Control method of superconducting magnet system based on adjustable frequency GM refrigerator

Abstract

The invention discloses a control method of a superconducting magnet system based on an adjustable frequency GM refrigerator, wherein the superconducting magnet system comprises a refrigeration component, a superconducting magnet component, a monitoring component and a controller; the refrigeration component comprises a compressor and a refrigerator, the compressor is connected with the refrigerator in cooperation, the superconducting magnet component comprises a superconducting coil and a cold screen, the superconducting coil is arranged in the cold screen; the refrigerator comprises a primary cold head and a secondary cold head, the primary cold head is thermally connected with the cold screen, and the secondary cold head is thermally connected with the superconducting coil; the monitoring component comprises a plurality of temperature sensors, and the plurality of temperature sensors are arranged on the superconducting magnet component; the controller is connected with the refrigeration component in cooperation, and the controller is connected with the plurality of temperature sensors in cooperation. The superconducting magnet system can adjust the working frequency of the GM refrigerator through the controller according to different working operation modes, thereby reducing the risk of quenching of the superconducting magnet system, improving the working efficiency of the superconducting magnet system, and reducing energy consumption at the same time, so as to achieve the purpose of energy saving.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of refrigerators, and in particular to a control method for a superconducting magnet system based on an adjustable frequency GM refrigerator. Background Art

[0002] GM refrigerator is a device based on Simon expansion principle to obtain ultra-low temperature, which is widely used in medical MRI and semiconductor fields. GM refrigerator drives the piston to reciprocate along the inner wall of the cylinder through the driving device, compressing and expanding the helium to achieve cooling and refrigeration.

[0003] Superconducting magnets are used in nuclear magnetic resonance imaging equipment and need to work in ultra-low temperature and vacuum environments. High-temperature superconducting tapes are used as high-temperature current leads to meet the equipment operation requirements. The working temperature of superconducting magnets is 4.2K or below, and the working temperature of high-temperature superconducting tapes under excitation or demagnetization is 65K or below. The working temperature of superconducting magnets and high-temperature superconducting tapes is controlled by GM refrigerators.

[0004] At present, superconducting magnet systems with GM refrigerators generally use superconducting magnet systems with less or no liquid nitrogen due to the shortage of liquid nitrogen resources. However, the cooling time of such superconducting magnet systems is long, which affects the working efficiency of the superconducting magnet systems. In addition, the superconducting magnet systems are prone to quenching, which affects the operation of the superconducting magnet systems. Under normal operation, the operating temperature is too low, resulting in partial waste of cooling capacity, causing high energy consumption of the system. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art. The present invention provides a superconducting magnet system based on an adjustable frequency GM refrigerator and a control method. The superconducting magnet system is provided with a controller. According to different working modes of the superconducting magnet system, the working frequency of the GM refrigerator is adjusted by the controller, thereby reducing the risk of quenching of the superconducting magnet system, improving the working efficiency of the superconducting magnet system, and reducing energy consumption, thereby achieving the purpose of energy saving.

[0006] The present invention provides a superconducting magnet system based on an adjustable frequency GM refrigerator, the superconducting magnet system comprising a refrigeration component, a superconducting magnet component, a monitoring component and a controller;

[0007] The refrigeration assembly includes a compressor and a refrigerator, the compressor is cooperatively connected with the refrigerator, the superconducting magnet assembly includes a superconducting coil and a cold shield, the superconducting coil is arranged in the cold shield;

[0008] The refrigerator comprises a primary cold head and a secondary cold head, wherein the primary cold head is thermally connected to the cold shield, and the secondary cold head is thermally connected to the superconducting coil;

[0009] The monitoring assembly includes a plurality of temperature sensors, and the plurality of temperature sensors are arranged on the superconducting magnet assembly;

[0010] The controller is cooperatively connected with the refrigeration component, and the controller is cooperatively connected with the plurality of temperature sensors.

