A control method and system of a transcritical carbon dioxide heat pump air conditioning system

Abstract

The application belongs to the technical field of transcritical carbon dioxide system, and discloses a control method and system of a transcritical carbon dioxide heat pump air conditioning system; in the control method, an ESC controller is used as a bottom controller, an optimal starting value is input, optimization is carried out, and an optimal value of a control variable of the transcritical carbon dioxide heat pump air conditioning system is output; an MPC controller is used as an upper controller, is connected with the ESC controller, and synchronously calculates the optimal value of the control variable, and outputs a calculation result; wherein, when the transcritical carbon dioxide heat pump air conditioning system starts, the calculation result output by the MPC controller is used as the optimal starting value of the ESC controller; when a running condition of the transcritical carbon dioxide heat pump air conditioning system mutates, the calculation result output by the MPC controller is used to update the optimal starting value of the ESC controller. The application can realize fast and accurate optimal control of the system under complex running conditions.

Description

Technical Field

[0001] This invention belongs to the technical field of transcritical carbon dioxide systems, and specifically relates to a control method and system for a transcritical carbon dioxide heat pump air conditioning system. Background Technology

[0002] With the increasing prominence of environmental issues, traditional CFCs and HFCs refrigerants are facing gradual phase-out globally due to their high GWP (Global Warming Potential). CO2, as a pure natural refrigerant, has become one of the most ideal alternative refrigerants due to its high energy efficiency, environmental friendliness, and safety.

[0003] Currently, transcritical CO2 heat pump air conditioning systems are widely used in residential heat pump water heaters, electric vehicle thermal management, and some industrial applications. However, as the application scenarios of transcritical CO2 heat pump air conditioning become increasingly complex, traditional control methods are no longer sufficient. Specifically, for automotive transcritical CO2 heat pump air conditioning and thermal management systems, the control method must simultaneously meet the requirements of battery temperature control, passenger compartment temperature control, and motor electronic control temperature control. Existing traditional control schemes cannot achieve precise and optimized control, leading to battery energy waste.

[0004] In summary, given the increasingly complex and diverse working environments and operating conditions, there is an urgent need for a new control scheme for transcritical carbon dioxide heat pump air conditioning systems to achieve rapid and accurate system optimization control, thereby ensuring the efficient operation of transcritical CO2 heat pump air conditioning systems. Summary of the Invention

[0005] The purpose of this invention is to provide a control method and system for a transcritical carbon dioxide heat pump air conditioning system to solve one or more of the aforementioned technical problems. Specifically, the technical solution provided by this invention is a two-layer control scheme for a transcritical CO2 heat pump air conditioning system that combines model predictive control (MPC) and extreme value search control (ESC). This scheme can improve the optimization results of either ESC or MPC alone, enabling rapid and accurate optimal system control under complex operating conditions and ensuring the efficient operation of the transcritical CO2 heat pump air conditioning system.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a control method for a transcritical carbon dioxide heat pump air conditioning system, comprising:

[0008] Using the ESC controller as the underlying controller, the system inputs the initial optimization value, performs optimization, and outputs the optimal value of the control variables of the transcritical carbon dioxide heat pump air conditioning system. The optimal value output by the ESC controller is used to assign the execution structure of the transcritical carbon dioxide heat pump air conditioning system to control the system operation.

[0009] The MPC controller is used as the upper-level controller, connected to the ESC controller, and synchronously calculates the optimal value of the control variable, and outputs the calculation result;

[0010] Specifically, when the transcritical carbon dioxide heat pump air conditioning system is started, the calculation result output by the MPC controller is used as the optimization starting value of the ESC controller; when the operating conditions of the transcritical carbon dioxide heat pump air conditioning system change abruptly, the calculation result output by the MPC controller is used to update the optimization starting value of the ESC controller.

[0011] A further improvement to the method of the present invention is that,

[0012] The input to the ESC controller is the measured total energy consumption or the calculated cooling and heating energy efficiency ratio;

[0013] The output of the ESC controller is the current control variable.

[0014] A further improvement to the method of the present invention is that,

[0015] The ESC controller is either a single-output, single-channel ESC controller or a multi-output, multi-channel ESC controller.

