A control method of a heat pump air conditioning system

Abstract

This invention provides a control method for a heat pump air conditioning system, comprising: a detection step, detecting the suction superheat of the compressor; a judgment step, judging whether the suction superheat is less than a first preset value 'a' and whether it is greater than a second preset value 'b'; and a control step, when the heat pump system is operating in cooling or heating mode: when the suction superheat is less than 'a', controlling to reduce the opening of the second or first electronic expansion valve; when the opening of the second or first electronic expansion valve is less than the lower limit 'c', controlling to reduce the opening of the first or second electronic expansion valve; when the suction superheat is greater than 'b', controlling to increase the opening of the second or first electronic expansion valve; and when the opening of the second or first electronic expansion valve is greater than the upper limit 'd', controlling to increase the opening of the first or second electronic expansion valve. According to this invention, the most suitable refrigerant flow rate can be selected to meet the system's operation, ensuring the system operates at its optimal performance, increasing cooling or heating capacity, and improving energy efficiency.

Description

Technical Field

[0001] This invention relates to the field of heat pump air conditioning technology, and more specifically to a control method for a heat pump air conditioning system. Background Technology

[0002] Currently, higher requirements are being placed on the energy efficiency of heat pump air conditioning systems. In particular, air source heat pump air conditioners face problems such as high exhaust temperature and insufficient heating capacity at low temperatures during their promotion in northern regions.

[0003] To address this deficiency, systems are becoming increasingly complex, and the use of multiple electronic expansion valves for control is becoming more common. However, current electronic expansion valve control strategies for heat pump air conditioning systems typically rely solely on feedback adjustment based on compressor suction or exhaust superheat. This approach is primarily suited for conventional single-stage systems with a single electronic expansion valve.

[0004] Because existing heat pump air conditioning systems using gas replenishment and enthalpy enhancement structures suffer from structural defects and the inability to precisely control multiple electronic expansion valves, resulting in technical problems such as the need to improve system energy efficiency, this invention studies and designs a control method for heat pump air conditioning systems. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of the existing heat pump air conditioning system with gas replenishment and enthalpy increase structure, which has structural defects and multiple electronic expansion valves cannot be precisely controlled, resulting in the need to improve the system energy efficiency. Thus, a control method for a heat pump air conditioning system is provided.

[0006] To address the above problems, the present invention provides a control method for a heat pump air conditioning system, comprising:

[0007] The heat pump air conditioning system includes a compressor, a first heat exchanger, a first electronic expansion valve, a flash evaporator, a second electronic expansion valve, and an indoor heat exchanger. The flash evaporator is connected between the first electronic expansion valve and the second electronic expansion valve. The gas outlet end of the flash evaporator is connected to the gas supply end of the compressor. One end of the first heat exchanger is connected to the first electronic expansion valve, and the other end is connected to the exhaust end or intake end of the compressor. The indoor heat exchanger is connected between the second electronic expansion valve and the exhaust end or intake end of the compressor.

[0008] The control method includes:

[0009] The detection step involves detecting the suction superheat of the compressor.

[0010] The control steps involve adjusting the opening of the first electronic expansion valve and the opening of the second electronic expansion valve based on the intake superheat.

[0011] The judgment step is to determine whether the inhalation superheat is less than the first preset value a and whether it is greater than the second preset value b, where b>a>0;

[0012] The control steps, when the heat pump system is operating in cooling mode: when the suction superheat is less than a, the opening degree B2 of the second electronic expansion valve is reduced; and when the opening degree B2 of the second electronic expansion valve is less than the lower limit c, the opening degree B1 of the first electronic expansion valve is reduced; when the suction superheat is greater than b, the opening degree B2 of the second electronic expansion valve is increased; and when the opening degree B2 of the second electronic expansion valve is greater than the upper limit d, the opening degree B1 of the first electronic expansion valve is increased.

[0013] When the heat pump system is operating in heating mode: when the suction superheat is less than a, the opening degree B1 of the first electronic expansion valve is reduced; and when the opening degree B1 of the first electronic expansion valve is less than the lower limit c, the opening degree B2 of the second electronic expansion valve is reduced; when the suction superheat is greater than b, the opening degree B1 of the first electronic expansion valve is increased; and when the opening degree B1 of the first electronic expansion valve is greater than the upper limit d, the opening degree B2 of the second electronic expansion valve is increased.

[0014] In some implementations...

[0015] In the aforementioned detection step, after either decreasing or increasing the opening degree B1 of the first electronic expansion valve, the discharge temperature t of the compressor is also detected. _dis and exhaust superheat dt _dis ;

[0016] The control step, if the exhaust superheat and exhaust temperature simultaneously satisfy dt _dis ≥e and t _dis When ≤g, maintain this opening for T2 time, then check the intake superheat and exhaust superheat again; if not satisfied, in cooling mode, control the opening of the first electronic expansion valve to return to the previous opening and maintain it, and in heating mode, control the opening of the second electronic expansion valve to return to the previous opening and maintain it.

[0017] In some implementations...

[0018] The compressor includes a first main cylinder, a second main cylinder, and a supplementary air cylinder. The intake end of the supplementary air cylinder is the supplementary air end and is connected to the gas outlet end of the flash evaporator. The exhaust ends of the first main cylinder, the second main cylinder, and the supplementary air cylinder are all connected.

[0019] The indoor heat exchanger includes a second heat exchanger and a third heat exchanger. The second heat exchanger can be connected to the second main cylinder, and the third heat exchanger can be connected to the first main cylinder. One end of the third heat exchanger is connected to the third electronic expansion valve and then to the pipeline where the second heat exchanger is located, so that the merged pipeline is connected to the second electronic expansion valve.

[0020] The control steps include controlling the third electronic expansion valve to adjust normally in cooling mode and controlling the opening of the third electronic expansion valve to the maximum in heating mode.

[0021] In some implementations...

[0022] The heat pump air conditioning system further includes a first four-way valve and a second four-way valve. The first four-way valve has its D end connected to the exhaust end of the compressor, its E end connected to the second heat exchanger, its S end connected to the second main cylinder, and its C end connected to the first heat exchanger. The second four-way valve has its D end connected to the exhaust end of the compressor, its E end connected to the third heat exchanger, its S end connected to the first main cylinder, and its C end connected to the first heat exchanger.

[0023] In some implementations...

[0024] The detection step, in cooling mode, involves detecting the intake superheat dt of the first master cylinder. suc_l and the intake superheat dt of the second master cylinder suc_h ,

[0025] The control step, when dt suc_h <a and dt suc_l When <a, reduce the opening B2 of the second electronic expansion valve. If the opening B2 of the second electronic expansion valve satisfies B2>c, maintain this opening for a time T2, and then recalculate the superheat. Otherwise, reduce the opening B1 of the first electronic expansion valve.

[0026] When dt suc_h >b and dt suc_l When the value is greater than b, increase the opening of the second electronic expansion valve B2. If the opening of the second electronic expansion valve B2 satisfies B2 < d, maintain this opening for a time T2, and then recalculate the superheat. Otherwise, increase the opening of the first electronic expansion valve B1.

[0027] In some implementations...

[0028] The detection step, in heating mode, involves detecting the intake superheat dt of the second master cylinder. suc_h ,

[0029] The control step, when dt suc_hWhen <a, reduce the opening B1 of the first electronic expansion valve. If the opening B1 of the first electronic expansion valve satisfies B1>c, maintain this opening for a time T2, and then recalculate the intake superheat. Otherwise, reduce the opening B2 of the second electronic expansion valve.

[0030] When dt suc_h When the value is greater than b, increase the opening of the first electronic expansion valve B1. If the opening of the first electronic expansion valve B1 satisfies B1 < d, maintain this opening for a time T2, and then recalculate the superheat. Otherwise, increase the opening of the second electronic expansion valve B2.

