Coolant temperature control method for fuel cell system

Abstract

An electronic control unit for coolant temperature control of a fuel cell system of a vehicle includes: a vehicle mode determination module that determines that the fuel cell system is in a 0 kW idle mode based on a power request of the vehicle; a temperature detection module that detects a coolant temperature T in a cooling circuit of the fuel cell system; the temperature control module is used for starting a heating assembly in the cooling loop to heat the cooling liquid when the detected temperature T of the cooling liquid is lower than a first temperature threshold value T1; and deactivating the heating assembly and returning the fuel cell system to the 0kW idle mode when the detected coolant temperature T is higher than a second temperature threshold T2. The invention also relates to a fuel cell system and a method for controlling a coolant temperature in a fuel cell system. By adopting the scheme of the invention, the temperature of the cooling liquid can be kept when the vehicle is in a 0 kW idle mode at a lower environment temperature, so that the situation that the electric pile and Bops are frozen again due to the fact that the temperature of the cooling liquid is reduced to a freezing temperature is avoided.

Description

Technical Field

[0001] The present application relates to a fuel cell system, and particularly to a coolant temperature control device and method for a fuel cell system in the 0 kW idle mode. Background Art

[0002] In recent years, fuel cell systems have been widely used in electric vehicles, and it is necessary to use the fuel cell system to charge the battery unit of the electric vehicle. However, when the temperature of the battery unit is below 0°C, the vehicle battery cannot be charged, so it requires a long time of heating. For example, it takes about 3 minutes to increase the temperature by 1°C. Therefore, in this case, it is necessary to make the fuel cell system in the 0 kW idle state to avoid charging the battery by the fuel cell system.

[0003] However, in this 0 kW idle state, there may be a situation where it cannot quickly respond to the restart requirement or even cause the fuel cell stack to reverse polarize when the vehicle is restarted after being parked in a low-temperature environment for a long time (>12 hours).

[0004] Therefore, the control of the low-temperature start of the fuel cell system still needs to be improved. Summary of the Invention

[0005] The purpose of the present application is to improve the low-temperature restart control of the fuel cell system, so that when the ambient temperature is low and in the 0 kW idle state, the fuel cell stack can be quickly restarted, so that the fuel cell stack and the Bops (balance of plant auxiliary system) will not refreeze.

[0006] To achieve the above object, the present application provides an electronic control unit for controlling the coolant temperature of a fuel cell system for a vehicle, including: a vehicle mode determination module that determines that the fuel cell system is in the 0 kW idle mode based on the power request of the vehicle; a temperature detection module that detects the coolant temperature T in the cooling circuit of the fuel cell system; and a temperature control module that, when the detected coolant temperature T is lower than the first temperature threshold T1, activates a heating component in the cooling circuit to heat the coolant; and when the detected coolant temperature T is higher than the second temperature threshold T2, deactivates the heating component and the fuel cell system returns to the normal 0 kW idle mode.

[0007] Wherein, the temperature control module reports a heating component failure and shuts down the fuel cell system when the coolant temperature T is lower than the first temperature threshold T1 for a predetermined period of time t.

[0008] Optionally, the heating component is a heating pipeline parallel to the cooling circuit, and the heating pipeline includes a heater and a thermal circulation pump.

[0009] Optionally, the first temperature threshold T1 is 5°C, and the second temperature threshold T2 is 15°C.

[0010] Wherein, the heater is a PTC heater or an electric heater.

[0011] Wherein, the predetermined time period t is 30 s.

[0012] The present application further relates to a fuel cell system for a vehicle, comprising: a fuel cell stack; a cooling circuit connected to the stack, the cooling circuit including: a cooling connector connected to the stack; a coolant circulation pump for circulating the coolant; a temperature detector for measuring the coolant temperature; and a heating assembly for heating the coolant, the heating assembly including a heater and a heat circulation pump; and an electronic control unit as described above, which controls the heating assembly in the cooling circuit based on the coolant temperature detected by the temperature detector to adjust the coolant temperature.

[0013] Wherein, the heater is a PTC heater or an electric heater.

