Air conditioning system and control method thereof

Abstract

The present invention provides an air-conditioning system and a control method thereof. The air-conditioning system includes a first compressor and a second compressor. The control method includes the following steps: a single-compressor control step of adjusting the operating frequency of the first compressor according to a control instruction; a data acquisition step of detecting the high-pressure pressure, the exhaust temperature, and the operating frequency of the first compressor; a second-compressor starting step. After receiving the control instruction for starting both compressors, while keeping the operating frequency of the first compressor stable, open a second pressure relief valve communicating with the exhaust port of the second compressor for a first duration and then start the second compressor. After the second compressor operates at the starting operating frequency of the second compressor for a second duration with the pressure relief valve open, close the second pressure relief valve. In the second-compressor starting step, the starting operating frequency of the second compressor is related to the high-pressure pressure, the exhaust temperature, and the operating frequency of the first compressor.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning systems, and particularly to a dual-compressor air conditioning system and a control method for an air conditioning system. Background Art

[0002] In the prior art, there is a dual-compressor air conditioning system. When the energy demand in the air conditioning system is small, only one compressor can be started. When the energy demand in the air conditioning system increases, two compressors can be started simultaneously to meet the user's needs. For the dual-compressor air conditioning system in the prior art, when it is necessary to switch from the single-compressor mode to the dual-compressor mode, that is, when it is necessary to start another compressor while one compressor is running, generally, the frequency of the compressor that is running needs to be reduced first so that the other compressor can be started normally, and then the two compressors perform a frequency increase operation according to a preset logic. During the process of switching from the single-compressor mode to the dual-compressor mode in the above dual-compressor air conditioning system, the frequency of the compressor fluctuates frequently, which makes the cooling capacity or heating capacity of the air conditioning system unstable, thus causing energy waste.

[0003] Therefore, how to provide an air conditioning system and its control method, so that the dual-compressor air conditioning system can complete the mutual switching between the single-compressor mode and the dual-compressor mode, and at the same time, avoid the frequent fluctuation of the compressor frequency as much as possible, thereby avoiding energy waste, is a technical problem faced by the prior art. Summary of the Invention

[0004] In view of the above problems, the present invention provides an air conditioning system and a control method therefor, so that the dual-compressor air conditioning system can complete the mutual switching between the single-compressor mode and the dual-compressor mode, and at the same time, avoid the frequent fluctuation of the compressor frequency as much as possible, thereby avoiding energy waste.

[0005] The control method of the air conditioning system provided by the present invention, wherein the air conditioning system includes a first compressor and a second compressor, and the control method includes the following steps: a single-compressor control step of adjusting the operating frequency of the first compressor according to a control instruction; a data acquisition step of detecting the high-pressure pressure, the exhaust temperature, and the operating frequency of the first compressor; a second-compressor starting step of, after receiving a control instruction for starting two compressors, starting the second compressor after opening a second pressure relief valve communicating with the exhaust port of the second compressor for a first period of time while keeping the operating frequency of the first compressor stable, and making the second compressor operate at a second-compressor starting operating frequency for a second period of time with the second pressure relief valve open, and then closing the second pressure relief valve; in the second-compressor starting step, the second-compressor starting operating frequency is related to the high-pressure pressure, the exhaust temperature, and the operating frequency of the first compressor.

[0006] According to the control method of the air-conditioning system provided by the present invention, since it includes the step of opening a second pressure relief valve communicating with the exhaust port of the second compressor for a first duration before starting the second compressor and operating the second compressor for a second duration while the second pressure relief valve is open, and the second pressure relief valve can play a role in balancing the pressure difference between the suction port and the exhaust port of the second compressor. Therefore, in the state where the second pressure relief valve is open, even if the operating frequency of the first compressor is not significantly reduced, the second compressor can be smoothly started and operated, avoiding frequent fluctuations in the operating frequency of the first compressor during the starting step of the second compressor and in the dual-compressor mode after the starting step of the second compressor.

[0007] Since it includes a data acquisition step, the starting and operating frequency of the second compressor matching the current working condition of the air-conditioning system can be obtained according to the detected high-pressure pressure, exhaust temperature, and the operating frequency of the first compressor. Thus, the second compressor can be smoothly started and operated at the starting and operating frequency of the second compressor. At the same time, the second compressor operating at the starting and operating frequency of the second compressor can reasonably control the cooling capacity or heating capacity output by the air-conditioning system, and further facilitate the air-conditioning system to enter a stable operating state faster after switching to the dual-compressor mode. In other words, after switching to the dual-compressor mode, the operating frequencies of the first compressor and the second compressor are not likely to fluctuate frequently, and the purpose of saving energy can be achieved.