[0031] In some implementations...

[0032] When the cooling mode satisfies a≤dt suc_h ≤b and a≤dt suc_l When b ≤ b, keep the openings of the first, second, and third electronic expansion valves unchanged for time T3; when in heating mode, a ≤ dt suc_h When ≤b, keep the opening of both the first electronic expansion valve and the second electronic expansion valve unchanged, and run for time T3.

[0033] In some implementations...

[0034] The control steps, in cooling mode, occur before controlling the first electronic expansion valve and after the start-up operation time T2, when dt suc_h >b and a≤dt suc_l When a ≤ b, increase the opening of the second electronic expansion valve B2 and decrease the opening of the third electronic expansion valve B3, where a < b;

[0035] When dt suc_h <a and a≤dt suc_l When ≤b, decrease the opening of the second electronic expansion valve B2 and simultaneously increase the opening of the third electronic expansion valve B3;

[0036] When dt suc_h <a and dt suc_l When >b, increase the opening of the third electronic expansion valve B3;

[0037] a≤dt suc_h ≤b and dt suc_l When <a, reduce the opening of the second electronic expansion valve B2 and simultaneously reduce the opening of the third electronic expansion valve B3;

[0038] a≤dt suc_h ≤b and dt suc_l When >b, increase the opening of the second electronic expansion valve B2 and simultaneously increase the opening of the third electronic expansion valve B3;

[0039] dt suc_h>b and dt suc_l When <a, reduce the opening degree B3 of the third electronic expansion valve.

[0040] In some implementations...

[0041] The detection step involves detecting the indoor and outdoor ambient temperatures after the heat pump system is turned on.

[0042] The control steps determine the compressor operating frequency f, indoor fan speed, outdoor fan speed, and the initial opening degree of the first electronic expansion valve, the initial opening degree of the second electronic expansion valve, and the initial opening degree of the third electronic expansion valve based on the indoor ambient temperature, outdoor ambient temperature, set temperature, and set indoor unit fan speed.

[0043] In some implementations...

[0044] The detection steps involve detecting the compressor's suction temperature, discharge temperature, indoor ambient temperature, outdoor ambient temperature, and compressor frequency f after the compressor has been running for T1 time.

[0045] The control steps involve calculating the first specified opening degree of the first electronic expansion valve, the second specified opening degree of the second electronic expansion valve, and the third specified opening degree of the third electronic expansion valve according to the electronic expansion valve control algorithm, and controlling and adjusting the opening degree B1 of the first electronic expansion valve to the first specified opening degree, controlling and adjusting the opening degree B2 of the second electronic expansion valve to the second specified opening degree, and controlling and adjusting the opening degree B3 of the third electronic expansion valve to the third specified opening degree.

[0046] In some implementations...

[0047] The electronic expansion valve control algorithm is as follows: based on the detected refrigeration system parameters and compressor parameters, as well as the set parameters of the compressor, electronic expansion valve, and refrigerant, the refrigerant mass flow rate M of the electronic expansion valve is calculated. r Inlet and outlet pressure difference Δp r Import density ρ r,i Flow coefficient k c Then, the corresponding air flow rate V corresponding to the refrigerant flow rate is calculated. a,o And from this, the opening degree n of the electronic expansion valve can be calculated;

[0048] The relationship is as follows:

[0049] The relationship between the air volume flow rate and the refrigerant mass flow rate of the electronic expansion valve is as follows:

[0050]

[0051] The relationship between the opening degree of the electronic expansion valve and the air volume flow rate is as follows:

[0052] n=(-C1+(C1^2-4*C2*(C0-V a,o ))^0.5) / (2*C2), where C1, C2 and C0 are all constants.

[0053] In some implementations...

[0054] When the cooling mode satisfies a≤dt suc_h ≤b and a≤dt suc_l ≤b, and run for time T3; or in heating mode, satisfy a≤dt suc_h When ≤b, and after running for time T3;

[0055] The detection step involves detecting the indoor and outdoor ambient temperatures again, and adjusting the compressor operating frequency, indoor fan speed, and outdoor fan speed based on the indoor ambient temperature, the outdoor ambient temperature, the set temperature, and the set indoor unit fan speed, and detecting the frequency change value Δf of the compressor before and after the adjustment;

[0056] In the control steps, if the frequency change value Δf≤h, the opening degree of the first electronic expansion valve, the second electronic expansion valve, and the third electronic expansion valve is adjusted according to the intake superheat and exhaust superheat; otherwise, the opening degree of the first electronic expansion valve, the second electronic expansion valve, and the third electronic expansion valve is recalculated according to the electronic expansion valve control algorithm.

[0057] In some implementations...

[0058] The value ranges from 2 to 10 minutes for T1, 0.5 to 3 minutes for T2, 0 to 5 minutes for T3, 1 to 5℃ for a, 2 to 6℃ for b, 10 to 15℃ for e, 95 to 115℃ for g, and 3 to 10Hz for h.

[0059] The control method for a heat pump air conditioning system provided by this invention has the following beneficial effects:

[0060] 1. This invention detects the compressor's suction superheat and, under different operating modes, reduces the opening of the second or first electronic expansion valve when the suction superheat is less than 'a', and further reduces the opening of the first or second electronic expansion valve when the opening is less than the lower limit 'c', thereby increasing the compressor's suction superheat. Furthermore, under different operating modes, it increases the opening of the second or first electronic expansion valve when the suction superheat is greater than 'b', and further reduces the refrigerant flow into the compressor's suction port when the opening is greater than the upper limit 'd', thus decreasing the compressor's suction superheat. Therefore, it can select the most suitable refrigerant flow rate to meet the system's operation, ensuring optimal system performance, maximizing cooling or heating capacity, and maximizing COP.

[0061] 2. The present invention further detects the discharge temperature t of the compressor by adjusting the opening degree B1 of the first electronic expansion valve to a smaller or larger position. _dis and exhaust superheat dt _dis If the exhaust superheat and exhaust temperature simultaneously satisfy dt _dis ≥e and t _dis When the temperature is ≤g, maintain this opening for time T2, then re-evaluate the suction superheat and discharge superheat. If not satisfied, in cooling mode, control the opening of the first electronic expansion valve to return to the previous opening and maintain it; in heating mode, control the opening of the second electronic expansion valve to return to the previous opening and maintain it. This allows for further control of the opening of the first or second electronic expansion valve based on the compressor's discharge superheat and discharge temperature, and in different operating modes. This improves the control accuracy of multiple electronic expansion valves and enables the selection of the most suitable refrigerant flow rate to meet the system's operating requirements while satisfying the discharge temperature and discharge superheat. This ensures that the system operates at its optimal performance under safe and reliable conditions, maximizing the cooling or heating capacity and further maximizing the COP.

[0062] 3. The present invention also includes a third electronic expansion valve installed on the pipeline connected to the third heat exchanger, and in cooling mode, before controlling the first electronic expansion valve and after the start-up operation time T2, the intake superheat dt of the second main cylinder is... suc_h and intake superheat dt of the first master cylinder suc_lThe system compares the values ​​with the first preset value a and the second preset value b, and controls the opening of the second electronic expansion valve B2 and the opening of the third electronic expansion valve B3 to be increased or decreased based on the comparison results. This allows the openings of the second and third electronic expansion valves to be varied according to the intake superheat of different cylinders, improving the control accuracy of multiple electronic expansion valves. Furthermore, it enables the selection of the most suitable refrigerant flow rate to meet the system's operation while satisfying the intake superheat of different cylinders, ensuring that the system operates at its best performance, maximizing the cooling or heating capacity, and further maximizing the COP.

