Starting method of fuel cell system and vehicle with same

Abstract

The invention relates to a starting method of a fuel cell system and a vehicle with the fuel cell system. Comprising the following steps: in response to a starting instruction, acquiring the temperature of a cooling liquid outlet of a galvanic pile, heating the galvanic pile through a cooling liquid loop when the temperature is lower than a preset temperature, controlling a hydrogen loop and an oxygen loop of the fuel cell system to be in corresponding working states, and controlling a second output end and an air bypass valve to be in an open state, the first output end and the third output end are in a closed state, one end of the air bypass valve is connected with the output end of the intercooler, and the other end of the air bypass valve is connected with the oxygen output end of the electric pile; and obtaining the temperature of the output end of the air compression assembly and the hydrogen outlet temperature of the electric pile, and controlling the fuel cell system to start according to the temperature of the output end of the air compression assembly and the hydrogen outlet temperature. Therefore, the problems that in the prior art, the heating efficiency is low, the energy loss is large, the local temperature difference is too large, and cooperative regulation and control over the hydrogen and the air side are lacked are solved, and the safe, rapid and energy-saving cold start process is achieved.

Description

Technical Field

[0001] This application relates to the field of vehicle technology, and in particular to a method for starting a fuel cell system and a vehicle having the same. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) face severe cold start difficulties in cold environments due to problems such as electrolyte membrane dehydration, decreased electrochemical reaction activity, and internal icing caused by low temperatures.

[0003] In related technologies, the use of external heaters, self-heating of fuel cell stacks, and circulating water heating have solved the cold start problem to some extent.

[0004] However, the related technologies suffer from problems such as reliance on external heat sources or slow heat generation by the fuel cell stack itself, the need to consume a large amount of auxiliary energy to reach the target temperature, uneven heating, and focusing only on preheating the gas on one side. These problems result in low heating efficiency, large energy loss, excessive local temperature differences, and a lack of a coordinated control mechanism for the hydrogen and air sides, which urgently need to be solved. Summary of the Invention

[0005] This application provides a starting method for a fuel cell system and a vehicle having the same, to solve the problems of low heating efficiency, large energy loss, excessive local temperature difference, and lack of coordinated control of hydrogen and air sides in related technologies. By adding a four-way gas solenoid valve and a shell-and-tube counter-flow gas-to-gas heat exchanger, the temperature, pressure, and flow rate parameters of the gases on both sides can be precisely controlled. Combined with the short-time closed-loop operation strategy of the fuel cell stack, the uniform heating of the fuel cell stack can be completed in a very short time, avoiding freezing, dehydration, and thermal stress damage, thereby achieving safe, fast, and energy-saving cold start, improving the heating rate, and reducing energy consumption to a certain extent.

[0006] To achieve the above objectives, a first aspect of this application proposes a startup method for a fuel cell system. The oxygen circuit of the fuel cell system includes a four-way valve. The input terminal of the four-way valve is connected to the output terminal of an air compressor assembly. The first output terminal of the four-way valve is connected to an oxygen input terminal. The second output terminal of the four-way valve is connected to the oxygen input terminal via an intercooler. The third output terminal of the four-way valve is connected to a hydrogen preheating assembly. The method includes the following steps: In response to the power-on command, the coolant outlet temperature of the fuel cell stack is obtained; When the coolant outlet temperature is lower than the preset temperature, the fuel cell stack is heated through the coolant circuit of the fuel cell system. The hydrogen circuit and the oxygen circuit of the fuel cell system are controlled to be in the corresponding working state, and the second output terminal and the air bypass valve are both in the open state, while the first output terminal and the third output terminal are in the closed state. One end of the air bypass valve is connected to the output terminal of the intercooler, and the other end of the air bypass valve is connected to the oxygen output terminal of the fuel cell stack. The temperature at the output terminal of the air compressor assembly and the hydrogen outlet temperature of the fuel cell stack are obtained, and the fuel cell system is started according to the temperature at the output terminal of the air compressor assembly and the hydrogen outlet temperature.

[0007] According to one embodiment of this application, controlling the start-up of the fuel cell system based on the temperature at the output terminal of the air compressor assembly and the hydrogen outlet temperature includes: Calculate the first difference between the temperature at the output end of the air compressor component and the temperature at the hydrogen outlet, and determine whether the first difference is less than a preset threshold. If the first difference is less than the preset threshold, the load of the vehicle is controlled to perform a load current operation, the first output terminal is controlled to be in the open state, and the second output terminal, the third output terminal and the air bypass valve are all controlled to be in the closed state, and the current load current is obtained. The water production of the fuel cell stack is calculated based on the current load current, and the ice capacity of the gas diffusion layer of the fuel cell stack is calculated based on the water production. Based on the ice capacity of the gas diffusion layer, it is determined whether the fuel cell system has completed the cold start. If the fuel cell system completes a cold start, the system obtains the vehicle's total power requirement, controls the fuel cell system to start, and outputs power according to the vehicle's total power requirement.

[0008] According to one embodiment of this application, the water production capacity of the fuel cell stack is: ; in, The water production of the fuel cell stack is expressed in grams. The number of individual pieces in the fuel cell stack; n The number of electrons transferred in the electrochemical reaction of the stack is 2; F The Faraday constant is 96500 C / mol; It is a function of the change of current with time from 0 to t (s); The molar mass of water is 18 g / mol.

