JP6861922B1 - Refrigerator control method, refrigerator control program and refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerator control method, a refrigerator control program and a refrigerator capable of suppressing a sudden change in the rotation speed of a turbo compressor. SOLUTION: A transition command step to a second control mode for instructing a transition from a first control mode to a second control mode, and an SV21 of a set value (SV2) of a second temperature controller are displayed. The process of rewriting the set value of the second temperature controller, which rewrites the current value (PV2) of the second temperature controller to PV21, and the operation amount (MV2) of the second temperature controller are changed to the first temperature. The operation amount rewriting process of the second temperature controller, which rewrites the operation amount of the controller (MV1) to MV11, and the control of the rotation speed of the turbo type compressor are performed by the operation amount of the first temperature controller (MV1). ) Switch from dependence to operation amount (MV2) dependence of the second temperature controller, change the second control point switching step and the set value (SV2) of the second temperature controller from PV21 to SV21 over time. A method for controlling a refrigerator, comprising a step of changing a set value of a second temperature controller over time. [Selection diagram] None

Description

The present invention relates to a refrigerator control method, a refrigerator control program, and a refrigerator.

Refrigerators that utilize cryogenic refrigeration cycles that repeat adiabatic compression, isobaric cooling, adiabatic expansion, and isobaric heating are used to cool superelectric conductive equipment (cooling targets) such as power transmission cables, current limiters, and transformers. .. In cooling the superconducting power equipment, a circulating refrigerant (second refrigerant) such as liquid nitrogen, liquid hydrogen or liquid helium is circulated in the superconducting power equipment, and the temperature is raised by the heat generated by the superconducting power equipment and the invading heat in the system. The refrigerant (second refrigerant) is cooled to a predetermined temperature by the refrigerator. Refrigerators are suitable when large capacity refrigeration capacity is required. As the refrigerant gas of the refrigerator, a refrigerator refrigerant (first refrigerant) such as neon or helium is used.

A schematic configuration of an example of a refrigerator is shown in FIG. In the refrigerator 1, the main heat exchanger 101, the auxiliary heat exchanger 102, and the turbo type are on the first circulation path (refrigerant refrigerant circulation line) 111 in which the first refrigerant (refrigerant refrigerant) M1 circulates. A compressor 103, a cooler 110, an expansion turbine 104, and a first temperature controller 105 are arranged, and on a second circulation path (circulating refrigerant circulation line) 112 in which the second refrigerant (circulating refrigerant) M2 circulates. The auxiliary heat exchanger 102, the second temperature controller 106, the refrigerant circulation pump 108, and the cooling target 109 are arranged. In the auxiliary heat exchanger 102, heat exchange is performed between the first refrigerant M1 and the second refrigerant M2, and the second refrigerant M2 is cooled. The turbo compressor 103, the first temperature controller 105, and the second temperature controller 106 are the turbo compressor control line 103a, the first temperature controller control line 105a, and the second temperature controller, respectively. It is controlled by the control device 107 via the device control line 106a. The control device 107 includes an inverter 107a and a control panel 107b.

The control modes when the superconducting device is cooled by the refrigerator shown in FIG. 1 are broadly defined as the following first control mode (hereinafter, also referred to as “control mode 1”) and second control mode (hereinafter, “control mode”). 2 ”).
The control mode 1 is a mode in which the temperature of the refrigerator refrigerant M1 is controlled at a target temperature by using the first temperature controller 105. The control mode 2 is a mode in which the temperature of the circulating refrigerant M2 is controlled at the target temperature by using the second temperature controller 106. In the refrigerator 1, when the second refrigerant M2 is flowing through the second circulation path 112, it is necessary to stabilize the temperature of the circulating refrigerant M2, and the temperature of the circulating refrigerant M2 will be controlled in the control mode 1. Then, the responsiveness to the temperature fluctuation of the circulating refrigerant M2 deteriorates. Therefore, the control of the refrigerator 1 cannot follow the heat load on the circulating refrigerant M2 side, and there is a possibility that the temperature required for cooling the superconducting power device (cooling target 109) cannot be maintained. Therefore, it is necessary to select the control mode 1 or the control mode 2 for the control of the refrigerator 1 depending on the situation of the circulating refrigerant M2. At this time, it is important in the operation of the refrigerator 1 to smoothly shift from the control mode 1 to the control mode 2 or from the control mode 2 to the control mode 1.
As a method of controlling the refrigerating capacity in each control mode, the temperature of the refrigerant (refrigerant refrigerant M1 and circulating refrigerant M2) is monitored by a temperature controller (first temperature controller 105, second temperature controller 106). A method is used in which the rotation speed of the turbo-type compressor 103 is calculated so that the temperature maintains the set value (hereinafter, also referred to as “SV”), and the operation amount (hereinafter, also referred to as “MV”) is output. For example, when the current value (hereinafter, also referred to as “PV”) is higher than that of the SV, it is necessary to promote cooling, so that the rotation speed of the turbo compressor 103 is increased to increase the refrigerating capacity. In this way, by increasing or decreasing the rotation speed of the turbo compressor 103, control is performed so that the SV and the PV match.
When shifting from the control mode 1 to the control mode 2, in order to avoid duplication of control, the temperature controller is changed from the first temperature controller 105 on the refrigerator refrigerant M1 side to the second temperature controller on the circulating refrigerant M2 side. It is necessary to switch to the vessel 106. However, since the PV and SV in the first temperature controller 105 and the PV and SV in the second temperature controller 106 differ depending on the operating conditions, the PV and SV in the first temperature controller 105 and the second temperature controller 106 There is also a difference in MV. When the control mode is shifted while the MV divergence between the first temperature controller 105 and the second temperature controller 106 is large, the turbo compressor is loaded due to a sudden change in the rotation speed of the turbo compressor 103. It takes.
The turbo compressor 103 is one of the important devices in the refrigerator 1, and if the turbo compressor 103 fails, it is necessary to open the refrigerator refrigerant M1 system and disassemble and repair the turbo compressor 103. Therefore, a great deal of time and money will be required for restoration. Therefore, in order to realize long-term operation of the refrigerator 1, stable operation of the turbo type compressor 103 is important.
Further, if the rotation speed of the turbo compressor 103 suddenly changes, undershoot and overshoot from the SV may occur. In that case, it takes time for the SV and PV to match. Further, when the load fluctuation of the circulating refrigerant M2 is large, hunting may occur and control may not be possible. Further, the undershoot may cause the circulating refrigerant M2 to become too low in temperature and solidify. When blockage occurs due to solidification of the circulating refrigerant M2 in the auxiliary heat exchanger 102 that exchanges heat between the refrigerating refrigerant M1 and the circulating refrigerant M2, the amount of exchanged heat decreases as the heat transfer area decreases, and the circulating refrigerant M2 is cooled. Can be difficult. If the circulating refrigerant M2 cannot be cooled, it is necessary to switch to backup equipment. If the backup cannot keep up, the power supply will be stopped due to the stoppage of the superconducting power device (cooling target 109).

