Cold start control method and control device for fuel cell system, vehicle

Abstract

The present invention discloses a cold start control method, a control device and a vehicle for a fuel cell system. The fuel cell system includes a fuel cell stack, an intercooler, an air compressor and a water pump. The method includes: adjusting the boost ratio of the air compressor and determining a target air metering ratio according to the current density of the fuel cell stack; adjusting the air flow rate entering the air compressor based on the target air metering and controlling the air compressor according to the boost ratio; when the voltage of the fuel cell stack meets the voltage preset condition, increasing the power supply current of the fuel cell stack at a preset current rate until the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack meet the preset temperature condition, and determining that the cold start of the fuel cell stack is completed. The control method of the present invention can improve the reliability of the fuel cell engine during low-temperature cold start, shorten the cold start time, reduce the heating components, save costs and avoid maintenance.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular, to a cold start control method for a fuel cell system, a vehicle, and a cold start control device for a fuel cell system. Background Art

[0002] Low-temperature cold start is a function that a fuel cell engine must possess. Currently, it is required that a fuel cell has the ability to cold start at -30°C. During low-temperature cold start, icing often occurs inside the fuel cell stack, which easily leads to start-up failure. Therefore, the low-temperature cold start control strategy plays a decisive role in whether the engine can be successfully started. The low-temperature cold start methods adopted in the current related technologies are mainly divided into two modes: external heating and internal heating; the external heating mode mainly sets an external PTC (Positive Temperature Coefficient) (generally referring to a positive temperature coefficient thermistor), and heats the coolant to achieve the purpose of rapid temperature rise; the internal heating mode mainly reduces the cathode excess coefficient, increases the concentration polarization of the cathode to increase the heat generation inside the fuel cell stack, and achieves the purpose of rapid temperature rise. Although the external PTC heating is simple and easy to operate, the engine adds extra components and wiring harnesses, increasing the overall cost of the machine and the insulation design.

[0003] Internal heating mainly makes the cathode experience oxygen starvation by reducing the cathode excess coefficient, and makes the fuel cell stack work at the near short-circuit point to generate a large amount of waste heat for rapid temperature rise. This operation method is extremely effective for the temperature rise of the fuel cell stack, but it is a relatively dangerous behavior for the fuel cell stack to work at the near short-circuit point. Once the calculation of the hydrogen supply amount is incorrect, it will cause the fuel cell stack to burn out or more serious accidents. This solution has extremely high requirements for the fluid distribution uniformity of the fuel cell stack and is difficult to control.

[0004] In addition, in related technologies, there is also a method of separately heating the inlet temperatures of the cathode and anode using resistance wires to enable rapid temperature rise during cold start of the fuel cell stack. This method is similar to the PTC-based solution and has a more complex structure, without obvious advantages over PTC heating. There is also a method of setting up a hydrogen heater in the fuel cell system to heat the fresh hydrogen of the system through the cathode tail drain water and gas, which can increase the inlet temperature of the fresh hydrogen during cold start and shorten the overall cold start time. An external heating device, PTC, is also set up to heat the coolant to shorten the cold start time of the fuel cell system. The cold start during low temperature is carried out by combining two self-heating methods inside the fuel cell stack and the external heating device, optimizing the cold start of the fuel cell system. However, this also adds three components, namely the hydrogen heater, the cathode tail drain heat exchanger, and PTC, resulting in an increase in the overall cost of the machine. In another related technology, by setting up an outer coolant pipe to wrap the inner coolant pipe and filling the space between them with supersaturated sodium acetate solution, during cold start, the supersaturated sodium acetate solution is crystallized by using a perturbation component, and a large amount of heat is released during the crystallization process, reducing the power consumption of the power battery during cold start. However, this solution is more complex and difficult to implement. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems in the related technologies to some extent. For this purpose, the first object of the present invention is to propose a cold start control method for a fuel cell system, which adjusts the boost ratio of the air compressor, determines the target air metering ratio according to the current density of the fuel cell stack, adjusts the air flow rate entering the air compressor based on the target air metering, and controls the air compressor according to the boost ratio. When the voltage of the fuel cell stack meets the voltage preset condition, the supply current of the fuel cell stack is increased at a preset current rate until the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack meet the preset temperature conditions, and it is determined that the cold start of the fuel cell stack is completed. Thereby, the reliability of the fuel cell engine during cold start at low temperature can be improved, the cold start time can be shortened, and the heating components can be reduced, saving costs and avoiding maintenance.

[0006] The second object of the present invention is to propose a vehicle.

[0007] The third object of the present invention is to propose a cold start control device for a fuel cell system.

[0008] To achieve the above object, an embodiment of the first aspect of the present invention provides a cold start control method for a fuel cell system. The fuel cell system includes a fuel cell stack, an intercooler, an air compressor, and a water pump. The cathode inlet of the fuel cell stack is connected to the air compressor through the intercooler. One end of the water pump is connected to the heating inlet of the intercooler and the fuel cell stack respectively to transfer the heat after heat exchange in the intercooler to the fuel cell stack. The method includes: adjusting the boost ratio of the air compressor, and determining a target air stoichiometric ratio according to the current density of the fuel cell stack; adjusting the air flow rate entering the air compressor based on the target air stoichiometric ratio, and controlling the air compressor according to the boost ratio; when the voltage of the fuel cell stack meets the voltage preset condition, increasing the supply current of the fuel cell stack at a preset current rate until the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack meet the preset temperature condition, and determining that the cold start of the fuel cell stack is completed.

