Control system and method for thermal management system of transcritical carbon dioxide new energy vehicle

Abstract

The present invention discloses a control system and method for a transcritical CO2 new energy vehicle thermal management system, the control system comprising: an exhaust pressure PID controller, the input of which is the exhaust pressure value, and the output of which is the opening of the second two-way throttle valve; an outlet water temperature PID controller, the input of which is the outlet water temperature value of the coolant, and the output of which is the opening of the first two-way throttle valve; an air supply temperature PID controller, the input of which is the cabin air supply temperature value, and the output of which is the speed of the compressor; a cabin temperature PID controller, the input of which is the cabin temperature value, and the output of which is the speed of the indoor fan; an intermediate temperature PID controller, the input of which is the intermediate temperature value, and the output of which is the opening of the full-throttle valve. The present invention can improve the response speed and stability of the dynamic control of the transcritical CO2 new energy vehicle thermal management system, and can realize real-time and accurate optimization control of the cabin temperature and humidity and the battery temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal management of new energy vehicles, and in particular relates to a control system and method for a thermal management system of a transcritical carbon dioxide new energy vehicle. Background Art

[0002] The application and popularization of new energy electric vehicles have alleviated the problems of environmental pollution and fossil energy shortage. Due to the lack of recyclable engine waste heat, independent heat pump systems have become an indispensable part of new energy electric vehicles.

[0003] At present, electric vehicles mainly use R134a heat pump air-conditioning systems; however, R134a's heating performance in winter is poor. In order to ensure the thermal comfort of passengers, electric vehicles often use PTC auxiliary electric heating to provide additional heat for the car; in addition, R134a's GWP value is as high as 1430, which is very unfriendly to the environment and is facing the situation of being completely eliminated.

[0004] As a pure natural refrigerant, CO2 has become one of the most ideal alternative refrigerants of the new generation due to its non-toxic, pollution-free and low-priced characteristics. Compared with PTC auxiliary electric heating, CO2 heat pumps have superior heating performance, which can save a lot of battery power in winter and indirectly extend the driving range of electric vehicles. The CO2 thermal management system has many parameters that can be optimized and the control is very complex: first, the driving conditions of electric vehicles are complex and diverse, resulting in too much interference in the temperature and humidity control of the cabin; second, the battery of electric vehicles has very strict requirements on the operating temperature, and the battery temperature must be monitored and controlled in real time; third, compared with the traditional refrigeration cycle, the CO2 cycle has an additional performance optimization object, namely the optimal exhaust pressure.

[0005] In summary, in a complex and diverse working environment, real-time and accurate optimization and control of the temperature and humidity in the car, the temperature of the battery, and ensuring the minimum power consumption of the system have become one of the huge challenges currently faced by the thermal management system of electric vehicles. A new control system and method for the thermal management system of transcritical carbon dioxide new energy vehicles is urgently needed. Summary of the invention

[0006] The purpose of the present invention is to provide a control system and method for a transcritical carbon dioxide new energy vehicle thermal management system to solve one or more of the above-mentioned technical problems. The technical solution provided by the present invention can improve the response speed and stability of the dynamic control of the transcritical CO2 new energy vehicle thermal management system, and can achieve real-time and accurate optimization control of the temperature and humidity of the vehicle compartment and the temperature of the battery.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a control system for a transcritical carbon dioxide new energy vehicle thermal management system.

[0009] The transcritical carbon dioxide new energy vehicle thermal management system includes: a compressor, a four-way reversing valve, an outdoor heat exchanger, a regenerator, a water cooler, a main heat exchanger, an auxiliary heat exchanger, a liquid reservoir, a first two-way throttle valve, a second two-way throttle valve and a full-pass throttle valve;

[0010] The compressor, the four-way reversing valve, the outdoor heat exchanger, the regenerator, the water cooler, the main heat exchanger, the auxiliary heat exchanger, the liquid storage device, the first two-way throttle valve, the second two-way throttle valve and the full-throttle valve constitute a refrigerant circulation loop; wherein the first two-way throttle valve is arranged on the connecting pipe between the regenerator and the water cooler, the second two-way throttle valve is arranged on the connecting pipe between the main heat exchanger and the regenerator, and the full-throttle valve is arranged on the connecting pipe between the main heat exchanger and the auxiliary heat exchanger;

