Vehicle transcritical CO2 refrigeration system temperature gradient optimization control device and method
By using a temperature gradient optimization control method to adjust the opening of the electronic expansion valve in real time, the problem of parameter drift in the CO2 transcritical refrigeration cycle was solved, and the maximum cooling capacity control of the system under dynamic operating conditions was realized, thereby improving the system reliability and energy efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-29
- Publication Date
- 2026-03-27
AI Technical Summary
Existing technologies cannot adapt to parameter drift in real time during CO2 transcritical refrigeration cycles, resulting in decreased control accuracy. Furthermore, the reliance on high-precision pressure sensors increases hardware costs and makes them prone to failure under high temperature and high pressure environments.
By employing a temperature sensor and an electronic expansion valve driver, and using a temperature gradient optimization control method, the opening of the electronic expansion valve is adjusted in real time. Combined with a low-pass filter and gradient calculation module, adaptive optimization control is achieved, avoiding the use of high-precision pressure sensors.
It improves the engineering reliability and energy efficiency ratio of the refrigeration system, ensures that the system operates at maximum cooling capacity under dynamic conditions, reduces system costs, and avoids control failures caused by sensor drift.
Smart Images
Figure CN121739655A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of optimization control of refrigeration systems, and particularly relates to a temperature gradient optimization control device and method for a transcritical CO2 refrigeration system for vehicles. BACKGROUND
[0002] In a transcritical CO2 refrigeration cycle, there is an optimal high-pressure side pressure point that makes the system refrigeration capacity maximum, i.e., an optimal working point. The optimal working point is dynamically affected by various factors such as ambient temperature, system charge, and component aging degree. Therefore, by adjusting the opening degree of the electronic expansion valve in real time, the system can always be maintained at the optimal working point, which is the key to improving the system energy efficiency.
[0003] The prior art mostly uses a "look-up table method" or "empirical formula" to set the target opening degree of the electronic expansion valve. However, this open-loop control method cannot adapt to parameter drift in actual operation, resulting in a decrease in control accuracy over time. Although some technologies introduce high-precision pressure sensors for closed-loop feedback, they significantly increase the hardware cost, and the sensors are prone to accuracy zero drift in high-temperature and high-pressure environments.
[0004] Therefore, there is an urgent need for a control method that can accurately lock and adaptively optimize the maximum refrigeration capacity working point of the system under variable working conditions without relying on high-precision sensors and complex theoretical models. SUMMARY
[0005] An object of the present application is to provide a temperature gradient optimization control device for a transcritical CO2 refrigeration system for vehicles, which can control the opening degree of the electronic expansion valve based on temperature signals, thereby avoiding the control failure problem caused by "zero drift" of the pressure sensor in high-temperature and high-pressure environments, and improving the engineering reliability of the refrigeration system.
[0006] Another object of the present application is to provide a self-adaptive optimization control method for a transcritical CO2 refrigeration system for vehicles based on temperature gradient, which can dynamically track the minimum point of the inlet temperature of the electronic expansion valve, so that the refrigeration system can adaptively lock the optimal working point under the current working condition, and ensure that the system always operates in the maximum refrigeration capacity state.
[0007] The technical solution provided by the present application is as follows: A temperature gradient optimization control device for a transcritical CO2 refrigeration system for vehicles, comprising: a temperature sensor arranged at the inlet of an electronic expansion valve of a transcritical CO2 refrigeration system for vehicles, for collecting the temperature at the inlet of the electronic expansion valve; an electronic expansion valve driver for driving the electronic expansion valve; A controller is electrically connected with the temperature sensor and the electronic expansion valve driver respectively; the controller determines the working state of the transcritical CO2 refrigeration system according to the signal of the temperature sensor, and controls the electronic expansion valve driver to adjust the opening of the electronic expansion valve according to the working state.
[0008] A temperature gradient optimization control method of a transcritical CO2 refrigeration system for vehicles, using the transcritical CO2 refrigeration system temperature gradient optimization control device for vehicles, comprising the following steps: Step one, according to the sampling period, the temperature sensor real-time acquisition electronic expansion valve inlet temperature; Step two, the electronic expansion valve inlet temperature is filtered to obtain the filtered electronic expansion valve inlet temperature; Step three, according to the filtered electronic expansion valve inlet temperature, the temperature gradient of the current time is calculated ; ; Among them, represents the current time, is the filtered electronic expansion valve inlet temperature at the current time, is the filtered electronic expansion valve inlet temperature at the last time, represents the adjustment step of the electronic expansion valve opening; Step four, according to the temperature gradient of the current time determine the working condition area of the current refrigeration system; with the electronic expansion valve inlet temperature keeping at the minimum point of the electronic expansion valve inlet temperature as the optimization target, according to the working condition area of the current refrigeration system, the opening of the electronic expansion valve at the next time is controlled.