[0009] According to the cold start control method of the fuel cell system in the embodiment of the present invention, the boost ratio of the air compressor is adjusted, and the target air stoichiometric ratio is determined according to the current density of the fuel cell stack. The air flow rate entering the air compressor is adjusted based on the target air stoichiometric ratio, and the air compressor is controlled according to the boost ratio. When the voltage of the fuel cell stack meets the voltage preset condition, the supply current of the fuel cell stack is increased at a preset current rate until the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack meet the preset temperature condition, and it is determined that the cold start of the fuel cell stack is completed. Thus, this method can improve the reliability of the low-temperature cold start of the fuel cell engine, shorten the cold start time, reduce heating components, save costs and avoid maintenance.

[0010] In addition, the cold start control method of the fuel cell system according to the above embodiment of the present invention may further have the following additional technical features:

[0011] According to an embodiment of the present invention, the adjusting the boost ratio of the air compressor includes: increasing the boost ratio of the air compressor to a target boost ratio.

[0012] According to an embodiment of the present invention, the determining the target air stoichiometric ratio according to the current density of the fuel cell stack includes: determining the current density interval where the current density is located; determining the target air stoichiometric ratio based on the current density interval, where different current density intervals correspond to different target air stoichiometric ratios.

[0013] According to an embodiment of the present invention, the target air stoichiometric ratio is determined by the following method:

[0014]

[0015] Wherein, y represents the target air stoichiometry ratio, and x represents the current density.

[0016] According to an embodiment of the present invention, when the average single-cell voltage of the fuel cell stack is greater than or equal to a first preset voltage threshold and the minimum single-cell voltage is greater than or equal to a second preset voltage threshold, it is determined that the voltage of the fuel cell stack meets the preset voltage condition, wherein the first preset voltage threshold is greater than the second preset voltage threshold.

[0017] According to an embodiment of the present invention, when increasing the supply current of the fuel cell stack at a preset current rate, the method further includes: when the lowest single-cell voltage of the fuel cell stack is greater than or equal to a third preset voltage threshold, continuously increasing the supply current of the fuel cell stack at the preset current rate; when the lowest single-cell voltage of the fuel cell stack is greater than a fourth preset voltage threshold and less than the third preset voltage threshold, keeping the current supply current of the fuel cell stack unchanged; and when the lowest single-cell voltage of the fuel cell stack is less than or equal to the fourth preset voltage threshold, stopping increasing the supply current of the fuel cell stack.

[0018] According to an embodiment of the present invention, during the process of increasing the supply current of the fuel cell stack at a preset current rate, the method further includes: when the coolant temperature difference between the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack is greater than a preset temperature difference, controlling the rotational speed of the water pump to increase.

[0019] According to an embodiment of the present invention, when the outlet coolant temperature of the fuel cell stack is greater than a first preset temperature threshold and the inlet coolant temperature of the fuel cell stack is greater than a second preset temperature threshold, it is determined that the preset temperature condition is met.

[0020] To achieve the above object, a vehicle according to an embodiment of the second aspect of the present invention includes a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, the cold start control method of the above fuel cell system is implemented.

[0021] The vehicle according to the embodiment of the present invention can improve the reliability of low-temperature cold start of the fuel cell engine, shorten the cold start time, reduce heating components, save costs and avoid maintenance by executing the cold start control method of the above fuel cell system.

[0022] To achieve the above object, an embodiment of the third aspect of the present invention provides a cold start control device for a fuel cell system. The fuel cell system includes a fuel cell stack, an intercooler, an air compressor, and a water pump. The cathode inlet of the fuel cell stack is connected to the air compressor through the intercooler. One end of the water pump is respectively connected to the intercooler and the heating inlet of the fuel cell stack to transfer the heat after heat exchange in the intercooler to the fuel cell stack. The device includes: an adjustment module for adjusting the boost ratio of the air compressor; a determination module for determining a target air stoichiometric ratio according to the current density of the fuel cell stack; a control module for adjusting the air flow rate entering the air compressor based on the target air stoichiometric ratio and controlling the air compressor according to the boost ratio. The control module is further configured to increase the supply current of the fuel cell stack at a preset current rate when the voltage of the fuel cell stack meets the voltage preset condition, and determine that the cold start of the fuel cell stack is completed until the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack meet the preset temperature conditions.

[0023] For the cold start control device of the fuel cell system according to the embodiment of the present invention, the adjustment module is used to adjust the boost ratio of the air compressor; the determination module is used to determine the target air stoichiometric ratio according to the current density of the fuel cell stack, the control module is used to adjust the air flow rate entering the air compressor based on the target air stoichiometric ratio and control the air compressor according to the boost ratio, and the control module is further used to increase the supply current of the fuel cell stack at a preset current rate when the voltage of the fuel cell stack meets the voltage preset condition, and determine that the cold start of the fuel cell stack is completed until the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack meet the preset temperature conditions. Thus, the device can improve the reliability of the low-temperature cold start of the fuel cell engine and shorten the cold start time, and reduce the heating components, saving costs and being maintenance-free.

