Air conditioning system and control method

Abstract

The present invention provides an air conditioning system and control method, the control method comprising the following steps: S1, power on; S2, the air conditioner obtains the current operating mode; S3, the air conditioner determines whether the current operating mode is heating mode; if so, proceeds to step S4; if not, operates normally; S4, after the air conditioner completes the startup operation phase, enters normal control and operates for a first preset duration t1; S5, the air conditioner obtains the current compressor frequency f; S6, determines whether the current compressor frequency f is less than the maximum frequency fmax; if so, operates normally for a second preset duration t2 and then returns to step S5; if not, proceeds to step S7; S7, operates in an increased injection enthalpy mode based on the injection enthalpy superheat and the compressor exhaust temperature. The control method of the air conditioning system of the present invention utilizes the combined control of the injection enthalpy superheat and the compressor exhaust temperature to achieve optimal energy efficiency while ensuring that the air supply meets capacity improvement.

Description

Technical Field

[0001] The present invention relates to the field of air conditioning, and in particular to an air conditioning system and a control method thereof. Background Art

[0002] When operating an air conditioner in low-temperature heating mode, the air conditioner's heating capacity is reduced due to the low ambient temperature. To effectively improve the low-temperature heating effect of the air conditioner, an enthalpy injection compressor is often used to increase the return air enthalpy and increase the return air volume of the system, thereby improving the air conditioner's heating capacity.

[0003] The current air injection enthalpy increase control is based on injection enthalpy superheat control, which only considers improving the capacity of the air conditioning system and ignores the improvement of the air injection enthalpy increase technology on the energy efficiency of the air conditioning system. Therefore, two problems will arise:

[0004] 1. When the ambient temperature is high, the capacity and energy efficiency can be improved without excessive air supply. However, the current control method only considers the capacity. In order to maintain the same injection enthalpy and superheat, the air supply volume is increased, resulting in an increase in the compressor power but no increase in heating capacity, and a decrease in energy efficiency.

[0005] 2. When the ambient temperature is low, a relatively large amount of air supply is required to improve the capacity and energy efficiency. However, in order to maintain the same spray enthalpy superheat, the current control concept does not increase the air supply to the actual required amount, resulting in the heating capacity not being increased to the maximum and the energy efficiency being low.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of the present invention is to propose an air-conditioning system and control method to solve the problem in the prior art that the current air-supply enthalpy increase control during heating operation of the air-conditioning is only the injection enthalpy superheat control, which only considers improving the capacity of the air-conditioning system and ignores the improvement of the energy efficiency of the air-conditioning system by the air-supply enthalpy increase technology.

[0008] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0009] A method for controlling an air conditioning system, comprising the following steps:

[0010] S1, power on;

[0011] S2. The air conditioner obtains the current working mode;

[0012] S3, the air conditioner determines whether the current working mode is heating mode, if so, proceeds to step S4, if not, operates normally;

[0013] S4: After the air conditioner finishes the startup operation phase, it enters normal control and runs for the first preset time t1;

[0014] S5. The air conditioner obtains the current frequency f of the compressor;

[0015] S6, determining whether the current compressor frequency f is less than the maximum frequency fmax, if so, returning to step S5 after normal operation for the second preset time t2, if not, proceeding to step S7;

[0016] S7. Operate the increased injection enthalpy mode in combination with the injection enthalpy superheat and the exhaust temperature of the compressor.

[0017] In the control method of the air conditioning system of the present invention, steps S1 to S7 are interrelated and inseparable. The air conditioning working mode is detected and judged through steps S2 and S3. When the air conditioner is in the heating mode, the air conditioner ends the startup operation phase through step S4 and enters the normal control and runs for the first preset time t1, which is conducive to ensuring that the relevant components gradually reach their normal working state and improve their operating reliability. Then, the current compressor frequency f is detected and judged through steps S5 and S6. If the compressor frequency f is less than the maximum frequency fmax, it means that the current air conditioning system does not need this frequency. So much heating capacity, the system's own heating capacity is in surplus at this time, so there is no need to improve the system's capacity, and it will run normally for the second preset time t2 and then return to step S5; if the compressor frequency f = maximum frequency fmax, it means that it is the maximum frequency at this time, that is, the heating capacity may be insufficient and the capacity needs to be improved, then enter step S7 to operate the increased air injection enthalpy mode in combination with the injection enthalpy superheat and the exhaust temperature of the compressor. First, the air supply volume is ensured to meet the capacity improvement while the energy efficiency is optimized; second, it achieves a good energy-saving and emission reduction effect; third, the low-temperature heating capacity of the air conditioner is increased to improve the user comfort.