[0016] A further improvement to the method of the present invention is that,

[0017] The output of the single-output, single-channel ESC controller is the optimal exhaust pressure;

[0018] The output of the multi-output multi-channel ESC controller includes multiple parameters such as optimal exhaust pressure, compressor speed, evaporator fan speed, and water pump speed.

[0019] A further improvement to the method of the present invention is that,

[0020] The inputs to the MPC controller are system state variables and system disturbances;

[0021] The output of the MPC controller is the same in type and quantity as the output of the ESC controller.

[0022] A further improvement to the method of the present invention is that,

[0023] The system state variables are one of the following combinations: refrigerant discharge pressure, outlet temperature of the secondary fluid on the gas cooler side, compressor outlet discharge pressure and temperature, gas cooler outlet pressure and temperature, pressure and temperature after the throttle valve, compressor inlet suction pressure and temperature, and inlet and outlet temperatures of the secondary fluid on the evaporator and gas cooler side.

[0024] The system interference is the weather temperature over a future period and the inlet temperature of the secondary fluid on the gas cooler side.

[0025] A further improvement to the method of the present invention is that,

[0026] When the transcritical carbon dioxide heat pump air conditioning system is running continuously and stably, the calculation results output by the MPC controller are not input into the ESC controller, and the ESC controller runs independently according to its own optimization logic.

[0027] A further improvement to the method of the present invention is that,

[0028] Based on the comparison between the relative error between the current output of the ESC controller and the current output of the MPC controller and the preset error threshold, it is determined whether the transcritical carbon dioxide heat pump air conditioning system is operating continuously and stably or experiencing a sudden change in operating conditions.

[0029] A further improvement to the method of the present invention is that,

[0030] The expression for calculating the relative error is as follows:

[0031]

[0032] In the formula, ε is the relative error; u mpc This is the current output of the MPC controller; u esc This is the current output of the ESC controller.

[0033] The present invention provides a control system for a transcritical carbon dioxide heat pump air conditioning system, comprising:

[0034] The ESC controller is used as a low-level controller, taking in the initial optimization value, performing optimization, and outputting the optimal value of the control variables of the transcritical carbon dioxide heat pump air conditioning system; wherein, the optimal value output by the ESC controller is used to assign the execution structure of the transcritical carbon dioxide heat pump air conditioning system to control the operation of the system.

[0035] The MPC controller is used as an upper-level controller to connect with the ESC controller, synchronously calculate the optimal values ​​of the control variables, and output the calculation results.

[0036] Specifically, when the transcritical carbon dioxide heat pump air conditioning system is started, the calculation result output by the MPC controller is used as the optimization starting value of the ESC controller; when the operating conditions of the transcritical carbon dioxide heat pump air conditioning system change abruptly, the calculation result output by the MPC controller is used to update the optimization starting value of the ESC controller.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] In view of the control challenges of existing transcritical CO2 heat pump air conditioning systems in complex application scenarios, this invention proposes a two-layer control method for transcritical CO2 heat pump air conditioning systems that combines MPC and ESC. By fully utilizing the respective control characteristics of ESC and MPC and combining their advantages to construct a two-layer control logic of ESC and MPC, the invention achieves fast, accurate and optimal control of the transcritical CO2 heat pump air conditioning system in complex and ever-changing application scenarios. This ensures the efficient operation of the transcritical CO2 heat pump air conditioning system, improves system operating efficiency, and saves energy. To further explain, the effectiveness of the ESC control method alone heavily depends on the initial value for optimization. An inappropriate initial value will cause the optimization process to be slow, and it will be unable to respond in real time and track the true optimal value of the system under rapidly changing operating conditions, thus failing to achieve optimal system control. MPC control heavily depends on the accuracy of the system model. Due to the high nonlinearity of the transcritical CO2 heat pump air conditioning system, the established control model can generally approximate but cannot accurately describe the system behavior. Therefore, even when the system is operating stably, the calculated optimal value is still not the exact optimal value, but a quasi-optimal value near the optimal value. The technical solution provided by this invention can improve the optimization results of ESC or MPC alone, and achieve fast and accurate optimal system control under complex operating conditions. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art are briefly introduced below; obviously, the drawings described below are some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0040] Figure 1 This is a schematic flowchart of a control method for a transcritical carbon dioxide heat pump air conditioning system provided in an embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the optimal intermediate pressure control method for a transcritical CO2 heat pump water heater in an embodiment of the present invention;

