JP2013231533A - Refrigerating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerating system capable of executing demand control to achieve both of maintaining of an inside temperature of a refrigerated storage and reduction of electric energy with respect to a refrigerating system having a plurality of refrigerating machines.SOLUTION: A refrigerating system executing demand control of refrigerating machines 10 respectively disposed in a plurality of refrigerated storages 1, includes an electric power meter 51 measuring power usage in the entire refrigerating system, inside temperature sensors 13 respectively measuring an inside temperature of each refrigerated storage 1, and a controller 50 to which a target value of power usage, operation set temperatures of the refrigerating machines 10, present temperatures of the refrigerated storages 1 measured by the inside temperature sensors 13, are input. The controller 50 compares the operation set temperature of each refrigerating machine 10 and the present temperature of each refrigerated storage, when the power usage within a prescribed time, measured by the electric power meter 51 may be over the target value, or is over the target value, and controls a capacity by demand control while giving priority to the refrigerating machine of the refrigerated storage having smaller temperature difference.

Description

  The present invention relates to a refrigeration system that performs demand control that performs target management of power for the purpose of reducing contract power and power receiving facilities and reducing the amount of power used.

  Conventionally, a refrigeration system that performs demand control has been implemented by controlling the operation and stop of a plurality of refrigerators. For example, Patent Document 1 discloses a demand control method for refrigerators installed in a plurality of refrigerated warehouses. When a demand signal is generated, the difference between the operation set temperature of the refrigerator and the current temperature of the refrigerated warehouse is disclosed. A method is disclosed in which the amount of change within a unit time is compared and a refrigerator in a refrigerated warehouse with a small change in temperature difference is preferentially stopped.

JP-A-10-339546

  In the conventional refrigeration system as shown in Patent Document 1, the amount of electric power is reduced by performing demand control for stopping the operating chiller when a demand signal is generated. For this reason, it is inevitable that the internal temperature of the refrigerated warehouse where the stopped freezer is installed rises, so there is a problem that it is difficult to perform demand control that achieves both maintenance of the internal temperature and reduction of electric energy. It was.

  The present invention has been made in order to solve the above-described problems, and demand control that achieves both maintenance of the internal temperature of a refrigerated warehouse and reduction of electric energy is targeted for a refrigeration system having a plurality of refrigerators. The aim is to obtain a possible refrigeration system.

The refrigeration system according to the present invention is a refrigeration system for demand-controlling a refrigerator provided in each of a plurality of refrigerated warehouses, and a power meter that measures the amount of power used by the entire refrigeration system, and the temperature inside each refrigerated warehouse is measured. A temperature controller, a target value of the electric energy used, an operation set temperature of each refrigerator, and a control controller to which a current temperature of each refrigerated warehouse measured by the temperature sensor is input,
When the controller is predicted that the amount of power used within a predetermined time measured by the power meter exceeds the target value, or exceeds the target value, the operation set temperature of each refrigerator and each refrigerated warehouse Compared with the current temperature, the capacity is controlled by demand control in preference to the refrigerator in the refrigerated warehouse where the temperature difference is small.

  According to the present invention, the controller is configured such that when the amount of power used within a predetermined time measured by the power meter is predicted to exceed the target value or exceeds the target value, the operation set temperature of each refrigerator is Compared with the current temperature of each refrigerated warehouse, capacity control is performed by demand control in preference to the refrigerator in the refrigerated warehouse where this temperature difference is small, so both increase in internal temperature and reduction of power consumption must be achieved. Can be obtained.

1 is a configuration diagram of a refrigeration system according to Embodiment 1 of the present invention. It is a demand course figure (the 1) of the refrigerating system concerning Embodiment 1 of the present invention. It is the demand progress figure (the 2) of the refrigerating system concerning Embodiment 1 of the present invention. It is a figure which shows the state of each store | warehouse | chamber temperature of the refrigeration system which concerns on Embodiment 1 of this invention. It is a figure which shows the relationship between the operating frequency of the refrigerator which concerns on Embodiment 4 of this invention, cooling capacity, power consumption, and COP.

