A control method of a three-heat-exchanger carbon dioxide heat pump system

Abstract

The application discloses a control method of a three-heat-exchanger carbon dioxide heat pump system, comprising the following steps: S1) acquiring temperature data and a preset table; S2) determining a working mode of the heat pump system according to the temperature data, wherein the working mode comprises a maximum heating mode, a heating dehumidification mode, a refrigeration dehumidification mode and a maximum refrigeration mode; S3) calculating a target air outlet temperature in an instantaneous state according to the target air outlet temperature, and dynamically adjusting the target air outlet temperature according to a control rule, the temperature data and the target air outlet temperature in the instantaneous state, wherein the control rule comprises a maximum heating mode control rule, a heating dehumidification mode control rule, a refrigeration dehumidification mode control rule and a maximum refrigeration mode control rule; and S4) using the dynamically adjusted target air outlet temperature for indoor temperature regulation.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicles, and specifically to a control method for a three-heat-exchanger carbon dioxide heat pump system. Background Technology

[0002] With increasingly stringent environmental protection regulations and stricter carbon emission requirements, new energy vehicles have experienced rapid development and widespread promotion. Since new energy vehicles lack an engine to provide additional heat, the heating energy for winter air conditioning relies solely on the battery's electrical energy, directly shortening the vehicle's driving range and highlighting range anxiety. Therefore, designing a more energy-efficient electric vehicle heating system is crucial for improving the driving range and overall driving experience. Currently, the mainstream heating solutions for electric vehicles are PTC (Positive Temperature Coefficient) heating and heat pump air conditioning technology. PTC (Power Transmission Control) converts electrical energy into heat energy through ceramic heating elements. This method cannot achieve 100% energy conversion efficiency, inevitably resulting in energy loss. Furthermore, the lower the ambient temperature, the lower the energy utilization efficiency, significantly reducing the driving range of electric vehicles in winter. Heat pump air conditioning technology, on the other hand, can extract low-grade heat energy from the ambient air, thus achieving higher energy efficiency. However, limited by the thermodynamic properties of R134a refrigerant, its heating capacity drops drastically below -10°C, rendering it unable to meet winter heating comfort requirements and necessitating PTC assistance. In contrast, carbon dioxide refrigerant exhibits excellent thermodynamic properties at low temperatures (below -20°C), and its supercritical region can achieve very high temperatures. Therefore, carbon dioxide heat pumps can meet the heating requirements in severe winter conditions, while achieving an energy efficiency ratio (EER) of over 2, significantly outperforming PTC systems in terms of energy consumption. A qualified carbon dioxide heat pump system needs to meet the following requirements: (1) meet the temperature regulation needs of the car cabin under all working conditions, including heating in the cold winter, cooling in the hot summer and dehumidifying in rainy and foggy weather; (2) when the external environment fluctuates drastically, it can switch between different modes in a timely and stable manner to ensure the stability of the in-vehicle environment and the comfort of the occupants; (3) under the premise of ensuring comfort and driving safety, the system's energy efficiency should be taken into account, and the most reasonable working mode should be selected to cope with the corresponding working conditions to maximize the vehicle's range.

[0003] Currently, most mature commercial heat pump systems use four-way valves or three-way valves to switch between different modes. The advantage is that the system is simple and the mode switching is fast. However, since the pressure in a carbon dioxide heat pump system can reach 14 MPa or even higher, the existing four-way valves and three-way valves cannot meet the requirements for airtightness, safety and reliability under such high pressure. Therefore, the existing four-way reversing heat pump system solutions and their control methods cannot be directly used for carbon dioxide heat pump systems, and there is no corresponding control method to meet the reliability, safety and comfort of in-vehicle temperature regulation. Summary of the Invention

[0004] To address the aforementioned issues, the purpose of this application is to provide a control method and a heat pump system for a three-heat exchanger carbon dioxide heat pump system that allows for rapid and stable switching between different modes depending on changes in the external environment and the set mode.

[0005] This application provides a control method for a three-heat-exchanger carbon dioxide heat pump system, including:

[0006] S1) Obtain temperature data and preset tables. The temperature data includes target air outlet temperature, vehicle interior temperature, target value of vehicle interior temperature, outside temperature and glass temperature. The preset tables include a maximum heating mode operation preset table, a maximum cooling mode operation preset table, a heating and dehumidification mode preset table, and a cooling and dehumidification mode preset table.

[0007] S2) Determine the operating mode of the heat pump system based on the temperature data. The operating mode includes maximum heating mode, heating and dehumidification mode, cooling and dehumidification mode and maximum cooling mode.

[0008] S3) Calculate the target outlet air temperature under instantaneous conditions based on the target outlet air temperature, and dynamically adjust the target outlet air temperature according to the control rules, the temperature data, and the target outlet air temperature under instantaneous conditions. The control rules include maximum heating mode control rules, heating and dehumidification mode control rules, cooling and dehumidification mode control rules, and maximum cooling mode control rules.

[0009] S4) The dynamically adjusted target air outlet temperature is used for vehicle interior temperature regulation.

[0010] Furthermore, the control method for the three-heat-exchanger carbon dioxide heat pump system, which determines the operating mode of the heat pump system based on the temperature data, further includes:

[0011] Set the maximum and minimum temperature points;

[0012] The maximum heating mode is used when the external temperature is lower than the minimum temperature point.

[0013] The maximum cooling mode is used when the external temperature is greater than the maximum temperature point.

[0014] The heating dehumidification mode is used when the outside temperature is between the maximum and minimum temperature points and the target air outlet temperature is greater than the outside temperature; otherwise, the cooling dehumidification mode is used.

[0015] Furthermore, in the control method of the three-heat-exchanger carbon dioxide heat pump system, the calculation expression for the target outlet air temperature under instantaneous conditions is as follows:

[0016] T transient =T steady +θ·ΔT;

[0017] Wherein, θ is the instantaneous compensation coefficient, which is obtained based on the vehicle interior temperature, the target value of the vehicle interior temperature, and the outside temperature;

[0018] ΔT is a preset value, which is determined based on the outside temperature and the inside temperature of the vehicle;

[0019] T steady The target outlet air temperature;

[0020] T transient The target outlet air temperature is defined as the instantaneous temperature.