[0024] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Description of the Drawings

[0025] Figure 1 It is a flowchart of the cold start control method for the fuel cell system according to the embodiment of the present invention;

[0026] Figure 2 It is a schematic structural diagram of the fuel cell system according to the embodiment of the present invention;

[0027] Figure 3 It is a flowchart of the cold start control method for the fuel cell system according to a specific example of the present invention;

[0028] Figure 4A block diagram of a vehicle according to an embodiment of the present invention;

[0029] Figure 5 A block diagram of a cold start control device for a fuel cell system according to an embodiment of the present invention. Detailed implementation manners

[0030] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0031] Currently, the commonly used low-temperature cold start methods are mainly divided into two modes: external heating and internal heating. The external heating mode mainly heats the coolant by setting an external PTC to achieve the purpose of rapid temperature rise. The internal heating mode mainly increases the concentration polarization of the cathode by reducing the cathode excess coefficient to increase the heat generation inside the stack and achieve the purpose of rapid temperature rise. However, the external PTC heating is simple and easy to operate, but the engine adds extra components and wiring harnesses, increasing the overall cost and insulation design of the whole machine. The internal heating mainly makes the cathode experience oxygen starvation by reducing the cathode excess coefficient, and makes the stack work near the short-circuit point to make the stack generate a large amount of waste heat and rapidly increase the temperature. This method is extremely effective for stack temperature rise, but it is a relatively dangerous behavior for the stack to work near the short-circuit point. Once the calculation of the hydrogen supply amount is incorrect, it will cause the stack to burn out or more serious accidents. And this solution has particularly high requirements for the fluid distribution uniformity of the stack and is difficult to control. Therefore, the present application proposes a cold start control method for a fuel cell system. For the current solutions that require adding PTC or anode and cathode gas heaters, the present application directly uses an air compressor for heating, heating the coolant and the cathode channel at the same time, promoting the coolant temperature rise, preventing the cathode channel from icing, and for the problem that the cathode is prone to icing during the low-temperature cold start of the fuel cell, the excess air coefficient under different low-temperature cold start currents is given, and the cathode purge is increased to prevent icing. For the risk that the cathode oxygen starvation method is difficult to control and may burn out the stack, the present application purges the cathode by heating the air and increasing the air excess coefficient, making the proton exchange membrane drier, and keeping the internal resistance of the stack at a relatively high value, so that a large amount of internal heat can be generated to heat the stack, which helps the system to rapidly warm up.

[0032] In an embodiment of the present invention, as Figure 2As shown, the fuel cell system may include an anode circuit, a cathode circuit, and a heat exchange circuit. In the anode circuit, high-pressure hydrogen exits from a high-pressure hydrogen cylinder and is depressurized by a pressure reducing valve, then enters a hydrogen injector. The hydrogen injector controls the flow rate and then enters the fuel cell stack (fuel cell pile) for reaction. The unreacted hydrogen and impurities exit the fuel cell stack and are separated by a separator (gas-water separator). The hydrogen is recycled back to the fuel cell stack inlet through a hydrogen circulation pump to participate in the reaction, and the separated water is drained through a nitrogen / water discharge valve. The main function of the nitrogen / water discharge valve is to discharge the water and impurities (mainly nitrogen) in the anode, enabling the fuel cell stack to operate efficiently and stably. In the cathode circuit, air enters an air compressor (air compressor) through an air filter (air filter) for compression, then enters an intercooler for cooling. After opening the inlet stack shut-off valve, it enters the fuel cell stack for reaction, and the exhaust gas after the reaction is discharged through a back pressure valve. By controlling the opening of the back pressure valve, the pressure and flow rate of the cathode can be controlled. The bypass valve plays a role in preventing the air compressor from surging (when the air compressor surges, opening the bypass valve can avoid surging). In the heat exchange circuit, one end of a water pump is respectively connected to the intercooler and the heating inlet of the fuel cell stack to transfer the heat after heat exchange in the intercooler to the fuel cell stack. That is to say, the water pressurized by the water pump enters the fuel cell stack in one way and enters the intercooler for heat exchange in the other way. The high-temperature and high-pressure gas compressed by the air compressor in the cathode circuit can exchange heat in the intercooler, raising the temperature of the coolant. That is, the air passing through the intercooler transfers most of the heat to the coolant through the intercooler, and the heat is conducted to the fuel cell stack through the heat exchange liquid circulation for heating, thereby increasing the temperature of the fuel cell stack and facilitating the rapid warming of the fuel cell stack. Among them, the rotational speed of the water pump can be set to about 2000 r / min. The rotational speed should not be too large or too small. If it is too large, it will take away the internal heat of the fuel cell stack, and it is not conducive to heat storage. If it is too small, there is a risk of excessive temperature inside the fuel cell stack. In addition, if the rotational speed is too small, the coolant flow rate in the intercooler is insufficient, which is also not conducive to the intercooler transferring the heat of the air to the fuel cell stack through the coolant for heating. In addition, the function of the deionizer can remove ions in the coolant to ensure the insulation of the fuel cell system.

[0033] The cold start control method, vehicle, and cold start control device of a fuel cell system proposed in an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0034] Figure 1 It is a flowchart of the cold start control method of a fuel cell system according to an embodiment of the present invention.

[0035] As Figure 1 shown, the cold start control method of the fuel cell system in an embodiment of the present invention may include the following steps:

[0036] S1, adjust the boost ratio of the air compressor, and determine the target air stoichiometry ratio according to the current density of the fuel cell stack.

[0037] S2, adjusting the air flow entering the air compressor based on the target air metering ratio, and controlling the air compressor according to the boost ratio.

[0038] S3, when the voltage of the fuel cell stack meets the preset voltage condition, the power supply current of the fuel cell stack is increased at a preset current rate until the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack meet the preset temperature condition, and it is determined that the cold start of the fuel cell stack is completed. The preset current rate can be determined according to actual conditions.