[0011] The main heat exchanger and the auxiliary heat exchanger are used to realize refrigerant heat exchange and supply air to the vehicle compartment;

[0012] The water cooler is used to realize refrigerant heat exchange and output coolant for cooling batteries and motors;

[0013] The control system comprises:

[0014] Exhaust pressure PID controller, the input is the exhaust pressure value, and the output is the opening of the second two-way throttle valve;

[0015] The outlet water temperature PID controller has an input of the outlet water temperature value of the coolant and an output of the opening of the first two-way throttle valve;

[0016] The input of the air supply temperature PID controller is the cabin air supply temperature value, and the output is the speed of the compressor;

[0017] The input of the cabin temperature PID controller is the cabin temperature value, and the output is the speed of the indoor fan;

[0018] The intermediate temperature PID controller has the intermediate temperature value as input and the opening of the full-throttle valve as output.

[0019] A further improvement of the present invention is that in the transcritical carbon dioxide new energy vehicle thermal management system,

[0020] The outlet of the compressor is connected to the A port of the four-way reversing valve;

[0021] The C port of the four-way reversing valve is connected to the inlet of the compressor via the liquid accumulator and the first heat exchange channel of the regenerator in sequence;

[0022] The D port of the four-way reversing valve is connected to the inlet of the second heat exchange channel of the regenerator via the first heat exchange channel of the auxiliary heat exchanger, the full-pass throttle valve, the first heat exchange channel of the main heat exchanger, and the second two-way throttle valve in sequence; the D port of the four-way reversing valve is also connected to the inlet of the second heat exchange channel of the regenerator via the first heat exchange channel of the water cooler and the first two-way throttle valve in sequence;

[0023] The outlet of the second heat exchange channel of the regenerator is connected to the B port of the four-way reversing valve through the first heat exchange channel of the outdoor heat exchanger;

[0024] The second heat exchange channel of the outdoor heat exchanger is used to blow in outdoor air through the outdoor fan;

[0025] The second heat exchange channel of the main heat exchanger and the second heat exchange channel of the auxiliary heat exchanger are both used for blowing in fresh air and return air through the indoor fan.

[0026] A further improvement of the present invention is that the refrigerant arranged in the refrigerant circulation loop is CO2.

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

[0028] When in cabin cooling mode, the A port of the four-way reversing valve is connected to the B port and the C port is connected to the D port. The opening of the second two-way throttle valve is determined by the cabin cooling capacity demand and is adjusted by the exhaust pressure PID controller. The full-throttle valve is fully open.

[0029] When in the cabin dehumidification mode, the A port of the four-way reversing valve is connected to the D port and the B port is connected to the C port. The opening of the second two-way throttle valve is determined according to the exhaust pressure and adjusted by the exhaust pressure PID controller; the opening of the full-throttle valve is determined by the dehumidification demand and adjusted by the intermediate temperature PID controller.

[0030] When the cabin is in heating mode, port A of the four-way reversing valve is connected to port D and port B is connected to port C. The opening of the second two-way throttle valve is determined according to the exhaust pressure and adjusted by the exhaust pressure PID controller. The full-throttle valve is fully open.

[0031] A further improvement of the present invention is that when the transcritical carbon dioxide new energy vehicle thermal management system is in each mode, the working conditions of each PID controller are as shown in the following table:

[0032] Functional Mode PID startup number N PID1 PID2 PID3 PID4 PID5 Cabin and battery cooling 4 Work Work Work Work Not Started Cabin cooling only 3 Work Not Started Work Work Not Started Battery cooling only 2 Work Work Not Started Not Started Not Started Dehumidification of the cabin 4 Work Not Started Work Work Work Cabin dehumidification and battery cooling 5 Work Work Work Work Work Cabin dehumidification and battery heating 5 Work Work Work Work Work Dual heating for cabin and battery 4 Work Work Work Work Not Started Battery heating only 2 Work Work Not Started Not Started Not Started Cabin heating only 3 Work Not Started Work Work Not Started ;

[0033] In the table, PID1 is the exhaust pressure PID controller; PID2 is the water outlet temperature PID controller; PID3 is the air supply temperature PID controller; PID4 is the cabin temperature PID controller; PID5 is the intermediate temperature PID controller.

