Fuel cell thermal management control method in waste heat recovery mode

Abstract

The invention discloses a fuel cell thermal management control method in a waste heat recovery mode, and relates to the field of fuel cell thermal management, and the fuel cell thermal management control method in the waste heat recovery mode comprises the following steps: step 1, based on a fuel cell thermal management control system, performing thermal management on a fuel cell; fuel cell waste heat is used for transmitting heat to a passenger compartment heat management loop through a heat exchanger, and a heat pump is used as a heat source for supplying heat to a passenger compartment to serve as a fuel cell heat management control model; 2, judging whether the fuel cell thermal management control system is in a heat dissipation mode or a heating mode based on the fuel cell thermal management model; compared with the prior art, the method has the beneficial effects that the thermal management control accuracy of the fuel cell is improved; through combination control of feedforward and feedback, the control difficulty is reduced, and the cost is relatively low; the feed-forward controller is optimally designed, so that the optimal energy consumption of the water pump and the cooling fan is realized, and the economical efficiency is high.

Description

Technical Field

[0001] The present invention relates to the field of fuel cell thermal management, and in particular to a fuel cell thermal management control method in a waste heat recovery mode. Background Art

[0002] During the electrochemical reaction process of proton exchange membrane fuel cells, a large amount of heat is often generated. In existing proton exchange membrane fuel cell vehicle technology, the temperature of the fuel cell directly affects its performance. Too high a temperature will cause the proton exchange membrane to dehydrate and cause irreversible performance loss. Too low a temperature will affect its efficiency. Therefore, the thermal management of the fuel cell is crucial. However, the electrochemical reaction efficiency of proton exchange membrane fuel cells is between 40% and 60%, resulting in a large amount of heat energy generation. At this stage, how to utilize the waste heat of fuel cells is of great research significance. Under low ambient temperatures, the waste heat of fuel cells is usually used to heat up the vehicle cabin to improve its economic benefits. In the control process of fuel cell thermal management, due to certain disturbances in waste heat recovery, the control difficulty of the fuel cell is increased.

[0003] In the existing technology, Jiang (Jiang H, Xu L, Li JQ, et al. Design and Control of Thermal Management System for the Fuel Cell Vehicle in Low-Temperature Environment [C] / / WCX SAE World Congress Experience. 2020. DOI: 10.4271 / 2020-01-0851.) et al. proposed the design of a thermal management coupling system in which the waste heat of the fuel cell is used to heat the passenger compartment in a low-temperature environment. The sliding film control is used to control the heat exchanged by the heat exchanger to a stable value, thereby realizing independent thermal management control of the fuel cell system and the passenger compartment.

[0004] In the fuel cell thermal management system, there is a disturbance in the heat exchanger. The heat control of the heat exchanger designed by Jiang et al. may cause excessive heat loss in the performance of the fuel cell, and too low heat cannot achieve the optimization of energy consumption, which needs to be improved. Summary of the invention

[0005] The object of the present invention is to provide a fuel cell thermal management control method in a waste heat recovery mode to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A fuel cell thermal management control method in a waste heat recovery mode comprises the following steps:

[0008] Step 1, based on the fuel cell thermal management control system, using the waste heat of the fuel cell to transfer heat to the passenger compartment thermal management loop through a heat exchanger, and using a heat pump as a heat source to heat the passenger compartment as a fuel cell thermal management control model;

[0009] Step 2, judging whether the fuel cell thermal management control system is in a heat dissipation mode or a heating mode based on the fuel cell thermal management model;

[0010] Step 3, in the heat dissipation mode, design an optimized feedforward MAP controller to control the working state of the fuel cell thermal management control system, and perform control correction through PID feedback adjustment.

[0011] As a further solution of the present invention: in step 1, the fuel cell thermal management control model includes a passenger compartment thermal management loop and a fuel cell thermal management loop;

[0012] The passenger compartment thermal management circuit includes an expansion valve, a heat exchanger, a compressor, and an evaporator. The waste heat of the fuel cell is transferred to the passenger compartment thermal management circuit through the heat exchanger. In a low-temperature environment, the heat pump is used as an auxiliary heat source. After the compressor further compresses and heats the heat, the resulting refrigerant (R134a) is used to heat the passenger compartment through the evaporator.