[0018] Furthermore, step S7 includes the following steps:

[0019] S71. Open the auxiliary expansion valve and control it according to the superheat of the refrigerant in the plate heat exchanger = 1°C. Finally, the opening degree of the auxiliary expansion valve PMV2 = PMVmax;

[0020] S72. Obtain the current exhaust temperature T1 of the compressor, reduce the opening of the auxiliary expansion valve by a first preset step value A, run for a third preset time t3, obtain the exhaust temperature T2 of the compressor again, and calculate the absolute value of the first exhaust temperature change |ΔT1|=|T1-T2|;

[0021] S73, determining whether the absolute value of the first exhaust temperature change |ΔT1| is less than the first exhaust temperature change threshold K1; if so, returning to step S72; if not, proceeding to step S74;

[0022] S74 , obtaining that the opening of the auxiliary expansion valve at this time is a critical opening PMVa, and controlling the auxiliary expansion valve to operate at the critical opening PMVa for a fourth preset time period t4, and then returning to step S5 .

[0023] Steps S71 to S74 are interrelated and inseparable. In step S71, the auxiliary expansion valve is opened and controlled according to the superheat of the refrigerant in the plate heat exchanger = 1°C. The superheat of the jet is controlled to be around 1. This control is mature. The superheat is 1°C, which is the minimum superheat to ensure that the refrigerant returning to the compressor is in a gaseous state, to prevent liquid hammer and damage to the compressor. The auxiliary expansion valve opening PMV2 = PMVmax is recorded, and the final opening is recorded as the maximum opening PMVmax allowed by the auxiliary expansion valve. If the auxiliary expansion valve opening is opened further, the superheat of the jet will be reduced, and there is a risk of liquid return, and step S72 is entered; in step S72, after obtaining the current compressor exhaust temperature T1, the auxiliary expansion valve opening is closed by the first preset step value A steps, and after running for the third preset time t3, the compressor exhaust temperature T2 is obtained again to facilitate the calculation of the absolute value of the first exhaust temperature change |△T1|, and step S73 is used to determine whether the absolute value of the first exhaust temperature change |△T1| < the first exhaust temperature change The exhaust temperature change threshold K1, if the absolute value of the first exhaust temperature change |△T1| is less than the first exhaust temperature change threshold K1, it means that the exhaust temperature has not changed significantly, the exhaust temperature is not a critical value, and the opening of the auxiliary expansion valve is not a critical opening PMVa, then the process returns to step S72, so as to continue the cycle to find the critical value of the exhaust temperature and the critical opening of the auxiliary expansion valve; if the absolute value of the first exhaust temperature change |△T1| is greater than or equal to the first exhaust temperature change threshold K1, it means that the temperature has changed significantly at this time, the exhaust temperature is a critical value, and it can be determined that the energy efficiency is optimal at this time, then the process enters step S74, obtains the opening of the auxiliary expansion valve at this time as the critical opening PMVa, and controls the auxiliary expansion valve to operate at the critical opening PMVa for the fourth preset time t4, then returns to step S5; first, the air supply volume is ensured to meet the capacity improvement while the energy efficiency is optimized; second, a good energy-saving and emission reduction effect is achieved; third, the low-temperature heating capacity of the air conditioner is increased to improve the use comfort.

[0024] Whether the current air-conditioning system needs such a large amount of heating is determined by whether the compressor frequency is the maximum frequency, and then whether to operate the increased air injection enthalpy mode in combination with the injection enthalpy superheat and the exhaust temperature of compressor 1 is determined, making the control method of the air-conditioning system more precise and accurate; and improving the reliability of the air-conditioning operation.

[0025] Furthermore, step S74 includes the following steps:

[0026] S741, determine the exhaust temperature change again. If the absolute value of the second exhaust temperature change |ΔT2| is greater than or equal to the second exhaust temperature change threshold K2, proceed to step S742;

[0027] S742: Acquire the opening of the auxiliary expansion valve at this time as the critical opening PMVa, control the auxiliary expansion valve to operate at the critical opening PMVa for a fourth preset time period t4, and then return to step S5.

[0028] Steps S741 to S742 are interrelated and inseparable. In step S741, the exhaust temperature change is judged again to avoid misjudgment and improve the precision and accuracy of air-conditioning control. If the absolute value of the second exhaust temperature change |△T2| ≥ the second exhaust temperature change threshold K2, it means that the temperature has changed significantly at this time, and the exhaust temperature is a critical value. It can be determined that the energy efficiency is optimal at this time, and step S742 is entered to obtain the opening of the auxiliary expansion valve at this time as the critical opening PMVa, and control the auxiliary expansion valve to run at the critical opening PMVa for the fourth preset time t4, and then return to step S5. First, the air supply volume is ensured to meet the capacity improvement while the energy efficiency is optimized; second, a good energy-saving and emission reduction effect is achieved; third, the low-temperature heating capacity of the air conditioner is increased to improve the comfort of use.

[0029] Furthermore, step S741 includes the following steps:

[0030] S7411: Close the auxiliary expansion valve opening by a second preset step value B, and after running for a fifth preset time t5, obtain the current compressor exhaust temperature T3, calculate the absolute value of the second exhaust temperature change |ΔT2|=|T1-T3|, and proceed to step S7412;

[0031] S7412. Determine whether the absolute value of the second exhaust temperature change |ΔT2| is less than the second exhaust temperature change threshold K2; if so, return to step S7411; if not, proceed to step S742.