[0063] 4. The compressor of this invention adopts a three-cylinder parallel configuration, wherein two main cylinders are connected to two evaporators respectively, and the parallel injection cylinder is connected to the outlet of the flash evaporator; the evaporator adopts a multi-row evaporator, which is divided into front and rear rows for use. The evaporation temperatures of the two evaporators are different, forming a stepped heat exchange effect, which can reduce the temperature difference between the heat exchanger and the inlet air, improve the heat exchange efficiency, and this invention also uses a method based on real-time calculation of the opening degree of the electronic expansion valve and superheat feedback control based on the temperature sensor and frequency, which can shorten the intermediate control process, accelerate the adjustment convergence process, improve the accuracy and reliability of system control, and thus improve the energy efficiency of system operation. Attached Figure Description

[0064] Figure 1 This is a schematic diagram of the cooling operation mode of the heat pump air conditioning system of the present invention;

[0065] Figure 2 This is a schematic diagram of the heating operation mode of the heat pump air conditioning system of the present invention;

[0066] Figure 3 This is a flowchart of the cooling operation control logic of the heat pump air conditioning system of the present invention;

[0067] Figure 4 This is a flowchart of the heating operation control logic of the heat pump air conditioning system of the present invention.

[0068] The attached figures are labeled as follows:

[0069] 1. Compressor; 1a. Air supply cylinder; 1b. First main cylinder; 1c. Second main cylinder; 2. First four-way valve; 3. Second four-way valve; 4. First heat exchanger; 5. First electronic expansion valve; 6. Flash generator; 7. Second electronic expansion valve; 8. Third electronic expansion valve; 9. Second heat exchanger; 10. Third heat exchanger. Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0072] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0073] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0074] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0075] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0076] like Figure 1-4 As shown, the present invention provides a control method for a heat pump air conditioning system, which includes:

[0077] The heat pump air conditioning system includes a compressor, a first heat exchanger 4, a first throttling device (preferably a first electronic expansion valve 5), a flash evaporator 6, a second throttling device (preferably a second electronic expansion valve 7), and an indoor heat exchanger. The flash evaporator 6 is connected between the first electronic expansion valve 5 and the second electronic expansion valve 7. The gas outlet end of the flash evaporator 6 is connected to the gas supply end of the compressor. One end of the first heat exchanger 4 is connected to the first electronic expansion valve 5, and the other end is connected to the exhaust end or intake end of the compressor. The indoor heat exchanger is connected between the second electronic expansion valve 7 and the exhaust end or intake end of the compressor.

[0078] The control method includes:

[0079] The detection step involves detecting the suction superheat of the compressor.

[0080] The control steps involve adjusting the opening of the first electronic expansion valve 5 and the opening of the second electronic expansion valve 7 according to the intake superheat.

[0081] The judgment step is to determine whether the inhalation superheat is less than the first preset value a and whether it is greater than the second preset value b, where b>a>0;

[0082] The control steps, when the heat pump system is operating in cooling mode: when the suction superheat is less than a, the opening degree B2 of the second electronic expansion valve 7 is reduced; and when the opening degree B2 of the second electronic expansion valve is less than the lower limit c, the opening degree B1 of the first electronic expansion valve 5 is reduced; when the suction superheat is greater than b, the opening degree B2 of the second electronic expansion valve 7 is increased; and when the opening degree B2 of the second electronic expansion valve is greater than the upper limit d, the opening degree B1 of the first electronic expansion valve 5 is increased.

[0083] When the heat pump system is operating in heating mode: when the suction superheat is less than a, the opening B1 of the first electronic expansion valve 5 is reduced; and when the opening B1 of the first electronic expansion valve 5 is less than the lower limit c, the opening B2 of the second electronic expansion valve 7 is reduced; when the suction superheat is greater than b, the opening B1 of the first electronic expansion valve 5 is increased; and when the opening B1 of the first electronic expansion valve is greater than the upper limit d, the opening B2 of the second electronic expansion valve 7 is increased.

[0084] This invention detects the compressor's suction superheat and, under different operating modes, reduces the opening of the second or first electronic expansion valve when the suction superheat is less than 'a', and further reduces the opening of the first or second electronic expansion valve when the opening is less than the lower limit 'c', thereby increasing the compressor's suction superheat. Furthermore, under different operating modes, it increases the opening of the second or first electronic expansion valve when the suction superheat is greater than 'b', and further reduces the refrigerant flow into the compressor's suction port when the opening is greater than the upper limit 'd', thus decreasing the compressor's suction superheat. Therefore, it can select the most suitable refrigerant flow rate to meet the system's operating requirements, ensuring optimal system performance, maximizing cooling or heating capacity, and maximizing COP.

[0085] In some implementations...

[0086] In the aforementioned detection step, after either decreasing or increasing the opening degree B1 of the first electronic expansion valve, the discharge temperature t of the compressor is also detected. _dis and exhaust superheat dt _dis ;

[0087] The control step, if the exhaust superheat and exhaust temperature simultaneously satisfy dt _dis ≥e and t _disWhen ≤g, maintain this opening for time T2, and then re-evaluate the intake superheat and exhaust superheat; if not satisfied, in cooling mode, control the opening of the first electronic expansion valve to return to the previous opening and maintain it, and in heating mode, control the opening of the second electronic expansion valve to return to the previous opening and maintain it.

[0088] The present invention further detects the discharge temperature t of the compressor by adjusting the opening degree B1 of the first electronic expansion valve to be smaller or larger. _dis and exhaust superheat dt _dis If the exhaust superheat and exhaust temperature simultaneously satisfy dt _dis ≥e and t _dis When the value is ≤g, maintain this opening for time T2, then re-evaluate the suction superheat and discharge superheat. If the conditions are not met, it indicates that the opening of the first electronic expansion valve is over-adjusted. In cooling mode, control the opening of the first electronic expansion valve to return to the previous opening and maintain it. In heating mode, control the opening of the second electronic expansion valve to return to the previous opening and maintain it. This allows for further control of the opening of the first or second electronic expansion valve by adjusting the compressor's discharge superheat and discharge temperature under different operating modes. This improves the control accuracy of multiple electronic expansion valves and enables the selection of the most suitable refrigerant flow rate to meet the system's operating requirements while satisfying the discharge superheat. This ensures that the system operates at its best performance under safe and reliable conditions, maximizing the cooling or heating capacity and further maximizing the COP.

[0089] In some implementations...

[0090] The compressor 1 includes a first main cylinder 1b, a second main cylinder 1c, and a supplementary cylinder 1a. The intake end of the supplementary cylinder 1a is the supplementary end and is connected to the gas outlet end of the flash generator 6. The exhaust ends of the first main cylinder 1b, the second main cylinder 1c, and the supplementary cylinder 1a are all connected.

[0091] The indoor heat exchanger includes a second heat exchanger 9 and a third heat exchanger 10. The second heat exchanger 9 can be connected to the second main cylinder 1c, and the third heat exchanger 10 can be connected to the first main cylinder 1b. One end of the third heat exchanger 10 is connected to a third throttling device (preferably a third electronic expansion valve 8) and then connected to the pipeline where the second heat exchanger 9 is located, so that the merged pipeline is connected to the second electronic expansion valve 7.

[0092] In the control steps, the third electronic expansion valve 8 is controlled to adjust normally in the cooling mode, and in the heating mode, the opening of the third electronic expansion valve 8 is controlled to be adjusted to the maximum.