[0034] A further improvement of the present invention is that

[0035] When in cabin and battery cooling mode, the startup sequence of the PID controller is PID1, PID3, PID4, PID2;

[0036] When in cabin cooling only mode, the startup sequence of the PID controllers is PID1, PID3, and PID4;

[0037] When in battery cooling mode only, the PID startup sequence is PID1, PID2;

[0038] When in cabin dehumidification mode, the startup sequence of the PID controller is PID1, PID3, PID5, and PID4;

[0039] When in cabin dehumidification and battery cooling mode, the startup sequence of the PID controller is PID1, PID3, PID5, PID4, PID2;

[0040] When in cabin dehumidification and battery heating mode, the startup sequence of the PID controller is PID1, PID3, PID5, PID4, PID2;

[0041] When in cabin and battery dual heating mode, the startup sequence of the PID controller is PID1, PID3, PID4, PID2;

[0042] When in battery heating mode only, the startup sequence of the PID controller is PID1, PID2;

[0043] When in cabin heating only mode, the startup sequence of the PID controllers is PID1, PID3, and PID4.

[0044] A further improvement of the present invention is that

[0045] In the startup sequence of each functional mode, after the first PID controller is started, the delay time of the latter PID controller is one third to two thirds of the time required for the previous PID controller to stabilize control alone.

[0046] A further improvement of the present invention is that the coolant outlet temperature controlled by PID2 adopts a segmented control method.

[0047] The present invention provides a control method for a transcritical carbon dioxide new energy vehicle thermal management system.

[0048] The control method is based on the above-mentioned control system of the present invention;

[0049] The control method optimizes the coupled startup control performance of multiple PID controllers from two perspectives of startup sequence and startup time of the PID controllers.

[0050] A further improvement of the present invention is that the step of optimizing the coupled startup control performance of multiple PID controllers from two perspectives of startup sequence and startup time of the PID controllers comprises:

[0051] The PID coupling control optimization process is combined with the response surface analysis method, and the startup sequence and startup time of the PID controller are used as factors of the response surface analysis method;

[0052] The steepest ramp test is used to select the reasonable horizontal step length and change direction for the start-up sequence and start-up time, so as to quickly approach the maximum response area during analysis;

[0053] Confirm the response value and its target, use central composite experimental design or Box-Behnken experimental design method to perform response surface analysis and complete the optimization.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] The functions that can be realized in the control of the existing transcritical carbon dioxide system are not comprehensive enough, and it is impossible to perform accurate and rapid dynamic real-time control of multiple targets at the same time, and at the same time meet the requirements of human comfort, battery operation safety and optimal thermal management performance; in view of the defects of the above-mentioned prior art, the present invention proposes a control method for a transcritical carbon dioxide new energy vehicle thermal management system, specifically a multi-PID coupling dynamic control performance optimization method for a transcritical CO2 new energy vehicle thermal management system, discloses the dynamic control logic of different functional modes, can improve the stability and stabilization speed of the dynamic control of the transcritical CO2 new energy vehicle thermal management system, and can meet the requirements of human comfort and performance optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art; obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0057] Figure 1 This is a control logic diagram of a transcritical CO2 new energy vehicle thermal management system provided by an embodiment of the present invention;

[0058] Figure 2 is a schematic diagram of a transcritical CO2 new energy vehicle thermal management system in an embodiment of the present invention;

[0059] In the figure, 1. compressor; 2. four-way reversing valve; 3. outdoor heat exchanger; 4. regenerator; 5. water cooler; 6. main heat exchanger; 7. auxiliary heat exchanger; 8. liquid storage tank; 9. first two-way throttle valve; 10. second two-way throttle valve; 11. full-pass throttle valve; 12. pump. DETAILED DESCRIPTION

[0060] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0061] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0062] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0063] See also Figure 1 and Figure 2 A transcritical CO2 new energy vehicle thermal management system according to an embodiment of the present invention comprises: a refrigerant circulation circuit, an air circulation circuit for cabin air supply, and a coolant circulation circuit system for battery and motor liquid cooling; wherein, the refrigerant circulation circuit is composed of a compressor 1, a four-way reversing valve 2, an outdoor heat exchanger 3, a regenerator 4, a water cooler 5, a main heat exchanger 6, an auxiliary heat exchanger 7, a liquid storage tank 8, a first two-way throttle valve 9, a second two-way throttle valve 10 and a full-pass throttle valve 11; the air circulation circuit for cabin air supply is composed of an indoor fan and an HVAC box; the coolant circulation circuit for battery and motor liquid cooling is composed of components such as a battery module and a pump 12.

