A control method of a variable displacement compressor and an air conditioning system

Abstract

This invention discloses a control method for a variable capacity compressor and an air conditioning system. The control method includes: detecting the outdoor and indoor ambient temperatures of the air conditioning system; obtaining the set operating temperature of the air conditioning system; determining whether the variable capacity compressor meets the switching conditions for single-cylinder mode based on the outdoor ambient temperature; and controlling the variable capacity compressor to operate in single-cylinder mode when the switching conditions are met; and switching the variable capacity compressor to dual-cylinder mode or bipolar mode based on the indoor ambient temperature and the set operating temperature when the switching conditions are not met. Compared with the prior art, this invention fully integrates the outdoor ambient temperature, indoor ambient temperature, and set operating temperature to intelligently switch the variable capacity compressor to operate in single-cylinder mode, dual-cylinder mode, and bipolar mode, ensuring that the air conditioning system can maintain the best energy efficiency ratio and response speed under all operating conditions. It belongs to energy-saving hydraulic and pneumatic components.

Description

Technical Field

[0001] This invention relates to the field of compressor control, and in particular to a control method for a variable capacity compressor and an air conditioning system. Background Technology

[0002] In existing variable frequency air conditioners, variable capacity compressors typically employ simple start-stop control or a single variable frequency adjustment method. However, with the improvement of energy efficiency standards and the increasing demand for user comfort, variable capacity compressors are gradually becoming more popular due to their ability to provide a wider adjustment range and higher part-load efficiency.

[0003] However, existing control strategies for variable capacity compressors are often quite fixed. For example, they only switch to single-cylinder mode under low load and operate at full capacity under high load, lacking fine-grained differentiation of intermediate operating conditions. Especially for two-stage compression systems with intercoolers, existing control strategies for variable capacity compressors do not provide clear control schemes for balancing the energy efficiency of single-cylinder mode, the high energy efficiency of two-stage mode, and the strong cooling capacity of two-cylinder mode, and achieving a smooth transition between single-cylinder mode, two-cylinder mode, and two-stage mode under different temperature differences. This may lead to frequent mode switching of the variable capacity compressor, increased energy consumption, or unstable cooling performance.

[0004] Therefore, how to design a control method and air conditioning system for a variable capacity compressor that can intelligently switch the variable capacity compressor to work in single-cylinder mode, dual-cylinder mode, and bipolar mode, and avoid frequent mode switching of the variable capacity compressor, is a technical problem that the industry urgently needs to solve. Summary of the Invention

[0005] To address the problem that existing technologies lack clear switching schemes for single-cylinder, dual-cylinder, and bipolar modes, leading to frequent mode switching, increased energy consumption, or unstable cooling performance in variable capacity compressors, this invention proposes a control method and air conditioning system for a variable capacity compressor. This method intelligently switches the variable capacity compressor between single-cylinder, dual-cylinder, and bipolar modes by comprehensively considering outdoor ambient temperature, indoor ambient temperature, and the set operating temperature. This ensures that the air conditioning system maintains optimal energy efficiency and response speed under all operating conditions, and is an energy-saving hydraulic and pneumatic component.

[0006] The technical solution of this invention is to propose a control method for a variable displacement compressor, wherein the variable displacement compressor has a single-cylinder mode, a dual-cylinder mode, and a bipolar mode, and the control method includes:

[0007] Detect the outdoor and indoor ambient temperatures where the air conditioning system is located;

[0008] The system obtains the set operating temperature of the air conditioning system, determines whether the variable capacity compressor meets the switching conditions for single-cylinder mode based on the outdoor ambient temperature, and controls the variable capacity compressor to work in single-cylinder mode when the switching conditions for single-cylinder mode are met.

[0009] When the variable capacity compressor does not meet the switching conditions for single-cylinder mode, the variable capacity compressor is switched to dual-cylinder mode or bipolar mode according to the indoor ambient temperature and the set operating temperature.

[0010] Based on the above-mentioned solution, this invention provides a clear switching scheme for single-cylinder mode, dual-cylinder mode, and bipolar mode, which can balance the energy saving of single-cylinder mode, the high energy efficiency of bipolar mode, and the strong cooling capacity of dual-cylinder mode. It also achieves a smooth transition between single-cylinder mode, dual-cylinder mode, and bipolar mode under different temperature difference conditions, ensuring that the air conditioning system can maintain the best energy efficiency ratio and response speed under all operating conditions.

[0011] Furthermore, in this invention, determining whether the variable-capacity compressor meets the switching conditions for single-cylinder mode based on the outdoor ambient temperature includes:

[0012] When the outdoor ambient temperature is greater than the first preset threshold temperature, the current operating state of the air conditioning system is maintained;

[0013] After a preset threshold time, determine whether the outdoor ambient temperature is lower than the first preset threshold temperature;

[0014] If so, the variable capacity compressor is determined to meet the switching conditions for single-cylinder mode;

[0015] If not, it is determined that the variable capacity compressor does not meet the switching conditions for single-cylinder mode.

[0016] Based on the above solution, this invention determines the current load of the air conditioning system by the outdoor ambient temperature, and controls whether the variable capacity compressor operates in single-cylinder mode according to the current load of the air conditioning system. This ensures that the air conditioning system maintains stable operation in single-cylinder mode under low load conditions, meets the user's comfort needs, and takes into account the energy-saving performance of single-cylinder mode, thereby achieving energy efficiency optimization under low load conditions.

[0017] Furthermore, in this invention, switching the variable capacity compressor to operate in dual-cylinder mode or bipolar mode based on the indoor ambient temperature and the set operating temperature includes:

[0018] Calculate the temperature difference between the indoor ambient temperature and the set operating temperature;

[0019] Determine whether the temperature difference value is greater than the second preset threshold temperature. If so, control the variable capacity compressor to work in dual-cylinder mode.

[0020] If not, the variable capacity compressor is controlled to operate in bipolar mode.

[0021] Based on the above solution, this invention can switch the variable capacity compressor to work in dual-cylinder mode or bipolar mode under medium- and high load conditions according to the temperature difference between the indoor ambient temperature and the set operating temperature. It can take into account the high energy efficiency of bipolar mode and the strong cooling capacity of dual-cylinder mode, achieve a smooth transition between bipolar mode and dual-cylinder mode, and achieve energy efficiency optimization under medium- and high load conditions.