  Embodiments of a refrigeration system according to the present invention will be described below with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a refrigeration system 100 according to Embodiment 1 of the present invention.
The refrigeration system 100 according to Embodiment 1 includes a refrigerated warehouse 1 having a plurality of partitioned rooms, a refrigerator 10 installed in each room of the refrigerated warehouse 1, and a control controller that controls the operation of the refrigerator 10. 50, and a wattmeter 51 that measures the amount of power used by the entire refrigeration system 100. The plurality of rooms in the refrigerated warehouse 1 are synonymous with the plurality of refrigerated warehouses.

  The refrigerated warehouse 1 stores objects to be cooled such as marine products, livestock products, agricultural products, and frozen foods, although not shown in the drawings. This refrigerated warehouse 1 is composed of, for example, five independent rooms, and each room has five units from the first to the fifth in order to maintain the internal temperature at the optimum temperature for storing the stored items. Refrigerating machines 10a to 10e are respectively installed. Each refrigerator 10a-10e is comprised by the heat-source equipment 11a-11e each installed outside the warehouse, and the coolers 12a-12e installed in the warehouse. Further, in each room of the refrigerated warehouse 1, warehouse temperature sensors 13a to 13e for detecting the warehouse temperature are respectively installed.

  The wattmeter 51 measures the power consumption of the entire refrigeration system 100, that is, the total power consumption including the refrigerator 10, the air conditioner, these auxiliary machines, and the verification instrument. The wattmeter 51 counts pulses transmitted according to the power used, and transmits the current power consumption to the control controller 50 of the refrigerator 10.

  The target demand value of the electric energy of each of the refrigerators 10a to 10e is input to the control controller 50, and the control controller 50 is installed in the set temperature and operating state of the refrigerators 10a to 10e and in each cabinet. Each refrigerator 10a is based on the result of comparing the calculated value with the target demand value by taking in and calculating the detected values of the internal temperature sensors 13a to 13e and the information on the current power consumption from the power measurement controller. -10e operation is controlled.

Next, the operation of the refrigeration system 100 according to the first embodiment will be described.
In order to keep the objects to be cooled such as marine products, agricultural products, and frozen foods stored in the five rooms of the refrigerated warehouse 1 at a suitable storage temperature, one refrigerator 10a to 10e is installed in each room. Has been. In each room of the refrigerated warehouse 1, a set temperature (operation set temperature) that is a target temperature of the inside temperature is set. The refrigerators 10a to 10e are all inverter refrigerators equipped with an inverter-driven compressor, and the cooling capacity (capacity) of the refrigerators 10a to 10e is independently controlled by controlling the operation frequency of the compressor with the inverter. It can be increased or decreased. In addition, internal temperature sensors 13 a to 13 e for detecting the current internal temperature of each room of the refrigerated warehouse 1 are installed, and the detected values are input to the controller 50. Furthermore, the wattmeter 51 measures all the electric energy used including the refrigerators 10 a to 10 e of the refrigeration system 100, the air conditioner, these auxiliary machines, and lighting equipment, and transmits the measured value to the control controller 50. .

  Next, the operation of the control controller 50 will be described. The controller 50 takes in the power consumption of the entire refrigeration system 100 from the power meter 51 and calculates a demand value. The demand value is an average power consumption obtained from a power consumption for a predetermined time (for example, 30 minutes). The average power consumption (current demand value) for 30 minutes and a preset target value (target demand) Value) and control the refrigerators 10a to 10e so that the current demand value does not exceed the target demand value.

  FIG. 2 is a graph called a demand progress diagram, and the operation of the controller 50 will be described using this graph. FIG. 2 is a graph in which the horizontal axis represents time, the vertical axis represents the demand value, and the average power consumption (power consumption per unit time) for 30 minutes from time 0 to the demand time limit. The solid line shown in FIG. 2 is an ideal straight line, and shows a case where the amount of power used for 30 minutes from time 0 is constant. For example, when the target demand value Pm is 100 kW, it is between time 0 and 30 minutes. The case where the amount of power used is constant at 100 kW is shown.

  In FIG. 2, the solid line indicated by the curve A indicates the demand value, and the current demand value P1 is indicated at time t1. In the figure, a straight line indicated by a broken line from the point B is a tangent to the curve A at the time t1, and indicates a demand predicted value when the demand value after the time t1 continues with the gradient at the point B. The demand value when the straight line indicated by the broken line reaches the demand time limit of 30 minutes is set as the predicted demand value Pf. Since the predicted demand value Pf is smaller than the target demand value Pm at the time t1 shown in FIG. 2, the controller 50 continues to operate the refrigerators 10a to 10e.