[0039] Specifically, during the cold start process of the fuel cell system, in order to prevent the cold start failure caused by low temperature, the pressure ratio of the air compressor can be adjusted. The pressure ratio refers to the ratio of the outlet pressure of the air compressor to the inlet pressure. Adjusting the pressure ratio of the air compressor can change the air pressure entering the fuel cell stack. The appropriate pressure ratio can ensure sufficient oxygen supply, thereby optimizing the electrochemical reaction. For example, the pressure ratio of the air compressor is adjusted by adjusting the speed of the air compressor. And the target air stoichiometric ratio is determined according to the current density of the fuel cell stack. The target air stoichiometric ratio represents the ratio of air (usually oxygen or air flow) to fuel (such as hydrogen) flow in the fuel cell stack. For example, the target air stoichiometric ratio is determined by a pre-set corresponding relationship. For example, the relationship between the current density of the fuel cell stack and the target air stoichiometric ratio is pre-determined. After the current density of the fuel cell stack is determined, the target air stoichiometric ratio can be obtained by directly calling the corresponding relationship. For example, when the fuel cell stack is cold-started, the fuel cell needs to heat up quickly to reach the normal operating temperature. However, an excessively high air stoichiometric ratio will cause too much air to enter, taking away more heat and slowing down the heating process. The air stoichiometric ratio can be adjusted according to the current density of the fuel cell stack to reduce the amount of air entering the fuel cell stack, thereby reducing heat loss and speeding up the temperature rise of the fuel cell stack.

[0040] Therefore, after the boost ratio and the target air metering ratio are determined, the air flow entering the air compressor can be adjusted according to the target air metering ratio, and the air compressor can be controlled according to the boost ratio. Figure 2As shown, the opening degree of the back pressure valve can be adjusted according to the flow rate shown by the flow meter, so as to adjust the air flow rate entering the air compressor. For example, in the case of a small flow rate, the opening degree of the back pressure valve can be increased. By increasing the opening degree of the back pressure valve, the back pressure of the system can be reduced, enabling more air to enter the air compressor, thereby increasing the flow rate. When the flow rate is large, reducing the opening degree of the back pressure valve will increase the back pressure of the system, restricting the amount of air entering the compressor, thereby reducing the flow rate. The supercharging ratio can be increased by increasing the rotational speed of the air compressor and decreased by reducing the rotational speed of the air compressor. In addition, after the air compressor is started, the air temperature rise at the inlet and outlet of the air compressor can be determined based on the absolute pressure at the outlet of the air compressor, the absolute pressure at the inlet of the air compressor, the actual inlet pressure of the air compressor, the adiabatic efficiency of the air compressor, and the air adiabatic index. For example, through the formula to determine the air temperature rise at the inlet and outlet of the air compressor. Among them, ΔT represents the air temperature rise, T cp,in represents the actual inlet temperature of the air compressor, which can be the ambient temperature, n cp represents the adiabatic efficiency of the air compressor, P cp,out represents the absolute pressure at the outlet of the air compressor (kPa), P cp,in represents the absolute pressure at the inlet of the air compressor (kPa). Thus, the outlet temperature of the air compressor can be determined as the sum of the ambient temperature and the air temperature rise based on the ambient temperature and the air temperature rise. As the air compressor starts, the air temperature at the outlet of the air compressor rises. The air passing through the intercooler transfers most of the heat to the coolant through the intercooler, and the heat is conducted to the fuel cell stack for heating along with the coolant circulation. The heat exchange power of the intercooler can be determined as: W = M 空气 *C 空气 *(T 空出 -T 中出 ) Among them, M 空气 is the air mass flow rate, C 空气 is the specific heat capacity of air, T 空出 is the air temperature at the outlet of the air compressor, T 中出 is the air temperature at the outlet of the intercooler. The intercooler takes away a large amount of heat from the air. The air coming out of the intercooler still has a certain residual temperature and enters the cathode to heat the fuel cell stack again.

[0041] As the fuel cell stack continues to operate, the voltage of the fuel cell stack will increase. When the voltage of the fuel cell stack meets the preset voltage condition, that is, meeting the preset voltage condition means that the fuel cell stack has reached a relatively stable operating state. Increase the supply current of the fuel cell stack at a preset current rate. For example, the preset current rate can be 0.03 A / s. That is, by gradually increasing the current, the temperature of the fuel cell stack can be slowly increased, avoiding thermal stress or other thermal management problems caused by too rapid temperature changes. And it can ensure that the system remains stable at each stage, avoiding voltage fluctuations or other performance instability problems caused by sudden increases in current.

[0042] Judge the inlet coolant temperature and outlet coolant temperature of the fuel cell stack. When the inlet coolant temperature and outlet coolant temperature of the fuel cell stack meet the preset temperature condition, it can be determined that the cold start of the fuel cell stack is completed. That is to say, when both the voltage and temperature of the fuel cell stack meet the preset conditions, it means that the fuel cell stack has reached a relatively stable operating state, and it can be confirmed that the cold start process is completed, and the system can enter the normal operation mode. In addition, when the fuel cell engine performs a low-temperature cold start, it can first perform a self-check. After the self-check is fault-free, it enters the ice-breaking mode to quickly and effectively remove the ice in the system interior and related pipelines, thereby restoring the normal operation of the fuel cell stack (that is, ensuring that all components that may freeze in the system can work properly).

[0043] Thus, the reliability of the low-temperature cold start of the fuel cell engine can be improved, the cold start time can be shortened, and the heating components can be reduced, saving costs and eliminating maintenance.

[0044] According to an embodiment of the present invention, adjusting the boost ratio of the air compressor includes: increasing the boost ratio of the air compressor to a target boost ratio. Wherein, the target boost ratio can be determined according to the actual situation.