[0009] According to one embodiment of this application, the ice capacity of the gas diffusion layer is: ; in, The ice capacity of the gas diffusion layer. This represents the volume fraction of water converted into ice. This is the instantaneous operating current of the fuel cell.

[0010] According to one embodiment of this application, determining whether the fuel cell system has completed a cold start based on the ice capacity of the gas diffusion layer includes: Determine whether the ice capacity of the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer; If the ice capacity of the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer, the fuel cell system is determined to have completed a cold start when the coolant outlet temperature of the fuel cell stack reaches the target temperature.

[0011] According to one embodiment of this application, after determining whether the ice capacity of the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer, the method further includes: If the ice capacity of the gas diffusion layer is greater than or equal to the maximum allowable ice capacity of the gas diffusion layer, then calculate the second difference between the ice capacity of the gas diffusion layer and the maximum allowable ice capacity of the gas diffusion layer, and calculate the upper limit of the slope and the upper limit of the load current based on the second difference. Based on the upper limit of the slope of the load current and the upper limit of the current, the load current of the fuel cell is adjusted, and the adjusted load current is used as the current load current. The step of recalculating the water production of the fuel cell based on the current load current is repeated until the new ice capacity of the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer.

[0012] According to one embodiment of this application, after determining whether the first difference is less than a preset threshold, the method further includes: If the difference is greater than or equal to a preset threshold, the third output terminal is controlled to be in the open state, and the second output terminal and the first output terminal are controlled to be in the closed state, so as to heat the hydrogen in the hydrogen supply circuit of the hydrogen preheating component. Obtain the temperature at the output terminal of the new air compressor assembly and the oxygen output terminal temperature of the fuel cell stack; If the temperature difference between the output terminal of the new air compressor component and the output terminal of the oxygen component is greater than or equal to the preset threshold, then the first output terminal and the third output terminal are controlled to be in the open state, and the second output terminal is controlled to be in the closed state, and the step of controlling the load of the vehicle to perform the load current operation is executed.

[0013] According to one embodiment of this application, heating the fuel cell stack via the coolant circuit of the fuel cell system includes: The thermostat of the fuel cell system is adjusted to a first state to form the coolant circuit through the stack coolant output terminal, thermostat, heater, water pump, and stack coolant input terminal; The water pump and heater of the fuel cell system are both in operation to heat the coolant in the coolant circuit, and the heated coolant heats the fuel cell stack.

[0014] According to one embodiment of this application, after obtaining the coolant outlet temperature of the fuel cell stack, the method further includes: When the coolant outlet temperature is greater than or equal to the preset temperature, the first and third output terminals of the four-way valve are closed, and the vehicle's total power demand is obtained. The system controls the start-up of the fuel cell system and outputs power according to the power requirements of the vehicle.

[0015] According to the fuel cell system startup method proposed in this application, after receiving the startup command, the fuel cell system obtains the coolant outlet temperature of the stack. If the temperature is lower than a preset temperature, the stack is heated through the coolant circuit. The hydrogen and oxygen circuits are controlled to be in working state, and the second output terminal of the four-way valve and the air bypass valve are controlled to be in the open state. The startup of the fuel cell system is controlled according to the temperature of the air compressor component output terminal and the hydrogen outlet temperature of the stack. This solves the problems of low heating efficiency, large energy loss, excessive local temperature difference, and lack of coordinated control of hydrogen and air sides in related technologies. By adding a four-way gas solenoid valve and a shell-and-tube counter-current gas-to-gas heat exchanger, the temperature, pressure, and flow rate parameters of the gases on both sides can be precisely controlled. Combined with the short-time closed-loop operation strategy of the stack, the stack can be uniformly heated in a very short time, avoiding freezing, dehydration, and thermal stress damage. This achieves safe, fast, and energy-saving cold start, improves the heating rate, and reduces energy consumption to a certain extent.

[0016] To achieve the above objectives, a second aspect of this application provides a vehicle comprising: a memory, a processor, and a computer program stored in the memory and capable of running on the processor, wherein the processor executes the program to implement the fuel cell system startup method as described in the above embodiments.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a schematic diagram of a fuel cell system provided according to an embodiment of this application; Figure 2 This is a flowchart of a startup method for a fuel cell system according to an embodiment of this application; Figure 3 This is a flowchart of a startup method for a fuel cell system according to an embodiment of this application; Figure 4 This is a structural schematic diagram of a vehicle provided according to an embodiment of this application. Detailed Implementation

[0019] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying 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 accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0020] The following description, with reference to the accompanying drawings, describes a method for starting a fuel cell system according to an embodiment of this application, and a vehicle having such a system.

[0021] Before introducing the start-up method of the fuel cell system according to the embodiments of this application, let me briefly introduce the fuel cell system according to the embodiments of this application.