  FIG. 3 is a demand progress diagram at time t2 when time has elapsed from time t1, and the current demand value P2 is reached at time t2. Similar to FIG. 2, in FIG. 3, the horizontal axis represents time, and the vertical axis represents the demand value. Here, the predicted demand value Pf using the gradient at the point B is larger than the target demand value Pm, and if the operation of the refrigerators 10a to 10e is continued as it is, the target demand Pm is set at the time of the demand time limit of 30 minutes. Since there is a possibility of exceeding, the controller 50 restricts or partially stops the operation of the refrigerators 10a to 10e.

  In the first embodiment, as shown in FIG. 3, when the predicted demand value Pf is predicted to be larger than the target demand value Pm, or when the predicted demand value Pf is larger than the target demand value Pm, the refrigerators 10a to 10e Control is performed to decrease the operating frequency (capacity control amount) of the compressor, reduce the power consumption of the compressor of each of the refrigerators 10a to 10e, and reduce the power consumption of the entire system. In this control, a refrigerator that preferentially decreases the compressor operating frequency is selected in accordance with the internal temperature of each room of the refrigerated warehouse 1.

In a refrigerator equipped with an inverter compressor, generally, the compressor power consumption can be reduced by reducing the compressor operating frequency. At the same time, since the cooling capacity is reduced, the internal temperature rises, and there is a problem that the storage quality of the object to be cooled stored in the internal storage is lowered.
Therefore, in this embodiment, in order to minimize the deterioration of the storage quality, the value of the difference ΔT between the operation set temperature of the refrigerators 10a to 10e and the current temperature of each room of the refrigerator warehouse 1 is compared for each room. In addition, the compressor operating frequency of the refrigerator installed in the room where the temperature difference ΔT is small is preferentially controlled (capacity control).

  FIG. 4 is a diagram showing the state of the internal temperature of the refrigeration system according to the first embodiment, and shows the operation set temperature of the refrigerators 10a to 10e in the five rooms and the current temperature of each room in the refrigerated warehouse 1. It is a thing. Now, the operation set temperature of the refrigerators 10a to 10e is constant in all the rooms in FIG. 4, and the current temperature of each room is shown by a bar graph. In addition, in FIG. 4, when the internal temperature drops further, the thermo OFF point where the operating refrigerator is forcibly stopped, and when the internal temperature rises further, the stopped refrigerator is forcibly operated. The thermo-ON point to be performed is indicated by a broken line. The difference ΔT (ΔT = T1−T0) between the operation set temperature (T0) of each of the refrigerators 10a to 10e and the current temperature (T1) of each room shown in FIG. > 13c> 13a> 13b> 13d. That is, the current temperature of the room of the internal temperature sensor 13e is larger than the set temperature, and the internal cooling is most necessary, and then the internal cooling is required in the order of the room of the internal temperature sensors 13c and 13a. On the other hand, the current temperature of the room of the internal temperature sensor 13b matches the set temperature, and the current temperature of the room of the internal temperature sensor 13d is lower than the set temperature. However, it can be determined that the internal temperature does not rise significantly due to the heat capacity of the walls of the room and the objects to be stored.

  Therefore, in this embodiment, the compressor operating frequencies of the refrigerator 10b and the refrigerator 10d installed in the room where the difference ΔT between the operation set temperature of each of the refrigerators 10a to 10e and the current temperature of each room is small are set. For example, the controller 50 issues a command to the refrigerator 10b and the refrigerator 10d so as to reduce the current operating frequency by, for example, 10%, and controls to reduce the power consumption of the entire refrigeration system 100. That is, the compressor operating frequency of the three-room refrigerators 10e, 10c, and 10a having a large difference ΔT between the operation set temperature of the refrigerators 10a to 10e and the current room temperature does not decrease, and the two rooms having a small ΔT are not reduced. By controlling the compressor operating frequency of the refrigerators 10b and 10d to be, for example, 10% smaller than the current operating frequency, a refrigeration system capable of achieving both suppression of increase in the internal temperature and reduction of the amount of power used Can be obtained.