[0064] In the embodiment of the present invention, the outlet of the compressor 1 is connected to the A port of the four-way reversing valve 2; the C port of the four-way reversing valve 2 is connected to the inlet of the compressor 1 through the liquid reservoir 8 and the first heat exchange channel of the regenerator 4 in sequence; the D port of the four-way reversing valve 2 is connected to the inlet of the second heat exchange channel of the regenerator 4 through the first heat exchange channel of the auxiliary heat exchanger 7, the full-pass throttle valve 11, the first heat exchange channel of the main heat exchanger 6, and the second two-way throttle valve 10 in sequence; the D port of the four-way reversing valve 2 is also connected to the inlet of the second heat exchange channel of the regenerator 4 through the first heat exchange channel of the water cooler 5 and the first two-way throttle valve 9 in sequence; the outlet of the second heat exchange channel of the regenerator 4 is connected to the B port of the four-way reversing valve 2 through the first heat exchange channel of the outdoor heat exchanger 3; the outlet of the second heat exchange channel of the water cooler 5 is connected to the inlet of the second heat exchange channel of the water cooler 5 after passing through the pump 12, the motor to be cooled, and the battery;

[0065] An outdoor blower is provided at the second heat exchange channel of the outdoor heat exchanger 3 for blowing in outdoor air through the outdoor blower;

[0066] The main heat exchanger 6 and the auxiliary heat exchanger 7 are contained in the HVAC box, and the second heat exchange channel of the main heat exchanger 6 and the second heat exchange channel of the auxiliary heat exchanger 7 are both used to blow in fresh air and return air through the indoor fan.

[0067] See also Figure 1 and Figure 2 In an embodiment of the present invention, a multi-PID coupled dynamic control performance optimization method for a transcritical CO2 new energy vehicle thermal management system includes: each of the three circulation loops of the above-mentioned transcritical CO2 new energy vehicle thermal management system has a target parameter, and real-time and precise control is performed through a PID controller to ensure that the system meets the thermal comfort requirements of the passenger compartment and the battery thermal management requirements in real time, while always operating at the best performance.

[0068] Specifically, the refrigerant circulation loop includes five PID controllers, and the control target parameters are exhaust pressure (P dis ), compartment air supply temperature (T air ), compartment temperature (T cab ), battery liquid cooling water outlet temperature (T wat ) and the intermediate temperature (T mid ); Among them, the input of the exhaust pressure PID controller (PID1) is the real-time exhaust pressure value (P dis ), the output is the opening degree of the second two-way throttle valve 10 (EXV ope1); the input of the outlet water temperature PID controller (PID2) of the battery liquid cooling is the real-time value of the outlet water temperature (T wat ), the output is the opening of the first two-way throttle valve 9 (EXV ope2 ); the input of the air supply temperature PID controller (PID3) is the real-time value of the cabin air supply temperature (T air ), the output is the real-time speed of compressor 1 (N rpm ); the input of the cabin temperature PID controller (PID4) is the real-time value of the cabin temperature (T cab ), the output is the indoor fan (N fan ) speed, the input of the intermediate temperature PID controller (PID5) is the real-time value of the intermediate temperature (T mid ), the output is the opening of the full-throttle valve 11 (EXV ope3 ).

[0069] The dynamic performance optimization of the embodiment of the present invention is mainly divided into the following two steps: first, the PID parameters are tuned and optimized; then, the multi-PID coupling startup control performance is optimized from the two perspectives of the startup sequence and startup time of the PID controller.

[0070] In the embodiment of the present invention, the thermal management system of the transcritical CO2 new energy vehicle can realize multiple functional mode adjustments, including: the combination of the refrigerant circulation loop system and the air circulation system can realize the cooling, heating and dehumidification functions of the cabin; the combination of the refrigerant circulation loop and the water circulation loop can realize the active cooling function of the battery and the motor. Each functional mode is mainly divided into three groups, a high-temperature cooling demand functional group, a dehumidification functional group and a low-temperature heating functional group; the functional modes in each functional demand group can be operated separately or randomly arranged and combined according to actual needs. The functional modes of the cooling demand group include: cabin cooling, battery cooling and motor cooling modes; the functional modes of the dehumidification demand group include cabin air dehumidification mode, battery cooling, motor cooling and battery heating mode; the functional modes of the heating demand group include cabin heating and battery heating modes; each functional mode is adjusted and switched by the valve opening.