[0022] Specifically, such as Figure 1 As shown, Figure 1This is a schematic diagram of a fuel cell system according to an embodiment of this application. The fuel cell system includes: a fuel cell stack 1, a proportional valve and ejector assembly 2, a hydrogen circulation pump 3, a fuel cell stack hydrogen outlet temperature sensor 4, a shell-and-tube counter-current gas-to-gas heat exchanger 5, an air compressor 6, an air compressor outlet gas temperature sensor 7, a four-way gas solenoid valve 8, an intercooler 9, an air bypass valve 10, a fuel cell stack air outlet temperature sensor 11, a cathode water distributor 12, a water pump 13, a PTC heater 14, a thermostat 15, and a fuel cell stack coolant outlet water temperature sensor 16. The gas four-way solenoid valve 8 includes a first input terminal 81, a first output terminal 84, a second output terminal 83, and a third output terminal 82; the fuel cell stack 1 includes a hydrogen input terminal, a hydrogen output terminal, an oxygen input terminal, an oxygen output terminal, a coolant input terminal, and a coolant output terminal; the input terminal of the coolant circulation system is connected to the coolant output terminal, and the output terminal of the coolant circulation system is connected to the coolant input terminal; the output terminal of the hydrogen preheating component is connected to the hydrogen input terminal, and the input terminal of the hydrogen preheating component is connected to the hydrogen output terminal; the oxygen supply component includes an air compressor 6, a gas four-way solenoid valve 8, and an intercooler 9. The first input terminal 81 of the gas four-way solenoid valve 8 is connected to the output terminal of the air compressor 6, the first output terminal 84 of the gas four-way solenoid valve 8 is connected to the oxygen input terminal, the second output terminal 83 of the gas four-way solenoid valve 8 is connected to the oxygen input terminal through the intercooler 9, the third output terminal 82 of the gas four-way solenoid valve 8 is connected to the hydrogen preheating component, and the input terminal of the oxygen supply component is connected to the second gas output terminal.

[0023] Furthermore, Figure 2 This is a flowchart of a startup method for a fuel cell system according to an embodiment of this application.

[0024] like Figure 2 As shown, the start-up method of this fuel cell system includes the following steps: In step S201, in response to the power-on command, the coolant outlet temperature of the fuel cell stack is obtained.

[0025] Specifically, the vehicle sends a command to start the fuel cell system. In response to the start command, the fuel cell system performs high-voltage pre-charging and low-voltage configuration. After completion, the temperature acquisition device (i.e., the coolant outlet temperature sensor 16) is used to detect the coolant outlet temperature of the fuel cell stack 1 and obtain the coolant outlet temperature of the fuel cell stack 1.

[0026] In step S202, when the coolant outlet temperature is lower than the preset temperature, the fuel cell stack 1 is heated through the coolant circuit of the fuel cell system.

[0027] Optionally, in some embodiments, heating the fuel cell stack 1 through the coolant circuit of the fuel cell system includes: adjusting the thermostat 15 of the fuel cell system to a first state to form a coolant circuit through the coolant output terminal of the fuel cell stack, the thermostat 15, the heater, the water pump 13 and the coolant input terminal of the fuel cell stack; controlling the water pump 13 and the heater of the fuel cell system to be in a working state to heat the coolant in the coolant circuit, and heating the fuel cell stack 1 through the heated coolant.

[0028] The preset temperature can be a temperature set by the user, a temperature obtained through a limited number of experiments, or a temperature obtained through a limited number of computer simulations. The first state refers to a valve opening / closing configuration of the thermostat in the fuel cell system. The preset temperature can be 0°C, and the heater can be a PTC heater 14 (Positive Temperature Coefficient Heater).

[0029] Specifically, based on the coolant outlet temperature of the fuel cell stack obtained in step S101, this embodiment determines that the fuel cell system is undergoing a cold start at low temperature when the coolant outlet temperature is lower than a preset temperature. During the cold start phase of the fuel cell system, this embodiment drives the thermostat 15 to a first state. In this state, the internal valve structure of the thermostat 15 opens the closed coolant circuit connecting the fuel cell stack coolant outlet, thermostat 15, heater 14, water pump 13, and the fuel cell stack coolant outlet. At the same time, the second state of the thermostat 15 is closed, cutting off the connection between the coolant and other branches such as the radiator, ensuring that the coolant circulates only within the target circuit. The water pump 13 and heater 14 are maintained in operation. The water pump 13 continues to operate to provide circulation power for the coolant. After the heater 14 starts working, it releases heat and exchanges heat with the coolant, causing the coolant temperature in the circuit to rise. The heated coolant enters the fuel cell stack 1 through the fuel cell stack coolant inlet, causing the interior of the fuel cell stack 1 to heat up.

[0030] In step S203, the hydrogen circuit and oxygen circuit of the control fuel cell system are both in the corresponding working state, and the second output terminal and the air bypass valve 10 are both in the open state, while the first output terminal and the third output terminal are in the closed state. One end of the air bypass valve 10 is connected to the output terminal of the intercooler 9, and the other end of the air bypass valve 10 is connected to the oxygen output terminal of the fuel cell stack 1.

[0031] The oxygen circuit of the fuel cell system includes a four-way valve 8 (i.e., a four-way gas solenoid valve). The input end of the four-way valve 8 is connected to the output end of the air compressor assembly (i.e., the air compressor 6). The first output end of the four-way valve 8 is connected to the oxygen input end. The second output end of the four-way valve 8 is connected to the oxygen input end through the intercooler 9. The third output end of the four-way valve 8 is connected to the hydrogen preheating assembly.

