Fluorine pump mode low-load control method for fluorine pump double-circulation air conditioning unit

Abstract

The invention relates to the technical field of air conditioners, in particular to a fluorine pump mode low-load control method for a fluorine pump double-circulation air conditioning unit. Comprising the following steps that the running state of an exhaust fan is automatically adjusted according to refrigeration requirements, the initial rotating speed and the maximum limited rotating speed of the exhaust fan in a fluorine pump mode are calculated, whether the extremely-low-temperature anti-freezing control condition is met or not is judged, whether the exhaust fan needs to be closed or not is judged according to the reduction condition, and an electronic expansion valve is gradually turned down; gradually increasing the suction superheat degree and reducing the rotating speed of the fluorine pump. The initial rotating speed of the exhaust fan is dynamically adjusted according to the external environment temperature, the maximum limited rotating speed of the exhaust fan is dynamically adjusted according to the indoor and outdoor temperature difference, the real-time rotating speed of the exhaust fan is dynamically adjusted according to the refrigeration requirement, then the exhaust fan is sequentially closed according to the fixed sequence, meanwhile, an electronic expansion valve is gradually turned down, and the suction superheat degree is gradually increased; and finally, the frequency of the fluorine pump is reduced step by step, the impact on a refrigerating system can be reduced to the minimum extent, and meanwhile the energy-saving requirement of a unit is met to the maximum extent.

Description

Technical Field

[0001] The invention relates to the technical field of air conditioning, and in particular to a low-load control method for a fluorine pump mode of a fluorine pump dual-circulation air conditioning unit. Background Art

[0002] Fluorine pump dual-cycle air conditioning units are widely used in data centers, industrial cooling and other fields due to their high efficiency and energy saving. However, under low load conditions, how to effectively control the exhaust fan, fluorine pump and electronic expansion valve to ensure the stable operation and energy efficiency of the system is an issue that needs to be focused on and improved. Traditional control methods are prone to problems such as reduced energy efficiency and system instability under low load conditions.

[0003] In the existing technical solutions for fluorine pump dual-circulation air-conditioning units, in low-load mode at extremely low temperatures, the exhaust fan and fluorine pump are usually directly shut down to adapt to low-load requirements. Frequent starting and stopping of exhaust fans and fluorine pumps will increase equipment wear, especially causing additional pressure and damage to mechanical seals and bearings, thereby increasing the risk of leakage and shortening equipment life. Secondly, frequent starting and stopping will also lead to energy waste, because the current at startup is large, and frequent starting and stopping for a long time will increase overall energy consumption. In addition, completely shutting down the exhaust fan and fluorine pump under low-load conditions will lead to a decrease in the accuracy of temperature control in the computer room, especially when the external environmental conditions change. The system's response speed and recovery ability will be affected, which will have a certain impact on the stability of the system. Summary of the invention

[0004] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide a low-load control method for a fluorine pump mode of a fluorine pump dual-cycle air-conditioning unit.

[0005] The purpose of the present invention is achieved through the following technical solution: A fluorine pump mode low-load control method for a fluorine pump dual-cycle air-conditioning unit, comprising the following steps:

[0006] S1. Automatically adjust the operating status of the exhaust fan according to the cooling demand;

[0007] S2. Calculate the initial speed and maximum speed limit of the exhaust fan in the fluorine pump mode;

[0008] S3, judging whether the conditions for extremely low temperature antifreeze control are met, and if so, entering the extremely low temperature antifreeze control mode;

[0009] S4. In the extremely low temperature antifreeze control mode, determine whether the exhaust fan needs to be shut down according to the machine reduction conditions, and control the exhaust fans that are not shut down according to the preset logic;

[0010] S5. In the extremely low temperature antifreeze control mode, gradually close the electronic expansion valve, then gradually increase the suction superheat, and then check whether the conditions for the fluorine pump frequency reduction are met;

[0011] If the conditions for reducing the frequency of the fluorine pump are met, the speed of the fluorine pump will be reduced according to the preset step size. If the conditions for reducing the frequency of the fluorine pump are not met, the fluorine pump will maintain the current speed.

[0012] The present invention is further configured such that the automatic adjustment of the operating state of the exhaust fan according to the refrigeration demand comprises:

[0013] Obtaining the external ambient temperature; calculating the initial speed of the exhaust fan according to the external ambient temperature;

[0014] Obtaining the indoor and outdoor temperature difference; calculating the maximum limited speed of the exhaust fan according to the indoor and outdoor temperature difference;

[0015] Calculate the real-time speed of the exhaust fan based on the cooling demand.

