A control method, system and device for a magnetic commutation switch

Abstract

The present invention discloses a control method, system and device for a magnetic commutation switch, which relates to the technical field of commutation switches. A commutation switch circuit of a magnetic converter is obtained by connecting several parallel MOSFETs and energy transfer resistors in parallel; the actual current value of the magnetic converter is collected; the difference between the actual current value and the preset current value is calculated to obtain the working state of the magnetic converter; the working state includes steady state and demagnetization; when the working state is steady state, the MOSFET is adaptively adjusted to maintain the actual current value; when the working state is demagnetization, the MOSFET is slowly turned off until the actual current value is not greater than the preset current value. According to the embodiment of the present invention, a commutation switch circuit formed based on the variable on-resistance characteristic of MOSFET can be slowly turned off to realize commutation by adjusting the gate-source voltage of MOSFET, and the adjustment range is flexible and controllable, which can eliminate the switching loss and turn-off overvoltage problems in the commutation process.

Description

Technical Field

[0001] The present invention relates to the technical field of commutation switches, and in particular to a control method, system and device for a magnetic commutation switch. Background Art

[0002] At present, magnet power supplies generally use energy transfer resistors to consume the energy stored in magnets, and the magnet current commutation method is mostly a mechanical switch connected in parallel with a resistor. When the power supply is in steady state operation, a large current passes through the mechanical switch. When the magnet needs to be demagnetized, the high-current mechanical switch is disconnected, and the loop current is transferred to the parallel resistor, transferring the energy on the magnet to the resistor for consumption.

[0003] However, for some magnetic power supplies with a slow current change rate and no need to respond quickly to current reduction needs, the cost of using large current mechanical switches for disconnection is relatively high and the power supply cannot be returned to the specified current value for maintenance. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a control method, system and device for a magnetic commutation switch, which can slowly shut down to achieve commutation, so as to eliminate the problems of switch loss and shutdown overvoltage during commutation. Compared with traditional mechanical switches, the embodiments of the present invention can reduce costs under the same current conditions, and its control of commutation is more flexible.

[0005] An embodiment of the present invention provides a control method for a magnetic commutation switch, comprising:

[0006] Connecting several MOSFETs and energy transfer resistors in parallel to obtain a commutation switch circuit of a magnetic converter;

[0007] Collecting the actual current value of the magnetic converter;

[0008] Calculating the difference between the actual current value and the preset current value to obtain the working state of the magnetic converter; the working state includes steady state and demagnetization;

[0009] When the working state is a steady state, adaptively adjusting the MOSFET to maintain the actual current value;

[0010] When the working state is demagnetization, the MOSFET is slowly turned off until the actual current value is no greater than the preset current value.

[0011] As an improvement of the above solution, the commutation switch circuit is connected in series with the magnetic converter to adjust the current of the magnetic converter.

[0012] As an improvement of the above solution, the commutation switch circuit of the magnetic converter is obtained by connecting several MOSFETs and energy transfer resistors in parallel, including:

[0013] Connecting the source electrodes and drain electrodes of a plurality of N-channel MOSFETs in parallel to obtain a first parallel circuit;

[0014] Connecting the first parallel circuit and the energy transfer resistor in parallel to obtain a second parallel circuit;

[0015] The second parallel circuit is connected in series with the superconducting magnet load to obtain a commutation switch circuit.

[0016] As an improvement of the above solution, the calculating the difference between the actual current value and the preset current value to obtain the working state of the magnetic converter includes:

[0017] Calculating the difference between the actual current value and the preset current value;

[0018] When the difference is not greater than zero, it is considered that the working state of the magnetic converter is steady state;

[0019] When the difference is greater than zero, it is considered that the working state of the magnetic converter is demagnetization.

[0020] As an improvement of the above solution, when the working state is a steady state, adaptively adjusting the MOSFET to maintain the actual current value includes:

[0021] When the working state is steady state, the gate-source voltage of the MOSFET is adaptively adjusted to a preset voltage value to maintain the actual current value; at the preset voltage value, the current of the commutation switch circuit mainly passes through the MOSFETs but not the energy transfer resistor.

