Method and system for automatically adding or reducing a refrigeration host of a central air conditioning system

Abstract

This invention discloses a control method and system for automatically increasing or decreasing the number of chiller units in a central air conditioning system, relating to the field of air conditioning energy conservation. The method includes the following steps: In the central air conditioning system, the differential pressure value at the inlet and outlet of the chilled water of each chiller unit is monitored in real time using a differential pressure sensor; when one or more user air conditioning terminals are turned off or on, the opening degree of the electric bypass valve on the supply and return water mains is controlled based on the change between the differential pressure value and the rated differential pressure; when the actual detected differential pressure value is ≤ a first differential pressure set threshold detected when the electric bypass valve opening is at its maximum, or ≥ a second differential pressure set threshold detected when the electric bypass valve opening is at its minimum, the number of chiller units turned on is controlled to increase or decrease. Using this solution, the measured differential pressure and temperature difference between the inlet and outlet of the chilled water of the chiller unit itself can be used as control quantities to directly control the increase or decrease in the number of chiller units turned on, thereby achieving energy-saving control of the central air conditioning system.

Description

Technical Field

[0001] This invention relates to the field of air conditioning energy saving, specifically to a control method and system for automatically increasing or decreasing the refrigeration unit of a central air conditioning system. Background Technology

[0002] In central air conditioning systems, refrigeration units are the main energy-consuming equipment. Achieving energy-efficient cooling by automatically adjusting the number of refrigeration units in operation based on user air conditioning load is of great significance for the energy conservation of central air conditioning systems.

[0003] In existing technologies, numerous solutions have been provided for achieving energy conservation in air conditioning systems. For example, patent CN119222875A, entitled "A Load Distribution Control Method, System, and Equipment for a Parallel Refrigeration Unit System," addresses the problem of finding the optimal number of operating refrigeration unit nodes corresponding to the best energy efficiency value in a parallel system. Its control method includes: obtaining a three-dimensional performance array table of the inlet and outlet temperatures, load rate, and energy efficiency value of each refrigeration unit; executing an optimal load adjustment strategy: obtaining the real-time cooling capacity of each refrigeration unit and determining the total real-time cooling capacity of the system; determining the range of the number of refrigeration units to be operated based on the rated and minimum cooling capacities of the units; determining the energy efficiency values ​​of each unit in the table corresponding to each number of units within the range and calculating the total energy efficiency value of each corresponding number of units; obtaining the number of units corresponding to the maximum total energy efficiency value as the optimal number of operating units; and adjusting the load based on the current number of operating units and the optimal number of operating units. This method enables the system to meet cooling requirements while achieving optimal energy efficiency. Although the document discloses the ability to control the number of chiller units, it actually measures the inlet and outlet temperatures of the cooling medium, not the chilled water inlet and outlet temperatures. Furthermore, it requires consideration of the unit load and energy efficiency values ​​to determine the number of chiller units to be increased or decreased. The document has too many parameters to measure, making the control process more complex.

[0004] For example, in existing literature CN105571089A, an invention patent entitled "An Energy-Saving Intelligent Ecological Central Air Conditioning Device," its structure involves connecting the output of a central air conditioning operating parameter acquisition device to the input of a controller. The output of the controller is connected to the input of a frequency converter, and the output of the frequency converter is connected to the central air conditioning unit. The central air conditioning unit includes a refrigeration unit, cooling water pipes and chilled water pipes connected to the refrigeration unit, a cooling water circulation pump connected to the cooling water pipes, a chilled water circulation pump connected to the chilled water pipes, and a cooling tower fan. The central air conditioning operating parameter acquisition device includes a flow meter, a differential pressure sensor, and a temperature sensor. The frequency converter includes the variable frequency output terminals of the cooling water circulation pump, the chilled water circulation pump, and the cooling tower fan. The advantages of this invention are: it uses temperature compensation and on-demand cooling to output cooling capacity, allowing the central air conditioning unit to operate at its optimal state, thus achieving energy savings; furthermore, it introduces the concept of smart homes, realizing intelligent operation. Although the document discloses the installation of a second differential pressure sensor at the inlet and outlet of the chilled water pipe, its application of differential pressure is for use in conjunction with parameters such as temperature and flow rate. It actually controls the operating power of the chiller unit to achieve energy-saving function through frequency modulation. Its control path is completely different from this solution. Furthermore, due to the long-term fluctuation of chilled water flow rate, its flow rate value cannot be accurately measured. Since both the cooling water and chilled water of the chiller unit are equipped with flow switches, if the flow rate is too low, the flow switches cannot be opened, causing the unit to shut down and enter a self-protection state. Therefore, the flow rates of the chilled water pump and cooling water need to be controlled at the rated flow rate to achieve this.