[0022] Furthermore, the operating frequency of the variable capacity compressor in this invention is adjusted according to the temperature difference between the indoor ambient temperature and the set operating temperature, as well as a PID algorithm.

[0023] Based on the above solution, this invention adjusts the operating frequency of the variable capacity compressor according to the temperature difference between the indoor ambient temperature and the set operating temperature and the PID algorithm, which can avoid noise and room temperature fluctuations caused by sudden frequency changes.

[0024] Furthermore, the output of the PID algorithm described in this invention is: ;

[0025] in, The temperature difference between the indoor ambient temperature and the set operating temperature. For proportional gain, For integral gain, This is the differential gain.

[0026] Based on the above scheme, this invention can determine the response sensitivity to temperature difference through proportional gain, eliminate long-term static temperature difference deviation through integral gain, predict the temperature difference change trend through differential gain, suppress overshoot to achieve smooth adjustment, and adjust the operating frequency of the variable capacity compressor through the output of the above PID algorithm, thereby avoiding noise and room temperature oscillation caused by frequency abrupt changes.

[0027] Furthermore, the calculation model for the operating frequency of the variable capacity compressor described in this invention is: f = fmin + (fmax - fmin)·Sigmoid[u(t)];

[0028] Where f is the operating frequency of the variable capacity compressor, fmin is the lower limit of the operating frequency of the variable capacity compressor, fmax is the upper limit of the operating frequency of the variable capacity compressor, u(t) is the output of the PID algorithm, and Sigmoid is the logistic function.

[0029] Based on the above-mentioned scheme, this invention ensures the stable operation of the variable capacity compressor within a safe frequency range by constraining the upper and lower limits of the operating frequency. Combined with the introduced PID algorithm for control, it ensures that the indoor ambient temperature can ultimately be accurately stabilized near the set operating temperature. This solves the problem of overcooling or overheating that may occur in traditional on / off control or simple frequency conversion control. Furthermore, it enables the prediction of temperature difference trends, allowing the variable capacity compressor's operating frequency to be reduced in advance when the indoor ambient temperature approaches the set operating temperature. This effectively prevents large temperature fluctuations due to inertia, thus ensuring user comfort. Compared to traditional step-like frequency regulation, the operating frequency change output by this invention is continuous and smooth, significantly reducing the start-stop shock and operating noise of the variable capacity compressor and extending the lifespan of its mechanical components.

[0030] Furthermore, the present invention also proposes an air conditioning system employing the above-mentioned control method for a variable capacity compressor, comprising a variable capacity compressor, a gas-liquid separator connected to the suction side of the variable capacity compressor, and a condenser connected to the discharge side of the variable capacity compressor, wherein the variable capacity compressor comprises at least a first compression cylinder, a second compression cylinder, and a cooler.

[0031] The variable displacement compressor can operate in single-cylinder mode, double-cylinder mode, and bipolar mode. In the single-cylinder mode, the first compression cylinder operates alone.

[0032] In the dual-cylinder mode, the first compression cylinder and the second compression cylinder work in parallel;

[0033] In the bipolar mode, the first compression cylinder and the second compression cylinder operate in series, and the cooler is placed between the first compression cylinder and the second compression cylinder to cool the refrigerant discharged from the first compression cylinder and transfer it to the second compression cylinder.

[0034] Based on the above-mentioned solution, this invention provides a variable capacity compressor with single-cylinder mode, dual-cylinder mode, and bipolar mode. In conjunction with the control method of the variable capacity compressor, the single-cylinder mode, dual-cylinder mode, and bipolar mode can be switched. This can balance the energy saving of single-cylinder mode, the high energy efficiency of bipolar mode, and the strong cooling capacity of dual-cylinder mode. It also achieves a smooth transition between single-cylinder mode, dual-cylinder mode, and bipolar mode under different temperature difference conditions, ensuring that the air conditioning system can maintain the best energy efficiency ratio and response speed under all operating conditions.

[0035] Furthermore, the air conditioning system described in this invention also includes a first four-way valve and a second four-way valve connected to the first compression cylinder and the second compression cylinder. The first four-way valve and the second four-way valve are used to adjust the refrigerant flow direction in the air conditioning system to switch the variable capacity compressor to operate in one of the following modes: single-cylinder mode, dual-cylinder mode, and bipolar mode.

[0036] Based on the above solution, the present invention simplifies the switching action of single-cylinder mode, dual-cylinder mode and bipolar mode to the control of the first four-way valve and the second four-way valve, without the need for additional pipeline layout and flow path switching. The overall switching scheme is simpler and more efficient, and can meet the stable control requirements of the present invention for switching between single-cylinder mode, dual-cylinder mode and bipolar mode.

[0037] Furthermore, the gas-liquid separator of the present invention has a first outlet and a second outlet, the first outlet being connected to the air inlet of the first compression cylinder, and the second outlet being connected to the first port of the first four-way valve.

[0038] The outlet of the first compression cylinder is connected to the third and fourth ports of the second four-way valve, the first port of the second four-way valve is connected to the cooler, and the second port of the second four-way valve and the outlet of the cooler are connected together to the second port of the first four-way valve.

[0039] The fourth port of the first four-way valve is connected to the air inlet of the second compression cylinder, and the third port of the first four-way valve and the air outlet of the second compression cylinder are connected to the condenser.

[0040] Based on the above-mentioned solution, this invention provides the connection relationship between the first and second compression cylinders and the first and second four-way valves in the variable capacity compressor. Based on this connection relationship, this invention can achieve the switching between single-cylinder mode, dual-cylinder mode, and bipolar mode by controlling only the first and second four-way valves. This makes the overall switching scheme simpler and more efficient, and meets the stable control requirements of this invention for switching between single-cylinder mode, dual-cylinder mode, and bipolar mode.

[0041] Furthermore, in this invention, when the variable capacity compressor operates in single-cylinder mode, the second port of the first four-way valve is connected to the third port, and the second port of the second four-way valve is connected to the fourth port.