In Patent Document 1, in a refrigerator using a cryogenic refrigeration cycle using a multi-stage compressor, when the heat load to be cooled fluctuates, the refrigerating capacity is controlled by controlling the rotation speed of the compressor or the expander. Is adjusted according to the heat load, but when the refrigerating capacity is controlled by the rotation speed control, other control parameters such as the flow rate, pressure ratio and temperature of the refrigerant are changed as the rotation speed changes. However, it may take some time for the refrigerating capacity to converge to a predetermined target value corresponding to the heat load, and it is difficult to obtain good responsiveness. ing.
In response to such a problem, Patent Document 1 describes that in a refrigerator using an ultra-low temperature refrigeration cycle using a multi-stage compressor, when a fluctuation in heat load is detected in a cooling target, the temperature is extremely low. We are proposing a cryogenic refrigeration cycle refrigerator that has good responsiveness to changes in the heat load of the object to be cooled, which is characterized by changing the flow rate of the refrigerant flowing through the refrigeration cycle. ..

International Publication No. 2014/192382

As shown in Patent Document 1, it is generally known to properly use the control mode 1 and the control mode 2. However, no control method for mode transition is shown.
Further, in Patent Document 1, a method is used in which a valve connecting the refrigerator refrigerant circulation path and the buffer tank is opened and closed by the output of the MV, and the pressure of the refrigerator refrigerant is changed to adjust the refrigerating capacity. In this method, since the rotation speed of the compressor is constant, the compressor can always be operated in a region where the efficiency of the compressor is high, and there is an advantage that the refrigerator can be operated with high efficiency. However, compared with the adjustment of the refrigerating capacity by the number of revolutions, the responsiveness of the refrigerating capacity is poor in the adjustment of the internal pressure, and there is a possibility that it cannot be followed when the load fluctuation of the circulating refrigerant is large. Further, a buffer tank, a valve, etc. for adjusting the pressure are required, and there is a concern that the device may become large in size.
Further, in a refrigerator using a reciprocating compressor, the refrigerating capacity is adjusted by increasing or decreasing the number of operating piston cylinders instead of controlling the rotation speed. However, since the freezing capacity of each refrigerator using a reciprocating compressor is small, it is necessary to arrange a plurality of refrigerators for large-capacity freezing. As the number of units increases, there is concern that the frequency of maintenance will increase. Therefore, when a large-capacity refrigerating capacity such as a superconducting power device is required, a refrigerating machine using a turbo compressor is suitable from the viewpoint of installation area, cost, and maintainability.

An object of the present invention is to provide a refrigerator control method, a refrigerator control program, and a refrigerator that can suppress a sudden change in the rotation speed of a turbo compressor and enable stable operation. ..