[0021] Furthermore, in the control method of the aforementioned three-heat-exchanger carbon dioxide heat pump system, the calculation expression for the instantaneous compensation coefficient is as follows:

[0022]

[0023] Among them, T incar The temperature inside the vehicle;

[0024] T set The target value for the vehicle interior temperature;

[0025] T amb The external temperature is referred to as "the external temperature".

[0026] Furthermore, the control method for the three-heat-exchanger carbon dioxide heat pump system, wherein the three-heat-exchanger carbon dioxide heat pump system using the control method includes an expansion valve, a compressor, and an evaporator.

[0027] Furthermore, in the control method of the three-heat-exchanger carbon dioxide heat pump system, the maximum heating mode operation preset table includes the maximum target outlet air temperature and the minimum target outlet air temperature in the maximum heating mode, and the maximum heating mode control rules include:

[0028] When the target outlet air temperature is less than the minimum target outlet air temperature of the maximum heating mode, switch to the heating and dehumidification mode; otherwise, adjust the expansion valve and the compressor according to the preset table of the maximum heating mode and proceed to the next step.

[0029] When the target outlet air temperature is greater than the target outlet air temperature in the instantaneous state, switch to the heating and dehumidification mode; otherwise, maintain the current operating mode.

[0030] Furthermore, in the control method of the three-heat-exchanger carbon dioxide heat pump system, the maximum cooling mode operation preset table includes the maximum target outlet air temperature and the minimum target outlet air temperature in the maximum cooling mode, and the maximum cooling mode control rules include:

[0031] When the target outlet air temperature is greater than the maximum target outlet air temperature of the maximum cooling mode, switch to the cooling and dehumidification mode; otherwise, adjust the expansion valve and the compressor according to the maximum cooling mode preset table and proceed to the next step.

[0032] When the target outlet air temperature is lower than the target outlet air temperature under the instantaneous state, switch to the cooling and dehumidification mode; otherwise, maintain the current operating mode.

[0033] Furthermore, in the control method of the three-heat-exchanger carbon dioxide heat pump system, the preset table for the heating and dehumidification mode includes the maximum and minimum target outlet air temperatures for the heating and dehumidification mode, and the control rules for the heating and dehumidification mode include:

[0034] When the target air outlet temperature is greater than the maximum target air outlet temperature of the heating and dehumidification mode, switch to the maximum heating mode; when the target air outlet temperature is less than the minimum target air outlet temperature of the heating and dehumidification mode, switch to the cooling and dehumidification mode; otherwise, adjust the expansion valve and the compressor according to the preset table of the heating and dehumidification mode and proceed to the next step.

[0035] If the target outlet air temperature does not reach the target outlet air temperature under the instantaneous state and the target outlet air temperature is greater than the instantaneous target outlet air temperature correction value at the lowest speed of the compressor, then switch to the cooling and dehumidification mode; if the target outlet air temperature does not reach the target outlet air temperature under the instantaneous state and the target outlet air temperature is less than the instantaneous target outlet air temperature correction value at the highest speed of the compressor, then switch to the maximum heating mode; otherwise, maintain the current mode operation.

[0036] When the target outlet air temperature reaches the target outlet air temperature under the instantaneous state and the glass temperature is greater than the preset dew point temperature, adjust the expansion valve, the evaporator and the compressor; otherwise, maintain the current operating mode.

[0037] Furthermore, in the control method of the three-heat-exchanger carbon dioxide heat pump system, the preset table for the cooling and dehumidification mode includes the maximum and minimum target outlet air temperatures of the cooling and dehumidification mode, and the control rules for the cooling and dehumidification mode include:

[0038] When the target air outlet temperature is less than the minimum target air outlet temperature of the heating and dehumidification mode, switch to the maximum cooling mode; when the target air outlet temperature is greater than the maximum target air outlet temperature of the dehumidification mode, switch to the heating and dehumidification mode; otherwise, adjust the expansion valve and the compressor according to the preset table of the dehumidification mode and proceed to the next step.

[0039] If the target outlet air temperature does not reach the target outlet air temperature under the instantaneous state and the target outlet air temperature is less than the instantaneous target outlet air temperature correction value when the compressor is at its lowest speed, the system switches to the heating and dehumidification mode. If the target outlet air temperature does not reach the target outlet air temperature under the instantaneous state and the target outlet air temperature is greater than the instantaneous target outlet air temperature correction value when the compressor is at its highest speed, the system switches to the maximum cooling mode. Otherwise, the current mode is maintained.

[0040] When the target outlet air temperature reaches the target outlet air temperature under the instantaneous state and the glass temperature is greater than the preset dew point temperature, adjust the expansion valve, the evaporator and the compressor; otherwise, maintain the current operating mode.

[0041] Furthermore, in the control method of the aforementioned three-heat-exchanger carbon dioxide heat pump system, the expression for calculating the instantaneous target outlet air temperature correction value is as follows:

[0042] T correct = (1-α)·T steady +α·T transient ;

[0043] Among them, T correct This is the correction value for the instantaneous target outlet air temperature;

[0044] T steady The target outlet air temperature;

[0045] T transient The target outlet air temperature under the instantaneous state;

[0046] α is a correction ratio, 0≤α≤1, obtained based on the target values ​​of the external temperature and the interior temperature.

[0047] The technical solution provided in this application has the following advantages:

[0048] 1. Because the target air outlet temperature is used as the regulator, the interior temperature can be adjusted more accurately;

[0049] 2. Thanks to the use of preset meters, the vehicle can save more electricity during operation;

[0050] 3. Due to the adoption of control rules, the switching between different modes during system operation is smoother. Attached Figure Description

[0051] Figure 1 This is a flowchart of a preferred embodiment of the control method for a three-heat-exchanger carbon dioxide heat pump system of the present invention.