[0042] In the diagram, 1. Compressor; 2. Gas cooler; 3. Electronic expansion valve; 4. Evaporator; 5. Gas-liquid separator; 6. Water pump; 7. Fan; 8. ESC controller; 9. MPC controller; 10. First PI controller; 11. Second PI controller; 12. System total power consumption calculator; 13. Pressure sensor; 14. First temperature sensor; 15. Second temperature sensor. Detailed Implementation

[0043] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0044] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0045] The present invention will now be described in further detail with reference to the accompanying drawings:

[0046] Please see Figure 1 This invention provides a control method for a transcritical carbon dioxide heat pump air conditioning system, specifically a two-layer control method combining MPC and ESC. The ESC, as the bottom-level controller of the transcritical CO2 heat pump air conditioning system, is responsible for finding the precise optimal values ​​of the system control variables. These precise optimal values ​​are directly assigned to the system's execution structure to control system operation. The MPC, as the upper-level controller, is connected to the ESC controller and synchronously calculates the optimal values ​​of the system control variables in real time. The calculation results are only used as the starting value of the ESC controller's optimization module when the system starts up, or to update the starting value of the ESC controller's optimization module when the system's operating conditions change abruptly. During continuous and stable system operation, the optimal values ​​calculated by the MPC are not assigned to the ESC controller; in this case, the ESC controller operates independently according to its own optimization logic.

[0047] In a further preferred embodiment of the present invention, the ESC controller includes a standard ESC based on a sinusoidal signal, and also includes an ESC based on other modulated / demodulated signals; the ESC controller can be a single-output, single-channel ESC controller, or a multi-output, multi-channel ESC controller. The input to the ESC is generally the total energy consumption W obtained by real-time measurement of the system. total Alternatively, the COP of the calculated system, the output of ESC is the current control variable u of the system. esc =[u1,u2...u n ] esc Specifically, for transcritical CO2 heat pump air conditioning systems, the output u of a single-channel ESC... esc =[u1] esc Generally, it is the optimal exhaust pressure; multi-channel ESC output u esc =[u1,u2...u n ] esc Generally, this includes, but is not limited to, optimal discharge pressure, compressor speed, evaporator fan speed, and water pump speed. Therefore, the actuators connected to the ESC controller generally include, but are not limited to, PI controllers, expansion valve opening, compressors, fans, and water pump frequency converters.

[0048] In a further preferred embodiment of the present invention, the input to MPC is the system state variable x = [x1, x2...x...]. n and system disturbance d=[d1,d2...d n The output of MPC is the optimal value u of the same system control variable as ESC. mpc =[u1,u2...u n ] mpc The output value of the MPC is connected to the optimization start value module of the ESC controller, assigning or updating the optimization start value of the ESC controller. The optimal value u calculated by the MPC at system startup... mpc =[u1,u2...u n ] mpc The value is directly used as the starting point for the ESC controller to find the optimal value for the system. Based on the assigned starting value, the ESC quickly finds the accurate optimal value for the system.

[0049] Under sudden changes in system operating conditions, the optimal value u calculated by MPC mpc =[u1,u2...u n ] mpc Update the optimization starting value of the ESC controller so that the ESC controller can quickly find the optimal value of the system after a sudden change.

[0050] During the continuous and stable operation of the system, the optimal value u of the system calculated by MPC is... mpc =[u1,u2...u n ] mpc If not assigned to the ESC controller, the ESC controller will run independently according to its own optimization logic.

[0051] A further improvement of the present invention is that, for a transcritical CO2 heat pump air conditioning system, the system state variable of MPC is x = [x1, x2... x...]. n Generally, these are the refrigerant discharge pressure and the outlet temperature (water outlet temperature / air outlet temperature) of the secondary fluid on the gas cooler side. They can also be various combinations of compressor outlet discharge pressure and temperature, gas cooler outlet pressure and temperature, pressure and temperature after the expansion valve, compressor inlet suction pressure and temperature, and the inlet and outlet temperatures (water inlet / outlet / air outlet temperatures) of the secondary fluid on the evaporator and gas cooler side.

[0052] The interference amount of MPC is d = [d1, d2...d]. n This generally refers to the weather temperature over a period of time and the inlet temperature (inlet water temperature / inlet air temperature) of the secondary fluid on the gas cooler side.