[0042] When the variable capacity compressor is operating in dual-cylinder mode, the first port and the fourth port of the first four-way valve are connected, the second port and the third port are connected, and the second port and the fourth port of the second four-way valve are connected.

[0043] When the variable capacity compressor operates in bipolar mode, the second and fourth ports of the first four-way valve are connected, and the first and third ports of the second four-way valve are connected.

[0044] Based on the above-mentioned scheme, this invention provides specific control logic for switching between single-cylinder mode, dual-cylinder mode, and bipolar mode through a first four-way valve and a second four-way valve. Combined with the control method of the variable capacity compressor, the switching between single-cylinder mode, dual-cylinder mode, and bipolar mode can balance the energy saving of single-cylinder mode, the high energy efficiency of bipolar mode, and the strong cooling capacity of dual-cylinder mode. It also achieves a smooth transition between single-cylinder mode, dual-cylinder mode, and bipolar mode under different temperature difference conditions, ensuring that the air conditioning system can maintain the best energy efficiency ratio and response speed under all operating conditions.

[0045] This invention belongs to the category of energy-saving hydraulic and pneumatic components, and compared with the prior art, it has at least the following beneficial effects:

[0046] 1. This invention provides a clear switching scheme for single-cylinder mode, dual-cylinder mode, and bipolar mode, which can balance the energy saving of single-cylinder mode, the high energy efficiency of bipolar mode, and the strong cooling capacity of dual-cylinder mode. It also achieves a smooth transition between single-cylinder mode, dual-cylinder mode, and bipolar mode under different temperature difference conditions, ensuring that the air conditioning system can maintain the best energy efficiency ratio and response speed under all operating conditions.

[0047] 2. This invention uses the temperature difference between the indoor ambient temperature and the set operating temperature, combined with an introduced PID algorithm, to control the system. This ensures that the indoor ambient temperature is accurately stabilized near the set operating temperature, resolving the overcooling or overheating issues that may occur in traditional on / off control or simple frequency conversion control. Furthermore, it allows for prediction of temperature difference trends, enabling the reduction of the variable capacity compressor's operating frequency in advance when the indoor ambient temperature approaches the set operating temperature. This effectively prevents significant temperature fluctuations due to inertia, thus ensuring user comfort. Compared to traditional step-like frequency regulation, this invention provides a continuous and smooth change in the output operating frequency, significantly reducing start-stop shock and operating noise of the variable capacity compressor, and extending the lifespan of its mechanical components. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is the overall working logic of the control method for the variable capacity compressor in this invention;

[0050] Figure 2 This invention provides the control logic for switching between single-cylinder modes in the control method of the variable capacity compressor.

[0051] Figure 3 This invention provides the control logic for switching between dual-cylinder mode and bipolar mode in the control method of the variable capacity compressor.

[0052] Figure 4 The control flow of the variable capacity compressor control method of the present invention is shown in a specific embodiment.

[0053] Figure 5 This is a simplified schematic diagram of the variable displacement compressor in the present invention operating in single-cylinder mode;

[0054] Figure 6 This is a simplified schematic diagram of the variable displacement compressor in the present invention operating in dual-cylinder mode;

[0055] Figure 7 This is a simplified schematic diagram of the variable capacity compressor in the present invention operating in bipolar mode;

[0056] Figure 8 This is a schematic diagram of the connection of the air conditioning system at the variable capacity compressor in this invention;

[0057] Figure 9 This is a schematic diagram of the refrigerant flow direction when the variable capacity compressor of the present invention is operating in single-cylinder mode;

[0058] Figure 10 This is a schematic diagram of the refrigerant flow direction when the variable capacity compressor of the present invention is operating in dual-cylinder mode;

[0059] Figure 11 This is a schematic diagram of the refrigerant flow direction when the variable capacity compressor of the present invention is operating in bipolar mode;

[0060] Among them, 1 is a gas-liquid separator, 2 is a first four-way valve, 3 is a cooler, 4 is a second four-way valve, and 5 is a variable capacity compressor;

[0061] 11 is the first outlet of the gas-liquid separator, and 12 is the second outlet of the gas-liquid separator;

[0062] 21 is the first port of the first four-way valve, 22 is the second port of the first four-way valve, 23 is the third port of the first four-way valve, and 24 is the fourth port of the first four-way valve.

[0063] 41 is the first port of the second four-way valve, 42 is the second port of the second four-way valve, 43 is the third port of the second four-way valve, and 41 is the fourth port of the second four-way valve.

[0064] 51 is the first compression cylinder, and 52 is the second compression cylinder;

[0065] 511 is the air inlet of the first compression cylinder, and 512 is the air outlet of the first compression cylinder;

[0066] 521 is the air inlet of the second compression cylinder, and 522 is the air outlet of the second compression cylinder. Detailed Implementation

[0067] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0068] Therefore, a feature pointed out in this specification is used to describe one feature of one embodiment of the invention, and does not imply that every embodiment of the invention must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0069] The principles and structure of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0070] Existing control strategies for variable capacity compressors are often quite fixed. For example, they may switch to single-cylinder mode only at low loads and operate at full capacity at high loads, lacking a fine-grained distinction between intermediate operating conditions. Especially for two-stage compression systems with intercoolers, existing control strategies fail to provide a clear solution for balancing the energy efficiency of single-cylinder mode, the high energy efficiency of two-stage mode, and the powerful cooling capacity of two-cylinder mode, while also achieving a smooth transition between single-cylinder, two-cylinder, and two-stage modes under different temperature differences. This can lead to frequent mode switching, increased energy consumption, or unstable cooling performance.

[0071] To address the aforementioned issues, this invention proposes a control method for a variable capacity compressor. This method integrates outdoor ambient temperature, indoor ambient temperature, and set operating temperature to intelligently switch the variable capacity compressor between single-cylinder, dual-cylinder, and bipolar modes, ensuring that the air conditioning system maintains optimal energy efficiency ratio and response speed under all operating conditions.