[0016] The present invention is further configured such that when the initial speed of the exhaust fan is less than the minimum speed of the exhaust fan, the value of the initial speed of the exhaust fan is the minimum speed of the exhaust fan; when the initial speed of the exhaust fan is greater than the rated speed of the exhaust fan, the value of the initial speed of the exhaust fan is the rated speed of the exhaust fan; when the initial speed of the exhaust fan is between the minimum speed of the exhaust fan and the rated speed of the exhaust fan, the initial speed of the exhaust fan is calculated according to the following formula:

[0017] The initial speed of the exhaust fan = A*external ambient temperature+B;

[0018] Wherein, A = (rated speed of exhaust fan - minimum speed of exhaust fan) / (upper limit of external ambient temperature - lower limit of external ambient temperature);

[0019] B = minimum exhaust fan speed - lower limit of external ambient temperature * A.

[0020] The present invention is further configured such that when the maximum limited speed of the exhaust fan is less than the lower limit of the maximum speed of the exhaust fan, the value of the maximum limited speed of the exhaust fan is the lower limit of the maximum speed of the exhaust fan; when the maximum limited speed of the exhaust fan is greater than the rated speed of the exhaust fan, the value of the maximum limited speed of the exhaust fan is the rated speed of the exhaust fan; when the maximum limited speed of the exhaust fan is between the lower limit of the maximum speed of the exhaust fan and the rated speed of the exhaust fan, the maximum limited speed of the exhaust fan is calculated according to the following formula:

[0021] The maximum speed limit of the exhaust fan = C*indoor and outdoor temperature difference + D;

[0022] Wherein, C = (lower limit of maximum speed of exhaust fan - rated speed of exhaust fan) / (upper limit of indoor and outdoor temperature difference - lower limit of indoor and outdoor temperature difference);

[0023] D = rated speed of exhaust fan - lower limit of indoor and outdoor temperature difference * C.

[0024] The present invention is further configured to calculate the real-time rotation speed of the exhaust fan according to the following formula:

[0025] u(k)=E*P ID(k)+F;

[0026]

[0027] Where CFC is the cooling demand; PID(k) is the calculated value of PID at the kth sampling time; e(k) is the deviation between the supply air temperature detection value and the set value or the deviation between the return air temperature detection value and the set value at the kth sampling time; e(k-1) is the deviation between the supply air temperature detection value and the set value or the deviation between the return air temperature detection value and the set value at the k-1th sampling time; Kp is the cooling demand proportional coefficient; Ti is the cooling demand integral coefficient; Td is the cooling demand differential coefficient; T is the cooling demand calculation period;

[0028] u(k) is the real-time speed of the exhaust fan;

[0029] E = (maximum speed limit of exhaust fan - minimum speed of exhaust fan) / (upper limit of exhaust fan mapping demand - lower limit of exhaust fan mapping demand);

[0030] F = minimum exhaust fan speed - lower limit of exhaust fan single system mapping requirement * E.

[0031] The present invention is further configured such that the step of judging whether the conditions for extremely low temperature antifreeze control are met includes:

[0032] Determine whether the extremely low temperature antifreeze enable setting is turned on;

[0033] Determine whether the external environment temperature is lower than the antifreeze ambient temperature of the exhaust fan for a first period of time;

[0034] Determine whether the cooling demand is less than the antifreeze demand of the exhaust fan;

[0035] Determine whether the real-time rotation speed of the turned-on exhaust fan is less than or equal to the sum of the minimum rotation speed of the exhaust fan and the first redundant deviation for a second consecutive period of time.

[0036] The present invention is further configured such that the method of judging whether the exhaust fan needs to be shut down according to the machine reduction condition and controlling the exhaust fan that is not shut down according to the preset logic includes:

[0037] A1. Obtain the cooling demand and real-time speed of the exhaust fan;

[0038] A2. If the cooling demand is less than the antifreeze demand of the exhaust fan, and the real-time speed of the exhaust fan is less than or equal to the sum of the minimum speed of the exhaust fan and the second redundant deviation for a third consecutive period, the exhaust fan is gradually turned off according to the preset logic;

[0039] A3. Repeat step A1 until at least one exhaust fan in the system remains in operation;

[0040] The preset logic includes:

[0041] The speed of the exhaust fan is gradually reduced to the minimum speed of the exhaust fan according to 1% / winter antifreeze adjustment cycle of the exhaust fan, and the exhaust fan is turned off after a delay of 5s;

[0042] The exhaust fans are shut down in the following order: first shut down the exhaust fans close to the outdoor side, then shut down the exhaust fans close to the indoor side, and finally shut down the exhaust fans between the outdoor side and the indoor side.

