Refrigeration system with cold storage device and its demand side response based control method

Abstract

A refrigeration system with a cold storage device and a demand-side response based control method thereof, the system comprising a carrier fluid outer circulation system, a carrier fluid inner circulation system, a cold storage device and a refrigeration unit; the carrier fluid outer circulation system comprising a carrier fluid pump set and a carrier fluid liquid supply main pipeline and a carrier fluid return liquid main pipeline connected to a cold using unit; the carrier fluid pump set being connected to the cold using unit through the carrier fluid liquid supply main pipeline; the carrier fluid inner circulation system comprising a carrier fluid return liquid pipeline and a carrier fluid liquid supply pipeline connected to the refrigeration unit and a carrier fluid total liquid supply pipeline connected to the carrier fluid liquid supply pipeline, the carrier fluid return liquid pipeline being connected to an inner circulation carrier fluid pump; the inner circulation carrier fluid pump being connected to an outer circulation high-temperature carrier fluid return liquid main pipeline and a first import and export pipeline of the cold storage device through a three-way valve; and a low-temperature carrier fluid total liquid supply pipeline being connected to the outer circulation carrier fluid pump set and a second import and export pipeline of the cold storage device through a three-way valve. The present application can realize active control and improve response speed.

Description

Technical Field

[0001] This invention belongs to the field of refrigeration system technology, specifically relating to a refrigeration system with a cold storage device and its control method based on demand-side response. Background Technology

[0002] For refrigeration systems, energy conservation and efficiency improvement of energy-consuming equipment and upgrading of production models have become the current development focus. Commercial and industrial refrigeration systems typically operate on a large scale, requiring 24-hour operation, with a clear alternation between peak and off-peak periods throughout the day. During peak production periods, the load surges, and if refrigeration equipment such as compressors lag in response and the cooling capacity fails to keep up with the load changes, it can impact safe production. Furthermore, prolonged high-load operation leads to high energy consumption and sometimes even overload. Conversely, during off-peak periods, compressors operate at low loads for extended periods, resulting in lower energy efficiency and potential waste of cooling capacity. By adding cold storage devices to the refrigeration system to store excess cooling capacity during low-load periods and release it during high-load periods, the peak-to-valley load difference can be effectively reduced, improving energy utilization efficiency.

[0003] In recent years, research on refrigeration systems using cold storage devices has mainly focused on the development of new cold storage materials, intelligent control of cold storage systems, and large-scale applications. Currently, these systems are being used in both air conditioning and data centers.

[0004] For example, patent application CN 114322142 A discloses a cold storage device, a refrigeration system, a refrigeration equipment and its control method, and patent application CN 115515400 A discloses a water-based cold storage refrigeration system and its cooling method for data centers. By using a water-based cold storage device, the power consumption of data center refrigeration units during peak periods is reduced, thereby reducing electricity costs, and various cold storage and refrigeration control modes are proposed.

[0005] In existing cold storage refrigeration systems, the switching between cold storage and release is mostly based on two traditional control methods. The first is timed control, such as starting the refrigeration unit in cold storage mode during low-load periods at night and stopping the refrigeration system during the day, relying solely on the stored cold energy to maintain system operation, or releasing cold energy during peak load periods to reduce the daytime operating load of the refrigeration unit. The second method is temperature control, such as adjusting the operating status of the refrigeration equipment based on changes in the building's internal temperature. When the indoor temperature is higher than the set value, the refrigeration unit is activated; when the temperature is at the set value, only the cold storage device provides cooling for the building. Timed control is simple and easy to implement but lacks flexibility and cannot adapt to sudden changes in end-user demand. Temperature control is based on the passively changing state parameter of temperature. Due to thermal inertia, changes in load only manifest as temperature changes after a period of time, and often cannot be promptly transmitted to the cold storage and refrigeration systems, resulting in a serious time lag problem and representing a passive demand-side response. Summary of the Invention

[0006] The purpose of this invention is to address the problems in the prior art by providing a refrigeration system with a cold storage device and a control method based on demand-side response, which effectively reduces the energy consumption of the refrigeration system during peak load periods, improves the energy utilization efficiency during off-peak periods, achieves active control based on demand-side response, accelerates the control response speed, and eliminates time lag problems.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A refrigeration system with a cold storage device includes a refrigerant external circulation system, a refrigerant internal circulation system, a cold storage device, and a refrigeration unit;

[0009] The refrigerant external circulation system includes an external circulation refrigerant pump set, and an external circulation low-temperature refrigerant supply main pipeline and an external circulation high-temperature refrigerant return main pipeline connected to the cooling unit; the external circulation refrigerant pump set is connected to the cooling unit through the external circulation low-temperature refrigerant supply main pipeline.

[0010] The refrigerant internal circulation system includes a high-temperature refrigerant return line and a low-temperature refrigerant supply line connected to the refrigeration unit, as well as a low-temperature refrigerant main supply line connected to the low-temperature refrigerant supply line. The high-temperature refrigerant return line is connected to the internal circulation refrigerant pump. The internal circulation refrigerant pump is connected to the external circulation high-temperature refrigerant return line and the first inlet and outlet lines of the cold storage device via a refrigerant return three-way valve of the refrigeration unit. The low-temperature refrigerant main supply line is connected to the external circulation refrigerant pump group and the second inlet and outlet lines of the cold storage device via a refrigerant supply three-way valve. The refrigerant flow direction is reversed depending on whether the cold storage device is in a cold storage state or a cold release state.

[0011] As a preferred embodiment, the external circulation refrigerant pump group consists of one or more refrigerant variable frequency pumps connected in parallel; the refrigeration unit consists of one or more vapor compression refrigeration units connected in parallel, each refrigeration unit is connected to a high-temperature refrigerant return line and a low-temperature refrigerant supply line, and each high-temperature refrigerant return line is equipped with an internal circulation refrigerant pump and a refrigeration unit refrigerant return three-way valve.

[0012] As a preferred embodiment, the cold storage device is a layered refrigerant storage tank, with the first inlet and outlet pipes located at the top and the second inlet and outlet pipes located at the bottom.

[0013] When the refrigerant stratified storage tank is in the cold storage state, the first inlet and outlet are the refrigerant outlets of the refrigerant stratified storage tank, and the second inlet and outlet are the refrigerant inlets of the refrigerant stratified storage tank. The flow direction of the refrigerant in the refrigerant stratified storage tank is from bottom to top.

[0014] When the refrigerant stratified storage tank is in the cooling state, the first inlet and outlet are the refrigerant inlets of the refrigerant stratified storage tank, and the second inlet and outlet are the refrigerant outlets of the refrigerant stratified storage tank. The flow direction of the refrigerant in the refrigerant stratified storage tank is from top to bottom.

[0015] As a preferred embodiment, a temperature sensor, a flow sensor, and a pressure sensor are installed on the external circulation low-temperature refrigerant supply main pipeline; a temperature sensor is installed on the external circulation high-temperature refrigerant return main pipeline.

[0016] The refrigerant stratified storage tank is equipped with a level sensor to detect changes in the liquid level inside the tank, and temperature sensors are installed in the upper, middle and lower layers inside the refrigerant stratified storage tank.

[0017] As a preferred embodiment, the refrigeration unit includes an evaporator, a throttling valve, a compressor, a condenser, and a cooling tower; the cooling tower is connected to the condenser, and the condenser and evaporator are connected through a refrigerant pipeline to form a circulating refrigeration system; the throttling valve and the compressor are located on the refrigerant pipeline; the high-temperature refrigerant return pipeline and the low-temperature refrigerant supply pipeline are connected to the evaporator.

[0018] As a preferred embodiment, a temperature sensor and a flow sensor are installed at the inlet of the evaporator connected to the high-temperature refrigerant return line;

[0019] A temperature sensor is installed at the outlet of the evaporator connected to the low-temperature refrigerant supply pipeline;

[0020] The compressor is equipped with a speed sensor and a slide valve position sensor.