[0072] Please see the appendix Figure 1 The control method for the variable capacity compressor proposed in this invention mainly includes the following steps:

[0073] Detect the outdoor and indoor ambient temperatures where the air conditioning system is located;

[0074] The system obtains the set operating temperature of the air conditioning system, determines whether the variable capacity compressor meets the switching conditions for single-cylinder mode based on the outdoor ambient temperature, and controls the variable capacity compressor to work in single-cylinder mode when the switching conditions for single-cylinder mode are met.

[0075] When the variable capacity compressor does not meet the switching conditions for single-cylinder mode, the variable capacity compressor will switch to dual-cylinder mode or bipolar mode according to the indoor ambient temperature and the set operating temperature.

[0076] As can be seen from the above scheme, when switching between single-cylinder mode, the present invention makes a judgment based on the outdoor ambient temperature; when switching between dual-cylinder mode and bipolar mode, it makes a judgment based on the indoor ambient temperature and the set operating temperature. That is, the variable capacity compressor control method provided by the present invention integrates the outdoor ambient temperature, the indoor ambient temperature, and the set operating temperature to intelligently switch the variable capacity compressor to work in single-cylinder mode, dual-cylinder mode, and bipolar mode.

[0077] Based on this, the system can switch between single-cylinder mode, dual-cylinder mode, and bipolar mode, balancing the energy efficiency of single-cylinder mode, the high energy efficiency of bipolar mode, and the strong cooling capacity of dual-cylinder mode. It also achieves a smooth transition between single-cylinder mode, dual-cylinder mode, and bipolar mode under different temperature difference conditions, ensuring that the air conditioning system can maintain the best energy efficiency ratio and response speed under all operating conditions.

[0078] Please see the appendix Figure 2 The method for determining whether a variable displacement compressor meets the switching conditions for single-cylinder mode in this invention includes:

[0079] When the outdoor ambient temperature is higher than the first preset threshold temperature, maintain the current operating state of the air conditioning system;

[0080] After a preset threshold time, determine whether the outdoor ambient temperature is lower than the first preset threshold temperature;

[0081] If so, then the variable displacement compressor is determined to meet the switching conditions for single-cylinder mode;

[0082] If not, then the variable displacement compressor is determined not to meet the switching conditions for single-cylinder mode.

[0083] Here, after maintaining the current operating state of the air conditioning system for a preset threshold time, it is determined whether the outdoor ambient temperature is still greater than the first preset threshold temperature. This is mainly used to determine the load of the air conditioning system. If the outdoor ambient temperature is continuously high (still higher than the first preset threshold temperature after the preset threshold time), it indicates that the air conditioning system is under high load. If the variable capacity compressor is allowed to work in single-cylinder mode at this time, it may not be able to meet the cooling demand under high load. Therefore, in this case, it is determined that the variable capacity compressor does not meet the switching conditions for single-cylinder mode.

[0084] If the outdoor ambient temperature is briefly high (and then drops below the first preset threshold temperature after a preset threshold time), it indicates that the air conditioning system is in a low-load state. At this time, there is no need for excessive cooling demand, and the variable capacity compressor can be operated in single-cylinder mode to take into account the energy-saving performance of single-cylinder mode.

[0085] The preset threshold time and the first preset threshold temperature can both be adjusted according to actual needs, and no specific limitations are made here.

[0086] Based on the above solution, this invention determines the current load of the air conditioning system by the outdoor ambient temperature, and controls whether the variable capacity compressor operates in single-cylinder mode according to the current load of the air conditioning system. This ensures that the air conditioning system maintains stable operation in single-cylinder mode under low load conditions, meets the user's comfort needs, and takes into account the energy-saving performance of single-cylinder mode, thereby achieving energy efficiency optimization under low load conditions.

[0087] Please see the appendix Figure 3 The present invention includes a scheme for switching the variable displacement compressor to operate in dual-cylinder mode or bipolar mode, comprising:

[0088] Calculate the temperature difference between the indoor ambient temperature and the set operating temperature;

[0089] Determine if the temperature difference is greater than the second preset threshold temperature. If so, control the variable capacity compressor to work in dual-cylinder mode.

[0090] If not, the variable displacement compressor will be controlled to operate in bipolar mode.

[0091] Here, the judgment of the temperature difference value and the second preset threshold temperature is to further combine the indoor ambient temperature and the set operating temperature to determine the load of the air conditioning system. If the indoor ambient temperature is much higher than the set operating temperature, that is, the temperature difference value is greater than the second preset threshold temperature, it means that the air conditioning system needs to lower the temperature more to meet the user's cooling needs. At this time, the air conditioning system can be identified as being in a high load state.

[0092] Conversely, if the indoor ambient temperature is higher than the set operating temperature, but the temperature difference is less than the second preset threshold temperature, it means that although the air conditioning system needs to cool down, it does not need to lower the temperature much to meet the user's cooling needs. At this time, the air conditioning system can be considered to be in a medium load state.

[0093] In this invention, the variable capacity compressor is controlled to operate in bipolar mode under medium load conditions, which can take into account the high energy efficiency of bipolar mode (intermediate cooling is performed between the two compression cylinders in bipolar mode, which can effectively reduce irreversible losses in the compression process and thus improve energy efficiency), and the variable capacity compressor is controlled to operate in dual-cylinder mode under high load conditions, which can take into account the strong cooling capacity of dual-cylinder mode to accelerate the cooling rate.

[0094] The second preset threshold temperature can be adjusted according to actual needs, and no specific limitation is made here.

[0095] In other words, based on the above solution, the present invention can switch the variable capacity compressor to work in dual-cylinder mode or bipolar mode under medium and high load conditions according to the temperature difference between the indoor ambient temperature and the set working temperature. It can take into account the high energy efficiency of bipolar mode and the strong cooling capacity of dual-cylinder mode, achieve a smooth transition between bipolar mode and dual-cylinder mode, and achieve energy efficiency optimization under medium and high load conditions.

[0096] As can be seen from the above introduction, the present invention provides a clear switching scheme for single-cylinder mode, dual-cylinder mode, and bipolar mode, which can balance the energy saving of single-cylinder mode, the high energy efficiency of bipolar mode, and the strong cooling capacity of dual-cylinder mode. It also achieves a smooth transition between single-cylinder mode, dual-cylinder mode, and bipolar mode under different temperature difference conditions, ensuring that the air conditioning system can maintain the best energy efficiency ratio and response speed under all operating conditions.