[0008] Preferably, in the starting step of the second compressor, the starting and operating frequency of the second compressor is a fixed value. That is, after receiving the control instruction for the dual-compressor, the starting and operating frequency of the second compressor is obtained according to the currently detected high-pressure pressure, exhaust temperature, and the operating frequency of the first compressor. In this way, it is beneficial to simplify the control and improve the stability of the air-conditioning system.

[0009] Preferably, in the starting step of the second compressor, the stable operating frequency of the first compressor means keeping the operating frequency of the first compressor unchanged or keeping the change range of the operating frequency of the first compressor between plus and minus 2 Hz.

[0010] In the control method of the air-conditioning system of the optional technical solution of the present invention, after the starting step of the second compressor, it further includes: a dual-compressor control step of adjusting the operating frequencies of the first compressor and the second compressor according to the control instruction.

[0011] In the above preferred technical solutions, since a dual-compressor control step is included after the second compressor startup step, the control logic in the dual-compressor control step can be different from the control logic in the second compressor startup step, so that after the air-conditioning system switches to the dual-compressor mode, the operating frequencies of the first compressor and the second compressor can be controlled with a more reasonable control logic, and then the cooling capacity or heating capacity output by the air-conditioning system can be reasonably controlled to achieve the purpose of energy conservation.

[0012] In the control method of the air-conditioning system according to the optional technical solution of the present invention, after the dual-compressor control step, it further includes: a second compressor shutdown step. After receiving the control instruction for single-compressor operation, the second compressor is shut down while keeping the operating frequency of the first compressor stable. After the second compressor is shut down, the second pressure relief valve is opened for a third duration.

[0013] In the above preferred technical solutions, since the second compressor is shut down while keeping the operating frequency of the first compressor stable, it is possible to avoid frequent fluctuations in the operating frequency of the first compressor during the second compressor shutdown step. Since the second pressure relief valve is opened for a third duration after the second compressor is shut down, the pressure difference between the suction port and the discharge port of the second compressor after shutdown can be balanced.

[0014] Preferably, in the second compressor shutdown step, keeping the operating frequency of the first compressor stable means keeping the operating frequency of the first compressor unchanged or keeping the change range of the operating frequency of the first compressor between plus and minus 2 Hz.

[0015] In the control method of the air-conditioning system according to the optional technical solution of the present invention, in the data acquisition step, it further includes a step of detecting the operating frequency of the second compressor; and after the dual-compressor control step, the control method further includes: a first compressor shutdown step. After receiving the control instruction for single-compressor operation, the first compressor is shut down while keeping the operating frequency of the second compressor stable. After the first compressor is shut down, the first pressure relief valve communicated with the discharge port of the first compressor is opened for a third duration.

[0016] In the above preferred technical solutions, since it includes a first compressor shutdown step, that is, the first compressor that has been started and operated for a longer time is selected to be shut down between the first compressor and the second compressor to balance the total startup and operation duration of the first compressor and the second compressor, which is beneficial to the long-term stable operation of the air-conditioning system.

[0017] Preferably, in the first compressor shutdown step, keeping the operating frequency of the second compressor stable means keeping the operating frequency of the second compressor unchanged or keeping the change range of the operating frequency of the second compressor between plus and minus 2 Hz.

[0018] In the control method of the air-conditioning system according to the optional technical solution of the present invention, the starting and operating frequency of the second compressor is negatively correlated with the high-pressure pressure, negatively correlated with the exhaust temperature, and positively correlated with the operating frequency of the first compressor.

[0019] In the above preferred technical solution, since the starting and operating frequency of the second compressor is negatively correlated with the high-pressure pressure, when the high-pressure pressure is relatively high, that is, when the starting load of the second compressor is relatively large, the starting and operating frequency of the second compressor can be made smaller, so that the second compressor can start smoothly. Since the starting and operating frequency of the second compressor is negatively correlated with the exhaust temperature, when the exhaust temperature is relatively high, that is, when the starting load of the second compressor is relatively large, the starting and operating frequency of the second compressor can be made smaller, so that the second compressor can start smoothly. Since the starting and operating frequency of the second compressor is positively correlated with the operating frequency of the first compressor, when the operating frequency of the first compressor is relatively large, that is, when the energy demand of the air-conditioning system is relatively large, the starting and operating frequency of the second compressor can also be made larger, so that after the air-conditioning system is switched to the dual-compressor mode, it can enter the stable operating state faster. In other words, after being switched to the dual-compressor mode, the operating frequencies of the first compressor and the second compressor are not likely to fluctuate frequently, which is beneficial to achieving the purpose of energy conservation.

