A thermal management system and control method for waste heat recovery from fresh air in electric vehicles

Abstract

This invention discloses a waste heat recovery management system and control method for electric vehicles, belonging to the field of waste heat recovery technology. The system does not alter the original system loop structure of the vehicle. It delivers exhaust air from the passenger compartment to the condenser, mixing the exhaust air with incoming outside air; alternatively, a gas heat exchanger component is added to the HVAC assembly, which exchanges heat between the passenger compartment exhaust air and the blower intake air through an internal heat exchange filter; or a small evaporator is added to the original heat pump air conditioning system loop, located between the compressor and condenser; the evaporator's air source is the passenger compartment exhaust air. This invention employs a more optimized configuration design based on the original vehicle configuration and characteristics, effectively leveraging the system's energy-saving potential to improve the problem of reduced vehicle driving range.

Description

Technical Field

[0001] This invention belongs to the field of waste heat recovery technology, specifically relating to a thermal management system and control method for waste heat recovery from fresh air in electric vehicles. Background Technology

[0002] With increasing energy consumption and worsening environmental problems, countries worldwide are vigorously promoting the development and utilization of clean energy, and many major automakers have gradually reduced their R&D investment in gasoline-powered vehicles. The performance of key components in electric vehicles is closely linked to the vehicle's thermal management system, making thermal management technology a core issue restricting overall vehicle performance. Air conditioning systems, used for summer cooling and winter heating, should also have defrosting and defogging functions to ensure passenger comfort. The performance of the air conditioning system directly affects the safety and passenger comfort of electric vehicles, and is crucial for the driving experience and driving range. The severe reduction in battery safety and driving range at high and low temperatures is a significant problem hindering the rapid development of electric vehicles.

[0003] Currently, most traditional thermal management systems employ distributed or semi-integrated control systems that combine air conditioning and batteries. These systems have relatively simple loop systems and control components, lacking the ability to coordinate the entire vehicle's thermal management system and thus failing to meet the comprehensive utilization of system energy. Overall vehicle performance still has room for optimization. To address this issue, it is necessary to couple the various thermal management systems functionally and structurally to form an integrated vehicle thermal management system. This is particularly important for low-temperature vehicle thermal management systems, comprehensively utilizing the potential waste heat of the thermal management system to improve energy efficiency, thereby increasing the vehicle's driving range and alleviating problems such as low efficiency and frosting in low-temperature heat pump systems. Furthermore, an efficient and safe vehicle thermal management system is crucial for ensuring the performance of the vehicle's "three electrics" (battery, motor, and electronic control system), passenger cabin comfort, the lifespan of key components, and overall vehicle safety. Summary of the Invention

[0004] This invention aims to address the shortcomings of existing technologies by proposing a thermal management system and control method for waste heat recovery in electric vehicles. Based on the original vehicle configuration and characteristics, a more optimized configuration design is adopted, which can effectively leverage the system's energy-saving potential and improve the problem of reduced vehicle driving range.

[0005] To achieve the above objectives, the present invention provides the following solution: a thermal management control method for waste heat recovery of fresh air in electric vehicles, comprising: a compressor control strategy, an electronic expansion valve control strategy, and an electric water pump control strategy for an automotive heat pump air conditioning system.

[0006] More preferably, the compressor control strategy includes: determining the control objective and controlling the rotational speed using a PID control method;

[0007] The control objectives include:

[0008] When the crew cabin is being cooled or heated, the control target is the outlet temperature of the evaporator or heater core;

[0009] When the battery is cooling or refrigerating, the control target is the temperature of the inlet coolant in the battery fluid circuit;

[0010] When the crew compartment and battery are heated simultaneously, the control target is the coolant temperature;

[0011] The PID control method includes:

[0012]

[0013] In the formula, v represents the control output; u represents the difference between the actual value and the target value; K p K i K d These represent the proportional coefficient, integral coefficient, and differential coefficient, respectively.