[0013] The fuel cell thermal management circuit includes a fuel cell, an electronic thermostat, a radiator, a water tank, and an electronic water pump. The fuel cell thermal management circuit is divided into a large circuit and a small circuit. The large circuit is composed of a fuel cell, an electronic water pump, a water tank, and a radiator, and dissipates heat for the fuel cell system, which is a heat dissipation mode; the small circuit is composed of a fuel cell, an electronic water pump, a water tank, and an electronic thermostat, and maintains the temperature of the fuel cell system, which is a heating mode.

[0014] As a further solution of the present invention: in step 2, the current fuel cell outlet temperature T is obtained. cell , determine the first control input signal, and obtain the optimal operating temperature T of the fuel cell 1 , determine T 1 is the second control input signal; when T cell Less than T 1 The fuel cell thermal management system is in heating mode. cell Greater than T 1 The fuel cell thermal management system is in heat dissipation mode.

[0015] As a further solution of the present invention: step 3 comprises:

[0016] Step 31: Under the heat dissipation mode, obtain the current fuel cell heat dissipation demand Q req, according to the heat dissipation requirement, determine the fuel cell output current I as the third control input signal; obtain the actual ambient temperature T amb , determined as the fourth control input signal; obtaining the heat Q currently exchanged by the heat exchanger exc , determined as the fifth control input signal;

[0017] Step 32: according to the currently acquired heat dissipation demand Q req 、Ambient temperature T amb , the disturbance heat Q transferred by the heat exchanger exc , the extended state observer (ESO) is used to estimate the disturbance caused by the heat exchanger, and an optimized feedforward MAP controller is designed to control the working state of the fuel cell thermal management control system;

[0018] Step 33, design PID feedback regulation to perform control correction, control the first control output signal to control the water pump speed n pump , control the second control output signal to control the speed of the fan fan , PID feedback regulation and MAP controller together form a closed-loop optimized feedforward MAP-PID control system.

[0019] As a further solution of the present invention: In step 31, the heat dissipation demand Q of the fuel cell req Determined by the fuel cell output current I:

[0020] Q req =N cell (E nernst -V cell )I (1);

[0021] Where: N cell is the number of cells in the fuel cell, E nernst is the theoretical thermodynamic electromotive force, V cell is the fuel cell output voltage;

[0022] In the fuel cell thermal management system, due to the presence of the disturbance Q of the heat exchanger exc , so the actual heat dissipation requirement is Q rea for:

[0023] Q rea =Q req -Q exc (2);

[0024] As a further solution of the present invention: in step 32, according to the actual heat dissipation demand Q rea And the ambient temperature T amb Designed a MAP controller, which is a MAP table determined based on the principle of optimizing the energy consumption of the electronic water pump and fan;

[0025] The ambient temperature corrects the actual heat dissipation requirement:

[0026]

[0027] Where: Q s is the actual heat dissipation demand correction, ΔT a_s is the actual temperature difference between the air side and the cooling side of the radiator after correction, ΔT a_rea The temperature difference between the current radiator air side and cooling side is calibrated;

[0028] The cooling power of the radiator is Q ra :

[0029] Q ra =L ra ·C air ΔT ra (4);

[0030] Where: L ra is the air flow rate entering the radiator, C air is the specific heat capacity of air, ΔT ra It is the temperature difference between the front and rear ends of the radiator when the coolant flows through it;

[0031] It can be obtained that the optimal temperature of the coolant at the outlet of the fuel cell stack is T full It can be expressed as:

[0032]

[0033] As a further solution of the present invention: in step 32, an extended state observer (ESO) is used to estimate and compensate for disturbances of the heat exchanger, thereby improving the accuracy and robustness of the model;

[0034] Formula (5) can be organized into the following form:

[0035]

[0036] y=c(6);

[0037] Where c = T full , u=I, δ=f+d, is the disturbance of the heat exchanger of the system, δ is called the total disturbance;

[0038] Expand δ into a state of the system, so the original system can be reconstructed as:

[0039]

[0040] y=x 1 (7);

[0041] The specific form of the extended state observer is:

[0042]

[0043] In the formula, z 1 , z 2 The system state x 1 , x 2 The estimated value of β 1 , β 2 is the observer gain;

[0044] Observation error:

[0045]

[0046] Written in matrix form:

[0047]

[0048] Where E is the identity matrix, C =

[10] ;

[0049] Select appropriate β so that the characteristic root of the matrix (A-βC) has a negative real part, so that the error e converges to 0 in a finite time;

[0050] The heat exchanger disturbance of the system is obtained:

[0051] d=z 2 -f (13);

[0052] Substituting the above equation into formula (6) and the value of d, the heat exchange capacity can be obtained:

[0053]

[0054] The heat exchanger disturbance is the fuel cell system loss, which is a negative value here.