[0014] The present application further relates to a method for controlling the coolant temperature in a fuel cell system of a vehicle, the method being executed by the electronic control unit according to the above description, the method comprising the following steps: after the fuel cell system is started, determining that the fuel cell system is in the 0 kW idle mode according to the power request of the vehicle; detecting the coolant temperature T in the cooling circuit of the fuel cell system through a temperature sensor; when the coolant temperature T is not lower than the first temperature threshold T1, maintaining the normal 0 kW idle mode; when the coolant temperature T drops below the first temperature threshold T1, starting the heating assembly in the cooling circuit through the electronic control unit to heat the coolant; and when the coolant temperature T is higher than the second temperature threshold T2, deactivating the heating assembly to return the system to the normal 0 kW idle mode.

[0015] Optionally, the method of the present application further comprises the following steps: when the coolant temperature T is lower than the first temperature threshold T1 for a continuous predetermined time period t, the electronic control unit reports a heating assembly failure and shuts down the fuel cell system.

[0016] Wherein, the first temperature threshold T1 is 5°C, and the second temperature threshold T2 is 15°C.

[0017] Wherein, the predetermined time period t is 30 s.

[0018] Optionally, the heating assembly is a heating pipeline parallel to the cooling circuit, the heating pipeline including a heater and a heat circulation pump, and the heater is a PTC heater or an electric heater.

[0019] The present application also relates to a machine-readable storage medium storing executable instructions that, when executed, cause one or more processors to perform the method as described above.

[0020] Generally, in the 0 kW idle state of the fuel cell system, by closing the cut-off valve, fresh air is not supplied to the fuel cell stack. At this time, the operation of the anode system is the same as in normal operation, and the coolant pump in the cooling circuit of the fuel cell system still rotates at the lowest speed to quickly respond to the restart requirement. Since no power is output externally at this time, the fuel cell stack of the fuel cell system does not generate heat.

[0021] However, in this case, when the vehicle is restarted after being parked in a low-temperature environment for a long time (> 12 hours), the fuel cell system will perform a low-temperature cold start until the coolant temperature is higher than 5 °C. Then the fuel cell system will follow the power requested by the vehicle. Once there is no power request from the vehicle, since the power battery does not allow charging at this time, the fuel cell system will enter the 0 kW idle mode. The coolant temperature will rapidly decrease due to the very low ambient temperature (such as -30 °C), and the fuel cell stack does not generate heat. When the coolant temperature is lower than 0 °C, the fuel cell stack and the Bops (balance of plant auxiliary system) will refreeze. If the vehicle requests the fuel cell system to exit the 0 kW idle state for restart at this time, it may cause reverse polarization of the fuel cell stack.

[0022] By adopting the solution of the present application as described above, when the vehicle is in a low ambient temperature (such as -30 °C) and in the 0 kW idle mode, the temperature of the coolant can be maintained. Thus, it will not cause the fuel cell stack and the Bops to refreeze due to the coolant temperature dropping to the freezing temperature, improving the service life of the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments of the present application will be described in more detail with reference to the accompanying drawings, in which:

[0024] Figure 1 is a schematic diagram of a fuel cell system including a cooling circuit according to the present application; and

[0025] Figure 2 is a method block diagram for controlling the temperature of the coolant in the cooling circuit of the fuel cell system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Hereinafter, embodiments of the fuel cell system according to the present application and the temperature control process of the coolant in its cooling circuit will be described with reference to the accompanying drawings. The drawings are not drawn to scale, and some components are enlarged for clarity. The same or similar features in the drawings will be denoted by the same reference numerals, and their repeated description will be omitted.