[0009] Preferably, in the step two, the formula used in the filtering process is: ; Among them, is the filtered electronic expansion valve inlet temperature at the current time, is the filter smoothing coefficient, is the filtered electronic expansion valve inlet temperature at the last time, is the electronic expansion valve inlet temperature collected by the temperature sensor at the current time.
[0010] Preferably, in the step four, the method of controlling the opening of the electronic expansion valve at the next time includes: If , it is judged that the current refrigeration system is in the temperature drop area; the opening of the electronic expansion valve at the next time is controlled as: ; in, This represents the opening degree of the electronic expansion valve at the next moment. This represents the current opening degree of the electronic expansion valve. This indicates the adjustment step size of the electronic expansion valve opening.
[0011] Preferably, in step four, the method for controlling the opening degree of the electronic expansion valve at the next moment further includes: if ,and Then, determine the current optimal operating point of the refrigeration system; control the opening degree of the electronic expansion valve at the next moment as follows: or ; in, This represents the temperature gradient from the previous moment. This represents the opening degree of the electronic expansion valve at the next moment. This represents the current opening degree of the electronic expansion valve. This indicates the adjustment step size of the electronic expansion valve opening.
[0012] Preferably, in step four, the method for controlling the opening degree of the electronic expansion valve at the next moment further includes: if and Then, determine the current temperature rise zone of the refrigeration system; control the opening degree of the electronic expansion valve at the next moment as follows: ; in, This represents the temperature gradient from the previous moment. This represents the opening degree of the electronic expansion valve at the next moment. This represents the current opening degree of the electronic expansion valve. This indicates the adjustment step size of the electronic expansion valve opening.
[0013] Preferably, step four further includes: Generate the opening value of the electronic expansion valve at the next moment. Then, make a judgment Does it exceed the physical allowable range of the electronic expansion valve opening? ; if Then set ; Then set ; in, , These represent the minimum and maximum opening degrees of the electronic expansion valve, respectively.
[0014] Preferably, the adjustment step size of the electronic expansion valve opening is set as follows: ; in, This is the opening adjustment coefficient. ; These represent the maximum opening degree of the electronic expansion valve.
[0015] The beneficial effects of this invention are: (1) The adaptive optimization control method for automotive transcritical CO2 refrigeration system based on temperature gradient provided by the present invention effectively eliminates the gradient calculation deviation caused by high frequency noise by combining low-pass filtering preprocessing with temperature gradient trend judgment. It solves the problem of "gradient misjudgment" and repeated valve oscillation caused by noise in traditional extreme value search algorithm, and ensures the smoothness and stability of the control process.
[0016] (2) The adaptive optimization control method for automotive transcritical CO2 refrigeration system based on temperature gradient provided by the present invention abandons the dependence on static empirical formulas and theoretical models, and can dynamically track the minimum point of the inlet temperature of the electronic expansion valve. No matter how the ambient temperature fluctuates, or the system performance drifts due to component aging, it can automatically lock the optimal operating point under the current operating conditions, thereby ensuring that the system always operates at the maximum cooling capacity and effectively improving the energy efficiency ratio.
[0017] (3) The adaptive optimization control device for automotive transcritical CO2 refrigeration system based on temperature gradient provided by the present invention controls based on temperature signal, without the need to install expensive and easily damaged high-precision high-pressure pressure sensor; it not only directly reduces the material cost of the system, but also fundamentally avoids the control failure problem caused by "zero drift" of pressure sensor under high temperature and high pressure environment, and improves the engineering reliability of the system. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the transcritical CO2 refrigeration system for vehicles described in this invention.
[0019] Figure 2 This is the framework of the temperature gradient optimization control device for the transcritical CO2 refrigeration system for vehicles described in this invention.
[0020] Figure 3 This is a flowchart of the temperature gradient optimization control method for a transcritical CO2 refrigeration system for vehicles according to the present invention.
[0021] Figure 4 This is a comparison graph showing the trend of cooling capacity with the opening degree of the electronic expansion valve under different ambient temperatures and the characteristic curves of the electronic expansion valve inlet temperature with the opening degree of the electronic expansion valve.