[0045] Specifically, when adjusting the boost ratio of the air compressor, the boost ratio of the air compressor can be increased to the target boost ratio. For example, the target boost ratio of the air compressor can be 2.5. If the inlet pressure of the air compressor is 1 atmosphere, then the outlet pressure is 2.5 atmospheres. That is, high boost can increase the outlet temperature of the air compressor. Without changing the structure and accessories of the fuel cell engine, by controlling the boost ratio of the air compressor, using the higher outlet temperature of the air compressor to heat the coolant and the cathode, the fuel cell stack can be quickly heated up.

[0046] According to an embodiment of the present invention, determining the target air stoichiometry ratio according to the current density of the fuel cell stack includes: determining the current density range where the current density is located; determining the target air stoichiometry ratio based on the current density range, wherein different current density ranges correspond to different target air stoichiometry ratios.

[0047] Further, according to an embodiment of the present invention, the target air stoichiometric ratio is determined in the following manner:

[0048]

[0049] Wherein, y represents the target air stoichiometric ratio, and x represents the current density.

[0050] Specifically, when determining the target air stoichiometric ratio according to the current density of the fuel cell stack, the current density range where the current density is located can be determined. After determining the current density range, the target air stoichiometric ratio can be determined according to the current density range, and different current density ranges correspond to different target air stoichiometric ratios. For example, the target air stoichiometric ratio can be determined through a preset corresponding relationship. For example, the relationship between the current density range and the target air stoichiometric ratio length is determined in advance. After the current density range is determined, the corresponding relationship can be directly called to obtain the target air stoichiometric ratio. Specifically, the target air stoichiometric ratio can be determined through the above formula (1). For example, when the current density is less than 0.5 A / cm 2 That is, when the current density is in the current density range less than 0.5 A / cm 2 It can be determined that the target air stoichiometric ratio has a linear correspondence with the current density. When determining a current density, a target air stoichiometric ratio can be determined according to this linear relationship. When the current density is greater than or equal to 0.5 A / cm 2 That is, when the current density is in the current density range greater than or equal to 0.5 A / cm 2 It can be determined that the target air stoichiometric ratio is 4. In addition, the greater the current density, the lower the target air stoichiometric ratio; the smaller the current density, the higher the target air stoichiometric ratio. That is, in a fuel cell, the reaction between oxygen and hydrogen is a process of generating current. If the supply amount of air (oxygen) is too much, it will cause too much oxygen to be discharged without participating in the reaction, which will reduce the energy conversion efficiency. Therefore, as the current density increases, appropriately reducing the air stoichiometric ratio can ensure that the supply amount of oxygen matches the demand, thereby improving the overall energy conversion efficiency. Under high current conditions, if the air stoichiometric ratio remains unchanged or is too large, it may lead to excessive oxygen, which will not only reduce the efficiency, but may also cause oxidation reactions inside the battery, affecting the performance and life of the battery.

[0051] Thus, by designing the excess air coefficient under different low-temperature cold start currents, combined with the fact that the air at the outlet of the intercooler still has a certain temperature, purging the cathode to prevent icing, and the air with a certain temperature can also heat the cathode to accelerate the temperature rise of the stack and prevent icing. Moreover, setting a larger air stoichiometric ratio and purging with air at a certain temperature can keep the membrane electrode resistance at a larger value, increase the heat generation inside the fuel cell stack, and also accelerate the temperature rise of the stack.

[0052] It should be noted that the current density of the fuel cell stack refers to the current flowing through per unit area on the active area of the stack. When determining the current density, it can be determined according to the total current of the fuel cell stack and the total active area of the fuel cell stack.

[0053] According to an embodiment of the present invention, when the average single-cell voltage of the fuel cell stack is greater than or equal to a first preset voltage threshold and the minimum single-cell voltage is greater than or equal to a second preset voltage threshold, it is determined that the voltage of the fuel cell stack meets the preset voltage condition, where the first preset voltage threshold is greater than the second preset voltage threshold. The first preset voltage threshold and the second preset voltage threshold can be determined according to the actual situation.

[0054] Specifically, the magnitudes of the average single-cell voltage and the minimum single-cell voltage of the fuel cell stack are judged. When the average single-cell voltage of the fuel cell stack is greater than or equal to the first preset voltage threshold and the minimum single-cell voltage is greater than or equal to the second preset voltage threshold, it can be determined that the voltage of the fuel cell stack meets the preset voltage condition. For example, if the first preset voltage threshold is 800 mV and the second preset voltage threshold is 750 mV, when the average single-cell voltage of the fuel cell stack is greater than or equal to 800 mV and the minimum single-cell voltage is greater than 750 mV, it can be determined that the voltage of the fuel cell stack meets the preset voltage condition. That is to say, as the fuel cell stack operates, the voltage continuously increases. This condition ensures that each single-cell has sufficient voltage before the fuel cell stack starts to supply power, so as to ensure that the electrochemical reaction can proceed stably, and thus the supply current of the fuel cell stack can be increased at a preset current rate.

[0055] According to an embodiment of the present invention, when increasing the supply current of the fuel cell stack at a preset current rate, the method further includes: when the lowest single-cell voltage of the fuel cell stack is greater than or equal to a third preset voltage threshold, continuously increasing the supply current of the fuel cell stack at the preset current rate; when the lowest single-cell voltage of the fuel cell stack is greater than a fourth preset voltage threshold and less than the third preset voltage threshold, keeping the current supply current of the fuel cell stack unchanged; when the lowest single-cell voltage of the fuel cell stack is less than or equal to the fourth preset voltage threshold, stopping increasing the supply current of the fuel cell stack. The third preset voltage threshold and the fourth preset voltage threshold can be determined according to the actual situation.