[0005] For example, in existing literature, CN119353761A, entitled "Invention Patent on Control Method, Device, Equipment and Medium for Central Air Conditioning Chilled Water System," describes a method that includes: acquiring a set differential pressure value of the central air conditioning chilled water system; adjusting the set differential pressure value within a preset period to obtain an adjusted set differential pressure value; and controlling the chilled water pump of the central air conditioning chilled water system based on the adjusted set differential pressure value to regulate the chilled water flow rate. This application can reduce the energy consumption of the central air conditioning chilled water system. However, while this literature discloses the ability to acquire the differential pressure value of the central air conditioning chilled water system, it actually measures the differential pressure between the chilled water supply and return mains. The measuring points also have additional local resistances such as valves, Y-filters, short pipe bends, reducers, and flanges. The measured differential pressure is actually greater than the differential pressure of the chiller itself. Furthermore, during flow rate changes, accurate measurements cannot be found on the supply and return mains; only power can be adjusted, not the flow rate can be accurately matched to control the chiller's operation.

[0006] In summary, there is an urgent need for a simpler and more precise control method to automatically increase or decrease the number of refrigeration units that are turned on, in order to achieve the goal of energy-saving control. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention aims to provide a control method and system for automatically increasing or decreasing the number of refrigeration units in a central air conditioning system. By using this solution, the measured pressure difference between the inlet and outlet of the chilled water in the refrigeration unit itself can be used as a control quantity to directly control the increase or decrease in the number of refrigeration units that are turned on, thereby achieving energy-saving control of the central air conditioning system.

[0008] This invention is achieved through the following technical solution:

[0009] The control method for automatically increasing or decreasing the refrigeration unit temperature in a central air conditioning system includes the following steps:

[0010] S1: In a central air conditioning system, the differential pressure value between the inlet and outlet of the chilled water of each chiller unit is monitored in real time based on differential pressure sensors; and the differential pressure between the inlet and outlet of the chilled water of the chiller unit at the rated flow rate is taken as the rated differential pressure value.

[0011] S2: When one or more user air conditioning terminals are turned off or on, the opening of the electric bypass valve on the supply and return water main is controlled based on the change between the differential pressure value and the rated differential pressure to maintain the rated flow of the refrigeration unit.

[0012] S3: When the actual detected differential pressure value is less than or equal to the first differential pressure setting threshold detected when the electric bypass valve is at its maximum opening, or greater than or equal to the second differential pressure setting threshold detected when the electric bypass valve is at its minimum opening, control the increase or decrease of the number of refrigeration units that are turned on.

[0013] In a further optimization, step S2 also includes the following steps:

[0014] The first operating condition: When one or more user air conditioning terminals are turned off, the pressure difference between the inlet and outlet of the chilled water of the chiller decreases. Based on the decrease in pressure difference, the opening of the electric bypass valve on the main supply and return water pipes is gradually increased to bypass part of the chilled water to the chiller until the flow rate of the chiller equals the rated flow rate, so that the pressure difference change returns to the rated pressure difference.

[0015] The second operating condition: When one or more user air conditioning terminals are turned on, the pressure difference between the inlet and outlet of the chilled water of the chiller unit increases. Based on the increased pressure difference, the opening of the electric bypass valve on the main supply and return water pipes is gradually reduced to decrease the bypass flow of chilled water until the flow rate of the chiller unit equals the rated flow rate, so that the pressure difference change returns to the rated pressure difference.

[0016] In a further optimization, step S2 also includes a step of controlling the refrigeration unit to reduce its operating speed using a temperature difference controller:

[0017] In the process of controlling the opening of the electric bypass valve on the main supply and return water pipes based on the change between the differential pressure value and the rated differential pressure to maintain the rated flow of the chiller, the temperature difference value of the inlet and outlet of the chilled water of each chiller can also be monitored in real time by the temperature difference sensor.