[0052] Figure 2 This is a preferred heat pump system mode switching control logic diagram according to an embodiment of the present invention;

[0053] Figure 3 This is a preferred maximum heating mode control rule logic control diagram for an embodiment of the present invention;

[0054] Figure 4 This is a preferred maximum cooling mode control rule logic control diagram according to an embodiment of the present invention;

[0055] Figure 5 This is a preferred control logic diagram for the heating and dehumidification mode control in an embodiment of the present invention.

[0056] Figure 6 This is a preferred control logic diagram for the cooling and dehumidification mode control in an embodiment of the present invention.

[0057] Figure 7 This is a specific application embodiment of the preferred control method for a three-heat-exchanger carbon dioxide heat pump system in the maximum heating mode of the three-heat-exchanger heat pump system according to an embodiment of the present invention.

[0058] Figure 8 This is a specific application embodiment of the control method of a preferred three-heat-exchange carbon dioxide heat pump system in the heating and dehumidification mode of a three-heat-exchange heat pump system according to an embodiment of the present invention.

[0059] Figure 9 This is a specific application embodiment of the preferred control method of a three-heat-exchanger carbon dioxide heat pump system in the refrigeration and dehumidification mode of a three-heat-exchanger heat pump system according to an embodiment of the present invention.

[0060] Figure 10 This is a specific application embodiment of the control method for a preferred three-heat-exchanger carbon dioxide heat pump system in the maximum cooling mode of the three-heat-exchanger heat pump system. Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The described embodiments are some embodiments of this application, but not all embodiments. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0062] Furthermore, it should be noted that, unless otherwise explicitly specified and limited, terms such as “installation,” “connection,” and “linkage” used in the description of this application should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; or it can be a connection within two components. Those skilled in the art can understand its specific meaning in this application according to the specific circumstances.

[0063] Figure 1 This is a flowchart illustrating the control method for a preferred embodiment of the three-heat-exchanger carbon dioxide heat pump system of the present invention. Figure 1 As shown, the control method for a three-heat-exchanger carbon dioxide heat pump system is characterized by comprising:

[0064] S1) Acquire temperature data and preset tables. Temperature data includes target air outlet temperature, vehicle interior temperature, target value of vehicle interior temperature, outside temperature and glass temperature. Preset tables include maximum heating mode operation preset table, maximum cooling mode operation preset table, heating and dehumidification mode preset table and cooling and dehumidification mode preset table.

[0065] S2) Determine the operating mode of the heat pump system based on temperature data. The operating modes include maximum heating mode, heating and dehumidification mode, cooling and dehumidification mode, and maximum cooling mode.

[0066] S3) Calculate the target outlet air temperature under instantaneous conditions based on the target outlet air temperature, and dynamically adjust the target outlet air temperature according to the control rules, temperature data and the target outlet air temperature under instantaneous conditions. The control rules include the maximum heating mode control rules, the heating and dehumidification mode control rules, the cooling and dehumidification mode control rules and the maximum cooling mode control rules.

[0067] S4) The dynamically adjusted target air outlet temperature is used for vehicle interior temperature regulation.

[0068] In this preferred embodiment, the target air outlet temperature can be calculated based on the heat exchange between the vehicle body and the external environment, the heat from solar thermal radiation, and the heat provided by the air conditioning system, using the blower airflow. This value is dynamically adjusted and changed based on temperature data and system operation.

[0069] Figure 2 This is a preferred embodiment of the heat pump system mode switching control logic diagram of the present invention. (See diagram below.) Figure 2 As shown, determining the operating mode of the heat pump system based on temperature data further includes:

[0070] Set the maximum and minimum temperature points;

[0071] The maximum heating mode is used when the outside temperature is lower than the minimum temperature point.

[0072] The maximum cooling mode is used when the outside temperature is higher than the maximum temperature point.

[0073] Use the heating dehumidification mode when the outside temperature is between the maximum and minimum temperatures and the target air outlet temperature is greater than the outside temperature; otherwise, use the cooling dehumidification mode.

[0074] Preferably, once the working mode is determined, the operating mode can be dynamically switched according to the control rules.

[0075] Preferably, the calculation expression for the target outlet air temperature under instantaneous conditions is as follows:

[0076] T transient =T steady +θ·ΔT;

[0077] Wherein, θ is the instantaneous compensation coefficient, which is obtained based on the vehicle interior temperature, the target value of the vehicle interior temperature, and the outside temperature;

[0078] ΔT is a preset value, which is determined based on the outside temperature and the inside temperature of the vehicle;

[0079] T steady Target air outlet temperature;

[0080] T transient The target outlet air temperature is the temperature at the instantaneous state.

[0081] Preferably, the expression for calculating the instantaneous compensation coefficient is:

[0082]

[0083] Among them, T incar The temperature inside the car;

[0084] T set This is the target value for the vehicle interior temperature.

[0085] T ambExternal temperature.

[0086] Preferably, the control method of the three-heat-exchanger carbon dioxide heat pump system of the present invention is applied to the three-heat-exchanger carbon dioxide heat pump system, which includes an expansion valve, a compressor, and an evaporator.

[0087] Figure 3 This is a preferred maximum heating mode control rule logic control diagram for an embodiment of the present invention. For example... Figure 3 As shown, the maximum heating mode operation preset table includes the maximum and minimum target outlet air temperatures for the maximum heating mode. The maximum heating mode control rules include:

[0088] When the target outlet air temperature is less than the minimum target outlet air temperature of the maximum heating mode, switch to heating and dehumidification mode; otherwise, adjust the expansion valve and compressor according to the preset table of the maximum heating mode and proceed to the next step.

[0089] When the target outlet air temperature is greater than the instantaneous target outlet air temperature, switch to heating and dehumidification mode; otherwise, maintain the current operating mode.