[0032] Specifically, in this embodiment, the proportional valve 2 is opened to conduct the hydrogen supply channel and regulate the hydrogen input flow rate; the ejector assembly 2' is opened to achieve efficient mixing and directional delivery of hydrogen and circulating hydrogen; and the hydrogen circulation pump 3 is started to provide circulating power for the hydrogen circuit. Through the coordinated operation of the above components, the hydrogen circuit of the fuel cell system is established, and the opening degree of the proportional valve 2 and the operating speed of the hydrogen circulation pump 3 are dynamically adjusted to establish the hydrogen pressure of the fuel cell stack 1. One end of the air bypass valve 10 is connected to the output end of the intercooler 9, and the other end is connected to the oxygen output end of the fuel cell stack. The core component of the oxygen circuit is the four-way valve 8. The input end of the four-way valve 8 is connected to the output end of the air compressor assembly 6. The first output end is directly connected to the oxygen input end of the fuel cell stack. The second output end is connected to the oxygen input end of the fuel cell stack after being cooled by the intercooler 9. The third output end is connected to the second input end of the heat exchange assembly (i.e., the shell-and-tube counter-current gas-to-gas heat exchanger 5), forming a multi-path configuration architecture for the oxygen circuit. Among them, the air compressor assembly 6 contains an expander.

[0033] In this embodiment, the first output terminal 84 of the four-way valve 8 is closed to cut off the direct connection between the air compressor assembly 6 and the oxygen input terminal of the fuel cell stack; the second output terminal 83 of the four-way valve 8 is opened to allow compressed air to enter the fuel cell stack 1 after being cooled by the intercooler 9; the third output terminal 82 of the four-way valve 8 is closed to prevent oxygen from flowing into the hydrogen preheating assembly side and affecting the stability of the hydrogen circuit; the air bypass valve 10 is opened to enable the communication between the compressed air after passing through the intercooler 9 and the oxygen exhaust from the fuel cell stack, thus establishing the system air flow.

[0034] In step S204, the temperature of the output terminal of the air compressor assembly 6 and the hydrogen outlet temperature of the fuel cell stack 1 are obtained, and the fuel cell system is started according to the temperature of the output terminal of the air compressor assembly 6 and the hydrogen outlet temperature.

[0035] Specifically, the temperature at the output of the air compressor assembly 6 and the hydrogen outlet temperature of the fuel cell stack 1 are obtained by a temperature acquisition device (i.e., air compressor outlet gas temperature sensor 7) at the output end of the air compressor assembly 6 and a temperature acquisition device (i.e., fuel cell stack hydrogen outlet temperature sensor 4) at the hydrogen outlet of the fuel cell stack 1, and the start-up of the fuel cell system is controlled based on the temperature at the output of the air compressor assembly 6 and the hydrogen outlet temperature.

[0036] Optionally, in some embodiments, controlling the start-up of the fuel cell system based on the temperature at the output terminal of the air compressor assembly 6 and the hydrogen outlet temperature includes: calculating a first difference between the temperature at the output terminal of the air compressor assembly 6 and the hydrogen outlet temperature, and determining whether the first difference is less than a preset threshold; if the first difference is less than the preset threshold, controlling the vehicle load to perform a load-drawing current operation, controlling the first output terminal to be in an open state, and controlling the second output terminal, the third output terminal, and the air bypass valve 10 to be in a closed state, and obtaining the current load-drawing current; calculating the water production of the fuel cell stack 1 based on the current load-drawing current, calculating the ice capacity of the gas diffusion layer of the fuel cell stack 1 based on the water production, and determining whether the fuel cell system has completed a cold start based on the ice capacity of the gas diffusion layer; if the fuel cell system has completed a cold start, obtaining the vehicle's total power demand, controlling the start-up of the fuel cell system, and outputting power according to the vehicle's total power demand.

[0037] Optionally, in some embodiments, the water production capacity of the fuel cell stack 1 is: ; in, The water production of the fuel cell stack is expressed in grams. The number of individual cells in the fuel cell stack; n The number of electrons transferred in the electrochemical reaction of the fuel cell stack is 2; F The Faraday constant is 96500 C / mol; The current is a function of time from 0 to t, with units of seconds (s). The molar mass of water is 18 g / mol.

[0038] Optionally, in some embodiments, the ice capacity of the gas diffusion layer is: ; in, This refers to the ice capacity of the gas diffusion layer. This represents the volume fraction of water converted into ice. This is the instantaneous operating current of the fuel cell.

[0039] Optionally, in some embodiments, determining whether the fuel cell system has completed a cold start based on the ice capacity of the gas diffusion layer includes: determining whether the ice capacity of the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer; if the ice capacity of the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer, then when the coolant outlet temperature of the fuel cell stack reaches the target temperature, it is determined that the fuel cell system has completed a cold start.

[0040] The preset threshold can be a user-defined threshold, a threshold obtained through a limited number of experiments, or a threshold obtained through a limited number of computer simulations. The load current refers to the current actively drawn by the fuel cell system through an external load during the testing, startup, or operation phases.