[0053] The output variable u of MPC mpc =[u1,u2...u n ] mpc With the output variable u of ESC esc =[u1,u2...u n ] esc Both the type and quantity are the same.

[0054] A further improvement of this invention is that, upon system startup, the calculation result of MPC is directly assigned to ESC as the initial value. During subsequent operation, whether the calculation result of MPC is assigned to ESC to update its optimization initial value depends on the system's operating state: if the system operates continuously and smoothly, the calculation result of MPC is not input to the ESC controller, and ESC operates independently according to its own optimization logic; if the system's operating conditions change abruptly, the calculation result of MPC is input to the ESC controller, updating its optimization initial value. The basis for determining whether the system is operating continuously and smoothly or under abrupt change is the relative error between the current output of ESC and the current output of MPC, as determined by the following formula:

[0055]

[0056] In the formula, ε is the relative error, u mpc The current output calculated by the MPC controller, u escThe current output calculated for the ESC controller. For a system with only a single control variable u = [u1], if the control variable ε ≥ 15%, then the current system operating condition is considered to have changed abruptly. For a system with multiple control variables u = [u1, u2, ... u...], ... n In a system where ε ≥ 20% for any one of the control variables, the system operating condition is considered to have undergone a sudden change.

[0057] In this embodiment of the invention, the transcritical carbon dioxide heat pump air conditioning system mainly includes: a compressor, a gas cooler, a throttling valve, and an evaporator. In a further optional scheme, a regenerator can be added depending on whether the system is cooling or heating, without affecting the proposed system control logic. Additionally, the control system implementing the control method mainly includes: an ESC (Extremum Seeking Control) controller, which is a controller based on an extreme value search control algorithm; and an MPC (Model Predictive Control) controller, which is a controller based on a model predictive control algorithm. Furthermore, a PI controller can be selected based on the actual system conditions.

[0058] The embodiments of this invention are explanatory in terms of their inventive principles.

[0059] Extreme Value Search (ESC) is an adaptive feedback control method that does not require a specific model of the controlled system. It determines the real-time optimal value of the system's control variables based on the total power consumption or cooling / heating efficiency ratio (COP) of the heat pump system and the system gradient. Further explanation: the search time of ESC depends on the given initial values ​​of the control variables. If the given initial values ​​are close to the system's optimal value, the ESC search time is greatly reduced, allowing for timely response to system changes and rapid finding of the optimal value. Conversely, if the given initial values ​​are far from the system's true optimal value, the ESC search time increases significantly, failing to keep pace with changes in the optimal value of the control variables caused by changes in the external environment.

[0060] Model predictive controller (MPC) control is a predictive control method based on a model of the controlled object. It derives the optimal values ​​of the system control variables by solving the objective equation, based on the constructed mathematical model of the controlled object system and the designed objective equation, under the premise of predicted system disturbances over a future period. Further explanation is that MPC control heavily relies on the accuracy of the constructed system model. Due to the high nonlinearity of the heat pump system, while the system model is close to the actual system, there are still certain discrepancies. Therefore, the optimal solution for the system control variables calculated by MPC is generally not the exact optimal value of the system, but rather a quasi-optimal solution that is relatively close to the true optimal value.

[0061] Therefore, individual ESC or MPC control methods are limited by their own control characteristics and cannot achieve the best control results. Faced with increasingly complex and diverse working environments and operating conditions, achieving fast and accurate system optimization control is crucial to ensuring the efficient operation of transcritical CO2 heat pump air conditioning systems.

[0062] The technical solution provided by this invention can improve the optimization results of individual ESC or MPC, achieving fast and accurate optimal system control under complex operating conditions. The proposed control method is applicable to any heat pump air conditioning system using a transcritical CO2 cycle, including but not limited to CO2 heat pump water heaters, CO2 air source heat pumps, automotive CO2 heat pump air conditioning and thermal management systems, etc.