[0022] As an improvement of the above solution, when the working state is demagnetization, slowly turning off the MOSFET until the actual current value is no greater than the preset current value includes:

[0023] When the working state is demagnetization, the gate-source voltage of each MOSFET is reduced to 0 according to a preset step size to ensure that the actual current value is not greater than the preset current value.

[0024] As an improvement of the above solution, when the working state is demagnetization, slowly turning off the MOSFET until the actual current value is no greater than the preset current value includes:

[0025] When the working state is demagnetization, reducing the gate-source voltage of each MOSFET according to a preset step size;

[0026] If the actual current value is not greater than the preset current value before the gate-source voltage drops to the gate-source threshold voltage, the gate-source voltage is automatically adjusted to commutate the current to the MOSFET to maintain the preset current value;

[0027] If the actual current value is still greater than the preset current value after the gate-source voltage drops to the gate-source threshold voltage, the MOSFET is turned off to transfer the current to the energy transfer resistor.

[0028] The embodiment of the present invention further provides a control system for a magnetic commutation switch, comprising:

[0029] A circuit building module, used for connecting several MOSFETs and energy transfer resistors in parallel to obtain a commutation switch circuit of a magnetic converter;

[0030] A current acquisition module, used for acquiring the actual current value of the magnetic current converter;

[0031] A difference calculation module, used to calculate the difference between the actual current value and the preset current value, and obtain the working state of the magnetic converter; the working state includes steady state and demagnetization;

[0032] A steady-state control module, used for adaptively adjusting the MOSFET to maintain the actual current value when the working state is a steady state;

[0033] The demagnetization control module is used to slowly turn off the MOSFET when the working state is demagnetization until the actual current value is no greater than the preset current value.

[0034] As an improvement of the above solution, the demagnetization control module is specifically used for:

[0035] When the working state is demagnetization, reducing the gate-source voltage of each MOSFET according to a preset step size;

[0036] If the actual current value is not greater than the preset current value before the gate-source voltage drops to the gate-source threshold voltage, the gate-source voltage is automatically adjusted to commutate the current to the MOSFET to maintain the preset current value;

[0037] If the actual current value is still greater than the preset current value after the gate-source voltage drops to the gate-source threshold voltage, the MOSFET is turned off to transfer the current to the energy transfer resistor.

[0038] An embodiment of the present invention also provides a control device for a magnetic commutation switch, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the control method for the magnetic commutation switch as described above when executing the computer program.

[0039] Compared with the prior art, the present invention discloses a control method, system and device for a magnetic commutation switch, which obtains a commutation switch circuit of a magnetic converter by connecting several parallel MOSFETs and energy transfer resistors in parallel; collects the actual current value of the magnetic converter; calculates the difference between the actual current value and the preset current value to obtain the working state of the magnetic converter; the working state includes steady state and demagnetization; when the working state is steady state, the MOSFET is adaptively adjusted to maintain the actual current value; when the working state is demagnetization, the MOSFET is slowly turned off until the actual current value is not greater than the preset current value. By adopting the embodiment of the present invention, commutation can be achieved by slowly shutting down to eliminate the problems of switch loss and shutdown overvoltage during the commutation process. Moreover, compared with traditional mechanical switches, the embodiment of the present invention can reduce costs under the same current conditions, and its control of commutation is also more flexible. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the topological structure of a traditional commutation switch circuit;

[0041] Figure 2 It is a schematic flow chart of the steps of a control method of a magnetic commutation switch provided by an embodiment of the present invention;

[0042] Figure 3 is a schematic diagram of a topological structure of an improved commutation switch circuit provided by an embodiment of the present invention;