[0055] As a further solution of the present invention: in step 32, the MAP controller is optimized, and the power consumption of the electronic water pump P pump for:

[0056]

[0057] Where: q pump is the coolant flow through the electronic water pump, ΔP is the pressure difference between the two ends of the electronic water pump, η pump is the efficiency of the electronic water pump;

[0058] The power consumption of the fan is P fan for:

[0059]

[0060] Where: ΔP fan is the air flow resistance, V fan is the air volume flow rate;

[0061] Therefore, the total power consumption of the fuel cell heat dissipation P total for:

[0062] P total =P pump +P fan (17);

[0063] Considering the economic benefits and the maximum reduction of power consumption, the optimal response problem is expressed as:

[0064]

[0065] x∈X,u∈U(20);

[0066] x 1 (t 0 )=P 0 ,x 1 (t f )=P f (twenty one);

[0067] Where: f(x,u,t) is the system transition equation, x=[P total T full ] is the state variable of the system, u=[n pump n fan ] is the control variable of the system, which is realized by changing the pump speed n in real time. pump , and fan speed n fan Change the real-time pump and fan power, P 0 , P f are the total power consumption values ​​from the starting point to the ending point respectively;

[0068] X=[X 1 X 2 ],U=[U 1 U 2 ] are the boundary conditions of the system transition variables and control variables, respectively, as follows:

[0069]

[0070] Where: P pump,min , P pump,max is the minimum and maximum power consumption of the electronic water pump, P fan,min , P fan,max is the minimum and maximum power consumption of the fan; T full,min , T full,maxThe lowest and highest temperatures of the fuel cell cooling water outlet; n pump,min , n pump,max is the minimum and maximum speed of the electronic water pump, n fan,min , n fan,max The minimum and maximum speed of the fan.

[0071] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention adopts a genetic algorithm to optimize the power consumption of different combinations of control variables, and obtains the optimal operating points of the electronic water pump and the fan under different heat dissipation requirements based on the boundary constraints and the optimization of power consumption, thereby obtaining a MAP curve diagram of the electronic water pump and fan speed corresponding to the actual heat dissipation requirements after optimization, thereby improving the accuracy of fuel cell thermal management control; through the combination of feedforward and feedback control, the control difficulty is reduced and the cost is low; the feedforward controller is optimized to achieve optimal energy consumption of the water pump and the cooling fan, and high economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 Schematic diagram of the fuel cell thermal management control model.

[0073] Figure 2 This is a schematic diagram of the working mode judgment of the fuel cell thermal management control model.

[0074] Figure 3 MAP-PID control block diagram for optimized feedforward. DETAILED DESCRIPTION

[0075] The technical solutions 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, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0076] See also Figure 1 , a fuel cell thermal management control method in a waste heat recovery mode, comprising the following steps:

[0077] Step 1, based on the fuel cell thermal management control system, using the waste heat of the fuel cell to transfer heat to the passenger compartment thermal management loop through a heat exchanger, and using a heat pump as a heat source to heat the passenger compartment as a fuel cell thermal management control model;

[0078] Step 2, judging whether the fuel cell thermal management control system is in a heat dissipation mode or a heating mode based on the fuel cell thermal management model;

[0079] Step 3, in the heat dissipation mode, design an optimized feedforward MAP controller to control the working state of the fuel cell thermal management control system, and perform control correction through PID feedback adjustment.

[0080] In a specific embodiment: In the existing technology, Jiang (Jiang H, Xu L, Li JQ, et al. Design and Control of Thermal Management System for the Fuel Cell Vehicle in Low-Temperature Environment [C] / / WCX SAE World Congress Experience. 2020. DOI: 10.4271 / 2020-01-0851.) et al. proposed the design of a thermal management coupling system in which the waste heat of the fuel cell is used to heat the passenger compartment in a low-temperature environment, and the sliding film control is used to control the heat exchanged by the heat exchanger to a stable value, thereby realizing independent thermal management control of the fuel cell system and the passenger compartment.