[0018] As users reduce their air conditioning load, the temperature difference between the inlet and outlet of the chilled water in the air conditioning unit decreases accordingly. When the actual detected temperature difference value is less than or equal to the first temperature setting threshold, the number of refrigeration units controlled by the temperature difference controller to be turned on is reduced by one.

[0019] In a further optimization, step S2 also includes a step of controlling the refrigeration unit's operating temperature by controlling the return water temperature of the chilled water return main pipe:

[0020] In the process of controlling the opening of the electric bypass valve on the main supply and return water pipes based on the change between the differential pressure value and the rated differential pressure to maintain the rated flow of the chiller, the return water temperature of the chilled water in each chiller can also be monitored in real time by the return water temperature sensor.

[0021] As the user's air conditioning load increases, the return water temperature of the chilled water in the air conditioning unit rises accordingly. When the actual detected return water temperature value is greater than or equal to the second temperature setting threshold, the temperature difference controller will control an additional refrigeration unit to be turned on. The second temperature setting threshold is located below the air dew point temperature.

[0022] In a further optimization, the bypass flow rate of the supply and return water main is the same as the rated flow rate of the chiller.

[0023] Further optimization involves setting the first pressure threshold as the differential pressure detected by the differential pressure sensor when the electric bypass valve is fully open; and setting the second pressure threshold as the differential pressure detected by the differential pressure sensor when the electric bypass valve is fully closed.

[0024] In a further optimization, step S3 also includes the following steps:

[0025] The refrigeration unit is controlled to reduce its operating rate by a differential pressure controller: as one or more user air conditioning terminals continue to shut down, when the change in differential pressure reaches the first pressure setting threshold, the electric bypass valve has reached its maximum opening, i.e., the rated flow rate has been reached.

[0026] Since the bypass flow cannot be increased, the flow through the refrigeration unit will continuously decrease. Therefore, at this time, the number of refrigeration units controlled by the differential pressure controller to be turned on is reduced by one, so that the flow of the refrigeration unit can be restored to the rated flow, and the change in differential pressure value can be restored to the rated differential pressure value.

[0027] In a further optimization, step S3 also includes the following steps:

[0028] The refrigeration unit is controlled by a differential pressure controller to add power: as one or more user air conditioning terminals continue to be turned on, when the change in differential pressure reaches the second pressure setting threshold, the electric bypass valve is completely closed and cannot bypass the flow.

[0029] Since the flow cannot be bypassed, the flow through the refrigeration unit will continue to increase. Therefore, at this time, an additional refrigeration unit is turned on by the differential pressure controller to restore the flow of the refrigeration unit to the rated flow and restore the differential pressure value change to the rated differential pressure value.

[0030] Further solutions:

[0031] This invention also provides a control system for realizing the automatic addition and subtraction of the refrigeration unit in a central air conditioning system, comprising:

[0032] A differential pressure sensor is used to monitor the differential pressure value between the inlet and outlet of the chilled water in each chiller unit;

[0033] A differential pressure controller is used to receive the detection signal from the differential pressure sensor and, based on the magnitude of the differential pressure value, control the opening degree of the electric bypass valve on the main supply and return water pipes, as well as control the increase or decrease of the number of refrigeration units that are turned on.

[0034] A temperature difference sensor is used to monitor the temperature difference between the inlet and outlet of the chilled water in each chiller unit.

[0035] A temperature difference controller is used to receive the detection signal from the temperature difference sensor and control the refrigeration unit to reduce its operating speed based on the temperature difference value and the value between the temperature difference value and a first temperature set threshold.

[0036] A return water temperature sensor is used to monitor the return water temperature of the chilled water return main pipe;

[0037] A return water temperature controller is used to receive the detection signal from the return water temperature sensor and set a threshold value between the return water temperature and the second temperature to control the operation of the refrigeration unit.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] 1. This invention provides a control method and system for automatically increasing or decreasing the number of refrigeration units in a central air conditioning system. By using this solution, the measured pressure difference between the inlet and outlet of the chilled water in the refrigeration unit itself can be used as a control quantity to directly control the increase or decrease in the number of refrigeration units that are turned on, thereby achieving energy-saving control of the central air conditioning system.