[0011] Furthermore, the superconducting magnet assembly further comprises a vacuum cylinder, and the superconducting coil and the cold shield are arranged in the vacuum cylinder;

[0012] Furthermore, the plurality of temperature sensors include a first temperature sensor, and the first temperature sensor is disposed on the superconducting coil.

[0013] Furthermore, the plurality of temperature sensors include a second temperature sensor, and the second temperature sensor is arranged on the cold screen.

[0014] Furthermore, a high-temperature current lead is provided on the superconducting coil;

[0015] The plurality of temperature sensors further include a third sensor disposed on the high-temperature current lead.

[0016] The present invention also provides a control method, which is applicable to the superconducting magnet system, and comprises:

[0017] According to the working state of the superconducting magnet system, the working modes of the superconducting magnet system are divided into a cooling operation mode, an excitation and demagnetization operation mode, an energy-saving operation mode and a normal fixed-frequency operation mode;

[0018] Setting relevant parameters of the operation of the superconducting magnet system on the controller;

[0019] The controller adjusts the frequency of the compressor and the refrigerator according to the actual operation mode.

[0020] Furthermore, the relevant parameters of the superconducting magnet system operation are set on the controller, including:

[0021] According to the material of the superconducting coil, the maximum operating temperature of the superconducting coil is set to Tcmax, the normal operating temperature of the superconducting coil is set to Tc, the high-temperature current lead temperature in the excitation and demagnetization operation modes is set to Thtst, and the operating temperature of the high-temperature current lead is set to Thst; the set temperature of the superconducting coil operation in the energy-saving mode is set to Tcmax1;

[0022] Set the maximum frequency of the compressor to f1max, the normal operating frequency to f1n, and the excitation or demagnetization operating frequency to f1ramp;

[0023] Set the maximum frequency of the refrigerator to f2max, the normal operating frequency to f2n, and the excitation or demagnetization operating frequency to f2ramp.

[0024] Furthermore, the controller adjusts the frequency of the compressor and the refrigerator according to the actual operation mode, including:

[0025] In the cooling operation mode, the frequency of the compressor is adjusted to f1max and the frequency of the refrigerator is adjusted to f2max by the controller;

[0026] When it is monitored that the temperature of the superconducting coil reaches Tc, the frequency of the compressor is adjusted to f1n, and the frequency of the refrigerator is adjusted to f2n, and the normal fixed-frequency operation mode is entered.

[0027] Furthermore, the controller adjusts the frequency of the compressor and the refrigerator according to the actual operation mode, including:

[0028] In the excitation or demagnetization operation mode, when the monitored temperature is higher than Thtst, the controller adjusts the compressor frequency to f1ramp and the refrigerator frequency to f2ramp.

[0029] Furthermore, the controller adjusts the frequency of the compressor and the refrigerator according to the actual operation mode, including:

[0030] In the energy-saving operation mode, the actual temperature of the superconducting coil, the maximum operating temperature Tcmax and the set temperature Tcmax1 are compared. If the actual temperature is lower than the maximum operating temperature Tcmax, the compressor frequency is lowered. If the actual temperature is higher than the set temperature Tcmax1, the compressor frequency is increased. The compressor frequency is repeatedly adjusted to maintain stability.

[0031] The present invention provides a superconducting magnet system based on an adjustable frequency GM refrigerator and a control method. The superconducting magnet system is provided with a controller. According to different working operation modes of the superconducting magnet system, the working frequency of the GM refrigerator is adjusted by the controller, thereby reducing the quench risk of the superconducting magnet system, improving the working efficiency of the superconducting magnet system, and reducing energy consumption, thereby achieving the purpose of energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 Schematic diagram of the structure of a superconducting magnet system based on an adjustable frequency GM refrigerator in an embodiment of the present invention;

[0034] Figure 2 is a flow chart of a superconducting magnet system control method based on an adjustable frequency GM refrigerator in an embodiment of the present invention;

[0035] Figure 3 Schematic diagram of temperature adjustment of a superconducting magnet system in a cooling operation mode according to an embodiment of the present invention;

[0036] Figure 4 It is a schematic diagram of temperature adjustment of a superconducting magnet system in an excitation or demagnetization operation mode in an embodiment of the present invention;

[0037] Figure 5 It is a schematic diagram of temperature adjustment of a superconducting magnet system in an energy-saving operation mode in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] 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.