[0032] Steps S7411 to S7412 are interrelated and inseparable. In step S7411, the exhaust temperature change is judged again to avoid misjudgment and improve the precision and accuracy of air-conditioning control. The auxiliary expansion valve opening is closed by the second preset step value B step. After running for the fifth preset time t5, the current compressor exhaust temperature T3 is obtained to facilitate the calculation of the second exhaust temperature change absolute value |△T2|=|T1-T3|. Step S7412 is used to determine whether the first exhaust temperature change absolute value |△T2|<the second exhaust temperature change threshold value K2. If the second exhaust temperature change absolute value |△T2|<the second exhaust temperature change threshold value K2, it means that the exhaust temperature has not changed significantly and the exhaust temperature is not a critical value. The auxiliary expansion valve is closed. If the opening is not the critical opening PMVa, then return to step S7411 to continue the cycle to find the critical value of the exhaust temperature and the critical opening of the auxiliary expansion valve; if the absolute value of the second exhaust temperature change |△T2| ≥ the second exhaust temperature change threshold K2, it means that the temperature has changed significantly at this time, and the exhaust temperature is the critical value. It can be determined that the energy efficiency is optimal at this time, and enter step S742 to obtain the opening of the auxiliary expansion valve at this time as the critical opening PMVa, and control the auxiliary expansion valve to run at the critical opening PMVa for the fourth preset time t4, and then return to step S5. First, the air supply volume is met to improve the capacity while the energy efficiency is optimized; second, it achieves a good energy-saving and emission reduction effect; third, the low-temperature heating capacity of the air conditioner is increased to improve the comfort of use.

[0033] Furthermore, in step S71 , the auxiliary expansion valve is opened, and the initial opening degree of the auxiliary expansion valve is PMV1 = 2fmax.

[0034] In step S71, the auxiliary expansion valve 7 is opened, and the initial opening PMV1=2fmax. The opening of the auxiliary expansion valve 7 is adjusted little by little from the closed state to the target opening. The process is too slow. First, a more reasonable empirical value PMV1=2fmax is given, and then the adjustment is started from the empirical value, so that the time for the auxiliary expansion valve 7 to be adjusted to the target opening is greatly shortened, and the adjustment process is faster.

[0035] Furthermore, the value range of the first preset step value A is [4, 8].

[0036] The value range of the first preset step value A is within the above range, which improves the precision and accuracy of air conditioning control.

[0037] Furthermore, the value range of the second preset step value B is [2, 6].

[0038] The value range of the second preset step value B is within the above range, which improves the precision and accuracy of air conditioning control.

[0039] Furthermore, the value range of the first exhaust temperature change threshold K1 is [0.2, 0.5].

[0040] The value range of the first exhaust temperature change threshold K1 is within the above range, which improves the precision and accuracy of air-conditioning control.

[0041] Furthermore, the value range of the second exhaust temperature change threshold K2 is [0.4, 0.8].

[0042] The value range of the second exhaust gas temperature change threshold K2 is within the above range, which improves the precision and accuracy of air-conditioning control.

[0043] In a second aspect of the present invention, an air-conditioning system is proposed, which includes a compressor, a four-way valve, an outdoor heat exchanger, an indoor heat exchanger, a plate heat exchanger and a throttling device connected into a circulation loop through pipelines, and the throttling device includes a main expansion valve and an auxiliary expansion valve, and the auxiliary expansion valve is arranged between the outlet of the plate heat exchanger and the air supply port of the compressor; the air-conditioning system uses any one of the control methods of an air-conditioning system described.

[0044] Compared with the prior art, the air conditioning system and control method described in the present invention have the following advantages:

[0045] Beneficial effects:

[0046] The present invention provides an air conditioning system and control method, wherein steps S1 to S7 are interrelated and inseparable. Steps S2 and S3 are used to detect and judge the air conditioning working mode. When the air conditioner is in the heating mode, step S4 is used to end the startup operation phase of the air conditioner and enter normal control. The system runs for a first preset time t1, which is beneficial to ensure that the relevant components gradually reach their normal working state and improve their operating reliability. Then, steps S5 and S6 are used to detect and judge the current compressor frequency f. If the compressor frequency f is less than the maximum frequency fmax, it means that the current air conditioning system does not need so many The heating capacity of the system itself is in surplus at this time, so there is no need to improve the capacity of the system. The system will operate normally for the second preset time t2 and then return to step S5. If the frequency f of the compressor is greater than or equal to the maximum frequency fmax, it means that the frequency is the maximum at this time, that is, the heating capacity may be insufficient and the capacity needs to be improved. Then, step S7 is entered to control the operation of the increased air injection enthalpy mode in combination with the injection enthalpy superheat and the exhaust temperature of the compressor. First, the air supply volume is ensured to meet the capacity improvement while the energy efficiency is optimized. Second, it achieves a good energy-saving and emission reduction effect. Third, the low-temperature heating capacity of the air conditioner is increased to improve the user comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic flow chart of a method for controlling an air-conditioning system according to an embodiment of the present invention;

[0048] Figure 2 The figure is a schematic diagram of the principle of an air-conditioning system according to an embodiment of the present invention.