[0071] In the embodiment of the present invention, the working state of the first two-way throttle valve 9 and the pump 12 is consistent with the battery cooling mode; the opening of the four-way reversing valve 2, the second two-way throttle valve 10, and the full-throttle valve 11 is closely related to the cabin mode. When in the cabin cooling mode, the AB end and the CD end of the four-way reversing valve 2 are connected, the opening of the second two-way throttle valve 10 is determined by the cabin cooling capacity demand, and is adjusted in real time by the PID1 controller, and the full-throttle valve 11 is fully opened; when in the cabin dehumidification mode, the AD end and the BC end of the four-way reversing valve 2 are connected, the opening of the second two-way throttle valve 10 is determined by the exhaust pressure, and is adjusted in real time by the PID1 controller, and the opening of the full-throttle valve 11 is determined by the dehumidification capacity demand, and is adjusted in real time by the PID5 controller; when the cabin is in the heating mode, the AD end and the BC end of the four-way reversing valve 2 are connected, the opening of the second two-way throttle valve 10 is determined by the exhaust pressure, and is adjusted in real time by the PID1 controller, and the full-throttle valve 11 is fully opened.

[0072] The embodiments of the present invention are specifically explained. The working conditions of each PID controller in each mode are shown in Table 1; wherein, motor cooling does not require precise coolant temperature control, and whether the motor cooling function is started has no effect on the PID control optimization, so it is not listed separately in the following table.

[0073] Table 1. Working conditions of each PID controller in each mode

[0074] Functional Mode PID startup number N PID1 PID2 PID3 PID4 PID5 Cabin and battery cooling 4 Work Work Work Work Not Started Cabin cooling only 3 Work Not Started Work Work Not Started Battery cooling only 2 Work Work Not Started Not Started Not Started Dehumidification of the cabin 4 Work Not Started Work Work Work Cabin dehumidification and battery cooling 5 Work Work Work Work Work Cabin dehumidification and battery heating 5 Work Work Work Work Work Dual heating for cabin and battery 4 Work Work Work Work Not Started Battery heating only 2 Work Work Not Started Not Started Not Started Cabin heating only 3 Work Not Started Work Work Not Started

[0075] The refrigerant used in the embodiment of the present invention is natural working fluid CO2, which is environmentally friendly, low-priced, economical, and has outstanding heating performance, and meets the modern development requirements of sustainable development of green economy. The present invention introduces the dynamic control logic of different functional modes, and provides optimization suggestions for dynamic control for each functional mode, thereby improving the stability and stabilization speed of dynamic control of the thermal management system of transcritical CO2 new energy vehicles.

[0076] In the embodiment of the present invention, when the thermal management system is in the dual cooling mode of the cabin and the battery, except for the PID controller 5, the other four PID controllers need to be started (ie, N=4); therefore, the startup sequence of the four PID controllers is The specific types are shown in Table 2.

[0077] Table 2. Start-up order of four PID controllers

[0078] 1234 2134 3124 4123 1243 2143 3142 4132 1324 2314 3214 4213 1342 2341 3241 4231 1423 2413 3412 4312 1432 2431 3421 4321

[0079] In the embodiment of the present invention, when the thermal management system is in the state of cabin cooling only (i.e., air conditioning cooling), a total of three PID controllers, PID1, PID3, and PID4, start working (i.e., N=3), so the startup sequence of the PIDs is The logic is the same as above.

[0080] In the embodiment of the present invention, when the thermal management system is in battery cooling mode, two PID controllers, PID1 and PID2, are started (ie, N=2). Therefore, the startup sequence of the PID controllers is The logic is the same as above.

[0081] In the embodiment of the present invention, when the thermal management system is in the cabin dehumidification mode, PID1, PID3, PID4 and PID5, a total of four PID controllers, are started (ie, N=4). Therefore, the startup sequence of the PIDs is The logic is the same as above.

