Air conditioning unit compressor mode low-load control method

Abstract

The invention relates to the technical field of air conditioners, in particular to an air conditioning unit compressor mode low-load control method. The low-load control method for the compressor mode of the air conditioning unit further comprises the following steps that S1, whether the air conditioning unit meets the low-load control entering condition or not is detected in real time; s2, if the condition of entering the low-load control is met, entering a low-load adjusting mode; s3, in the low-load adjusting mode, whether the air conditioning unit meets the low-load control quitting condition or not is detected in real time; and S4, if the condition of quitting the low-load control is met, entering a low-load quitting mode. When the air conditioning unit meets the low-load control condition, namely when the thermal load is very small, the output of the refrigerating capacity of the air conditioner can be reduced to the maximum extent through the control sequence of closing one compressor, increasing the condensing pressure, increasing the superheat degree and closing one electronic expansion valve; the problems of frequent starting and stopping of the compressor, large indoor temperature fluctuation and the like are effectively solved.

Description

Technical Field

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

[0002] Existing variable frequency air conditioning units generally consist of a single system, which includes a variable frequency compressor, an evaporator, a condenser, and an electronic expansion valve. This configuration allows the operating frequency of the compressor to be adjusted to adapt to different heat load requirements, while the flow of refrigerant through the evaporator can be adjusted by the expansion valve. However, since the heat exchange area of ​​the evaporator is fixed and the system is only equipped with one compressor, the system's adjustment ability is limited in the face of lower heat loads.

[0003] Under the condition of low heat load, existing variable frequency air conditioner units mainly rely on reducing the operating frequency of the compressor and adjusting the opening of the expansion valve to reduce the cooling capacity. However, even at the lowest operating frequency, the cooling capacity generated by the compressor may still far exceed the actual cooling capacity required by the room. This situation causes the compressor to start and stop frequently, which in turn causes large fluctuations in indoor temperature, which not only affects the user's comfort experience, but also reduces energy utilization efficiency, increases energy consumption, and has a negative impact on the life of the compressor. Summary of the invention

[0004] The object of the present invention is to provide a method for controlling a compressor mode of an air-conditioning unit under low load in view of the above-mentioned deficiencies in the prior art.

[0005] The object of the present invention is achieved by the following technical solutions: A method for controlling a compressor mode of an air-conditioning unit under low load, comprising an air-conditioning unit; the air-conditioning unit comprises a first compressor, a second compressor, a condenser, a first electronic expansion valve, a second electronic expansion valve, a first evaporator and a second evaporator;

[0006] The first compressor is connected in parallel with the second compressor; one end of the first compressor is connected to one end of the condenser; the other end of the condenser is connected to one end of the first evaporator through a first electronic expansion valve; the other end of the first evaporator is connected to the other end of the first compressor; the other end of the condenser is connected to one end of the second evaporator through a second electronic expansion valve; the other end of the second evaporator is connected to the other end of the first compressor; an exhaust fan is provided at the condenser; and blowers are provided at the first evaporator and the second evaporator;

[0007] The air conditioning unit compressor mode low load control method further comprises the following steps:

[0008] S1, real-time detection of whether the air-conditioning unit meets the conditions for entering low-load control;

[0009] S2: If the low-load control conditions are met, the low-load regulation mode is entered;

[0010] S3, in the low-load adjustment mode, real-time detection of whether the air-conditioning unit meets the conditions for exiting the low-load control;

[0011] S4. If the conditions for exiting low-load control are met, enter low-load exit mode.

[0012] The present invention is further configured such that the air-conditioning unit also includes a gas-liquid separator; the other end of the first evaporator and the other end of the second evaporator are respectively connected to one end of the gas-liquid separator; the other end of the first compressor and the other end of the second compressor are respectively connected to the other end of the gas-liquid separator.

[0013] The present invention is further configured such that a first temperature sensor is provided at the other end of the first evaporator; a second temperature sensor is provided at the other end of the second evaporator; a first pressure sensor is provided at one end of the gas-liquid separator; and a second pressure sensor is provided at the other end of the condenser.

[0014] The present invention is further configured that the condition for entering low load control includes:

[0015] During the continuous low-load detection time T1, the operating frequency of the first compressor and the operating frequency of the second compressor are ≤ the preset value of the compressor operating frequency, the cooling demand is < the low-load control enters the preset value of the cooling demand, and the actual supply air temperature is < the first preset value of the supply air temperature.

[0016] The present invention is further configured that the condition for exiting low-load control includes:

[0017] During the continuous low-load detection time T2, the cooling demand ≥ the low-load control exit cooling demand preset value, or the actual supply air temperature ≥ the second supply air temperature setting value.