[0090] Figure 4 This is a preferred maximum cooling mode control rule logic control diagram according to an embodiment of the present invention. For example... Figure 4 As shown, the maximum cooling mode operation preset table includes the maximum and minimum target outlet air temperatures for the maximum cooling mode. The maximum cooling mode control rules include:

[0091] When the target outlet air temperature is greater than the maximum target outlet air temperature of the maximum cooling mode, switch to cooling and dehumidification mode; otherwise, adjust the expansion valve and compressor according to the maximum cooling mode preset table and proceed to the next step.

[0092] When the target outlet air temperature is lower than the instantaneous target outlet air temperature, switch to cooling and dehumidification mode; otherwise, maintain the current operating mode.

[0093] Figure 5 This is a logic control diagram of the preferred heating and dehumidification mode control rules in an embodiment of the present invention. For example... Figure 5 As shown, the preset table for heating and dehumidification modes includes the maximum and minimum target outlet air temperatures for the heating and dehumidification modes. The control rules for the heating and dehumidification modes include:

[0094] When the target air outlet temperature is greater than the maximum target air outlet temperature of the heating and dehumidification mode, switch to the maximum heating mode. When the target air outlet temperature is less than the minimum target air outlet temperature of the heating and dehumidification mode, switch to the cooling and dehumidification mode. Otherwise, adjust the expansion valve and compressor according to the preset table of the heating and dehumidification mode and proceed to the next step.

[0095] If the target outlet air temperature does not reach the instantaneous target outlet air temperature and the target outlet air temperature is greater than the instantaneous target outlet air temperature correction value when the compressor is at its lowest speed, the mode will switch to cooling and dehumidification. If the target outlet air temperature does not reach the instantaneous target outlet air temperature and the target outlet air temperature is less than the instantaneous target outlet air temperature correction value when the compressor is at its highest speed, the mode will switch to maximum heating. Otherwise, the current mode will be maintained.

[0096] When the target outlet air temperature reaches the instantaneous target outlet air temperature and the glass temperature is greater than the preset dew point temperature, adjust the expansion valve, evaporator and compressor; otherwise, maintain the current operating mode.

[0097] Figure 6 This is a logic control diagram of the preferred cooling and dehumidification mode control rules in an embodiment of the present invention. Figure 6 As shown, the preset table for cooling and dehumidifying modes includes the maximum and minimum target outlet air temperatures for the cooling and dehumidifying mode. The control rules for the cooling and dehumidifying mode include:

[0098] When the target air outlet temperature is less than the minimum target air outlet temperature of the heating and dehumidification mode, switch to the maximum cooling mode. When the target air outlet temperature is greater than the maximum target air outlet temperature of the dehumidification mode, switch to the heating and dehumidification mode. Otherwise, adjust the expansion valve and compressor according to the preset table of the dehumidification mode and proceed to the next step.

[0099] If the target air outlet temperature does not reach the instantaneous target air outlet temperature and the target air outlet temperature is less than the instantaneous target air outlet temperature correction value when the compressor is at its lowest speed, the mode will switch to heating and dehumidification. If the target air outlet temperature does not reach the instantaneous target air outlet temperature and the target air outlet temperature is greater than the instantaneous target air outlet temperature correction value when the compressor is at its highest speed, the mode will switch to maximum cooling. Otherwise, the current mode will be maintained.

[0100] When the target outlet air temperature reaches the instantaneous target outlet air temperature and the glass temperature is greater than the preset dew point temperature, adjust the expansion valve, evaporator and compressor; otherwise, maintain the current operating mode.

[0101] Preferably, the formula for calculating the instantaneous target outlet air temperature correction value is:

[0102] T correct = (1-α)·T steady +α·T transient ;

[0103] Among them, T correct This is the correction value for the instantaneous target outlet air temperature;

[0104] T steady Target air outlet temperature;

[0105] T transient The target outlet air temperature in the instantaneous state;

[0106] α is the correction ratio, 0≤α≤1, which is obtained based on the target values ​​of outside temperature and inside temperature.

[0107] In this embodiment, the preset dew point temperature is the preset temperature when there is a risk of fogging.

[0108] It is worth noting that the preset table includes adjustments for the target outlet air temperature, blower airflow, compressor speed, and expansion valve opening of the carbon dioxide heat pump system. By operating the carbon dioxide heat pump system according to the parameters in the preset table, the target outlet air temperature can be dynamically adjusted, while also saving energy. This allows for quick switching of operating modes and adjustment of the vehicle interior temperature based on the target outlet air temperature.

[0109] Figure 7 This is a specific application embodiment of the control method for a preferred three-heat-exchanger carbon dioxide heat pump system in the maximum heating mode of the three-heat-exchanger heat pump system. Figure 8 This is a specific application embodiment of the control method of a preferred three-heat-exchanger carbon dioxide heat pump system in the heating and dehumidification mode of a three-heat-exchanger heat pump system according to an embodiment of the present invention. Figure 9 This is a specific application embodiment of the control method of a preferred three-heat-exchanger carbon dioxide heat pump system in the refrigeration and dehumidification mode of a three-heat-exchanger heat pump system according to an embodiment of the present invention. Figure 10 This is a specific application embodiment of the preferred control method for a three-heat-exchanger carbon dioxide heat pump system in the maximum cooling mode of the three-heat-exchanger heat pump system according to an embodiment of the present invention. Combined with control rules and... Figures 7-10 As shown, the three-heat-exchange carbon dioxide heat pump system includes: a first internal heat exchanger 1A, a second internal air exchanger 1B, an interior heat exchanger 2, a compressor 3, a first expansion valve 4A, a second expansion valve 4B, a first shut-off valve 5A, a second shut-off valve 5B, a third shut-off valve 5C, a fourth shut-off valve 5D, a fifth shut-off valve 5E, and a temperature damper 6. The heat exchangers (1A, 1B, 2) are used to heat the air, defrost and defog, and regulate humidity. The expansion valves (4A, 4B) and shut-off valves (5A, 5B, 5C, 5D, 5E) work together in the automotive air conditioning system to ensure the flow of refrigerant between different components and to achieve temperature regulation through corresponding thermodynamic cycles. Accurate control of these valves helps improve the efficiency of the automotive air conditioning system and also ensures reliable operation of the system in different operating modes. The temperature damper 6 mainly regulates the temperature of the air entering the vehicle. It can be controlled by a motor or manually to change the ratio of cold and hot air in the ventilation system to achieve the desired comfortable temperature.