[0040] 2. This invention provides a control method and system for automatically increasing or decreasing the flow rate of the chiller unit in a central air conditioning system. Using this method, the opening of the electric bypass valve on the main supply and return water pipes is directly controlled by the pressure difference between the inlet and outlet of the chilled water in the chiller unit itself, thereby changing the return flow rate to maintain the chiller unit operating at the rated flow rate and ensuring the stability of the chiller unit's operation.

[0041] 3. This invention provides a control method and system for automatically increasing or decreasing the flow rate of a central air conditioning system's chiller unit. Using this method, while maintaining the chiller unit's operation at its rated flow rate by controlling the opening of the electric bypass valve through a differential pressure controller, the system can also directly control the chiller unit's flow rate reduction by using the measured temperature difference between the chilled water inlet and outlet as a control quantity; and it can also directly control the chiller unit's flow rate increase by using the measured temperature of the chilled water return main pipe as a control quantity. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0043] Figure 1 The central air conditioning system control diagram provided by the present invention;

[0044] Figure 2 Provided by the present invention Figure 1 Enlarged view of point A (sensor placement location);

[0045] Figure 3 The automatic reduction control flowchart provided by this invention;

[0046] Figure 4 The automatic machining control flowchart provided by this invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0048] Example 1: This Example 1 provides a control method for automatically increasing or decreasing the refrigeration unit of a central air conditioning system, such as... Figures 3-4 As shown, a process is provided that uses differential pressure detection and control by an adder / subtractor.

[0049] To ensure the safe and stable operation of the chiller unit, it must operate at a constant flow rate, i.e., the rated flow rate of the chilled water. When the chiller unit operates at its rated flow rate, the pressure drop in the evaporator is the pressure difference between the inlet and outlet of the chilled water. Therefore, the pressure difference between the inlet and outlet of the chilled water in this design, detected by the differential pressure sensor, is actually the pressure difference between the inlet and outlet of the evaporator.

[0050] In this solution, the chilled water flow rate, pressure difference, and temperature difference are the same for each of the several chiller units. Therefore, the pressure difference detected on one chiller unit can be reflected as the same pressure difference for each chiller unit. In this solution, a pressure difference sensor is installed on each chiller unit to prevent the pressure difference sensor from detecting a chiller unit that has not yet been turned on.

[0051] This embodiment provides a solution for automatically adjusting the number of refrigeration units in operation based on the user's air conditioning load. It uses a differential pressure sensor as the detection source and a differential pressure controller as the control terminal, aiming to maintain stable operation of the refrigeration units at rated flow. Details are as follows:

[0052] (1) Automatic reduction of refrigeration unit:

[0053] Because the number of user-end devices in the air conditioning system changes constantly, the system's circulating water volume also changes continuously. Therefore, it is difficult to keep the chilled water circulation volume of the chiller unit constant.

[0054] In order for the chiller to operate at the rated flow rate, an electric differential pressure bypass valve is installed on the main supply and return water pipes of the chilled water in the system. At the same time, a differential pressure sensor is installed at the inlet and outlet of the chilled water of each chiller unit. The opening degree of the electric differential pressure bypass valve is controlled by the differential pressure between the inlet and outlet of the chilled water of the chiller unit.

[0055] like Figure 3 As shown, when the user's air conditioning terminal is turned off, the system resistance will increase, the chilled water flow will decrease, and the flow rate of chilled water through the chiller unit will be less than the rated flow rate of the unit. Consequently, the pressure difference between the chilled water inlet and outlet of the unit will decrease relative to the rated pressure difference (according to the formula P=S*G). 2 P: Pressure difference between inlet and outlet of the chiller unit; S: Resistance number; G: Chilled water flow rate. At this time, the electric bypass valve is opened by the pressure difference between inlet and outlet of the chilled water of the chiller unit, so that a portion of the chilled water is bypassed to the chiller unit to supplement the chiller unit until the flow rate of the chiller unit is equal to the rated flow rate, thereby maintaining the chiller unit to operate stably at the rated flow rate. At this time, the pressure difference between inlet and outlet of the chiller unit is the pressure difference when the unit is at the rated flow rate.