[0082] In the embodiment of the present invention, when the thermal management system is in the cabin dehumidification and battery cooling mode, all five PID controllers need to be started (ie, N=5), so the startup sequence of the PID controllers is The logic is the same as above.

[0083] In the embodiment of the present invention, when the thermal management system is in the cabin dehumidification and battery heating mode, all five PID controllers need to be started (ie, N=5), so the startup sequence of the PID controllers is The logic is the same as above.

[0084] In the embodiment of the present invention, when the thermal management system is in dual heating of the cabin and the battery, except for PID controller 5, the other four PID controllers need to be started (ie, N=4), so the starting sequence of the PID controllers is The logic is the same as above.

[0085] In the embodiment of the present invention, when the thermal management system is in air conditioning heating mode, PID1, PID3 and PID4, a total of three PID controllers, start working (i.e., N=3), so the startup sequence of the PIDs is The logic is the same as above.

[0086] In the embodiment of the present invention, when the thermal management system is in battery heating, two PID controllers, PID1 and PID2, start working (ie, N=2), so the startup sequence of the PIDs is The logic is the same as above.

[0087] Based on the above statements, it can be seen that the number of pre-test conditions is very large, and it is necessary to combine the PID coupling control optimization process experiment with the response surface analysis method. The start-up sequence and start-up time of the PID controller are the factors of the response surface analysis method; on this basis, the steepest climbing test is used to screen out the most reasonable horizontal step size and change direction for the above two factors, so as to approach the maximum response area as quickly as possible during analysis; then, confirm the response value and its target, and finally use the central composite experimental design or Box-Behnken experimental design method for response surface analysis.

[0088] In an embodiment of the present invention, when the system is in the cabin and battery cooling mode, the recommended startup sequence of the PID controller is 1342; when the system is in the cabin cooling mode only, the recommended startup sequence of the PID controller is 134; when the system is in the battery cooling mode only, the recommended startup sequence of the PID is 12; when the system is in the cabin dehumidification mode, the recommended startup sequence of the PID controller is 1354; when the system is in the cabin dehumidification and battery cooling mode, the recommended startup sequence of the PID controller is 13542; when the system is in the cabin dehumidification and battery heating mode, the recommended startup sequence of the PID controller is 13542; when the system is in the cabin and battery dual heating mode, the recommended startup sequence of the PID controller is 1342; when the system is in the battery heating mode only, the recommended startup sequence of the PID controller is 12; when the system is in the cabin heating mode only, the recommended startup sequence of the PID controller is 134.

[0089] In the preferred embodiment of the present invention, under the optimal startup sequence of each functional mode, after the first PID controller is started, the delay time of the next PID controller to start is recommended to be one-third to two-thirds of the time required for the previous PID controller to stabilize when it is in separate control. Specifically, taking the system in the cabin and battery cooling mode as an example, the recommended startup sequence of the PID controller is 1342; if the stable time of PID controllers 1234 when controlled separately is t1, t2, t3, t4 respectively. Then after PID1 controller is started, the recommended delay time for PID2 controller to start is The recommended delay time for the PID3 controller to start is The recommended delay time for the PID4 controller to start is The specific duration can be adjusted according to actual needs. If the actual control requires a higher fluctuation amplitude of the control component, it is recommended to select a longer delay duration. If the control stability speed is required to be higher, it is recommended to select a shorter delay duration.

[0090] In the preferred embodiment of the present invention, since the proportion of water in the coolant is very high, the coolant temperature has a low response sensitivity to the opening adjustment. Therefore, in order to accelerate the control stability, the coolant outlet temperature controlled by PID2 adopts a segmented control method. According to the temperature difference (ΔT c ) range, the control is divided into three stages, each stage PID controller has different control parameters. The recommended value of temperature control stage partition is large temperature difference (ΔT c >3) High-speed adjustment stage, small temperature difference (3≥ΔT c ≥1) Low speed adjustment stage and stabilization (1>ΔT c ) Fine-tuning stage.