[1] The first circulation path in which the first refrigerant circulates, the second circulation path in which the second refrigerant circulates, and the first circulation path are arranged to adiabatically compress the first refrigerant. In the turbo type compressor, the cooler arranged in the first circulation path and isostatically cooling the first refrigerant after adiabatic compression by the turbo type compressor, and the first circulation path. A main heat exchanger that is arranged and exchanges heat between the first refrigerant before adiabatic compression by the turbo compressor and the first refrigerant after isobaric cooling by the cooler. An expansion turbine arranged in the first circulation path and adiabatically expanding the first refrigerant, and the first circulation path and the second circulation path arranged in the first circulation path and the second circulation path. An auxiliary heat exchanger that exchanges heat with the refrigerant, a first temperature controller arranged on the inlet side of the expansion turbine in the first circulation path, and the auxiliary heat exchanger in the second circulation path. A second temperature controller arranged on the outlet side of the above, a turbo compressor, a control device for controlling the first temperature controller and the second temperature controller, and the first It is a control method of a refrigerator in which the control device controls the rotation speed of the turbo compressor depending on the operation amount of the temperature controller (MV1) or the operation amount of the second temperature controller (MV2). hand,
The refrigerator used at an extremely low temperature has a first temperature controller that controls the temperature of the first refrigerant at a target temperature by adjusting the rotation speed of the turbo compressor. Control mode and a second control mode for controlling the temperature of the second refrigerant at a target temperature by adjusting the rotation speed of the turbo compressor using the second temperature controller. ,
A transition command process to the second control mode, which instructs the transition from the first control mode to the second control mode, and
The setting value rewriting process of the second temperature controller, which rewrites the SV21 of the set value (SV2) of the second temperature controller to the PV21 of the current value (PV2) of the second temperature controller,
The operation amount rewriting process of the second temperature controller, which rewrites the operation amount (MV2) of the second temperature controller to MV11 of the operation amount (MV1) of the first temperature controller,
A second control point switching process that switches the control of the rotation speed of the turbo compressor from the operation amount (MV1) dependence of the first temperature controller to the operation amount (MV2) dependence of the second temperature controller.
A method for controlling a refrigerator, comprising a step of changing the set value (SV2) of the second temperature controller with time from PV21 to SV21 with time.
[2] Furthermore
After the transition command step to the second control mode, before the set value rewriting step of the second temperature controller, or after the set value rewriting step of the second temperature controller, the second. Before the operation amount rewriting process of the temperature controller of 2, the operation amount of the first temperature controller (MV1) is fixed to MV11, and the operation amount of the first temperature controller is fixed.
After the second control point switching step, the operation amount fixing release step of the first temperature controller is provided, which releases the fixation of the operation amount (MV1) of the first temperature controller.
The method for controlling a refrigerator according to [1].
[3] The first circulation path in which the first refrigerant circulates, the second circulation path in which the second refrigerant circulates, and the first circulation path are arranged to adiabatically compress the first refrigerant. In the turbo type compressor, the cooler arranged in the first circulation path and isostatically cooling the first refrigerant after adiabatic compression by the turbo type compressor, and the first circulation path. A main heat exchanger that is arranged and exchanges heat between the first refrigerant before adiabatic compression by the turbo compressor and the first refrigerant after isobaric cooling by the cooler. An expansion turbine arranged in the first circulation path and adiabatically expanding the first refrigerant, and the first circulation path and the second circulation path arranged in the first circulation path and the second circulation path. An auxiliary heat exchanger that exchanges heat with the refrigerant, a first temperature controller arranged on the inlet side of the expansion turbine in the first circulation path, and the auxiliary heat exchanger in the second circulation path. A second temperature controller arranged on the outlet side of the above, a turbo compressor, a control device for controlling the first temperature controller and the second temperature controller, and the first It is a control method of a refrigerator in which the control device controls the rotation speed of the turbo compressor depending on the operation amount of the temperature controller (MV1) or the operation amount of the second temperature controller (MV2). hand,
The refrigerator used at an extremely low temperature has a first temperature controller that controls the temperature of the first refrigerant at a target temperature by adjusting the rotation speed of the turbo compressor. Control mode and a second control mode for controlling the temperature of the second refrigerant at a target temperature by adjusting the rotation speed of the turbo compressor using the second temperature controller. ,
A transition command process to the first control mode, which instructs the transition from the second control mode to the first control mode, and
The setting value rewriting process of the first temperature controller, which rewrites the SV11 of the set value (SV1) of the first temperature controller to the PV11 of the current value (PV1) of the first temperature controller,
The operation amount rewriting process of the first temperature controller, which rewrites the operation amount (MV1) of the first temperature controller to MV21 of the operation amount (MV2) of the second temperature controller,
The first control point switching process, which switches the control of the rotation speed of the turbo compressor from the operation amount (MV2) dependence of the second temperature controller to the operation amount (MV1) dependence of the first temperature controller,
A method for controlling a refrigerator, comprising a step of changing the set value (SV1) of the first temperature controller over time from PV11 to SV11, and a step of changing the set value of the first temperature controller over time.
[4] Furthermore
After the set value rewriting step S22 of the first temperature controller, before the operation amount rewriting step S24 of the first temperature controller, or after the transition command step S21 to the first control mode. Before the set value rewriting step S22 of the first temperature controller, the operation amount fixing step of the second temperature controller is provided, in which the operation amount (MV2) of the second temperature controller is fixed to the MV21. ,
After the first control point switching step, the operation amount fixing release step of the second temperature controller is provided, which releases the fixation of the operation amount (MV2) of the second temperature controller.
The method for controlling a refrigerator according to [3].
[5] A refrigerator control program, characterized in that a computer executes the refrigerator control method according to any one of [1] to [4].
[6] A refrigerator comprising a control device equipped with the control program for the refrigerator according to [5].

According to the present invention, it is possible to provide a refrigerator control method, a refrigerator control program, and a refrigerator that can suppress a sudden change in the rotation speed of a turbo compressor and enable stable operation.

FIG. 1 is a schematic configuration diagram of an example of a refrigerator. FIG. 2 is a flow chart showing a transition sequence from the control mode 1 to the control mode 2. FIG. 3 is a flow chart showing a transition sequence from the control mode 2 to the control mode 1. FIG. 4 is a trend graph of PV and MV in the transition from the control mode 1 to the control mode 2.

[Refrigerator control method]
An embodiment of the refrigerator control method of the present invention will be described as appropriate with reference to the drawings.