[0014] More preferably, the electronic expansion valve control strategy includes: determining the control target and controlling the rotational speed using a PID control method;

[0015] The control objectives include:

[0016] When the crew compartment is cooled, the control target is the refrigerant superheat at the evaporator outlet;

[0017] When the battery is used for cooling, the control target is the superheat at the refrigerant side outlet of the plate heat exchanger Chiller.

[0018] When the crew compartment and the battery are cooled simultaneously, the control target is first the superheat of the Chiller refrigerant outlet; when the superheat is greater than 8°C, the control target is the battery coolant inlet temperature.

[0019] The PID control method in the electronic expansion valve control strategy is the same as the PID control method in the compressor control strategy.

[0020] More preferably, the electric water pump includes an electric water pump with a battery fluid circuit and an electric water pump with a heater core circuit.

[0021] The electric water pump control strategy includes:

[0022] In cooling mode, the electric water pump in the heating core circuit does not work. When the average battery temperature is greater than 28°C, the electric water pump in the battery liquid circuit starts to work at a fixed speed.

[0023] During heating operation, the electric water pump in the heater core circuit operates at a high speed when the outlet air temperature is below 38°C, and at a low speed when the outlet air temperature is above 38°C. When the average battery temperature is below 22°C, the electric water pump in the battery fluid circuit operates at a high speed, and at a low speed when the temperature reaches 22°C.

[0024] More preferably, model predictive control is used to optimize the compressor control strategy and the electronic expansion valve control strategy;

[0025] The optimization method includes:

[0026] The MPC controller performs state-space modeling of the heat pump air conditioning system to obtain a predictive model; it then performs optimization on the control model to obtain the optimal control sequence for the compressor speed at the current moment; the speed is input into the heat pump air conditioning system to obtain the evaporator outlet air temperature, and the air temperature value is returned to the MPC controller for optimization to obtain the speed control sequence for future time periods.

[0027] More preferably, the prediction model includes:

[0028]

[0029] In the formula, Let represent the state variable; x represents the initial condition of the state variable; u represents the input variable; y represents the output variable; a i The parameter representing the state matrix A; b i The parameter representing the input matrix B;

[0030] The objective function is:

[0031]

[0032] In the formula, k and k+1 represent the current time k and the future time k+1, respectively; p represents the prediction time domain; m represents the control time domain; w() represents the desired output value; Δu(k) represents the change in the control quantity; qi represents the weight matrix of the change in tracking error; r j A weight matrix representing the changes in the control quantity; This represents the predicted output value.

[0033] The constraints are:

[0034] 500≤N comp ≤5000,

[0035] -50≤ΔN comp ≤50,

[0036] In the formula, N compIndicates compressor speed; ΔN comp This indicates the rate of change of compressor speed.

[0037] The present invention also provides a fresh air waste heat recovery thermal management system for electric vehicles. The system does not change the original system circuit structure of the vehicle, and delivers the exhaust air from the passenger compartment to the condenser to mix the exhaust air with the outside air intake.

[0038] Alternatively, the system may add a gas heat exchanger component to the HVAC assembly, which exchanges heat between the passenger compartment exhaust air and the blower intake air through an internal heat exchange filter.

[0039] Alternatively, the system can add a small evaporator to the circuit of the vehicle's existing heat pump air conditioning system, with the evaporator located between the compressor and the condenser; the air source for the evaporator comes from the exhaust air from the passenger compartment.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] Based on the analysis of waste heat utilization in fresh air systems, this invention proposes three improved configuration schemes with waste heat recovery and utilization functions in fresh air systems, and then designs control strategies for the system and key components based on the configurations. For the three improved schemes, the optimization effect on system performance during high-temperature cooling and low-temperature heating is analyzed, and the specific impact of key factors of heat pump air conditioning systems on the optimization effect of each scheme is studied, providing a foundation for subsequent heat pump system control optimization. Attached Figure Description

[0042] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a block diagram of the PID control logic in an embodiment of the present invention;

[0044] Figure 2 This is a block diagram illustrating the model predictive control principle of an embodiment of the present invention.