[0021] As a preferred solution, the refrigeration capacity is adjusted by regulating the number of operating refrigeration units and the operating speed or slide valve position of the compressor in the operating refrigeration unit, so as to keep the water temperature and supply pressure of the external circulation low-temperature refrigerant supply pipeline within the safe operating range.

[0022] A demand-side response-based control method for a refrigeration system with a cold storage device includes the following steps:

[0023] Obtain the pressure measurement value P on the main supply line of the external circulation cryogenic refrigerant in the external circulation system. end Temperature measurement value T on the external circulation high-temperature refrigerant return main pipe back ;

[0024] Set condition one, where condition one is the pressure measurement value P. end Within the upper and lower limits of the required liquid supply pressure of the external refrigerant circulation system, and with the measured temperature T back Within the specified range; when condition one is met, maintain the operating status of the external circulation refrigerant pump group of the current external refrigerant circulation system.

[0025] Set condition two, where condition two is the pressure measurement value P. end Within the upper and lower limits of the required liquid supply pressure of the external refrigerant circulation system, and with the measured temperature T back Not within the specified range; when condition two is met, if the temperature measurement value T back If the value exceeds the specified upper limit, one additional external circulation refrigerant pump will be activated; conversely, if the value is below the limit, one external circulation refrigerant pump will be deactivated. The number of operating external circulation refrigerant pumps will be adjusted until the operating status of the above parameters changes from condition two to condition one.

[0026] Set condition three, where condition three is the pressure measurement value P. end The pressure is below the lower limit required by the external refrigerant circulation system, but does not exceed the lower safety warning limit; when condition three is met, if the temperature measurement value T... back If the temperature exceeds the specified upper limit, an additional external circulation refrigerant pump will be activated; if the temperature measurement value T back If the liquid supply pressure is below the required lower limit within the specified range, the external circulation refrigerant pump in operation will be controlled by frequency converter to maintain the liquid supply pressure at or above the required lower limit.

[0027] Set condition four, where condition four is the pressure measurement value P. end The pressure is higher than the upper limit of the liquid supply pressure required by the external circulation system of the refrigerant, but not higher than the upper limit of the safety warning limit; if condition four is met, the operating external circulation refrigerant pump will be controlled by frequency converter to maintain the liquid supply pressure not higher than the required upper limit.

[0028] Set condition five, where condition five is the pressure measurement value P.end Exceeding the upper and lower limits of the safety warning line; when condition five is met, if the pressure measurement value P end If the pressure drops below the lower safety warning limit, then add an external circulation refrigerant pump. If the pressure measurement value P... end If the value exceeds the safety warning limit, one external refrigerant pump will be switched off.

[0029] Adjust the pressure measurement value P using the steps described above. end Within the upper and lower limits of the required liquid supply pressure of the external refrigerant circulation system, and with the measured temperature T back Within the specified range, obtain the flow rate measurement value qv of the main pipeline for the external circulation cryogenic refrigerant supply. end The measured flow rate qv of the high-temperature refrigerant return line on each refrigeration unit in the internal circulation refrigeration system. n Temperature measurement value T of the low-temperature refrigerant supply pipeline on each refrigeration unit n And the average temperature T of the middle and lower layers of the refrigerant stratified storage tank. wt ;

[0030] Condition six is ​​set as the sum of the measured flow rates of the high-temperature refrigerant return lines on each currently operating refrigeration unit. Flow measurement value of the main pipeline for external circulation cryogenic refrigerant supply The difference is within the range of 1, and the average temperature measurement T of the middle and lower layers of the refrigerant stratified storage tank is... wt The temperature is below the upper limit of the refrigerant supply requirement of the external refrigerant circulation system; when condition six is ​​met, the number of refrigeration units in operation is maintained at the current level, and the compressor speed or slide valve position of the operating refrigeration units is adjusted to maintain the measured temperature T of the low-temperature refrigerant supply pipeline. n Not exceeding the production safety range; when the sum of the measured flow rates of the high-temperature refrigerant return lines on each operating refrigeration unit... Flow measurement value of the main pipeline for external circulation cryogenic refrigerant supply When the difference is positive, the refrigerant stratified storage tank is in a cold storage state; while when the difference is negative, the refrigerant stratified storage tank is in a cold release state.

[0031] Condition seven is set as the sum of the high-temperature refrigerant return liquid flow measurements on the high-temperature refrigerant return liquid pipeline of each operating refrigeration unit. Flow measurement value of the main pipeline for external circulation cryogenic refrigerant supply The difference is within range two, or the average temperature T between the middle and lower layers of the refrigerant stratified storage tank. wtIf the refrigerant temperature exceeds the upper limit of the refrigerant supply requirements of the external refrigerant circulation system, and condition seven is met, add a refrigeration unit and adjust the compressor speed or slide valve position of the operating refrigeration unit until the operating state changes from condition seven to condition six. If the condition is not met, add another refrigeration unit until condition six is ​​met. If the total cooling capacity of the refrigerant stratified storage tank and the cooling capacity of the operating refrigeration unit cannot meet the load requirements of the external refrigerant circulation system, or if the refrigerant temperature in the refrigerant stratified storage tank is higher than the upper limit of the refrigerant supply temperature, add a refrigeration unit to increase the cooling capacity or switch the operating state of the refrigerant stratified storage tank from cooling release to cooling storage.

[0032] Condition eight is set as the sum of the high-temperature refrigerant return liquid flow measurements on the high-temperature refrigerant return liquid pipeline of each operating refrigeration unit. Flow measurement value of the main pipeline for external circulation cryogenic refrigerant supply The difference is within range three, and the average temperature measurement T of the middle and lower layers of the refrigerant stratified storage tank is... wt If the refrigerant temperature is below the lower limit of the refrigerant supply requirement of the external refrigerant circulation system, and condition eight is met, then one refrigeration unit is shut down, and the compressor speed or slide valve position of the operating refrigeration unit is adjusted until the operating state changes from condition eight to condition six. If this condition is not met, another refrigeration unit is shut down until condition six is ​​met. If the total cooling capacity of the refrigerant stratified storage tank and the cooling capacity of the operating refrigeration unit exceeds the load of the external refrigerant circulation system, and the refrigerant temperature in the refrigerant stratified storage tank is below the lower limit of the supply temperature, then the refrigerant stratified storage tank has completely stored cold, and the operating state is switched from cold storage state to cold release state.

[0033] As a preferred option, the temperature measurement value T on the external circulation high-temperature refrigerant return main pipe is... back Within the specified range, determined experimentally: the measured temperature T on the external circulation high-temperature refrigerant return main pipe. back The upper limit value T back,UL To ensure that the refrigerant supply temperature of the refrigeration unit equals the upper limit of the refrigerant supply temperature required by the external circulation system, the refrigerant return temperature of the refrigeration unit is the refrigerant inlet temperature when the evaporator in the refrigeration unit reaches its heat exchange limit; the temperature measurement value T on the high-temperature refrigerant return main pipe of the external circulation system. back The lower limit value T back,DL To ensure that the compressor in the refrigeration unit operates at 20% of its rated load, the refrigerant return temperature of the refrigeration unit is...