[0043] The present invention is further configured that the checking whether the condition for reducing the frequency of the fluorine pump is met includes:

[0044] Determine whether the current opening of all electronic expansion valves is less than the sum of the minimum opening of the expansion valve and the initial opening, and whether all suction superheats are less than the sum of the target suction superheat and the preset deviation, then reduce the fluorine pump speed according to the preset step size.

[0045] The present invention is further configured such that the checking whether the conditions for reducing the frequency of the fluorine pump are met includes: when the extremely low temperature antifreeze enable is set to be enabled, determining whether the exhaust fan of the corresponding system has been turned off to the minimum number and is at the minimum exhaust fan speed; if so, continuously detecting whether the refrigeration demand is less than the fluorine pump speed reduction demand, and whether the supply air temperature is less than the difference between the supply air temperature setting value and the fluorine pump speed reduction temperature deviation; if so, reducing the fluorine pump speed according to a preset step size.

[0046] The present invention is further configured such that the checking whether the conditions for reducing the frequency of the fluorine pump are met includes: when the extremely low temperature antifreeze enable is set to disabled, determining whether the exhaust fans running in the corresponding system are all at the minimum exhaust fan speed; if so, continuously detecting whether the refrigeration demand is less than the fluorine pump speed reduction demand, and whether the supply air temperature is less than the difference between the supply air temperature setting value and the fluorine pump speed reduction temperature deviation; if so, reducing the fluorine pump speed according to a preset step size.

[0047] The beneficial effects of the present invention are as follows: the present invention dynamically adjusts the initial speed of the exhaust fan according to the external ambient temperature, dynamically adjusts the maximum speed of the exhaust fan according to the indoor and outdoor temperature difference, dynamically adjusts the real-time speed of the exhaust fan according to the refrigeration demand, and then shuts down the exhaust fan in a fixed order, while gradually closing the electronic expansion valve, gradually increasing the suction superheat, and finally gradually reducing the frequency of the fluorine pump; compared with the mechanical method of directly shutting down the fan, expansion valve and fluorine pump, the dynamic adjustment of each component can ensure that the impact on the refrigeration system is minimized, while meeting the energy-saving needs of the unit to the greatest extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The invention is further described using the accompanying drawings, but the embodiments in the accompanying drawings do not constitute any limitation to the invention. A person skilled in the art can obtain other drawings based on the following drawings without creative work.

[0049] Figure 1 It is a system principle diagram of the present invention;

[0050] Figure 2 This is a structural principle diagram of the fluorine pump double-circulation air conditioning unit of the present invention; DETAILED DESCRIPTION

[0051] The present invention is further described in conjunction with the following examples.

[0052] Depend on Figure 1 to Figure 2 It can be seen that the low-load control method of the fluorine pump mode of the fluorine pump dual-cycle air-conditioning unit described in this embodiment includes the following steps:

[0053] S1. Automatically adjust the operating status of the exhaust fan according to the cooling demand;

[0054] S2. Calculate the initial speed and maximum speed limit of the exhaust fan in the fluorine pump mode;

[0055] S3, judging whether the conditions for extremely low temperature antifreeze control are met, and if so, entering the extremely low temperature antifreeze control mode;

[0056] S4. In the extremely low temperature antifreeze control mode, determine whether the exhaust fan needs to be shut down according to the machine reduction conditions, and control the exhaust fans that are not shut down according to the preset logic;

[0057] S5. In the extremely low temperature antifreeze control mode, gradually close the electronic expansion valve, then gradually increase the suction superheat, and then check whether the conditions for the fluorine pump frequency reduction are met;

[0058] If the conditions for reducing the frequency of the fluorine pump are met, the speed of the fluorine pump will be reduced according to the preset step size. If the conditions for reducing the frequency of the fluorine pump are not met, the fluorine pump will maintain the current speed.