[0081] Wang (Wang Yuteng. Energy-saving control of integrated thermal management system of fuel cell vehicles [D]. Jiangsu University, 2023. DOI: 10.27170 / d.cnki.gjsuu.2022.002359.) Considering the influence of the heat exchange disturbance of the liquid-liquid exchanger in the waste heat utilization subsystem on the precise control of the operating temperature of the fuel cell, the heat exchange disturbance of the liquid-liquid exchanger is added to the constraint conditions, and the optimal operating temperature following predictive controller of the cooling subsystem is designed to improve the accuracy of thermal management control.

[0082] In the fuel cell thermal management system, there are disturbances in the heat exchanger. The heat control of the heat exchanger designed by Jiang et al. may cause excessive heat loss in the performance of the fuel cell, and too little heat cannot achieve the optimization of energy consumption. Wang designed a cooling subsystem optimal operating temperature following prediction controller by adding constraints on the heat exchanger disturbance, but real-time prediction has high requirements on the controller hardware and software and is costly.

[0083] Since the thermal management system is a complex control system with nonlinearity, strong coupling, multiple inputs and multiple outputs and certain hysteresis, the present invention provides a fuel cell thermal management control method in a waste heat recovery mode, taking into account the disturbance of the heat exchanger without reducing the performance of the fuel cell and achieving energy consumption optimization. The advantage of this method is that the heat generation of the fuel cell can be predicted in real time through the feedforward controller, and the water pump and fan can be decoupled. Considering the disturbance factor of the heat exchanger, this paper designs an optimized feedforward MAP controller to improve the control accuracy of the fuel cell thermal management temperature and optimize the energy consumption.

[0084] PID regulation is an existing regulation technology, and the innovation of the present invention is to optimize the feedforward MAP controller. PID regulation is not the focus of the present invention and will not be elaborated in detail here.

[0085] In this example: See Figure 1 ,In step 1, the fuel cell thermal management control model includes a passenger compartment thermal management loop and a fuel cell thermal management loop;

[0086] The passenger compartment thermal management circuit includes an expansion valve, a heat exchanger, a compressor, and an evaporator. The waste heat of the fuel cell is transferred to the passenger compartment thermal management circuit through the heat exchanger. In a low-temperature environment, the heat pump is used as an auxiliary heat source. After the compressor further compresses and heats the heat, the resulting refrigerant (R134a) is used to heat the passenger compartment through the evaporator.

[0087] The fuel cell thermal management circuit includes a fuel cell, an electronic thermostat, a radiator, a water tank, and an electronic water pump. The fuel cell thermal management circuit is divided into a large circuit and a small circuit. The large circuit is composed of a fuel cell, an electronic water pump, a water tank, and a radiator, and dissipates heat for the fuel cell system, which is a heat dissipation mode; the small circuit is composed of a fuel cell, an electronic water pump, a water tank, and an electronic thermostat, and maintains the temperature of the fuel cell system, which is a heating mode.

[0088] In this example: See Figure 2 In step 2, obtain the current fuel cell outlet temperature T cell , determine the first control input signal, and obtain the optimal operating temperature T of the fuel cell 1 , determine T 1 is the second control input signal; when T cell Less than T 1 The fuel cell thermal management system is in heating mode. cell Greater than T 1 The fuel cell thermal management system is in heat dissipation mode.

[0089] In this example: See Figure 3 , step 3 includes:

[0090] Step 31: Under the heat dissipation mode, obtain the current fuel cell heat dissipation demand Q req , according to the heat dissipation requirement, determine the fuel cell output current I as the third control input signal; obtain the actual ambient temperature T amb , determined as the fourth control input signal; obtaining the heat Q currently exchanged by the heat exchanger exc , determined as the fifth control input signal;

[0091] Step 32: according to the currently acquired heat dissipation demand Q req 、Ambient temperature T amb, the disturbance heat Q transferred by the heat exchanger exc , the extended state observer (ESO) is used to estimate the disturbance caused by the heat exchanger, and an optimized feedforward MAP controller is designed to control the working state of the fuel cell thermal management control system;

[0092] Step 33, design PID feedback regulation to perform control correction, control the first control output signal to control the water pump speed n pump , control the second control output signal to control the speed of the fan fan , PID feedback regulation and MAP controller together form a closed-loop optimized feedforward MAP-PID control system.