  In the present embodiment, the compressor is divided into a refrigerator that does not change the compressor operating frequency by ΔT and a refrigerator that reduces the compressor operating frequency, but is not limited to this, and the amount of reduction in the compressor operating frequency by ΔT is not limited to this. May be determined. That is, in the example of FIG. 4, ΔT is 13e> 13c> 13a> 13b> 13d. For example, the compressor operating frequency of the refrigerator 10e is 1%, and the compressor operating frequency of the refrigerator 10c is 2%. The compressor operating frequency of the refrigerator 10a is controlled to be 5%, the compressor operating frequency of the refrigerator 10b is 10%, and the compressor operating frequency of the refrigerator 10d is controlled to 20%. In this way, by increasing the amount of reduction in the compressor operating frequency of the refrigerator in the room where the internal temperature is sufficiently cooled, an increase in the internal temperature can be suppressed and a greater reduction in power consumption can be obtained.

Embodiment 2. FIG.
A refrigeration system according to Embodiment 2 of the present invention will be described. The configuration of the refrigeration system according to Embodiment 2 is the same as that in FIG. Items that are not particularly described are the same as those in the first embodiment, and the same functions and configurations are denoted by the same reference numerals, and redundant description is omitted. In this embodiment, the rated capacity information of the refrigerators 10a to 10e is input to the controller 50, and the rated capacity information and information on the difference ΔT between the operation set temperature of the refrigerators 10a to 10e and the current temperature of the room, The control amount of the compressor operating frequency of the refrigerators 10a to 10e is determined.

  Generally, in the case of an air-cooled model, the refrigerator is used for model selection, etc., with the cooling capacity when the outside air temperature is 32 ° C., the internal temperature is −25 ° C. and the compressor frequency is a low frequency, for example 70 Hz, as the rated capacity. . In addition, the compressor power consumption at the rated time is usually higher for models with a larger rated capacity, that is, a refrigerator with a larger rated capacity has a larger compressor power consumption, and conversely, a compressor with a smaller rated capacity also has a lower compressor power consumption. small. Therefore, when demand control is performed, demand control can be realized more effectively by using the rated capacity information of the refrigerator, that is, compressor power consumption information.

  In this embodiment, the rated capacity information of the refrigerators 10a to 10e is input to the controller 50, and the compressor operating frequency of the refrigerator having a large rated capacity is small and the compressor of the refrigerator having a small rated capacity is small. Increase the amount of reduction in operating frequency. That is, in the example of the internal temperature state shown in FIG. 4, the compressor operating frequencies of the three-room refrigerators 10e, 10c, and 10a having a large difference ΔT between the operation setting temperature of the refrigerator and the current room temperature are decreased. Without control, the compressor operating frequencies of the refrigerators 10b and 10d in the two rooms with small ΔT are controlled to be small. At this time, for example, when the rated capacity of the refrigerator 10b is 50 kW and the rated capacity of the refrigerator 10d is 30 kW, it is determined that the compressor power consumption is larger in the refrigerator 10b than in the refrigerator 10d. Control is performed so that the machine operation frequency is reduced by 10% and the compressor operation frequency of the refrigerator 10d is reduced by 20%.

  As described above, in the present embodiment, the amount of reduction in the compressor operating frequency of a refrigerator having a large rated capacity during demand control is small, and the amount of reduction in the compressor operating frequency of a refrigerator having a small rated capacity is increased. The amount of reduction in compressor power consumption of the refrigerator is averaged, and a greater effect of reducing the amount of power used can be obtained.

Embodiment 3 FIG.
A refrigeration system according to Embodiment 3 of the present invention will be described. The configuration of the refrigeration system according to Embodiment 3 is the same as that shown in FIG. Items that are not particularly described are the same as those in the first embodiment, and the same functions and configurations are denoted by the same reference numerals, and redundant description is omitted. In this embodiment, the efficiency information of the refrigerators 10a to 10e is input to the control controller 50, and the compressor operating frequency of the refrigerator is obtained from the efficiency information and information on the difference ΔT between the operation set temperature of the refrigerator and the current temperature of the room. The amount of control is determined.