[0027] Figure 1 FIG. shows a schematic diagram of a fuel cell system including a cooling circuit according to the present application. The fuel cell system includes a stack 1 having a cathode 13 and an anode 14. Cathode gas such as air is supplied to the cathode gas inlet 17 of the cathode 13, and the air discharged from the cathode gas outlet 18 of the cathode 13 is discharged to the outside of the vehicle through the tailpipe. Anode gas such as H with a certain humidity 2 is supplied to the anode 14 of the stack 1 through the anode gas inlet 19. The hydrogen molecules entering the anode 14 are adsorbed by the catalyst and ionized into hydrogen ions and electrons. The hydrogen ions are transferred to the cathode 13 through the proton exchange membrane in the stack 1, and the electrons flow to the cathode 13 through the external circuit to form an electric current. Air enters the cathode 13, and the oxygen in the air combines with the hydrogen ions and electrons at the cathode 13 to form water molecules, and is discharged from the cathode 13 together with other gases in the air. The gas discharged from the cathode gas outlet 18 can be called "cathode exhaust gas", and the cathode exhaust gas will eventually be discharged through the vehicle tailpipe.

[0028] In the fuel cell system, air can be supplied to the cathode gas inlet 17 through the electronic air compressor 2. An inlet shut-off valve 7 is provided between the electronic air compressor 2 and the cathode gas inlet 17 to control the entry and supply stop of the cathode gas. In addition, a flow regulating valve can also be provided between the electronic air compressor 2 and the cathode gas inlet 17 to regulate the feed flow of the air. An outlet shut-off valve 8 can also be provided at the cathode gas outlet 18 to control the discharge of the cathode gas.

[0029] The anode gas, i.e., hydrogen, enters the anode gas inlet 19 of the anode 14 through the hydrogen injector 3. The mixed gas containing water vapor discharged from the anode gas outlet 20 undergoes water-gas separation through the water separator 5. The separated water is discharged through the drain valve 6. The mixed gas after the water is separated enters the hydrogen circulation pump 4, and is compressed in the hydrogen circulation pump 4 and then mixed with the fresh hydrogen from the hydrogen injector 3. The mixed anode gas after mixing enters the anode gas inlet 19.

[0030] In practice, the operating temperature of the stack 1 will directly affect the catalytic conversion rate of the fuel cell, thereby affecting the hydration state inside the proton exchange membrane. Therefore, it is necessary to strictly control the operating temperature of the stack 1 to keep it in a relatively stable state. For this purpose, a corresponding cooling system or other temperature control devices are provided in the fuel cell system. Figure 1 Only a cooling system of a fuel cell system is shown by way of example.

[0031] Figure 1The cooling system of the fuel cell system shown includes a cooling circuit 21, and the cooling circuit 21 includes a cooling connector 9 associated with the fuel cell stack 1. The cooling connector 9 includes a coolant inlet 15 for supplying coolant to the fuel cell stack and a coolant outlet 16 for drawing coolant out of the fuel cell stack 1. The cooling circuit 21 further includes a coolant circulation pump 10 to make the coolant flow in the cooling circuit 21. In addition, the cooling circuit 21 may further include other components such as a heat exchanger. In this way, generally under the action of the coolant circulation pump 2, the coolant enters the fuel cell stack 1 from the coolant inlet 15, and then is discharged from the fuel cell stack through the coolant outlet 16, and circulates in this way.

[0032] The cooling circuit 21 further includes a heating pipeline between the coolant outlet 16 and the coolant circulation pump 10. The heating pipeline includes a heater 11 and a heat circulation pump 12. The heating pipeline is connected in parallel with the main line of the cooling circuit 21 to heat the coolant in the cooling circuit 21 when needed. The heater 11 can be an electric heater or other heaters, such as a PTC heater. The heating pipeline may also include a flow control valve and a switch valve to control the connection and disconnection of the heating pipeline with the main line of the cooling circuit 21 and the flow control of the coolant in the heating pipeline.

[0033] A temperature detection device, such as a temperature sensor, is also provided in the cooling circuit 21. The temperature sensor detects the temperature of the coolant in the cooling circuit 21 as needed and reports the detected temperature value to the vehicle control unit.

[0034] As mentioned above, when the vehicle is in a low-temperature environment and the battery cannot be charged, the fuel cell system needs to be in the 0 kW idle state to avoid the fuel cell system charging the battery.