[0063] Please see Figure 2 The present invention specifically exemplifies an optimal intermediate pressure control method for a transcritical CO2 heat pump water heater; wherein,

[0064] The transcritical CO2 heat pump water heater system includes: 1. compressor, 2. gas cooler, 3. electronic expansion valve, 4. evaporator, 5. gas-liquid separator, 6. water pump, 7. fan, 8. ESC controller, 9. MPC controller, 10. first PI controller, 11. second PI controller, 12. system total power consumption calculator, 13. pressure sensor for measuring exhaust pressure, 14. first temperature sensor for measuring outlet water temperature, and 15. second temperature sensor for measuring evaporator inlet air temperature; among which,

[0065] The outlet of compressor 1 is connected to the inlet of gas cooler 2. The outlet of gas cooler 2 is connected to the inlet of electronic expansion valve 3. The outlet of electronic expansion valve 3 is connected to the inlet of evaporator 4. The outlet of evaporator 4 is connected to the inlet of gas-liquid separator 5. The outlet of gas-liquid separator 5 is connected to the inlet of compressor 1.

[0066] The measuring terminal of the first PI controller 10 is connected to the pressure sensor 13 used to measure the compressor outlet discharge pressure, the setting terminal of the first PI controller 10 is connected to the output terminal of the ESC controller 8, and the output terminal of the first PI controller 10 is connected to the input terminal of the electronic expansion valve 3.

[0067] The input terminal of ESC controller 8 is connected to the system total power consumption calculator 12, the starting value module of ESC controller 8 is connected to the output terminal of MPC controller 9, and the output terminal of ESC controller 8 is connected to the setting terminal of the first PI controller 10.

[0068] The output of MPC controller 9 is connected to the initial value module of ESC controller 8, and the inputs of MPC controller 9 are the system state variable x = [P]. dis ,T wo ] and system disturbance d=[T airThe state variables are the real-time exhaust pressure and outlet water temperature of the system measured by the pressure sensor 13 and the first temperature sensor 14, respectively, and the system interference is the real-time air inlet temperature of the evaporator air side measured by the second temperature sensor 15.

[0069] The measuring terminal of the second PI controller 11 is connected to the first temperature sensor 14, the setting terminal is set to the outlet water temperature, and the output terminal is connected to the compressor to adjust the compressor speed N in real time. comp The required outlet water temperature is met;

[0070] Furthermore, in this embodiment of the invention, the ESC controller 8 is a standard single-channel ESC controller based on a sinusoidal signal; wherein, the input of the ESC controller is the total energy consumption, measured and calculated in real time by a total power consumption calculator, which is the compressor power consumption W. comp Water pump power consumption (W) pump and evaporator fan power consumption W fan The sum of the values; the output of the ESC controller is the optimal exhaust pressure u that the ESC is searching for in the system. esc =[P opt ] esc The ESC controller's initial value module is connected to the MPC controller.

[0071] Furthermore, in this embodiment of the invention, the system state variable input to the MPC controller is x = [P dis ,T wo The input system interference is d = [T] air The output of the MPC controller is the optimal system exhaust pressure u calculated by the MPC. mpc =[P opt ] mpc The optimal exhaust pressure value calculated by MPC is connected to the optimization start value module of the ESC controller. The optimal value u calculated by MPC at system startup... mpc =[P opt ] mpc The value is directly used as the starting point for the ESC controller's optimization. Whether the MPC calculation result is used to update the ESC controller's initial optimization value during subsequent operation depends on the system's operating state: in the event of a sudden change in system operating conditions, the optimal value u calculated by the MPC will be... mpc =[P opt ] mpc The input is sent to the ESC controller to update its initial optimization value. If the system is operating continuously and stably, the optimal value u calculated by MPC will be... mpc =[P opt ] mpc If no input is sent to the ESC controller, the ESC will run independently according to its own optimization logic.

[0072] Furthermore, the rules for determining whether the system is operating continuously and stably or experiencing a sudden change in operating conditions after system startup are as follows: Calculate the u output of the ESC controller. esc =[P opt ] esc and the output of the MPC controller u mpc =[P opt ] mpc The relative error is determined by the following formula:

[0073]

[0074] Where ε is the relative error, if the control variable ε ≥ 15%, it is considered that a sudden change has occurred in the current system operating condition, and the output u of the MPC controller will be... mpc =[P opt ] mpc The initial value needs to be updated in the ESC controller.

[0075] Based on the above specific embodiments, it can be seen that the present invention discloses a control method for a transcritical CO2 heat pump water heater, which solves the problem of controlling the optimal exhaust pressure of a transcritical CO2 heat pump water heater.