[0091] In summary, the embodiment of the present invention discloses a multi-PID coupled dynamic control performance optimization method for a transcritical CO2 new energy vehicle thermal management system; wherein the transcritical CO2 new energy vehicle thermal management system is composed of three circulation loops: a refrigerant circulation loop, an air circulation loop for cabin air supply, and a coolant circulation loop system for battery and motor liquid cooling. In order to ensure that the system can meet the thermal comfort requirements of the passenger compartment and the thermal management requirements of the battery in real time while always operating at the best performance, the dynamic control of the transcritical CO2 new energy vehicle thermal management system is mainly divided into five parts: exhaust pressure (P dis ) control, compartment air supply temperature (T air ) control, cabin temperature (T cab ) control, battery liquid cooling water outlet temperature (T wat ) control and the intermediate temperature between the main heat exchanger and the defrost heat exchanger (T mid ) control. The present invention provides a PID coupling dynamic control performance optimization solution in a full-operating multifunctional mode from the perspectives of the controller's startup sequence and delay duration. The present invention solves the problems of slow dynamic control response speed and long stabilization time of the transcritical CO2 new energy vehicle thermal management system, promotes the application and popularization of pure natural refrigerant CO2, promotes the development of electric vehicles and related industries, and makes significant contributions to environmental protection, alleviating the fossil energy crisis, and achieving carbon neutrality and carbon peak.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does 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 system for a transcritical carbon dioxide new energy vehicle thermal management system, characterized in that: The transcritical carbon dioxide new energy vehicle thermal management system comprises: a compressor (1), a four-way reversing valve (2), an outdoor heat exchanger (3), a regenerator (4), a water cooler (5), a main heat exchanger (6), an auxiliary heat exchanger (7), a liquid storage device (8), a first two-way throttle valve (9), a second two-way throttle valve (10) and a full-pass throttle valve (11); The compressor (1), the four-way reversing valve (2), the outdoor heat exchanger (3), the regenerator (4), the water cooler (5), the main heat exchanger (6), the auxiliary heat exchanger (7), the liquid storage device (8), the first two-way throttle valve (9), the second two-way throttle valve (10) and the full-throttle valve (11) constitute a refrigerant circulation loop; wherein the first two-way throttle valve (9) is arranged on the connecting pipe between the regenerator (4) and the water cooler (5), the second two-way throttle valve (10) is arranged on the connecting pipe between the main heat exchanger (6) and the regenerator (4), and the full-throttle valve (11) is arranged on the connecting pipe between the main heat exchanger (6) and the auxiliary heat exchanger (7); The main heat exchanger (6) and the auxiliary heat exchanger (7) are used to realize heat exchange of the refrigerant and supply air to the vehicle compartment; The water cooler (5) is used to realize heat exchange of the refrigerant and output a coolant for cooling the battery and the motor; The control system comprises: An exhaust pressure PID controller, the input of which is the exhaust pressure value, and the output of which is the opening of the second two-way throttle valve (10); An outlet water temperature PID controller, the input of which is the outlet water temperature value of the coolant, and the output of which is the opening degree of the first two-way throttle valve (9); The air supply temperature PID controller has the following input: the cabin air supply temperature value; the output: the speed of the compressor (1); The input of the cabin temperature PID controller is the cabin temperature value, and the output is the speed of the indoor fan; The input of the intermediate temperature PID controller is the intermediate temperature value, and the output is the opening of the full-pass throttle valve (11).

2. The control system of a transcritical carbon dioxide new energy vehicle thermal management system according to claim 1, characterized in that: In the transcritical carbon dioxide new energy vehicle thermal management system, The outlet of the compressor (1) is connected to the port A of the four-way reversing valve (2); The C port of the four-way reversing valve (2) is connected to the inlet of the compressor (1) via the liquid storage device (8) and the first heat exchange channel of the regenerator (4) in sequence; The D port of the four-way reversing valve (2) is connected to the inlet of the second heat exchange channel of the regenerator (4) via the first heat exchange channel of the auxiliary heat exchanger (7), the full-pass throttle valve (11), the first heat exchange channel of the main heat exchanger (6), and the second two-way throttle valve (10) in sequence; the D port of the four-way reversing valve (2) is also connected to the inlet of the second heat exchange channel of the regenerator (4) via the first heat exchange channel of the water cooler (5), the first two-way throttle valve (9) in sequence; The outlet of the second heat exchange channel of the regenerator (4) is connected to the B port of the four-way reversing valve (2) via the first heat exchange channel of the outdoor heat exchanger (3); The second heat exchange channel of the outdoor heat exchanger (3) is used to blow in outdoor air through the outdoor fan; The second heat exchange channel of the main heat exchanger (6) and the second heat exchange channel of the auxiliary heat exchanger (7) are both used to blow in fresh air and return air through the indoor fan.