[0039] Figure 1 A schematic diagram of the structure of a superconducting magnet system based on an adjustable frequency GM refrigerator in an embodiment of the present invention is shown. The superconducting magnet system includes a refrigeration component 1, a controller 2, a superconducting magnet component 3 and a monitoring component 4. The refrigeration component 1 includes a compressor 11 and a refrigerator 12. The compressor 11 is connected to the refrigerator 12, and the refrigerator 12 is connected to the superconducting magnet component 3 to provide the working temperature of the superconducting magnet component 3.

[0040] Specifically, the superconducting magnet assembly 3 includes a superconducting coil 31, a cold shield 32 and a vacuum cylinder 33. The superconducting coil 31 is arranged on the cold shield 32. The superconducting coil 31 and the cold shield 32 are arranged in the vacuum cylinder 33. The vacuum cylinder 33 provides a vacuum working environment for the superconducting coil 31.

[0041] The refrigerator 12 includes a primary cold head 121 and a secondary cold head 122 . The primary cold head 121 is thermally connected to the cold shield 32 to adjust the temperature of the cold shield 32 . The secondary cold head 122 is thermally connected to the superconducting coil 31 to adjust the temperature of the superconducting coil 31 .

[0042] Furthermore, a high-temperature current lead 34 is provided on the superconducting magnet assembly 3 , and the high-temperature current lead 34 connects the superconducting magnet assembly 3 and the operating equipment.

[0043] Specifically, the monitoring component 4 includes a first temperature sensor 41, a second temperature sensor 42 and a third temperature sensor 43. The first temperature sensor 41 is arranged on the superconducting coil 31, and the first temperature sensor 41 is used to monitor the temperature of the superconducting coil 31. The second temperature sensor 42 is arranged on the cold shield 32, and the second temperature sensor 42 is used to monitor the temperature of the cold shield 32. The third temperature sensor 43 is arranged on the high-temperature current lead 34, and the third temperature sensor 43 is used to monitor the temperature of the high-temperature current lead 34, so as to obtain the operating status of the operating equipment.

[0044] Specifically, the controller 2 is connected to the refrigeration assembly 1, and the controller 2 can control the working state of the refrigeration assembly 1. The compressor 11 is a nitrogen compressor, and the working frequency of the compressor 11 can be regulated by the controller 2, and the working frequency of the refrigerator 12 can be regulated by the controller 2.

[0045] Furthermore, the controller 2 is connected with the refrigeration component 1 and the monitoring component 4 in a wireless manner.

[0046] Specifically, the controller 2 is correspondingly connected to the first temperature sensor 41, the second temperature sensor 42 and the third temperature sensor 43. The controller 2 can receive temperature monitoring data from the first temperature sensor 41, the second temperature sensor 42 and the third temperature sensor 43, so as to obtain the operating temperature of the superconducting coil 31.

[0047] Furthermore, the operator can obtain the actual operating temperature of the superconducting coil 31 from the controller 2 and make adjustments according to the operating requirements of the superconducting magnet system. For example, when the superconducting coil 31 needs to cool down, the compressor 11 and the refrigerator 12 are regulated by the controller 2, and the frequencies of the compressor 11 and the refrigerator 12 are adjusted to the maximum frequency to improve the cooling efficiency of the superconducting coil 31. When the temperature of the superconducting coil 31 drops to the required temperature, the operating frequencies of the compressor 11 and the refrigerator 12 are adjusted to the normal operating frequency by the controller 2.