[0056] As the number of user terminals continuously decreases, the system resistance continuously increases. When the electric bypass valve opens to its maximum degree, the flow rate through the chiller will continuously decrease, and the pressure difference between the chilled water inlet and outlet of the chiller will also continuously decrease. When the difference between the sum of the flow rates through all chillers and the sum of the rated flow rates of the chillers equals the rated flow rate of one chiller, that is, when the flow rate bypassed by the electric bypass valve is the rated flow rate of the chiller, it means that one chiller can be reduced from operation at the user terminal. At this time, the pressure difference between the chilled water inlet and outlet of the chiller is the control pressure difference for stopping the chiller, which is the preset first pressure threshold. When the pressure difference reaches the first pressure threshold, the chiller can be reduced to restore the rated flow rate of each chiller, and the pressure difference is reset.

[0057] When the number of user terminals continues to decrease, the differential pressure controller can repeat the above steps, repeatedly controlling the opening of the electric bypass valve and the reduction in the number of refrigeration units that are turned on, thus achieving fully automated operation.

[0058] In the above scheme, the pressure difference can be used to control the automatic reduction of one refrigeration unit in operation. Specifically, when setting the pressure difference threshold, the inlet and outlet pressure difference of each refrigeration unit can be accurately determined because the flow rate of each unit can be precisely calculated. For example, when three units are running simultaneously, each unit has a rated flow rate of G, and the total rated flow rate of the three units is 3G. When the electric bypass valve bypasses the rated flow rate G of one refrigeration unit, the opening of the electric bypass valve is at its maximum, meaning the bypass flow rate of the supply and return water mains on the electric bypass valve is the same as the rated flow rate of a single refrigeration unit. Since the electric bypass valve has no bypass capacity, this will cause the flow rate of each unit to decrease by one-third, that is, the flow rate of each unit is 2 / 3G. According to the formula P=S*G 2 This allows for the precise calculation of the pressure difference P between the inlet and outlet of the chilled water unit during 2 / 3G operation. Consequently, it enables the accurate determination of the pressure difference required to stop the operation of a single unit, i.e., the first pressure setting threshold, which can be preset in advance to achieve automatic reduction of the chiller unit's operation.

[0059] (2) Automatic addition of refrigeration unit:

[0060] Similar to the automatic reduction method of the refrigeration unit controlled by differential pressure.

[0061] like Figure 4 As shown, when the number of user air conditioning terminals turned on increases, the resistance of the chilled water system decreases, the chilled water flow increases, and the pressure difference between the inlet and outlet of the chilled water of the chiller unit will increase. At this time, the opening degree of the electric bypass valve can be reduced by the differential pressure controller.

[0062] As the number of user air conditioning terminals increases and the electric bypass valve is completely closed, the system resistance decreases, the flow rate increases, and the pressure difference between the inlet and outlet of the chilled water of the chiller unit will continue to increase. When the total chilled water flow of all operating units is greater than or equal to the rated flow of one unit, one chiller unit will be started through the differential pressure controller, and the other operating chillers will resume operation at their rated flow rates.

[0063] For example, two chiller units are running simultaneously, with the electric bypass valve completely closed, yet the number of user air conditioning terminals still increasing. Assuming each chiller unit has a rated flow rate of G, when each chiller unit's actual operating flow rate is 1.5G, the chilled water circulation flow rate is 3G, which is one G more than the sum of the two chiller units' rated flow rates of 2G. Using the formula P=S*G², the inlet and outlet pressure difference of the chilled water when the chiller unit is operating at 1.5 times its rated flow rate can be calculated. This allows for the pre-calculation of the second pressure setting threshold, which can then be used to control the start of one chiller unit, thus achieving automatic multi-unit operation.

[0064] Example 2: Based on Example 1, Example 2 also provides a process for temperature difference detection and reduction control.

[0065] In this solution, the chilled water flow rate, pressure difference, and temperature difference are the same for each of the several chiller units. Therefore, the temperature difference detected on one chiller unit can be reflected as the same temperature difference for each chiller unit. In this solution, a temperature difference sensor is installed on each chiller unit to prevent the temperature difference sensor from detecting a chiller unit that has not yet been turned on.