[0022] Figure 5This is a comparison graph showing the trend of cooling capacity with electronic expansion valve opening at different compressor speeds and the characteristic curves of electronic expansion valve inlet temperature with electronic expansion valve opening. Detailed Implementation
[0023] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.
[0024] This invention provides a temperature gradient optimization control device and method for a transcritical CO2 refrigeration system in vehicles. For example... Figure 1 As shown, the automotive transcritical CO2 refrigeration system includes: an electric compressor 101, a gas cooler 102, an electronic expansion valve 103, an evaporator 104, and an integrated regenerator gas-liquid separator 120. The integrated regenerator gas-liquid separator 120 includes a first regenerator 121 and a second regenerator 122. The integrated regenerator gas-liquid separator 120 is provided with a first port, a second port, a third port, and a fourth port; wherein, the first regenerator 121 is disposed between the first port and the second port, and the second regenerator 122 is disposed between the third port and the fourth port.
[0025] The discharge end of the electric compressor 101 is connected to the inlet end of the gas cooler 102, the first port is connected to the outlet end of the gas cooler 102; the second port is connected to the inlet end of the electronic expansion valve 103, the outlet end of the electronic expansion valve 103 is connected to the inlet end of the evaporator 104; the third port is connected to the outlet end of the evaporator 104, and the fourth port is connected to the suction port of the electric compressor 101.
[0026] The temperature gradient optimization control device for a transcritical CO2 refrigeration system for vehicles provided by this invention includes: a temperature sensor, an electronic expansion valve driver, a controller, and a memory.
[0027] like Figure 1 As shown, a temperature sensor 111 is disposed between the second port of the integrated regenerator gas-liquid separator 120 and the inlet end of the electronic expansion valve 103, and is positioned close to the inlet end of the electronic expansion valve 103, for detecting the inlet temperature of the electronic expansion valve 103. The electronic expansion valve driver is used to drive the electronic expansion valve. The controller is electrically connected to both the temperature sensor and the electronic expansion valve driver; the controller can determine the operating state of the automotive transcritical CO2 refrigeration system based on the signal from the temperature sensor, and control the electronic expansion valve driver to adjust the opening degree of the electronic expansion valve based on the operating state. The memory is used to store computer programs and historical state data.
[0028] like Figure 2As shown, the temperature gradient optimization control device for the automotive transcritical CO2 refrigeration system, through closed-loop feedback logic, can achieve precise adaptive adjustment of the electronic expansion valve opening without the need for a pressure sensor. The control logic of the temperature gradient optimization control device for the automotive transcritical CO2 refrigeration system specifically includes: (1) Physical architecture and signal flow: As a controlled entity, the high-pressure side operating pressure of the transcritical CO2 refrigeration system directly affects the system's cooling capacity and energy efficiency ratio.
[0029] (2) Temperature sensor 111 is installed at the inlet of electronic expansion valve 103 to monitor the working fluid temperature in real time and convert it into a raw temperature signal output.
[0030] (3) The controller, as the core computing unit, is responsible for receiving the raw temperature signal and generating control commands through internal algorithm logic.
[0031] (4) The electronic expansion valve 103 acts as an actuator, receiving the opening command from the controller and performing the action to change the operating state of the transcritical CO2 refrigeration system, thereby forming a closed loop.
[0032] The controller includes a low-pass filtering module, a gradient calculation module, and an extreme value optimization decision module.
[0033] The low-pass filter module receives the raw temperature signal of the electronic expansion valve inlet from the temperature sensor and filters it to obtain the filtered electronic expansion valve inlet temperature. Due to compressor vibration and fluid pulsation in the transcritical CO2 refrigeration system, the raw temperature signal typically contains high-frequency noise. The low-pass filter module uses a low-pass filtering algorithm to remove noise and outputs a smooth characteristic temperature signal, providing an accurate data basis for subsequent gradient calculations.
[0034] The gradient calculation module receives the filtered inlet temperature signal of the electronic expansion valve and, combined with the current valve opening change, calculates the gradient trend of temperature change with opening degree. Then, by comparing the temperature difference in adjacent adjustment cycles, it identifies the current operating state of the refrigeration system: whether the refrigeration system is currently in the "cooling capacity rising zone" or the "cooling capacity falling zone (overshoot zone)".
[0035] The extreme value optimization decision module receives temperature gradient and current operating status information of the refrigeration system, outputs electronic expansion valve opening control command, and controls the opening of electronic expansion valve through electronic expansion valve driver.