[0043] Figure 4 It is a structural schematic diagram of a control system of a magnetic commutation switch provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] In the description of the specification and claims, it is to be understood that the terms first, second, etc. in the specification and claims are only used for the purpose of describing the same technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated, nor necessarily describing the order or time sequence. The terms are interchangeable where appropriate. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0046] See also Figure 1In traditional magnetic commutation switches, a mechanical switch is connected in parallel with an energy transfer resistor, and a buffer circuit unit is also required to prevent the current shock caused by the mechanical switch being turned on and off, which may cause overvoltage damage to the circuit. When the power supply is in steady state operation, a large current passes through the mechanical switch. When the magnet needs to be demagnetized, the large current mechanical switch is disconnected so that the loop current is switched to the parallel energy transfer resistor, and the energy on the magnet is transferred to the energy transfer resistor for consumption. When the current change rate is slow or there is no need to respond quickly to the current reduction demand, the cost of using a large current mechanical switch to disconnect is relatively high and the power supply cannot be returned to the specified current value for maintenance.

[0047] Based on the above considerations, an embodiment of the present invention provides a control method for a magnetic commutation switch. Figure 2 In this embodiment, the control method of the magnetic commutation switch is specifically performed through steps S1 to S5:

[0048] S1. Connect several MOSFETs and energy transfer resistors in parallel to obtain a commutation switch circuit of a magnetic converter.

[0049] It should be noted that, in the embodiment of the present invention, the plurality of MOSFETs are uniformly controlled, and the states of the MOSFETs are consistent. In practical applications, the MOSFETs can also be controlled differently according to the operation requirements. When the plurality of MOSFETs connected in parallel are all in the on state, the internal resistance and on-state voltage drop of the overall MOS module are small, and the loop current basically passes through the MOSFET; when the plurality of MOSFETs connected in parallel are all in the off state, the resistance of the overall MOS module is large, and the loop current basically passes through the energy transfer resistor.

[0050] S2. Collecting the actual current value of the magnetic converter.

[0051] S3. Calculate the difference between the actual current value and the preset current value to obtain the working state of the magnetic converter; the working state includes steady state and demagnetization.

[0052] It should be noted that in the embodiment of the present invention, when the magnetic converter is in a steady-state operation stage or the magnet needs to be excited, the magnetic converter is considered to be in a steady state. When the magnetic converter needs to reduce the current, it is considered to be in a demagnetization stage.

[0053] S4. When the working state is a steady state, adaptively adjust the MOSFET to maintain the actual current value.

[0054] S5. When the working state is demagnetization, slowly turn off the MOSFET until the actual current value is no greater than the preset current value.

[0055] It can be understood that the parallel-connected MOSFETs and the energy transfer resistor are in a parallel relationship. When the total equivalent resistance of the parallel-connected MOSFETs is less than the resistance of the energy transfer resistor, the current in the commutation switch circuit will flow through the MOSFETs and less through the energy transfer resistor. At this time, the current flowing through the magnetic converter depends on the equivalent resistance value.

[0056] When the total equivalent resistance of several MOSFETs in parallel is greater than the resistance of the energy transfer resistor, the current in the commutation switch circuit will flow through the energy transfer resistor and less through several MOSFETs. At this time, the current flowing through the magnetic converter depends on the resistance of the energy transfer resistor.

[0057] Therefore, in the embodiment of the present invention, the current of the magnetic converter can be controlled by adjusting the MOSFET. In the traditional process of commutation through a large current mechanical switch, it is not convenient to operate again during the current reduction process, and the number of mechanical switch operations is limited. The MOS module composed of MOSFET is flexible and controllable. It can operate during the current reduction process and can gradually commutate the current to the energy transfer resistor through gradient, linear and other methods.

[0058] In the above scheme, by adjusting the gate-source voltage of multiple MOSFETs connected in parallel, the commutation can be realized by slowly shutting down, so as to eliminate the switching loss and the problem of overvoltage during the commutation process. Compared with the traditional mechanical switch, the embodiment of the present invention can reduce the cost under the same current condition, and its control of commutation is more flexible.

[0059] As a preferred implementation, see Figure 3 The commutation switch circuit is connected in series with the magnetic converter to adjust the current of the magnetic converter.