[0110] This embodiment utilizes the switching of valves (4A, 4B, 5A, 5B, 5C, 5D, 5E) and the adjustment of temperature damper 6 to switch between different modes. However, switching between certain modes requires shutting down compressor 3 to activate the valves. The forced start and stop of compressor 3 not only generates significant noise but also causes changes in outlet air temperature, both of which impact passenger cabin comfort, especially during transitional seasons when mode switching is more frequent and the impact is greater. Therefore, the system design should minimize the start and stop of compressor 3. This system, through the design and adjustment of valve positions, ensures that the compressor does not need to be shut down during mode switching except for maximum heating and heating / dehumidification modes, guaranteeing rapid, smooth, and comfortable mode switching. Furthermore, by introducing control logic, this system can largely avoid switching between maximum heating and heating / dehumidification modes under automatic air conditioning comfort control, thereby reducing the need for compressor shutdown. The control logic for mode switching in this system will be described in detail below.

[0111] To achieve air conditioning control, the target outlet air temperature needs to be obtained. According to the energy balance principle, when the temperature in the car's passenger compartment reaches a stable level, Q... h +Q c +Q r +Q hvac =0, where:

[0112] Q h : The amount of heat generated by the human body;

[0113] Q c Heat exchange between the vehicle body and the external environment;

[0114] Q r The heat emitted by solar thermal radiation;

[0115] Q hvac The heat provided by the air conditioning system.

[0116] Q h Q c and Q r All of these can be calculated using sensor values, from which Q under stable operating conditions can be obtained. hvac Based on the external temperature, internal temperature, and target set temperature, the blower airflow is set, and the airflow and Q can be used to determine the optimal airflow. hvac The target outlet air temperature T under steady-state operating conditions was calculated. steady To ensure the vehicle interior temperature reaches the preset target value more quickly, the difference between the current interior temperature and the preset value should be considered, and compensation should be applied to the target air outlet temperature. Define an instantaneous compensation coefficient. in:

[0117] Among them, T incar The temperature inside the car;

[0118] Tset This is the target value for the vehicle interior temperature.

[0119] T amb External temperature.

[0120] As the interior temperature gradually approaches the target value, the value of θ gradually decreases from 100% to 0%, thus obtaining the instantaneous target outlet air temperature T. transient =T steady +θ·ΔT, where ΔT is a preset value based on the target values ​​of the external and internal temperatures. The resulting stable target outlet air temperature T is... steady and instantaneous target outlet air temperature T transient This becomes an important basis for judging mode switching.

[0121] The decision of which mode to use is primarily based on the current outside temperature and the target outlet air temperature: when the ambient temperature is harsh and the heat exchange energy demand is high, the heat pump mode is directly defined as maximum heating or maximum cooling; while when the outside temperature is in a transitional season, the heating or cooling energy demand is not too high, and the mode is then determined based on the stable target outlet air temperature T. steady The system determines its mode based on the magnitude of the heat pump's operating environment and user preferences, defining either cooling / dehumidification or heating / dehumidification. Generally, the system's maximum cooling or heating mode has stronger capabilities, while the dehumidification / cooling or heating mode is more energy-efficient and also provides dehumidification. The heat pump mode is determined in real-time based on the vehicle's current operating environment and user preferences, adapting to changes in external factors. The specific switching logic and methods between each mode will be explained below.

[0122] When the outside temperature is low, the heating demand is high while the absolute humidity in the air is low. Therefore, the preset mode is set to maximum heating mode: shut-off valves 5A, 5C, and 5E are open; shut-off valves 5B and 5D are closed; the first expansion valve 4A is fully closed; the second expansion valve 4B is throttled; and the temperature damper is fully open. To achieve rapid and accurate temperature regulation, a preset operating table was obtained beforehand through a ring model experiment, as shown in Table 1 below:

[0123] Table 1. Preset Table for Maximum Heating Mode Operation

[0124]

[0125] When the air conditioning system is in operation, first check the stable target outlet air temperature T based on the outside temperature. steadyCheck if the temperature exceeds the lower limit of the preset table. If it is lower than the minimum outlet air temperature in the preset table, switch to heating and dehumidification mode. The switching method is to first turn off compressor 3, then open the first expansion valve 4A and the fourth shut-off valve 5D, close the third shut-off valve 5C and the fifth shut-off valve 5E, and then turn on compressor 3 again. The entire process should not exceed 15 seconds. At the same time, the blower air volume is appropriately reduced to ensure the outlet air temperature, thus minimizing the impact on passenger cabin comfort. Otherwise, obtain the opening degree of expansion valve 2 and the preset value of compressor speed from the table by looking up the outside temperature and the stable target outlet air temperature, and operate the system with these parameters. Subsequently, use the instantaneous target outlet air temperature T... transient To achieve the target air outlet temperature, the compressor speed of unit 3 is adjusted. If the air outlet temperature is still higher than the instantaneous target air outlet temperature when the compressor speed of unit 3 drops to the minimum speed, it indicates that the heating capacity of the air conditioning system exceeds the demand. In this case, the mode needs to be switched to heating and dehumidification mode. Since the required air outlet temperature in the passenger compartment should normally be above 35°C under low outside temperatures, which can be achieved in the maximum heating mode, there is generally no need to switch from the maximum heating mode to the heating and dehumidification mode under automatic air conditioning comfort control. This switch is mainly for low air outlet temperature requests that may occur when passengers manually adjust the settings. If there is a risk of fogging on the windows in the maximum heating mode, the solution is to increase the opening of the defrost damper, which does not involve switching the heat pump mode.