[0093] The compressor of this invention uses three compression cylinders connected in parallel, wherein two main cylinders are connected to two evaporators respectively, and the parallel injection cylinder is connected to the outlet of the flash evaporator; the evaporator uses a multi-row evaporator divided into front and rear rows of evaporators, and the evaporation temperature of the two evaporators is different, forming a stepped heat exchange effect, which can reduce the temperature difference between the heat exchanger and the inlet air and improve the heat exchange efficiency.

[0094] In some implementations...

[0095] The heat pump air conditioning system also includes a first four-way valve 2 and a second four-way valve 3. The first four-way valve 2 has its D end connected to the exhaust end of the compressor 1, its E end connected to the second heat exchanger 9, its S end connected to the second main cylinder 1c, and its C end connected to the first heat exchanger 4. The second four-way valve 3 has its D end connected to the exhaust end of the compressor 1, its E end connected to the third heat exchanger 10, its S end connected to the first main cylinder 1b, and its C end connected to the first heat exchanger 4.

[0096] This is a further preferred structural form of the heat pump air conditioning system of the present invention. Through the structure of two four-way valves and the above connection method, the three compression cylinders can be connected and switched with the first, second and third heat exchangers respectively, effectively realizing the dual-temperature evaporative cooling structure during refrigeration, and improving the performance and effect of refrigeration.

[0097] Figure 1 This invention provides a schematic diagram of the cooling operation mode of a heat pump air conditioning system. The system includes a first refrigerant circuit, a second refrigerant circuit, and a third refrigerant circuit. The first refrigerant circuit consists of a compressor first main cylinder 1b, a first four-way valve 2, a first heat exchanger 4, a first electronic expansion valve 5, a flash evaporator 6, a second electronic expansion valve 7, a second heat exchanger 9, and an auxiliary piping system. The second refrigerant circuit consists of a compressor second main cylinder 1c, a second four-way valve 3, a first heat exchanger 4, a first electronic expansion valve 5, a flash evaporator 6, a second electronic expansion valve 7, a third electronic expansion valve 8, a third heat exchanger 10, and an auxiliary piping system. The third refrigerant circuit consists of a compressor parallel replenishment cylinder 1a, a first four-way valve 2, a first heat exchanger 4, a first electronic expansion valve 5, a flash evaporator 6, and an auxiliary piping system.

[0098] In this operating mode, the system works as follows: the slide valves of the first four-way valve 2 and the second four-way valve 3 move to the left, connecting the E and S ends and the D and C ends. The first electronic expansion valve 5, the second electronic expansion valve 7, and the third electronic expansion valve 8 open and are controlled according to logic. The high-temperature, high-pressure refrigerant gas discharged from the first main cylinder 1b of the compressor mixes with the high-temperature, high-pressure refrigerant gas discharged from the second main cylinder 1c and the parallel supplementary cylinder 1a of the compressor, then flows through the first four-way valve 2 and the second four-way valve 3 respectively. After merging again, it enters the first heat exchanger 4. After the refrigerant is cooled and condensed, it is throttled to an intermediate pressure state by the first electronic expansion valve 5 and enters the flash evaporator 6. In the flash evaporator... The gas and liquid are separated into saturated or near-saturated gas and liquid. The saturated / near-saturated gas enters the compressor parallel gas cylinder 1a from the gas replenishment branch to complete the third refrigerant cycle. The saturated / near-saturated liquid is divided into two paths after passing through the second electronic expansion valve 7. One path enters the second heat exchanger 9, where it absorbs heat from the indoor air and evaporates. Then, it passes through the first four-way valve 2 and enters the second main cylinder 1c of the compressor to complete the first refrigerant cycle. The other path passes through the third electronic expansion valve 8 and enters the third heat exchanger 10, where it absorbs heat from the indoor air and evaporates. Then, it passes through the second four-way valve 3 and enters the first main cylinder 1b of the compressor to complete the second refrigerant cycle.

[0099] Figure 2 This invention provides a schematic diagram of the heating operation mode of a heat pump air conditioning system. The system includes a first refrigerant circuit, a second refrigerant circuit, and a third refrigerant circuit. The first refrigerant circuit consists of a compressor first main cylinder 1b, a first four-way valve 2, a second heat exchanger 9, a second electronic expansion valve 7, a flash evaporator 6, a first electronic expansion valve 5, a first heat exchanger 4, and an auxiliary piping system. The second refrigerant circuit consists of a compressor second main cylinder 1c, a second four-way valve 3, a third heat exchanger 10, a third electronic expansion valve 8, a second electronic expansion valve 7, a flash evaporator 6, a first electronic expansion valve 5, a first heat exchanger 4, and an auxiliary piping system. The third refrigerant circuit consists of a compressor parallel replenishment cylinder 1a, a first four-way valve 2, a second heat exchanger 9, a second electronic expansion valve 7, a flash evaporator 6, and an auxiliary piping system.

[0100] In this operating mode, the system works as follows: the slide valves of the first four-way valve 2 and the second four-way valve 3 move to the right, connecting terminals E and D, and terminals S and C. The third electronic expansion valve 8 is fully open. The first electronic expansion valve 5 and the second electronic expansion valve 7 open and are controlled according to logic. The high-temperature, high-pressure refrigerant gas discharged from the first main cylinder 1b of the compressor mixes with the high-temperature, high-pressure refrigerant gas discharged from the second main cylinder 1c and the parallel supplementary cylinder 1a of the compressor and is then divided into two paths. One path passes through the first four-way valve 2 and enters the second heat exchanger 9, where the refrigerant is cooled and condensed. The second path passes through the second four-way valve 3 and enters the third heat exchanger 10, where the refrigerant is cooled. After condensation, the refrigerant liquid, after merging with the second electronic expansion valve 7, is throttled to an intermediate pressure state and enters the flash evaporator 6. In the flash evaporator, the gas and liquid are separated into saturated or near-saturated gas and liquid. The saturated / near-saturated gas enters the compressor parallel gas cylinder 1a from the gas supply branch to complete the third refrigerant cycle. The saturated / near-saturated liquid enters the first heat exchanger 4 after passing through the first electronic expansion valve 5, where it absorbs heat from the outdoor air and evaporates. Then, it enters the second main cylinder 1c and the first main cylinder 1b of the compressor through the first four-way valve 2 and the second four-way valve 3 respectively, completing the first and second refrigerant cycles.

[0101] In some implementations...

[0102] The detection step, in cooling mode, involves detecting the intake superheat dt of the first master cylinder 1b. suc_l and the intake superheat dt of the second master cylinder 1c suc_h ,

[0103] The control step, when dt suc_h <a and dt suc_l When <a, reduce the opening B2 of the second electronic expansion valve. If the opening B2 of the second electronic expansion valve satisfies B2>c, maintain this opening for a time T2, and then recalculate the superheat. Otherwise, reduce the opening B1 of the first electronic expansion valve.

[0104] When dt suc_h >b and dt suc_l When the value is greater than b, increase the opening of the second electronic expansion valve B2. If the opening of the second electronic expansion valve B2 satisfies B2 < d, maintain this opening for a time T2, and then recalculate the superheat. Otherwise, increase the opening of the first electronic expansion valve B1.

[0105] This invention relates to a heat pump air conditioning system in three-cylinder mode and cooling mode, where the opening of the first and second electronic expansion valves is controlled based on the suction superheat of the first and second main cylinders. In cooling mode, when the suction superheat of both cylinders is too low, the opening of the second electronic expansion valve is reduced to increase the suction superheat. Furthermore, when the opening of the second electronic expansion valve is too low (below a lower limit), the opening of the first electronic expansion valve is reduced to increase the suction superheat. In cooling mode, when the suction superheat of both cylinders is too high, the opening of the second electronic expansion valve is increased to decrease the suction superheat. Furthermore, when the opening of the second electronic expansion valve is too high (above an upper limit), the opening of the first electronic expansion valve is increased to decrease the suction superheat. This improves the control accuracy of multiple electronic expansion valves in cooling mode, enabling the selection of the most suitable refrigerant flow rate to meet the system's operation while satisfying the suction superheat of different cylinders. This ensures optimal system performance, maximizing cooling capacity and further maximizing COP.