[0034] As a preferred option, the sum of the high-temperature refrigerant return line flow measurements on each currently operating refrigeration unit is... Flow measurement value of the main pipeline for external circulation cryogenic refrigerant supply The range of the difference is divided as follows:

[0035] Range 1: Lower limit When the cooling capacity of the refrigerant stratified storage tank is equal to that of two-thirds of the refrigeration unit, the flow rate at the outlet of the refrigerant stratified storage tank is negative; upper limit. The value is the rated flow rate of the water entering two-thirds of the refrigeration units, and is a positive number. When the difference is negative, the refrigerant stratified storage tank is in a cooling release state; when the difference is positive, the refrigerant stratified storage tank is in a cooling storage state. The expression is as follows:

[0036]

[0037]

[0038]

[0039]

[0040] In the formula, Q 制冷机组 The rated cooling capacity of a single refrigeration unit; ΔT is the maximum temperature difference between the supply and return refrigerant liquids of the refrigeration unit; ρ is the density of the refrigerant; c p Where is the specific heat capacity of the refrigerant, and N is the number of operating refrigeration units. The rated flow rate of a single external circulation refrigerant pump in the external refrigerant circulation system;

[0041] Scope 2: The sum of flow measurements of the high-temperature refrigerant return line on each currently operating refrigeration unit. The flow rate is less than the measured value of the main supply line for the external circulation cryogenic refrigerant. Furthermore, when the absolute value of the difference is greater than the cooling capacity of the refrigerant stratified storage tank and two-thirds of the cooling capacity of the refrigeration unit, the flow rate at the outlet of the refrigerant stratified storage tank is expressed as follows:

[0042]

[0043]

[0044]

[0045] Scope 3: The sum of flow measurements of the high-temperature refrigerant return line on each currently operating refrigeration unit. The flow rate is greater than the measured value of the main supply line for the external circulation cryogenic refrigerant. Furthermore, the absolute value of the difference is greater than the rated flow rate of the inlet water for two-thirds of the chiller units, as expressed below:

[0046]

[0047]

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] This invention, featuring a cold storage device, effectively reduces energy consumption during peak load periods and improves energy efficiency during off-peak periods, lowering the overall electricity cost of system operation. It offers significant economic benefits and is applicable to industrial and commercial refrigeration systems, as well as liquid-cooled data center refrigeration systems, demonstrating broad applicability. The invention sets the cold storage and release control signals of the cold storage device based on the difference between the refrigerant supply flow rate and the refrigerant demand flow rate on the demand side. This makes the entire refrigeration system more sensitive to load and flow rate changes on the demand side. When the cooling load surges, it can quickly release the stored cold energy, improving response speed and solving the time lag problem of traditional control strategies. It is a proactive control method based on demand-side response. Furthermore, this invention improves the refrigerant supply flow rate control method on the demand side by adding a limitation on the supply flow rate based on the refrigerant return temperature after heat exchange on the demand side, in addition to real-time adjustment according to load changes. By controlling the refrigerant return temperature, i.e., the refrigerant return temperature of the chiller unit, within the upper limit of the chiller unit's heat exchange capacity, the chiller unit's operating energy efficiency is maximized. This allows for the rational adjustment of the refrigerant supply flow rate without altering the demand-side refrigerant supply temperature and pressure, thereby improving the overall energy utilization efficiency of the system. Attached Figure Description

[0050] Figure 1 A schematic diagram of the structure of the refrigeration system with a cold storage device in the cold storage state according to an embodiment of the present invention;

[0051] Figure 2 A schematic diagram of the structure of the refrigeration system with a cold storage device in the cold release state according to an embodiment of the present invention;

[0052] Figure 3 A schematic diagram of the structure of the refrigeration unit according to an embodiment of the present invention;

[0053] Figure 4 This invention uses a layered refrigerant storage tank as a structural diagram of a cold storage device.

[0054] Figure 5 The present invention relates to a flowchart of a demand-side response-based control method for a refrigeration system.

[0055] In the attached diagram: 10 - External refrigerant circulation system; 110 - Cooling unit; 111 - External circulation high-temperature refrigerant return main pipeline; 112 - External circulation low-temperature refrigerant supply main pipeline; 113 - Temperature sensor for external circulation high-temperature refrigerant return main pipeline; 114 - Temperature sensor for external circulation low-temperature refrigerant supply main pipeline; 115 - Flow sensor for external circulation low-temperature refrigerant supply main pipeline; 116 - Pressure sensor for external circulation low-temperature refrigerant supply main pipeline; 120 - External circulation refrigerant pump unit; 121 - First external circulation refrigerant Pumps; 122 - Second external circulation refrigerant pump; 123 - Third external circulation refrigerant pump; 130 - Refrigerant stratified storage tank; 131 - Upper inlet / outlet piping of refrigerant stratified storage tank; 132 - Lower inlet / outlet piping of refrigerant stratified storage tank; 134 - Liquid level sensor; 135 - Upper layer temperature sensor of cold storage stratified storage tank; 136 - Middle layer temperature sensor of cold storage stratified storage tank; 137 - Middle layer temperature sensor of lower layer cold storage tank; 140 - Refrigerant supply three-way valve; 20 - Refrigeration unit; 210 - Evaporator; 211 - Refrigeration unit 212 - Refrigerant return temperature sensor for the first refrigeration unit; 213 - Refrigerant supply temperature sensor for the second refrigeration unit; 220 - Throttling valve; 230 - Compressor; 231 - Speed ​​sensor; 232 - Slide valve position sensor; 240 - Condenser; 250 - Cooling tower; 261 - High-temperature refrigerant return line for the first refrigeration unit; 262 - High-temperature refrigerant return line for the second refrigeration unit; 263 - High-temperature refrigerant return line for the third refrigeration unit; 270 - Low-temperature refrigerant main supply line. 271 - Low-temperature refrigerant supply line for the first refrigeration unit; 272 - Low-temperature refrigerant supply line for the second refrigeration unit; 273 - Low-temperature refrigerant supply line for the third refrigeration unit; 30 - Refrigerant return device for the refrigeration unit; 311 - First internal circulation refrigerant pump; 312 - Second internal circulation refrigerant pump; 313 - Third internal circulation refrigerant pump; 321 - Refrigerant return three-way valve for the first refrigeration unit; 322 - Refrigerant return three-way valve for the second refrigeration unit; 323 - Refrigerant return three-way valve for the third refrigeration unit. Detailed Implementation

[0056] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0057] Please see Figure 1 and Figure 2This invention provides a refrigeration system with a cold storage device, comprising a refrigerant external circulation system 10, a refrigerant internal circulation system, a cold storage device, and a refrigeration unit 20. The refrigerant external circulation system 10 includes an external circulation refrigerant pump group 120. In the embodiment shown, the external circulation refrigerant pump group 120 is composed of a first external circulation refrigerant pump 121, a second external circulation refrigerant pump 122, and a third external circulation refrigerant pump 123 connected in parallel. It also includes an external circulation low-temperature refrigerant supply main pipeline 112 and an external circulation high-temperature refrigerant return main pipeline 111 connected to the cooling unit 110. The external circulation refrigerant pump group 120 is connected to the cooling unit 110 via the external circulation low-temperature refrigerant supply main pipeline 112. The refrigerant internal circulation system includes a high-temperature refrigerant return line and a low-temperature refrigerant supply line connected to the refrigeration unit 20, and a low-temperature refrigerant main supply line 270 connected to the low-temperature refrigerant supply line. The high-temperature refrigerant return line is connected to the internal circulation refrigerant pump. The internal circulation refrigerant pump is connected to the external circulation high-temperature refrigerant return line 111 and the first inlet and outlet lines of the cold storage device via a refrigeration unit refrigerant return three-way valve. The low-temperature refrigerant main supply line 270 is connected to the external circulation refrigerant pump group 120 and the second inlet and outlet lines of the cold storage device via a refrigerant supply three-way valve 140. In the embodiment shown in the figure, the refrigeration unit 20 is composed of refrigeration units #1 to #3 connected in parallel. Each refrigeration unit 20 is connected to a high-temperature refrigerant return line and a low-temperature refrigerant supply line. Each high-temperature refrigerant return line is equipped with an internal circulation refrigerant pump and a refrigeration unit refrigerant return three-way valve. The refrigerant internal circulation system operates in opposite directions depending on whether the refrigerant storage device is in a refrigerant storage or refrigerant release state. Furthermore, in this embodiment of the invention, the refrigerant storage device is a refrigerant stratified storage tank 130, with a first inlet / outlet pipe located at the top and a second inlet / outlet pipe located at the bottom. When the refrigerant stratified storage tank 130 is in a refrigerant storage state, the first inlet / outlet is the refrigerant outlet of the refrigerant stratified storage tank 130, and the second inlet / outlet is the refrigerant inlet of the refrigerant stratified storage tank 130, with the refrigerant flowing from bottom to top. When the refrigerant stratified storage tank 130 is in a refrigerant release state, the first inlet / outlet is the refrigerant inlet of the refrigerant stratified storage tank 130, and the second inlet / outlet is the refrigerant outlet of the refrigerant stratified storage tank 130, with the refrigerant flowing from top to bottom.