[0020] In the control method of the air-conditioning system according to the optional technical solution of the present invention, in the data acquisition step, it includes: a step of calculating the superheat degree of the exhaust gas; the starting and operating frequency of the second compressor is negatively correlated with the superheat degree of the exhaust gas.

[0021] In the above preferred technical solution, since the starting and operating frequency of the second compressor is negatively correlated with the superheat degree of the exhaust gas, when the superheat degree of the exhaust gas is relatively large, that is, when the exhaust temperature is relatively high or the high-pressure pressure is relatively low, the starting and operating frequency of the second compressor can be made smaller, so as to avoid as much as possible the situation that the second compressor cannot start smoothly due to the relatively high exhaust temperature and the relatively large starting load of the second compressor.

[0022] Preferably, the step of calculating the superheat degree of the exhaust gas specifically includes: subtracting the saturation temperature corresponding to the high-pressure pressure from the exhaust temperature.

[0023] In the control method of the air-conditioning system according to the optional technical solution of the present invention, in the second compressor starting step, the starting and operating frequency of the second compressor is calculated by the following formula: Starting and operating frequency of the second compressor = oil return correction coefficient * operating frequency of the first compressor / high-pressure pressure - superheat degree of the exhaust gas / (pi * oil return correction coefficient).

[0024] In the above preferred technical solution, since the starting and operating frequency of the second compressor is obtained by formula calculation, it is realized to intelligently determine the starting and operating frequency of the second compressor according to the working conditions of the air-conditioning system, which is beneficial to achieving the purpose of energy conservation.

[0025] Among them, the value of the oil return correction coefficient is greater than 1 and is negatively correlated with the high-pressure pressure. Preferably, when the high-pressure pressure is greater than 2.8 Mpa, the oil return correction coefficient is 1.1; when the high-pressure pressure is greater than 2.2 Mpa and less than or equal to 2.8 Mpa, the oil return correction coefficient is 1.2; when the high-pressure pressure is less than or equal to 2.2 Mpa, the oil return correction coefficient is 1.35.

[0026] In the control method of the air-conditioning system according to the optional technical solution of the present invention, the first duration is greater than the second duration, and the third duration is greater than the first duration.

[0027] In the above preferred technical solution, since the first duration is greater than the second duration, that is, in the second compressor startup step, the duration for which the pressure relief valve is opened before the second compressor starts is longer, which is beneficial to balancing the pressure difference between the suction port and the discharge port of the second compressor and ensuring that the second compressor can start smoothly. And the duration for which the pressure relief valve is opened after the second compressor starts is shorter, which is beneficial to enabling the air-conditioning system to enter a stable operating state faster, so as to improve the user experience. Since the third duration is greater than the first duration, it is beneficial to balance the pressure difference between the suction port and the discharge port of the second compressor after the second compressor shuts down, and generally, the longer third duration does not affect the user experience either.

[0028] Preferably, the values of the first duration, the second duration, and the third duration are all between 0.5 minutes and 5 minutes.

[0029] The present invention also provides an air-conditioning system, which can be controlled by using the control method mentioned above. The air-conditioning system includes a first compressor, an oil separator, a reversing valve, an outdoor heat exchanger, a throttling device, an indoor heat exchanger, and a gas-liquid separation device that are connected in sequence. A first exhaust temperature detection device is provided at the exhaust port of the first compressor, and a first pressure relief valve is provided between the first compressor and the gas-liquid separation device. The air-conditioning system further includes: a second compressor, which is connected in parallel with the first compressor, a second exhaust temperature detection device is provided at the exhaust port of the second compressor, and a second pressure relief valve is provided between the second compressor and the gas-liquid separation device; a high-pressure pressure detection device, which is provided between the oil separator and the reversing valve. Description of the Drawings

[0030] Figure 1 and Figure 2 is a schematic flow chart of the control method of the air-conditioning system in the embodiment of the present invention;

[0031] Figure 3 is a schematic structural diagram of the air-conditioning system in the embodiment of the present invention;

[0032] Reference Signs:

[0033] Air conditioning system 100, first compressor 1, first exhaust temperature detection device 11, first pressure relief valve 12, first exhaust check valve 13, second compressor 2, second exhaust temperature detection device 21, second pressure relief valve 22, second exhaust check valve 23, oil separator 3, oil return capillary 31, reversing valve 4, outdoor heat exchanger 51, fan 52, ambient temperature detection device 53, heat exchanger outlet temperature detection device 54, throttling device 6, indoor unit 7, gas-liquid separation device 8, high-pressure pressure detection device 9, low-pressure pressure detection device 10, low-pressure stop valve 16, high-pressure stop valve 17.