[0106] In some implementations...

[0107] The detection step, in heating mode, involves detecting the intake superheat dt of the second master cylinder 1c. suc_h (At this time, the intake superheat of the first master cylinder 1b and the second master cylinder 1c is the same, as both draw refrigerant from the first heat exchanger 4. Therefore, the intake superheat of the first master cylinder 1b can also be detected here.)

[0108] The control step, when dt suc_h When <a, reduce the opening B1 of the first electronic expansion valve. If the opening B1 of the first electronic expansion valve satisfies B1>c, maintain this opening for a time T2, and then recalculate the intake superheat. Otherwise, reduce the opening B2 of the second electronic expansion valve.

[0109] When dt suc_h When the value is greater than b, increase the opening of the first electronic expansion valve B1. If the opening of the first electronic expansion valve B1 satisfies B1 < d, maintain this opening for a time T2, and then recalculate the superheat. Otherwise, increase the opening of the second electronic expansion valve B2.

[0110] This invention relates to a heat pump air conditioning system in three-cylinder mode and in heating mode, where the opening of the first and second electronic expansion valves is controlled based on the suction superheat of the second main cylinder. In heating mode, when the suction superheat of the second main cylinder is too low, the opening of the first electronic expansion valve is reduced to increase the suction superheat of both cylinders. Furthermore, when the opening of the first electronic expansion valve is below a lower limit, the opening of the second electronic expansion valve is reduced to increase both suction superheats. In heating mode, when the suction superheat of the second main cylinder is too high, the opening of the first electronic expansion valve is increased to decrease the suction superheat of both cylinders. Furthermore, when the opening of the first electronic expansion valve is above an upper limit, the opening of the second electronic expansion valve is increased to decrease the suction superheat of both cylinders. This improves the control accuracy of multiple electronic expansion valves in heating mode, enabling the selection of the most suitable refrigerant flow rate to meet the system's operation while satisfying the suction superheat of different cylinders. This ensures optimal system performance, maximizing heating capacity and further maximizing COP.

[0111] In some implementations...

[0112] When the cooling mode satisfies a≤dt suc_h ≤b and a≤dt suc_l When ≤b, it indicates that the openings of the three electronic expansion valves are in the target operating state. The openings of the first, second, and third electronic expansion valves remain unchanged for time T3. In heating mode, a≤dt is satisfied. suc_h When ≤b, it indicates that the opening of the three electronic expansion valves is in the target operating state. Keep the opening of the first electronic expansion valve and the second electronic expansion valve unchanged for time T3.

[0113] This is the preferred control form when the suction superheat of both cylinders in the refrigeration mode meets the condition range, and the opening of the three electronic expansion valves remains unchanged. In the heating mode, the suction superheat of the second main cylinder meets the condition range, and the opening of multiple electronic expansion valves remains unchanged, maintaining the current opening state and continuing to ensure the stable and reliable operation of the compressor.

[0114] In some implementations...

[0115] The control steps, in cooling mode, occur before controlling the first electronic expansion valve and after the start-up operation time T2, when dt suc_h >b and a≤dt suc_l When a ≤ b, increase the opening of the second electronic expansion valve B2 and decrease the opening of the third electronic expansion valve B3, where a < b;

[0116] When dt suc_h<a and a≤dt suc_l When ≤b, decrease the opening of the second electronic expansion valve B2 and simultaneously increase the opening of the third electronic expansion valve B3;

[0117] When dt suc_h <a and dt suc_l When >b, increase the opening of the third electronic expansion valve B3;

[0118] a≤dt suc_h ≤b and dt suc_l When <a, reduce the opening of the second electronic expansion valve B2 and simultaneously reduce the opening of the third electronic expansion valve B3;

[0119] a≤dt suc_h ≤b and dt suc_l When >b, increase the opening of the second electronic expansion valve B2 and simultaneously increase the opening of the third electronic expansion valve B3;

[0120] dt suc_h >b and dt suc_l When <a, reduce the opening degree B3 of the third electronic expansion valve.

[0121] The present invention also includes a third electronic expansion valve installed on the pipeline connected to the third heat exchanger, and in cooling mode, before controlling the first electronic expansion valve and after the start-up operation time T2, the intake superheat dt of the second main cylinder is increased. suc_h and intake superheat dt of the first master cylinder suc_l The system compares the values ​​with the first preset value a and the second preset value b, and controls the opening of the second electronic expansion valve B2 and the opening of the third electronic expansion valve B3 to be increased or decreased based on the comparison results. This allows the openings of the second and third electronic expansion valves to be varied according to the intake superheat of different cylinders, improving the control accuracy of multiple electronic expansion valves. Furthermore, it enables the selection of the most suitable refrigerant flow rate to meet the system's operation while satisfying the intake superheat of different cylinders, ensuring that the system operates at its best performance, maximizing the cooling capacity, and further maximizing the COP.

[0122] Figure 3 The present invention provides a flow chart of the cooling operation control logic for a heat pump air conditioning system, the specific control flow of which is as follows:

[0123] 1) Start-up cooling operation.

[0124] 2) Based on the indoor ambient temperature, outdoor ambient temperature, set temperature, and set indoor unit fan speed, determine the compressor operating frequency f, indoor fan speed, outdoor fan speed, and the initial opening degree of the three electronic expansion valves.

[0125] 3) After running for time T1, detect the temperature of each temperature sensor and the compressor frequency f. Calculate and adjust the openings B1, B2, and B3 of the first, second, and third electronic expansion valves according to the electronic expansion valve control algorithm. The value of T1 is in the range of 2-10 minutes.

[0126] 4) After running for time T2, calculate the intake superheat dt of the second master cylinder. suc_h First master cylinder intake superheat dt suc_l Exhaust superheat dt _dis The superheat of the intake air in the first and second master cylinders is judged, with T2 ranging from 0.5 to 3 minutes.

[0127] 5) When the intake superheat of the second and first master cylinders meets dt suc_h >b and a≤dt suc_l When a ≤ b, increase the opening of the second electronic expansion valve B2 and decrease the opening of the third electronic expansion valve B3. After adjustment, return to step 4). Where a < b, the value of a is in the range of 1-5℃ and the value of b is in the range of 2-6℃ (the values ​​of a and b are the same below).

[0128] 6) When the intake superheat of the second and first master cylinders meets dt suc_h <a and a≤dt suc_l When ≤b, decrease the opening of the second electronic expansion valve B2 and simultaneously increase the opening of the third electronic expansion valve B3. After adjustment, return to step 4.

[0129] 7) When the intake superheat of the second and first master cylinders meets dt suc_h <a and dt suc_l When >b, increase the opening of the third electronic expansion valve B3, and then return to step 4 after adjustment.

[0130] 8) When the intake superheat of the second and first master cylinders satisfies a≤dt suc_h ≤b and dt suc_l When <a, reduce the opening of the second electronic expansion valve B2 and simultaneously reduce the opening of the third electronic expansion valve B3. After adjustment, return to step 4.

[0131] 9) When the intake superheat of the second and first master cylinders satisfies a≤dt suc_h ≤b and dt suc_l When >b, increase the opening of the second electronic expansion valve B2 and simultaneously increase the opening of the third electronic expansion valve B3. After adjustment, return to step 4.

[0132] 10) When the intake superheat of the second and first master cylinders meets dt suc_h >b and dt suc_l When <a, reduce the opening of the third electronic expansion valve B3, and return to step 4 after adjustment.

