnetization stage, after the main thyristor is triggered, the operating point of the magnetic core starts from It rises along the curve on the right and reaches the positive saturation point. , i.e., point S. During this climbing process, the magnetic core can provide a large magnetic flux increment ΔB, preferably ΔB is 1.8-2.7T. At this time, the inductance of the magnetic switch is very large, reserving a safe conduction time of 1-3μs for the thyristor. Preferably, the inductance of the magnetic switch is above 100μH. (3) Saturation burst stage. After 3µs, the operating point reaches point S. At this point, it means that the magnetic core is completely saturated and can no longer accommodate more magnetic flux. The slope of the curve is almost zero. The magnetic switch is equivalent to an instantaneous short circuit, and the stored electrical energy is released to the load at a very high di / dt.

[0060] In the fifth embodiment of the present invention, to illustrate the experimental effects of the third embodiment, as follows: Figure 5The experimental waveform data of the third embodiment are shown below. (1) Experimental conditions: The charging voltage of the pulse capacitor is 10kV. (2) Waveform analysis: In the oscilloscope waveform, the red curve represents the voltage across the main thyristor, preferably 5kV / division. The yellow curve represents the current flowing through the main thyristor, preferably 20kA / division. (3) Test data results: The experimental results show that after the magnetic switch provides a safety buffer delay of about 3us, the discharge current rises rapidly, the peak current reaches 95.6kA, and the di / dt of the output pulse current reaches 10kA / us. (4) Technical effects demonstrated by the experiment: Under the ultra-high di / dt discharge conditions, the main thyristor did not experience any local overheating or damage, and could stably and reliably output extremely steep large current pulses, meeting the experimental requirements of the FRC device for rapid magnetic field establishment.

[0061] In the sixth embodiment of the present invention, in order to more clearly illustrate the collaborative working mechanism of the present invention, combined with Figure 6 This document provides a detailed description of the control timing diagram for the high di / dt magnetically controlled thyristor switching device of the present invention. The timing diagram, from top to bottom, shows the dynamic changes of the demagnetizing circuit control signal, charging control signal, trigger signal, magnetic switch voltage across the magnetic switch, and main circuit discharge current throughout the entire operating cycle. The complete control cycle of the present invention can be divided into the following four stages, described below in the order of the vertical dashed lines from left to right: S1, Reverse Demagnetization Stage: At the beginning of the entire discharge cycle, such as... Figure 6 As shown in the first to second vertical dashed line intervals, the system first controls the demagnetizing circuit signal to output a high-level pulse. During this period, the demagnetizing circuit is activated, injecting demagnetizing current into the magnetic core of the magnetic switch, forcibly pulling the internal magnetization state of the core to the reverse residual magnetization point. After the demagnetizing pulse ends, the demagnetizing circuit is disconnected, preparing sufficient magnetic flux increment for subsequent high-voltage discharge.

[0062] S2, Forward Magnetization Stage: (e.g.) Figure 6 As shown in the figure, the charging signal remains at a high level for a certain period of time and is pulled low at the third vertical dashed line. At this point, it indicates that charging is complete.

[0063] During the valid charging signal period, the external pre-charging power supply begins to charge the high-voltage pulse capacitor in the main discharge circuit with constant current or constant power. When the voltage across the high-voltage pulse capacitor reaches the preset high voltage required for the experiment, the charging signal ends, and the system enters a standby state. Preferably, the preset high voltage is 10kV.

[0064] S3, Switch On and High di / dt Output Stage: (e.g.) Figure 6As shown, at the fourth vertical dashed line, the system sends a trigger pulse (signal changes from low to high) to the gate of the main thyristor. Simultaneously, the magnetic switch voltage waveform instantaneously jumps and remains at a high potential, i.e. Figure 6 The interval between the fourth and fifth vertical dashed lines.

[0065] Upon receiving the trigger signal, the main thyristor begins to conduct. At the instant the circuit is turned on, the magnetic switch, not yet saturated, exhibits extremely high inductance. At this moment, almost all the voltage across the high-voltage pulse capacitor drops across the magnetic switch. Figure 6 During the high-level phase of the magnetic switch voltage, the voltage across the main thyristor drops to a safe low level. This high-voltage plateau provides the thyristor die with ample lateral conduction time. During this period, the discharge current remains at an extremely low level close to zero, preventing the thyristor from experiencing high current surges during partial conduction.