[0035] In this 0 kW idle state, as Figure 1 shown, the cut-off valves 7 and 8 are closed, and fresh air is not supplied to the fuel cell stack 1. However, at this time, the operation of the anode 14 is the same as in the normal operation, that is, hydrogen is normally supplied to the anode 14 and circulates according to Figure 1 this. The coolant circulation pump 10 in the cooling circuit 21 of the fuel cell system still rotates at the lowest speed to quickly respond to the restart requirement. At this time, since no power is output externally, the fuel cell stack 1 does not generate heat.

[0036] In this 0 kW idle mode, if the coolant temperature is too low, the fuel cell stack and Bops will refreeze. At this time, if the vehicle requests the fuel cell system to exit the 0 kW idle state for restart, it may cause the fuel cell stack to reverse polar. Therefore, the coolant temperature must be guaranteed to reach a certain value, such as higher than 5 °C, to enable the fuel cell system to correctly restart from the 0 kW idle state.

[0037] That is to say, when the ambient temperature of the vehicle is relatively low (such as -30°C) and the vehicle is at 0 kW idle speed, it is necessary to maintain the temperature of the coolant so as not to cause the coolant temperature to drop to the freezing temperature, resulting in the fuel cell stack and Bops freezing again.

[0038] The method for controlling the temperature of the coolant in the cooling circuit 21 using a PTC heater will be described in detail below. The flow chart of this method is as Figure 2 shown.

[0039] First, in step S1, after the fuel cell system is started, if there is no power request from the vehicle, it is determined that the fuel cell system will enter the 0 kW idle mode, and then step S2 is entered.

[0040] In step S2, the temperature T of the coolant in the cooling circuit 21 is detected by a temperature sensor, and the value of the temperature T is evaluated. When the coolant temperature T is not lower than the first temperature threshold T1, for example, not lower than 5°C, the normal 0 kW idle mode is maintained, and this cycle continues.

[0041] When the coolant temperature T drops below the first temperature threshold T1, for example, below 5°C, step S3 is entered. In step S3, the PTC heater 11 and the thermal circulation pump 12 in the heating pipeline in the cooling circuit 21 are started by the electronic control unit to heat the coolant, and the temperature of the coolant is detected at any time, and then step S4 is entered.

[0042] In step S4, a timer is started. When the duration t during which the coolant temperature T is lower than the first temperature threshold T1, for example, 5°C, exceeds a predetermined time, for example, 30 seconds, step S6 is entered. In step S6, the FCCU will report a heating pipeline failure and shut down the fuel cell system; when the coolant temperature T is heated to higher than the second temperature threshold T2, for example, 15°C, step S5 is entered. In step S5, the electronic control unit deactivates the PTC heater and the thermal circulation pump, and resets the timer, and the system returns to the normal 0 kW idle mode, and this cycle continues.

[0043] The above control process only takes the PTC heater as an example. In fact, various other heaters in the prior art, such as electric heaters, can be used according to needs based on different heating powers and thermal efficiencies, etc.

[0044] Through the control method described above, the temperature T of the coolant in the cooling circuit 21 can always be maintained within a suitable temperature range, so that the fuel cell system is in the normal 0 kW idle state, and can enter the restart state normally from the 0 kW idle state at any time according to the power request of the vehicle. Thus, it will not cause the fuel cell stack temperature to be too low due to the too low coolant temperature, and further cause the fuel cell stack and Bops to freeze again, resulting in vehicle start-up failures.

[0045] The first temperature threshold T1 and the second temperature threshold T2 of the coolant as described above are only for illustrative purposes and are not limited to the listed temperature values, but can be set according to the needs of different fuel cell systems.

[0046] The definition of the duration t value that the coolant temperature T as described above is lower than the first temperature threshold T1 is also only for illustrative purposes and is not limited to the listed time values, but can be set according to different fuel cell systems.

[0047] The temperature detection device as described above can be various temperature sensors known in the art, such as an infrared temperature sensor, a thermocouple temperature sensor, etc.