[0133] 11) When the intake superheat of the second and first master cylinders meets dt suc_h <a and dt suc_l When <a, reduce the opening of the second electronic expansion valve B2. If the opening of the second electronic expansion valve B2 satisfies B2>c, then return to step 4) to recalculate the superheat. Otherwise, reduce the opening of the first electronic expansion valve B1 and proceed to step 12), where c is the lower limit of the opening.

[0134] 12) If the exhaust superheat and exhaust temperature simultaneously satisfy dt _dis ≥e and t _dis When ≤g, return to step 4) to re-evaluate the superheat; if not satisfied, it means that the opening of the first electronic expansion valve is in an over-adjusted state, the opening of the first electronic expansion valve returns to the previous opening and is maintained, and then returns to step 3), where the value range of e is 10-15℃ and the value range of g is 95-115℃.

[0135] 13) When the intake superheat of the second and first master cylinders meets dt suc_h >b and dt suc_l When the value is greater than b, increase the opening of the second electronic expansion valve B2. If the opening of the second electronic expansion valve B2 satisfies B2 < d, return to step 4) to recalculate the superheat. Otherwise, increase the opening of the first electronic expansion valve B1 and proceed to step 12), where d is the upper limit of the opening.

[0136] 14) When the intake superheat of both the second and first master cylinders does not meet the above conditions, i.e., a≤dt is satisfied. suc_h ≤b and a≤dt suc_l When ≤b, it means that the opening of the three electronic expansion valves is in the target operating state. Keep the opening of the three electronic expansion valves unchanged and run for T3 time, where the value of T3 ranges from 0 to 5 minutes.

[0137] 15) Recheck the indoor ambient temperature, outdoor ambient temperature, set temperature, and set indoor unit fan speed, and adjust the compressor operating frequency, indoor fan speed, and outdoor fan speed accordingly, and check the frequency change value Δf before and after adjustment.

[0138] 16) If the frequency change value Δf≤h, it is determined that the indoor and outdoor ambient temperature or the set temperature has not changed significantly, and return to step 4) to adjust the opening of the electronic expansion valve according to the superheat, where the value of h is in the range of 3-10Hz; otherwise, it is determined that the indoor and outdoor ambient temperature or the set temperature has changed significantly, and return to step 3) to recalculate the opening according to the electronic expansion valve control algorithm.

[0139] In some implementations...

[0140] The detection step involves detecting the indoor and outdoor ambient temperatures after the heat pump system is turned on.

[0141] The control steps determine the compressor operating frequency f, indoor fan speed, outdoor fan speed, and the initial opening degree of the first electronic expansion valve, the initial opening degree of the second electronic expansion valve, and the initial opening degree of the third electronic expansion valve based on the indoor ambient temperature, outdoor ambient temperature, set temperature, and set indoor unit fan speed.

[0142] This invention also calculates the compressor's operating frequency f, indoor fan speed, outdoor fan speed, and the initial opening degrees of the first, second, and third electronic expansion valves by detecting the indoor and outdoor ambient temperatures, as well as the set temperature and fan speed when the system is turned on. This enables the heat pump air conditioning system to quickly reach the desired target operating state or near the target operating state, improving the effect of precise control, allowing the system to reach the required operating state as soon as possible, reducing power consumption, and improving system energy efficiency.

[0143] In some implementations...

[0144] The detection steps involve detecting the compressor's suction temperature, discharge temperature, indoor ambient temperature, outdoor ambient temperature, and compressor frequency f after the compressor has been running for T1 time.

[0145] The control steps involve calculating the first specified opening degree of the first electronic expansion valve, the second specified opening degree of the second electronic expansion valve, and the third specified opening degree of the third electronic expansion valve according to the electronic expansion valve control algorithm, and controlling and adjusting the opening degree B1 of the first electronic expansion valve to the first specified opening degree, controlling and adjusting the opening degree B2 of the second electronic expansion valve to the second specified opening degree, and controlling and adjusting the opening degree B3 of the third electronic expansion valve to the third specified opening degree.

[0146] The specific electronic expansion valve control algorithm here is as follows: Based on the detected refrigeration system parameters (including condenser mid-pipe temperature, evaporator mid-pipe temperature, condenser outlet temperature, compressor suction temperature, etc.) and compressor parameters (frequency), as well as the set parameters of the compressor, electronic expansion valve, and refrigerant (compressor displacement, valve opening and air flow related parameters, refrigerant property related parameters), the refrigerant mass flow rate M of the electronic expansion valve is calculated. r Inlet and outlet pressure difference Δp r Import density ρ r,i Flow coefficient k c Then, the corresponding air flow rate V corresponding to the refrigerant flow rate is calculated. a,o And from this, the opening degree n of the electronic expansion valve can be calculated.

[0147] The main relationships are as follows:

[0148] The relationship between air volume flow rate and refrigerant mass flow rate of electronic expansion valve:

[0149]

[0150] The relationship between the opening degree of the electronic expansion valve and the air volume flow rate is as follows:

[0151] n=(-C1+(C1^2-4*C2*(C0-V a,o ))^0.5) / (2*C2), where C1, C2 and C0 are all constants.

[0152] This invention also calculates the specified opening degrees of the first, second, and third electronic expansion valves by detecting the indoor and outdoor ambient temperatures, as well as the compressor's suction and discharge temperatures and compressor frequency f after the system has been running for T1 time. This allows the heat pump air conditioning system to quickly reach the desired target operating state or near the target operating state after T1 time by using feedback data, improving the effectiveness of precise control, enabling the system to reach the required operating state as quickly as possible, reducing power consumption, and improving system energy efficiency. It also shortens the intermediate control process, accelerates the adjustment and convergence process, improves the accuracy and reliability of system control, and thus improves the energy efficiency of system operation.

[0153] In some implementations...

[0154] When the cooling mode satisfies a≤dt suc_h ≤b and a≤dt suc_l ≤b, and run for time T3; or in heating mode, satisfy a≤dt suc_h When ≤b, and after running for time T3;

[0155] The detection step involves detecting the indoor and outdoor ambient temperatures again, and adjusting the compressor operating frequency, indoor fan speed, and outdoor fan speed based on the indoor ambient temperature, the outdoor ambient temperature, the set temperature, and the set indoor unit fan speed, and detecting the frequency change value Δf of the compressor before and after the adjustment;

[0156] In the control steps, if the frequency change value Δf ≤ h, it is determined that the indoor and outdoor ambient temperature or the set temperature has not changed significantly, and the opening degree of the first electronic expansion valve, the second electronic expansion valve, and the third electronic expansion valve is adjusted according to the intake superheat and exhaust superheat; otherwise, it is determined that the indoor and outdoor ambient temperature or the set temperature has changed significantly, and the opening degree of the first electronic expansion valve, the second electronic expansion valve, and the third electronic expansion valve is recalculated according to the electronic expansion valve control algorithm.

[0157] This invention further improves the precision control effect by combining real-time calculation of the electronic expansion valve opening and superheat feedback control based on the temperature sensor and frequency after the system has been running for T3 time in a stable cooling or heating mode. This allows the system to quickly reach the desired target operating state or its vicinity after a period of stable operation through calculation and control, shortening the intermediate control process, accelerating the adjustment and convergence process, improving the accuracy and reliability of system control, and ultimately enhancing the energy efficiency of system operation.

[0158] In some implementations...

[0159] The value ranges from 2 to 10 minutes for T1, 0.5 to 3 minutes for T2, 0 to 5 minutes for T3, 1 to 5℃ for a, 2 to 6℃ for b, 10 to 15℃ for e, 95 to 115℃ for g, and 3 to 10Hz for h.