[0049] Description of reference numerals:

[0050] 1. Compressor; 2. Four-way valve; 3. External heat exchanger; 4. Internal heat exchanger; 5. Plate heat exchanger; 6. Main expansion valve; 7. Auxiliary expansion valve. DETAILED DESCRIPTION

[0051] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The descriptions of "first", "second", etc. mentioned in the embodiments of the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0052] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0053] In the prior art, the current air supply enthalpy increase control during heating operation of the air conditioner is only the spray enthalpy superheat control, which only considers improving the capacity of the air conditioning system and ignores the improvement of the energy efficiency of the air conditioning system by the air supply enthalpy increase technology; when the ambient temperature is high, in order to maintain the same spray enthalpy superheat, the air supply volume is increased, resulting in an increase in the power of the compressor 1 but no increase in the heating capacity, and a decrease in energy efficiency; when the ambient temperature is low, in order to maintain the same spray enthalpy superheat, the increased air supply volume does not reach the actual required air supply volume, resulting in the heating capacity not being increased to the maximum and the problem of low energy efficiency.

[0054] Example 1

[0055] like Figure 2As shown, the air conditioning system includes a compressor 1, a four-way valve 2, an outdoor heat exchanger 3, an indoor heat exchanger 4, a plate heat exchanger 5, and a throttling device, all connected by piping to form a circulation loop. The throttling device includes a main expansion valve 6 and an auxiliary expansion valve 7. The main expansion valve 6 is located between the outlet of the plate heat exchanger 5 and the inlet of the outdoor heat exchanger 3; the auxiliary expansion valve 7 is located between the outlet of the plate heat exchanger 5 and the air supply port of the compressor 1. When the air conditioning system is activated in heating mode, air supply is activated to increase enthalpy. Some low-temperature refrigerant from the indoor heat exchanger 4 is directly injected into the compression chamber of the compressor 1 through the plate heat exchanger 5 and the auxiliary expansion valve 7. This lowers the exhaust temperature of the compressor 1, thereby reducing the oil sump and cylinder temperatures of the compressor 1, effectively reducing the heat exchange losses of the compressor 1, thereby improving the efficiency of the compressor 1 and enhancing the energy efficiency ratio.

[0056] To address the above issues, the applicant used a certain model of 3P ducted central air conditioner as an example. The system layout was based on the flow direction of the heating refrigerant, using R410A as the system refrigerant. The heating mode was activated at -5°C. The effects of varying auxiliary expansion valve openings on the unit's low-temperature heating capacity, energy efficiency, and exhaust temperature were determined, as shown in Table 1.

[0057] Table 1

[0058]

[0059] Table 1 shows that increasing the opening of auxiliary expansion valve 7 can increase capacity, but energy efficiency doesn't continue to improve, and exhaust temperature doesn't continue to decrease. As the opening of auxiliary expansion valve 7 increases, the power increase increases, the capacity increase decreases, and the temperature decreases. There is a limit to temperature decrease, and an inflection point in energy efficiency. The temperature drop limit and the expansion valve opening at the energy efficiency inflection point are equivalent. This shows that the exhaust temperature of compressor 1 cannot decrease indefinitely. When the exhaust temperature of compressor 1 drops to the critical value, energy efficiency is maximized, and capacity is also increased to a higher level.

[0060] On the contrary, if the opening of the auxiliary expansion valve 7 reaches the maximum, as the opening of the auxiliary expansion valve 7 decreases, the power reduction becomes smaller and smaller, the capacity reduction becomes larger and larger, the exhaust temperature rise has a limit, the exhaust temperature rise becomes larger and larger, the energy efficiency has an inflection point, and the limit of the exhaust temperature rise and the expansion valve opening at the energy efficiency inflection point are equivalent.

[0061] The applicant also conducted experiments on other air conditioner models and obtained the same conclusions as above, which will not be elaborated here.

[0062] This embodiment provides a control method for an air-conditioning system, which controls the opening of the auxiliary expansion valve 7 to achieve optimal energy efficiency of the air conditioner, thereby achieving energy conservation and emission reduction.

[0063] The exhaust temperature of the compressor 1 is adjusted by controlling the opening of the auxiliary expansion valve 7. As the opening of the auxiliary expansion valve 7 decreases, the amplitude of the exhaust temperature change becomes larger and larger. When it is detected that the amplitude of the exhaust temperature change of the compressor 1 becomes larger and larger as the valve opening decreases, it can be determined that the exhaust temperature at this time is a critical value, and it can be determined that the energy efficiency at this time is optimal.

[0064] The control method of the air-conditioning system described in this embodiment uses the combined control of the injection enthalpy superheat and the exhaust temperature of compressor 1 to ensure that the air supply volume meets the optimal requirements for capacity improvement and energy efficiency improvement; when the ambient temperature is high, the air supply volume is reduced without affecting the capacity improvement and improving energy efficiency; when the ambient temperature is low, the air supply volume is increased to reach the return air volume required for maximum capacity, thereby improving capacity and energy efficiency.