[0048] Through the above design of the present application, when the vehicle is in a low-temperature environment, the stack can be maintained within a suitable temperature range. Moreover, when the fuel cell system restarts from 0 kW idle speed, reverse polarization of the stack caused by freezing of the stack and Bops can be avoided.

[0049] Although the present invention has been described with reference to the preferred embodiments, this does not mean a limitation to the present invention. It should be understood that the protection scope of the present invention is defined by the appended claims, and those skilled in the art can make various modifications without departing from this scope.

Claims

1. An electronic control unit for controlling the coolant temperature of a fuel cell system for a vehicle, comprising: A vehicle mode determination module that determines that the fuel cell system is in the 0 kW idle mode based on the power request of the vehicle; A temperature detection module that detects the coolant temperature T in the cooling circuit of the fuel cell system; A temperature control module that, when the detected coolant temperature T is lower than the first temperature threshold T1, activates a heating component in the cooling circuit to heat the coolant; And when the detected coolant temperature T is higher than the second temperature threshold T2, deactivates the heating component and the fuel cell system returns to the normal 0 kW idle mode.

2. The electronic control unit according to claim 1, wherein, The temperature control module reports a heating component failure and shuts down the fuel cell system when the coolant temperature T is lower than the first temperature threshold T1 for a predetermined period of time t.

3. The electronic control unit according to claim 1 or 2, wherein, The heating component is a heating pipeline connected in parallel with the cooling circuit, and the heating pipeline includes a heater and a thermal circulation pump.

4. The electronic control unit according to any one of claims 1-3, wherein, The first temperature threshold T1 is 5 °C.

5. The electronic control unit according to any one of claims 1-4, wherein, The second temperature threshold T2 is 15 °C.

6. The electronic control unit according to any one of claims 3-5, wherein, The heater is a PTC heater or an electric heater.

7. The electronic control unit according to any one of claims 1-6, wherein, The predetermined period of time t is 30 s.

8. A fuel cell system for a vehicle, comprising: The stack of the fuel cell; A cooling circuit connected to the stack, the cooling circuit includes: a cooling connector connected to the stack; a coolant circulation pump for circulating the coolant; a temperature detector for measuring the coolant temperature; and a heating component for heating the coolant, the heating component includes a heater and a thermal circulation pump; and The electronic control unit according to any one of claims 1-7, which controls the heating component in the cooling circuit based on the coolant temperature detected by the temperature detector to adjust the coolant temperature.

9. The fuel cell system according to claim 8, wherein, The heater is a PTC heater or an electric heater.

10. A method for controlling the coolant temperature in a fuel cell system of a vehicle, the method is executed by the electronic control unit according to any one of claims 1-7, the method comprises the following steps: After the fuel cell system is started, determine that the fuel cell system is in the 0 kW idle mode according to the power request of the vehicle; Detect the coolant temperature T in the cooling circuit of the fuel cell system through a temperature sensor; When the coolant temperature T is not lower than the first temperature threshold T1, maintain the normal 0 kW idle mode; When the coolant temperature T drops below the first temperature threshold T1, activate the heating component in the cooling circuit through the electronic control unit to heat the coolant; and When the coolant temperature T is higher than the second temperature threshold T2, the heating component is deactivated, and the system returns to the normal 0 kW idle mode.

11. The method according to claim 10 further includes the following steps: when the coolant temperature T is lower than the first temperature threshold T1 for a predetermined time period t, the electronic control unit reports a heating component failure and shuts down the fuel cell system.

12. The method according to claim 10 or 11, wherein, the first temperature threshold T1 is 5 °C.

13. The method according to any one of claims 10-12, wherein, the second temperature threshold T2 is 15 °C.

14. The method according to any one of claims 10-13, wherein, the predetermined time period t is 30 s.

15. The method according to any one of claims 10-14, wherein, the heating component is a heating pipeline parallel to the cooling circuit, the heating pipeline includes a heater and a thermal circulation pump, and the heater is a PTC heater or an electric heater.

16. A machine-readable storage medium stores executable instructions that, when executed, cause one or more processors to perform the method according to any one of claims 10-15.

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