[0018] The present invention is further configured that the low load regulation mode comprises the following steps:

[0019] A1. Turn off the second compressor and keep the first compressor running;

[0020] A2. Increase the target condensing pressure, reduce the exhaust fan speed, and increase the actual condensing pressure;

[0021] A3. Increase the target suction superheat, reduce the opening of the first electronic expansion valve and the second electronic expansion valve to increase the actual suction superheat;

[0022] A4. Close the second electronic expansion valve to reduce the heat exchange area of ​​the evaporator.

[0023] The present invention is further configured that the step of increasing the target condensing pressure and reducing the exhaust fan speed to increase the actual condensing pressure comprises:

[0024] After completely shutting down the first compressor, delay the low-load control time interval T3, stop the automatic adjustment of the target condensing pressure, gradually increase the target condensing pressure to the upper limit of the condensing pressure according to the set value, the actual condensing pressure responds to the increase in demand, and controls the exhaust fan speed to gradually decrease until the target condensing pressure reaches the upper limit of the condensing pressure, and stops increasing and maintains it.

[0025] The present invention is further configured that the increasing the target suction superheat, reducing the opening of the first electronic expansion valve and the opening of the second electronic expansion valve, and increasing the actual suction superheat comprises:

[0026] After the target condensing pressure reaches the upper limit of the condensing pressure, the low-load control time interval T4 is delayed, and the target suction superheat is gradually increased to the upper limit of the suction superheat according to the set value. The actual suction superheat responds to the increase in demand, and the first electronic expansion valve and the second electronic expansion valve are controlled to gradually close the opening to reduce the refrigerant flowing into the first evaporator and the second evaporator. The target suction superheat stops increasing and is maintained when it reaches the upper limit of the suction superheat.

[0027] The present invention is further configured such that closing the second electronic expansion valve to reduce the heat exchange area of ​​the evaporator comprises:

[0028] After the target suction superheat reaches the upper limit of the suction superheat, the low-load control time interval T5 is delayed, the second electronic expansion valve is closed to the minimum opening and then completely closed, the corresponding second evaporator does not participate in heat exchange, and the first electronic expansion valve adjusts the refrigerant flow according to the target suction superheat.

[0029] The present invention is further configured that the low-load exit mode comprises the following steps:

[0030] The target condensing pressure is automatically adjusted to restore the initial value of the target suction superheat, the second electronic expansion valve that has been closed is opened, and it is automatically determined whether to open the second compressor that has been closed according to the refrigeration demand.

[0031] Beneficial effects of the present invention: When the air-conditioning unit meets the conditions for entering low-load control, that is, when the heat load is very small, the air-conditioning cooling output can be minimized by controlling the sequence of shutting down one of the compressors, increasing the condensing pressure, increasing the superheat, and shutting down an electronic expansion valve, thereby effectively solving problems such as frequent start and stop of the compressor and large fluctuations in indoor temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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.

[0033] Figure 1 It is a system principle diagram of the present invention;

[0034] Figure 2 It is a structural principle diagram of the air conditioning unit of the present invention;

[0035] Among them: 11, the first compressor; 12, the second compressor; 2, the condenser; 21, the exhaust fan; 31, the first electronic expansion valve; 32, the second electronic expansion valve; 41, the first evaporator; 42, the second evaporator; 43, the blower; 5, the gas-liquid separator; 61, the first temperature sensor; 62, the second temperature sensor; 7, the first pressure sensor; 8, the second pressure sensor. DETAILED DESCRIPTION

[0036] The present invention is further described in conjunction with the following examples.

[0037] Depend on Figure 1 to Figure 2 It can be seen that the low-load control method of the compressor mode of an air-conditioning unit described in this embodiment includes an air-conditioning unit; the air-conditioning unit includes a first compressor 11, a second compressor 12, a condenser 2, a first electronic expansion valve 31, a second electronic expansion valve 32, a first evaporator 41 and a second evaporator 42;

[0038] The first compressor 11 is connected in parallel with the second compressor 12; one end of the first compressor 11 is connected to one end of the condenser 2; the other end of the condenser 2 is connected to one end of the first evaporator 41 through the first electronic expansion valve 31; the other end of the first evaporator 41 is connected to the other end of the first compressor 11; the other end of the condenser 2 is connected to one end of the second evaporator 42 through the second electronic expansion valve 32; the other end of the second evaporator 42 is connected to the other end of the first compressor 11; an exhaust fan 21 is provided at the condenser 2; and a blower 43 is provided at the first evaporator 41 and the second evaporator 42;

[0039] The air conditioning unit compressor mode low load control method further comprises the following steps:

[0040] S1, real-time detection of whether the air-conditioning unit meets the conditions for entering low-load control;

[0041] S2: If the low-load control conditions are met, the low-load regulation mode is entered;

[0042] S3, in the low-load adjustment mode, real-time detection of whether the air-conditioning unit meets the conditions for exiting the low-load control;

[0043] S4. If the conditions for exiting low-load control are met, enter low-load exit mode.