[0126] When the outside temperature exceeds a certain value, the cooling demand is high. The preset mode is set to maximum cooling mode, with shut-off valves 5B and 5D open, shut-off valves 5A, 5C, and 5E closed, the first expansion valve 4A fully closed, the second expansion valve 4B throttled, and the temperature damper 6 fully closed. A preset operating table, similar to the preset table for the maximum heating mode mentioned earlier, is obtained through prior experiments. During air conditioning system operation, the stable target outlet air temperature T is first checked based on the outside temperature. steady Check if the temperature exceeds the upper limit of the preset table. If it exceeds the highest outlet air temperature in the preset table, switch to cooling / dehumidification mode. The switching method is to keep the compressor 3 speed at its lowest, first open the first shut-off valve 5A, fully open the first expansion valve 4A, and then close the second shut-off valve 5B. Otherwise, based on the outside temperature and the stable target outlet air temperature, obtain the opening degree of the second expansion valve 4B and the preset value of the compressor 3 speed from the table, and operate the system with these parameters. Subsequently, use the instantaneous target outlet air temperature T... transient To achieve the target outlet air temperature, the compressor speed is adjusted. If the outlet air temperature is still lower than the instantaneous target outlet air temperature when the compressor speed drops to the lowest speed, it indicates that the cooling capacity of the air conditioning system exceeds the demand. In this case, the mode needs to be switched to cooling and dehumidification mode.

[0127] When the outside temperature is in transitional seasonal conditions, the system's heating and cooling demands are not high, and the focus of regulation is on comfort and energy saving. Therefore, how to quickly regulate temperature and humidity is the key to the air conditioning control system under these conditions. Humidity regulation is mainly achieved by adjusting the opening of the first expansion valve 4A and the second expansion valve 4B to change the refrigerant temperature on the low-pressure side, thereby changing the air temperature after the evaporator, controlling the outlet air temperature and humidity, and achieving optimal efficiency. Temperature regulation can be achieved by changing the compressor speed 3 and the opening of the temperature damper 6.

[0128] When T steady > At ambient temperature, the preset mode is set to heating and dehumidification mode. In this mode, shut-off valves 5A and 5D are open, shut-off valves 5B, 5C, and 5E are closed, the first expansion valve 4A is throttled, the second expansion valve 4B is fully open, and the temperature damper 6 is fully open. In heating and dehumidification mode, priority is given to achieving the desired heating effect; dehumidification effect is only considered when there is a risk of fogging, i.e., when the glass temperature measured by the sensor is close to or below the dew point temperature. In heating and dehumidification mode, first check the stable target outlet air temperature T based on the ambient temperature. steady Check if the temperature exceeds the upper or lower limit of the preset table. If it exceeds the highest outlet air temperature in the preset table, the mode will switch to maximum heating mode. The switching method is to first turn off the compressor, then open the third shut-off valve 5C and the fifth shut-off valve 5E, close the first expansion valve 4A and the fourth shut-off valve 5D, and then turn on the compressor again. The entire process takes no more than 15 seconds. At the same time, the blower air volume is appropriately reduced to ensure the outlet air temperature, thus minimizing the impact on passenger cabin comfort. Since the heating and dehumidification mode can still provide a high outlet air temperature when the outside temperature is not very low, the outlet air temperature can fully meet the comfort requirements. Therefore, under automatic air conditioning comfort control, the switching from heating and dehumidification to maximum heating mode is rare. This switching mainly occurs in situations such as passengers manually adjusting the air temperature and requesting a high outlet air temperature. If the temperature is lower than the lowest outlet air temperature in the preset table, the mode will switch to cooling and dehumidification mode. The switching method is to fully open the first expansion valve 4A and throttle the second expansion valve 4B. If the stable target outlet air temperature is within the preset table range, the opening degree of expansion valve 1 and the preset value of compressor speed are obtained by looking up the table based on the outside temperature and the target outlet air temperature, and the system is operated with these parameters. Subsequently, the instantaneous target outlet air temperature T transient To achieve the target outlet air temperature, the compressor speed is adjusted. If the compressor speed is reduced to its lowest setting, and the outlet air temperature is still higher than the instantaneous target outlet air temperature correction value T, then... correct That is, the outlet air temperature T > (1-α)·T steady +α·T transientIf the mode switches to cooling / dehumidification mode, it will switch to cooling mode; otherwise, it will remain in the current mode. Here, α is a correction ratio defined based on the outside temperature and the target inside temperature (0 ≤ α ≤ 1), which needs to be calibrated through real-vehicle road tests. Decreasing α will reduce the frequency of mode switching, but the rate at which the interior temperature reaches the target temperature may be slower. If the compressor reaches its maximum speed, and the outlet air temperature is still lower than the instantaneous target outlet air temperature correction value T, then... correct That is, the outlet air temperature T < (1-α)·T steady +α·T transient (α is defined as before, 0≤α≤1), then the switching mode is the maximum heating mode; otherwise, the current mode is maintained. When the outlet air temperature reaches the target temperature, the window glass temperature is monitored. When the glass temperature is < dew point temperature + M℃, there is a risk of fogging. In this case, the opening of the first expansion valve 4A needs to be adjusted to lower the temperature after the evaporator to the glass temperature - N℃, and then the compressor speed 3 is adjusted to bring the outlet air temperature back to the target outlet air temperature. Here, M is the dew point temperature correction amount obtained through experimental calibration, and N is the condensing temperature offset set to achieve the dehumidification effect. Simultaneously, to prevent evaporator frosting, the evaporator surface temperature must not be lower than 0℃.