[0160] Conventional electronic expansion valve control methods cannot achieve decoupling control of the three electronic expansion valves in a dual-temperature parallel compression system. This invention combines three-cylinder parallel compression technology with staged heat exchange technology, allowing the advantages of both technologies to be superimposed, effectively improving system energy efficiency and heating capacity at low temperatures in winter, while also reducing system exhaust temperature and improving system reliability.

[0161] Figure 4 The present invention provides a flow chart of the heating operation control logic for a heat pump air conditioning system, the specific control flow of which is as follows:

[0162] 1) Start heating operation.

[0163] 2) Based on the indoor ambient temperature, outdoor ambient temperature, set temperature, and set indoor unit fan speed, determine the compressor operating frequency f, indoor fan speed, outdoor fan speed, and the initial opening degree of the three electronic expansion valves (the opening degree of the third electronic expansion valve is fixed to the maximum opening degree of this valve in heating mode).

[0164] 3) After running for time T1, detect the temperature of each temperature sensor and the compressor frequency f. Calculate and adjust the openings B1 and B2 of the first and second electronic expansion valves according to the electronic expansion valve control algorithm. The value of T1 is in the range of 2-10 minutes.

[0165] 4) After running for time T2, calculate the intake superheat dt of the second master cylinder. suc_h Exhaust superheat dt _dis The value of T2 ranges from 0.5 to 3 minutes.

[0166] 5) When the intake superheat of the second master cylinder meets dt suc_h If a > b, then increase the opening of the first electronic expansion valve B1 and proceed to step 6); otherwise, proceed to step 8). Where a < b, the value of a ranges from 1 to 5℃, and the value of b ranges from 2 to 6℃.

[0167] 6) If the opening degree B1 of the first electronic expansion valve satisfies B1 < d, then return to step 4) to recalculate the superheat; otherwise, increase the opening degree B2 of the second electronic expansion valve and proceed to step 7), where d is the upper limit of the opening degree.

[0168] 7) If the exhaust superheat and exhaust temperature simultaneously satisfy dt _dis ≥e and t _dis When ≤g, return to step 4) to re-determine the superheat; if not satisfied, it means that the opening of the second electronic expansion valve is in an over-adjusted state, the opening of the second electronic expansion valve returns to the previous opening and is maintained, and then returns to step 3), where the value range of e is 10-15℃ and the value range of g is 95-115℃.

[0169] 8) When the intake superheat of the second master cylinder meets dt suc_h If a < b, then reduce the opening of the first electronic expansion valve B1 and proceed to step 9); otherwise, proceed to step 10). Where a < b, the value of a ranges from 1 to 5℃, and the value of b ranges from 2 to 6℃.

[0170] 9) If the opening degree B1 of the first electronic expansion valve satisfies B1>c, then return to step 4) to recalculate the superheat; otherwise, reduce the opening degree B2 of the second electronic expansion valve and proceed to step 7), where c is the lower limit of the opening degree.

[0171] 10) When the superheat of the second master cylinder intake does not meet the above conditions, i.e., a≤dt suc_h When ≤b, it means that the opening of the three electronic expansion valves is in the target operating state. Keep the opening of the three electronic expansion valves unchanged and run for T3 time, where the value of T3 ranges from 0 to 5 minutes.

[0172] 11) Recheck the indoor ambient temperature, outdoor ambient temperature, set temperature, and set indoor unit fan speed, and adjust the compressor operating frequency, indoor fan speed, and outdoor fan speed accordingly, and check the frequency change value Δf before and after adjustment.

[0173] 12) If the frequency change value Δf≤h, it is determined that the indoor and outdoor ambient temperature or the set temperature has not changed significantly, and return to step 4) to adjust the opening of the electronic expansion valve according to the superheat, where the value of h is in the range of 3-10Hz; otherwise, it is determined that the indoor and outdoor ambient temperature or the set temperature has changed significantly, and return to step 3) to recalculate the opening according to the electronic expansion valve control algorithm.

[0174] For this system and similar multi-electronic expansion valve systems with cyclic operation, this invention proposes a novel control method that enables decoupled control of multiple electronic expansion valves. During the heat pump air conditioner startup phase or when indoor and outdoor temperatures fluctuate significantly, this control method calculates the opening degree of the electronic expansion valves in real time and quickly adjusts them to near their optimal opening degree. This shortens the adjustment time, improves the accuracy and reliability of system control, and ultimately enhances the energy efficiency of the system.

[0175] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A control method of a heat pump air conditioning system, characterized by: include: The heat pump air conditioning system includes a compressor (1), a first heat exchanger (4), a first electronic expansion valve (5), a flash evaporator (6), a second electronic expansion valve (7), and an indoor heat exchanger. The flash evaporator (6) is connected between the first electronic expansion valve (5) and the second electronic expansion valve (7). The gas outlet end of the flash evaporator (6) is connected to the gas supply end of the compressor (1). One end of the first heat exchanger (4) is connected to the first electronic expansion valve (5), and the other end is connected to the exhaust end or the intake end of the compressor (1). The indoor heat exchanger is connected between the second electronic expansion valve (7) and the exhaust end or the intake end of the compressor (1). The control method includes: The detection step is to detect the suction superheat of the compressor (1); The control steps involve adjusting the opening of the first electronic expansion valve (5) and the opening of the second electronic expansion valve (7) according to the intake superheat. The judgment step is to determine whether the inhalation superheat is less than the first preset value a and whether it is greater than the second preset value b, where b>a>0; The control steps are as follows: when the heat pump system is operating in cooling mode: when the suction superheat is less than a, the opening of the second electronic expansion valve (7) is reduced; and when the opening of the second electronic expansion valve (7) is less than the lower limit c, the opening of the first electronic expansion valve (5) is reduced; when the suction superheat is greater than b, the opening of the second electronic expansion valve (7) is increased; and when the opening of the second electronic expansion valve (7) is greater than the upper limit d, the opening of the first electronic expansion valve (5) is increased. When the heat pump system is operating in heating mode: when the suction superheat is less than a, the opening of the first electronic expansion valve (5) is reduced; and when the opening of the first electronic expansion valve (5) is less than the lower limit c, the opening of the second electronic expansion valve (7) is reduced; when the suction superheat is greater than b, the opening of the first electronic expansion valve (5) is increased; and when the opening of the first electronic expansion valve (5) is greater than the upper limit d, the opening of the second electronic expansion valve (7) is increased.

2. The control method for a heat pump air conditioning system according to claim 1, characterized in that: The detection step detects the discharge temperature t of the compressor (1) after the opening degree of the first electronic expansion valve (5) is reduced or after the opening degree of the first electronic expansion valve (5) is increased _dis and the discharge superheat degree dt _dis ; The control step, if the exhaust superheat and exhaust temperature simultaneously satisfy dt _dis ≥e and t _dis When ≤g, maintain this opening for T2 time, and then judge the intake superheat and exhaust superheat again; if not satisfied, in the cooling mode, control the opening of the first electronic expansion valve (5) to return to the previous opening and maintain it, and in the heating mode, control the opening of the second electronic expansion valve (7) to return to the previous opening and maintain it.

3. The control method for a heat pump air conditioning system according to claim 1, characterized in that: The compressor (1) includes a first main cylinder (1b), a second main cylinder (1c) and a supplementary cylinder (1a). The intake end of the supplementary cylinder (1a) is the supplementary end and is connected to the gas outlet end of the flash generator (6). The exhaust ends of the first main cylinder (1b), the second main cylinder (1c) and the supplementary cylinder (1a) are all connected. The indoor heat exchanger includes a second heat exchanger (9) and a third heat exchanger (10). The second heat exchanger (9) can be connected to the second main cylinder (1c), and the third heat exchanger (10) can be connected to the first main cylinder (1b). One end of the third heat exchanger (10) is connected to the third electronic expansion valve (8) and then connected to the pipeline where the second heat exchanger (9) is located, so that the merged pipeline is connected to the second electronic expansion valve (7). In the control steps, in the cooling mode, the third electronic expansion valve (8) is controlled to adjust normally, and in the heating mode, the opening degree of the third electronic expansion valve (8) is controlled to be adjusted to the maximum.