[0044] Specifically, the air-conditioning unit compressor mode low-load control method described in this embodiment, by setting two compressors, two electronic expansion valves and two evaporators, in a dual compressor parallel connection, dual electronic expansion valves and dual evaporators, the high-pressure refrigerant from the condenser 2 is divided into two paths and enters the first electronic expansion valve 31 and the second electronic expansion valve 32 respectively for throttling and pressure reduction, and then enters the first evaporator 41 and the second evaporator 42 respectively, and then merges into one path after coming out, and then passes through the gas-liquid separator 5 and is divided into two paths to enter the first compressor 11 and the second compressor 12 for compression.

[0045] In the non-low-load control mode, the frequencies of the first compressor 11 and the second compressor 12 are automatically adjusted according to the cooling demand, the openings of the first electronic expansion valve 31 and the second electronic expansion valve 32 are automatically adjusted according to their respective suction superheats, and the speed of the exhaust fan 21 is automatically adjusted according to the condensing pressure.

[0046] When the air-conditioning unit meets the conditions for entering low-load control, that is, when the heat load is very small, it enters the low-load adjustment mode. By shutting down one of the compressors, increasing the condensing pressure, increasing the superheat and closing an electronic expansion valve in this control sequence, the air-conditioning cooling output can be minimized, effectively solving problems such as frequent start and stop of the compressor and large fluctuations in indoor temperature. In addition, during the low-load adjustment mode, it is detected in real time whether the air-conditioning unit meets the conditions for exiting the low-load control. When the conditions for exiting the low-load control are met, the air-conditioning unit enters the low-load exit mode, thereby automatically exiting the low-load adjustment mode.

[0047] In the low-load control method of the compressor mode of an air-conditioning unit described in this embodiment, the air-conditioning unit further includes a gas-liquid separator 5; the other end of the first evaporator 41 and the other end of the second evaporator 42 are respectively connected to one end of the gas-liquid separator 5; the other end of the first compressor 11 and the other end of the second compressor 12 are respectively connected to the other end of the gas-liquid separator 5. The above arrangement can ensure the stability of the first compressor 11 and the second compressor 12.

[0048] In the present embodiment, a method for controlling the low-load mode of the compressor of an air-conditioning unit is described, wherein a first temperature sensor 61 is provided at the other end of the first evaporator 41; a second temperature sensor 62 is provided at the other end of the second evaporator 42; a first pressure sensor 7 is provided at one end of the gas-liquid separator 5; and a second pressure sensor 8 is provided at the other end of the condenser 2.

[0049] Specifically, the present embodiment can calculate the suction saturation temperature according to the pressure value of the first pressure sensor 7 by setting the first pressure sensor 7, and can detect the suction temperature at the first evaporator 41 and the suction temperature at the second evaporator 42 respectively by the first temperature sensor 61 and the second temperature sensor 62; by subtracting the suction temperature from the suction saturation temperature, the suction superheat corresponding to the first evaporator 41 and the suction superheat corresponding to the second evaporator 42 can be calculated respectively.

[0050] In addition, by providing the second pressure sensor 8, the condensing pressure of the air-conditioning unit can be detected.

[0051] In the present embodiment, a method for controlling a compressor mode of an air-conditioning unit in low load mode is provided, wherein the conditions for entering low load control include:

[0052] During the continuous low-load detection time T1, the operating frequency of the first compressor 11 and the operating frequency of the second compressor 12 are ≤ the preset value of the compressor operating frequency, the cooling demand is < the preset value of the low-load control entering the cooling demand, and the actual supply air temperature is < the first preset value of the supply air temperature. When all the above conditions are met, it means that the air conditioning unit is currently in an environment with a very small heat load, so it needs to enter the low-load adjustment mode.

[0053] In the present embodiment, a method for controlling a compressor mode of an air-conditioning unit under low load is provided, wherein the condition for exiting the low load control comprises:

[0054] During the continuous low-load detection time T2, the cooling demand ≥ the low-load control exit cooling demand preset value, or the actual supply air temperature ≥ the second supply air temperature setting value. When one of the above conditions is met, it means that the air conditioning unit is no longer in an environment with a very small heat load, so there is no need to enter the low-load adjustment mode.