[0097] Furthermore, in this invention, the operating frequency of the variable capacity compressor is adjusted based on the temperature difference between the indoor ambient temperature and the set operating temperature, as well as a PID algorithm.

[0098] Here, the scheme for adjusting the operating frequency of the variable capacity compressor is applicable to the single-cylinder mode, dual-cylinder mode, and bipolar mode mentioned above. This invention introduces a PID algorithm to adjust the operating frequency of the variable capacity compressor, which can avoid noise and room temperature fluctuations caused by sudden frequency changes.

[0099] Specifically, the output of the PID algorithm in this invention is: ;

[0100] in, This is the temperature difference between the indoor ambient temperature and the set operating temperature. For proportional gain, For integral gain, This is the differential gain.

[0101] This invention uses a PID algorithm to adjust the operating frequency of a variable capacity compressor. It can determine the response sensitivity to temperature difference through proportional gain, eliminate long-term static temperature difference deviation through integral gain, predict the temperature difference change trend through differential gain, suppress overshoot to achieve a smooth adjustment process, and adjust the operating frequency of the variable capacity compressor through the output of the above PID algorithm, thus avoiding noise and room temperature oscillation caused by frequency abrupt changes.

[0102] Furthermore, the calculation model for the operating frequency of the variable capacity compressor in this invention is: f = fmin + (fmax -fmin)·Sigmoid[u(t)];

[0103] Where f is the operating frequency of the variable capacity compressor under high load, fmin is the lower limit of the operating frequency of the variable capacity compressor under high load, fmax is the upper limit of the operating frequency of the variable capacity compressor under high load, u(t) is the output of the PID algorithm under high load, and Sigmoid is the logistic function.

[0104] Based on the above-mentioned scheme, this invention ensures the stable operation of the variable capacity compressor within a safe frequency range by constraining the upper and lower limits of the operating frequency. Combined with the introduced PID algorithm for control, it ensures that the indoor ambient temperature can ultimately be accurately stabilized near the set operating temperature. This solves the problem of overcooling or overheating that may occur in traditional on / off control or simple frequency conversion control. Furthermore, it enables the prediction of temperature difference trends, allowing the variable capacity compressor's operating frequency to be reduced in advance when the indoor ambient temperature approaches the set operating temperature. This effectively prevents large temperature fluctuations due to inertia, thus ensuring user comfort. Compared to traditional step-like frequency regulation, the operating frequency change output by this invention is continuous and smooth, significantly reducing the start-stop shock and operating noise of the variable capacity compressor and extending the lifespan of its mechanical components.

[0105] In a specific example, the steps for introducing the PID algorithm described above include:

[0106] First, an error signal is generated, which is the temperature difference between the indoor ambient temperature and the set operating temperature. Here, the indoor ambient temperature is represented as T2, and the set operating temperature is represented as T3. The above error signal (i.e., the temperature difference value) is represented as... Then e(t) = T2 - T3;

[0107] Then, a proportional-integral-derivative (PID) controller needs to be established, and its control law expression is as follows:

[0108] ;

[0109] Where u(t) is the output signal of the PID controller (i.e., the output of the PID algorithm mentioned above), which is used to map the target frequency of the variable capacity compressor.

[0110] Kp is the proportional gain, which is used to determine the response sensitivity to temperature difference.

[0111] Ki is the integral gain, used to eliminate long-standing static temperature difference deviations;

[0112] Kd is the differential gain, used to predict the trend of temperature difference changes and suppress overshoot to achieve a smooth adjustment process.

[0113] Finally, the output signal u(t) of the PID controller is converted into the operating frequency of the variable displacement compressor through a linear or nonlinear mapping function:

[0114] f = fmin + (fmax - fmin)·Sigmoid[u(t)];

[0115] The Sigmoid function is a logistic function, and its expression is as follows:

[0116]

[0117] By using the above expression to impose upper and lower limits on the operating frequency of the variable displacement compressor (fmin ≤ f ≤ fmax), it can be ensured that the variable displacement compressor operates smoothly within a safe range.

[0118] Based on the above-mentioned scheme, this invention uses the temperature difference between the indoor ambient temperature and the set operating temperature, combined with an introduced PID algorithm, to control the system. This ensures that the indoor ambient temperature can be accurately stabilized near the set operating temperature, resolving the overcooling or overheating phenomena that may occur in traditional on / off control or simple frequency conversion control. Furthermore, it can predict the trend of temperature difference changes and reduce the operating frequency of the variable capacity compressor in advance when the indoor ambient temperature approaches the set operating temperature. This effectively prevents large temperature fluctuations due to inertia, thus ensuring user comfort. Compared to traditional step-like frequency regulation, the operating frequency change output by this invention is continuous and smooth, significantly reducing the start-stop shock and operating noise of the variable capacity compressor and extending the lifespan of its mechanical components.

[0119] Please see the appendix Figure 4 In one specific embodiment, the control method for the above-mentioned variable displacement compressor includes the following steps:

[0120] When the air conditioning system is running in cooling mode, detect the outdoor ambient temperature T1 and the indoor ambient temperature T2, obtain the set operating temperature T3, and calculate the temperature difference between the indoor ambient temperature and the set operating temperature ΔT=T2-T3.

[0121] Then, it is determined whether the outdoor ambient temperature T1 is greater than the first preset threshold temperature T01 within the preset threshold time. If not, it indicates that the air conditioning system is in a low load state. At this time, the variable capacity compressor is controlled to work in single cylinder mode, and the operating frequency of the variable capacity compressor is adjusted according to the magnitude and change of the temperature difference value combined with the PID algorithm.

[0122] If yes, it means that the air conditioning system is in a medium-high load state. Then, it is further determined whether the temperature difference is greater than the second preset threshold temperature T02. If no, it means that the air conditioning system is in a medium load state. At this time, the variable capacity compressor is controlled to work in bipolar mode. At the same time, the operating frequency of the variable capacity compressor is adjusted according to the size and change of the temperature difference and the PID algorithm.