[0058] When the refrigerant stratified storage tank 130 is in the cold storage and cold release states respectively, the flow mode of the refrigerant in the external circulation and internal circulation systems is as follows: During cold storage, the refrigerant with a higher temperature in the middle and upper layers of the refrigerant stratified storage tank 130 is drawn and mixed with the high-temperature refrigerant in the external circulation high-temperature refrigerant return main pipeline 111 by the refrigerant return liquid three-way valve of the refrigeration unit and then sent to the refrigeration unit for cooling. The cooled low-temperature refrigerant is sent to the external circulation cooling demand side for cooling through one side pipeline of the refrigerant supply liquid three-way valve 140. The excess low-temperature refrigerant is returned to the refrigerant stratified storage tank 130 for storage through the other side pipeline of the refrigerant supply liquid three-way valve 140. During cooling, the total low-temperature refrigerant supply on the external circulation side is composed of the total low-temperature refrigerant supply of the refrigeration unit mixed by the refrigerant supply three-way valve 140 and the low-temperature refrigerant storage liquid in the middle and lower layers of the refrigerant stratified storage tank 130. The total high-temperature refrigerant return liquid on the external circulation side is partially sent to the upper layer of the refrigerant stratified storage tank 130 by the internal circulation refrigerant pump, and part of it is directly sent to the refrigeration unit 20 for cooling.

[0059] The calculation method for the cold storage capacity and volume of the refrigerant stratified storage tank 130 is as follows:

[0060] Based on the actual investment cost and workshop size, the cooling storage time of the storage tanks is selected to be 20 minutes to 2 hours. Calculate the cooling storage capacity and required volume of the stratified storage tanks based on the rated cooling capacity of a single refrigeration unit.

[0061] Q 储罐 =Q 机组制冷量 ·t

[0062]

[0063]

[0064] In the formula, Q 机组制冷量 V represents the rated cooling capacity of a single refrigeration unit; t represents the cold storage time; V t储罐 ρ is the theoretical volume of the stratified refrigerant storage tank; ΔT is the maximum temperature difference between the refrigerant supply and return liquids in the external circulation system; ρ is the density of the refrigerant; c p V is the specific heat capacity of the refrigerant; N is the number of operating refrigeration units; V 储罐 η is the total volume of the stratified refrigerant storage tanks; 储罐 Efficiency of stratified storage tanks for refrigerants.

[0065] Please see Figure 3In one possible implementation, the refrigeration unit 20 includes an evaporator 210, a throttling valve 220, a compressor 230, a condenser 240, and a cooling tower 250. The cooling tower 250 is connected to the condenser 240, and the condenser 240 and evaporator 210 are connected via refrigerant piping to form a circulating refrigeration system. The throttling valve 220 and compressor 230 are located on the refrigerant piping. A high-temperature refrigerant return line and a low-temperature refrigerant supply line are connected to the evaporator 210. A temperature sensor and a flow sensor are installed at the inlet of the evaporator 210 connected to the high-temperature refrigerant return line; a temperature sensor is installed at the outlet of the evaporator 210 connected to the low-temperature refrigerant supply line; and a speed sensor 231 and a slide valve position sensor 232 are installed on the compressor 230. In one possible implementation, the total rated cooling capacity of the refrigeration unit 20 should be at least 1.25 times the rated load on the cooling demand side. The cooling capacity of the internal circulation system is roughly adjusted by starting and stopping the refrigeration unit 20, and fine adjustment is achieved by controlling the speed of the compressor 230 or the position of the slide valve in a single refrigeration unit 20. In this embodiment of the invention, the evaporator 210 adopts a plate heat exchanger, with ice water on the hot side and ammonia as the refrigerant on the cold side.

[0066] Please see Figure 4 In one possible implementation, a temperature sensor, a flow sensor, and a pressure sensor are installed on the external circulation low-temperature refrigerant supply main pipeline 112; a temperature sensor is installed on the external circulation high-temperature refrigerant return main pipeline 111; a level sensor is installed in the refrigerant stratified storage tank 130 to detect changes in the liquid level inside the tank, and temperature sensors are installed in the upper, middle, and lower layers inside the refrigerant stratified storage tank 130 to detect temperature changes inside the refrigerant stratified storage tank 130. In this embodiment of the invention, the chilled water supply source of the refrigeration system with a cold storage device can consist of chilled water provided by the refrigeration unit 20 and the refrigerant stratified storage tank 130. The return water from the external circulation production workshop can be entirely sent to the refrigeration unit 20 for cooling or partially returned to the refrigerant stratified storage tank 130 to mix with the stored chilled water for cooling. The level sensor detects changes in the liquid level inside the tank and replenishes water in a timely manner.

[0067] In one possible implementation, the aforementioned flow sensor, temperature sensor, pressure sensor, level sensor, and other sensors send the collected signals to the control device. The control device uses PID control to adjust the cooling capacity of the refrigeration unit 20 in the internal circulation system based on the measured values ​​of the flow, temperature, pressure, and level sensors.

[0068] Furthermore, in this embodiment of the invention, the cooling capacity is adjusted by regulating the number of operating refrigeration units 20 and the operating speed or slide valve position of the compressor 230 in the operating refrigeration unit 20, so as to keep the water temperature and water supply pressure of the external circulation low-temperature refrigerant supply main pipeline 112 within the safe operating range, thereby achieving active control and improving the response speed.

[0069] Please see Figure 5 This invention also proposes a demand-side response-based control method for a refrigeration system with a cold storage device, comprising the following steps:

[0070] Obtain the pressure measurement value P on the external circulation cryogenic refrigerant supply main pipeline 112 in the external circulation refrigerant system 10. end The temperature measurement value T on the external circulation high-temperature refrigerant return main pipe 111 back ;

[0071] Set condition one, where condition one is the pressure measurement value P. end Within the upper and lower limits of the required liquid supply pressure of the external refrigerant circulation system 10, and with the measured temperature value T back Within the specified range; when condition one is met, maintain the current operating state of the external circulation refrigerant pump group 120 of the external circulation system 10;

[0072] Set condition two, where condition two is the pressure measurement value P. end Within the upper and lower limits of the required liquid supply pressure of the external refrigerant circulation system 10, and with the measured temperature value T back Not within the specified range; when condition two is met, if the temperature measurement value T back If the value exceeds the specified upper limit, one additional external circulation refrigerant pump will be activated; conversely, if the value is below the limit, one external circulation refrigerant pump will be deactivated. The number of operating external circulation refrigerant pumps will be adjusted until the operating status of the above parameters changes from condition two to condition one.

[0073] Set condition three, where condition three is the pressure measurement value P. end The pressure is below the lower limit of the refrigerant external circulation system's liquid supply pressure requirement, but does not exceed the safety warning lower limit; when condition three is met, if the temperature measurement value T... back If the temperature exceeds the specified upper limit, an additional external circulation refrigerant pump will be activated; if the temperature measurement value T back If the liquid supply pressure is below the required lower limit within the specified range, the external circulation refrigerant pump in operation will be controlled by frequency converter to maintain the liquid supply pressure at or above the required lower limit.