[0055] The present embodiment provides a method for controlling a compressor mode of an air-conditioning unit in a low-load mode, wherein the low-load adjustment mode comprises the following steps:

[0056] A1. Turn off the second compressor 12, and keep the first compressor 11 running;

[0057] A2. Increase the target condensing pressure and reduce the speed of the exhaust fan 21 to increase the actual condensing pressure;

[0058] A3. Increase the target suction superheat, reduce the opening of the first electronic expansion valve 31 and the opening of the second electronic expansion valve 32, so that the actual suction superheat increases;

[0059] A4. Close the second electronic expansion valve 32 to reduce the heat exchange area of ​​the evaporator.

[0060] In the present embodiment, a method for controlling a compressor mode of an air-conditioning unit under low load is described, wherein the target condensing pressure is increased, the speed of the exhaust fan 21 is reduced, and the actual condensing pressure is increased, including:

[0061] After completely shutting down the first compressor 11, the low-load control time interval T3 is delayed, the automatic adjustment of the target condensing pressure is stopped, and the target condensing pressure is gradually increased to the upper limit of the condensing pressure at 1 bar / condensing pressure adjustment cycle. The actual condensing pressure increases in response to demand, and the speed of the exhaust fan 21 is controlled to gradually decrease until the target condensing pressure reaches the upper limit of the condensing pressure, and the increase is stopped and maintained.

[0062] In the present embodiment, a method for controlling a compressor mode of an air-conditioning unit under low load is described, wherein the target suction superheat is increased, the opening of the first electronic expansion valve 31 and the opening of the second electronic expansion valve 32 are reduced, and the actual suction superheat is increased, including:

[0063] After the target condensing pressure reaches the upper limit of the condensing pressure, the low-load control time interval T4 is delayed, and the target suction superheat is gradually increased to the upper limit of the suction superheat according to 1°C / superheat adjustment cycle. The actual suction superheat responds to the increase in demand, and the first electronic expansion valve 31 and the second electronic expansion valve 32 are controlled to gradually close their openings to reduce the refrigerant flowing into the first evaporator 41 and the second evaporator 42. The target suction superheat stops increasing and is maintained until it reaches the upper limit of the suction superheat.

[0064] In the low-load control method for the compressor mode of an air-conditioning unit described in this embodiment, closing the second electronic expansion valve 32 to reduce the heat exchange area of ​​the evaporator includes:

[0065] After the target suction superheat reaches the upper limit of the suction superheat, the low-load control time interval T5 is delayed, and the second electronic expansion valve 32 is closed to the minimum opening and then completely closed. The corresponding second evaporator 42 does not participate in heat exchange, and the first electronic expansion valve 31 adjusts the refrigerant flow according to the target suction superheat.

[0066] Through the above control, this embodiment allows the air-conditioning unit to output a smaller cooling capacity without shutting down all compressors, meeting the use of scenarios with very small heat loads and solving the problem of frequent start and stop of compressors.

[0067] In the present embodiment, a method for controlling a compressor mode of an air-conditioning unit under low load is provided, wherein the low load exit mode comprises the following steps:

[0068] The target condensing pressure is automatically adjusted to restore the initial value of the target suction superheat, the closed second electronic expansion valve 32 is opened, and it is automatically determined whether to open the closed second compressor 12 according to the refrigeration demand.

[0069] 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 method for controlling low load of compressor mode of an air-conditioning unit, characterized in that: An air conditioning unit is provided; the air conditioning unit comprises a first compressor (11), a second compressor (12), a condenser (2), a first electronic expansion valve (31), a second electronic expansion valve (32), a first evaporator (41) and a second evaporator (42); The first compressor (11) and the second compressor (12) are connected in parallel; one end of the first compressor (11) is connected to one end of the condenser (2); the other end of the condenser (2) is connected to one end of the first evaporator (41) through a first electronic expansion valve (31); the other end of the first evaporator (41) is connected to the other end of the first compressor (11); the other end of the condenser (2) is connected to one end of the second evaporator (42) through a second electronic expansion valve (32); the other end of the second evaporator (42) is connected to the other end of the first compressor (11); an exhaust fan (21) is provided at the condenser (2); and air supply fans (43) are provided at the first evaporator (41) and the second evaporator (42); The air conditioning unit compressor mode low load control method further comprises the following steps: S1, real-time detection of whether the air-conditioning unit meets the conditions for entering low-load control; S2: If the low-load control conditions are met, the low-load regulation mode is entered; S3, in the low-load adjustment mode, real-time detection of whether the air-conditioning unit meets the conditions for exiting the low-load control; S4. If the conditions for exiting low-load control are met, enter low-load exit mode.