[0045] Figure 3 This is a schematic diagram of the configuration of the first system scheme of the present invention;

[0046] Figure 4 This is a schematic diagram of the configuration of the second system scheme of the present invention;

[0047] Figure 5 This is a schematic diagram of the configuration of the system scheme three of the present invention. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 are within the scope of protection of the present invention.

[0049] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] Example 1:

[0051] This embodiment provides a thermal management control method for waste heat recovery from fresh air in electric vehicles. First, the control modes are divided:

[0052] In cooling mode, first confirm the ambient temperature and air conditioning system operation. When the passenger compartment temperature is above 25°C and the battery temperature is below or equal to 28°C, the air conditioning system cools the passenger compartment only, and the electronic expansion valve of the Chiller branch is closed. At this time, if the ambient temperature is higher than the passenger compartment temperature, exhaust air recirculation is activated to lower the intake air temperature; if the ambient temperature is lower than the passenger compartment temperature, the exhaust air is discharged into the outside environment without being recycled. When the passenger compartment temperature is below 25°C and the battery temperature is above 38°C, the active battery cooling mode is activated. In this mode, the air conditioning system cools the battery circuit coolant via the Chiller. If the ambient temperature is higher than the passenger compartment temperature, passenger compartment exhaust air is supplied to the air conditioning system to lower the intake air temperature; if the passenger compartment temperature is higher than the ambient temperature, exhaust air utilization is shut off. When the passenger compartment temperature is above 25°C and the battery temperature is above 38°C, both the passenger compartment and the battery are cooled simultaneously, and exhaust air utilization is not activated.

[0053] During heating operation, the ambient temperature is first assessed. When the ambient temperature is below -15°C, the heat pump system in this embodiment uses R134a as the working fluid. At this temperature, the heat pump system's efficiency is low and it cannot provide sufficient heat. Therefore, the water-cooled PTC heater is activated, the air conditioning system is off, and exhaust gases are released into the environment. When the passenger compartment temperature is below 16°C and the battery temperature is above 22°C, the heat pump air conditioning system heats the passenger compartment independently. The battery-heater core circuit three-way valve on the battery side is closed, the refrigerant two-way valve is open, and the evaporator branch electronic expansion valve is closed. When the passenger compartment temperature is higher than the ambient temperature, exhaust waste heat recovery is activated to increase the intake air temperature. When the passenger compartment temperature is above 22°C and the battery temperature is below 22°C, the battery-heater core circuit three-way valve on the battery side is open. The heat pump air conditioning system heats the coolant through the water-cooled condenser to heat the battery. Similarly, when the passenger compartment temperature is higher than the ambient temperature, exhaust waste heat recovery is activated.

[0054] In this embodiment, the main controllable components of the thermal management system include: the compressor and electronic expansion valve of the heat pump air conditioning system, as well as the electric water pump in the battery fluid circuit and the electric water pump in the heater core circuit; wherein the compressor and electric water pump are mainly controlled by their speed, and the electronic expansion valve is mainly controlled by its opening degree. Therefore, the control method in this embodiment mainly includes: compressor control strategy, electronic expansion valve control strategy, and electric water pump control strategy of the automotive heat pump air conditioning system.

[0055] (1) Compressor control strategy

[0056] The compressor is the power source of the heat pump air conditioning system, and its control effect directly affects the comfort of the passenger compartment and the operating temperature of the battery. Therefore, it is necessary to determine the control targets for different operating conditions and modes. When the passenger compartment is cooling or heating, the control target is the outlet temperature of the evaporator or heater core; when the battery is cooling or operating, the control target is the inlet coolant temperature of the battery fluid circuit; when both the passenger compartment and the battery are heating simultaneously, the control target is the coolant temperature.