[0056] Specifically, when increasing the supply current of the fuel cell stack at a preset current rate, in order to prevent the risk of burning out the fuel cell stack, it is necessary to protect the fuel cell stack. That is, the minimum single-cell voltage of the fuel cell stack can be determined, and the minimum single-cell voltage of the fuel cell stack is compared with a third preset voltage threshold and a fourth preset voltage threshold respectively. For example, the third preset voltage threshold can be 250 mV, and the fourth preset voltage threshold can be 200 mV. When the minimum single-cell voltage of the fuel cell stack is greater than or equal to the third preset voltage threshold, the supply current of the fuel cell stack can be continuously increased at the preset current rate, so that the voltage of the fuel cell stack continuously decreases. When the minimum single-cell voltage of the fuel cell stack is greater than 200 mV and less than 250 mV, it indicates that the current voltage of the fuel cell stack has dropped relatively low, and the current supply current of the fuel cell stack can be kept unchanged to avoid further voltage drop. When the minimum single-cell voltage of the fuel cell stack is less than 200 mV, it indicates that the current voltage of the fuel cell stack is low. If power continues to be supplied, there is a risk of burning out the fuel cell stack. Therefore, the protection program can be entered, that is, the increase in the supply current of the fuel cell stack is stopped, so that the fuel cell stack can operate safely and stably, while avoiding damage to the fuel cell stack due to too low voltage and extending the service life of the fuel cell stack.

[0057] According to an embodiment of the present invention, during the process of increasing the supply current of the fuel cell stack at a preset current rate, the cold start control method of the fuel cell system further includes: when the coolant temperature difference between the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack is greater than a preset temperature difference, controlling the rotational speed of the water pump to increase. The preset temperature difference can be determined according to the actual situation.

[0058] Specifically, during the process of increasing the supply current of the fuel cell stack at a preset current rate, the magnitude relationship between the coolant temperature difference between the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack and the preset temperature difference can be compared. For example, the preset temperature difference can be 30 degrees Celsius. When the coolant temperature difference is greater than 30 degrees Celsius, it indicates that the current coolant temperature difference is too large. In order to ensure a more balanced temperature distribution of the fuel cell stack, prevent local overheating, and ensure the safety of the fuel cell pair, the rotational speed of the water pump can be controlled to increase. Increasing the rotational speed of the water pump can increase the flow rate of the coolant, improve the cooling uniformity inside the fuel cell stack, improve the thermal efficiency and reliability, and ensure that the fuel cell stack operates in a safe and optimal performance state.

[0059] According to an embodiment of the present invention, when the outlet coolant temperature of the fuel cell stack is greater than a first preset temperature threshold and the inlet coolant temperature of the fuel cell stack is greater than a second preset temperature threshold, it is determined that the preset temperature condition is satisfied. The first preset temperature threshold and the second preset temperature threshold can be determined according to the actual situation.

[0060] Specifically, when increasing the power supply current of the fuel cell stack at a preset current rate, compare the magnitude relationship between the outlet coolant temperature of the fuel cell stack and the first preset temperature threshold, and compare the magnitude relationship between the inlet coolant temperature of the fuel cell stack and the second preset temperature threshold. For example, the first preset temperature threshold is 15 °C and the second preset temperature threshold is 0 °C. When the outlet coolant temperature of the fuel cell stack is greater than 15 °C and the inlet coolant temperature of the fuel cell stack is greater than 0 °C, it indicates that it can ensure that all components and reactions inside the fuel cell stack can operate within a sufficient temperature range. A temperature lower than 15 °C may affect the efficiency and performance of the fuel cell stack, and a coolant temperature greater than 0 °C avoids the freezing problem. If the inlet coolant temperature is lower than 0 °C, it may cause the coolant in the pipeline and the stack to freeze, thereby affecting the operation stability and safety of the system. Thus, it can be determined that the preset temperature condition is satisfied, and thus it is determined that the cold start of the fuel cell stack is completed.

[0061] The following will be combined with Figure 3 to describe the control method of the present invention.

[0062] As a specific example, the cold start control method of the fuel cell system of the present invention may include the following steps:

[0063] S101, when the fuel cell engine performs a low-temperature cold start, perform a self-check, and after the self-check is fault-free, enter the ice-breaking mode.

[0064] S102, adjust the boost ratio of the air compressor, determine the current density interval where the current density is located, and determine the target air stoichiometric ratio based on the current density interval.

[0065] S103, adjust the air flow rate entering the air compressor based on the target air stoichiometric ratio, and control the air compressor according to the boost ratio.

[0066] S104, determine whether the average single-cell voltage of the fuel cell stack is greater than or equal to the first preset voltage threshold and whether the minimum single-cell voltage is greater than or equal to the second preset voltage threshold. If so, execute step S105; if not, execute step S103.

[0067] S105, increase the power supply current of the fuel cell stack at a preset current rate.

[0068] S106, determine whether the lowest single-cell voltage of the fuel cell stack is greater than or equal to the third preset voltage threshold. If so, execute step S107; if not, execute step S108.

[0069] S107, continuously increase the power supply current of the fuel cell stack at a preset current rate.

[0070] S108, determine whether the minimum single - cell voltage of the fuel cell stack is greater than the fourth preset voltage threshold and less than the third preset voltage threshold. If yes, execute step S109; if no, execute step S110.