[0034] High-pressure pressure P, exhaust temperature Tp, saturation temperature Ts, exhaust superheat Dsh, first compressor operating frequency Fa, second compressor operating frequency Fb, second compressor starting operating frequency F0, timer T, first duration t1, second duration t2, third duration t3. Detailed implementation manner

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] As Figure 1 and Figure 3 shown, a control method for an air conditioning system is provided in this embodiment. On the premise that the dual-compressor air conditioning system 100 can complete the mutual switching between the single-compressor mode and the dual-compressor mode, the frequency of the compressor is prevented from fluctuating frequently, thereby avoiding energy waste. The air conditioning system 100 includes a first compressor 1 and a second compressor 2. The control method includes the following steps: a single-compressor control step of adjusting the first compressor operating frequency Fa according to a control instruction; a data acquisition step of detecting the high-pressure pressure P, the exhaust temperature Tp, the first compressor operating frequency Fa, and the second compressor operating frequency Fb; a second compressor starting step. After receiving the control instruction for starting the dual-compressor, while keeping the first compressor operating frequency Fa stable, open the second pressure relief valve 22 communicating with the exhaust port of the second compressor 2 for a first duration t1, then start the second compressor 2, and make the second compressor 2 operate at the second compressor starting operating frequency F0 for a second duration t2 while the second pressure relief valve 22 is open, and then close the second pressure relief valve 22; in the second compressor starting step, the second compressor starting operating frequency F0 is related to the high-pressure pressure P, the exhaust temperature Tp, and the first compressor operating frequency Fa.

[0037] In some other embodiments, the types of parameters obtained in the data acquisition step and the ways of obtaining the parameters can be selected according to actual requirements. For example, when the second compressor 2 is not started, the parameter of the operating frequency Fb of the second compressor may not be obtained.

[0038] In this embodiment, since it includes the step of opening the second pressure relief valve 22 communicating with the exhaust port of the second compressor 2 for the first duration t1 before starting the second compressor, and making the second compressor 2 operate for the second duration t2 in the state where the second pressure relief valve 22 is opened. And the second pressure relief valve 22 can play a role in balancing the pressure difference between the suction port and the exhaust port of the second compressor 2. Therefore, in the state where the second pressure relief valve 22 is opened, even if the operating frequency Fa of the first compressor is not greatly reduced, the second compressor 2 can be smoothly started and operated, avoiding the frequent fluctuation of the operating frequency Fa of the first compressor in the second compressor starting step and in the dual-compressor operation mode after the second compressor starting step.

[0039] In this embodiment, since it includes a data acquisition step, the starting and operating frequency F0 of the second compressor that matches the current working condition of the air-conditioning system 100 can be obtained according to the detected high-pressure pressure P, exhaust temperature Tp, and the operating frequency Fa of the first compressor. Thus, the second compressor 2 can be smoothly started and operated at the starting and operating frequency F0 of the second compressor in the current working condition of the air-conditioning system 100. At the same time, the second compressor 2 operating at the starting and operating frequency F0 of the second compressor can reasonably control the cooling capacity or heating capacity output by the air-conditioning system 100, and further is beneficial to the air-conditioning system 100 entering a stable operating state faster after switching to the dual-compressor operation mode. In other words, after switching to the dual-compressor operation mode, the operating frequency Fa of the first compressor and the operating frequency Fb of the second compressor are not likely to fluctuate frequently, and thus the purpose of saving energy can be achieved.

[0040] In this embodiment, in the second compressor starting step, the starting and operating frequency F0 of the second compressor is a fixed value. That is, after receiving the control instruction for the dual-compressor, the starting and operating frequency F0 of the second compressor is obtained according to the currently detected high-pressure pressure P, exhaust temperature Tp, and the operating frequency Fa of the first compressor. In this way, the control can be simplified, which is beneficial to the stable operation of the air-conditioning system 100.

[0041] In some other embodiments, in the second compressor starting step, the starting and operating frequency F0 of the second compressor can also be a variable value within a certain range.

[0042] In this embodiment, in the second compressor starting step, the stability of the operating frequency Fa of the first compressor means keeping the operating frequency Fa of the first compressor unchanged.