[0059] Specifically, the fluorine pump mode low-load control method of the fluorine pump dual-circulation air-conditioning unit described in this embodiment dynamically adjusts the initial speed of the exhaust fan according to the external ambient temperature, dynamically adjusts the maximum limited speed of the exhaust fan according to the indoor and outdoor temperature difference, and dynamically adjusts the real-time speed of the exhaust fan according to the refrigeration demand. The exhaust fan is then shut down in a fixed order, and the electronic expansion valve is gradually closed to gradually increase the suction superheat, and finally the fluorine pump is gradually reduced in frequency. Compared with the mechanical method of directly shutting down the fan, expansion valve and fluorine pump, dynamic adjustment of each component can ensure that the impact on the refrigeration system is minimized, while meeting the energy-saving needs of the unit to the greatest extent.

[0060] The low-load control method of the fluorine pump mode of a fluorine pump dual-cycle air-conditioning unit described in this embodiment, wherein the operating state of the exhaust fan is automatically adjusted according to the refrigeration demand, comprises:

[0061] Obtaining the external ambient temperature; calculating the initial speed of the exhaust fan according to the external ambient temperature;

[0062] Obtaining the indoor and outdoor temperature difference; calculating the maximum limited speed of the exhaust fan according to the indoor and outdoor temperature difference;

[0063] Calculate the real-time speed of the exhaust fan based on the cooling demand.

[0064] Specifically, this embodiment obtains the external ambient temperature of the fluorine pump dual-circulation air-conditioning unit by using an outdoor temperature sensor to detect the external ambient temperature in real time. The external ambient temperature is the value of the condenser inlet air temperature when the exhaust fan is turned on, and then transmits the detected temperature data to the controller.

[0065] The indoor and outdoor temperature difference of the fluorine pump dual-cycle air-conditioning unit is obtained by calculating the indoor and outdoor temperature difference based on the indoor temperature data detected by the indoor temperature sensor, i.e., the return air temperature, and the external ambient temperature detected in real time by the outdoor temperature sensor.

[0066] Specifically, in hot weather, the condenser requires a higher air volume to dissipate heat. If the exhaust fan speed is set too low, the condenser temperature may be too high, affecting the cooling effect and increasing energy consumption. In a low temperature environment, the maximum speed limit of the exhaust fan needs to be controlled. Excessive exhaust fan speed may cause the condensation pressure to decrease, and the evaporation pressure will also decrease. The evaporator is at risk of condensation, affecting the cooling effect. Therefore, there is a positive linear relationship between the initial speed of the exhaust fan and the external ambient temperature. The exhaust fan speed increases with the increase of the external ambient temperature; similarly, the maximum speed limit of the exhaust fan is inversely proportional to the indoor and outdoor temperature difference. The maximum speed limit of the exhaust fan decreases with the increase of the indoor and outdoor temperature difference. This is because the indoor and outdoor temperature difference = return air temperature - condenser inlet air temperature, and when the return air temperature is normal, it is equal to the indoor target set temperature value and remains unchanged. The condenser inlet air temperature is the external ambient temperature.

[0067] In the low-load control method of the fluorine pump mode of a fluorine pump dual-cycle air-conditioning unit described in this embodiment, when the initial speed of the exhaust fan is less than the minimum speed of the exhaust fan (the default value is 15%), the value of the initial speed of the exhaust fan is the minimum speed of the exhaust fan; when the initial speed of the exhaust fan is greater than the rated speed of the exhaust fan (the default value is 90%), the value of the initial speed of the exhaust fan is the rated speed of the exhaust fan; when the initial speed of the exhaust fan is between the minimum speed of the exhaust fan and the rated speed of the exhaust fan, the initial speed of the exhaust fan is calculated according to the following formula:

[0068] The initial speed of the exhaust fan = A*external ambient temperature+B;

[0069] Among them, A = (exhaust fan rated speed - exhaust fan minimum speed) / (exterior ambient temperature upper limit - exterior ambient temperature lower limit); the exterior ambient temperature upper limit is set to 20 ° C, the exterior ambient temperature lower limit is set to 0 ° C; therefore, it is calculated that A = (90-15) / (20-0) = 3.75;

[0070] B = minimum speed of exhaust fan - lower limit of external ambient temperature * A; therefore, B = 15;

[0071] In summary, in this embodiment, the initial speed of the exhaust fan=3.75*external ambient temperature+15.

[0072] In order to make the unit system better adapt to the dynamically changing ambient temperature, this solution also considers dynamically setting the initial speed of the exhaust fan in the fluorine pump mode and the maximum speed limit of the exhaust fan.