[0060] It should be noted that, combined with Figure 1 and Figure 3 The commutation switch circuit described in the embodiment of the present invention can be regarded as replacing the high-current mechanical switch and the buffer circuit unit in the traditional commutation switch circuit with several MOSFETs in parallel. Its structure is relatively simpler and the cost will be greatly reduced. In addition, since the on-resistance of MOSFET has a positive temperature coefficient characteristic and the drain current has a negative temperature coefficient characteristic, when the current of a certain MOSFET increases and starts to heat up, the on-resistance of the MOSFET will increase, and the drain current flowing through the MOSFET will decrease. Several MOSFETs in parallel can achieve natural current sharing and current limiting.

[0061] As a preferred implementation, step S1, connecting several MOSFETs and energy transfer resistors in parallel to obtain a commutation switch circuit of a magnetic converter, comprises:

[0062] Connecting the source electrodes and drain electrodes of a plurality of N-channel MOSFETs in parallel to obtain a first parallel circuit;

[0063] Connecting the first parallel circuit and the energy transfer resistor in parallel to obtain a second parallel circuit;

[0064] The second parallel circuit is connected in series with the superconducting magnet load to obtain a commutation switch circuit.

[0065] It should be noted that, in the embodiment of the present invention, when the gate voltage of the N-channel MOSFET is positive, the MOSFET is turned on, and the current flows from the drain to the source. By connecting the sources of several N-channel MOSFETs in parallel, and connecting the drains of several N-channel MOSFETs in parallel, the MOSFETs in the first parallel circuit obtained have the same structure, so that they can be uniformly controlled by the gate. It should be noted that by adjusting the gate of the MOSFET, the output characteristics of the MOSFET variable resistance region can be used for commutation control.

[0066] In some preferred embodiments, the superconducting magnet load may be equivalent to an inductor.

[0067] As a preferred implementation, step S3, calculating the difference between the actual current value and the preset current value to obtain the working state of the magnetic converter, includes:

[0068] Calculating the difference between the actual current value and the preset current value;

[0069] When the difference is not greater than zero, it is considered that the working state of the magnetic converter is steady state;

[0070] When the difference is greater than zero, it is considered that the working state of the magnetic converter is demagnetization.

[0071] That is, when the actual current value is not greater than the preset current value, the magnetic converter operates in a steady state; when the actual current value is greater than the preset current value, the magnetic converter needs to be demagnetized, and in the embodiment of the present invention, demagnetization is achieved by reducing the current.

[0072] As a preferred implementation, step S4, when the working state is a steady state, adaptively adjusting the MOSFET to maintain the actual current value, includes:

[0073] When the working state is steady state, the gate-source voltage of the MOSFET is adaptively adjusted to a preset voltage value to maintain the actual current value; at the preset voltage value, the current of the commutation switch circuit mainly passes through the MOSFETs but not the energy transfer resistor.

[0074] It should be noted that the preset voltage value is calculated in combination with the steady-state current demand and the MOSFET parameters. When the MOSFET is at the preset voltage value, the current of the commutation switch circuit mainly passes through the MOSFETs instead of the energy transfer resistor. In practical applications, the preset voltage value can be selected so that the control port of the MOSFET automatically adjusts the gate-source voltage to the preset voltage value according to the current change.

[0075] In some preferred embodiments, step S5, when the working state is demagnetization, slowly turning off the MOSFET until the actual current value is no greater than the preset current value, includes:

[0076] When the working state is demagnetization, the gate-source voltage of each MOSFET is reduced to 0 according to a preset step size to ensure that the actual current value is not greater than the preset current value.

[0077] It should be noted that the conventional high-current mechanical switch has only two states, on and off. When the mechanical switch is disconnected, the current will be directly transferred to the energy transfer resistor, and the instantaneous current shock may cause overvoltage damage to the circuit. In the embodiment of the present invention, MOSFET is used for commutation, and the gate-source voltage of MOSFET is gradually reduced by a preset step size, so that slow shutdown can be achieved to eliminate the switching loss and shutdown overvoltage problems during the commutation process.