[0129] When T steady When the outside temperature is below a certain threshold, the preset mode is set to cooling and dehumidification mode. In this mode, shut-off valves 5A and 5D are open, shut-off valves 5B, 5C, and 5E are closed, the first expansion valve 4A is fully open, the second expansion valve 4B is throttled, and the temperature damper 6 is initially fully closed, with adjustable opening. In cooling and dehumidification mode, priority is given to whether the cooling effect meets the requirements; dehumidification effect is only considered when there is a risk of fogging, i.e., when the glass temperature measured by the sensor is close to or below the dew point temperature. Simultaneously, to prevent evaporator frosting, the temperature after the evaporator must not be lower than 0℃. In cooling and dehumidification mode, first check the stable target outlet air temperature T based on the outside temperature. steady Check if the temperature exceeds the upper or lower limit of the preset table. If it exceeds the highest outlet temperature in the preset table, switch to heating and dehumidification mode. The switching method is to fully open the second expansion valve 4B and throttle the first expansion valve 4A. If it exceeds the lowest outlet temperature in the preset table, switch to maximum cooling mode. The switching method is to adjust the compressor 3 speed to the lowest, first open the second shut-off valve 5B, and then close the first shut-off valve 5A and the first expansion valve 4A. If the stable target outlet temperature is within the preset table range, first determine the opening degree of the second expansion valve 4B and the preset value of the compressor 3 speed by referring to the table based on the outside temperature and the target outlet temperature, and run the system with these parameters. Then, use the instantaneous target outlet temperature T... transientTo achieve the target outlet air temperature, the compressor speed is adjusted. If the outlet air temperature is still lower than the target outlet air temperature when the compressor speed is reduced to the lowest speed, the temperature damper 6 is gradually opened to mix the heat from the internal air cooler and increase the outlet air temperature. If the outlet air temperature is still lower than the target outlet air temperature when the temperature damper 6 is fully open, i.e., the outlet air temperature T < (1-α)·T steady +α·T transient (α is defined as before, 0≤α≤1), then the switching mode is heating and dehumidification mode. If the compressor speed reaches its maximum speed and the outlet air temperature is still higher than the target outlet air temperature, i.e., outlet air temperature T>(1-α)·T steady +α·T transient (α is defined as before, 0≤α≤1), then the switching mode is the maximum cooling mode. When the outlet air temperature reaches the target temperature, monitor the window glass temperature. When the glass temperature < dew point temperature + M℃, a risk of fogging is identified. At this point, it is necessary to adjust the opening of expansion valve 2 to lower the temperature after the evaporator to the glass temperature - N℃, and then adjust the compressor speed to bring the outlet air temperature up to the instantaneous target outlet air temperature T. transient If the outlet air temperature is still lower than the target temperature when the compressor 3 is reduced to the lowest speed, the temperature damper will be gradually opened to adjust the airflow until the target outlet air temperature is reached.

[0130] The control method and carbon dioxide heat pump system of the three heat exchanger of the present invention have multiple working modes such as maximum heating, cooling and dehumidification, heating and dehumidification and maximum cooling. It can seamlessly switch between multiple modes, which can not only cover the comfort needs of the whole temperature range, but also quickly and smoothly switch between different modes according to changes in the external environment and the set mode.

[0131] Those skilled in the art will understand that information, signals, and data can be represented using any of a variety of different techniques and arts. For example, the data, instructions, commands, information, signals, bits, symbols, and chips described throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or optical particles, or any combination thereof.

[0132] Those skilled in the art will further appreciate that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this hardware-software interchangeability, the various illustrative components, blocks, modules, circuits, and steps are described above in a generalized manner in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art may implement the described functionality in different ways for each specific application, but such implementation decisions should not be construed as departing from the scope of this application.

[0133] The various illustrative logic modules and circuits described in conjunction with the embodiments disclosed herein may be implemented or performed using a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general-purpose processor may be a microprocessor, but in alternatives, it may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors cooperating with a DSP core, or any other such configuration.

[0134] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of both. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor such that the processor can read and write information to / from the storage medium. In an alternative, the storage medium may be integrated into the processor. The processor and storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In an alternative, the processor and storage medium may reside as discrete components in the user terminal.

[0135] In one or more exemplary embodiments, the described functionality may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software as a computer program product, the functionality may be stored or transmitted as one or more instructions or code on or through a computer-readable medium. A computer-readable medium includes both computer storage media and communication media, encompassing any medium that facilitates the transfer of a computer program from one location to another. A storage medium may be any available medium accessible to a computer. By way of example and not limitation, such a computer-readable medium may include RAM, ROM, EEPROM, CD-ROM or other optical disc storage, disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and is accessible to a computer. Any connection is also legitimately referred to as a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of a medium. As used in this article, disk and disc include compact discs (CDs), laser discs, optical discs, digital multi-purpose discs (DVDs), floppy disks, and Blu-ray discs. Disks typically reproduce data magnetically, while discs reproduce data optically using lasers. Combinations of these should also be included within the scope of computer-readable media.

[0136] The above embodiments are provided for those skilled in the art to implement or use this application. Those skilled in the art can make various modifications or changes to the above embodiments without departing from the spirit of this application. Therefore, the scope of protection of this application is not limited to the above embodiments, but should be the maximum scope that conforms to the innovative features mentioned in the claims.