[0065] This embodiment provides a control method for an air conditioning system. Figure 1 As shown, the control method of the air conditioning system includes the following steps:

[0066] S1, power on;

[0067] S2. The air conditioner obtains the current working mode;

[0068] S3, the air conditioner determines whether the current working mode is heating mode, if so, proceeds to step S4, if not, operates normally;

[0069] S4: After the air conditioner finishes the startup operation phase, it enters normal control and runs for the first preset time t1;

[0070] S5. The air conditioner obtains the current frequency f of the compressor 1;

[0071] S6, determining whether the current frequency f of the compressor 1 is less than the maximum frequency fmax, if so, returning to step S5 after normal operation for the second preset time t2, if not, proceeding to step S7;

[0072] S7. Operate the increased injection enthalpy mode in combination with the injection enthalpy superheat and the exhaust gas temperature of the compressor 1.

[0073] The control method of the air-conditioning system described in this embodiment is interrelated and inseparable from steps S1 to S7. The air-conditioning working mode is detected and judged through steps S2 and S3. When the air-conditioner is in the heating mode, the air-conditioner enters the normal control after the startup operation phase ends through step S4, and runs for the first preset time t1, which is conducive to ensuring that the relevant components gradually reach their normal working state and improve their operating reliability. Then, the frequency f of the current compressor 1 is detected and judged through steps S5 and S6. If the frequency f of the compressor 1 is less than the maximum frequency fmax, it means that the current air-conditioning system does not need With such a large amount of heating capacity, the system's own heating capacity is in surplus, so there is no need to improve the system's capacity. It will run normally for the second preset time t2 and then return to step S5; if the frequency f of compressor 1 = maximum frequency fmax, it means that the frequency is maximum at this time, that is, the heating capacity may be insufficient and the capacity needs to be improved, then enter step S7 to operate the increased air injection enthalpy mode in combination with the injection enthalpy superheat and the exhaust temperature of compressor 1. First, the air supply volume is ensured to meet the capacity improvement while the energy efficiency is optimized; second, it achieves a good energy-saving and emission reduction effect; third, the low-temperature heating capacity of the air conditioner is increased to improve the user comfort.

[0074] Specifically, step S7 includes the following steps:

[0075] S71, open the auxiliary expansion valve 7 and control it according to the superheat of the refrigerant in the plate heat exchanger 5 = 1°C, and finally the opening degree of the auxiliary expansion valve 7 PMV2 = PMVmax;

[0076] S72, obtaining the current exhaust temperature T1 of compressor 1, reducing the opening of auxiliary expansion valve 7 by a first preset step value A, and operating for a third preset time t3, obtaining the exhaust temperature T2 of compressor 1 again, and calculating the absolute value of the first exhaust temperature change |ΔT1|=|T1-T2|;

[0077] S73, determining whether the absolute value of the first exhaust temperature change |ΔT1| is less than the first exhaust temperature change threshold K1; if so, returning to step S72; if not, proceeding to step S74;

[0078] S74 , obtaining that the opening of the auxiliary expansion valve 7 at this moment is the critical opening PMVa, and controlling the auxiliary expansion valve 7 to operate at the critical opening PMVa for a fourth preset time period t4, and then returning to step S5 .

[0079] Steps S71 to S74 are interrelated and inseparable. In step S71, the auxiliary expansion valve 7 is opened and controlled according to the superheat of the refrigerant in the plate heat exchanger = 1°C. The superheat of the jet is controlled to be around 1. This control is mature. The superheat is 1°C, which is the minimum superheat to ensure that the refrigerant returning to the compressor is in a gaseous state, to prevent liquid hammer and damage to the compressor. The opening of the auxiliary expansion valve 7 PMV2 = PMVmax is recorded, and the final opening is recorded as the maximum opening PMVmax allowed by the auxiliary expansion valve 7. If the opening of the auxiliary expansion valve 7 is opened further, the superheat of the jet will be reduced, and there is a risk of liquid backflow, and step S72 is entered; in step S72, after obtaining the current compressor exhaust temperature T1, the opening of the auxiliary expansion valve 7 is closed by the first preset step value A steps, and after running for the third preset time t3, the compressor exhaust temperature T2 is obtained again to facilitate the calculation of the absolute value of the first exhaust temperature change |△T1|, and step S73 is used to determine whether the absolute value of the first exhaust temperature change |△T1| < the first Exhaust temperature change threshold K1. If the absolute value of the first exhaust temperature change |△T1| is less than the first exhaust temperature change threshold K1, it means that the exhaust temperature has not changed significantly, the exhaust temperature is not the critical value, and the opening of the auxiliary expansion valve 7 is not the critical opening PMVa, then return to step S72, so as to continue the cycle to find the critical value of the exhaust temperature and the critical opening of the auxiliary expansion valve 7; if the absolute value of the first exhaust temperature change |△T1| is greater than or equal to the first exhaust temperature change threshold K1, it means that the temperature has changed significantly at this time, the exhaust temperature is the critical value, and it can be determined that the energy efficiency is optimal at this time, then enter step S74, obtain the opening of the auxiliary expansion valve 7 at this time as the critical opening PMVa, and control the auxiliary expansion valve 7 to operate at the critical opening PMVa for the fourth preset time t4, and then return to step S5; first, the air supply volume is ensured to meet the capacity improvement while the energy efficiency is optimized; second, a good energy-saving and emission reduction effect is achieved; third, the low-temperature heating capacity of the air conditioner is increased to improve the comfort of use.