[0074] Set condition four, where condition four is the pressure measurement value P. endThe pressure is higher than the upper limit of the liquid supply pressure required by the external circulation system of the refrigerant, but not exceeding the upper limit of the safety warning limit; if condition four is met, the operating external circulation refrigerant pump will be controlled by frequency converter to maintain the liquid supply pressure not higher than the required upper limit.

[0075] Set condition five, where condition five is the pressure measurement value P. end Exceeding the upper and lower limits of the safety warning line; when condition five is met, if the pressure measurement value P end If the pressure drops below the lower safety warning limit, then add an external circulation refrigerant pump. If the pressure measurement value P... end If the value exceeds the safety warning limit, one external refrigerant pump will be switched off.

[0076] Adjust the pressure measurement value P using the steps described above. end Within the upper and lower limits of the required liquid supply pressure of the external refrigerant circulation system 10, and with the measured temperature value T back Within the specified range, obtain the flow rate measurement value qv of the external circulation cryogenic refrigerant supply main pipeline 112. end The measured flow rate qv of the high-temperature refrigerant return line on each refrigeration unit 20 in the internal circulation refrigeration system. n Temperature measurement value T of the low-temperature refrigerant supply pipeline on each refrigeration unit 20 n And the average temperature T of the middle and lower layers of the refrigerant stratified storage tank 130. wt ;

[0077] Condition six is ​​set as the sum of the high-temperature refrigerant return line flow measurements on each currently operating refrigeration unit 20. Flow measurement value of the main supply line 112 for external circulation cryogenic refrigerant The difference is within the range of 1, and the average temperature measurement values ​​T of the middle and lower layers of the refrigerant stratified storage tank 130 are... wt The temperature is below the upper limit of the refrigerant supply requirement of the external refrigerant circulation system 10; when condition six is ​​met, the refrigeration unit 20 maintains the current number of operating units, and adjusts the compressor speed or slide valve position of the operating refrigeration unit 20 to maintain the measured temperature T of the low-temperature refrigerant supply pipeline. n Not exceeding the production safety range; when the sum of the measured flow rates of the high-temperature refrigerant return lines on each operating refrigeration unit 20 Flow measurement value of the main supply line 112 for external circulation cryogenic refrigerant When the difference is positive, the refrigerant stratified storage tank 130 is in a cold storage state; while when the difference is negative, the refrigerant stratified storage tank 130 is in a cold release state.

[0078] Condition seven is set as the sum of the high-temperature refrigerant return liquid flow measurements on the high-temperature refrigerant return liquid pipeline of each operating refrigeration unit 20. Flow measurement value of the main supply line 112 for external circulation cryogenic refrigerant The difference is within range two, or the average temperature T between the middle and lower layers of the refrigerant stratified storage tank 130. wt If the refrigerant supply temperature exceeds the upper limit of the refrigerant supply requirements of the external refrigerant circulation system 10, and condition seven is met, an additional refrigeration unit 20 is started, and the compressor speed or slide valve position of the running refrigeration unit 20 is adjusted until the operating state changes from condition seven to condition six. If the condition is not met, another refrigeration unit 20 is started until condition six is ​​met. If the total cooling capacity of the refrigerant stratified storage tank 130 and the cooling capacity of the running refrigeration unit 20 cannot meet the load requirements of the external refrigerant circulation system 10, or if the refrigerant temperature in the refrigerant stratified storage tank 130 is higher than the upper limit of the refrigerant supply temperature, then an additional refrigeration unit 20 is started to increase the cooling capacity or the operating state of the refrigerant stratified storage tank 130 is switched from cooling release to cooling storage.

[0079] Condition eight is set as the sum of the high-temperature refrigerant return liquid flow measurements on the high-temperature refrigerant return liquid pipeline of each operating refrigeration unit 20. Flow measurement value of the main supply line 112 for external circulation cryogenic refrigerant The difference is within range three, and the average temperature measurement T of the middle and lower layers of the refrigerant stratified storage tank 130 is... wt If the refrigerant temperature is below the lower limit of the refrigerant supply requirement of the external refrigerant circulation system 10, and condition eight is met, then one refrigeration unit 20 is shut down, and the compressor speed or slide valve position of the operating refrigeration unit 20 is adjusted until the operating state changes from condition eight to condition six. If the condition is not met, then another refrigeration unit 20 is shut down until condition six is ​​met. If the total cooling capacity of the refrigerant stratified storage tank 130 and the cooling capacity of the operating refrigeration unit 20 exceeds the load of the external refrigerant circulation system 10, and the refrigerant temperature in the refrigerant stratified storage tank 130 is below the lower limit of the supply temperature, then the refrigerant stratified storage tank 130 has completely stored cold, and the operating state is switched from the cold storage state to the cold release state.

[0080] In one possible implementation, the temperature measurement value T on the external circulating high-temperature refrigerant return main line 111 is... back Within the specified range, determined experimentally, the temperature measurement value T on the external circulation high-temperature refrigerant return main pipe 111 is as follows: back The upper limit value T back,UL To ensure that the refrigerant supply temperature of the refrigeration unit 20 is equal to the upper limit of the supply temperature required by the external refrigerant circulation system 10, the refrigerant return temperature of the refrigeration unit 20 is the refrigerant inlet temperature when the evaporator 210 in the refrigeration unit 20 reaches the upper limit of heat exchange; the temperature measurement value T on the external circulation high-temperature refrigerant return main pipeline 111. back The lower limit value T back,DLTo ensure that the compressor 230 in the refrigeration unit 20 operates at 20% of its rated load, the refrigerant return temperature of the refrigeration unit 20 is...

[0081] In one possible implementation, the sum of the high-temperature refrigerant return line flow measurements on each currently operating chiller unit 20 is... Flow measurement value of the main supply line 112 for external circulation cryogenic refrigerant The range of the difference is divided into:

[0082] Range 1: Lower limit When the cooling capacity of the refrigerant stratified storage tank 130 is the same as that of two-thirds of the cooling capacity of the refrigeration unit 20, the flow rate at the outlet of the refrigerant stratified storage tank 130 is negative; upper limit. The value is the rated flow rate of the inlet water for two-thirds of the refrigeration units 20, and is a positive number. When the difference is negative, the refrigerant stratification storage tank 130 is in a cooling release state; when the difference is positive, the refrigerant stratification storage tank 130 is in a cooling storage state, as expressed below:

[0083]

[0084]

[0085]

[0086]

[0087] In the formula, Q 制冷机组 The rated cooling capacity of a single refrigeration unit; ΔT is the maximum temperature difference between the supply and return refrigerant liquids of the refrigeration unit; ρ is the density of the refrigerant; c p Where is the specific heat capacity of the refrigerant, and N is the number of operating refrigeration units. The rated flow rate of a single external circulation refrigerant pump in the external refrigerant circulation system 10;

[0088] Scope 2: The sum of the measured flow rates of the high-temperature refrigerant return lines on each currently operating refrigeration unit 20. The flow rate is less than the measured value of the main supply line 112 for the external circulation cryogenic refrigerant. And when the absolute value of the difference is greater than the cooling capacity of the refrigerant stratified storage tank 130 and two-thirds of the cooling capacity of the refrigeration unit 20, the flow rate at the outlet of the refrigerant stratified storage tank 130 is:

[0089]

[0090]

[0091]

[0092] Scope 3: The sum of the measured flow rates of the high-temperature refrigerant return lines on each currently operating refrigeration unit 20. The flow rate is greater than the measured value of the main supply line 112 for the external circulation cryogenic refrigerant. Furthermore, the absolute value of the difference is greater than the rated flow rate of 20 cubic meters of water inlet for two-thirds of the chiller units, as expressed below:

[0093]

[0094]

[0095] Specifically, this invention is applied to an industrial refrigeration system. The cooling demand side of the external circulation system is a liquid milk production workshop, with chilled water as the refrigerant. The chilled water supply pressure and temperature requirements for the liquid milk production workshop are shown in Table 1. The external circulation refrigerant pump group 120 includes three variable frequency water pumps. The internal circulation refrigeration system has three refrigeration units 20, each equipped with an internal circulation refrigerant pump and a three-way valve for refrigerant return. The compressors 230 in each refrigeration unit 20 are variable frequency screw compressors, and the refrigerant is ammonia. The selection of the main equipment for the entire system is shown in Table 2.