[0048] The embodiment of the present invention provides a superconducting magnet system based on an adjustable frequency GM refrigerator. The system is provided with a controller 2 and a compressor 11 and a refrigerator 12 whose frequencies can be adjusted. The system performs real-time temperature monitoring of a superconducting magnet assembly 3 through a monitoring component 4. The frequencies of the compressor 11 and the refrigerator 12 can be adjusted in real time through the controller 2 according to actual operating requirements, thereby adjusting the operating temperature of the superconducting magnet assembly 3, thereby reducing the risk of quenching of the superconducting magnet assembly 3, improving the operating efficiency of the superconducting magnet system, and reducing energy consumption.

[0049] Embodiment 2:

[0050] Figure 2 The flowchart of the control method of the superconducting magnet system based on the adjustable frequency GM refrigerator in the embodiment of the present invention is shown. The control method includes:

[0051] S11: According to the operating state of the superconducting magnet system, the operating modes of the superconducting magnet system are divided into a cooling operation mode, an excitation and demagnetization operation mode, an energy-saving operation mode and a normal fixed-frequency operation mode.

[0052] S12: Setting relevant parameters of the superconducting magnet system operation on the controller.

[0053] Specifically, according to the material of the superconducting coil, the maximum operating temperature of the superconducting coil 31 is set to Tcmax on the controller 2, the normal operating temperature value of the superconducting coil 31 is Tc, the operating temperature of the high-temperature current lead in the excitation and demagnetization operation modes is set to Thtst, and the operating temperature of the high-temperature current lead is set to Thts; the set temperature of the superconducting coil operation in the energy-saving mode is set to Tcmax1.

[0054] Furthermore, the maximum frequency of the compressor 11 is set as f1max on the controller 2, the normal operating frequency of the compressor 11 is f1n, and the operating frequency of the compressor 11 in the excitation or demagnetization operation mode is f1ramp;

[0055] Furthermore, the maximum frequency of the refrigerator 12 is set as f2max on the controller 2, the normal operating frequency of the refrigerator 12 is set as f2n, and the operating frequency of the refrigerator 12 in the excitation or demagnetization operation mode is set as f2ramp.

[0056] S13: adjusting the frequencies of the compressor and the refrigerator according to the actual operation mode through the controller.

[0057] Specifically, in the cooling operation mode, the frequency of the compressor is adjusted to f1max and the frequency of the refrigerator is adjusted to f2max through the controller.

[0058] Specifically, Figure 3 The temperature schematic diagram of the superconducting magnet system in the cooling operation mode in the embodiment of the present invention is shown. The temperature of the superconducting coil 31 is monitored by the first temperature sensor 41. When the actual temperature of the superconducting coil 31 is higher than the maximum operable temperature Tcmax of the superconducting coil 31, the superconducting magnet system needs to be cooled down. The mode is adjusted to the cooling operation mode by the controller 2, that is, the operating frequency of the compressor 11 is adjusted to the maximum operating frequency f1max, and the operating frequency of the refrigerator 12 is adjusted to the maximum operating frequency f2max. At this time, the air volume provided by the compressor 11 to the refrigerator 12 reaches the maximum, and the cooling capacity output of the first-level cold head 121 and the second-level cold head 122 also reaches the maximum, which can accelerate the cooling of the superconducting coil 31. When the temperature of the superconducting coil 31 returns to the normal operating temperature Tc, the operating frequency of the compressor 11 is adjusted to the operating frequency f1n in the normal fixed frequency mode, and the operating frequency of the refrigerator 12 is adjusted to the normal operating frequency f2n, and the normal fixed frequency operation mode is entered.

[0059] Specifically, Figure 4 The schematic diagram of temperature adjustment of the superconducting magnet system in the excitation or demagnetization operation mode in the embodiment of the present invention is shown. In the excitation or demagnetization operation mode, the temperature of the high-temperature current lead 34 is monitored by the third temperature sensor 43. When the monitored operation temperature Thts of the high-temperature current lead 34 is higher than the operation temperature Thtst of the high-temperature current lead 34 in the excitation and demagnetization operation mode, the operation frequency of the compressor 11 is adjusted to f1ramp and the operation frequency of the refrigerator 12 is adjusted to f2ramp through the controller 2. At this time, the amount of air provided by the compressor 11 to the refrigerator 12 increases, and the cooling capacity of the first-stage cold head 121 and the second-stage cold head 122 in the refrigerator 12 increases. When the excitation or demagnetization is completed, the operation frequency of the compressor 11 is adjusted to the normal operating frequency f1n and the operation frequency of the refrigerator 12 is adjusted to the normal operating frequency f2n through the controller 2, and the normal fixed frequency operation mode is entered.