[0036] The specific functions of the extreme value optimization decision module include: initial setting, which sets the initial opening of the electronic expansion valve for optimization; direction determination, which determines whether to increase or decrease the opening of the sub-expansion valve based on the trend fed back by the gradient calculation module; and locking and callback, which means that when it is determined that the refrigeration system has crossed the temperature minimum point (i.e. the maximum cooling capacity point), the extreme value optimization decision module issues a reverse callback command to control the opening of the electronic expansion valve to return to the optimal point and lock it in real time.
[0037] The temperature gradient optimization control device for a transcritical CO2 refrigeration system in vehicles provided by this invention collects temperature information from the transcritical CO2 refrigeration system using a temperature sensor, generating a noisy raw temperature signal. The controller uses an internal low-pass filter module to denoise the system, a gradient calculation module to analyze trends, and an extreme value optimization decision module to issue commands. Finally, the electronic expansion valve performs the opening adjustment. This modular design ensures that the system can bypass the dependence on expensive pressure sensors and achieve adaptive optimization of the maximum cooling capacity under all operating conditions through pure temperature feedback and noise reduction algorithms.
[0038] This invention also provides a method for optimizing the temperature gradient control of a transcritical CO2 refrigeration system for vehicles, such as... Figure 3 As shown, the specific implementation process of the temperature gradient optimization control method for the transcritical CO2 refrigeration system for vehicles is as follows.
[0039] 1. System initialization phase (1) Check whether the system meets the steady-state operating conditions; (2) Set the initial opening of the electronic expansion valve Electronic expansion valve opening adjustment step Filtering smoothing coefficient and the gradient of the previous time step Initialize to 0.
[0040] When setting the adjustment step size for the electronic expansion valve opening, if the adjustment step size is too small, the electronic expansion valve typically has mechanical hysteresis. Extremely small changes in opening may result in too small a change in flow rate, leading to a small temperature change that is less than the sensor's measurement error. In this case, the calculated gradient will be entirely noise, and the algorithm will fail.
[0041] If the opening step of the electronic expansion valve is too large, it will cause a drastic change in refrigerant flow, resulting in a sudden surge in high pressure or a sudden drop in suction pressure. This will cause severe oscillations in the system and may even trigger high and low pressure alarms and shutdowns.
[0042] Therefore, setting the adjustment step size of the electronic expansion valve opening is the foundation of the optimization control algorithm. Only by setting the adjustment step size of the electronic expansion valve opening appropriately can the stable operation of the refrigeration system be guaranteed. As a preferred option, the opening adjustment step size is set. ;in, This is the opening adjustment coefficient. ; These represent the maximum opening degree of the electronic expansion valve. That is, the opening degree adjustment step is... It is 1% to 5% of the full opening of the electronic expansion valve.
[0043] 2. Signal Acquisition and Denoising Stage (1) The temperature sensor collects the raw temperature signal at the inlet of the electronic expansion valve in real time. And output to the controller; (2) To address high-frequency interference and jitter in the original signal, the low-pass filter module in the controller filters the received original temperature signal. The filtering process is performed, and the filtering formula is as follows: ; in, Indicates the current moment. This represents the current filtered inlet temperature of the electronic expansion valve. This is the filtering smoothing coefficient, and its value range is... ; This represents the filtered inlet temperature of the electronic expansion valve from the previous moment. This is the inlet temperature of the electronic expansion valve collected by the temperature sensor at the current moment.
[0044] 3. Gradient Calculation The current temperature gradient is obtained by calculating the difference between the smoothed temperature value at the current moment and the previous moment, and dividing it by the step size. This temperature gradient reflects the mapping relationship between the change in the opening degree of the electronic expansion valve and the change in the inlet temperature of the electronic expansion valve. The formula for calculating the temperature gradient is: ; in, Indicates the current moment. This represents the current filtered inlet temperature of the electronic expansion valve. This represents the filtered inlet temperature of the electronic expansion valve from the previous moment. This indicates the adjustment step size of the electronic expansion valve opening.
[0045] 4. Based on the current temperature gradient Using symbols and their historical states, a three-way branching decision is made. In a transcritical CO2 refrigeration cycle, the discharge pressure is an independent variable not limited by the saturation temperature, and the opening degree of the electronic expansion valve directly determines the system's discharge pressure. The characteristic curve refers to the steady-state response curve under specific operating conditions (ambient temperature, set compressor speed, etc.), with the opening degree of the electronic expansion valve as the independent variable and the inlet temperature of the electronic expansion valve as the dependent variable.