Claims

1. A control method for a three-heat-exchanger carbon dioxide heat pump system, characterized in that, include: S1) Obtain temperature data and preset tables. The temperature data includes target air outlet temperature, vehicle interior temperature, target value of vehicle interior temperature, outside temperature and glass temperature. The preset tables include a maximum heating mode operation preset table, a maximum cooling mode operation preset table, a heating and dehumidification mode preset table, and a cooling and dehumidification mode preset table. S2) Determine the operating mode of the heat pump system based on the temperature data. The operating mode includes maximum heating mode, heating and dehumidification mode, cooling and dehumidification mode, and maximum cooling mode. S3) Calculate the target outlet air temperature under instantaneous conditions based on the target outlet air temperature, and dynamically adjust the target outlet air temperature according to the control rules, the temperature data, and the target outlet air temperature under instantaneous conditions. The control rules include the maximum heating mode control rules, the heating and dehumidification mode control rules, the cooling and dehumidification mode control rules, and the maximum cooling mode control rules. S4) The dynamically adjusted target air outlet temperature is used for vehicle interior temperature regulation; Determining the operating mode of the heat pump system based on the temperature data further includes: Set the maximum and minimum temperature points; The maximum heating mode is used when the external temperature is lower than the minimum temperature point. The maximum cooling mode is used when the external temperature is greater than the maximum temperature point. The heating dehumidification mode is used when the outside temperature is between the maximum and minimum temperature points and the target air outlet temperature is greater than the outside temperature; otherwise, the cooling dehumidification mode is used. The calculation expression for the target outlet air temperature under the instantaneous state is as follows: ； in, The instantaneous compensation coefficient is obtained based on the vehicle interior temperature, the target value of the vehicle interior temperature, and the outside temperature. The preset value is determined based on the outside temperature and the inside temperature of the vehicle; The target outlet air temperature; The target outlet air temperature under the instantaneous state; The expression for calculating the instantaneous compensation coefficient is as follows: ； in, T incar The temperature inside the vehicle; T set The target value for the vehicle interior temperature; T amb The external temperature is referred to as "the external temperature".

2. The control method for the three-heat-exchanger carbon dioxide heat pump system according to claim 1, characterized in that, The three-heat-exchanger carbon dioxide heat pump system using this control method includes an expansion valve, a compressor, and an evaporator.

3. The control method for the three-heat-exchanger carbon dioxide heat pump system according to claim 2, characterized in that, The maximum heating mode operation preset table includes the maximum target outlet air temperature and the minimum target outlet air temperature under the maximum heating mode. The maximum heating mode control rules include: When the target outlet air temperature is less than the minimum target outlet air temperature of the maximum heating mode, switch to the heating and dehumidification mode; otherwise, adjust the expansion valve and the compressor according to the preset table of the maximum heating mode and proceed to the next step. When the target outlet air temperature is greater than the target outlet air temperature in the instantaneous state, switch to the heating and dehumidification mode; otherwise, maintain the current operating mode.

4. The control method for the three-heat-exchanger carbon dioxide heat pump system according to claim 2, characterized in that, The maximum cooling mode operation preset table includes the maximum target outlet air temperature and the minimum target outlet air temperature under the maximum cooling mode. The maximum cooling mode control rules include: When the target outlet air temperature is greater than the maximum target outlet air temperature of the maximum cooling mode, switch to the cooling and dehumidification mode; otherwise, adjust the expansion valve and the compressor according to the maximum cooling mode preset table and proceed to the next step. When the target outlet air temperature is lower than the target outlet air temperature under the instantaneous state, switch to the cooling and dehumidification mode; otherwise, maintain the current operating mode.

5. The control method for the three-heat-exchanger carbon dioxide heat pump system according to claim 2, characterized in that, The preset table for heating and dehumidifying modes includes the maximum and minimum target outlet air temperatures for the heating and dehumidifying modes. The control rules for the heating and dehumidifying modes include: When the target air outlet temperature is greater than the maximum target air outlet temperature of the heating and dehumidification mode, switch to the maximum heating mode; when the target air outlet temperature is less than the minimum target air outlet temperature of the heating and dehumidification mode, switch to the cooling and dehumidification mode; otherwise, adjust the expansion valve and the compressor according to the preset table of the heating and dehumidification mode and proceed to the next step. If the target outlet air temperature does not reach the target outlet air temperature under the instantaneous state and the target outlet air temperature is greater than the instantaneous target outlet air temperature correction value at the lowest speed of the compressor, then switch to the cooling and dehumidification mode; if the target outlet air temperature does not reach the target outlet air temperature under the instantaneous state and the target outlet air temperature is less than the instantaneous target outlet air temperature correction value at the highest speed of the compressor, then switch to the maximum heating mode; otherwise, maintain the current mode operation. When the target outlet air temperature reaches the target outlet air temperature under the instantaneous state and the glass temperature is greater than the preset dew point temperature, adjust the expansion valve, the evaporator and the compressor; otherwise, maintain the current operating mode.

6. The control method for the three-heat-exchanger carbon dioxide heat pump system according to claim 2, characterized in that, The preset table for cooling and dehumidifying modes includes the maximum and minimum target outlet air temperatures for the cooling and dehumidifying mode. The control rules for the cooling and dehumidifying mode include: When the target air outlet temperature is less than the minimum target air outlet temperature of the heating and dehumidification mode, switch to the maximum cooling mode; when the target air outlet temperature is greater than the maximum target air outlet temperature of the cooling and dehumidification mode, switch to the heating and dehumidification mode; otherwise, adjust the expansion valve and the compressor according to the preset table of the cooling and dehumidification mode and proceed to the next step. If the target outlet air temperature does not reach the target outlet air temperature under the instantaneous state and the target outlet air temperature is less than the instantaneous target outlet air temperature correction value when the compressor is at its lowest speed, the system switches to the heating and dehumidification mode. If the target outlet air temperature does not reach the target outlet air temperature under the instantaneous state and the target outlet air temperature is greater than the instantaneous target outlet air temperature correction value when the compressor is at its highest speed, the system switches to the maximum cooling mode. Otherwise, the current mode is maintained. When the target outlet air temperature reaches the target outlet air temperature under the instantaneous state and the glass temperature is greater than the preset dew point temperature, adjust the expansion valve, the evaporator and the compressor; otherwise, maintain the current operating mode.

7. The control method for a three-heat-exchanger carbon dioxide heat pump system according to any one of claims 5 or 6, characterized in that, The formula for calculating the instantaneous target outlet air temperature correction value is as follows: T correct =(1-α) +α ； in, T correct This is the correction value for the instantaneous target outlet air temperature; The target outlet air temperature; The target outlet air temperature under the instantaneous state; α is a correction ratio, 0≤α≤1, obtained based on the target values ​​of the external temperature and the interior temperature.

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