  The efficiency information of the refrigerators 10a to 10e is input to the controller 50, and the reduction amount of the compressor operating frequency of the refrigerator with high efficiency is controlled to be small, and the reduction amount of the compressor operating frequency of the refrigerator with low efficiency is increased. So that it is controlled. That is, in the example of the internal temperature state shown in FIG. 4, the compressor operating frequencies of the three-room refrigerators 10e, 10c, and 10a having a large difference ΔT between the operation setting temperature of the refrigerator and the current room temperature are decreased. Without control, the compressor operating frequencies of the refrigerators 10b and 10d in the two rooms with small ΔT are controlled to be small. At this time, for example, when the efficiency (COP) of the refrigerator 10b is 1.5 and the efficiency (COP) of the refrigerator 10d is 1.0, the compressor operating frequency of the highly efficient refrigerator 10b is 10% and the efficiency is low. The compressor operating frequency of the refrigerator 10d is controlled to be reduced by 20%.

  As described above, in this embodiment, the amount of reduction in the compressor operating frequency of the highly efficient refrigerator is small during demand control, and the amount of reduction in the compressor operating frequency of the low efficiency refrigerator is controlled to be large. Therefore, it is possible to obtain a refrigeration system with high efficiency of the entire system by controlling so that a highly efficient refrigerator is operated with priority.

Embodiment 4 FIG.
A refrigeration system according to Embodiment 4 of the present invention will be described. The configuration of the refrigeration system according to Embodiment 4 is the same as that shown in FIG. Items that are not particularly described are the same as those in the first embodiment, and the same functions and configurations are denoted by the same reference numerals, and redundant description is omitted. In this embodiment, the lower limit value of the operating frequency of the refrigerator is input to the control controller 50, and when the compressor operating frequency of the refrigerator is equal to or lower than the lower limit value, the operation of the refrigerator is controlled to stop. ing.

  FIG. 5 is a diagram illustrating the relationship between the cooling capacity, the compressor power consumption, and the efficiency (COP) with respect to the compressor operating frequency of the refrigerator, where the horizontal axis represents the compressor operating frequency, the vertical axis represents the cooling capacity, and the middle stage. Indicates compressor power consumption, and the lower row indicates efficiency (COP). As the compressor operating frequency decreases, the cooling capacity and the compressor power consumption monotonously decrease, but the efficiency (COP) expressed by the ratio between the cooling capacity and the compressor power consumption has an extreme value. For this reason, if the operation frequency is decreased from the compressor operation upper limit frequency, the efficiency of the refrigerator increases, but the efficiency eventually decreases. The range where the efficiency at the compressor upper limit frequency or higher indicated by the broken line in FIG. 5 can be maintained is defined as the operation range, the compressor operation lower limit frequency is determined, and the frequency between the lower limit frequency and the upper limit frequency is set to the refrigerator operation. It is determined as a frequency.

  When demand control starts and a command to reduce the compressor operating frequency of the corresponding refrigerator is issued, the controller 50 controls the operation of the refrigerator when the reduced operating frequency becomes lower than the operation lower limit frequency. Control to stop. For example, the lower limit frequency of the refrigerator 10d is 30 Hz, the current operation frequency is 40 Hz, and if the compressor operation frequency reduction command of 20% is given to the refrigerator 10d during demand control, the compressor operation frequency is 32 Hz. In this case, since the lower limit frequency is higher than 30 Hz, the operation is continued.

  If the lower limit frequency of the refrigerator 10d is 30 Hz, the current operation frequency is 40 Hz, and the demand for controlling this compressor 10d is reduced by 30%, the compressor operation frequency is 28 Hz. In this case, Since the lower limit frequency is smaller than 30 Hz, the operation of this refrigerator is stopped.

  As described above, in this embodiment, when the compressor operating frequency of the refrigerator is equal to or lower than the preset lower limit value, the operation of the refrigerator is stopped and the operation is always performed with the efficiency (COP) of the refrigerator being high. By performing control so as to perform, a refrigeration system capable of demand control with high efficiency of the entire system can be provided.

Embodiment 5 FIG.
A refrigeration system according to Embodiment 5 of the present invention will be described. The configuration of the refrigeration system according to Embodiment 5 is the same as that shown in FIG. Items that are not particularly described are the same as those in the first embodiment, and the same functions and configurations are denoted by the same reference numerals, and redundant description is omitted. In this embodiment, the compressor operating frequency reduction amount of the refrigerator is controlled to be small in the initial demand period, and the compressor operating frequency reduction amount of the refrigerator is controlled to be large in the late demand period.