[0060] Specifically, Figure 5A schematic diagram of temperature adjustment of a superconducting magnet system in an energy-saving operation mode in an embodiment of the present invention is shown. When the superconducting magnet system is in an idle state, or when the superconducting magnet system needs to save energy, the superconducting magnet system can be set to the energy-saving mode through the controller 2, and the actual temperature of the superconducting coil 31, the maximum operating temperature Tcmax and the set temperature Tcmax1 are compared. If the actual temperature is less than the maximum operating temperature Tcmax, the operating frequency of the compressor 11 is lowered. If the actual temperature is greater than the set temperature Tcmax1, the operating frequency of the compressor 11 is increased. The frequency of the compressor 11 is repeatedly adjusted to maintain a stable frequency.

[0061] Furthermore, the operating frequency of the compressor 11 is adjusted by the controller 2. After multiple iterations, the operating frequency of the compressor 11 will stabilize at a certain frequency, and the frequency is less than the normal operating frequency f1n of the compressor 11. The superconducting magnet system enters an energy-saving operation mode, reducing the operating energy consumption of the superconducting magnet system.

[0062] Furthermore, by adjusting the compressor 11 through the controller 2, adjusting the operating frequency of the compressor 11 to the normal operating frequency f1n, and adjusting the operating frequency of the refrigerator 12 to the normal operating frequency f2n, the superconducting magnet system can be pushed out of the energy-saving operation mode and enter the normal operation mode.

[0063] The embodiment of the present invention provides a superconducting magnet system control method based on an adjustable frequency GM refrigerator. The control method adjusts the operating frequencies of the compressor 11 and the refrigerator 12 through the controller 2 according to different operating modes of the superconducting magnet system. During the cooling process, the operating frequencies of the compressor 11 and the refrigerator 12 are accelerated, and the cooling speed of the superconducting coil 31 is accelerated. During the excitation or demagnetization process, the operating frequencies of the compressor 11 and the refrigerator 12 are accelerated, the temperature of the high-temperature current lead 34 is reduced, and the quench risk of the superconducting coil 31 is reduced. In the energy-saving mode, the frequency of the compressor 11 is reduced, thereby reducing the cooling capacity of the refrigerator 12, thereby achieving an energy-saving effect.

[0064] The embodiment of the present invention provides a superconducting magnet system and control method based on an adjustable frequency GM refrigerator. By setting a controller 2 and a monitoring component 4, the operating frequencies of the compressor 11 and the refrigerator 12 are regulated by the controller 2 according to the requirements of different operating modes of the superconducting magnet system, thereby reducing the risk of quenching of the superconducting magnet system, improving the working efficiency of the superconducting magnet system, reducing the energy consumption of the superconducting magnet system, and achieving the purpose of energy saving.

[0065] A person skilled in the art may understand that all or part of the steps in the various methods of the above embodiments may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, and the storage medium may include: a read-only memory (ROM), a random access memory (RAM), a disk or an optical disk, etc.