[0093] In this example: See Figure 3 In step 31, the fuel cell heat dissipation requirement Q req Determined by the fuel cell output current I:

[0094] Q req =N cell (E nernst -V cell )I (1);

[0095] Where: N cell is the number of cells in the fuel cell, E nernst is the theoretical thermodynamic electromotive force, V cell is the fuel cell output voltage;

[0096] In the fuel cell thermal management system, due to the presence of the disturbance Q of the heat exchanger exc , so the actual heat dissipation requirement is Q rea for:

[0097] Q rea =Q req -Q exc (2);

[0098] In this example: See Figure 3 In step 32, the actual heat dissipation requirement Q rea And the ambient temperature T amb Designed a MAP controller, which is a MAP table determined based on the principle of optimizing the energy consumption of the electronic water pump and fan;

[0099] The ambient temperature corrects the actual heat dissipation requirement:

[0100]

[0101] Where: Q s is the actual heat dissipation demand correction, ΔT a_sis the actual temperature difference between the air side and the cooling side of the radiator after correction, ΔT a_rea The temperature difference between the current radiator air side and cooling side is calibrated;

[0102] The cooling power of the radiator is Q ra :

[0103] Q ra =L ra ·C air ΔT ra (4);

[0104] Where: L ra is the air flow rate entering the radiator, C air is the specific heat capacity of air, ΔT ra It is the temperature difference between the front and rear ends of the radiator when the coolant flows through it;

[0105] It can be obtained that the optimal temperature of the coolant at the outlet of the fuel cell stack is T full It can be expressed as:

[0106]

[0107] In this example: See Figure 3 In step 32, an extended state observer (ESO) is used to estimate and compensate for disturbances of the heat exchanger, thereby improving the accuracy and robustness of the model;

[0108] Formula (5) can be organized into the following form:

[0109]

[0110] y=x (6);

[0111] Where x = T full , u=I, δ=f+d, is the disturbance of the heat exchanger of the system, δ is called the total disturbance;

[0112] Expand δ into a state of the system, so the original system can be reconstructed as:

[0113]

[0114] y=x 1 (7);

[0115] The specific form of the extended state observer is:

[0116]

[0117] In the formula, z 1 , z 2The system state x 1 , x 2 The estimated value of β 1 , β 2 is the observer gain;

[0118] Observation error:

[0119]

[0120] Written in matrix form:

[0121]

[0122] Where E is the identity matrix, C =

[10] ;

[0123] Select appropriate β so that the characteristic root of the matrix (A-βC) has a negative real part, so that the error e converges to 0 in a finite time;

[0124] The heat exchanger disturbance of the system is obtained:

[0125] d=z 2 -f (13);

[0126] Substituting the above equation into formula (6) and the value of d, the heat exchange capacity can be obtained:

[0127]

[0128] The heat exchanger disturbance is the fuel cell system loss, which is a negative value here.

[0129] In this example: See Figure 3 In step 32, the MAP controller is optimized, and the power consumption of the electronic water pump P pump for:

[0130]

[0131] Where: q pump is the coolant flow through the electronic water pump, ΔP is the pressure difference between the two ends of the electronic water pump, η ump is the efficiency of the electronic water pump;

[0132] The power consumption of the fan is P fan for:

[0133]

[0134] Where: ΔP fan is the air flow resistance, V fan is the air volume flow rate;

[0135] Therefore, the total power consumption of the fuel cell heat dissipation P totalfor:

[0136] P total =P pump +P fan (17);

[0137] Considering the economic benefits and the maximum reduction of power consumption, the optimal response problem is expressed as:

[0138]

[0139] x∈X,u∈U(20);

[0140] x 1 (t 0 )=P 0 ,x 1 (t f )=P f (twenty one);

[0141] Where: f(x,u,t) is the system transition equation composed of equations (4) and (7), x = [P total T full ] is the state variable of the system, u=[n pump n fan ] is the control variable of the system, which is realized by changing the pump speed n in real time. pump , and fan speed n fan Change the real-time pump and fan power, P 0 , P f are the total power consumption values ​​from the starting point to the ending point respectively;