[0066] To achieve automatic reduction of the number of refrigeration units in operation based on the user's air conditioning load, a solution is mainly provided that uses a temperature difference sensor as the detection source and a temperature difference controller as the control terminal, thereby controlling the reduction of units based on the temperature difference. Figure 3 As shown. Specifically:

[0067] The temperature difference controller automatically reduces the operating speed of the refrigeration unit.

[0068] Because the chilled water system is equipped with an electric differential pressure bypass valve between the supply and return water mains, and the differential pressure controller can control the valve opening of the electric bypass valve on the supply and return water mains according to the differential pressure value between the chilled water inlet and outlet of the chiller, the chiller can be kept running at its rated flow rate. Provided that the chiller can maintain its rated flow rate, the temperature difference controller can be used to control the chiller to reduce its operating speed based on a first temperature threshold.

[0069] In actual operation: such as Figure 3As shown, during the operation of the chiller unit at its rated flow rate, its cooling capacity and temperature difference are directly proportional. When multiple chillers are running, the cooling capacity of each unit can be accurately calculated. When the sum of the rated cooling capacity of all operating units minus the sum of the actual cooling capacity of the operating units is greater than or equal to the rated cooling capacity of one chiller unit, the operation of one chiller unit can be stopped. At this time, the temperature difference between the inlet and outlet of the chilled water in the chiller unit is the control temperature difference for stopping the chiller unit, which is the pre-set first temperature threshold.

[0070] As users reduce their air conditioning load, the temperature difference between the inlet and outlet of the chilled water in the air conditioning unit decreases accordingly. When the temperature difference reaches the first set temperature threshold, the unit can be controlled to reduce its operating temperature to restore cooling capacity. The factors that reduce users' air conditioning load are not only related to the shutdown of the user terminals, but also to outdoor weather conditions. For example, when the outdoor temperature is not high, the air conditioning usage will also decrease.

[0071] Regarding the first temperature setting threshold: When multiple chiller units are running, the cooling capacity of each unit can be accurately calculated. For example, if three chiller units are running simultaneously, each with a rated flow rate of G and a rated cooling capacity of Q, the formula Q = G * CP * Δt is used. CP represents the specific heat of water, and Δt represents the temperature difference between the chilled water inlet and outlet. Δt = Q / G * CP. In actual operation, Δt' = Q' / G * CP. When Q' = 2 / 3Q, Δt' = 2 / 3 * Δt. At this point, the temperature has reached the limit requiring a reduction in the number of chiller units. Δt is the temperature difference at rated flow rate and rated cooling capacity, so it is a known value. Therefore, the actual operating temperature difference Δt' can be accurately calculated in advance, thus obtaining the first temperature setting threshold. When the actual detected temperature difference during operation is less than or equal to the first temperature setting threshold, the operating chiller unit can be reduced by one unit using a temperature difference controller based on the chilled water inlet and outlet temperature difference of the chiller unit.

[0072] Example 3: Based on Example 2, Example 3 further provides a chilled water return temperature control method, so that the return water temperature controller can control the automatic addition of chiller units, such as... Figure 4 As shown.

[0073] like Figure 3As shown, chilled water in an air conditioning system serves not only a cooling function but also a dehumidifying function. Therefore, the temperature of the chilled water must be lower than the dew point temperature of the processed air. To ensure the cooling and dehumidification equipment (such as surface coolers) operates at maximum efficiency, i.e., the entire system is in a fully humid condition, the return water temperature of the chilled water must also be lower than the dew point temperature of the processed air. Therefore, this solution installs a return water temperature sensor on the return water main or in the water collector. As the air conditioning load increases, the chilled water return temperature rises accordingly. When the return water temperature approaches the dew point temperature of the processed air, i.e., when the second temperature set threshold is reached, a refrigeration unit can be started via the return water temperature controller. For example, if the dew point temperature of the air processed by the air conditioning terminal surface cooler is 15℃, and the chilled water return temperature is 14℃, a refrigeration unit can be started via the return water temperature controller, thus automatically increasing the number of refrigeration units based on the chilled water return temperature.

[0074] In addition, for centrifugal chillers operating in single-unit mode, since the chilled water in the unit maintains a constant flow rate, the temperature difference between the inlet and outlet of the chilled water in the chiller unit can be used to provide an early warning of the centrifugal chiller entering the surge zone, thus preventing the unit from experiencing surge.