[0123] If so, it indicates that the air conditioning system is under high load. At this time, the variable capacity compressor is controlled to work in dual-cylinder mode, and the operating frequency of the variable capacity compressor is adjusted according to the magnitude and change of the temperature difference and the PID algorithm.

[0124] Based on the above-described solution, the present invention can achieve the following beneficial effects:

[0125] 1. This invention provides a clear switching scheme for single-cylinder mode, dual-cylinder mode, and bipolar mode, which can balance the energy saving of single-cylinder mode, the high energy efficiency of bipolar mode, and the strong cooling capacity of dual-cylinder mode. It also achieves a smooth transition between single-cylinder mode, dual-cylinder mode, and bipolar mode under different temperature difference conditions, ensuring that the air conditioning system can maintain the best energy efficiency ratio and response speed under all operating conditions.

[0126] 2. This invention uses the temperature difference between the indoor ambient temperature and the set operating temperature, combined with an introduced PID algorithm, to control the system. This ensures that the indoor ambient temperature is accurately stabilized near the set operating temperature, resolving the overcooling or overheating issues that may occur in traditional on / off control or simple frequency conversion control. Furthermore, it allows for prediction of temperature difference trends, enabling the reduction of the variable capacity compressor's operating frequency in advance when the indoor ambient temperature approaches the set operating temperature. This effectively prevents significant temperature fluctuations due to inertia, thus ensuring user comfort. Compared to traditional step-like frequency regulation, this invention provides a continuous and smooth change in the output operating frequency, significantly reducing start-stop shock and operating noise of the variable capacity compressor, and extending the lifespan of its mechanical components.

[0127] Please see the appendix Figure 8 Based on the above-mentioned control method for variable capacity compressor, the present invention also proposes an air conditioning system, which has a variable capacity compressor 5, a gas-liquid separator 1 connected to the suction side of the variable capacity compressor, and a condenser connected to the discharge side of the variable capacity compressor 5, characterized in that the variable capacity compressor includes at least a first compression cylinder 51, a second compression cylinder 52, and a cooler 3.

[0128] The variable displacement compressor can operate in single-cylinder mode, double-cylinder mode, and two-stage mode. In single-cylinder mode, the first compression cylinder 51 works alone.

[0129] In dual-cylinder mode, the first compression cylinder 51 and the second compression cylinder 52 work in parallel;

[0130] In bipolar mode, the first compression cylinder 51 and the second compression cylinder 52 operate in series, and the cooler 3 is placed between the first compression cylinder 51 and the second compression cylinder 52 to cool the refrigerant discharged from the first compression cylinder 51 and transfer it to the second compression cylinder 52.

[0131] Please see the appendix Figure 5In single-cylinder mode, only the first compression cylinder 51 is engaged in operation. At this time, after the refrigerant is discharged from the gas-liquid separator 1, it enters the air inlet 511 of the first compression cylinder 51. After being compressed by the first compression cylinder 51, it is discharged from the air outlet 512. In this case, since only one compression cylinder is engaged in operation, the working energy consumption is low, which can achieve energy saving effect under low load conditions.

[0132] Please see the appendix Figure 6 In dual-cylinder mode, the first compression cylinder 51 and the second compression cylinder 52 work simultaneously and are connected in parallel. The two compression cylinders work at the same time, resulting in higher cooling efficiency and enabling rapid cooling under high load conditions.

[0133] Please see the appendix Figure 7 In bipolar mode, the first compression cylinder 51 and the second compression cylinder 52 work simultaneously and are connected in series. A cooler 3 is also provided between the first compression cylinder 51 and the second compression cylinder 52. The cooler 3 can perform intermediate cooling on the refrigerant discharged from the first compression cylinder 51, which can effectively reduce irreversible losses during the compression process, thereby improving the energy efficiency ratio of the air conditioning system and ensuring high energy efficiency under medium load conditions.

[0134] Based on the above-mentioned solution, this invention provides a variable capacity compressor 5 with single-cylinder mode, dual-cylinder mode, and bipolar mode. The control method of the variable capacity compressor 5 can switch between single-cylinder mode, dual-cylinder mode, and bipolar mode, which can balance the energy saving of single-cylinder mode, the high energy efficiency of bipolar mode, and the strong cooling capacity of dual-cylinder mode. It also achieves a smooth transition between single-cylinder mode, dual-cylinder mode, and bipolar mode under different temperature difference conditions, ensuring that the air conditioning system can maintain the best energy efficiency ratio and response speed under all operating conditions.

[0135] Please see the appendix Figure 8 The air conditioning system described in this invention also includes a first four-way valve 2 and a second four-way valve 4 connected to the first compression cylinder 51 and the second compression cylinder 52. The first four-way valve 2 and the second four-way valve 4 are used to adjust the refrigerant flow direction in the air conditioning system to switch the variable capacity compressor 5 to work in one of the following modes: single-cylinder mode, dual-cylinder mode, and bipolar mode.

[0136] Based on the above solution, the present invention simplifies the switching action of single-cylinder mode, dual-cylinder mode and bipolar mode to the control of the first four-way valve 2 and the second four-way valve 4, without the need for additional pipeline layout and flow path switching. The overall switching scheme is simpler and more efficient, and can meet the stable control requirements of the present invention for switching between single-cylinder mode, dual-cylinder mode and bipolar mode.

[0137] Specifically, in this invention, the gas-liquid separator 1 has a first outlet 11 and a second outlet 12. The first outlet 11 is connected to the air inlet 511 of the first compression cylinder 51, and the second outlet 12 is connected to the first port 21 of the first four-way valve 2.

[0138] The outlet 512 of the first compression cylinder 51 is connected to the third port 43 and the fourth port 44 of the second four-way valve 4. The first port 41 of the second four-way valve 4 is connected to the cooler 3. The second port 42 of the second four-way valve 4 and the outlet of the cooler 3 are connected together to the second port 22 of the first four-way valve 2.

[0139] The fourth port 24 of the first four-way valve 2 is connected to the air inlet 521 of the second compression cylinder 52, and the third port 23 of the first four-way valve 2 is connected to the condenser together with the air outlet 522 of the second compression cylinder 52.