[0041] Specifically, in this embodiment, the first difference between the outlet gas temperature of the air compressor assembly 6 and the hydrogen outlet temperature of the fuel cell stack is calculated. It is then determined whether the first difference is less than a preset threshold. If the first difference is less than the preset threshold, the heater 14 continues to operate until the fuel cell coolant outlet temperature reaches the fuel cell stack 1's self-starting target temperature, and the vehicle load is controlled to perform a load-pull current operation. Simultaneously, the states of the oxygen circuit four-way valve 8 and the air bypass valve 10 are adjusted: the air compressor assembly 6 is maintained in operation, the first output terminal 84 of the four-way valve 8 is opened, and the second output terminal 83, the third output terminal 82 of the four-way valve 8, and the air bypass valve 10 are closed. This switches the oxygen circuit to a direct connection between the output terminal of the air compressor assembly 6, the first output terminal 84 of the four-way valve 8, and the oxygen input terminal of the fuel cell stack. The load is increased to the target current at the fuel cell stack 1's maximum allowable low-temperature load-pull current slope, and the real-time value of the current load-pull current is collected.

[0042] This embodiment of the application calculates the water production of fuel cell 1 in real time based on the collected current load current and the formula for calculating the water production of fuel cell 1; then, based on the calculated water production of the fuel cell 1 and the formula for calculating the freezing rate of liquid water below the freezing point, the amount of ice in the gas diffusion layer is calculated. The formula for calculating the freezing rate of liquid water below the freezing point is as follows: ; in, This represents the volume fraction of water converted into ice. For solidification rate, The porosity of the gas diffusion layer. For liquid water saturation, It is the effective presence factor of liquid water.

[0043] This application's embodiments determine whether the fuel cell system has completed a cold start based on the ice capacity of the gas diffusion layer.

[0044] If the amount of ice in the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer, the embodiments of this application maintain the current self-starting state parameter conditions of the fuel cell stack 1 until the coolant outlet temperature of the fuel cell stack reaches the target value that allows for free load-bearing. After this, the fuel cell cold start is successful, the vehicle's total power demand is obtained, the fuel cell system is controlled to start, and power output is performed according to the vehicle's total power demand.

[0045] Therefore, the waste heat of the high-temperature gas from the air compressor assembly outlet is used to heat both sides of the hydrogen and air sides, thereby improving the overall energy utilization rate of the fuel cell system. After the gas on both sides of the hydrogen and air sides is heated, it enters the core of the fuel cell stack to carry out chemical reactions. At the same time, the heat is transferred to the core material to assist the rapid heating of the internal structure of the fuel cell stack and accelerate the cold start time of the fuel cell system. During the heater operation and the heat generation stage of the fuel cell stack reaction, the accelerated heating of the core will shorten the heater operation time or power, thereby reducing the consumption of the vehicle's power battery.

[0046] Furthermore, in order to avoid the gas diffusion layer ice capacity exceeding the maximum allowable range, which would damage the stack performance or cause cold start failure, the embodiments of this application also require regulation.

[0047] Optionally, in some embodiments, after determining whether the ice capacity of the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer, the method further includes: if the ice capacity of the gas diffusion layer is greater than or equal to the maximum allowable ice capacity of the gas diffusion layer, calculating a second difference between the ice capacity of the gas diffusion layer and the maximum allowable ice capacity of the gas diffusion layer, and calculating the upper limit of the slope and the upper limit of the current of the load current based on the second difference; adjusting the load current of the fuel cell based on the upper limit of the slope and the upper limit of the current of the load current, and using the adjusted load current as the current load current, and recalculating the water production of the fuel cell based on the current load current, until the new ice capacity of the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer.

[0048] Specifically, if the ice content in the gas diffusion layer is greater than or equal to the maximum allowable ice capacity of the gas diffusion layer, this embodiment combines the calculated second difference between the actual ice content in the gas diffusion layer and the maximum allowable ice capacity of the gas diffusion layer. It then uses the formulas for calculating the water production of the fuel cell stack, the formula for calculating the ice capacity of the gas diffusion layer, and the formula for calculating the freezing rate of liquid water below the freezing point to calculate and reduce the upper limit of the fuel cell stack self-starting load current slope and the upper limit of the current corresponding to the actual ice content in the gas diffusion layer. The current and load slope are adjusted through a closed-loop program, and the ice content in the gas diffusion layer and the self-starting status of fuel cell stack 1 are calculated and monitored in real time until the ice capacity of the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer.

[0049] This avoids the problem of stack performance being damaged or cold start failure caused by the gas diffusion layer ice capacity exceeding the maximum allowable range.

[0050] Furthermore, when the first difference is greater than or equal to a preset threshold, the embodiments of this application perform regulation.

[0051] Optionally, in some embodiments, after determining whether the first difference is less than a preset threshold, the method further includes: if the difference is greater than or equal to the preset threshold, controlling the third output terminal 82 to be in the open state and controlling the second output terminal 83 and the first output terminal 84 to be in the closed state, so as to heat the hydrogen in the hydrogen supply circuit of the hydrogen preheating component; obtaining the temperature of the new air compressor component 6 output terminal and the oxygen output terminal temperature of the fuel cell stack 1; if the difference between the temperature of the new air compressor component 6 output terminal and the oxygen output terminal temperature is greater than or equal to the preset threshold, controlling the first output terminal 84 and the third terminal 82 to be in the open state and controlling the second terminal 83 to be in the closed state, and performing the step of controlling the load of the vehicle to perform a load current operation.