[0046] (1) If the current temperature gradient The system is determined to be in the temperature decrease region on the left side of the characteristic curve, indicating that the current refrigeration system is in a state where increasing the opening degree still leads to a temperature decrease (i.e., the cooling capacity is still increasing). At this time, the first branch decision is executed: increase the opening degree of the electronic expansion valve, controlling the opening degree of the electronic expansion valve at the next moment as follows: .
[0047] Update system status: Log Then, proceed to the next sampling cycle.
[0048] (2) If the current temperature gradient Then, the gradient state from the previous time step is retrieved. Perform backtracking judgment; like and The system has just crossed the minimum point of its characteristic curve, meaning it has just experienced a gradient reversal from negative to positive, i.e., crossed the temperature minimum point. At this point, the current position is determined to be the optimal operating point. Execute the second branch decision, perform a hold or lock operation, and control the opening degree of the electronic expansion valve at the next moment as follows: or Perform fine-tuning and locking; Update system status: Log Then, proceed to the next sampling cycle.
[0049] (3) If the current gradient and The system is determined to be in the temperature rise region on the right side of the characteristic curve, indicating that it has deviated from the optimal point (overshoot region). At this point, the third branch strategy is executed: the opening of the electronic expansion valve is reduced to perform a callback, controlling the opening of the electronic expansion valve at the next moment as follows: ; Update system status: Log Then, it enters the next sampling cycle, thus forming a closed-loop control loop.
[0050] In each branch strategy, the opening control instruction is generated. Then, make a judgment Does it exceed the physical allowable range of the electronic expansion valve? ; like Then force setting ; Then force setting .
[0051] After executing the above opening adjustment command, the controller enters the update state: update step size. And store the current gradient value. This allows for a periodic comparison. Finally, the system enters a waiting state to await the next sampling period, continuously cycling to adapt to changes in external operating conditions.
[0052] To further demonstrate the physical basis of the optimization control method described in this invention, this embodiment provides a characteristic analysis based on experimental data.
[0053] like Figure 4 and Figure 5 As shown, in a transcritical CO2 refrigeration cycle, the left vertical axis represents the system cooling capacity (kW), and the right vertical axis represents the inlet temperature of the electronic expansion valve (°C). Experimental data clearly demonstrate that: As the opening of the electronic expansion valve changes, the cooling capacity curve shows a trend of first rising and then falling, with a clear maximum cooling capacity point; at the same time, the inlet temperature curve of the electronic expansion valve shows a trend of first falling and then rising, with a clear temperature minimum point.
[0054] The most crucial physical characteristic is that the opening degree of the electronic expansion valve corresponding to the maximum cooling capacity is essentially the same as the opening degree of the electronic expansion valve corresponding to the minimum inlet temperature. This principle proves that by finding and locking the minimum point of the electronic expansion valve inlet temperature, optimal control of the system's maximum cooling capacity can be achieved effectively.
[0055] In addition, in comparison Figure 4 Different ambient temperatures (40℃ and 45℃) and Figure 5 The curves at different compressor speeds (6000 rpm and 7000 rpm) show that the optimal operating point (extreme point) shifts significantly with changes in operating conditions. This demonstrates the necessity of using optimization control to dynamically track the extreme point.
[0056] Combination Figure 4 and Figure 5 The curve characteristics reveal that the gradient of the electronic expansion valve inlet temperature is relatively gentle near the minimum point. In practical engineering applications, high-frequency noise from the sensor can easily drown out the true gradient change, leading to misjudgment of the gradient direction by the controller or frequent oscillations of the electronic expansion valve. Therefore, this invention introduces a first-order weighted recursive filtering algorithm to improve the signal-to-noise ratio and incorporates reasonable logic to limit the opening adjustment step size, overcoming the mechanical hysteresis of the electronic expansion valve and ensuring that the temperature change is sufficient to be detected by the sensor. This ensures that the system can accurately and stably lock near the extreme operating point under complex and dynamic operating conditions.
[0057] The adaptive optimization control method for automotive transcritical CO2 refrigeration systems based on temperature gradients provided by this invention abandons the reliance on static empirical formulas and theoretical models, and can dynamically track the minimum point of the electronic expansion valve inlet temperature. Regardless of the fluctuation of ambient temperature or the performance drift of the system due to component aging, it can automatically lock the optimal operating point under the current operating conditions, thereby ensuring that the system always operates at the maximum cooling capacity and effectively improving the energy efficiency ratio.
[0058] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.