<Composition of refrigerator>
The refrigerator 1 used at an extremely low temperature, the configuration outline of which is shown in FIG. 1, includes a first circulation path 111 in which the first refrigerant M1 circulates, and a main heat exchanger 101 arranged in the first circulation path 111. A secondary heat exchanger 102, a turbo compressor 103, an expansion turbine 104, a first temperature controller 105 and a cooler 110, a second circulation path 112 through which the second refrigerant M2 circulates, and a second circulation. A sub-heat exchanger 102, a second temperature controller 106, a refrigerant circulation pump 108, a cooling target 109, a turbo compressor 103, a first temperature controller 105, and a second temperature arranged in the path 112. A control device 107 for controlling the controller 106 is provided.

The turbo type compressor 103 adiabatically compresses the first refrigerant M1. The turbo type compressor 103 can be operated within the range of the design rotation speed by a command from the inverter 107a.
The cooler 110 cools the first refrigerant M1 after adiabatic compression by the turbo type compressor 103 at an isobaric pressure.
The main heat exchanger 101 exchanges heat between the first refrigerant M1 before being adiabatically compressed by the turbo compressor 103 and the first refrigerant M1 after being isobarically cooled by the cooler 110.
The expansion turbine 104 adiabatically expands the first refrigerant M1.
The sub-heat exchanger 102 exchanges heat between the first refrigerant M1 and the second refrigerant M2.

Although the first temperature controller 105 is arranged on the inlet side of the expansion turbine 104 of the first circulation path 111, that is, between the main heat exchanger 101 and the expansion turbine 104 in FIG. 1, the first temperature controller 105 is arranged. The temperature controller 105 may be installed between the expansion turbine 104 and the sub-heat exchanger 102 or between the sub-heat exchanger 102 and the main heat exchanger 101.
Although the second temperature controller 106 is arranged on the outlet side of the sub-heat exchanger 102 of the second circulation path 112 in FIG. 1, it may be arranged on the inlet side of the sub-heat exchanger 102. Since the temperature of the second refrigerant M2 introduced into the cooling target (superconducting device) 109 can be easily controlled, the second temperature controller 106 is preferably arranged on the outlet side of the auxiliary heat exchanger 102.

The control device 107 includes an inverter 107a and a control panel 107b for controlling the inverter 107a. The inverter 107a, the turbo compressor 103, the first temperature controller 105, and the second temperature controller 106 are the turbo compressor control line 103a, the first temperature controller control line 105a, and the second temperature controller 106, respectively. It is connected to the second temperature controller control line 106a.

The refrigerator 1 has a first control mode and a first control mode in which the temperature of the first refrigerant M1 is controlled at a target temperature by adjusting the rotation speed of the turbo compressor 103 using the first temperature controller 105. It has a second control mode in which the temperature of the second refrigerant M2 is controlled at a target temperature by adjusting the rotation speed of the turbo compressor 103 using the temperature controller 106 of 2.
In the control mode 1, the first temperature controller 105 monitors the temperature of the first refrigerant M1 and controls the rotation speed of the turbo compressor 103. A temperature sensor (not shown) for measuring the temperature of the first refrigerant M1 is provided in the refrigerant pipe of the first circulation path 111, and the current value PV1 of the temperature of the first refrigerant M1 is determined by an electric signal. It is input as the current value PV11 to the temperature controller 105 of 1. The set value SV1 of the temperature of the first refrigerant M1 is set to an arbitrary value SV11 by operating the main body of the first temperature controller 105. Based on the deviation between PV11 and SV11, the operation amount MV1 is output from the first temperature controller 105 to the inverter 107a, and the rotation speed of the turbo compressor 103 is set.
In the control mode 2, the second temperature controller 106 monitors the temperature of the second refrigerant M2 and controls the rotation speed of the turbo compressor 103. A temperature sensor (not shown) for measuring the temperature of the second refrigerant M2 is provided in the refrigerant pipe of the second circulation path 112, and the current value PV2 of the temperature of the second refrigerant M2 is determined by an electric signal. It is input as the current value PV21 to the temperature controller 106 of 2. The set value SV2 of the temperature of the second refrigerant M2 is set to an arbitrary value SV21 by operating the main body of the second temperature controller 106. Based on the deviation between PV21 and SV21, the operation amount MV2 is output from the second temperature controller 106 to the inverter 107a, and the rotation speed of the turbo compressor 103 is set.

The first refrigerant M1 is, for example, neon, hydrogen or helium. As the first refrigerant M1, neon is preferable because it has a low freezing point and can realize the design pressure ratio of a turbo compressor at a low rotation speed.
The second refrigerant M2 is, for example, liquid nitrogen, liquid hydrogen or liquid helium. As the second refrigerant M2, liquid nitrogen is usually preferable because it can exhibit necessary and sufficient cooling performance and is inexpensive.

Hereinafter, the transition sequence from the control mode 1 to the control mode 2 and the transition sequence from the control mode 2 to the control mode 1 in the control method of the refrigerator of the present invention will be described in detail.