  In the demand progress diagram shown in FIG. 2 or FIG. 3, at the beginning of the demand time period from time 0 to 15 minutes, there is a time margin up to 30 minutes, which is the demand time end time, so control to suppress power consumption It is preferable to perform control giving priority to the maintenance of the internal temperature rather than. Conversely, in the latter period of the demand time period from 15 minutes to 30 minutes, it is preferable to perform control in which priority is given to setting the current demand value Pf to be equal to or less than the target demand value Pm rather than maintaining the internal temperature. From this point of view, in the present embodiment, when the compressor frequency of the refrigerator subjected to demand control is reduced, the amount of reduction in the compressor operating frequency of the refrigerator is reduced in the initial demand period, and the refrigerator is reduced in the latter period of the demand period. The compressor is controlled to increase the amount of reduction in the compressor operating frequency.

  As described above, in the present embodiment, by performing control giving priority to maintaining the internal temperature in the initial demand period, and performing control giving priority to the target demand value or less in the late demand period, the internal temperature over the entire demand period Both maintenance and the target demand value can be achieved.

  In the present embodiment, the compressor operating frequency reduction amount of the refrigerator subjected to demand control is reduced in the initial demand period, and the compressor operating frequency reduction amount of the refrigerator is increased in the late demand period. Although an example of control has been described, the present invention is not limited to this, and the compressor operating frequency of the refrigerator that is the target of demand control is reduced in the initial demand period, and the operation of the refrigerator is stopped in the latter period of the demand period. Thus, the same effect is exhibited even if the control is performed to reduce the amount of power used.

  In the present embodiment, the case of a refrigerator equipped with an inverter compressor has been described. However, the present invention is not limited to a capacity control type refrigerator using this inverter, but a mechanical capacity control having a slide valve inside the compressor. The same effect is exhibited even in a refrigerator equipped with a screw compressor having a mechanism. The same effect is exhibited even in a refrigerator having a capacity control system such as hot gas bypass or suction pressure adjustment.

  1 Refrigerated warehouse 10, 10a, 10b, 10c, 10d, 10e Refrigerator, 11a, 11b, 11c, 11d, 11e Heat source machine, 12a, 12b, 12c, 12d, 12e Cooler, 13, 13a, 13b, 13c, 13d, 13e Internal temperature sensor, 50 control controller, 51 wattmeter, 100 refrigeration system.

Claims (8)

In a refrigeration system for demand-controlling a refrigerator provided in each of a plurality of refrigerated warehouses,
A power meter that measures the amount of power used by the entire refrigeration system;
A temperature sensor that measures the internal temperature of each refrigerated warehouse;
A controller for inputting the target value of the electric energy used, the operation set temperature of each refrigerator, and the current temperature of each refrigerated warehouse measured by the temperature sensor;
With
When the controller is predicted that the amount of power used within a predetermined time measured by the power meter exceeds the target value, or exceeds the target value, the operation set temperature of each refrigerator and each refrigerated warehouse A refrigeration system that compares the current temperature and performs capacity control by demand control in preference to a refrigerator in a refrigerated warehouse where the temperature difference is small. 2. The refrigeration system according to claim 1, wherein the capacity control amount is increased as the chiller has a smaller temperature difference between the operation set temperature of each chiller and the current temperature of each refrigerated warehouse. The rated capacity information of each refrigerator is input to the control controller, and the controller determines a capacity control amount of each refrigerator according to the rated capacity information of each refrigerator. Refrigeration system. 2. The refrigeration system according to claim 1, wherein efficiency information of each refrigerator is input to the control controller, and the control controller determines a capacity control amount of each refrigerator according to the efficiency information of each refrigerator. . 2. The refrigeration system according to claim 1, wherein a capacity lower limit value of each refrigerator is input to the control controller, and the control controller performs demand control so as to stop the operation of the refrigerator having a capacity lower than the lower limit value. . The demand control is performed so that the capacity control amount of the refrigerator subjected to demand control is small in the initial demand period, and the capacity control amount of the refrigerator is increased in the late demand period. Refrigeration system. 7. The refrigeration system according to claim 6, wherein the capacity control of the refrigerator subjected to demand control is performed in the initial demand period, and the operation of the refrigerator is stopped in the latter period of the demand period. Each refrigeration machine is provided with an inverter drive compressor, The refrigeration system as described in any one of Claims 1-7 characterized by the above-mentioned.

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