[0096] Table 1

[0097]

[0098] Table 2

[0099]

[0100] The refrigerant stratified storage tank 130 is a stratified ice water storage tank. Considering the size of the refrigeration station and the manufacturing cost of the stratified storage tank, the cooling time of the tank is selected as 50 minutes. According to the following formula, the required volume of the tank is at least 317 m³. 3 A stainless steel water tank with an inner diameter of 4.8m and a height of 20m was selected as the stratified storage tank for chilled water.

[0101] Q 水罐 =Q 机组制冷量 ·t

[0102]

[0103]

[0104] In the formula, Q 机组制冷量 The rated cooling capacity of a single refrigeration unit is 3000kW; t is the cooling time, 50min; V t水罐 ρ is the theoretical volume of the water tank; ΔT is the maximum temperature difference between the supply and return water in the workshop, 7℃; ρ is the density of water, 999.9 kg / m³. 3 ;c pV is the specific heat capacity of water, 4.2 kJ / (kg·℃); 水罐 η is the total volume of the cold water storage tank. 水罐 The efficiency of the cold water storage tank is taken as 0.9.

[0105] Before the refrigeration system with a cold storage device in this embodiment of the invention is put into production operation, the high-temperature return water temperature T of the external circulating chilled water should be determined first. back The specified range, total chilled water flow rate of the refrigeration unit Ice water supply flow rate of external circulation system The difference. A control signal used to determine the chilled water supply flow rate of the external circulation system and the system's cold storage and release operating status.

[0106] Experiments show that, under the evaporation temperature required by the production workshop and the condensation temperature determined by the ambient temperature, the inlet water temperature of the refrigeration unit should be 9–11°C to maintain the COP of the refrigeration unit within the optimal range. When the inlet water temperature exceeds 11°C, the outlet water temperature will be higher than 4°C, failing to meet the workshop's safe production requirements. When the inlet water temperature is below 9°C, if the compressor is operating at a high speed, the evaporator outlet chilled water temperature will be too low for the same cooling capacity. This leads to wasted cooling capacity and the evaporator may freeze, causing a malfunction.

[0107] According to calculations, and The lower limit of the difference The value should be a negative value for the flow rate at the tank outlet when the cooling capacity is the same as that of two-thirds of the refrigeration units. (Upper limit) This is the rated flow rate of two-thirds of the refrigeration unit's inlet water pumps, and the value is positive. When the difference is negative, the water tank is in a cooling release state; when the difference is positive, the water tank is in a cooling storage state.

[0108]

[0109]

[0110]

[0111]

[0112] In the formula, Q 制冷机组 The rated cooling capacity of a single refrigeration unit is 3000kW; ΔT is the maximum temperature difference between the chilled water supply and return liquids of the refrigeration unit, 7℃; ρ is the density of water, 999.9kg / m³. 3 ;c p Where is the specific heat capacity of water, 4.2 kJ / (kg·℃), and N is the number of operating refrigeration units. The rated flow rate of a single chilled water supply pump in the external circulation system is 258m³. 3 / h. Table 3 shows all the control signal boundaries in the demand-side response-based control method.

[0113] Table 3

[0114]

[0115] The control method for the above-mentioned refrigeration system based on demand-side response, as described in this embodiment of the invention, mainly includes the following steps:

[0116] Obtain the pressure measurement value P on the chilled water supply main pipe of the production workshop. end Temperature measurement value T on the workshop return water main pipe back .

[0117] Adjustment of the chilled water supply pump set in the production workshop:

[0118] When the water supply pressure P end When the return water temperature is within the safe range required for production, and is between 9 and 111°C, the refrigeration units in operation are all in a high-efficiency operating state, and there is no need to adjust the operating status of the chilled water supply pump. The control signal is:

[0119] 4 < P end <5

[0120] 9≤T back ≤11

[0121] When the return water temperature is above 11℃, it indicates that the end-product load is increasing, and an additional chilled water supply pump needs to be started; when the return water temperature is below 9℃, it indicates that the production workshop load is decreasing, and there is excess cooling capacity, so one chilled water supply pump can be removed from the pump. The control signal conforms to the following expression:

[0122] T back >11

[0123] T back <9

[0124] As the workshop load continues to decline and enters a production trough, the pump unit's water supply pressure rapidly drops below 3.8 bar, reaching the safety lower limit. It is necessary to immediately start an additional water supply pump to maintain the water supply pressure. The control signal is...

[0125] P end ≤3.8

[0126] When the supply water pressure is 3.8–4.0 bar, if the return water temperature does not exceed 11°C, it indicates that the required chilled water flow rate for production is very low, and the production load is low. Adjusting the speed of the chilled water supply pump set to maintain the lower limit of the production pressure is sufficient. The control signal is:

[0127] 3.8≤P end <4

[0128] 9≤T back ≤11

[0129] If the return water temperature rises above 11℃, it indicates an increase in production load; in this case, simply increase the number of chilled water supply pumps.

[0130] T back >11

[0131] As the workshop load continues to rise and production enters its peak period, the water supply pressure of the pump set rapidly increases to above 5.2 bar, reaching the safety limit. At this point, one water supply pump must be switched off to maintain the water supply pressure. The control signal is:

[0132] P end ≥5.2

[0133] When the water supply pressure is 5.0–5.2 bar, the production load is very high. Adjusting the speed of the chilled water supply pump unit to maintain the upper limit of the water supply pressure is sufficient. The control signal meets the following requirements:

[0134] 5.0≤P end <5.2

[0135] Obtain flow rate measurements on the main water supply pipe of the demand-side chilled water external circulation system. Flow measurement value on the main inlet pipe of each refrigeration unit in the refrigeration system Temperature measurement value T of the lower layer in the stratified chilled water storage tank wt .

[0136] The refrigeration unit remains in operation as is, in the stage of releasing or storing cold water from the tank:

[0137] The maximum cooling capacity of the chilled water stratified storage tank is two-thirds of the cooling capacity of a single unit. Calculations show that the maximum cooling flow rate of the storage tank is 244 m³ / s. 3 / h.

[0138] If the total inlet water flow of the currently operating chiller units is Less than However, it should not exceed the upper limit of the cooling flow rate of the water storage tank, and the temperature T of the lower layer of the water tank should be within acceptable limits. wt When the temperature is below 5℃, the water tank's cold storage capacity is considered sufficient. The chilled water supply for the external circulation system is provided by both the chilled water from the water tank and the chilled water outlet from the refrigeration unit. The refrigeration unit can maintain its current operating state, and the compressor's frequency converter regulates the evaporator's chilled water outlet temperature T. n The temperature should be within the range of 4–5℃. The flow control signal for this stage is:

[0139]

[0140] like Greater than However, when the flow rate does not exceed two-thirds of the rated flow rate of the return water pump of a single chiller unit, the unit's cooling capacity is slightly higher than the required amount of chilled water for production. Excess chilled water can be returned to the water tank for storage, and the unit can still maintain its current operating state. Adjusting the unit's inlet water pump flow rate is sufficient to ensure the unit's flow rate is not excessive. The flow control signal for this stage is:

[0141]

[0142] The cooling capacity in the water storage tank is insufficient to continue releasing cold water; additional refrigeration units need to be activated.