[0057] Once the compressor control objective is determined, the PID control method is used to control its speed.

[0058] The control equations for the PID control method are as follows:

[0059]

[0060] In the formula, v represents the control output; u represents the difference between the actual value and the target value; K p K i K d These represent the proportional coefficient, integral coefficient, and differential coefficient, respectively.

[0061] PID control logic as follows Figure 1As shown, r(t) represents the input signal; e(t) represents the deviation signal; u(t) represents the control signal; and y(t) represents the output signal of the controlled object.

[0062] (2) Electronic expansion valve control strategy

[0063] Heat pump air conditioning systems regulate refrigerant flow by controlling the opening of the electronic expansion valve to improve system performance. The electronic expansion valve opening is generally controlled based on the superheat of the refrigerant at the evaporator outlet; maintaining a certain level of superheat in the refrigerant helps prevent liquid slugging in the compressor.

[0064] When the crew compartment is cooled, the control target is the refrigerant superheat at the evaporator outlet; when the battery is cooled, the control target is the refrigerant superheat at the Chiller refrigerant side outlet of the plate heat exchanger; when the crew compartment and the battery are cooled simultaneously, the Chiller refrigerant side outlet superheat is the primary control target; when the superheat is greater than 8°C, the control target is the battery coolant inlet temperature.

[0065] The PID control method in the electronic expansion valve control strategy is the same as that in the compressor control strategy.

[0066] (3) Electric water pump control strategy

[0067] The speed of the water pump controls the flow rate of the coolant circulation circuit, thus directly affecting the heat exchange effect of the coolant. In this embodiment, the electric water pump includes an electric water pump for the battery fluid circuit and an electric water pump for the heater core circuit.

[0068] The electric water pump speed control adopts a logic threshold control method. In cooling mode, the electric water pump in the heating core circuit does not work. When the average battery temperature is greater than 28℃, the electric water pump in the battery fluid circuit starts working at a fixed speed. In heating mode, the electric water pump in the heating core circuit operates at a high speed based on the outlet air temperature of the heating core. When the outlet air temperature is below 38℃, the electric water pump operates at a high speed. When it is above 38℃, it slows down and switches to a low speed. When the average battery temperature is below 22℃, the electric water pump in the battery fluid circuit operates at a high speed. After the temperature reaches 22℃, it switches to a low speed.

[0069] Based on the aforementioned control strategies, this embodiment employs model predictive control (MPC) to optimize the compressor control strategy and the electronic expansion valve control strategy. Specifically, MPC is used to control the compressor speed, the electronic expansion valve, and the condenser fan. MPC is a model-based multivariable control strategy that comprises three key components: a predictive model, rolling optimization, and feedback correction. Its core principle is to reduce system errors through repeated rolling optimization within a finite time domain, thereby achieving the desired control effect.

[0070] During the control process, there exists a desired reference trajectory. The controller, combining current measurements and a prediction model, predicts the system's output over a future period, where the time domain [k, k+Np] is called the prediction time domain. Subsequently, by solving an optimization problem that satisfies the objective function and various constraints, a series of control sequences are obtained within the control time domain. The first element of this control sequence is used as the actual control variable for the controlled object. This process is repeated in the next sampling period, thereby continuously completing the constrained optimization problem and achieving continuous control of the controlled object.

[0071] Model predictive control principle block diagram as follows Figure 2 As shown, it includes three modules: an MPC controller, a controlled object, and a state estimator. In this embodiment, the heat pump air conditioning system is taken as the controlled object. State-space models are created for both the refrigeration and heating cycles, and these models are used as prediction models. Then, optimization is performed on these models to obtain the optimal control sequence for the compressor speed at the current moment. After inputting the compressor control speed into the thermal management system's calculation model, the simulated value of the evaporator outlet air temperature is returned. A state estimator is not needed here. The simulated value is then returned to the MPC controller for optimization to obtain the control sequence for future time periods, and this process is continuously repeated online.