[0076] In summary, this invention discloses a two-layer control method for a transcritical CO2 heat pump air conditioning system combining MPC and ESC. The ESC controller serves as the bottom-layer controller, responsible for the precise control of system control variables; the MPC controller serves as the upper-layer controller, responsible for the initial calculation of system control variables. The MPC controller is assigned initial values ​​at system startup or updated to these initial values ​​in the event of sudden changes in system operating conditions. The technical solution provided by this invention improves the optimization speed of the ESC controller, solves the problem that the ESC controller cannot keep up with rapid changes in the optimal values ​​of control variables caused by changes in the external environment, and enables real-time optimal operation of the transcritical CO2 heat pump air conditioning system in complex application scenarios.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A control method of a transcritical carbon dioxide heat pump air conditioning system, characterized by, include: Using the ESC controller as the underlying controller, the system inputs the initial optimization value, performs optimization, and outputs the optimal value of the control variables of the transcritical carbon dioxide heat pump air conditioning system. The optimal value output by the ESC controller is used to assign the execution structure of the transcritical carbon dioxide heat pump air conditioning system to control the system operation. The MPC controller is used as the upper-level controller, connected to the ESC controller, and synchronously calculates the optimal value of the control variable, and outputs the calculation result; Specifically, when the transcritical carbon dioxide heat pump air conditioning system is started, the calculation result output by the MPC controller is used as the optimization starting value of the ESC controller; when the operating conditions of the transcritical carbon dioxide heat pump air conditioning system change abruptly, the calculation result output by the MPC controller is used to update the optimization starting value of the ESC controller; when the transcritical carbon dioxide heat pump air conditioning system is running continuously and stably, the calculation result output by the MPC controller is not input into the ESC controller, and the ESC controller runs independently according to its own optimization logic.

2. The control method for a transcritical carbon dioxide heat pump air conditioning system according to claim 1, characterized in that, The input to the ESC controller is the measured total energy consumption or the calculated cooling and heating energy efficiency ratio; The output of the ESC controller is the current control variable.

3. The control method for a transcritical carbon dioxide heat pump air conditioning system according to claim 2, characterized in that, The ESC controller is either a single-output, single-channel ESC controller or a multi-output, multi-channel ESC controller.

4. The control method for a transcritical carbon dioxide heat pump air conditioning system according to claim 3, characterized in that, The output of the single-output, single-channel ESC controller is the optimal exhaust pressure; The output of the multi-output multi-channel ESC controller includes multiple parameters such as optimal exhaust pressure, compressor speed, evaporator fan speed, and water pump speed.

5. The control method for a transcritical carbon dioxide heat pump air conditioning system according to claim 2, characterized in that, The inputs to the MPC controller are system state variables and system disturbances; The output of the MPC controller is the same in type and quantity as the output of the ESC controller.

6. The control method for a transcritical carbon dioxide heat pump air conditioning system according to claim 1, characterized in that, Based on the comparison between the relative error between the current output of the ESC controller and the current output of the MPC controller and the preset error threshold, it is determined whether the transcritical carbon dioxide heat pump air conditioning system is operating continuously and stably or experiencing a sudden change in operating conditions.

7. The control method for a transcritical carbon dioxide heat pump air conditioning system according to claim 6, characterized in that, The expression for calculating the relative error is as follows: ； wherein is the relative error; is the current output of the MPC controller; is the current output of the ESC controller.

8. A control system for a transcritical carbon dioxide heat pump air conditioning system, characterized in that, include: The ESC controller is used as a low-level controller. It takes an initial optimization value as input, performs optimization, and outputs the optimal value of the control variables of the transcritical carbon dioxide heat pump air conditioning system. The optimal value output by the ESC controller is used to assign the execution structure of the transcritical carbon dioxide heat pump air conditioning system to control the operation of the system. The MPC controller is used as an upper-level controller to connect with the ESC controller, synchronously calculate the optimal values ​​of the control variables, and output the calculation results. Specifically, when the transcritical carbon dioxide heat pump air conditioning system is started, the calculation result output by the MPC controller is used as the optimization starting value of the ESC controller; when the operating conditions of the transcritical carbon dioxide heat pump air conditioning system change abruptly, the calculation result output by the MPC controller is used to update the optimization starting value of the ESC controller; when the transcritical carbon dioxide heat pump air conditioning system is running continuously and stably, the calculation result output by the MPC controller is not input into the ESC controller, and the ESC controller runs independently according to its own optimization logic.

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