[0080] Specifically, step S74 includes the following steps:

[0081] S741, determine the exhaust temperature change again. If the absolute value of the second exhaust temperature change |ΔT2| is greater than or equal to the second exhaust temperature change threshold K2, proceed to step S742;

[0082] S742: Obtain the critical opening degree PMVa of the auxiliary expansion valve 7 at this time, control the auxiliary expansion valve 7 to operate at the critical opening degree PMVa for a fourth preset time period t4, and then return to step S5.

[0083] Steps S741 to S742 are interrelated and inseparable. In step S741, the exhaust temperature change is judged again to avoid misjudgment and improve the precision and accuracy of air-conditioning control. If the absolute value of the second exhaust temperature change |△T2| ≥ the second exhaust temperature change threshold K2, it means that the temperature has changed significantly at this time, and the exhaust temperature is a critical value. It can be determined that the energy efficiency is optimal at this time, and step S742 is entered to obtain the opening of the auxiliary expansion valve 7 at this time as the critical opening PMVa, and control the auxiliary expansion valve 7 to run at the critical opening PMVa for the fourth preset time t4, and then return to step S5. First, the air supply volume is ensured to meet the capacity improvement while the energy efficiency is optimized; second, a good energy-saving and emission reduction effect is achieved; third, the low-temperature heating capacity of the air conditioner is increased to improve the comfort of use.

[0084] Specifically, step S741 includes the following steps:

[0085] S7411: The auxiliary expansion valve 7 is closed by a second preset step value B, and after the fifth preset time t5, the current exhaust gas temperature T3 of the compressor 1 is obtained, and the absolute value of the second exhaust gas temperature change |ΔT2|=|T1-T3| is calculated, and the process proceeds to step S7412;

[0086] S7412. Determine whether the absolute value of the second exhaust temperature change |ΔT2| is less than the second exhaust temperature change threshold K2; if so, return to step S7411; if not, proceed to step S742.

[0087] Steps S7411 to S7412 are interrelated and inseparable. In step S7411, the exhaust temperature change is judged again to avoid misjudgment and improve the precision and accuracy of air-conditioning control. The opening of the auxiliary expansion valve 7 is closed by the second preset step value B step. After running for the fifth preset time t5, the exhaust temperature T3 of the current compressor 1 is obtained to facilitate the calculation of the absolute value of the second exhaust temperature change |△T2|=|T1-T3|. Step S7412 is used to judge whether the absolute value of the first exhaust temperature change |△T2| is less than the second exhaust temperature change threshold K2. If the absolute value of the second exhaust temperature change |△T2| is less than the second exhaust temperature change threshold K2, it means that the exhaust temperature has not changed significantly and the exhaust temperature is not a critical value. The auxiliary expansion valve 7 is closed. If the opening is not the critical opening PMVa, then return to step S7411, so as to continue the cycle to find the critical value of the exhaust temperature and the critical opening of the auxiliary expansion valve 7; if the absolute value of the second exhaust temperature change |△T2| ≥ the second exhaust temperature change threshold K2, it means that the temperature has changed significantly at this time, and the exhaust temperature is the critical value. It can be determined that the energy efficiency is optimal at this time, and enter step S742, obtain the opening of the auxiliary expansion valve 7 at this time as the critical opening PMVa, and control the auxiliary expansion valve 7 to run at the critical opening PMVa for the fourth preset time t4, and then return to step S5. First, the air supply volume is met to improve the capacity while the energy efficiency is optimized; second, it achieves a good energy-saving and emission reduction effect; third, the low-temperature heating capacity of the air conditioner is increased to improve the comfort of use.

[0088] Specifically, in step S71 , the auxiliary expansion valve 7 is opened, and the initial opening degree PMV1 of the auxiliary expansion valve 7 is 2fmax.

[0089] In step S71, the auxiliary expansion valve 7 is opened, and the initial opening PMV1 = 2fmax. The opening of the auxiliary expansion valve 7 is adjusted little by little from the closed state to the target opening. The process is too slow. First, a more reasonable empirical value PMV1 = 2fmax is given, and then the adjustment is started from the empirical value, so that the time for the auxiliary expansion valve 7 to adjust to the target opening is greatly shortened, and the adjustment process is faster; PMV1 = 2fmax here only emphasizes the numerical relationship, for example, when fmax = 100HZ, PMV1 = 200PLS.

[0090] Specifically, the second preset step value B is less than the first preset step value A.

[0091] Specifically, the value range of the first preset step value A is not specifically limited.