[0072] In this embodiment, the MPC controller is constructed using state-space equations, and the linear state-space equation system is expressed as follows:

[0073]

[0074] y = Cx + Du

[0075] In the formula, denoted by ; x represents the initial condition of the state variable; u represents the input variable; y represents the output variable; A represents the state matrix; B represents the input matrix; C represents the output matrix; and D represents the transfer matrix of the input.

[0076] When modeling the state-space equations of a heat pump air conditioning system, there are generally two approaches: gray-box models and black-box models. Gray-box models are more complex, modeling the air conditioning system based on mass and energy conservation equations. The modeling process requires deriving parameters for each component. Because the air conditioning system itself has numerous parameters, the source and accuracy of these parameters cannot guarantee that the state-space model can accurately reflect the performance characteristics of the air conditioning system. Furthermore, some parameters in the model need to be identified through experimental data. This embodiment uses a data-driven black-box model to model the state-space equations of the air conditioning system. The data comes from static experiments, the experimental process of which includes the system operating until it reaches a steady state, and can reflect the characteristics of the heat pump air conditioning system to a certain extent.

[0077] State matrix A and input matrix B are defined as unknown parameters, and output matrix C is the identity matrix. Then, the input and output variables and state variables of the state-space equation are selected. Through experimental data-driven parameter identification methods such as least squares, the parameters of the corresponding matrices are obtained.

[0078] The main parameters that change during the operation of a heat pump air conditioning system are temperature and pressure. Therefore, the selection of state variables mainly refers to the temperature and pressure of each major component. Based on the data measured in the experiment, the input variables are selected from the main control variables in the air conditioning system, such as compressor speed, electronic expansion valve opening, blower air volume, condenser air volume, ambient temperature, and vehicle speed. Based on experience, this embodiment adopts a state-space equation with 3 state variables and 3 input variables as the system prediction model. The state variables are the evaporator outlet air temperature and the system high and low pressures. The input variables are the compressor speed, expansion valve opening, and condenser air volume. The output matrix is ​​a unit matrix used to output the system state variables. The prediction model includes:

[0079]

[0080] In the formula, a i The parameter representing the state matrix A; b i The parameter represents the input matrix B.

[0081] Based on high-temperature refrigeration test data, the unknown parameters of matrices A and B in the state-space equations are identified. The input variables are compressor speed, electronic expansion valve opening, and condenser airflow, while the output variables are evaporator outlet air temperature and system high and low pressure. The parameter identification tool uses the Trust-Region-Reflective algorithm from the least squares method as the optimization algorithm, and identifies parameters of the state-space equations based on data collected from the thermal management system test; this embodiment adopts this approach.

[0082] MPC needs to determine m control increments Δu(k), ..., Δu(k-m+1) starting from each control time k, such that the predicted output value of the controlled object at p future times under its action can be as close as possible to the desired output value w(k+1), i = 1, ..., p, while ensuring that the change of Δu is not too drastic. The objective function is:

[0083]

[0084] In the formula, k and k+1 represent the current time k and the future time k+1, respectively; p represents the prediction time domain; m represents the control time domain; w() represents the desired output value; Δu(k) represents the change in the control quantity; qi represents the weight matrix of the change in tracking error; r j A weight matrix representing the changes in the control quantity; This represents the predicted output value.

[0085] The MPC control output is the compressor speed. The range and rate of change of the control output need to be determined based on actual conditions. Therefore, the following constraints are determined based on the actual compressor parameters, and all constraints are hard constraints. The constraints are:

[0086] 500≤N comp ≤5000,

[0087] -50≤ΔN comp ≤50,

[0088] In the formula, N comp Indicates compressor speed; ΔN comp This indicates the rate of change of compressor speed.

[0089] Example 2:

[0090] This embodiment provides three implementation schemes based on the control method in Embodiment 1. Since the components that mainly handle the input air volume in a heat pump air conditioning system include the evaporator and the condenser, the utilization of the passenger compartment exhaust air can be optimized and improved by optimizing the air supply components of these two components.