[0043] In some other embodiments, the stable operation frequency Fa of the first compressor may also mean that the variation range of the operation frequency Fa of the first compressor is maintained between plus and minus 2 Hz.

[0044] In this embodiment, after the second pressure relief valve 22 is opened, the timer T starts. When T ≥ the first duration t1, the second compressor 2 starts. At this time, the timer T restarts, that is, after the timer T is cleared, it starts timing again. When T ≥ the second duration t2, the second pressure relief valve 22 closes.

[0045] In this embodiment, the first duration t1 is greater than the second duration t2. That is, in the step of starting the second compressor, the opening duration of the second pressure relief valve 22 before the second compressor 2 starts is longer, which is beneficial to balancing the pressure difference between the suction port and the discharge port of the second compressor 2 and ensuring that the second compressor 2 can start smoothly. And the opening duration of the second pressure relief valve 22 after the second compressor 2 starts is shorter, which is beneficial to enabling the air-conditioning system 100 to enter a stable operation state faster, so as to improve the user experience.

[0046] In some other embodiments, the values of the first duration t1 and the second duration t2 can be adjusted according to different air-conditioning systems 100. In addition, the specific control method of the timer T can also be adjusted according to requirements. For example, a continuous timing method can be adopted.

[0047] In this embodiment, after the step of starting the second compressor, it further includes: a dual-compressor control step of adjusting the operation frequency Fa of the first compressor and the operation frequency Fb of the second compressor according to a control instruction. Since a dual-compressor control step is included after the step of starting the second compressor, and the control logic in the dual-compressor control step is different from the control logic in the step of starting the second compressor, the air-conditioning system 100 can control the operation frequency Fa of the first compressor and the operation frequency Fb of the second compressor with a more reasonable control logic after switching to the dual-compressor mode, and then reasonably control the cooling capacity or heating capacity output by the air-conditioning system 100 to achieve the purpose of saving energy.

[0048] In this embodiment, after the dual-compressor control step, it further includes: a second-compressor shutdown step. After receiving a single-compressor control instruction, the second compressor 2 is shut down while keeping the operation frequency Fa of the first compressor unchanged. After the second compressor 2 is shut down, the second pressure relief valve 22 is opened for a third duration t3. Since the second compressor 2 is shut down while keeping the operation frequency Fa of the first compressor stable, it can avoid frequent fluctuations of the operation frequency Fa of the first compressor in the second-compressor shutdown step. Since the second pressure relief valve 22 is opened for a third duration t3 after the second compressor 2 is shut down, it can balance the pressure difference between the suction port and the discharge port of the second compressor 2 after the second compressor 2 is shut down.

[0049] In this embodiment, the third duration t3 is greater than the first duration t1, which is beneficial to balancing the pressure difference between the suction port and the discharge port of the second compressor 2 after the second compressor 2 is shut down, and generally, a relatively long third duration t3 does not affect the user experience.

[0050] In this embodiment, in the step of shutting down the second compressor, keeping the operating frequency Fa of the first compressor stable means keeping the operating frequency Fa of the first compressor unchanged.

[0051] In some other embodiments, in the step of shutting down the second compressor, keeping the operating frequency of the first compressor stable means that the change range of the operating frequency Fa of the first compressor is between plus and minus 2 Hz.

[0052] In this embodiment, as Figure 2 shown, after the step of controlling the dual-compressor, it further includes: a step of shutting down the first compressor. After receiving the control instruction for the single-compressor, while keeping the operating frequency Fb of the second compressor stable, the first compressor 1 is shut down. After the first compressor 1 is shut down, the first pressure relief valve 12 communicating with the discharge port of the first compressor 1 is opened for the third duration t3. Since it includes the step of shutting down the first compressor, that is, choosing to shut down the first compressor 1 that has been started and operated for a longer time between the first compressor 1 and the second compressor 2, so as to balance the total start-up and operation durations of the first compressor 1 and the second compressor 2, which is beneficial to the long-term stable operation of the air-conditioning system 100.

[0053] In this embodiment, in the step of shutting down the first compressor, keeping the operating frequency Fb of the second compressor stable means keeping the operating frequency Fb of the second compressor unchanged.

[0054] In some other embodiments, in the step of shutting down the first compressor, keeping the operating frequency Fb of the second compressor stable means that the change range of the operating frequency Fb of the second compressor is between plus and minus 2 Hz.

[0055] Specifically, in this embodiment, when receiving the single-compressor control instruction after the step of controlling the dual-compressor, the air-conditioning system 100 can choose to execute the step of shutting down the second compressor or the step of shutting down the first compressor. For example, the air-conditioning system 100 can choose to execute the step of shutting down the first compressor after having continuously chosen to execute the step of shutting down the second compressor three times in a row or for a continuous week.