3. The control system of a transcritical carbon dioxide new energy vehicle thermal management system according to claim 1, characterized in that: The refrigerant arranged in the refrigerant circulation circuit is CO2.

4. The control system of a transcritical carbon dioxide new energy vehicle thermal management system according to claim 1, characterized in that: When in the cabin cooling mode, the A port of the four-way reversing valve (2) is connected to the B port and the C port is connected to the D port, the opening of the second two-way throttle valve (10) is determined by the cabin cooling capacity demand and is adjusted by the exhaust pressure PID controller; the full-throttle valve (11) is fully open; When in the cabin dehumidification mode, the A port of the four-way reversing valve (2) is connected to the D port and the B port is connected to the C port, the opening of the second two-way throttle valve (10) is determined according to the exhaust pressure and is adjusted by the exhaust pressure PID controller; the opening of the full-pass throttle valve (11) is determined according to the dehumidification demand and is adjusted by the intermediate temperature PID controller; When the vehicle compartment is in heating mode, the A port and the D port of the four-way reversing valve (2) are connected and the B port and the C port are connected, the opening of the second two-way throttle valve (10) is determined according to the exhaust pressure and adjusted by the exhaust pressure PID controller, and the full-throttle valve (11) is fully opened.

5. The control system of a transcritical carbon dioxide new energy vehicle thermal management system according to claim 1, characterized in that: When the transcritical carbon dioxide new energy vehicle thermal management system is in each mode, the working conditions of each PID controller are shown in the following table: ； In the table, PID1 is the exhaust pressure PID controller; PID2 is the water outlet temperature PID controller; PID3 is the air supply temperature PID controller; PID4 is the cabin temperature PID controller; PID5 is the intermediate temperature PID controller.

6. The control system of a transcritical carbon dioxide new energy vehicle thermal management system according to claim 5, characterized in that: When in cabin and battery cooling mode, the startup sequence of the PID controller is PID1, PID3, PID4, PID2; When in cabin cooling only mode, the PID controller startup sequence is PID1, PID3, PID4; When in battery cooling mode only, the PID startup sequence is PID1, PID2; When in cabin dehumidification mode, the startup sequence of the PID controller is PID1, PID3, PID5, and PID4; When in cabin dehumidification and battery cooling mode, the startup sequence of the PID controller is PID1, PID3, PID5, PID4, PID2; When in cabin dehumidification and battery heating mode, the startup sequence of the PID controller is PID1, PID3, PID5, PID4, PID2; When in cabin and battery dual heating mode, the startup sequence of the PID controller is PID1, PID3, PID4, PID2; When in battery heating mode only, the startup sequence of the PID controller is PID1, PID2; When in cabin heating only mode, the startup sequence of the PID controllers is PID1, PID3, and PID4.

7. The control system of a transcritical carbon dioxide new energy vehicle thermal management system according to claim 6, characterized in that: In the startup sequence of each functional mode, after the first PID controller is started, the delay time of the latter PID controller is one third to two thirds of the time required for the previous PID controller to stabilize control alone.

8. The control system of a transcritical carbon dioxide new energy vehicle thermal management system according to claim 6, characterized in that: The coolant outlet temperature controlled by PID2 adopts segmented control method.

9. A control method for a transcritical carbon dioxide new energy vehicle thermal management system, characterized in that: The control method is based on the control system according to claim 1; The control method optimizes the coupled startup control performance of multiple PID controllers from two perspectives of startup sequence and startup time of the PID controllers.

10. The control method according to claim 9, characterized in that: The steps of optimizing the coupled startup control performance of multiple PID controllers from two perspectives of startup sequence and startup time of the PID controllers include: The PID coupling control optimization process is combined with the response surface analysis method, and the startup sequence and startup time of the PID controller are used as factors of the response surface analysis method; The steepest ramp test is used to select the reasonable horizontal step length and change direction for the start-up sequence and start-up time, so as to quickly approach the maximum response area during analysis; Confirm the response value and its target, use central composite experimental design or Box-Behnken experimental design method to perform response surface analysis and complete the optimization.

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