[0091] System solution as follows Figure 3 As shown, the heat pump air conditioning system still adopts the three-heat exchanger scheme without changing the original system's loop structure. The waste heat recovery and utilization scheme is to send the passenger cabin exhaust air to the condenser, so that the exhaust air is mixed with the outside air intake, thereby improving the heat exchange effect of the condenser.

[0092] During high-temperature cooling, the refrigerant in the condenser of the air conditioning system condenses and releases heat. The exhaust air temperature in the passenger compartment is lower than the ambient temperature. After the exhaust air is delivered to the condenser and mixed with the outside air, the condenser intake air temperature is reduced, thereby increasing the heat exchange of the condenser. Under the same target control temperature, the energy consumption of the compressor can be reduced.

[0093] In low-temperature environments, the condenser in the circuit acts as an evaporator, absorbing heat from the external environment. However, when the ambient temperature drops below -10°C, the efficiency of the heat pump air conditioner decreases significantly, and the condenser is prone to frosting, making heat exchange difficult. Therefore, in extremely low-temperature conditions, PTC (Potential Thermal Capacitor) is typically activated for active heating. After heating is activated, the passenger compartment temperature rises, and the exhaust air delivered to the condenser can perform defrosting. When the heat pump system starts operating later, the passenger compartment exhaust air can mix with the outside intake air, increasing the condenser intake air temperature and thus improving the refrigerant heat exchange effect, absorbing more heat.

[0094] System Solution Two Figure 4As shown, a gas heat exchanger component is added to the HVAC assembly. The function of this component is to exchange heat between the passenger compartment exhaust air and the blower intake air through an internal heat exchange filter, without directly mixing the two, thereby ensuring the air quality of the passenger compartment. The passenger compartment exhaust air is discharged into the outside environment after passing through the gas heat exchanger.

[0095] When cooling at high temperatures, the air conditioning system rapidly cools the passenger compartment. The refrigerant in the evaporator evaporates and absorbs heat from the blower's airflow. At this time, sending the passenger compartment exhaust air to the gas heat exchanger can cool the blower's airflow in advance, thereby reducing the evaporator's heat exchange power and alleviating system energy consumption.

[0096] In low-temperature environments, the heating of the passenger compartment is not directly provided by the refrigerant. Instead, the coolant is heated by the refrigerant or PTC and then delivered to the passenger compartment through the heater core. Once the temperature of the passenger compartment has risen to a certain extent, the passenger compartment exhaust air is delivered to the gas heat exchanger, which can preheat the air intake of the blower, increase the air intake temperature of the heater core, and reduce the heating load of the heater core. The passenger compartment exhaust air, after recovering heat through the heat exchanger, is then discharged into the outside environment.

[0097] System Solution 3 Figure 5 As shown, a small evaporator is added to the circuit based on the original heat pump air conditioning system. It is located between the compressor and the condenser, and the air source for the evaporator comes from the exhaust air of the passenger compartment.

[0098] In high-temperature environments, the evaporator can act as a condenser to condense and release heat. When the system has high heat dissipation requirements, the evaporator can be opened for heat exchange in the passenger compartment exhaust. In other cases, since the heat exchange effect of the original circuit condenser is good, and considering the overall system performance, the passenger compartment exhaust recovery is not activated.

[0099] In low-temperature environments, the operation is similar to that of Scheme 1, but the loop structure of Scheme 3 is easier to implement. When the heat pump air conditioning system starts working, the temperature of the passenger compartment rises. At this time, the passenger compartment exhaust air is sent to the evaporator so that the refrigerant absorbs the heat, thereby improving the overall energy utilization rate of the system. After being recovered, the passenger compartment exhaust air will be discharged into the outside environment to ensure the air quality of the passenger compartment.