[0073] In the low-load control method of the fluorine pump mode of a fluorine pump dual-cycle air-conditioning unit described in this embodiment, when the maximum limited speed of the exhaust fan is less than the lower limit of the maximum speed of the exhaust fan (the default value is 30%), the value of the maximum limited speed of the exhaust fan is the lower limit of the maximum speed of the exhaust fan; when the maximum limited speed of the exhaust fan is greater than the rated speed of the exhaust fan (the default value is 90%), the value of the maximum limited speed of the exhaust fan is the rated speed of the exhaust fan; when the maximum limited speed of the exhaust fan is between the lower limit of the maximum speed of the exhaust fan and the rated speed of the exhaust fan, the maximum limited speed of the exhaust fan is calculated according to the following formula:

[0074] The maximum speed limit of the exhaust fan = C*indoor and outdoor temperature difference + D; the upper limit of the indoor and outdoor temperature difference is set to 32°C, and the lower limit of the indoor and outdoor temperature difference is set to 27°C

[0075] Among them, C = (lower limit of maximum speed of exhaust fan - rated speed of exhaust fan) / (upper limit of indoor and outdoor temperature difference - lower limit of indoor and outdoor temperature difference); therefore, it is calculated that C = (30-90) / (32-27) = -12;

[0076] D = rated speed of exhaust fan - lower limit of indoor and outdoor temperature difference * C, so D = 414;

[0077] In summary, in this embodiment, the maximum limited speed of the exhaust fan = -12*indoor and outdoor temperature difference + 414.

[0078] The present embodiment describes a fluorine pump dual-cycle air conditioning unit fluorine pump mode low-load control method, which calculates the real-time speed of the exhaust fan according to the following formula:

[0079] u(k)=E*P ID(k)+F;

[0080]

[0081] Where CFC is the cooling demand, and the calculated value range is [0,100%]; PID(k) is the PID calculated value at the kth sampling time; e(k) is the deviation between the supply air temperature detection value and the set value or the return air temperature detection value and the set value at the kth sampling time; e(k-1) is the deviation between the supply air temperature detection value and the set value or the return air temperature detection value and the set value at the k-1th sampling time; Kp is the cooling demand proportional coefficient; Ti is the cooling demand integral coefficient; Td is the cooling demand differential coefficient; T is the cooling demand calculation period;

[0082] u(k) is the real-time speed of the exhaust fan;

[0083] E = (maximum speed limit of exhaust fan - minimum speed of exhaust fan) / (upper limit of exhaust fan mapping demand - lower limit of exhaust fan mapping demand);

[0084] F = minimum exhaust fan speed - lower limit of exhaust fan single system mapping requirement * E.

[0085] Among them, the minimum speed of the exhaust fan is 15%. If the number of turned-on fluorine pump refrigeration subsystems = 1, and the number of turned-on compressor refrigeration subsystems = 0, the upper limit of the exhaust fan mapping demand and the lower limit of the exhaust fan mapping demand are 60% and 10% respectively; if the number of turned-on fluorine pump refrigeration subsystems = 2, and the number of turned-on compressor refrigeration subsystems = 0, the upper limit of the exhaust fan mapping demand and the lower limit of the exhaust fan mapping demand are 100% and 20% respectively.

[0086] Therefore, in this embodiment, the single fluorine pump system E = (100-15) / (60-10) = 1.5; the double fluorine pump system E = (100-15) / (100-20) = 0.9375;

[0087] Single fluorine pump system F = 15-10*1.5 = 0; double fluorine pump system F = 15-10*0.9375 = 5.625;

[0088] Therefore, in summary, in the single fluorine pump system, u(k)=1.5*PID(k); in the double fluorine pump system, u(k)=0.9375*PID(k)+5.625.

[0089] The present embodiment describes a fluorine pump dual-cycle air conditioning unit fluorine pump mode low-load control method, wherein the judgment of whether the extremely low temperature antifreeze control condition is met includes:

[0090] Determine whether the extremely low temperature antifreeze enable setting is turned on;

[0091] Determine whether the external environment temperature is lower than the antifreeze ambient temperature of the exhaust fan for a first period of time;

[0092] Determine whether the cooling demand is less than the antifreeze demand of the exhaust fan;

[0093] Determine whether the real-time rotation speed of the turned-on exhaust fan is less than or equal to the sum of the minimum rotation speed of the exhaust fan and the first redundant deviation for a second consecutive period of time.

[0094] Through the above settings, it is possible to determine whether the fluorine pump dual-circulation air-conditioning unit is in an extremely low temperature environment, thereby entering extremely low temperature antifreeze control.

