Hydrogen fuel cell thermal management system for vehicles and method of controlling the same

Abstract

A hydrogen fuel cell thermal management system for vehicles and a control method thereof, comprising: a hydrogen fuel cell stack with a cooling liquid circulation pipeline, an electronic thermostat, an electric heater, a radiator, a pressurized water tank, a water pump, an intercooler and a heat exchanger. The present application optimizes the system control strategy for different operating conditions of the vehicle, i.e. different output of the fuel cell, to achieve temperature control of the stack while reducing the power consumption of the radiator, significantly improving the overall endurance of the fuel cell vehicle.

Description

Technical Field

[0001] This invention relates to a technology in the field of automotive battery control, specifically a thermal management system for automotive hydrogen fuel cells and its control method. Background Technology

[0002] Hydrogen fuel cell vehicles have the advantages of zero emissions and high energy conversion efficiency. However, fuel cell stacks generate a lot of heat during operation. High-power fuel cell stacks require a large amount of compressed air during operation, and the compressed air needs to be cooled before entering the fuel cell. Existing fuel cells consume a lot of electricity when the air conditioning is running in winter. The control strategies are relatively simple under different operating conditions, which makes it difficult for the overall battery efficiency to meet the requirements. Summary of the Invention

[0003] To address the aforementioned shortcomings of existing technologies, this invention proposes a thermal management system and control method for hydrogen fuel cells in vehicles. It optimizes the system control strategy for different vehicle operating conditions, i.e., different fuel cell output states, achieving temperature control of the fuel cell stack while reducing the power consumption of the radiator, thus significantly improving the overall driving range of fuel cell vehicles.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to a thermal management system for a vehicle-mounted hydrogen fuel cell, comprising: a hydrogen fuel cell stack with a coolant circulation pipeline, an electronic thermostat, an electric heater, a radiator, a booster tank, a water pump, an intercooler, and a heat exchanger. The coolant pipeline outlet of the hydrogen fuel cell stack is connected via a throttle valve to the first port of a first three-way valve and the inlet of the intercooler. The second and third ports of the first three-way valve are connected to the inlet of the water pump and the outlet of the booster tank, respectively. The outlet of the water pump is connected to the first port of a second three-way valve. The second and third ports of the second three-way valve are connected to the first port of the electronic thermostat. One valve port is connected to the inlet of the heat exchanger, the outlet of the heat exchanger is connected to the inlet of the radiator, the outlet of the radiator is connected to the first valve port of the third three-way valve, the second and third valve ports of the third three-way valve are connected to the inlet of the deionizer and the second valve port of the electronic thermostat, respectively, the third valve port of the electronic thermostat is connected to the inlet of the electric heater, the outlet of the electric heater is connected to the first valve port of the fourth three-way valve, the second and third valve ports of the fourth three-way valve are connected to the outlet of the intercooler and the inlet of the hydrogen fuel cell stack, respectively, and the outlet of the deionizer is connected to the inlet pipe of the pressurized water tank.

[0006] The aforementioned vehicle hydrogen fuel cell thermal management system further includes a controller, which is connected to the fuel cell, temperature sensors located in the cooling water pipes at the inlet and outlet of the fuel cell stack, a water pump, a heat exchanger, a radiator, an electronic thermostat, and an electric heater. The controller receives temperature information from the cooling water pipes and output current information from the fuel cell stack. It controls the electronic thermostat valve using the temperature information from the cooling water pipes at the fuel cell stack inlet as input and the opening degree of the electronic thermostat valve as output; it controls the electric heater using the temperature information from the cooling water pipes at the fuel cell stack inlet as input and the start / stop status of the electric heater as output; it controls the radiator power using the temperature information from the cooling water pipes at the fuel cell stack outlet as input and the voltage of the cooling fan in the radiator as output; it controls the heat exchanger using the temperature information from the cooling water pipes at the fuel cell stack outlet as input and the opening / closing status of the heat exchanger's electronic valve as output; and it controls the water pump flow rate using the output current of the fuel cell stack as input and the frequency of the water pump motor as output.