Claims
1. A temperature gradient optimization control device for a transcritical CO2 refrigeration system for vehicles, characterized in that, include: A temperature sensor is installed at the inlet of the electronic expansion valve in the automotive transcritical CO2 refrigeration system to collect the temperature at the inlet of the electronic expansion valve. An electronic expansion valve actuator for driving the electronic expansion valve; The controller is electrically connected to the temperature sensor and the electronic expansion valve driver, respectively. The controller determines the operating state of the automotive transcritical CO2 refrigeration system based on the signal from the temperature sensor, and controls the electronic expansion valve driver to adjust the opening of the electronic expansion valve based on the operating state.
2. A method for optimizing the temperature gradient control of a transcritical CO2 refrigeration system for vehicles, using the temperature gradient optimization control device for a transcritical CO2 refrigeration system for vehicles as described in claim 1, characterized in that... Includes the following steps: Step 1: Collect the inlet temperature of the electronic expansion valve in real time using a temperature sensor according to the sampling cycle; Step 2: Filter the inlet temperature of the electronic expansion valve to obtain the filtered inlet temperature of the electronic expansion valve; Step 3: Calculate the temperature gradient at the current moment based on the filtered inlet temperature of the electronic expansion valve. ; ； in, Indicates the current moment. This represents the current filtered inlet temperature of the electronic expansion valve. This represents the filtered inlet temperature of the electronic expansion valve from the previous moment. Indicates the adjustment step size of the electronic expansion valve opening; Step 4: Based on the current temperature gradient Determine the current operating condition zone of the refrigeration system; with the optimization objective of keeping the inlet temperature of the electronic expansion valve at its minimum value, control the opening degree of the electronic expansion valve at the next moment based on the current operating condition zone of the refrigeration system.
3. The temperature gradient optimization control method for a transcritical CO2 refrigeration system for vehicles according to claim 2, characterized in that, In step two, the formula used for filtering is: ； in, This represents the current filtered inlet temperature of the electronic expansion valve. The filtering smoothing coefficient is... This represents the filtered inlet temperature of the electronic expansion valve from the previous moment. This is the inlet temperature of the electronic expansion valve collected by the temperature sensor at the current moment.
4. The temperature gradient optimization control method for a transcritical CO2 refrigeration system for vehicles according to claim 2 or 3, characterized in that, In step four, the method for controlling the opening degree of the electronic expansion valve at the next moment includes: if If so, it is determined that the current refrigeration system is in the temperature drop zone; the opening degree of the electronic expansion valve at the next moment is controlled as follows: ； in, This represents the opening degree of the electronic expansion valve at the next moment. This represents the current opening degree of the electronic expansion valve. This indicates the adjustment step size of the electronic expansion valve opening.
5. The temperature gradient optimization control method for a transcritical CO2 refrigeration system for vehicles according to claim 4, characterized in that, In step four, the method for controlling the opening degree of the electronic expansion valve at the next moment further includes: if ,and Then, determine the current optimal operating point of the refrigeration system; control the opening degree of the electronic expansion valve at the next moment as follows: or ; in, This represents the temperature gradient from the previous moment. This represents the opening degree of the electronic expansion valve at the next moment. This represents the current opening degree of the electronic expansion valve. This indicates the adjustment step size of the electronic expansion valve opening.
6. The temperature gradient optimization control method for a transcritical CO2 refrigeration system for vehicles according to claim 5, characterized in that, In step four, the method for controlling the opening degree of the electronic expansion valve at the next moment further includes: if and Then, determine the current temperature rise zone of the refrigeration system; control the opening degree of the electronic expansion valve at the next moment as follows: ； in, This represents the temperature gradient from the previous moment. This represents the opening degree of the electronic expansion valve at the next moment. This represents the current opening degree of the electronic expansion valve. This indicates the adjustment step size of the electronic expansion valve opening.
7. The temperature gradient optimization control method for a transcritical CO2 refrigeration system for vehicles according to claim 6, characterized in that, Step four also includes: Generate the opening value of the electronic expansion valve at the next moment. Then, make a judgment Does it exceed the physical allowable range of the electronic expansion valve opening? ; if Then set ; Then set ; in, , These represent the minimum and maximum opening degrees of the electronic expansion valve, respectively.
8. The temperature gradient optimization control method for a transcritical CO2 refrigeration system for vehicles according to claim 7, characterized in that, The adjustment step size of the electronic expansion valve opening is set as follows: ； in, This is the opening adjustment coefficient. ; These represent the maximum opening degree of the electronic expansion valve.