[0143] like Less than Furthermore, when the cooling flow rate exceeds the upper limit of the set chilled water stratified storage tank, the production load increases significantly. At this point, the sum of the return water flow rates of the chilled water storage tank and the operating refrigeration unit can no longer meet the demand side's production of chilled water, and an additional refrigeration unit must be started.

[0144] Or when the average temperature T between the middle and lower layers in the stratified water tank wt When the temperature is above 5℃, the cold storage in the water tank has been fully discharged and cannot meet the ice water temperature required for production. It is necessary to add a refrigeration unit in time to store cold for the water tank.

[0145] The control signals for this stage are:

[0146]

[0147] T wt ≥5

[0148] Once the cold storage capacity in the water tank is complete, the cooling phase can begin, and the refrigeration unit can be turned off.

[0149] like Greater than And when it exceeds two-thirds of the rated flow of the return water pump of a single refrigeration unit, and at this time the temperature T in the lower layer of the water tank... wt When the temperature is below 4℃, it can be assumed that the production load has dropped significantly and the water storage tank has been fully stored in cold water. One set of operating refrigeration units can be shut down to provide ice water by utilizing the cold storage in the water tank.

[0150] The control signals for this stage are:

[0151]

[0152] T wt <4

[0153] This invention effectively reduces energy consumption of the refrigeration system during peak load periods and improves energy efficiency during off-peak periods, thereby reducing the total electricity cost of system operation. Furthermore, the entire refrigeration system is more sensitive to changes in cooling demand load and flow rate. When cooling load surges, it can quickly release the cold storage capacity of the stratified refrigerant tank, improving response speed. Simultaneously, it improves the refrigerant supply flow control method on the demand side. In addition to real-time adjustments based on load changes, it incorporates a limitation on the supply flow rate based on the refrigerant return temperature after heat exchange on the demand side. By controlling the refrigerant return temperature—that is, the refrigerant return temperature of the refrigeration unit—within the upper limit of the evaporator's heat exchange capacity, the refrigeration unit achieves maximum operating energy efficiency. Without changing the refrigerant supply temperature and pressure on the demand side, it rationally adjusts the supply flow rate, improving the overall energy efficiency of the system.

[0154] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A demand-side response-based control method for a refrigeration system with a cold storage device, characterized in that, Includes the following steps: Obtain the pressure measurement value on the external circulation cryogenic refrigerant supply main pipeline (112) in the external circulation system (10). P end Temperature measurement value on the external circulation high-temperature refrigerant return main pipe (111) T back ; Set condition one, where condition one is the pressure measurement value. P end Within the upper and lower limits of the required liquid supply pressure of the external refrigerant circulation system (10), and the temperature measurement value T back Within the specified range; when condition one is met, maintain the operating status of the external circulation refrigerant pump group (120) of the current external refrigerant circulation system (10); Set condition two, where condition two is the pressure measurement value. P end Within the upper and lower limits of the required liquid supply pressure of the external refrigerant circulation system (10), and the temperature measurement value T back Not within the specified range; when condition two is met, if the temperature measurement value T back If the value exceeds the specified upper limit, one additional external circulation refrigerant pump will be activated; conversely, if the value is below the limit, one external circulation refrigerant pump will be deactivated. The number of operating external circulation refrigerant pumps will be adjusted until the operating status of the above parameters changes from condition two to condition one. Set condition three, where condition three is the pressure measurement value. P end The temperature is below the lower limit of the supply pressure requirement of the external refrigerant circulation system (10), but does not exceed the lower limit of the safety warning; if condition three is met, the temperature measurement value T back If the temperature exceeds the specified upper limit, an additional external circulation refrigerant pump will be activated; if the temperature measurement value... T back If the liquid supply pressure is below the required lower limit within the specified range, the external circulation refrigerant pump in operation will be controlled by frequency converter to maintain the liquid supply pressure at or above the required lower limit. Set condition four, where condition four is the pressure measurement value. P end The pressure is higher than the upper limit of the liquid supply pressure required by the external circulation system (10) for the refrigerant, but does not exceed the upper limit of the safety warning limit; If condition four is met, the external circulation refrigerant pump in operation will be controlled by frequency converter to maintain the liquid supply pressure not higher than the required upper limit. Set condition five, where condition five is the pressure measurement value. P end Exceeding the upper and lower limits of the safety warning line; When condition five is met, if the pressure measurement value P end If the pressure reading is below the lower safety warning limit, then add an external circulation refrigerant pump. P end If the value exceeds the safety warning limit, one external refrigerant pump will be switched off. Adjust the pressure measurement value using the steps described above. P end Within the upper and lower limits of the required liquid supply pressure of the external refrigerant circulation system (10), and the temperature measurement value T back Within the specified range, obtain the flow rate measurement value of the main external circulation cryogenic refrigerant supply line (112). qv end , Flow rate measurement of the high-temperature refrigerant return line on each refrigeration unit (20) in the internal circulation refrigeration system qv n Temperature measurement values ​​of the low-temperature refrigerant supply pipeline on each refrigeration unit (20) T n The average temperature measurements of the middle and lower layers of the refrigerant stratified storage tank (130) T wt ; Condition six is ​​set as the sum of the measured flow rates of the high-temperature refrigerant return lines on each currently operating refrigeration unit (20). Flow measurement value of the main supply line (112) for external circulation cryogenic refrigerant The difference is within the range of 1, and the average temperature measurement values ​​of the middle and lower layers of the refrigerant stratified storage tank (130) are... T wt The refrigerant supply is below the upper limit of the refrigerant supply requirement of the external refrigerant circulation system (10); when condition six is ​​met, the refrigeration unit (20) maintains the current number of operating units, adjusts the compressor speed or slide valve position of the operating refrigeration unit (20), and maintains the temperature measurement value of the low-temperature refrigerant supply pipeline. T n Not exceeding the production safety range; when the sum of the measured flow rates of the high-temperature refrigerant return lines on each operating refrigeration unit (20) is... Flow measurement value of the main supply line (112) for external circulation cryogenic refrigerant When the difference is positive, the refrigerant stratified storage tank (130) is in a cold storage state; while when the difference is negative, the refrigerant stratified storage tank (130) is in a cold release state. Condition seven is set as the sum of the measured flow rates of the high-temperature refrigerant return pipeline on each operating refrigeration unit (20). Flow measurement value of the main supply line (112) for external circulation cryogenic refrigerant The difference is within range two, or the average temperature measurement of the middle and lower layers of the refrigerant stratified storage tank (130). T wt The refrigerant supply is higher than the upper limit of the refrigerant supply requirements of the external circulation system (10); when condition seven is met, add a refrigeration unit (20) and adjust the compressor speed or slide valve position of the refrigeration unit (20) in operation until the operating state changes from condition seven to condition six. If it is not met, add another refrigeration unit (20) until condition six is ​​met; if the total cooling capacity of the refrigerant stratified storage tank (130) and the cooling capacity of the refrigeration unit (20) in operation cannot meet the load requirements of the external circulation system (10), or the refrigerant temperature in the refrigerant stratified storage tank (130) is higher than the upper limit of the refrigerant supply temperature, add a refrigeration unit (20) to increase the cooling capacity or switch the operating state of the refrigerant stratified storage tank (130) from cooling to cold storage. Setting condition eight, which is the sum of the measured flow rates of the high-temperature refrigerant return pipeline on each operating refrigeration unit (20). Flow measurement value of the main supply line (112) for external circulation cryogenic refrigerant The difference is within range three, and the average temperature measurement values ​​of the middle and lower layers of the refrigerant stratified storage tank (130) are... T wt If the refrigerant supply is below the lower limit of the refrigerant supply requirements of the external refrigerant circulation system (10), and one refrigeration unit (20) is turned off when condition eight is met, the compressor speed or slide valve position of the refrigeration unit (20) in operation is adjusted until the operating state changes from condition eight to condition six. If the condition is not met, another refrigeration unit (20) is turned off until condition six is ​​met. If the total cooling capacity of the refrigerant stratified storage tank (130) and the cooling capacity of the refrigeration unit (20) in operation exceed the load of the external refrigerant circulation system (10), and the refrigerant temperature in the refrigerant stratified storage tank (130) is lower than the lower limit of the supply temperature, then the refrigerant stratified storage tank (130) has been fully stored and the operating state is switched from the storage state to the release state. The sum of the flow measurements of the high-temperature refrigerant return line on each currently operating refrigeration unit (20) Flow measurement value of the main supply line (112) for external circulation cryogenic refrigerant The range of the difference is divided as follows: Range 1: Lower limit When the cooling capacity of the refrigerant stratified storage tank (130) is the same as that of two-thirds of the cooling capacity of the refrigeration unit (20), the flow rate at the outlet of the refrigerant stratified storage tank (130) is negative; upper limit The rated flow rate of the water entering two-thirds of the refrigeration units (20) is a positive number; when the difference is negative, the refrigerant stratification storage tank (130) is in a cooling release state, and when the difference is positive, the refrigerant stratification storage tank (130) is in a cooling storage state, as expressed below: In the formula, Q 制冷机组 This refers to the rated cooling capacity of a single refrigeration unit. T The maximum temperature difference between the supply and return refrigerant of the refrigeration unit; ρ The density of the refrigerant; c p The specific heat capacity of the refrigerant. N The number of operating refrigeration units. The rated flow rate of a single external circulation refrigerant pump in the external refrigerant circulation system (10); Scope 2: The sum of the measured flow rates of the high-temperature refrigerant return lines on each currently operating refrigeration unit (20). The flow rate is less than the measured value of the main supply line (112) for the external circulation cryogenic refrigerant. When the absolute value of the difference is greater than the cooling capacity of the refrigerant stratified storage tank (130) and two-thirds of the cooling capacity of the refrigeration unit (20), the flow rate at the outlet of the refrigerant stratified storage tank (130) is expressed as follows: Scope 3: The sum of the measured flow rates of the high-temperature refrigerant return lines on each currently operating refrigeration unit (20). The flow rate is greater than the measured value of the main supply line (112) for the external circulation cryogenic refrigerant. And the absolute value of the difference is greater than the rated flow rate of the inlet water of two-thirds of the chiller units (20), as expressed below: The refrigeration system with a cold storage device includes an external refrigerant circulation system (10), an internal refrigerant circulation system, a cold storage device, and a refrigeration unit (20). The refrigerant external circulation system (10) includes an external circulation refrigerant pump group (120), and an external circulation low-temperature refrigerant supply main pipeline (112) and an external circulation high-temperature refrigerant return main pipeline (111) connected to the cooling unit (110); the external circulation refrigerant pump group (120) is connected to the cooling unit (110) through the external circulation low-temperature refrigerant supply main pipeline (112). The refrigerant internal circulation system includes a high-temperature refrigerant return line and a low-temperature refrigerant supply line connected to the refrigeration unit (20), and a low-temperature refrigerant main supply line (270) connected to the low-temperature refrigerant supply line. The high-temperature refrigerant return line is connected to the internal circulation refrigerant pump. The internal circulation refrigerant pump is connected to the external circulation high-temperature refrigerant return line (111) and the first inlet and outlet lines of the cold storage device through the refrigeration unit refrigerant return three-way valve. The low-temperature refrigerant main supply line (270) is connected to the external circulation refrigerant pump group (120) and the second inlet and outlet lines of the cold storage device through the refrigerant supply three-way valve (140). The refrigerant flow direction is reversed depending on whether the cold storage device is in a cold storage state or a cold release state. The external circulation refrigerant pump set (120) is composed of one or more refrigerant variable frequency pumps connected in parallel; The refrigeration unit (20) is composed of one or more vapor compression refrigeration units connected in parallel. Each refrigeration unit (20) is connected to a high-temperature refrigerant return pipeline and a low-temperature refrigerant supply pipeline. Each high-temperature refrigerant return pipeline is equipped with an internal circulation refrigerant pump and a refrigeration unit refrigerant return three-way valve.