[0100] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for heat management and control of waste heat recovery from fresh air in electric vehicles, characterized in that, include: Compressor control strategy, electronic expansion valve control strategy, and electric water pump control strategy of automotive heat pump air conditioning system; The compressor control strategy includes: determining the control objective and controlling the speed using a PID control method; The control objectives include: When the crew cabin is being cooled or heated, the control target is the outlet temperature of the evaporator or heater core; When the battery is cooling or refrigerating, the control target is the temperature of the inlet coolant in the battery fluid circuit; When the crew compartment and battery are heated simultaneously, the control target is the coolant temperature; The PID control method includes: ， In the formula, v represents the control output; u This represents the difference between the actual value and the target value. K p , K i , K d These represent the proportional coefficient, integral coefficient, and differential coefficient, respectively. The electronic expansion valve control strategy includes: determining the control target and controlling the rotational speed using a PID control method; The control objectives include: When the crew compartment is cooled, the control target is the refrigerant superheat at the evaporator outlet; When the battery is used for cooling, the control target is the superheat at the refrigerant side outlet of the plate heat exchanger Chiller. When the crew compartment and the battery are cooled simultaneously, the control target is first the superheat of the Chiller refrigerant outlet; when the superheat is greater than 8°C, the control target is the battery coolant inlet temperature. The PID control method in the electronic expansion valve control strategy is the same as the PID control method in the compressor control strategy. Electric water pumps include electric water pumps with battery fluid circuits and electric water pumps with heating core circuits. The electric water pump control strategy includes: In cooling mode, the electric water pump in the heating core circuit does not work. When the average battery temperature is greater than 28°C, the electric water pump in the battery liquid circuit starts to work at a fixed speed. During heating operation, the electric water pump in the heater core circuit operates at a high speed when the outlet air temperature is below 38°C, and at a low speed when the outlet air temperature is above 38°C. When the average battery temperature is below 22°C, the electric water pump in the battery fluid circuit operates at a high speed, and at a low speed when the temperature reaches 22°C. The process of applying the waste heat recovery thermal management control method for fresh air in electric vehicles includes: without changing the original system circuit structure of the vehicle, delivering the exhaust air from the passenger compartment to the condenser, and mixing the exhaust air with the incoming air from the outside; Alternatively, a gas heat exchanger component can be added to the HVAC assembly, which exchanges heat between the passenger compartment exhaust air and the blower intake air through an internal heat exchange filter. Alternatively, a small evaporator can be added to the circuit of the car's existing heat pump air conditioning system. The evaporator is located between the compressor and the condenser, and the air source for the evaporator comes from the exhaust air from the passenger compartment.

2. The method for heat management and control of waste heat recovery in electric vehicles according to claim 1, characterized in that, The compressor control strategy and the electronic expansion valve control strategy are optimized using model predictive control methods. The optimization method includes: The MPC controller performs state-space modeling of the heat pump air conditioning system to obtain a prediction model; it then performs optimization on the prediction model to obtain the optimal control sequence of compressor speed at the current moment; the speed is input into the heat pump air conditioning system to obtain the evaporator outlet air temperature, and the air temperature value is returned to the MPC controller for optimization to obtain the speed control sequence for future time periods.

3. The method for heat management and control of waste heat recovery in electric vehicles according to claim 2, characterized in that, The prediction model includes: ， In the formula, Represents state variables; x The initial conditions of the state variables; u Indicates input variables; y Indicates the output variable; a i State matrix A Parameters; b i Represents the input matrix B Parameters; The objective function is: ， In the formula, k , k + i They represent the current k Time and Future k + i time; p Indicates the prediction time domain; m Indicates control over the time domain; w ( ) represents the expected output value; Δ u ( k () indicates the change in the control quantity; q i The weight matrix represents the change in tracking error; r j A weight matrix representing the changes in the control quantity; ( ) represents the predicted output value; The constraints are: ， ， In the formula, N comp Indicates the compressor speed; This indicates the rate of change of compressor speed.

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