[0140] Based on the above-mentioned scheme, this invention provides the connection relationship between the first compression cylinder 51 and the second compression cylinder 52 and the first four-way valve 2 and the second four-way valve 4 in the variable capacity compressor 5 of this invention. Based on this connection relationship, this invention can achieve the switching between single-cylinder mode, double-cylinder mode and bipolar mode by controlling only the first four-way valve 2 and the second four-way valve 4, making the overall switching scheme simpler and more efficient, and meeting the stable control requirements of this invention for switching between single-cylinder mode, double-cylinder mode and bipolar mode.

[0141] Please see the appendix Figure 9 When the variable capacity compressor 5 is operating in single-cylinder mode, the second port 22 of the first four-way valve 2 is connected to the third port 23, and the second port 42 of the second four-way valve 4 is connected to the fourth port 44.

[0142] At this time, after the refrigerant is discharged from the gas-liquid separator 1, it enters the air inlet 511 of the first compression cylinder 51. After being compressed by the first compression cylinder 51, it is discharged from the air outlet 512. Then it flows out through the fourth port 44 and the second port 42 of the second four-way valve 4, enters the second port 22 of the first four-way valve 2, and finally is discharged to the condenser through the third port 23 of the first four-way valve 2.

[0143] In other words, in single-cylinder mode, after the refrigerant is discharged from the first compression cylinder 51, it directly enters the next condenser through two four-way valves to complete the compression of the refrigerant. The second compression cylinder 52 does not work, which can achieve energy saving under low load.

[0144] Please see the appendix Figure 10 When the variable capacity compressor 5 is working in dual-cylinder mode, the first port 21 of the first four-way valve 2 is connected to the fourth port 24, the second port 22 is connected to the third port 23, and the second port 42 of the second four-way valve 4 is connected to the fourth port 44.

[0145] At this time, after the refrigerant is discharged from the gas-liquid separator 1, it directly enters the air inlet 511 of the first compression cylinder 51. After being compressed by the first compression cylinder 51, it is discharged from the air outlet 512. Then it flows out through the fourth port 44 and the second port 42 of the second four-way valve 4, enters the second port 22 of the first four-way valve 2, and finally is discharged to the condenser through the third port 23 of the first four-way valve 2.

[0146] The other path first passes through the first port 21 of the first four-way valve 2, and then enters the air inlet 521 of the second compression cylinder 52 through the fourth port 24 of the first four-way valve 2, and then is discharged to the condenser through the air outlet 522 of the second compression cylinder 52.

[0147] In other words, in dual-cylinder mode, after the refrigerant is discharged from the gas-liquid separator 1, it is divided into two paths and enters the first compression cylinder 51 and the second compression cylinder 52 respectively. The two compression cylinders work simultaneously to achieve rapid cooling under high load conditions.

[0148] Please see the appendix Figure 11 When the variable capacity compressor 5 is operating in bipolar mode, the second port 22 of the first four-way valve 2 is connected to the fourth port 24, and the first port 41 of the second four-way valve 4 is connected to the third port 43.

[0149] At this time, after the refrigerant is discharged from the gas-liquid separator 1, it enters the air inlet 511 of the first compression cylinder 51. After being compressed by the first compression cylinder 51, it is discharged from the air outlet 512. Then, it passes through the third port 43 of the second four-way valve 4 and is discharged from the first port 41. It then enters the cooler 3 for cooling. The refrigerant coming out of the cooler 3 passes through the second port 22 of the first four-way valve 2 and is discharged from the fourth port 24. It then enters the air inlet 521 of the second compression cylinder 52. After being compressed by the second compression cylinder 52, it is discharged from the air outlet 522 to the condenser.

[0150] In other words, in bipolar mode, after the refrigerant is discharged from the gas-liquid separator 1, it is compressed by the first compression cylinder 51 and then cooled by the cooler 3. After being cooled, the refrigerant enters the second compression cylinder 52 for compression. This mode combines intermediate cooling technology, which effectively reduces irreversible losses in the compression process and can improve the energy efficiency ratio of the air conditioning system.

[0151] Based on the above-mentioned scheme, this invention provides specific control logic for switching between single-cylinder mode, dual-cylinder mode, and bipolar mode through the first four-way valve 2 and the second four-way valve 4. Combined with the control method of the variable capacity compressor 5, the switching between single-cylinder mode, dual-cylinder mode, and bipolar mode can balance the energy saving of single-cylinder mode, the high energy efficiency of bipolar mode, and the strong cooling capacity of dual-cylinder mode. It also achieves a smooth transition between single-cylinder mode, dual-cylinder mode, and bipolar mode under different temperature difference conditions, ensuring that the air conditioning system can maintain the best energy efficiency ratio and response speed under all operating conditions.

[0152] In summary, this invention pertains to energy-saving hydraulic and pneumatic components, and compared with existing technologies, it has at least the following beneficial effects:

[0153] 1. This invention provides a clear switching scheme for single-cylinder mode, dual-cylinder mode, and bipolar mode, which can balance the energy saving of single-cylinder mode, the high energy efficiency of bipolar mode, and the strong cooling capacity of dual-cylinder mode. It also achieves a smooth transition between single-cylinder mode, dual-cylinder mode, and bipolar mode under different temperature difference conditions, ensuring that the air conditioning system can maintain the best energy efficiency ratio and response speed under all operating conditions.

[0154] 2. This invention uses the temperature difference between the indoor ambient temperature and the set operating temperature, combined with an introduced PID algorithm, to control the system. This ensures that the indoor ambient temperature is accurately stabilized near the set operating temperature, resolving the overcooling or overheating issues that may occur in traditional on / off control or simple frequency conversion control. Furthermore, it allows for prediction of temperature difference trends, enabling the reduction of the variable capacity compressor's operating frequency in advance when the indoor ambient temperature approaches the set operating temperature. This effectively prevents significant temperature fluctuations due to inertia, thus ensuring user comfort. Compared to traditional step-like frequency regulation, this invention provides a continuous and smooth change in the output operating frequency, significantly reducing start-stop shock and operating noise of the variable capacity compressor, and extending the lifespan of its mechanical components.