[0056] In this embodiment, the starting and operating frequency F0 of the second compressor is negatively correlated with the high-pressure pressure P, negatively correlated with the exhaust temperature Tp, and positively correlated with the operating frequency Fa of the first compressor. Since the starting and operating frequency F0 of the second compressor is negatively correlated with the high-pressure pressure P, when the high-pressure pressure P is relatively large, that is, when the starting load of the second compressor 2 is relatively large, the starting and operating frequency F0 of the second compressor can be made smaller, so that the second compressor 2 can start smoothly. Since the starting and operating frequency F0 of the second compressor is negatively correlated with the exhaust temperature Tp, when the exhaust temperature Tp is relatively high and the starting load of the second compressor 2 is relatively large, the starting and operating frequency F0 of the second compressor can be made smaller, so that the second compressor 2 can start smoothly. Since the starting and operating frequency F0 of the second compressor is positively correlated with the operating frequency Fa of the first compressor, when the operating frequency Fa of the first compressor is relatively large, that is, when the energy demand of the air-conditioning system 100 is relatively large, the starting and operating frequency F0 of the second compressor can also be made larger, so that after the air-conditioning system 100 is switched to the dual-compressor mode, it can enter a stable operating state faster. In other words, after being switched to the dual-compressor mode, the operating frequency Fa of the first compressor and the operating frequency Fb of the second compressor are not likely to fluctuate frequently, which is conducive to achieving the purpose of energy conservation.

[0057] In this embodiment, in the data acquisition step, it includes: a step of calculating the exhaust superheat Dsh; the starting and operating frequency F0 of the second compressor is negatively correlated with the exhaust superheat Dsh. Since the starting and operating frequency F0 of the second compressor is negatively correlated with the exhaust superheat Dsh, when the exhaust superheat Dsh is relatively large, that is, when the exhaust temperature Tp is relatively high or the high-pressure pressure P is relatively low, the starting and operating frequency F0 of the second compressor can be made smaller, so as to avoid as much as possible the situation that the second compressor 2 cannot start smoothly due to the relatively high exhaust temperature Tp and the relatively large starting load of the second compressor 2.

[0058] In this embodiment, the step of calculating the exhaust superheat Dsh specifically includes: subtracting the saturation temperature Ts corresponding to the high-pressure pressure P from the exhaust temperature Tp.

[0059] In this embodiment, in the second compressor starting step, the starting and operating frequency F0 of the second compressor is calculated by the following formula: the starting and operating frequency F0 of the second compressor = the oil return correction coefficient α * the operating frequency Fa of the first compressor / the high-pressure pressure P - the exhaust superheat Dsh / (pi π * the oil return correction coefficient α). Since the starting and operating frequency F0 of the second compressor is obtained by formula calculation, it is realized to intelligently determine the starting and operating frequency F0 of the second compressor according to the working conditions of the adjustment system 100, which is conducive to achieving the purpose of energy conservation. The value of the starting and operating frequency F0 of the second compressor obtained by formula calculation can retain the decimal places according to the actual situation.

[0060] In this embodiment, the value of the oil return correction coefficient α is greater than 1 and is negatively correlated with the high-pressure P. Specifically, when the high-pressure P is greater than 2.8 Mpa, the oil return correction coefficient α is 1.1; when the high-pressure P is greater than 2.2 Mpa and less than or equal to 2.8 Mpa, the oil return correction coefficient α is 1.2; when the high-pressure P is less than or equal to 2.2 Mpa, the oil return correction coefficient α is 1.35. The oil return correction coefficient α can be adjusted according to the actual situation to match the actual working conditions of the air-conditioning system 100.

[0061] The following will illustrate the control method of the air-conditioning system 100 in this embodiment through a specific example:

[0062] When the air-conditioning system 100 is in the single-compressor operation mode, that is, only the first compressor 1 is running, the air-conditioning system 100 executes the single-compressor control step to adjust the operating frequency Fa of the first compressor according to the control instruction. The air-conditioning system 100 detects the operating parameters such as the operating frequency Fa of the first compressor, the operating frequency Fb of the second compressor, the high-pressure P, and the exhaust temperature Tp in real time. When receiving the control instruction for dual-compressor operation, the air-conditioning system 100 detects that the operating frequency Fa of the first compressor is 72 Hz, the high-pressure P is 2.5 MPa, and the exhaust temperature Tp is 70 °C. By looking up the table, the saturation temperature Ts corresponding to the high-pressure P of 2.5 MPa is 43 °C, and the exhaust superheat Dsh = exhaust temperature Tp - saturation temperature Ts = 27 °C. After receiving the control instruction for dual-compressor operation, the air-conditioning system 100 executes the second-compressor start-up step, that is, keeps the operating frequency Fa of the first compressor unchanged at 72 Hz, opens the second pressure relief valve 22, and after 2 minutes, the second compressor 2 starts. The starting operating frequency F0 of the second compressor = 1.2 * 72 / 2.5 - 27 / (3.1415 * 1.2) = 27 Hz. After the second compressor runs at a frequency of 27 Hz for 1 minute, the second pressure relief valve 22 is closed. At this time, the air-conditioning system 100 enters the dual-compressor operation mode, and the air-conditioning system 100 executes the dual-compressor control step to adjust the operating frequency Fa of the first compressor and the operating frequency Fb of the second compressor according to the control instruction. The air-conditioning system 100 detects the operating parameters such as the operating frequency Fa of the first compressor, the operating frequency Fb of the second compressor, the high-pressure P, and the exhaust temperature Tp in real time. When receiving the control instruction for single-compressor operation, the operating frequency Fa of the first compressor is 80 Hz. After receiving the control instruction for single-compressor operation, the air-conditioning system 100 executes the second-compressor shutdown step, that is, keeps the operating frequency Fa of the first compressor unchanged at 80 Hz, shuts down the second compressor 2 (controls the operating frequency Fb of the second compressor to be 0 Hz), opens the second pressure relief valve 22, and after 3 minutes, the second pressure relief valve 22 is closed.

[0063] This embodiment also provides a kind of as Figure 3The air conditioning system 100 shown is a multi-split system. The following will describe the air conditioning system 100 by taking the working condition of the air conditioning system 100 during cooling as an example.

[0064] When the air conditioning system 100 is cooling, the exhaust port of the first compressor 1 discharges high-temperature and high-pressure refrigerant gas, and the first exhaust temperature detection device 11 can be used to detect the exhaust temperature Tp of the first compressor 1. The high-temperature and high-pressure gas refrigerant passes through the first exhaust check valve 13, the oil separator 3 (which separates the lubricating oil in the gas refrigerant, and the separated lubricating oil returns to the first compressor 1 after passing through the oil return capillary 31), the high-pressure pressure detection device 9 and the reversing valve 4 in sequence, and arrives at the outdoor heat exchanger 51. The high-temperature and high-pressure refrigerant gas releases the heat of the refrigerant to the air with the assistance of the fan 52 in the outdoor heat exchanger 51, so that the gaseous refrigerant becomes a liquid refrigerant. An ambient temperature detection device 53 is provided at the outdoor heat exchanger 51, and a heat exchanger outlet temperature detection device 54 is provided at the outlet of the outdoor heat exchanger 51. The high-temperature and high-pressure refrigerant liquid coming out of the outdoor heat exchanger 51 is converted into a low-temperature and low-pressure refrigerant liquid after passing through the throttling device 6, and enters the multiple indoor units 7 after passing through the high-pressure stop valve 17. In the indoor units 7, the air absorbs the coldness in the low-temperature and low-pressure refrigerant liquid, turning the liquid refrigerant into a gaseous refrigerant. The low-temperature and low-pressure refrigerant gas coming out of the indoor unit 7 passes through the low-pressure stop valve 16, the reversing valve 4, the low-pressure pressure detection device 10, and the gas-liquid separation device 8 in sequence, and is sucked into the first compressor 1 from the air intake port of the first compressor 1.

[0065] The air conditioning system 100 also includes a second compressor 2 connected in parallel with the first compressor 1, and the exhaust port of the second compressor 2 has a second exhaust temperature detection device 21 for detecting the exhaust temperature Tp of the second compressor 2. The high-temperature and high-pressure gas refrigerant discharged from the second compressor 2 passes through the second exhaust check valve 23 and merges with the high-temperature and high-pressure gas refrigerant discharged from the first compressor 1, and enters the oil separator 3 together. The low-temperature and low-pressure gas refrigerant coming out of the gas-liquid separation device 8 will flow to the air intake port of the first compressor 1, and part of it will flow to the air intake port of the second compressor 2.