[0052] Specifically, if the first difference is greater than or equal to the preset threshold, the air compressor assembly 6 is kept running, the first output terminal 84 and the second output terminal 83 of the four-way valve 8 are closed, and the third output terminal 82 is opened, so that high-temperature air enters the outer tube channel of the shell-and-tube counter-current gas-to-gas heat exchanger 5 to heat the hydrogen in the inner tube, and then circulates it into the internal part of the fuel cell stack 1 through the hydrogen circulation pump 3 to assist in heating the core.

[0053] The output temperatures of the air compressor assembly 6 and the oxygen output temperature of the fuel cell stack 1 are obtained through the temperature acquisition device 7 at the output end of the air compressor assembly and the temperature acquisition device (fuel cell stack air outlet temperature sensor 11) at the oxygen output end of the fuel cell stack. The difference between the output temperatures of the air compressor assembly 6 and the oxygen output temperature of the fuel cell stack 1 is calculated. If the difference is less than a preset threshold, the load of the vehicle is controlled to perform a load-pull current operation. If the difference is greater than or equal to the preset threshold, the air compressor assembly 6 is kept running, the first output end 84 and the third output end 82 of the four-way valve 8 are opened, and the second output end 83 is closed, so that the high-temperature air enters the fuel cell stack 1 directly without passing through the intercooler 9 to assist in heating the core, and the step of controlling the load of the vehicle to perform a load-pull current operation is executed.

[0054] Therefore, it can effectively avoid damage to the fuel cell stack caused by directly starting the load due to excessive temperature difference.

[0055] Furthermore, in non-low temperature cold start environments, it is necessary to simplify the gas circuit to avoid energy loss or circuit redundancy caused by unnecessary channel opening.

[0056] Optionally, in some embodiments, after obtaining the coolant outlet temperature of the fuel cell stack 1, the method further includes: closing the first output terminal 84 and the third output terminal 82 of the four-way valve 8 when the coolant outlet temperature is greater than or equal to a preset temperature, and obtaining the vehicle's total power demand; controlling the fuel cell system to start, and outputting power according to the vehicle's total power demand.

[0057] Specifically, if the coolant outlet temperature of the fuel cell stack is greater than the preset temperature, the fuel cell system is not in a low-temperature cold start environment. In this embodiment, the first output terminal 84 and the third output terminal 82 of the four-way valve 8 are closed, and a conventional start-up strategy is executed, that is, the vehicle's total power demand is obtained, the fuel cell system is controlled to start, and power is output according to the vehicle's total power demand.

[0058] This avoids energy loss or circuit redundancy caused by unnecessary channel activation in non-low temperature cold start environments.

[0059] Therefore, by utilizing the characteristic of the downstream gas temperature rise during the operation of the air compressor assembly, and through gas distribution in different branches and corresponding gas-to-gas heat exchanger devices, hydrogen and air synergistic preheating is achieved to assist in the rapid temperature rise of the fuel cell stack core. Based on real-time temperature feedback from multiple locations and stages involving hydrogen, air, and water, the difference is judged to determine whether it meets the target value, thereby adjusting the hydrogen-air preheating jump-in condition in a closed loop, making the overall strategy more stable. The calculation and judgment of water production and ice accumulation in the fuel cell stack are introduced, and the load current during the self-starting phase of the fuel cell stack is dynamically adjusted in real-time according to the internal state of the stack and the chemical reaction situation, which helps to improve the reliability of cold start of the fuel cell system. A complete hydrogen and air synergistic preheating system is established. By precisely controlling the temperature, pressure, and flow rate parameters of the gases on both sides, combined with the short-time closed-loop operation strategy of the fuel cell stack, uniform heating of the stack can be completed in a very short time, avoiding icing, dehydration, and thermal stress damage, thus achieving a safe, rapid, and energy-saving cold start process.

[0060] To facilitate a better understanding of the fuel cell system startup method proposed in the embodiments of this application by those skilled in the art, the following is combined with... Figure 3 Further explanation is needed.

[0061] like Figure 3 As shown, Figure 3 This is a flowchart of a startup method for a fuel cell system according to an embodiment of this application. The startup method for the fuel cell system includes the following steps: S301, the vehicle sends a start-up command for the fuel cell system.

[0062] S302, the fuel cell system performs high-voltage pre-charging and low-voltage configuration, and determines whether the coolant outlet temperature of the fuel cell stack is less than 0°C. If so, proceed to step S306; otherwise, proceed to step S303.

[0063] S303, close the first and third output terminals of the four-way valve.

[0064] S304, the normal temperature start-up control strategy is being executed.

[0065] S305, responding to the target power requirements of the entire vehicle.

[0066] S306 executes a low-temperature mixed heating cold start control strategy.

[0067] S307 is activated to maintain the operation of the water pump and PTC heater. The thermostat operates in a small loop, and the coolant circulates in the system piping to raise the temperature inside the fuel cell stack.

[0068] S308: Open the proportional valve, ejector assembly, and hydrogen circulation pump to establish hydrogen pressure in the fuel cell stack. Simultaneously, run the air compressor, adjust the four-way valve channel to open the second output end, and open the air bypass valve to establish system air flow.