[0007] The controller includes: a PLC controller, an analog-to-digital signal conversion module, a relay output module, a DC fan speed control module, a water pump DC motor drive module, a thermostat valve motor drive module, and a heat exchanger electronic valve module. The analog-to-digital signal conversion module's input is connected to two temperature sensors, and its output is connected to the PLC controller's input. The module receives analog signals from the temperature sensors, converts them into digital signals, and outputs them to the PLC controller. The PLC controller's input is connected to the fuel cell, receiving the fuel cell's output current signal. The PLC controller's output is connected to the relay output module, the DC fan speed control module, the water pump DC motor drive module, and the thermostat valve motor drive module, respectively. The heat exchanger electronic valve is connected to transmit the start / stop control signal of the electric heater to the relay output module, the voltage control signal of the radiator fan to the DC fan speed control module, the frequency control signal of the water pump motor to the DC motor drive module of the water pump, the opening control signal of the thermostat valve to the thermostat valve motor drive module, and the opening / closing control signal of the heat exchanger valve to the heat exchanger electronic valve module. The output terminal of the relay output module is connected to the electric heater to control the start / stop of the electric heater. The output terminal of the DC fan speed control module is connected to the radiator fan to control the voltage of the radiator fan. The output terminal of the DC motor drive module of the water pump is connected to the water pump motor to control the flow rate of the water pump. The output terminal of the thermostat valve motor drive module is connected to the thermostat valve motor to control the opening degree of the thermostat valve.

[0008] Technical effect

[0009] Compared with existing technologies, this invention addresses the problem of excessively long cold start time for automotive fuel cells by controlling the electronic thermostat to change the circulation loop and control the heater to heat the cooling water, thereby improving the start-up speed. For changes in operating conditions during operation, this invention improves upon existing dual-PID control strategies by using real-time and precise monitoring of the temperature difference between the inlet and outlet of the fuel cell stack's cooling water and the fuel cell's output current. It employs a PID control strategy to control the radiator's operation and a flow-following-current control strategy to control the water pump's operation, reducing the maximum overshoot of the fuel cell stack's cooling water outlet temperature, reducing the maximum deviation of the fuel cell stack's cooling water temperature, and shortening the average settling time. When the vehicle's air conditioning is on in winter, the invention preheats the cold air entering the air conditioning system through a heat exchanger, reducing the power consumption of the radiator and air conditioning system, improving system output efficiency, and increasing the vehicle's range.

[0010] This invention solves the problem of excessively long cold start time for automotive fuel cells in the prior art; improves the poor control effect caused by coupling in the control system; and can recover waste heat to improve system output efficiency and range. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the system of the present invention;

[0012] Figure 2 Flowchart for initialization of an example;

[0013] Figure 3 This is a flowchart of the idle state in an embodiment;

[0014] Figure 4 This is a flowchart illustrating the operation of an example.

[0015] Figure 5 This is the end flowchart of the embodiment;

[0016] Figure 6 This is a schematic diagram of the experimental setup for an example embodiment;

[0017] Figure 7 The existing PID control strategy includes cooling water flow rate and fan voltage curves;

[0018] Figure 8 The existing PID control strategy includes cooling water inlet and outlet temperature and temperature difference curves.

[0019] Figure 9 The implementation example uses control strategies for cooling water flow and fan voltage;

[0020] Figure 10 The control strategy for this example includes the inlet and outlet temperatures and temperature difference curves of the cooling water.

[0021] In the diagram: 1 Hydrogen fuel cell stack, 2 Throttling valve, 3 First three-way valve, 4 Water pump, 5 Second three-way valve, 6 Heat exchanger, 7 Radiator, 8 Third three-way valve, 9 Electronic thermostat, 10 Electric heater, 11 Fourth three-way valve, 12 Intercooler, 13 Deionizer, 14 Booster tank, 15 Controller, 16 First temperature sensor, 17 Second temperature sensor. Detailed Implementation

[0022] like Figure 1 As shown in the figure, this embodiment relates to a thermal management system for a vehicle-mounted hydrogen fuel cell, including: a hydrogen fuel cell stack 1 with a coolant circulation pipeline, an electronic thermostat 9, an electric heater 10, a radiator 7, a booster tank 14, a water pump 4, an intercooler 12, and a heat exchanger 6. The coolant pipeline outlet of the hydrogen fuel cell stack 1 is connected to the first port of a first three-way valve 3 and the inlet of the intercooler 12 via a throttle valve 2. The second and third ports of the first three-way valve 3 are connected to the inlet of the water pump 4 and the outlet of the booster tank 14, respectively. The outlet of the water pump 4 is connected to the first port of a second three-way valve 5. The second and third ports of the second three-way valve 5 are connected to the electronic thermostat 9. The first valve port is connected to the inlet of heat exchanger 6, the outlet of heat exchanger 6 is connected to the inlet of radiator 7, the outlet of radiator 7 is connected to the first valve port of the third three-way valve 8, the second and third valve ports of the third three-way valve 8 are connected to the inlet of deionizer 13 and the second valve port of electronic thermostat 9 respectively, the third valve port of electronic thermostat 9 is connected to the inlet of electric heater 10, the outlet of electric heater 10 is connected to the first valve port of fourth three-way valve 11, the second and third valve ports of fourth three-way valve 11 are connected to the outlet of intercooler 12 and the inlet of hydrogen fuel cell stack 1 respectively, and the outlet of deionizer 13 is connected to the inlet pipeline of pressurized water tank 14.