<Transition sequence from control mode 1 to control mode 2>
As shown in FIG. 2, the transition sequence from the control mode 1 to the control mode 2 includes the transition command step S11 to the second control mode, the set value rewriting step S12 of the second temperature controller, and the first. The operation amount fixing step S13 of the temperature controller, the operation amount rewriting step S14 of the second temperature controller, the second control point switching step S15, and the operation amount fixing release step S16 of the first temperature controller. , The set value time-dependent change step S17 of the second temperature controller is included. Normally, the transition sequence from the control mode 1 to the control mode 2 is an operation by an electric signal, and therefore can be executed in less than 1 second. Since the change in the operation amount MV1 in the transition sequence from the control mode 1 to the control mode 2 is extremely small, it is possible to omit fixing and releasing the operation amount, and it is possible to omit the operation amount fixing step of the first temperature controller. The operation amount fixing release step S16 of S13 and the first temperature controller can be omitted.

(S11: Transition command step to the second control mode)
The transition command step S11 to the second control mode is a step of instructing the transition from the first control mode to the second control mode.
The refrigerator 1 is in the control mode 1. The sequence of mode transition from control mode 1 to control mode 2 is activated.

(S12: Setting value rewriting process of the second temperature controller)
The setting value rewriting step S12 of the second temperature controller rewrites the SV21 of the set value (SV2) of the second temperature controller 106 to the PV21 of the current value (PV2) of the second temperature controller 106. It is a process.
After rewriting the SV21 to the PV21, the current value (PV2) of the second temperature controller 106 and the set value (SV2) of the second temperature controller 106 are always linked so as to be the same. As a result, the operating amount (MV2) of the second temperature controller 106 can be kept constant.

(S13: Step of fixing the operation amount of the first temperature controller)
The operation amount fixing step S13 of the first temperature controller is a step of fixing the operation amount (MV1) of the first temperature controller 105 to the MV11.
As a method of fixing the operation amount (MV1) of the first temperature controller 105, for example, there is a method of switching the first temperature controller 105 to the manual mode. Further, when the PID (Proportional-Integral-Differential) control is used to calculate the operation amount (MV1) of the first temperature controller 105, the PID parameter is temporarily changed to change the PID parameter of the first temperature controller 105. The rate of change of the manipulated variable (MV1) may be extremely slow.
At the same time, the operating amount (MV2) of the second temperature controller 106 may be fixed.
The operation amount fixing step S13 of the first temperature controller may be performed after the set value rewriting step S12 of the second temperature controller and before the operation amount rewriting step S14 of the second temperature controller. Then, it may be performed before the set value rewriting step S12 of the second temperature controller and after the transition command step S11 to the second control mode.

(S14: Operation amount rewriting process of the second temperature controller)
The operation amount rewriting step S14 of the second temperature controller is a step of rewriting the operation amount (MV2) of the second temperature controller 106 to MV11 of the operation amount (MV1) of the first temperature controller 105. is there.
In this step, since the current value (PV2) of the second temperature controller 106 and the set value (SV2) of the second temperature controller 106 are the same, the operating amount of the second temperature controller 106 (MV2). ) Does not change.

(S15: Second control point switching process)
In the second control point switching step S15, the control of the rotation speed of the turbo compressor 103 depends on the operation amount (MV1) of the first temperature controller 105 to the operation amount (MV2) of the second temperature controller 106. This is the process of switching to.

(S16: Operation amount fixing release step of the first temperature controller)
The operation amount fixing release step S16 of the first temperature controller is a step of releasing the operation amount (MV1) of the first temperature controller 105.
When the operation amount (MV2) of the second temperature controller 106 is fixed, the fixation of the operation amount (MV2) of the second temperature controller 106 is also released at the same time. If the temperature controller was in manual mode, return it to automatic mode. If the PID control parameter is changed to slow down the change in MV, the parameter is restored.

(S17: Process of changing the set value of the second temperature controller with time)
The set value time-dependent change step S17 of the second temperature controller is a step of changing the set value (SV2) of the second temperature controller 106 with time from PV21 to SV21.
Since the set value (SV2) of the second temperature controller 106 is different from the originally set value (SV2 in the transition command step to the second control mode), it is returned to the original value. However, when the value is suddenly returned to the originally set value, if the difference is large, a sudden change in the operation amount (MV2) of the second temperature controller 106 occurs. Therefore, it is preferable to change the set value (SV2) of the second temperature controller 106 little by little and gradually bring it closer to the originally set value. Specifically, for example, a method of increasing or decreasing the set value (SV2) of the second temperature controller 106 at a change rate of 0.1 K / s can be mentioned. Further, by controlling the output of the inverter 107a, the upper and lower limits may be set in stages for the rotation speed of the turbo compressor 103, and the rotation speed of the turbo compressor 103 may be changed in a plurality of times.

By executing the above steps S11 to S17, a sudden change in the number of revolutions of the turbo compressor 103 can be suppressed, and a stable mode transition from the control mode 1 to the control mode 2 can be executed.

<Transition sequence from control mode 2 to control mode 1>
As shown in FIG. 3, the transition sequence from the control mode 2 to the control mode 1 includes a transition command step S21 to the first control mode, a set value rewriting step S22 of the first temperature controller, and a second. The operation amount fixing step S23 of the temperature controller, the operation amount rewriting step S24 of the first temperature controller, the first control point switching step S25, and the operation amount fixing release step S26 of the second temperature controller. , The set value time-dependent change step S27 of the first temperature controller is included. Normally, the transition sequence from the control mode 2 to the control mode 1 is an operation by an electric signal, and therefore can be executed in less than 1 second. Since the change in the operation amount MV2 in the transition sequence from the control mode 2 to the control mode 1 is extremely small, it is possible to omit fixing and releasing the operation amount, and it is possible to omit the operation amount fixing step of the second temperature controller. The operation amount fixing release step S26 of S23 and the second temperature controller can be omitted.