[0095] The present embodiment describes a fluorine pump dual-cycle air conditioning unit fluorine pump mode low-load control method, wherein the method determines whether the exhaust fan needs to be shut down according to the machine reduction condition, and controls the exhaust fan that is not shut down according to the preset logic, including:

[0096] A1. Obtain the cooling demand and real-time speed of the exhaust fan;

[0097] A2. If the cooling demand is less than the antifreeze demand of the exhaust fan, and the real-time speed of the exhaust fan is less than or equal to the sum of the minimum speed of the exhaust fan and the second redundant deviation for a third consecutive period, the exhaust fan is gradually turned off according to the preset logic;

[0098] A3. Repeat step A1 until at least one exhaust fan in the system remains in operation;

[0099] The preset logic includes:

[0100] The speed of the exhaust fan is gradually reduced to the minimum speed of the exhaust fan according to 1% / winter antifreeze adjustment cycle of the exhaust fan, and the exhaust fan is turned off after a delay of 5s;

[0101] The exhaust fans are shut down in the following order: first shut down the exhaust fans close to the outdoor side, then shut down the exhaust fans close to the indoor side, and finally shut down the exhaust fans between the outdoor side and the indoor side.

[0102] In the low-load mode of the air-conditioning system, in order to protect the equipment from damage caused by extremely low temperatures, the system will implement exhaust fan load reduction protection. At this time, the indicator light on the system touch screen will flash to indicate that it is in extremely low temperature antifreeze control. Then, the exhaust fans will be gradually shut down in the established order, but at least one exhaust fan in each system will be kept running to maintain the basic operation of the system. After shutting down each exhaust fan, the system will re-evaluate whether the conditions for shutting down the next exhaust fan are met, that is, whether the cooling demand is still lower than the antifreeze demand, and whether the exhaust fan speed remains below 17% (exhaust fan minimum speed + 2%) for 5 consecutive minutes. If the conditions are met, the next exhaust fan will gradually slow down to the minimum speed (the default value is 15%) and shut down after a delay of 5 seconds.

[0103] In addition, when shutting down the exhaust fan, shutting down the exhaust fans near the outdoor side and the indoor side first can avoid airflow turbulence and sudden increase in local wind resistance caused by suddenly stopping the middle exhaust fan, ensuring uniform exhaust. In addition, since the condenser is located below the exhaust fan, after shutting down the exhaust fans near the outdoor side and the indoor side, shutting down the middle exhaust fan will not immediately have a significant impact on the condenser. This operation sequence can ensure that the condenser continues to work under conditions of low wind resistance and appropriate air intake.

[0104] The present embodiment describes a method for controlling the fluorine pump mode of a fluorine pump dual-cycle air-conditioning unit under low load, wherein the checking whether the conditions for reducing the frequency of the fluorine pump are met includes: judging whether the current opening of all electronic expansion valves is less than the sum of the minimum opening of the expansion valve and the initial opening, and whether all suction superheats are less than the sum of the target suction superheat and the preset deviation, and then reducing the speed of the fluorine pump according to the preset step length. The present embodiment describes a method for controlling the fluorine pump mode of a fluorine pump dual-cycle air-conditioning unit under low load, wherein the checking whether the conditions for reducing the frequency of the fluorine pump are met includes: judging whether the exhaust fan of the corresponding system has been turned off to the minimum number and the exhaust fan has the minimum speed when the extremely low temperature antifreeze enable is set to enabled; if so, continuously detecting whether the cooling demand is less than the fluorine pump speed reduction demand, and whether the supply air temperature is less than the difference between the supply air temperature setting value and the fluorine pump speed reduction temperature deviation; if so, reducing the speed of the fluorine pump according to the preset step length. The present embodiment describes a method for controlling the low-load control of the fluorine pump mode of a fluorine pump dual-circulation air-conditioning unit, wherein the checking whether the conditions for reducing the frequency of the fluorine pump are met includes: when the extremely low temperature antifreeze enable is set to disabled, determining whether the exhaust fans running in the corresponding system are all at the minimum exhaust fan speed; if so, continuously detecting whether the cooling demand is less than the fluorine pump speed reduction demand, and whether the supply air temperature is less than the difference between the supply air temperature setting value and the fluorine pump speed reduction temperature deviation; if so, reducing the fluorine pump speed according to a preset step size.

[0105] Specifically, this embodiment can prevent the condenser from being overheated in a high-temperature environment and the risk of condensation on the evaporator in a low-temperature environment by dynamically adjusting the initial speed and the maximum speed limit of the exhaust fan, thereby reducing the impact of the external environment on the refrigeration effect, and enabling the unit system to better adapt to dynamically changing ambient temperatures, thereby achieving precise temperature control and energy efficiency optimization.