[0078] In the embodiment of the present invention, the final adjustment target is to reduce the gate-source voltage of each MOSFET to 0, at which time the MOSFET is turned off, and the current of the magnetic converter is determined by the resistance value of the energy transfer resistor. It can be understood that from the perspective of circuit design, when all current flows through the energy transfer resistor, the actual current value must not be greater than the preset current value.

[0079] In some other preferred embodiments, step S5, when the working state is demagnetization, slowly turning off the MOSFET until the actual current value is not greater than the preset current value, includes:

[0080] When the working state is demagnetization, reducing the gate-source voltage of each MOSFET according to a preset step size;

[0081] If the actual current value is not greater than the preset current value before the gate-source voltage drops to the gate-source threshold voltage, the gate-source voltage is automatically adjusted to commutate the current to the MOSFET to maintain the preset current value;

[0082] If the actual current value is still greater than the preset current value after the gate-source voltage drops to the gate-source threshold voltage, the MOSFET is turned off to transfer the current to the energy transfer resistor.

[0083] It should be noted that when a traditional high-current mechanical switch is disconnected, the current will be instantly transferred to the energy transfer resistor, and the final current value is determined according to the resistance of the energy transfer resistor and is a fixed value. In an embodiment of the present invention, when the target current value is reached, the current value can be maintained by turning on the MOSFET, and the current value changes stably and can be adjusted within a certain range to adapt to various current condition demand scenarios, and the demagnetization process is flexible and controllable.

[0084] It should also be noted that when the equivalent resistance value is greater than the resistance value of the energy transfer resistor, the current has basically been gradually transferred to the energy transfer resistor, and the MOSFET can be directly turned off without causing loss problems. Turning off the MOSFET can be adjusting the voltage between the gate and source of the MOSFET to a smaller value or to 0.

[0085] In the embodiment of the present invention, when commutation is required, the gate-source voltage of each MOSFET is gradually reduced synchronously, and the on-resistance calculation formula of the MOSFET in the linear region is used. It can be seen that the equivalent resistance of MOSFET gradually increases. When the equivalent on-resistance of the MOS module is greater than the parallel resistance, the current begins to flow to the parallel resistance. is the ion mobility, is the gate oxide capacitance; is the gate width; is the gate length in the channel direction; is the gate-source voltage; is the gate-source turn-on voltage threshold.

[0086] During the commutation process, the gate-source voltage is gradually reduced until the conductive channel of the MOSFET disappears completely. At this time, the on-resistance of the MOSFET is close to infinity, and the loop current is completely switched to the parallel resistor, and then the MOSFET is turned off. The commutation process only requires linear adjustment of the gate-source voltage of the MOSFET in the MOS module, and the non-linear change of the on-resistance has little effect on the commutation process.

[0087] The commutation process slowly adjusts the gate-source voltage to slowly commutate the current on the MOS module to the resistor, eliminating the turn-off overvoltage caused by loop stray inductance and rapid current changes, thereby ensuring that the MOS module is not broken down by overvoltage.

[0088] A control method for a magnetic commutation switch provided by an embodiment of the present invention is adopted, and a commutation switch circuit is formed based on the variable on-resistance characteristic of MOSFET, so that the operating current range is flexibly adjustable. By adjusting the gate-source voltage of the MOSFET, commutation is achieved by slow shutdown to eliminate switching losses and shutdown overvoltages during the commutation process. Under the same current conditions, the commutation scheme greatly reduces the cost of large-current mechanical switches, reduces conduction losses compared to commutation schemes of semiconductor devices such as thyristors, and has a simple control method without the need to add additional circuits. The current of the demagnetization process of this scheme is flexibly controllable, and the magnetic power supply can be maintained after retreating to a specified current value.