[0023] The aforementioned vehicle hydrogen fuel cell thermal management system further includes a controller 15, which is connected to temperature sensors 16 and 17, water pump 4, heat exchanger 6, radiator 7, electronic thermostat 9, and electric heater 10, respectively, located in the cooling water pipes at the inlet and outlet of the fuel cell stack. The controller 15 receives temperature information from temperature sensors 16 and 17, outputs a water pump motor frequency control signal to control the flow of water pump 4, outputs an electronic valve control signal for the heat exchanger to control the start and stop of heat exchanger 6, outputs a radiator fan voltage control signal to control the power of heat exchanger 6, outputs an electronic thermostat valve opening signal to control the electronic thermostat 9, and outputs a start and stop signal for the electric heater to control the start and stop of electric heater 10.

[0024] like Figures 2-5As shown, this embodiment relates to the control method of the above system. When the vehicle is initially started, the controller 15 is powered on and started, the PLC completes initialization, and enters an idle state after initialization. The fan voltage of the radiator 7 is set to zero, the motor frequency of the water pump 4 is set to zero, the valve opening of the electronic thermostat 9 is set to zero, that is, the first valve is fully open and the second valve is fully closed. The state of the heat exchanger 6 is set to zero, that is, the valve of the heat exchanger 6 is closed, and the state of the heater 10 is set to zero, that is, the heater 10 is de-energized. When the vehicle gives the fuel cell stack system start-up command, the PLC operation phase begins, the fuel cell stack 1 starts working, and the water pump 4 is set to the set minimum speed. The system operates rapidly. At this point, the temperature at temperature sensor 16 is less than 50℃, so the electric heater 10 is activated. While maintaining the operation of other components, the cooling water temperature continues to rise. When the temperature at temperature sensor 16 is greater than 50℃ but less than 60℃, the electric heater 10 stops operating. The opening of the electronic thermostat 9 valve is controlled according to the temperature; the higher the temperature, the larger the valve opening, meaning a larger flow rate at the second valve port. When the temperature at temperature sensor 16 reaches 60℃, the valve opening is at its maximum, meaning the second valve port is fully open and the first valve port is fully closed. When the temperature at temperature sensor 16 reaches 60℃, the fuel... After the cold start process of the fuel cell is completed, the fuel cell stack 1 reaches the optimal operating temperature range of 60-65℃ and enters the working state. It determines whether the vehicle's heating system is on. If it is, the valve of heat exchanger 6 is opened; otherwise, the valve remains closed. During vehicle operation, the output current of fuel cell stack 1 changes with the operating conditions. Using the temperature at temperature sensor 16 as the input and setting the temperature parameter to 60℃, PID control is applied to radiator 7. Using the output current of fuel cell stack 1 as the input, the control is based on the relationship between the stack output current and... The flow rate of water pump 4 corresponds to the motor frequency of water pump 4, that is, the flow rate follows the fuel cell stack current strategy to control water pump 4. When the vehicle is turned off and stopped, the PLC system shutdown process begins. First, the fuel cell stack 1 stops working, water pump 4 is set to run at low speed, radiator 7 is set to run at maximum power, heat exchanger 6 valve is closed, electronic thermostat 9 valve is opened to the maximum, that is, the second valve port is fully open, electric heater 10 is kept closed, when the temperature at temperature sensor 17 is lower than 50℃, radiator 7 is turned off, water pump 4 is turned off after a 30s delay, all controllers are reset, and the shutdown ends.

[0025] This system enables rapid warming of the coolant during vehicle cold starts. The coolant flows through a small loop (fuel cell stack 1, three-way valve 2, three-way valve 3, water pump 4, three-way valve 5, electronic thermostat 9, electric heater 10, three-way valve 11) to ensure the coolant reaches the hydrogen fuel cell reaction temperature quickly. When the coolant temperature is about to reach the optimal reaction temperature range of 60-65°C, the opening of the electronic thermostat 9 is adjusted to allow fuel cell stack 1 to quickly and stably enter the operating temperature range. Once the coolant temperature reaches the fuel cell stack's operating temperature of 60-65°C, fuel cell stack 1 enters the working state. As the vehicle's operating conditions change, the output power and current of fuel cell stack 1 change accordingly, as does the heat generation. The system employs real-time monitoring of the inlet and outlet temperatures of the cooling water to the fuel cell stack, along with real-time output current information. This allows the controller to precisely manage the operation of the radiator 7 and water pump 4, ensuring the hydrogen fuel cell system operates within its optimal reaction temperature range. A combination of PID control and flow-following stack current strategies is used to control the radiator 7 and water pump 4, improving system control accuracy and speed. When the vehicle's air conditioning is on in winter, the heat exchanger 6 preheats the incoming cold air, reducing the power consumption of the radiator and air conditioning system, increasing system output efficiency, and enhancing the vehicle's range. Furthermore, this thermal management system cools the compressed air entering the fuel cell stack, reducing the need for additional cooling structures within the vehicle.