[0066] S4, Core Saturation and Current Burst Stage: (e.g.) Figure 6 As shown, at the fifth vertical dashed line, the waveform of the magnetic switch voltage drops rapidly to near zero. Simultaneously, the discharge current waveform begins to rise sharply and then reaches its peak.

[0067] After the aforementioned pre-defined delay, the magnetic switch completes the forward magnetization process and instantly enters a deep saturation state, causing a sharp drop in its impedance. At this moment, the large current intercepted by the high impedance is released instantly and transferred entirely to the fully conducting main thyristor. Since the thyristor is already in a fully conducting, low-resistance state, it bypasses the initial di / dt physical limitation, generating an extremely high discharge current and completing the high-energy pulse injection into the external load.

[0068] The present invention has the following beneficial effects: (1) Effectively improves the current rise rate and reduces the risk of device damage: This invention adopts a mechanism that combines magnetic switch delay buffering with reverse demagnetization preset. It utilizes the large inductance characteristic of the magnetic switch during the forward magnetization stage to reserve an appropriate conduction time for the thyristor. After the thyristor conducts, the magnetic switch saturates and presents low impedance, transferring the preset large current pulse to the thyristor, forcing it to bear the main current under the condition that a large holding current already exists. This mechanism significantly improves the di / dt of the device's output current, which can reach 10kA / us and above in experimental tests. At the same time, it effectively avoids the overheating or burnout phenomenon caused by the current concentration in a local area of ​​the die during the initial conduction of conventional thyristors.

[0069] (2) Improved response speed of pulse current: Compared with the technical solution of connecting a traditional saturated reactor in series in the main circuit, the magnetic switch in this invention is almost short-circuited after saturation at a preset time, which alleviates the defect that the overall current rise time is significantly prolonged in the traditional solution. Under the premise of ensuring the safe operation of the thyristor, this design can output a higher and steeper pulse current than the traditional solution, which better meets the timing and performance requirements of the field inversion device for the rapid establishment of the magnetic field.

[0070] (3) Optimization of device size and material cost: This invention introduces a demagnetizing circuit to pull the magnetism of the magnetic core to a reverse remanent state before the main discharge stage. Based on the volt-second characteristic principle of magnetic elements, this reverse pre-setting operation enables the magnetic core to obtain a larger magnetic flux increment ΔB during the forward magnetization stage. Under the condition of meeting the requirements of the same withstand voltage and reserved conduction time, the larger magnetic flux increment helps to reduce the required magnetic core cross-sectional area, thereby optimizing the physical volume of the magnetic switch.

[0071] (4) Reduced system complexity and construction cost: The present invention can achieve high di / dt pulse output using conventional thyristors, avoiding the problem of high system cost caused by the extensive use of gate commutated thyristors (IGCT), and can reduce the cost by about 60%. In addition, compared with the existing solution of sharing the current by connecting multiple thyristors in parallel, the topology of the present invention avoids the current sharing problem caused by parallel connection, which helps to reduce the circuit complexity and overall cost of the entire pulse discharge system.

[0072] In summary, by employing a mechanism that combines magnetic switch delay buffering with reverse demagnetization preset, this invention effectively protects conventional thyristors from initial high di / dt impacts and reduces overall system costs, while overcoming the inherent current rise rate limitation of devices, achieving fast-response high-current pulse output, and optimizing the overall physical size of the device.

[0073] The embodiments described above are merely further illustrations of the present invention and are not intended to limit the present invention in any other way. The present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding modifications and changes based on the present invention, but all such modifications and changes should fall within the protection scope of the present invention.

Claims

1. A high di / dt magnetically controlled thyristor switching device applied in the field reversal position, characterized in that, include, High-voltage pulse capacitor; The main thyristor branch includes a main thyristor, the anode of which is connected to the positive terminal of the high-voltage pulse capacitor; A magnetic switch is connected in series with the main thyristor and together with the load forms the main discharge circuit; the magnetic switch consists of at least one magnetic core with a rectangular hysteresis loop and a coil wound thereon. A demagnetizing circuit, coupled to the magnetic switch, is used to reverse demagnetize the magnetic core before discharge, so as to pull the magnetic induction intensity of the magnetic core to a reverse residual magnetization state.