[0069] S309, determine whether the temperature difference between the outlet gas temperature of the air compressor and the outlet hydrogen temperature of the fuel cell stack is greater than or equal to the designed target value. If yes, proceed to step S310; otherwise, proceed to step S313.

[0070] S310: Maintain air compressor operation, close the second output channel of the four-way valve, open the third output channel, and allow high-temperature air to enter the outer tube channel of the shell-and-tube counter-current gas-to-gas heat exchanger to heat the hydrogen in the inner tube. The hydrogen is then circulated into the fuel cell stack through the hydrogen circulation pump to assist in heating the core.

[0071] S311, determine whether the temperature difference between the air compressor outlet gas temperature and the fuel cell stack air outlet temperature is greater than or equal to the designed target value. If yes, proceed to step S312; otherwise, proceed to step S313.

[0072] S312, maintain the operation of the air compressor and the opening of the third output channel of the four-way valve, and at the same time open the first output channel so that the high-temperature air can directly enter the fuel cell stack to assist in heating the core without passing through the intercooler, and execute step S313.

[0073] S313, the load begins to draw in current, causing the fuel cell stack to start working.

[0074] S314, keep the air compressor running, close all other channels of the four-way valve, open the first output channel and close the air bypass valve to allow air to enter the stack, and increase the load to the target current at the maximum allowable load current slope of the stack at low temperature.

[0075] S315 calculates the fuel cell stack water production in real time based on the load current and the real-time calculation formula for fuel cell stack water production.

[0076] S316. Calculate the actual ice amount in the gas diffusion layer based on the calculated water production of the fuel cell stack, the formula for calculating the freezing rate of liquid water below the freezing point, and the formula for calculating the accumulated ice amount in the gas diffusion layer. Determine whether the actual ice amount in the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer. If so, proceed to step S318; otherwise, proceed to step S317.

[0077] S317, combining the difference between the calculated actual ice amount in the gas diffusion layer and the maximum allowable ice capacity of the gas diffusion layer, the stack water production calculation formula, the gas diffusion layer ice capacity calculation formula, and the liquid water freezing rate calculation formula below the freezing point temperature are used to reverse calculate the upper limit of the stack self-starting load current slope and the upper limit of the current corresponding to the reduction of the actual ice amount in the gas diffusion layer, and then return to execute step S315.

[0078] S318, maintain the current self-starting parameters of the fuel cell stack until the temperature of the third temperature acquisition unit 16 reaches the target value that the fuel cell stack 100 can freely pull load, then the cold start is successful and step S305 is executed.

[0079] According to the fuel cell system startup method proposed in this application, after receiving the startup command, the fuel cell system obtains the coolant outlet temperature of the stack. If the temperature is lower than a preset temperature, the stack is heated through the coolant circuit. The hydrogen and oxygen circuits are controlled to be in working state, and the second output terminal of the four-way valve and the air bypass valve are controlled to be in the open state. The startup of the fuel cell system is controlled according to the temperature of the air compressor component output terminal and the hydrogen outlet temperature of the stack. This solves the problems of low heating efficiency, large energy loss, excessive local temperature difference, and lack of coordinated control of hydrogen and air sides in related technologies. By adding a four-way gas solenoid valve and a shell-and-tube counter-current gas-to-gas heat exchanger, the temperature, pressure, and flow rate parameters of the gases on both sides can be precisely controlled. Combined with the short-time closed-loop operation strategy of the stack, the stack can be uniformly heated in a very short time, avoiding freezing, dehydration, and thermal stress damage. This achieves safe, fast, and energy-saving cold start, improves the heating rate, and reduces energy consumption to a certain extent.

[0080] Figure 4 This is a schematic diagram of a vehicle provided in an embodiment of the present invention. The vehicle may include: The memory 401, the processor 402, and the computer program stored on the memory 401 and capable of running on the processor 402.

[0081] When processor 402 executes the program, it implements the fuel cell system startup method provided in the above embodiments.

[0082] Furthermore, the vehicle also includes: Communication interface 403 is used for communication between memory 401 and processor 402.

[0083] The memory 401 is used to store computer programs that can run on the processor 402.

[0084] The memory 401 may include high-speed RAM (Random Access Memory) memory, and may also include non-volatile memory, such as at least one disk storage.

[0085] If the memory 401, processor 402, and communication interface 403 are implemented independently, then the communication interface 403, memory 401, and processor 402 can be interconnected via a bus to complete communication between them. The bus can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus, or an EISA (Extended Industry Standard Architecture) bus, etc. The bus can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 4 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0086] Optionally, in a specific implementation, if the memory 401, processor 402, and communication interface 403 are integrated on a single chip, then the memory 401, processor 402, and communication interface 403 can communicate with each other through an internal interface.

[0087] Processor 402 may be a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement embodiments of the present invention.