(S21: Transition command step to the first control mode)
The transition command step S21 to the first control mode is a step of instructing the transition from the second control mode to the first control mode.
The refrigerator 1 is in the control mode 2. The sequence of mode transition from control mode 2 to control mode 1 is activated.

(S22: Setting value rewriting process of the first temperature controller)
The setting value rewriting step S22 of the first temperature controller rewrites the SV11 of the set value (SV1) of the first temperature controller 105 to the PV11 of the current value (PV1) of the first temperature controller 105. It is a process.
After rewriting SV11 to PV11, the current value (PV1) of the first temperature controller 105 and the set value (SV1) of the first temperature controller 105 are always linked so as to be the same. As a result, the operating amount (MV1) of the first temperature controller 105 can be kept constant.

(S23: Step of fixing the operation amount of the second temperature controller)
The operation amount fixing step S23 of the second temperature controller is a step of fixing the operation amount (MV2) of the second temperature controller 106 to the MV21.
As a method of fixing the operation amount (MV2) of the second temperature controller 106, for example, there is a method of switching the second temperature controller 106 to the manual mode. Further, when the PID (Proportional-Integral-Differential) control is used to calculate the operation amount (MV2) of the second temperature controller 106, the PID parameter is temporarily changed to change the PID parameter of the second temperature controller 106. The rate of change of the manipulated variable (MV2) may be extremely slow.
At the same time, the operating amount (MV1) of the first temperature controller 105 may be fixed.
The operation amount fixing step S23 of the second temperature controller may be performed after the set value rewriting step S22 of the first temperature controller and before the operation amount rewriting step S24 of the first temperature controller. Then, it may be performed before the set value rewriting step S22 of the first temperature controller and after the transition command step S21 to the first control mode.

(S24: Operation amount rewriting process of the first temperature controller)
The operation amount rewriting step S24 of the first temperature controller is a step of rewriting the operation amount (MV1) of the first temperature controller 105 to MV21 of the operation amount (MV2) of the second temperature controller 106. is there.
In this step, since the current value (PV1) of the first temperature controller 105 and the set value (SV1) of the first temperature controller 105 are the same, the operating amount of the first temperature controller 105 (MV1). ) Does not change.

(S25: First control point switching process)
In the first control point switching step S25, the control of the rotation speed of the turbo compressor 103 depends on the operation amount (MV1) of the first temperature controller 105 from the operation amount (MV2) of the second temperature controller 106. This is the process of switching to.

(S26: Operation amount fixing release step of the second temperature controller)
The operation amount fixing release step S26 of the second temperature controller is a step of releasing the operation amount (MV2) of the second temperature controller 106.
When the operation amount (MV1) of the first temperature controller 105 is fixed, the fixation of the operation amount (MV1) of the first temperature controller 105 is also released at the same time. If the temperature controller was in manual mode, return it to automatic mode. If the PID control parameter is changed to slow down the change in MV, the parameter is restored.

(S27: Process of changing the set value of the first temperature controller with time)
The time-dependent change step of the set value of the first temperature controller S27 is a step of changing the set value (SV1) of the first temperature controller 105 from PV11 to SV11 with time.
Since the set value (SV1) of the first temperature controller 105 is different from the originally set value (SV1 in the transition command step to the first control mode), it is returned to the original value. However, when the value is suddenly returned to the originally set value, if the difference is large, a sudden change in the operating amount (MV1) of the first temperature controller 105 occurs. Therefore, it is preferable to change the set value (SV1) of the first temperature controller 105 little by little and gradually bring it closer to the originally set value. Specifically, for example, a method of increasing or decreasing the set value (SV1) of the first temperature controller 105 at a change rate of 0.1 K / s can be mentioned. Further, by controlling the output of the inverter 107a, the upper and lower limits may be set in stages for the rotation speed of the turbo compressor 103, and the rotation speed of the turbo compressor 103 may be changed in a plurality of times.

By executing the above steps S21 to S27, a sudden change in the number of revolutions of the turbo compressor 103 can be suppressed, and a stable mode transition from the control mode 2 to the control mode 1 can be executed.

[Refrigerator control program]
The refrigerator control program of the present invention is characterized in that a computer executes the above-described refrigerator control method.

[refrigerator]
The refrigerator of the present invention is characterized by including a control device equipped with the above-mentioned control program of the refrigerator.
The schematic configuration of an example of the refrigerator of the present invention is as shown in FIG.

[Action effect]
In the conventional control method of the refrigerator, when shifting from the control mode 1 to the control mode 2, the temperature of the first refrigerant M1 is controlled from the first temperature controller 105 to the second refrigerant M2. The mode transition was performed by a method of simply shifting the temperature controller to the second temperature controller 106 that controls the temperature. In this method, since the control parameters of each temperature controller are not changed, the MV of each temperature controller is different, and when the control is switched from the first temperature controller 105 to the second temperature controller 106, the turbo type is used. The rotation speed of the compressor 103 of the above changes suddenly. When the rotation speed of the turbo compressor 103 fluctuates greatly temporarily, the temperature of the second refrigerant M2 also fluctuates, and it takes time to become stable again. Further, not only the load is applied to the turbo compressor 103, but also the pressure fluctuation of the first refrigerant M1 due to the fluctuation of the rotation speed and the like may cause the refrigerator 1 to stop interlocking.
On the other hand, in the control method of the refrigerator of the present invention, a control sequence is added to each of the first temperature controller 105 and the second temperature controller 106 at the time of transition from the control mode 1 to the control mode 2. As a result, a sudden change in the rotation speed of the turbo compressor 103 can be suppressed, and stable operation becomes possible.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the examples described later, and various modifications can be made as long as the gist of the present invention is not deviated.