[0026] This invention, through the application of an electronic thermostat and its control based on temperature changes during the cold start process of the fuel cell stack, significantly improves the cold start speed of the fuel cell stack compared to conventional techniques that do not use a thermostat. Compared to some techniques that use wax-type thermostats, the temperature characteristics of wax-type thermostats are non-linear and only related to their structure and materials, and cannot be changed once installed. The temperature characteristics of the electronic thermostat can be adjusted and set as needed. The most efficient temperature characteristic curve can be found and set by reducing the temperature adjustment range and through experimental verification, thereby further improving the cold start speed of the fuel cell stack.

[0027] This invention improves control performance, reduces control error, and increases control speed by employing specific control strategies for the radiator and water pump. In contrast to conventional techniques that primarily use the fuel cell stack cooling water outlet temperature and the inlet / outlet temperature difference as inputs and employ PID control to control the radiator and water pump (which suffers from poor control due to strong coupling of inputs), this invention uses the fuel cell stack outlet temperature as the input and a PID strategy to control the radiator. It also uses the fuel cell stack output current as the input and controls the pump based on the functional relationship between the water pump flow rate and the fuel cell stack current.

[0028] A 20kW adjustable power electric heating element was used to replace the heat generated during the operation of the 15kW fuel cell stack. Test experiments were conducted to verify the effectiveness of the thermal management system. Experiments were performed focusing on the variation of fuel cell output power during vehicle operation to verify the effectiveness of the relevant control strategies. The experimental setup is shown in the figure below. Figure 6 As shown in the figure. The heat exchanger was shut off in the experiment, and relevant parameters were measured based on the changes in the fuel cell stack output current. The fuel cell stack inlet temperature was set to 60℃, the inlet and outlet temperature difference to 5.5℃, and the fuel cell stack output current changed from 18A to 25A to 28A to 30A. Comparative experiments were conducted between the existing PID control strategy and the control strategy described in the above embodiment, and the relevant experimental data are shown below. Figures 7-10 As shown, according to experimental data, under the existing PID control strategy, the maximum overshoot of the fuel cell cooling water outlet temperature is 1.12℃, the maximum deviation of the inlet and outlet temperature difference is 0.75℃, and the average settling time is 168s; under the control strategy of the embodiment, the maximum overshoot of the fuel cell cooling water outlet temperature is 0.4℃, the maximum deviation of the inlet and outlet temperature difference is 0.4℃, and the average settling time is 95s.

[0029] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A hydrogen fuel cell thermal management system for a vehicle, characterized by, include: The hydrogen fuel cell stack includes a coolant circulation pipeline, an electronic thermostat, an electric heater, a radiator, a booster tank, a water pump, an intercooler, a heat exchanger, and a controller. Specifically: the coolant pipeline outlet of the hydrogen fuel cell stack is connected via a throttle valve to the first port of a first three-way valve and the inlet of the intercooler. The second and third ports of the first three-way valve are connected to the inlet of the water pump and the outlet of the booster tank, respectively. The outlet of the water pump is connected to the first port of a second three-way valve. The second and third ports of the second three-way valve are connected to the first port of the electronic thermostat and the... The heat exchanger's inlet is connected to the radiator's outlet, which in turn is connected to the radiator's inlet. The radiator's outlet is connected to the first port of the third three-way valve. The second and third ports of the third three-way valve are connected to the deionizer's inlet and the electronic thermostat's second port, respectively. The electronic thermostat's third port is connected to the electric heater's inlet, and the electric heater's outlet is connected to the first port of the fourth three-way valve. The second and third ports of the fourth three-way valve are connected to the intercooler's outlet and the hydrogen fuel cell stack's inlet, respectively. The deionizer's outlet is connected to the booster... The water tank's inlet pipe is connected; the controller is connected to the fuel cell, temperature sensors located on the cooling water pipes at the fuel cell stack's inlet and outlet, water pump, heat exchanger, radiator, electronic thermostat, and electric heater; the controller receives temperature information from the cooling water pipes and the fuel cell stack's output current information, and uses the temperature information from the cooling water pipe at the fuel cell stack's inlet as input and the opening degree of the electronic thermostat valve as output to control the electronic thermostat valve; uses the temperature information from the cooling water pipe at the fuel cell stack's inlet as input and the start / stop status of the electric heater as output to control the electric heater; uses the temperature information from the cooling water pipe at the fuel cell stack's outlet as input and the voltage of the cooling fan in the radiator as output to control the radiator power; uses the temperature information from the cooling water pipe at the fuel cell stack's outlet as input and the opening / closing status of the heat exchanger's electronic valve as output to control the heat exchanger; uses the output current of the fuel cell stack as input and the frequency of the water pump motor as output to control the water pump flow rate.