[0092] More specifically, the value range of the first preset step value A is [4, 8], the first preset step value A can take any value in [4, 8], and the unit of the first preset step value A is pls.

[0093] The value range of the first preset step value A is within the above range, which improves the precision and accuracy of air conditioning control.

[0094] Preferably, in this embodiment, the value of the first preset step value A is 5.

[0095] Specifically, the value range of the second preset step value B is not specifically limited.

[0096] More specifically, the value range of the second preset step value B is [2, 6], the second preset step value B can be any value in [2, 6], and the unit of the second preset step value B is pls.

[0097] The value range of the second preset step value B is within the above range, which improves the precision and accuracy of air conditioning control.

[0098] Preferably, in this embodiment, the second preset step value B is 3.

[0099] Specifically, the value range of the first exhaust temperature change threshold K1 is not specifically limited.

[0100] More specifically, the value range of the first exhaust temperature change threshold K1 is [0.2, 0.5], and the first exhaust temperature change threshold K1 can take any value in [0.2, 0.5].

[0101] The value range of the first exhaust temperature change threshold K1 is within the above range, which improves the precision and accuracy of air-conditioning control.

[0102] Preferably, in this embodiment, the value of the first exhaust temperature change threshold K1 is 0.3.

[0103] Specifically, the value range of the second exhaust temperature change threshold K2 is not specifically limited.

[0104] More specifically, the value range of the second exhaust temperature change threshold K2 is [0.4, 0.8], and the second exhaust temperature change threshold K2 can take any value in [0.4, 0.8].

[0105] The value range of the second exhaust gas temperature change threshold K2 is within the above range, which improves the precision and accuracy of air-conditioning control.

[0106] Preferably, in this embodiment, the value of the second exhaust temperature change threshold K2 is 0.6.

[0107] Specifically, the value range of the first preset time length t1 is not specifically limited.

[0108] More specifically, the value range of the first preset time length t1 is [0, 10], the first preset time length t1 can take any value in [0, 10], and the unit of the first preset time length t1 is min.

[0109] Preferably, in this embodiment, the value of the first preset time length t1 is 5.

[0110] Specifically, the value range of the second preset time length t2 is not specifically limited.

[0111] More specifically, the value range of the second preset time length t2 is [20, 50], the first preset time length t2 can take any value in [20, 50], and the unit of the second preset time length t2 is min.

[0112] Preferably, in this embodiment, the value of the second preset time length t2 is 30.

[0113] Specifically, the value range of the third preset time length t3 is not specifically limited.

[0114] More specifically, the value range of the third preset time length t3 is [2, 6], the third preset time length t3 can take any value in [2, 6], and the unit of the third preset time length t3 is s.

[0115] Preferably, in this embodiment, the value of the third preset time length t3 is 3.

[0116] Specifically, the value range of the fourth preset time length t4 is not specifically limited.

[0117] More specifically, the value range of the fourth preset time length t4 is [0.5, 1.5], the fourth preset time length t4 can take any value in [0.5, 1.5], and the unit of the fourth preset time length t4 is h.

[0118] Preferably, in this embodiment, the value of the fourth preset time length t4 is 1.

[0119] Specifically, the value range of the fifth preset time length t5 is not specifically limited.

[0120] More specifically, the value range of the fifth preset time length t5 is [2, 6], the fifth preset time length t5 can take any value in [2, 6], and the unit of the fifth preset time length t5 is s.

[0121] Preferably, in this embodiment, the value of the fifth preset time length t5 is 3.

[0122] The present invention provides an air conditioning system and control method, wherein steps S1 to S7 are interrelated and inseparable. Steps S2 and S3 are used to detect and judge the air conditioning working mode. When the air conditioner is in the heating mode, step S4 is used to end the startup operation phase of the air conditioner and enter normal control. The system runs for a first preset time t1, which is beneficial to ensure that the relevant components gradually reach their normal working state and improve their operating reliability. Then, steps S5 and S6 are used to detect and judge the current compressor frequency f. If the compressor frequency f is less than the maximum frequency fmax, it means that the current air conditioning system does not need so many The heating capacity of the system itself is in surplus at this time, so there is no need to improve the capacity of the system. The system will operate normally for the second preset time t2 and then return to step S5. If the frequency f of the compressor is greater than or equal to the maximum frequency fmax, it means that the frequency is the maximum at this time, that is, the heating capacity may be insufficient and the capacity needs to be improved. Then, step S7 is entered to control the operation of the increased air injection enthalpy mode in combination with the injection enthalpy superheat and the exhaust temperature of the compressor. First, the air supply volume is ensured to meet the capacity improvement while the energy efficiency is optimized. Second, it achieves a good energy-saving and emission reduction effect. Third, the low-temperature heating capacity of the air conditioner is increased to improve the user comfort.

[0123] Example 2

[0124] This embodiment provides an air-conditioning system, which uses the control method of an air-conditioning system as described in any one of Embodiment 1.