[0155] It should be noted that the terminology used above is for describing specific embodiments only and is not intended to limit the exemplary embodiments of the present invention. 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. The order of execution of actions, steps, etc., in the apparatus and methods in the specification and drawings can be implemented in any order unless a specific express order is specified, and as long as the output of a previous process is not used in a subsequent process. Similar sequential terms used for ease of description do not imply that such an order must be followed.

[0156] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, they 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 constraints. 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.

[0157] The above description is only 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.

Claims

1. A control method for a variable displacement compressor, wherein the variable displacement compressor has a single-cylinder mode, a dual-cylinder mode, and a bipolar mode, characterized in that, The control method includes: Detect the outdoor and indoor ambient temperatures where the air conditioning system is located; The system obtains the set operating temperature of the air conditioning system, determines whether the variable capacity compressor meets the switching conditions for single-cylinder mode based on the outdoor ambient temperature, and controls the variable capacity compressor to work in single-cylinder mode when the switching conditions for single-cylinder mode are met. When the variable capacity compressor does not meet the switching conditions for single-cylinder mode, the variable capacity compressor is switched to dual-cylinder mode or bipolar mode according to the indoor ambient temperature and the set operating temperature.

2. The control method for a variable displacement compressor according to claim 1, characterized in that, Determining whether the variable-capacity compressor meets the switching conditions for single-cylinder mode based on the outdoor ambient temperature includes: When the outdoor ambient temperature is greater than the first preset threshold temperature, the current operating state of the air conditioning system is maintained; After a preset threshold time, determine whether the outdoor ambient temperature is lower than the first preset threshold temperature; If so, the variable capacity compressor is determined to meet the switching conditions for single-cylinder mode; If not, it is determined that the variable capacity compressor does not meet the switching conditions for single-cylinder mode.

3. The control method for a variable displacement compressor according to claim 2, characterized in that, Switching the variable capacity compressor to operate in dual-cylinder mode or dual-stage mode based on the indoor ambient temperature and the set operating temperature includes: Calculate the temperature difference between the indoor ambient temperature and the set operating temperature; Determine whether the temperature difference value is greater than the second preset threshold temperature. If so, control the variable capacity compressor to work in dual-cylinder mode. If not, the variable capacity compressor is controlled to operate in bipolar mode.

4. The control method for a variable displacement compressor according to claim 1, characterized in that, The operating frequency of the variable capacity compressor is adjusted according to the temperature difference between the indoor ambient temperature and the set operating temperature, as well as a PID algorithm.

5. The control method for a variable displacement compressor according to claim 4, characterized in that, The output of the PID algorithm is: ; in, The temperature difference between the indoor ambient temperature and the set operating temperature. For proportional gain, For integral gain, This is the differential gain.

6. The control method for a variable displacement compressor according to claim 5, characterized in that, The calculation model for the operating frequency of the variable capacity compressor is: f = fmin + (fmax - fmin)·Sigmoid[u(t)]; Where f is the operating frequency of the variable capacity compressor, fmin is the lower limit of the operating frequency of the variable capacity compressor, fmax is the upper limit of the operating frequency of the variable capacity compressor, u(t) is the output of the PID algorithm, and Sigmoid is the logistic function.

7. An air conditioning system employing a control method for a variable-capacity compressor as described in any one of claims 1 to 6, comprising a variable-capacity compressor (5), a gas-liquid separator (1) connected to the suction side of the variable-capacity compressor, and a condenser connected to the discharge side of the variable-capacity compressor (5), characterized in that, The variable displacement compressor includes at least a first compression cylinder (51), a second compression cylinder (52), and a cooler (3); The variable displacement compressor can operate in single-cylinder mode, double-cylinder mode, and bipolar mode. In the single-cylinder mode, the first compression cylinder (51) operates alone. In the dual-cylinder mode, the first compression cylinder (51) and the second compression cylinder (52) work in parallel; In the bipolar mode, the first compression cylinder (51) and the second compression cylinder (52) operate in series, and the cooler (3) is placed between the first compression cylinder (51) and the second compression cylinder (52) to cool the refrigerant discharged from the first compression cylinder (51) and transfer it to the second compression cylinder (52).

8. The air conditioning system according to claim 7, characterized in that, The air conditioning system also includes a first four-way valve (2) and a second four-way valve (4) connected to the first compression cylinder (51) and the second compression cylinder (52). The first four-way valve (2) and the second four-way valve (4) are used to adjust the refrigerant flow direction in the air conditioning system to switch the variable capacity compressor (5) to work in one of the single-cylinder mode, the dual-cylinder mode and the bipolar mode.

9. The air conditioning system according to claim 8, characterized in that, The gas-liquid separator (1) has a first outlet (11) and a second outlet (12), the first outlet (11) being connected to the air inlet (511) of the first compression cylinder (51), and the second outlet (12) being connected to the first port (21) of the first four-way valve (2). The outlet (512) of the first compression cylinder (51) is connected to the third port (43) and the fourth port (44) of the second four-way valve (4). The first port (41) of the second four-way valve (4) is connected to the cooler (3). The second port (42) of the second four-way valve (4) and the outlet of the cooler (3) are connected together to the second port (22) of the first four-way valve (2). The fourth port (24) of the first four-way valve (2) is connected to the air inlet (521) of the second compression cylinder (52), and the third port (23) of the first four-way valve (2) is connected to the condenser together with the air outlet (522) of the second compression cylinder (52).

10. The air conditioning system according to claim 9, characterized in that, When the variable capacity compressor (5) is operating in single-cylinder mode, the second port (22) of the first four-way valve (2) is connected to the third port (23), and the second port (42) of the second four-way valve (4) is connected to the fourth port (44). When the variable capacity compressor (5) is operating in dual-cylinder mode, the first port (21) and the fourth port (24) of the first four-way valve (2) are connected, the second port (22) and the third port (23) are connected, and the second port (42) and the fourth port (44) of the second four-way valve (4) are connected. When the variable capacity compressor (5) is operating in bipolar mode, the second port (22) of the first four-way valve (2) is connected to the fourth port (24), and the first port (41) of the second four-way valve (4) is connected to the third port (43).

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