[0089] The embodiment of the present invention provides a control system for a magnetic commutation switch. Figure 4 The control system of the magnetic commutation switch includes a circuit construction module 11, a current acquisition module 12, a difference calculation module 13, a steady-state control module 14 and a demagnetization control module 15, wherein:

[0090] A circuit building module 11 is used to connect several MOSFETs and energy transfer resistors in parallel to obtain a commutation switch circuit of a magnetic converter;

[0091] A current acquisition module 12, used for acquiring the actual current value of the magnetic current converter;

[0092] A difference calculation module 13 is used to calculate the difference between the actual current value and the preset current value to obtain the working state of the magnetic converter; the working state includes steady state and demagnetization;

[0093] A steady-state control module 14, configured to adaptively adjust the MOSFET to maintain the actual current value when the working state is a steady state;

[0094] The demagnetization control module 15 is used to slowly turn off the MOSFET when the working state is demagnetization, until the actual current value is not greater than the preset current value.

[0095] As a preferred implementation, the commutation switch circuit is connected in series with the magnetic converter to adjust the current of the magnetic converter.

[0096] As a preferred implementation, the circuit building module 11 is specifically used for:

[0097] Connecting the source electrodes and drain electrodes of a plurality of N-channel MOSFETs in parallel to obtain a first parallel circuit;

[0098] Connecting the first parallel circuit and the energy transfer resistor in parallel to obtain a second parallel circuit;

[0099] The second parallel circuit is connected in series with the superconducting magnet load to obtain a commutation switch circuit.

[0100] As a preferred implementation, the difference calculation module 13 is specifically used for:

[0101] Calculating the difference between the actual current value and the preset current value;

[0102] When the difference is not greater than zero, it is considered that the working state of the magnetic converter is steady state;

[0103] When the difference is greater than zero, it is considered that the working state of the magnetic converter is demagnetization.

[0104] As a preferred implementation, the steady-state control module 14 is specifically used for:

[0105] When the working state is steady state, the gate-source voltage of the MOSFET is adaptively adjusted to a preset voltage value to maintain the actual current value; at the preset voltage value, the current of the commutation switch circuit mainly passes through the MOSFETs but not the energy transfer resistor.

[0106] As a preferred implementation, the demagnetization control module 15 is specifically used for:

[0107] When the working state is demagnetization, the gate-source voltage of each MOSFET is reduced to 0 according to a preset step size to ensure that the actual current value is not greater than the preset current value.

[0108] As another preferred implementation, the demagnetization control module 15 is specifically used for:

[0109] When the working state is demagnetization, reducing the gate-source voltage of each MOSFET according to a preset step size;

[0110] If the actual current value is not greater than the preset current value before the gate-source voltage drops to the gate-source threshold voltage, the gate-source voltage is automatically adjusted to commutate the current to the MOSFET to maintain the preset current value;

[0111] If the actual current value is still greater than the preset current value after the gate-source voltage drops to the gate-source threshold voltage, the MOSFET is turned off to transfer the current to the energy transfer resistor.

[0112] A control system for a magnetic commutation switch provided by an embodiment of the present invention is adopted, and a commutation switch circuit is formed based on the variable on-resistance characteristic of MOSFET, so that the operating current range is flexibly adjustable. By adjusting the gate-source voltage of the MOSFET, commutation is achieved by slow shutdown to eliminate switching losses and shutdown overvoltages during the commutation process. Under the same current conditions, the commutation scheme greatly reduces the cost of large-current mechanical switches, reduces conduction losses compared to commutation schemes of semiconductor devices such as thyristors, and has a simple control method without the need to add additional circuits. The current of the demagnetization process of this scheme is flexibly controllable, and the magnetic power supply can be maintained after retreating to a specified current value.

[0113] An embodiment of the present invention also provides a control device for a magnetic commutation switch, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, a control method for a magnetic commutation switch as described above is implemented. The working principles and beneficial effects of the two correspond one to one, and thus will not be elaborated upon.