[0106] In addition, through specific temperature and operating parameter conditions, it is possible to accurately determine whether to enter the extremely low temperature antifreeze control mode to ensure the safe operation of the system in a low temperature environment.

[0107] In addition, by gradually shutting down the exhaust fans and re-evaluating the conditions for reducing the number of fans, it is ensured that at least one exhaust fan is running in the system to avoid the risk of the system completely stopping operation.

[0108] In addition, by gradually closing the electronic expansion valve and adjusting the speed of the fluorine pump, the refrigerant flow rate is reduced, the target superheat is gradually increased, and then it is determined whether to continue to reduce the speed of the fluorine pump to further reduce energy consumption and ensure the stability and energy efficiency of the system.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A low-load control method for a fluorine pump mode of a fluorine pump dual-cycle air-conditioning unit, characterized in that: The following steps are involved: S1. Automatically adjust the operating status of the exhaust fan according to the cooling demand; S2. Calculate the initial speed and maximum speed limit of the exhaust fan in the fluorine pump mode; S3, judging whether the conditions for extremely low temperature antifreeze control are met, and if so, entering the extremely low temperature antifreeze control mode; S4. In the extremely low temperature antifreeze control mode, determine whether the exhaust fan needs to be shut down according to the machine reduction conditions, and control the exhaust fans that are not shut down according to the preset logic; S5. In the extremely low temperature antifreeze control mode, gradually close the electronic expansion valve, then gradually increase the suction superheat, and then check whether the conditions for the fluorine pump frequency reduction are met; If the conditions for reducing the frequency of the fluorine pump are met, the speed of the fluorine pump will be reduced according to the preset step size. If the conditions for reducing the frequency of the fluorine pump are not met, the fluorine pump will maintain the current speed.

2. A fluorine pump mode low-load control method for a fluorine pump dual-cycle air conditioning unit according to claim 1, characterized in that: The automatic adjustment of the operating state of the exhaust fan according to the refrigeration demand includes: Obtaining the external ambient temperature; calculating the initial speed of the exhaust fan according to the external ambient temperature; Obtaining the indoor and outdoor temperature difference; calculating the maximum limited speed of the exhaust fan according to the indoor and outdoor temperature difference; Calculate the real-time speed of the exhaust fan based on the cooling demand.

3. A fluorine pump mode low-load control method for a fluorine pump dual-cycle air conditioning unit according to claim 2, characterized in that: When the initial speed of the exhaust fan is less than the minimum speed of the exhaust fan, the value of the initial speed of the exhaust fan is the minimum speed of the exhaust fan; when the initial speed of the exhaust fan is greater than the rated speed of the exhaust fan, the value of the initial speed of the exhaust fan is the rated speed of the exhaust fan; when the initial speed of the exhaust fan is between the minimum speed of the exhaust fan and the rated speed of the exhaust fan, the initial speed of the exhaust fan is calculated according to the following formula: The initial speed of the exhaust fan = A*external ambient temperature+B; Wherein, A = (rated speed of exhaust fan - minimum speed of exhaust fan) / (upper limit of external ambient temperature - lower limit of external ambient temperature); B = minimum exhaust fan speed - lower limit of external ambient temperature * A.

4. A fluorine pump mode low-load control method for a fluorine pump dual-cycle air conditioning unit according to claim 2, characterized in that: When the maximum speed limit of the exhaust fan is less than the lower limit of the maximum speed of the exhaust fan, the value of the maximum speed limit of the exhaust fan is the lower limit of the maximum speed of the exhaust fan; when the maximum speed limit of the exhaust fan is greater than the rated speed of the exhaust fan, the value of the maximum speed limit of the exhaust fan is the rated speed of the exhaust fan; when the maximum speed limit of the exhaust fan is between the lower limit of the maximum speed of the exhaust fan and the rated speed of the exhaust fan, the maximum speed limit of the exhaust fan is calculated according to the following formula: The maximum speed limit of the exhaust fan = C*indoor and outdoor temperature difference + D; Wherein, C = (lower limit of maximum speed of exhaust fan - rated speed of exhaust fan) / (upper limit of indoor and outdoor temperature difference - lower limit of indoor and outdoor temperature difference); D = rated speed of exhaust fan - lower limit of indoor and outdoor temperature difference * C.