[0066] In addition, the superconducting magnet system and control method based on the adjustable frequency GM refrigerator provided in the embodiment of the present invention are introduced in detail above. The principle and implementation mode of the present invention are explained by using specific examples herein. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A control method for a superconducting magnet system based on an adjustable frequency GM refrigerator, characterized in that: The superconducting magnet system includes a refrigeration component, a superconducting magnet component, a monitoring component and a controller; The refrigeration assembly includes a compressor and a refrigerator, the compressor is connected with the refrigerator, the superconducting magnet assembly includes a superconducting coil, a vacuum cylinder and a cold shield, the superconducting coil is arranged in the cold shield, the cold shield is arranged in the vacuum cylinder, and a high-temperature current lead is arranged on the superconducting coil; The refrigerator comprises a primary cold head and a secondary cold head, wherein the primary cold head is thermally connected to the cold shield, and the secondary cold head is thermally connected to the superconducting coil; The monitoring assembly includes a plurality of temperature sensors, which are arranged on the superconducting magnet assembly, specifically including a first sensor arranged on the superconducting coil, a second sensor arranged on the cold shield, and a third sensor arranged on the high-temperature current lead; The controller is cooperatively connected with the refrigeration assembly, and the controller is cooperatively connected with the plurality of temperature sensors; The control method comprises: According to the working state of the superconducting magnet system, the working mode of the superconducting magnet system is divided; the working mode includes a cooling operation mode, an excitation and demagnetization operation mode, an energy-saving operation mode and a normal fixed-frequency operation mode; The relevant parameters of the superconducting magnet system operation are set on the controller, including: According to the material of the superconducting coil, the maximum operating temperature of the superconducting coil is set to Tcmax, and the normal operating temperature of the superconducting coil is set to Tc; Set the operating temperature of the high-temperature current lead in the excitation and demagnetization operation modes to Thts, and the maximum operating temperature to Thtst; Set the set temperature of the superconducting coil in energy-saving mode to Tcmax1; Set the maximum frequency of the compressor to f1max, the normal operating frequency to f1n, and the excitation or demagnetization operating frequency to f1ramp; Set the maximum frequency of the refrigerator to f2max, the normal operating frequency to f2n, and the excitation or demagnetization operating frequency to f2ramp; The controller adjusts the frequency of the compressor and the refrigerator in combination with the actual operation mode, including: When it is monitored that the actual temperature of the superconducting coil is higher than the maximum operable temperature Tcmax, the operation mode of the superconducting magnet system is adjusted to a cooling operation mode; The controller adjusts the frequency of the compressor to a maximum frequency f1max, and adjusts the frequency of the refrigerator to a maximum frequency f2max; When it is monitored that the temperature of the superconducting coil returns to the normal operating temperature Tc, the operating mode of the superconducting magnet system is adjusted to the normal fixed-frequency operating mode; The frequency of the compressor is adjusted to the normal operating frequency f1n, and the frequency of the refrigerator is adjusted to the normal operating frequency f2n, and the normal fixed frequency operation mode is entered; When excitation or demagnetization is required, the operation mode of the superconducting magnet system is adjusted to the excitation or demagnetization operation mode, the operation frequency of the compressor and the refrigerator is increased, and the temperature of the high-temperature current lead is monitored; The temperature of the high-temperature current lead is monitored by the third sensor. When the monitored operating temperature Thts of the high-temperature current lead is higher than the operating temperature Thtst of the high-temperature current lead in the excitation and demagnetization operating modes, the operating frequency of the compressor is adjusted to f1ramp and the operating frequency of the refrigerator is adjusted to f2ramp by the controller, so that the amount of gas provided by the compressor to the refrigerator is increased; When the excitation or demagnetization is completed, the controller adjusts the operating frequency of the compressor to the normal operating frequency f1n, and adjusts the operating frequency of the refrigerator to the normal operating frequency f2n, so that the superconducting magnet system enters the normal fixed frequency operation mode; The frequency adjustment of the compressor and the refrigerator by the controller in combination with the actual operation mode includes: In the energy-saving operation mode, the actual temperature of the superconducting coil, the maximum operating temperature Tcmax and the set temperature Tcmax1 are compared. If the actual temperature is lower than the maximum operating temperature Tcmax, the compressor frequency is lowered by the controller; If the actual temperature is greater than the set temperature Tcmax1, the compressor frequency is increased by the controller, and the frequency of the compressor is repeatedly adjusted to maintain stability.

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