[0066] The air conditioning system 100 is provided with a first pressure relief valve 12 between the first compressor 1 and the gas-liquid separation device 8, which is used to balance the pressure difference between the suction port and the exhaust port of the first compressor 1 when the first compressor 1 is started or stopped. A second pressure relief valve 22 is provided between the second compressor 2 and the gas-liquid separation device 8, which is used to balance the pressure difference between the suction port and the exhaust port of the second compressor 2 when the second compressor 2 is started or stopped.

[0067] The air conditioning system 100 provided in this embodiment can be controlled by using the control method of the air conditioning system provided in this embodiment. It can be understood that in some other embodiments, the specific structure of the air conditioning system 100 can be adjusted according to actual requirements.

[0068] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A control method for an air conditioning system, the air conditioning system comprising a first compressor and a second compressor, characterized in that, The control method includes the following steps: Single-compressor control step: adjusting the operating frequency of the first compressor according to a control instruction; Data acquisition step: detecting the high-pressure pressure, the exhaust temperature, and the operating frequency of the first compressor; Second-compressor start-up step: after receiving a control instruction for dual-compressor operation, while keeping the operating frequency of the first compressor stable, opening a second pressure relief valve communicating with the exhaust port of the second compressor for a first period of time, then starting the second compressor, and making the second compressor operate at a second-compressor start-up operating frequency for a second period of time while the second pressure relief valve is open, and then closing the second pressure relief valve; In the second-compressor start-up step, the second-compressor start-up operating frequency is related to all of the high-pressure pressure, the exhaust temperature, and the operating frequency of the first compressor. Among them, in the data acquisition step, it includes: a step of calculating the superheat degree of the exhaust gas; The second-compressor start-up operating frequency is negatively correlated with the superheat degree of the exhaust gas; In the second-compressor start-up step, the second-compressor start-up operating frequency is calculated by the following formula: Second-compressor start-up operating frequency = oil return correction coefficient * operating frequency of the first compressor / high-pressure pressure - superheat degree of the exhaust gas / (pi * oil return correction coefficient).

2. The control method of the air conditioning system according to claim 1, wherein After the second-compressor start-up step, it further includes: Dual-compressor control step: adjusting the operating frequencies of the first compressor and the second compressor according to a control instruction.

3. The control method of the air-conditioning system according to claim 2, characterized in that, After the dual-compressor control step, it further includes: Second-compressor shutdown step: after receiving a control instruction for single-compressor operation, while keeping the operating frequency of the first compressor stable, shutting down the second compressor, and opening the second pressure relief valve for a third period of time after shutting down the second compressor.

4. The control method of the air conditioning system according to claim 2, wherein In the data acquisition step, it further includes a step of detecting the operating frequency of the second compressor; And after the dual-compressor control step, the control method further includes: First-compressor shutdown step: after receiving a control instruction for single-compressor operation, while keeping the operating frequency of the second compressor stable, shutting down the first compressor, and opening a first pressure relief valve communicating with the exhaust port of the first compressor for a third period of time after shutting down the first compressor.

5. The control method of the air conditioning system according to any one of claims 1-4, characterized in that, In the second-compressor start-up step, keep the operating frequency of the first compressor unchanged, or keep the change range of the operating frequency of the first compressor between plus or minus 2 Hz; In the second-compressor shutdown step, keep the operating frequency of the first compressor unchanged, or keep the change range of the operating frequency of the first compressor between plus or minus 2 Hz; In the first-compressor shutdown step, keep the operating frequency of the second compressor unchanged, or keep the change range of the operating frequency of the second compressor between plus or minus 2 Hz.

6. The control method of the air-conditioning system according to claim 1, characterized in that, The second-compressor start-up operating frequency is negatively correlated with the high-pressure pressure, negatively correlated with the exhaust temperature, and positively correlated with the operating frequency of the first compressor.

7. The control method of the air conditioning system according to claim 3 or 4, characterized in that, The first period of time is greater than the second period of time, and the third period of time is greater than the first period of time.

8. An air-conditioning system, which adopts the air-conditioning system control method as described in any one of claims 1-7, is characterized in that The air conditioning system includes a first compressor, an oil separator, a reversing valve, an outdoor heat exchanger, a throttling device, an indoor heat exchanger and a gas-liquid separation device which are connected in sequence; A first exhaust temperature detection device is provided at the exhaust port of the first compressor, and a first pressure relief valve is provided between the first compressor and the gas-liquid separation device; The air conditioning system further includes: A second compressor, which is connected in parallel with the first compressor. A second exhaust temperature detection device is provided at the exhaust port of the second compressor, and a second pressure relief valve is provided between the second compressor and the gas-liquid separation device; A high-pressure pressure detection device is provided between the oil separator and the reversing valve.

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