2. The control method for a refrigeration system with a cold storage device based on demand-side response according to claim 1, characterized in that: The aforementioned cold storage device is a layered refrigerant storage tank (130), with the first inlet and outlet pipes located at the top and the second inlet and outlet pipes located at the bottom; When the refrigerant stratified storage tank (130) is in the cold storage state, the first inlet and outlet are the refrigerant outlets of the refrigerant stratified storage tank (130), the second inlet and outlet are the refrigerant inlets of the refrigerant stratified storage tank (130), and the flow direction of the refrigerant in the refrigerant stratified storage tank (130) is from bottom to top. When the refrigerant stratified storage tank (130) is in the cooling state, the first inlet and outlet are the refrigerant inlet of the refrigerant stratified storage tank (130), and the second inlet and outlet are the refrigerant outlet of the refrigerant stratified storage tank (130). The flow direction of the refrigerant in the refrigerant stratified storage tank (130) is from top to bottom.

3. The control method for a refrigeration system with a cold storage device based on demand-side response according to claim 2, characterized in that: A temperature sensor, a flow sensor, and a pressure sensor are installed on the external circulation low-temperature refrigerant supply main pipeline (112); a temperature sensor is installed on the external circulation high-temperature refrigerant return main pipeline (111). The refrigerant stratified storage tank (130) is equipped with a liquid level sensor to detect changes in the liquid level inside the tank, and temperature sensors are installed in the upper, middle and lower layers inside the refrigerant stratified storage tank (130).

4. The control method for a refrigeration system with a cold storage device based on demand-side response according to claim 1, characterized in that: The refrigeration unit (20) includes an evaporator (210), a throttle valve (220), a compressor (230), a condenser (240), and a cooling tower (250); the cooling tower (250) is connected to the condenser (240), and the condenser (240) and the evaporator (210) are connected through a refrigerant pipeline to form a circulating refrigeration system; the throttle valve (220) and the compressor (230) are located on the refrigerant pipeline; the high-temperature refrigerant return pipeline and the low-temperature refrigerant supply pipeline are connected to the evaporator (210).

5. The demand-side response-based control method for a refrigeration system with a cold storage device according to claim 4, characterized in that: A temperature sensor and a flow sensor are installed at the inlet of the evaporator (210) connected to the high-temperature refrigerant return pipeline. A temperature sensor is installed at the outlet of the evaporator (210) connected to the low-temperature refrigerant supply pipeline; The compressor (230) is equipped with a speed sensor (231) and a slide valve position sensor (232).

6. The control method based on demand-side response for a refrigeration system with a cold storage device according to claim 5, characterized in that: The cooling capacity is adjusted by adjusting the number of operating refrigeration units (20) and the operating speed or slide valve position of the compressor (230) in the operating refrigeration unit (20), so as to keep the water temperature and water supply pressure of the external circulation low temperature refrigerant supply main pipeline (112) from not exceeding the safe operating range.

7. The demand-side response-based control method for a refrigeration system with a cold storage device according to claim 1, characterized in that, Temperature measurement value on the external circulation high-temperature refrigerant return main pipe (111) T back Within the specified range, the temperature measurement value on the external circulation high-temperature refrigerant return main pipeline (111) was determined experimentally: T back upper limit T back,UL To ensure that the refrigerant supply temperature of the refrigeration unit (20) is equal to the upper limit of the supply temperature required by the external refrigerant circulation system (10), the refrigerant return temperature of the refrigeration unit (20) is the refrigerant inlet temperature when the evaporator (210) in the refrigeration unit (20) reaches the upper limit of heat exchange; the temperature measurement value on the external circulation high-temperature refrigerant return main pipeline (111) T back lower limit T back,DL To ensure that the compressor (230) in the refrigeration unit (20) operates at 20% of its rated load.

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