[0075] Example 4: Based on the above examples, Example 4 further provides a control system for realizing the automatic addition and subtraction of the refrigeration unit in a central air conditioning system, such as... Figure 1 and Figure 2 , Figure 1 The control diagram of the central air conditioning system provided by this invention shows the location and method of setting each sensor and controller as follows: Figure 1 and Figure 2 As shown. Due to Figure 1 The sensors and controllers on chiller unit 1, chiller unit 2, and chiller unit 3 are all installed in the same way, therefore... Figure 2 Simply display the control circuit diagram for chiller unit 1. Among them, Figure 1 and Figure 2 The meanings of each character in the table are shown below:

[0076]

[0077] Specifically, the main components in the control system include:

[0078] A differential pressure sensor is used to monitor the differential pressure value between the inlet and outlet of the chilled water in each chiller unit;

[0079] A differential pressure controller is used to receive the detection signal from the differential pressure sensor and, based on the magnitude of the differential pressure value, control the opening degree of the electric bypass valve on the main supply and return water pipes, as well as control the increase or decrease of the number of refrigeration units that are turned on.

[0080] A temperature difference sensor is used to monitor the temperature difference between the inlet and outlet of the chilled water in each chiller unit.

[0081] A temperature difference controller is used to receive the detection signal from the temperature difference sensor and control the refrigeration unit to reduce its operating speed based on the temperature difference value and the value between the temperature difference value and a first temperature set threshold.

[0082] A return water temperature sensor is used to monitor the temperature of the chilled water return main pipe.

[0083] A return water temperature controller is used to receive the detection signal from the return water temperature sensor and set a threshold value between the return water temperature and the second temperature to control the operation of the refrigeration unit.

[0084] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for automatically increasing or decreasing the refrigeration unit temperature in a central air conditioning system, characterized in that: Includes the following steps: S1: In a central air conditioning system, the differential pressure value between the inlet and outlet of the chilled water of each chiller unit is monitored in real time based on differential pressure sensors; and the differential pressure between the inlet and outlet of the chilled water of the chiller unit at the rated flow rate is taken as the rated differential pressure value. S2: When one or more user air conditioning terminals are turned off or on, the opening of the electric bypass valve on the supply and return water main is controlled based on the change between the differential pressure value and the rated differential pressure to maintain the rated flow of the refrigeration unit. S3: When the actual detected differential pressure value is less than or equal to the first differential pressure setting threshold detected when the electric bypass valve is at its maximum opening, or greater than or equal to the second differential pressure setting threshold detected when the electric bypass valve is at its minimum opening, control the increase or decrease of the number of refrigeration units that are turned on.

2. The control method for automatically increasing or decreasing the refrigeration unit of a central air conditioning system according to claim 1, characterized in that, Step S2 further includes the following steps: The first operating condition: When one or more user air conditioning terminals are turned off, the pressure difference between the inlet and outlet of the chilled water of the chiller unit decreases. Based on the decrease in pressure difference, the opening of the electric bypass valve on the main supply and return water pipes is gradually increased to bypass part of the chilled water to the chiller unit until the flow rate of the chiller unit is equal to the rated flow rate, so that the pressure difference change is restored to the rated pressure difference.

3. The control method for automatically increasing or decreasing the refrigeration unit of a central air conditioning system according to claim 2, characterized in that, Step S2 further includes the following steps: The second operating condition: When one or more user air conditioning terminals are turned on, the pressure difference between the inlet and outlet of the chilled water of the chiller unit increases. Based on the increased pressure difference, the opening of the electric bypass valve on the main supply and return water pipes is gradually reduced to decrease the bypass flow of chilled water until the flow rate of the chiller unit equals the rated flow rate, so that the pressure difference change returns to the rated pressure difference.