5. A fluorine pump mode low-load control method for a fluorine pump dual-cycle air conditioning unit according to claim 2, characterized in that: Calculate the real-time speed of the exhaust fan according to the following formula: u(k)=E*PID(k)+F; Where CFC is the cooling demand; PID(k) is the PID calculation value at the kth sampling time; e(k) is the deviation between the supply air temperature detection value and the set value or the return air temperature detection value and the set value at the kth sampling time; e(k-1) is the deviation between the supply air temperature detection value and the set value or the return air temperature detection value and the set value at the k-1th sampling time; Kp is the cooling demand proportional coefficient; Ti is the cooling demand integral coefficient; Td is the cooling demand differential coefficient; T is the cooling demand calculation period; u(k) is the real-time speed of the exhaust fan; E = (maximum speed limit of exhaust fan - minimum speed of exhaust fan) / (upper limit of exhaust fan mapping demand - lower limit of exhaust fan mapping demand); F = minimum exhaust fan speed - lower limit of exhaust fan single system mapping requirement * E.

6. A fluorine pump dual-cycle air conditioning unit fluorine pump mode low-load control method according to claim 1, characterized in that: The determination of whether the conditions for extremely low temperature antifreeze control are met includes: Determine whether the extremely low temperature antifreeze enable setting is turned on; Determine whether the external environment temperature is lower than the antifreeze ambient temperature of the exhaust fan for a first period of time; Determine whether the cooling demand is less than the antifreeze demand of the exhaust fan; Determine whether the real-time rotation speed of the turned-on exhaust fan is less than or equal to the sum of the minimum rotation speed of the exhaust fan and the first redundant deviation for a second consecutive period of time.

7. A fluorine pump dual-cycle air conditioning unit fluorine pump mode low-load control method according to claim 1, characterized in that: The method of judging whether the exhaust fan needs to be shut down according to the machine reduction condition and controlling the exhaust fan that is not shut down according to the preset logic includes: A1. Obtain the cooling demand and real-time speed of the exhaust fan; A2. If the cooling demand is less than the antifreeze demand of the exhaust fan, and the real-time speed of the exhaust fan is less than or equal to the sum of the minimum speed of the exhaust fan and the second redundant deviation for a third consecutive period, the exhaust fan is gradually turned off according to the preset logic; A3. Repeat step A1 until at least one exhaust fan in the system remains in operation; The preset logic includes: The speed of the exhaust fan is gradually reduced to the minimum speed of the exhaust fan according to 1% / winter antifreeze adjustment cycle of the exhaust fan, and the exhaust fan is turned off after a delay of 5s; The exhaust fans are shut down in the following order: first shut down the exhaust fans close to the outdoor side, then shut down the exhaust fans close to the indoor side, and finally shut down the exhaust fans between the outdoor side and the indoor side.

8. The low-load control method for a fluorine pump mode of a fluorine pump dual-cycle air conditioning unit according to claim 1, characterized in that: The inspection of whether the conditions for reducing the frequency of the fluorine pump are met includes: Determine whether the current opening of all electronic expansion valves is less than the sum of the minimum opening of the expansion valve and the initial opening, and whether all suction superheats are less than the sum of the target suction superheat and the preset deviation, then reduce the fluorine pump speed according to the preset step size.

9. A fluorine pump dual-cycle air conditioning unit fluorine pump mode low-load control method according to claim 1, characterized in that: The checking whether the conditions for reducing the frequency of the fluorine pump are met includes: when the extremely low temperature antifreeze enable is set to be enabled, determining whether the exhaust fan of the corresponding system has been turned off to the minimum number and the exhaust fan has the minimum speed; if so, continuously detecting whether the refrigeration demand is less than the fluorine pump speed reduction demand, and whether the supply air temperature is less than the difference between the supply air temperature setting value and the fluorine pump speed reduction temperature deviation; if so, reducing the fluorine pump speed according to the preset step size.

10. A fluorine pump dual-cycle air conditioning unit fluorine pump mode low-load control method according to claim 1, characterized in that: The checking whether the conditions for reducing the frequency of the fluorine pump are met includes: when the extremely low temperature antifreeze enable is set to disabled, determining whether the exhaust fans running in the corresponding system are all at the minimum exhaust fan speed; if so, continuously detecting whether the refrigeration demand is less than the fluorine pump speed reduction demand, and whether the supply air temperature is less than the difference between the supply air temperature setting value and the fluorine pump speed reduction temperature deviation; if so, reducing the fluorine pump speed according to the preset step size.

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