[0142] X=[X 1 X 2 ],U=[U 1 U 2 ] are the boundary conditions of the system transition variables and control variables, respectively, as follows:

[0143]

[0144] Where: P pump,min , P pump,max is the minimum and maximum power consumption of the electronic water pump, P fan,min , P fan,max is the minimum and maximum power consumption of the fan; T full,min , T full,max The lowest and highest temperatures of the fuel cell cooling water outlet; n pump,min , n pump,max is the minimum and maximum speed of the electronic water pump, n fan,min , n fan,max The minimum and maximum speed of the fan.

[0145] The present invention adopts a genetic algorithm to optimize the power consumption of different combinations of control variables u, and obtains the optimal working points of the electronic water pump and the fan under different heat dissipation requirements based on the boundary constraints and the optimization of power consumption, thereby obtaining a MAP curve of the electronic water pump and fan speeds corresponding to the actual heat dissipation requirements after optimization.

[0146] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0147] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A fuel cell thermal management control method in waste heat recovery mode, characterized in that: The fuel cell thermal management control method in the waste heat recovery mode comprises the following steps: Step 1, based on the fuel cell thermal management control system, using the waste heat of the fuel cell to transfer heat to the passenger compartment thermal management loop through a heat exchanger, and using a heat pump as a heat source to heat the passenger compartment as a fuel cell thermal management control model; Step 2, judging whether the fuel cell thermal management control system is in a heat dissipation mode or a heating mode based on the fuel cell thermal management model; Step 3, in the heat dissipation mode, design an optimized feedforward MAP controller to control the working state of the fuel cell thermal management control system, and perform control correction through PID feedback adjustment.

2. The fuel cell thermal management control method in waste heat recovery mode according to claim 1, characterized in that: In step 1, the fuel cell thermal management control model includes a passenger compartment thermal management loop and a fuel cell thermal management loop; The passenger compartment thermal management circuit includes an expansion valve, a heat exchanger, a compressor, and an evaporator. The waste heat of the fuel cell is transferred to the passenger compartment thermal management circuit through the heat exchanger. In a low-temperature environment, the heat pump is used as an auxiliary heat source. After the compressor further compresses and heats the heat, the resulting refrigerant (R134a) is used to heat the passenger compartment through the evaporator. The fuel cell thermal management circuit includes a fuel cell, an electronic thermostat, a radiator, a water tank, and an electronic water pump. The fuel cell thermal management circuit is divided into a large circuit and a small circuit. The large circuit is composed of a fuel cell, an electronic water pump, a water tank, and a radiator, and dissipates heat for the fuel cell system, which is a heat dissipation mode; the small circuit is composed of a fuel cell, an electronic water pump, a water tank, and an electronic thermostat, and maintains the temperature of the fuel cell system, which is a heating mode.

3. The fuel cell thermal management control method in waste heat recovery mode according to claim 1, characterized in that: In step 2, obtain the current fuel cell outlet temperature T cell , determine the first control input signal, obtain the optimal operating temperature T1 of the fuel cell, and determine T1 as the second control input signal; when T cell When T1 is less than the fuel cell thermal management system, the fuel cell thermal management system is in heating mode. cell When it is greater than T1, the fuel cell thermal management system is in heat dissipation mode.

4. The fuel cell thermal management control method in waste heat recovery mode according to claim 1, characterized in that: Step 3 includes: Step 31: Under the heat dissipation mode, obtain the current fuel cell heat dissipation demand Q req , according to the heat dissipation requirement, determine the fuel cell output current I as the third control input signal; obtain the actual ambient temperature T amb , determined as the fourth control input signal; obtaining the heat Q currently exchanged by the heat exchanger exc , determined as the fifth control input signal; Step 32: according to the currently acquired heat dissipation demand Q req 、Ambient temperature T amb , the disturbance heat Q transferred by the heat exchanger exc , an extended state observer (ES0) is used to estimate the disturbance caused by the heat exchanger, and an optimized feedforward MAP controller is designed to control the working state of the fuel cell thermal management control system; Step 33, design PID feedback regulation to perform control correction, control the first control output signal to control the water pump speed n pump , control the second control output signal to control the speed of the fan n fan , PID feedback regulation and MAP controller together form a closed-loop optimized feedforward MAP-PID control system.