2. The method for controlling low load of compressor mode of an air-conditioning unit according to claim 1, characterized in that: The air conditioning unit further comprises a gas-liquid separator (5); the other end of the first evaporator (41) and the other end of the second evaporator (42) are respectively connected to one end of the gas-liquid separator (5); the other end of the first compressor (11) and the other end of the second compressor (12) are respectively connected to the other end of the gas-liquid separator (5).

3. The method for controlling low load of compressor mode of an air-conditioning unit according to claim 2, characterized in that: The other end of the first evaporator (41) is provided with a first temperature sensor (61); the other end of the second evaporator (42) is provided with a second temperature sensor (62); one end of the gas-liquid separator (5) is provided with a first pressure sensor (7); and the other end of the condenser (2) is provided with a second pressure sensor (8).

4. The method for controlling low load of compressor mode of an air-conditioning unit according to claim 1, characterized in that: The conditions for entering low load control include: During the continuous low-load detection time T1, the operating frequency of the first compressor (11) and the operating frequency of the second compressor (12) are ≤ the preset values ​​of the compressor operating frequencies, the refrigeration demand is < the low-load control enters the refrigeration demand preset value, and the actual supply air temperature is < the first supply air temperature preset value.

5. The low-load control method for compressor mode of an air-conditioning unit according to claim 1, characterized in that: The conditions for exiting low load control include: During the continuous low-load detection time T2, the cooling demand ≥ the low-load control exit cooling demand preset value, or the actual supply air temperature ≥ the second supply air temperature setting value.

6. The method for controlling low load of compressor mode of an air-conditioning unit according to claim 3, characterized in that: The low load regulation mode comprises the following steps: A1. Turn off the second compressor (12), and keep the first compressor (11) running; A2. Raising the target condensing pressure and reducing the speed of the exhaust fan (21) to increase the actual condensing pressure; A3, increasing the target suction superheat, reducing the opening of the first electronic expansion valve (31) and the opening of the second electronic expansion valve (32), so that the actual suction superheat increases; A4. Close the second electronic expansion valve (32) to reduce the heat exchange area of ​​the evaporator.

7. The method for controlling low load of compressor mode of an air-conditioning unit according to claim 6, characterized in that: The step of increasing the target condensing pressure and reducing the rotation speed of the exhaust fan (21) to increase the actual condensing pressure comprises: After the first compressor (11) is completely shut down, the low-load control time interval T3 is extended, the automatic adjustment of the target condensing pressure is stopped, and the target condensing pressure is gradually increased to the upper limit of the condensing pressure according to the set value. The actual condensing pressure increases in response to the demand, and the speed of the exhaust fan (21) is controlled to gradually decrease until the target condensing pressure reaches the upper limit of the condensing pressure, and the increase is stopped and maintained.

8. The method for controlling low load of compressor mode of an air-conditioning unit according to claim 7, characterized in that: The step of increasing the target suction superheat, reducing the opening of the first electronic expansion valve (31) and the opening of the second electronic expansion valve (32), and increasing the actual suction superheat comprises: After the target condensing pressure reaches the upper limit of the condensing pressure, the low-load control time interval T4 is delayed, and the target suction superheat is gradually increased to the upper limit of the suction superheat according to the set value. The actual suction superheat responds to the increase in demand, and the first electronic expansion valve (31) and the second electronic expansion valve (32) are controlled to gradually close their openings, so that the refrigerant flowing into the first evaporator (41) and the second evaporator (42) is reduced, until the target suction superheat reaches the upper limit of the suction superheat, and the increase is stopped and maintained.

9. The method for controlling low load of compressor mode of an air-conditioning unit according to claim 8, characterized in that: Closing the second electronic expansion valve (32) to reduce the heat exchange area of ​​the evaporator includes: After the target suction superheat reaches the upper limit of the suction superheat, the low-load control time interval T5 is delayed, the second electronic expansion valve (32) is closed to the minimum opening and then completely closed, the corresponding second evaporator (42) does not participate in heat exchange, and the refrigerant flow is adjusted by the first electronic expansion valve (31) according to the target suction superheat.

10. The low-load control method for compressor mode of an air-conditioning unit according to claim 3, characterized in that: The low load exit mode comprises the following steps: The target condensing pressure is automatically adjusted to restore the initial value of the target suction superheat, the closed second electronic expansion valve (32) is opened, and it is automatically determined whether to open the closed second compressor (12) according to the refrigeration demand.

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