2. The high di / dt magnetically controlled thyristor switching device applied to the field inversion position according to claim 1, characterized in that, The specific structure of the demagnetizing circuit includes: DC power supply, current-limiting resistor, isolation inductor, and capacitor; During the discharge process in the main discharge circuit, the isolation inductor serves to isolate the voltage, and the capacitor is used to clamp the voltage of the DC power supply and the current-limiting resistor in series.

3. The high di / dt magnetically controlled thyristor switching device applied to the field inversion position according to claim 1, characterized in that, A pre-charge power supply, connected to the high-voltage pulse capacitor, is used to charge the high-voltage pulse capacitor to a specified high voltage.

4. The high di / dt magnetically controlled thyristor switching device applied to the field inversion position according to claim 1, characterized in that, A drive circuit, connected to the main thyristor, is used to output a drive signal to turn on the main thyristor. The magnetic switch is configured such that its inductance increases during the forward magnetization step to withstand the voltage of the high-voltage pulse capacitor, thereby reserving 1-3µs of conduction time for the main thyristor.

5. A high di / dt magnetically controlled thyristor switching device for field reversal as described in claim 4, characterized in that, The magnetic switch provides a reserved conduction time for the main thyristor. The formula for the volt-second characteristic of magnetic components is satisfied: in, The number of coil turns. The cross-sectional area of ​​the magnetic core is... This represents the change in magnetic flux density obtained by the magnetic core. This refers to the voltage that the magnetic switch can withstand.

6. A high di / dt magnetically controlled thyristor switching device for field reversal as described in claim 5, characterized in that, The reverse remanent magnetization state of the magnetic core is when the magnetic induction intensity of the magnetic core is pulled to... Place; The reverse demagnetizing effect of the demagnetizing circuit results in an increase in magnetic flux obtained by the magnetic core. The range is 1.8-2.7T; The initial inductance of the magnetic switch during the forward magnetization step is not less than 100uH.

7. A high di / dt magnetically controlled thyristor switching device for field reversal as described in claim 1, characterized in that, The core material with a rectangular hysteresis loop is an iron-based amorphous or nanocrystalline alloy.

8. A high di / dt magnetically controlled thyristor switching device for field reversal according to any one of claims 1 to 7, characterized in that, The device is used in the plasma formation and maintenance system of a field inversion configuration device in the field of controlled nuclear fusion, and is used to inject pulsed current into the external magnetization coil of the system.

9. A control method for a high di / dt magnetically controlled thyristor switch device applied to a field-reverse position, implemented based on the high di / dt magnetically controlled thyristor switch device applied to a field-reverse position as described in any one of claims 1 to 8, characterized in that, The method includes the following steps: S1. Reverse demagnetization step: The demagnetization circuit starts working, demagnetizes the magnetic core, and pulls the magnetism to the reverse residual magnetism state; S2, Forward magnetization step: The drive circuit gives a signal to drive the main thyristor to conduct. At this time, the magnetic switch is in the forward magnetization step and has a large inductance, which can withstand the voltage of the high voltage pulse capacitor, and reserve 1-3us conduction time for the main thyristor. S3. Switching and High di / dt Output Steps: After the conduction time, the magnetic core is fully saturated, the magnetic switch is close to short-circuited, and the current preset pulse is instantly transferred to the main thyristor, forcing the main thyristor to bear the entire main current, thereby realizing high di / dt pulse current output.

10. The control method for a high di / dt magnetically controlled thyristor switching device applied to a field-reversed position according to claim 9, characterized in that, In the S2 forward magnetization step, the magnetic switch reserves a preset delay time of 1-3 µs for the main thyristor; Before implementation, the magnetic core cross-sectional area and coil turns of the magnetic switch are pre-configured according to the volt-second characteristic formula, so that the magnetic core does not saturate within the preset delay time.

Images