[0125] like Figure 2 As shown, the air-conditioning system includes a compressor 1, a four-way valve 2, an outdoor heat exchanger 3, an indoor heat exchanger 4, a plate heat exchanger 5 and a throttling device connected to form a circulation loop through pipelines. The throttling device includes a main expansion valve 6 and an auxiliary expansion valve 7; the main expansion valve 6 is arranged between the outlet of the plate heat exchanger 5 and the inlet of the outdoor heat exchanger 3; the auxiliary expansion valve 7 is arranged between the outlet of the plate heat exchanger 5 and the air supply port of the compressor 1.

[0126] For the air-conditioning system, in addition to the compressor 1, four-way valve 2, outdoor heat exchanger 3, indoor heat exchanger 4, plate heat exchanger 5 and throttling device, it also includes other related components. Since the specific structure and specific assembly relationship of the related components are all existing technologies, they are not described here.

[0127] The advantages of the air-conditioning system and the control method of the air-conditioning system described above over the prior art are the same and will not be described in detail here.

[0128] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A method for controlling an air conditioning system, characterized in that: The control method of the air conditioning system comprises the following steps: S1, power on; S2, the air conditioner obtains the current working mode; S3, the air conditioner determines whether the current working mode is heating mode, if so, proceeds to step S4, if not, operates normally; S4: After the air conditioner finishes the startup operation phase, it enters normal control and runs for the first preset time t1; S5, the air conditioner obtains the current frequency f of the compressor (1); S6, determining whether the current frequency f of the compressor (1) is less than the maximum frequency fmax, if so, returning to step S5 after normal operation for the second preset time t2, if not, proceeding to step S7; S7, operating the increased injection enthalpy mode in combination with the injection enthalpy superheat and the exhaust temperature of the compressor (1); Step S7 includes the following steps: S71, open the auxiliary expansion valve (7), and control it according to the superheat of the refrigerant in the plate heat exchanger (5) = 1°C, and finally the opening degree of the auxiliary expansion valve (7) PMV2 = PMVmax; S72, obtaining the current exhaust temperature T1 of the compressor (1), closing the auxiliary expansion valve (7) by a first preset step value A, and after running for a third preset time t3, obtaining the exhaust temperature T2 of the compressor (1) again, and calculating the absolute value of the first exhaust temperature change |ΔT1|=|T1-T2|; S73, determining whether the absolute value of the first exhaust temperature change |ΔT1| is less than the first exhaust temperature change threshold K1; if so, returning to step S72; if not, proceeding to step S74; S74, obtaining the opening of the auxiliary expansion valve (7) at this time as the critical opening PMVa, and controlling the auxiliary expansion valve (7) to operate at the critical opening PMVa for a fourth preset time length t4, and then returning to step S5.

2. The control method of an air conditioning system according to claim 1, characterized in that: Step S74 includes the following steps: S741, determine the exhaust temperature change again. If the absolute value of the second exhaust temperature change |ΔT2| is greater than or equal to the second exhaust temperature change threshold K2, proceed to step S742; S742: Obtain the opening of the auxiliary expansion valve (7) at this time as the critical opening PMVa, control the auxiliary expansion valve (7) to operate at the critical opening PMVa for a fourth preset time length t4, and then return to step S5.

3. The control method of an air conditioning system according to claim 2, characterized in that: Step S741 includes the following steps: S7411, the auxiliary expansion valve (7) is opened and closed by a second preset step value B, and after running for a fifth preset time t5, the current exhaust temperature T3 of the compressor (1) is obtained, and the absolute value of the second exhaust temperature change |ΔT2|=|T1-T3| is calculated, and the process proceeds to step S7412; S7412. Determine whether the absolute value of the second exhaust gas temperature change |ΔT2| is less than the second exhaust gas temperature change threshold K2; if so, return to step S7411; if not, proceed to step S742.

4. The control method of an air conditioning system according to claim 1, characterized in that: In step S71, the auxiliary expansion valve (7) is opened, and the initial opening degree PMV1 of the auxiliary expansion valve (7) is 2fmax.

5. The control method of an air conditioning system according to claim 1, characterized in that: The value range of the first preset step value A is [4, 8].

6. The control method of an air conditioning system according to claim 3, characterized in that: The value range of the second preset step value B is [2, 6].

7. The control method of an air conditioning system according to claim 1, characterized in that: The value range of the first exhaust temperature change threshold K1 is [0.2, 0.5].

8. The control method of an air conditioning system according to claim 2, characterized in that: The value range of the second exhaust temperature change threshold K2 is [0.4, 0.8].

9. An air conditioning system, characterized in that: The air-conditioning system comprises a compressor (1), a four-way valve (2), an outdoor heat exchanger (3), an indoor heat exchanger (4), a plate heat exchanger (5) and a throttling device connected to form a circulation loop through pipelines, wherein the throttling device comprises a main expansion valve (6) and an auxiliary expansion valve (7), and the auxiliary expansion valve (7) is arranged between the outlet of the plate heat exchanger (5) and the air supply port of the compressor (1); the air-conditioning system uses a control method for an air-conditioning system according to any one of claims 1 to 8.

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