5. The fuel cell thermal management control method in waste heat recovery mode according to claim 4, characterized in that: In step 31, the fuel cell heat dissipation requirement Q req From the fuel cell output current, determine: Q req =N cell (E nernst -V cell )I (1); Where: N cell is the number of cells in the fuel cell, E nernst is the theoretical thermodynamic electromotive force, V cell is the fuel cell output voltage; In the fuel cell thermal management system, due to the presence of the disturbance Q of the heat exchanger exc , so the actual heat dissipation requirement is Q rea for: Q rea =Q req -Q exc (2)。 6. The fuel cell thermal management control method in waste heat recovery mode according to claim 4, characterized in that: In step 32, the actual heat dissipation requirement Q rea And the ambient temperature T amb Designed a MAP controller, which is a MAP table determined based on the principle of optimizing the energy consumption of the electronic water pump and fan; The ambient temperature corrects the actual heat dissipation requirement: Where: Q s is the actual heat dissipation demand correction, ΔT a_s is the actual temperature difference between the air side and the cooling side of the radiator after correction, ΔT a_rea The temperature difference between the current radiator air side and cooling side is calibrated; The cooling power of the radiator is Q ra : Q ra =L ra ·C air ·ΔT ra (4); Where: L ra is the air flow rate entering the radiator, C air is the specific heat capacity of air, ΔT ra It is the temperature difference between the front and rear ends of the radiator when the coolant flows through it; It can be obtained that the optimal temperature of the coolant at the outlet of the fuel cell stack is T full It can be expressed as:

7. The fuel cell thermal management control method in waste heat recovery mode according to claim 4, characterized in that: In step 32, an extended state observer (ESO) is used to estimate and compensate for disturbances of the heat exchanger, thereby improving model accuracy and robustness; Formula (5) can be organized into the following form: y=x (6); Where x = T full , u=I, δ=f+d, is the disturbance of the heat exchanger of the system, δ is called the total disturbance; Expand δ into a state of the system, so the original system can be reconstructed as: y=x1(7); The specific form of the extended state observer is: Where z1, z2 are the estimated values ​​of system states x1, x2 respectively; β1, β2 are observer gains; Observation error: Written in matrix form: Where E is the identity matrix, C = [10]; Select appropriate β so that the characteristic root of the matrix (A-βC) has a negative real part, so that the error e converges to 0 in a finite time; The heat exchanger disturbance of the system is obtained: d = z2 - f (13); Substituting the above equation into formula (6) and the value of d, the heat exchange capacity can be obtained: The heat exchanger disturbance is the fuel cell system loss, which is a negative value here.

8. The fuel cell thermal management control method in waste heat recovery mode according to claim 4, characterized in that: In step 32, the MAP controller is optimized, and the power consumption of the electronic water pump P pump for: Where: q pump is the coolant flow through the electronic water pump, ΔP is the pressure difference between the two ends of the electronic water pump, η pump is the efficiency of the electronic water pump; The power consumption of the fan is P fan for: Where: ΔP fan is the air flow resistance, V fan is the air volume flow rate; Therefore, the total power consumption of the fuel cell heat dissipation P total for: P total =P pump +P fan (17); Considering the economic benefits and the maximum reduction of power consumption, the optimal response problem is expressed as: x∈X,u∈U(20); x1(t0)=P0,x1(t f )=P f (21); Where: f(x, u, t) is the system transition equation, x = [P total T full ] is the state variable of the system, u=[n pump n fan ] is the control variable of the system, which is realized by changing the pump speed n in real time. pump , and fan speed n fan Change the real-time pump and fan power, P0, P f are the total power consumption values ​​from the starting point to the ending point respectively; X=[X1 X2],U=[U1 U2] are the boundary conditions of the system transition variable and control variable, respectively, as follows: Where: P pump，min , P pump，max is the minimum and maximum power consumption of the electronic water pump, P fan，min , P fan，max The minimum and maximum power consumption of the fan; T full，min , T full，max The lowest and highest temperatures of the fuel cell cooling water outlet; n pump，min , n pump，max is the minimum and maximum speed of the electronic water pump, n fan，min , n fan，max The minimum and maximum speed of the fan.

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