[Example 1]
The transition from the control mode 1 to the control mode 2 is as follows: S11: Transition command process to the second control mode, S12: Setting value rewriting process of the second temperature controller, S13: Operation of the first temperature controller. Amount fixing process, S14: Operation amount rewriting process of the second temperature controller, S15: Second control point switching process, S16: Operation amount fixing release process of the first temperature controller, S17: Second temperature adjustment The mode transition was completed by performing the process of changing the set value of the vessel with time.
Table 1 shows the set value (SV), the current value (PV), and the manipulated variable (MV) of the temperature controller at the time of mode transition from the control mode 1 to the control mode 2 in this embodiment.

The current value (PV) of the temperature controller is constantly changing.
The italics in the SV and MV columns are the values that have been forcibly changed.
The MV with a circle in the MV column is the value used for the output.

FIG. 4 shows a trend graph of PV and MV of this embodiment in the transition from control mode 1 to control mode 2 (solid line).

[Example 2]
The transition from the control mode 1 to the control mode 2 is as follows: S11: Transition command process to the second control mode, S12: Setting value rewriting process of the second temperature controller, S14: Operation of the second temperature controller. The mode transition was completed in the order of quantity rewriting step, S15: second control point switching step, and S17: second temperature controller set value aging step.
Table 2 shows the set value (SV), the current value (PV), and the manipulated variable (MV) of the temperature controller at the time of mode transition from the control mode 1 to the control mode 2 in this embodiment.

The current value (PV) of the temperature controller is constantly changing.
The italics in the SV and MV columns are the values that have been forcibly changed.
The MV with a circle in the MV column is the value used for the output.

[Example 3]
The transition from the control mode 2 to the control mode 1 is as follows: S21: Transition command process to the first control mode, S22: Setting value rewriting process of the first temperature controller, S23: Operation of the second temperature controller. Amount fixing step, S24: operation amount rewriting step of the first temperature controller, S25: first control point switching step, S26: operation amount fixing release step of the second temperature controller, S27: first The mode transition was completed by performing the process of changing the set value of the temperature controller over time in this order.
Table 3 shows the set value (SV), the current value (PV), and the manipulated variable (MV) of the temperature controller at the time of mode transition from the control mode 2 to the control mode 1 in this embodiment.

The current value (PV) of the temperature controller is constantly changing.
The italics in the SV and MV columns are the values that have been forcibly changed.
The MV with a circle in the MV column is the value used for the output.

[Comparative Example 1]
The transition from the control mode 1 to the control mode 2 was performed in the order of S11: transition command step to the second control mode, and S15: second control point switching step, and the mode transition was completed.
Table 4 shows the set value (SV), the current value (PV), and the manipulated variable (MV) of the temperature controller at the time of mode transition from the control mode 1 to the control mode 2 in this comparative example.

The current value (PV) of the temperature controller is constantly changing.
The MV with a circle in the MV column is the value used for the output.

FIG. 4 shows a trend graph of PV and MV of this comparative example in the transition from the control mode 1 to the control mode 2 (broken line).

[Explanation of results]
In Examples 1 to 3, stable operation can be performed by suppressing a sudden change in the rotation speed of the turbo compressor. On the other hand, in Comparative Example 1, a sudden change in the rotation speed of the turbo compressor occurs, and stable operation cannot be performed.
Further, as shown in FIG. 4, in Example 1, PV2 does not reach the circulating refrigerant freezing point, whereas in Comparative Example 1, PV2 may reach the circulating refrigerant freezing point due to the large undershoot.

In the control method of the refrigerator of the present invention, there is no sudden change in the rotation speed of the turbo compressor at the time of transition from control mode 1 to control mode 2 and transition from control mode 2 to control mode 1, so that the refrigerator is refrigerated. Stable operation of the aircraft is possible.
The refrigerator control method of the present invention is suitable for operating a refrigerator for cooling superconducting equipment.

1 Refrigerant 101 Main heat exchanger 102 Secondary heat exchanger 103 Turbo compressor 103a Turbo compressor control line 104 Expansion turbine 105 First temperature controller 105a First temperature controller Control line 106 Second Temperature controller 106a Second temperature controller Control line 107 Control device 107a Inverter 107b Control panel 108 Refrigerant circulation pump 109 Cooling target 110 Cooler 111 First circulation path (refrigerant refrigerant circulation line)
112 Second circulation path (circulating refrigerant circulation line)
M1 first refrigerant (refrigerant refrigerant)
M2 Second refrigerant (circulating refrigerant)

Claims (6)