[0071] S109, keep the current power supply current of the fuel cell stack unchanged.

[0072] S110, determine whether the minimum single - cell voltage of the fuel cell stack is less than or equal to the fourth preset voltage threshold. If yes, execute step S111; if no, execute step S105.

[0073] S111, stop increasing the power supply current of the fuel cell stack and enter the protection program until the minimum single - cell voltage recovers to the value specified in the protection program and then continue to increase the current.

[0074] S112, determine whether the outlet coolant temperature of the fuel cell stack is greater than the first preset temperature threshold and the inlet coolant temperature of the fuel cell stack is greater than the second preset temperature threshold. If yes, execute step S113; if no, execute step S105.

[0075] S113, determine that the cold start of the fuel cell stack is completed.

[0076] In summary, according to the cold - start control method of the fuel cell system in the embodiments of the present invention, adjust the boost ratio of the air compressor, determine the target air metering ratio according to the current density of the fuel cell stack, adjust the air flow rate entering the air compressor based on the target air metering ratio, and control the air compressor according to the boost ratio. When the voltage of the fuel cell stack meets the voltage preset conditions, increase the power supply current of the fuel cell stack at a preset current rate until the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack meet the preset temperature conditions, and then determine that the cold start of the fuel cell stack is completed. Thus, this method can improve the reliability of the low - temperature cold start of the fuel cell engine, shorten the cold - start time, reduce the heating components, save costs and avoid maintenance.

[0077] Corresponding to the above - mentioned embodiments, the present invention also proposes a vehicle.

[0078] As Figure 4 shown, the vehicle 200 in the embodiments of the present invention may include: a memory 210, a processor 220, and a program stored on the memory 210 and executable on the processor 220. When the processor 220 executes the program, the above - mentioned cold - start control method of the fuel cell system is implemented.

[0079] According to the vehicle of the embodiment of the present invention, by executing the cold start control method of the above fuel cell system, the reliability of the low-temperature cold start of the fuel cell engine can be improved, the cold start time can be shortened, and the heating components can be reduced, saving costs and eliminating maintenance.

[0080] Corresponding to the above embodiment, the present invention also proposes a cold start control device for a fuel cell system.

[0081] As Figure 5 shown, the cold start control device 100 of the fuel cell system according to the embodiment of the present invention includes: an adjustment module 110, a determination module 120, and a control module 130.

[0082] Among them, the adjustment module 110 is used to adjust the boost ratio of the air compressor. The determination module 120 is used to determine the target air metering ratio according to the current density of the fuel cell stack. The control module 130 is used to adjust the air flow rate entering the air compressor based on the target air metering ratio and control the air compressor according to the boost ratio. The control module 130 is further used to increase the supply current of the fuel cell stack at a preset current rate when the voltage of the fuel cell stack meets the voltage preset condition, and determine that the cold start of the fuel cell stack is completed when the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack meet the preset temperature condition.

[0083] According to an embodiment of the present invention, the adjustment module 110 adjusts the boost ratio of the air compressor, specifically for: increasing the boost ratio of the air compressor to the target boost ratio.

[0084] According to an embodiment of the present invention, the determination module 120 determines the target air metering ratio according to the current density of the fuel cell stack, specifically for: determining the current density interval where the current density is located; determining the target air metering ratio based on the current density interval, where different current density intervals correspond to different target air metering ratios.

[0085] According to an embodiment of the present invention, the determination module 120 determines the target air metering ratio by the following method:

[0086]

[0087] Among them, y represents the target air metering ratio, and x represents the current density.

[0088] According to an embodiment of the present invention, the determination module 120 is further used to: determine that the voltage of the fuel cell stack meets the preset voltage condition when the average single cell voltage of the fuel cell stack is greater than or equal to the first preset voltage threshold and the minimum single cell voltage is greater than or equal to the second preset voltage threshold, where the first preset voltage threshold is greater than the second preset voltage threshold.

[0089] According to an embodiment of the present invention, the control module 130 is further configured to: when increasing the supply current of the fuel cell stack at a preset current rate, if the minimum single-cell voltage of the fuel cell stack is greater than or equal to a third preset voltage threshold, continuously increase the supply current of the fuel cell stack at the preset current rate; if the minimum single-cell voltage of the fuel cell stack is greater than a fourth preset voltage threshold and less than the third preset voltage threshold, keep the current supply current of the fuel cell stack unchanged; if the minimum single-cell voltage of the fuel cell stack is less than or equal to the fourth preset voltage threshold, stop increasing the supply current of the fuel cell stack.

[0090] According to an embodiment of the present invention, the control module 130 is further configured to: during the process of increasing the supply current of the fuel cell stack at a preset current rate, if the coolant temperature difference between the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack is greater than a preset temperature difference, control the rotation speed of the water pump to increase.

[0091] According to an embodiment of the present invention, the determination module 120 is further configured to: if the outlet coolant temperature of the fuel cell stack is greater than a first preset temperature threshold and the inlet coolant temperature of the fuel cell stack is greater than a second preset temperature threshold, determine that the preset temperature condition is satisfied.

[0092] It should be noted that for the details not disclosed in the cold start control device of the fuel cell system according to the embodiments of the present invention, please refer to the details disclosed in the cold start control method of the fuel cell system according to the embodiments of the present invention, and specific details are not elaborated here.