[0114] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0115] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A control method for a magnetic commutation switch, characterized in that: include: Connecting several MOSFETs and energy transfer resistors in parallel to obtain a commutation switch circuit of a magnetic converter; Collecting the actual current value of the magnetic converter; Calculating the difference between the actual current value and the preset current value to obtain the working state of the magnetic converter; the working state includes steady state and demagnetization; When the working state is a steady state, adaptively adjusting the MOSFET to maintain the actual current value; When the working state is demagnetization, slowly turning off the MOSFET until the actual current value is no greater than the preset current value; When the working state is demagnetization, slowly turning off the MOSFET until the actual current value is no greater than the preset current value includes: When the working state is demagnetization, the gate-source voltage of each MOSFET is reduced to 0 according to a preset step size to ensure that the actual current value is not greater than the preset current value; or, When the working state is demagnetization, reducing the gate-source voltage of each MOSFET according to a preset step size; If the actual current value is not greater than the preset current value before the gate-source voltage drops to the gate-source threshold voltage, the gate-source voltage is automatically adjusted to commutate the current to the MOSFET to maintain the preset current value; If the actual current value is still greater than the preset current value after the gate-source voltage drops to the gate-source threshold voltage, the MOSFET is turned off to transfer the current to the energy transfer resistor.

2. A control method for a magnetic commutation switch according to claim 1, characterized in that: The commutation switch circuit is connected in series with the magnetic converter to adjust the current of the magnetic converter.

3. A control method for a magnetic commutation switch according to claim 1, characterized in that: The commutation switch circuit of the magnetic converter is obtained by connecting several parallel MOSFETs and energy transfer resistors in parallel, including: Connecting the source electrodes and drain electrodes of a plurality of N-channel MOSFETs in parallel to obtain a first parallel circuit; Connecting the first parallel circuit and the energy transfer resistor in parallel to obtain a second parallel circuit; The second parallel circuit is connected in series with the superconducting magnet load to obtain a commutation switch circuit.

4. A control method for a magnetic commutation switch according to claim 1, characterized in that: The calculating the difference between the actual current value and the preset current value to obtain the working state of the magnetic converter includes: Calculating the difference between the actual current value and the preset current value; When the difference is not greater than zero, it is considered that the working state of the magnetic converter is steady state; When the difference is greater than zero, it is considered that the working state of the magnetic converter is demagnetization.

5. A control method for a magnetic commutation switch according to claim 1, characterized in that: When the working state is a steady state, adaptively adjusting the MOSFET to maintain the actual current value includes: When the working state is steady state, the gate-source voltage of the MOSFET is adaptively adjusted to a preset voltage value to maintain the actual current value; at the preset voltage value, the current of the commutation switch circuit mainly passes through the MOSFETs but not the energy transfer resistor.

6. A control system for a magnetic commutation switch, characterized in that: include: A circuit building module, used for connecting several MOSFETs and energy transfer resistors in parallel to obtain a commutation switch circuit of a magnetic converter; A current acquisition module, used for acquiring the actual current value of the magnetic current converter; A difference calculation module, used to calculate the difference between the actual current value and the preset current value, and obtain the working state of the magnetic converter; the working state includes steady state and demagnetization; A steady-state control module, used for adaptively adjusting the MOSFET to maintain the actual current value when the working state is a steady state; A demagnetization control module, used for slowly turning off the MOSFET when the working state is demagnetization, until the actual current value is no greater than the preset current value; The demagnetization control module is specifically used for: When the working state is demagnetization, the gate-source voltage of each MOSFET is reduced to 0 according to a preset step size to ensure that the actual current value is not greater than the preset current value; or, When the working state is demagnetization, reducing the gate-source voltage of each MOSFET according to a preset step size; If the actual current value is not greater than the preset current value before the gate-source voltage drops to the gate-source threshold voltage, the gate-source voltage is automatically adjusted to commutate the current to the MOSFET to maintain the preset current value; If the actual current value is still greater than the preset current value after the gate-source voltage drops to the gate-source threshold voltage, the MOSFET is turned off to transfer the current to the energy transfer resistor.

7. A control device for a magnetic commutation switch, characterized in that: The method comprises a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the control method of the magnetic commutation switch as claimed in any one of claims 1 to 5 when executing the computer program.

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