A turbo type that is arranged in the first circulation path through which the first refrigerant circulates, the second circulation path through which the second refrigerant circulates, and the first circulation path, and adiabatically compresses the first refrigerant. A compressor, a cooler arranged in the first circulation path and isostatically cooling the first refrigerant after adiabatic compression by the turbo compressor, and a cooler arranged in the first circulation path. A main heat exchanger that exchanges heat between the first refrigerant before adiabatic compression by the turbo compressor and the first refrigerant after isobaric cooling by the cooler, and the first heat exchanger. An expansion turbine arranged in the circulation path of the above and adiabatically expanding the first refrigerant, and the first circulation path and the second circulation path arranged in the first circulation path and the second circulation path. An auxiliary heat exchanger that exchanges heat, a first temperature controller arranged on the inlet side of the expansion turbine in the first circulation path, and an outlet side of the auxiliary heat exchanger in the second circulation path. The first temperature controller includes a second temperature controller arranged in the above, a turbo compressor, a first temperature controller, and a control device for controlling the second temperature controller. A method for controlling a refrigerator in which the control device controls the rotation speed of the turbo compressor depending on the operation amount (MV1) of the second temperature controller or the operation amount (MV2) of the second temperature controller.
The refrigerator used at an extremely low temperature has a first temperature controller that controls the temperature of the first refrigerant at a target temperature by adjusting the rotation speed of the turbo compressor. Control mode and a second control mode for controlling the temperature of the second refrigerant at a target temperature by adjusting the rotation speed of the turbo compressor using the second temperature controller. ,
A transition command process to the second control mode, which instructs the transition from the first control mode to the second control mode, and
The setting value rewriting process of the second temperature controller, which rewrites the SV21 of the set value (SV2) of the second temperature controller to the PV21 of the current value (PV2) of the second temperature controller,
The operation amount rewriting process of the second temperature controller, which rewrites the operation amount (MV2) of the second temperature controller to MV11 of the operation amount (MV1) of the first temperature controller,
A second control point switching process that switches the control of the rotation speed of the turbo compressor from the operation amount (MV1) dependence of the first temperature controller to the operation amount (MV2) dependence of the second temperature controller.
A method for controlling a refrigerator, comprising a step of changing the set value (SV2) of the second temperature controller with time from PV21 to SV21 with time. further,
After the transition command step to the second control mode, before the set value rewriting step of the second temperature controller, or after the set value rewriting step of the second temperature controller, the second. Before the operation amount rewriting process of the temperature controller of 2, the operation amount of the first temperature controller (MV1) is fixed to MV11, and the operation amount of the first temperature controller is fixed.
After the second control point switching step, the operation amount fixing release step of the first temperature controller is provided, which releases the fixation of the operation amount (MV1) of the first temperature controller.
The method for controlling a refrigerator according to claim 1. A turbo type that is arranged in the first circulation path through which the first refrigerant circulates, the second circulation path through which the second refrigerant circulates, and the first circulation path, and adiabatically compresses the first refrigerant. A compressor, a cooler arranged in the first circulation path and isostatically cooling the first refrigerant after adiabatic compression by the turbo compressor, and a cooler arranged in the first circulation path. A main heat exchanger that exchanges heat between the first refrigerant before adiabatic compression by the turbo compressor and the first refrigerant after isobaric cooling by the cooler, and the first heat exchanger. An expansion turbine arranged in the circulation path of the above and adiabatically expanding the first refrigerant, and the first circulation path and the second circulation path arranged in the first circulation path and the second circulation path. An auxiliary heat exchanger that exchanges heat, a first temperature controller arranged on the inlet side of the expansion turbine in the first circulation path, and an outlet side of the auxiliary heat exchanger in the second circulation path. The first temperature controller includes a second temperature controller arranged in the above, a turbo compressor, a first temperature controller, and a control device for controlling the second temperature controller. A method for controlling a refrigerator in which the control device controls the rotation speed of the turbo compressor depending on the operation amount (MV1) of the second temperature controller or the operation amount (MV2) of the second temperature controller.
The refrigerator has a first control mode in which the temperature of the first refrigerant is controlled at a target temperature by adjusting the rotation speed of the turbo compressor using the first temperature controller, and the above. It has a second control mode in which the temperature of the second refrigerant is controlled at a target temperature by adjusting the rotation speed of the turbo compressor using a second temperature controller.
A transition command process to the first control mode, which instructs the transition from the second control mode to the first control mode, and
The setting value rewriting process of the first temperature controller, which rewrites the SV11 of the set value (SV1) of the first temperature controller to the PV11 of the current value (PV1) of the first temperature controller,
The operation amount rewriting process of the first temperature controller, which rewrites the operation amount (MV1) of the first temperature controller to MV21 of the operation amount (MV2) of the second temperature controller,
The first control point switching process, which switches the control of the rotation speed of the turbo compressor from the operation amount (MV2) dependence of the second temperature controller to the operation amount (MV1) dependence of the first temperature controller,
A method for controlling a refrigerator, comprising a step of changing the set value (SV1) of the first temperature controller over time from PV11 to SV11, and a step of changing the set value of the first temperature controller over time. further,
After the set value rewriting step S22 of the first temperature controller, before the operation amount rewriting step S24 of the first temperature controller, or after the transition command step S21 to the first control mode. Before the set value rewriting step S22 of the first temperature controller, the operation amount fixing step of the second temperature controller is provided, in which the operation amount (MV2) of the second temperature controller is fixed to the MV21. ,
After the first control point switching step, the operation amount fixing release step of the second temperature controller is provided, which releases the fixation of the operation amount (MV2) of the second temperature controller.
The method for controlling a refrigerator according to claim 3. A control program for a refrigerator, which comprises causing a computer to execute the control method for the refrigerator according to any one of claims 1 to 4. A refrigerator comprising a control device equipped with the control program for the refrigerator according to claim 5.

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