[0093] For the cold start control device of the fuel cell system according to the embodiments of the present invention, the adjustment module is used to adjust the boost ratio of the air compressor; the determination module is used to determine the target air metering ratio according to the current density of the fuel cell stack, the control module is used to adjust the air flow rate entering the air compressor based on the target air metering ratio and control the air compressor according to the boost ratio, and the control module is further used to increase the supply current of the fuel cell stack at a preset current rate when the voltage of the fuel cell stack meets the voltage preset condition, and determine that the cold start of the fuel cell stack is completed until the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack meet the preset temperature condition. Thus, the device can improve the reliability of the low-temperature cold start of the fuel cell engine, shorten the cold start time, reduce the heating components, save costs and avoid maintenance.

[0094] Note that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a definite sequence list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device), or used in combination with these instruction execution systems, apparatus, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. More specific examples (non-exhaustive list) of the computer-readable medium include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer diskette (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can even be paper or other suitable medium on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpretation, or otherwise processing it in a suitable manner if necessary, and then storing it in a computer memory.

[0095] It should be understood that various parts of the present invention can be implemented by hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

[0096] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0097] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0098] In the present invention, unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0099] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A cold start control method for a fuel cell system, characterized in that: The fuel cell system comprises a fuel cell stack, an intercooler, an air compressor, and a water pump. The cathode inlet of the fuel cell stack is connected to the air compressor through the intercooler. One end of the water pump is respectively connected to the intercooler and the heating inlet of the fuel cell stack to transfer the heat after the heat exchange of the intercooler to the fuel cell stack. The method comprises: adjusting a pressure increase ratio of the air compressor and determining a target air metering ratio according to a current density of the fuel cell stack; adjusting the air flow entering the air compressor based on the target air metering ratio, and controlling the air compressor according to the boost ratio; When the voltage of the fuel cell stack meets a preset voltage condition, the power supply current of the fuel cell stack is increased at a preset current rate until the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack meet preset temperature conditions, and it is determined that the cold start of the fuel cell stack is completed; Wherein: the boost ratio refers to the ratio of the outlet pressure to the inlet pressure of the air compressor, and the target air metering ratio refers to the ratio of the air flow rate to the fuel cell stack; The step of determining a target air stoichiometric ratio according to the current density of the fuel cell stack comprises: Determining a current density interval in which the current density is located; Determining the target air stoichiometric ratio based on the current density interval, wherein different current density intervals correspond to different target air stoichiometric ratios; The target air stoichiometric ratio is determined by: Wherein, y represents the target air stoichiometry, x represents the current density, and the unit of current density is A / cm 2 .

2. The cold start control method of the fuel cell system according to claim 1, characterized in that: The step of adjusting the pressure increase ratio of the air compressor comprises: The pressure increase ratio of the air compressor is increased to a target pressure increase ratio.

3. The cold start control method of the fuel cell system according to claim 1, characterized in that: When the average cell voltage of the fuel cell stack is greater than or equal to a first preset voltage threshold and the minimum cell voltage is greater than or equal to a second preset voltage threshold, it is determined that the voltage of the fuel cell stack meets the preset voltage condition, wherein the first preset voltage is greater than the second preset voltage threshold.

4. The cold start control method of the fuel cell system according to claim 1, characterized in that: When increasing the power supply current of the fuel cell stack at a preset current rate, the method further includes: when the lowest cell voltage of the fuel cell stack is greater than or equal to a third preset voltage threshold, continuously increasing the power supply current of the fuel cell stack at the preset current rate; When the lowest cell voltage of the fuel cell stack is greater than a fourth preset voltage threshold and less than the third preset voltage threshold, maintaining the current power supply current of the fuel cell stack unchanged; When the lowest cell voltage of the fuel cell stack is less than or equal to the fourth preset voltage threshold, the increase of the power supply current of the fuel cell stack is stopped.

5. The cold start control method of the fuel cell system according to claim 1, characterized in that: In the process of increasing the supply current of the fuel cell stack at a preset current rate, the method further includes: When the coolant temperature difference between the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack is greater than a preset temperature difference, the rotation speed of the water pump is controlled to increase.

6. The cold start control method of the fuel cell system according to claim 1, characterized in that: In a case where the outlet coolant temperature of the fuel cell stack is greater than a first preset temperature threshold and the inlet coolant temperature of the fuel cell stack is greater than a second preset temperature threshold, it is determined that the preset temperature condition is met.

7. A vehicle, characterized in that: include: A memory, a processor, and a program stored in the memory and executable on the processor, wherein when the processor executes the program, the cold start control method for the fuel cell system according to any one of claims 1 to 6 is implemented.

8. A cold start control device for a fuel cell system, implementing the cold start control method for a fuel cell system according to any one of claims 1 to 6, characterized in that: The fuel cell system comprises a fuel cell stack, an intercooler, an air compressor, and a water pump. The cathode inlet of the fuel cell stack is connected to the air compressor through the intercooler. One end of the water pump is respectively connected to the intercooler and the heating inlet of the fuel cell stack to transfer the heat after the heat exchange of the intercooler to the fuel cell stack. The device comprises: A regulating module, used for regulating the pressure ratio of the air compressor; A determination module, configured to determine a target air stoichiometric ratio according to a current density of the fuel cell stack; a control module, configured to adjust the air flow entering the air compressor based on the target air metering ratio, and control the air compressor according to the boost ratio; The control module is also used to increase the power supply current of the fuel cell stack at a preset current rate when the voltage of the fuel cell stack meets a preset voltage condition, and to determine that the cold start of the fuel cell stack is completed when the inlet coolant temperature and the outlet coolant temperature of the fuel cell stack meet preset temperature conditions.

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