4. The control method for a heat pump air conditioning system according to claim 3, characterized in that: The heat pump air conditioning system also includes a first four-way valve (2) and a second four-way valve (3). The first four-way valve (2) has its D end connected to the exhaust end of the compressor (1), its E end connected to the second heat exchanger (9), its S end connected to the second main cylinder (1c), and its C end connected to the first heat exchanger (4). The second four-way valve (3) has its D end connected to the exhaust end of the compressor (1), its E end connected to the third heat exchanger (10), its S end connected to the first main cylinder (1b), and its C end connected to the first heat exchanger (4).

5. The control method for a heat pump air conditioning system according to claim 3, characterized in that: The detection step, in the refrigeration mode, respectively detects the suction superheat degree dt of the first main cylinder (1b) suc_l And the suction superheat degree dt of the second main cylinder (1c) suc_h , The control step, when dt suc_h <a and dt suc_l When <a, reduce the opening of the second electronic expansion valve (7). If the opening of the second electronic expansion valve (7) is >c, maintain this opening for a time T2, and then recalculate the superheat. Otherwise, reduce the opening of the first electronic expansion valve (5). When dt suc_h > b and dt suc_l > b, increase the opening of the second electronic expansion valve (7), and if the opening of the second electronic expansion valve (7) < d, maintain the opening for T2 time, and then calculate the superheat again, otherwise increase the opening of the first electronic expansion valve (5).

6. The control method for a heat pump air conditioning system according to claim 3, characterized in that: said detecting step, in the heating mode, detects the suction gas superheat degree dt of the second main cylinder (1c) suc_h , The control step, when dt suc_h When <a, reduce the opening of the first electronic expansion valve (5). If the opening of the first electronic expansion valve (5) is >c, maintain this opening for a time T2, and then recalculate the intake superheat. Otherwise, reduce the opening of the second electronic expansion valve (7). When dt suc_h If b > b, increase the opening of the first electronic expansion valve (5). If the opening of the first electronic expansion valve (5) < d, maintain the opening for T2, and then calculate the superheat again. Otherwise, increase the opening of the second electronic expansion valve (7).

7. The control method for a heat pump air conditioning system according to claim 5, characterized in that: When the cooling mode satisfies a≤dt suc_h ≤b and a≤dt suc_l When ≤b, keep the openings of the first electronic expansion valve (5), the second electronic expansion valve (7), and the third electronic expansion valve (8) unchanged, and run for time T3; when a≤dt is satisfied in heating mode. suc_h When ≤b, keep the opening of the first electronic expansion valve (5) and the second electronic expansion valve (7) unchanged, and run for time T3.

8. The control method for a heat pump air conditioning system according to claim 5, characterized in that: The control steps, in refrigeration mode, occur before controlling the first electronic expansion valve (5) and after the start-up operation time T2, when dt suc_h >b and a≤dt suc_l When a ≤ b, increase the opening of the second electronic expansion valve (7) and decrease the opening of the third electronic expansion valve (8), where a < b; When dt suc_h <a and a≤dt suc_l When ≤b, reduce the opening of the second electronic expansion valve (7) and simultaneously increase the opening of the third electronic expansion valve (8); When dt suc_h <a and dt suc_l When >b, increase the opening of the third electronic expansion valve (8); a < dt suc_h ≤ b and dt suc_l When a < b, reduce the opening of the second electronic expansion valve (7) and the opening of the third electronic expansion valve (8). a ≤ dt suc_h ≤ b and dt suc_l If b > a, increase the opening of the second electronic expansion valve (7) and the opening of the third electronic expansion valve (8). dt suc_h > b and dt suc_l When < a, reduce the opening of the third electronic expansion valve (8).

9. The control method for a heat pump air conditioning system according to any one of claims 1-8, characterized in that: The detection step involves detecting the indoor and outdoor ambient temperatures after the heat pump system is turned on. The control steps determine the compressor (1) operating frequency f, indoor fan speed, outdoor fan speed, and the initial opening degree of the first electronic expansion valve (5), the initial opening degree of the second electronic expansion valve (7), and the initial opening degree of the third electronic expansion valve (8) based on the indoor ambient temperature, outdoor ambient temperature, set temperature, and set indoor unit fan speed.

10. The control method for a heat pump air conditioning system according to claim 9, characterized in that: The detection steps involve detecting the suction temperature, discharge temperature, indoor ambient temperature, outdoor ambient temperature, and compressor frequency f of the compressor (1) after the machine has been running for T1 time. The control steps involve calculating the first specified opening degree of the first electronic expansion valve (5), the second specified opening degree of the second electronic expansion valve (7), and the third specified opening degree of the third electronic expansion valve (8) according to the electronic expansion valve control algorithm, and controlling and adjusting the opening degree of the first electronic expansion valve (5) to the first specified opening degree, controlling and adjusting the opening degree of the second electronic expansion valve (7) to the second specified opening degree, and controlling and adjusting the opening degree of the third electronic expansion valve (8) to the third specified opening degree.

11. The control method for a heat pump air conditioning system according to claim 10, characterized in that: The electronic expansion valve control algorithm is: according to the detected refrigeration system parameters and compressor parameters and the set parameters of the compressor, electronic expansion valve and refrigerant, the refrigerant mass flow M of the electronic expansion valve is calculated r , the inlet and outlet pressure difference Δp r , the inlet density ρ r,i , the flow coefficient k c , and then the air flow V corresponding to the refrigerant flow is calculated a,o , and the opening degree n of the electronic expansion valve is calculated. The relationship is as follows: The relationship between the air volume flow rate and the refrigerant mass flow rate of the electronic expansion valve is as follows: ； The relationship between the opening degree of the electronic expansion valve and the air volume flow rate is as follows: n = (-C1+ (C1^2-4*C2*(C0-V a,o ))^0.5) / (2*C2), where C1, C2 and C0 are all constants.

12. The control method for a heat pump air conditioning system according to claim 10 or 11, characterized in that: when a ≤ dt suc_h ≤ b and a ≤ dt suc_l ≤ b, and after running for T3 time; or when a ≤ dt suc_h ≤ b in the heating mode, and after running for T3 time; The detection step involves detecting the indoor and outdoor ambient temperatures again, and adjusting the compressor (1) operating frequency, indoor fan speed and outdoor fan speed according to the indoor ambient temperature, the outdoor ambient temperature, the set temperature and the set indoor unit fan speed, and detecting the frequency change value Δf of the compressor (1) before and after the adjustment. In the control steps, if the frequency change value Δf≤h, the opening degree of the first electronic expansion valve (5), the second electronic expansion valve (7), and the third electronic expansion valve (8) are adjusted according to the intake superheat and exhaust superheat; otherwise, the opening degree of the first electronic expansion valve (5), the second electronic expansion valve (7), and the third electronic expansion valve (8) are recalculated according to the electronic expansion valve control algorithm.

13. The control method for a heat pump air conditioning system according to claim 12, characterized in that: The value ranges from 2 to 10 minutes for T1, 0.5 to 3 minutes for T2, 0 to 5 minutes for T3, 1 to 5℃ for a, 2 to 6℃ for b, 10 to 15℃ for e, 95 to 115℃ for g, and 3 to 10Hz for h.

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