2. The hydrogen fuel cell thermal management system for vehicles of claim 1, wherein, The controller includes: a PLC controller, an analog-to-digital signal conversion module, a relay output module, a DC fan speed control module, a water pump DC motor drive module, a thermostat valve motor drive module, and a heat exchanger electronic valve module. The analog-to-digital signal conversion module's input is connected to two temperature sensors, and its output is connected to the PLC controller's input. The module receives analog signals from the temperature sensors, converts them into digital signals, and outputs them to the PLC controller. The PLC controller's input is connected to the fuel cell, receiving the fuel cell's output current signal. The PLC controller's output is connected to the relay output module, the DC fan speed control module, the water pump DC motor drive module, and the thermostat valve motor drive module, respectively. The heat exchanger electronic valve is connected to transmit the start / stop control signal of the electric heater to the relay output module, the voltage control signal of the radiator fan to the DC fan speed control module, the frequency control signal of the water pump motor to the DC motor drive module of the water pump, the opening control signal of the thermostat valve to the thermostat valve motor drive module, and the opening / closing control signal of the heat exchanger valve to the heat exchanger electronic valve module. The output terminal of the relay output module is connected to the electric heater to control the start / stop of the electric heater. The output terminal of the DC fan speed control module is connected to the radiator fan to control the voltage of the radiator fan. The output terminal of the DC motor drive module of the water pump is connected to the water pump motor to control the flow rate of the water pump. The output terminal of the thermostat valve motor drive module is connected to the thermostat valve motor to control the opening degree of the thermostat valve.

3. The control method of the hydrogen fuel cell thermal management system for vehicles according to claim 1 or 2, characterized by, When the vehicle is initially started, the controller is powered on and the PLC completes initialization. After initialization, it enters an idle state. The radiator fan voltage is set to zero, the water pump motor frequency is set to zero, the electronic thermostat valve opening is set to zero (first valve fully open, second valve fully closed), the heat exchanger status is set to zero (heat exchanger valve closed), and the heater status is set to zero (heater de-energized). When the vehicle issues a start-up command for the fuel cell stack system, the PLC's operation phase begins, the fuel cell stack starts working, and the water pump is set to operate at the set minimum speed. At this time, the temperature at the temperature sensor is less than 50°C, the electric heater is started, and the operating status of other components remains unchanged. The coolant temperature continues to rise. When the temperature at the temperature sensor is greater than 50°C but less than 60°C, the electric heater stops working. The opening of the electronic thermostat valve is controlled according to the temperature; the higher the temperature, the larger the valve opening, meaning a larger flow rate at the second valve. When the temperature at the temperature sensor reaches 60°C, the valve opening is at its maximum (second valve fully open, first valve fully closed). When the temperature at the temperature sensor reaches 60°C, the fuel cell cold start process is complete. When the fuel cell stack reaches its optimal operating temperature range of 60-65℃, it enters the working state. The system determines whether the vehicle's heating system is on. If it is, the heat exchanger valve opens; otherwise, it remains closed. During vehicle operation, the fuel cell stack's output current changes with operating conditions. Using the temperature sensor as input and setting the temperature parameter to 60℃, the system performs PID control of the radiator. Using the fuel cell stack's output current as input, the system controls the water pump's motor frequency based on the correlation between the stack's output current and the water pump's flow rate—a flow rate-following-stack-current strategy. When the vehicle shuts down, the PLC system's shutdown process begins. First, the fuel cell stack stops working. The water pump is set to operate at low speed, the radiator at maximum power, the heat exchanger valve is closed, the electronic thermostat valve is at its maximum opening (second valve fully open), and the electric heater remains closed. When the temperature sensor temperature drops below 50℃, the radiator shuts down. After a 30-second delay, the water pump shuts down, all controllers reset, and the shutdown ends.

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