4. The control method for automatically increasing or decreasing the refrigeration unit of a central air conditioning system according to claim 1, characterized in that, Step S2 further includes a step of controlling the refrigeration unit to reduce its operating speed using a temperature difference controller: In the process of controlling the opening of the electric bypass valve on the main supply and return water pipes based on the change between the differential pressure value and the rated differential pressure to maintain the rated flow of the chiller, the temperature difference value of the inlet and outlet of the chilled water of each chiller can also be monitored in real time by the temperature difference sensor. As users reduce their air conditioning load, the temperature difference between the inlet and outlet of the chilled water in the air conditioning unit decreases accordingly. When the actual detected temperature difference value is less than or equal to the first temperature setting threshold, the number of refrigeration units controlled by the temperature difference controller to be turned on is reduced by one.

5. The control method for automatically increasing or decreasing the refrigeration unit of a central air conditioning system according to claim 4, characterized in that, Step S2 further includes a step of controlling the refrigeration unit by controlling the return water temperature of the chilled water return main pipe: In the process of controlling the opening of the electric bypass valve on the main supply and return water pipes based on the change between the differential pressure value and the rated differential pressure to maintain the rated flow of the chiller, the return water temperature of the chilled water in each chiller can also be monitored in real time by the return water temperature sensor. As the user's air conditioning load increases, the return water temperature of the chilled water in the air conditioning unit rises accordingly. When the actual detected return water temperature value is greater than or equal to the second temperature setting threshold, the return water temperature controller will control an additional refrigeration unit to be turned on. The second temperature setting threshold is located below the air dew point temperature.

6. The control method for automatically increasing or decreasing the refrigeration unit of a central air conditioning system according to claim 1, characterized in that, The bypass flow rate of the supply and return water main is the same as the rated flow rate of the chiller.

7. The control method for automatically increasing or decreasing the refrigeration unit of a central air conditioning system according to claim 6, characterized in that, The first pressure setting threshold is the differential pressure detected by the differential pressure sensor when the electric bypass valve is fully open; the second pressure setting threshold is the differential pressure detected by the differential pressure sensor when the electric bypass valve is fully closed.

8. The control method for automatically increasing or decreasing the refrigeration unit of a central air conditioning system according to claim 7, characterized in that, Step S3 further includes the following steps: The refrigeration unit is controlled to reduce its operating rate by a differential pressure controller: as one or more user air conditioning terminals continue to shut down, when the change in differential pressure reaches the first pressure setting threshold, the electric bypass valve has reached its maximum opening, i.e., the rated flow rate has been reached. Since the bypass flow cannot be increased, the flow through the refrigeration unit will continuously decrease. Therefore, at this time, the number of refrigeration units controlled by the differential pressure controller to be turned on is reduced by one, so that the flow of the refrigeration unit can be restored to the rated flow, and the change in differential pressure value can be restored to the rated differential pressure value.

9. The control method for automatically increasing or decreasing the refrigeration unit of a central air conditioning system according to claim 7, characterized in that, Step S3 further includes the following steps: The refrigeration unit is controlled by a differential pressure controller to add power: as one or more user air conditioning terminals continue to be turned on, when the change in differential pressure reaches the second pressure setting threshold, the electric bypass valve is completely closed and cannot bypass the flow. Since the flow cannot be bypassed, the flow through the refrigeration unit will continue to increase. Therefore, at this time, an additional refrigeration unit is turned on by the differential pressure controller to restore the flow of the refrigeration unit to the rated flow and restore the differential pressure value change to the rated differential pressure value.

10. The control system for the control method of automatically adding or subtracting refrigeration units in a central air conditioning system according to any one of claims 1 to 9, characterized in that, include: A differential pressure sensor is used to monitor the differential pressure value between the inlet and outlet of the chilled water in each chiller unit; A differential pressure controller is used to receive the detection signal from the differential pressure sensor and, based on the magnitude of the differential pressure value, control the opening degree of the electric bypass valve on the main supply and return water pipes, as well as control the increase or decrease of the number of refrigeration units that are turned on. A temperature difference sensor is used to monitor the temperature difference between the inlet and outlet of the chilled water in each chiller unit. A temperature difference controller is used to receive the detection signal from the temperature difference sensor and control the refrigeration unit to reduce its operating speed based on the temperature difference value and the value between the temperature difference value and a first temperature set threshold. A return water temperature sensor is used to monitor the return water temperature of the chilled water return main pipe; A return water temperature controller is used to receive the detection signal from the return water temperature sensor and set a threshold value between the return water temperature and the second temperature to control the operation of the refrigeration unit.

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