[0088] Furthermore, 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 number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0089] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0090] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for starting a fuel cell system, characterized in that, The oxygen circuit of the fuel cell system includes a four-way valve. The input end of the four-way valve is connected to the output end of the air compressor assembly. The first output end of the four-way valve is connected to the oxygen input end. The second output end of the four-way valve is connected to the oxygen input end through an intercooler. The third output end of the four-way valve is connected to a hydrogen preheating assembly. The method includes the following steps: In response to the power-on command, the coolant outlet temperature of the fuel cell stack is obtained; When the coolant outlet temperature is lower than the preset temperature, the fuel cell stack is heated through the coolant circuit of the fuel cell system. The hydrogen circuit and the oxygen circuit of the fuel cell system are controlled to be in the corresponding working state, and the second output terminal and the air bypass valve are both in the open state, while the first output terminal and the third output terminal are in the closed state. One end of the air bypass valve is connected to the output terminal of the intercooler, and the other end of the air bypass valve is connected to the oxygen output terminal of the fuel cell stack. The temperature at the output terminal of the air compressor assembly and the hydrogen outlet temperature of the fuel cell stack are obtained, and the fuel cell system is started according to the temperature at the output terminal of the air compressor assembly and the hydrogen outlet temperature.

2. The method according to claim 1, characterized in that, The step of controlling the start-up of the fuel cell system based on the temperature at the output terminal of the air compressor assembly and the hydrogen outlet temperature includes: Calculate the first difference between the temperature at the output end of the air compressor assembly and the temperature at the hydrogen outlet, and determine whether the first difference is less than a preset threshold. If the first difference is less than the preset threshold, the load of the vehicle is controlled to perform a load current operation, the first output terminal is controlled to be in the open state, and the second output terminal, the third output terminal and the air bypass valve are all controlled to be in the closed state, and the current load current is obtained. The water production of the fuel cell stack is calculated based on the current load current, and the ice capacity of the gas diffusion layer of the fuel cell stack is calculated based on the water production. Based on the ice capacity of the gas diffusion layer, it is determined whether the fuel cell system has completed the cold start. If the fuel cell system completes a cold start, the system obtains the vehicle's total power requirement, controls the fuel cell system to start, and outputs power according to the vehicle's total power requirement.

3. The method according to claim 2, characterized in that, The water production capacity of the fuel cell stack is: ； in, The water production rate of the fuel cell stack; The number of individual pieces in the fuel cell stack; n The number of electrons transferred in the electrochemical reaction of the stack; F It is Faraday's constant; It is a function of the change of current with time from 0 to t (s); Let be the molar mass of water.

4. The method according to claim 2, characterized in that, The ice capacity of the gas diffusion layer is: ； in, The ice capacity of the gas diffusion layer. This represents the volume fraction of water converted into ice. This is the instantaneous operating current of the fuel cell.

5. The method according to claim 2, characterized in that, The step of determining whether the fuel cell system has completed a cold start based on the ice capacity of the gas diffusion layer includes: Determine whether the ice capacity of the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer; If the ice capacity of the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer, the fuel cell system is determined to have completed a cold start when the coolant outlet temperature of the fuel cell stack reaches the target temperature.

6. The method according to claim 5, characterized in that, After determining whether the ice capacity of the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer, the method further includes: If the ice capacity of the gas diffusion layer is greater than or equal to the maximum allowable ice capacity of the gas diffusion layer, then calculate the second difference between the ice capacity of the gas diffusion layer and the maximum allowable ice capacity of the gas diffusion layer, and calculate the upper limit of the slope and the upper limit of the load current based on the second difference. Based on the upper limit of the slope of the load current and the upper limit of the current, the load current of the fuel cell is adjusted, and the adjusted load current is used as the current load current. The step of recalculating the water production of the fuel cell based on the current load current is repeated until the new ice capacity of the gas diffusion layer is less than the maximum allowable ice capacity of the gas diffusion layer.

7. The method according to claim 5, characterized in that, After determining whether the first difference is less than a preset threshold, the method further includes: If the difference is greater than or equal to a preset threshold, the third output terminal is controlled to be in the open state, and the second output terminal and the first output terminal are controlled to be in the closed state, so as to heat the hydrogen in the hydrogen supply circuit of the hydrogen preheating component. Obtain the temperature at the output terminal of the new air compressor assembly and the oxygen output terminal temperature of the fuel cell stack; If the temperature difference between the output terminal of the new air compressor component and the output terminal of the oxygen component is greater than or equal to the preset threshold, then the first output terminal and the third output terminal are controlled to be in the open state, and the second output terminal is controlled to be in the closed state, and the step of controlling the load of the vehicle to perform the load current operation is executed.

8. The method according to claim 1, characterized in that, Heating the fuel cell stack via the coolant circuit of the fuel cell system includes: The thermostat of the fuel cell system is adjusted to a first state to form the coolant circuit through the stack coolant output terminal, thermostat, heater, water pump, and stack coolant input terminal; The water pump and heater of the fuel cell system are both in operation to heat the coolant in the coolant circuit, and the heated coolant heats the fuel cell stack.

9. The method according to claim 1, characterized in that, After obtaining the coolant outlet temperature of the fuel cell stack, the following steps are also included: When the coolant outlet temperature is greater than or equal to the preset temperature, the first and third output terminals of the four-way valve are closed, and the vehicle's total power demand is obtained. The system controls the start-up of the fuel cell system and outputs power according to the power requirements of the vehicle.

10. A vehicle, characterized in that, include: A memory, a processor, and a computer program stored in the memory and capable of running on the processor, the processor executing the program to implement the start-up method of the fuel cell system as described in any one of claims 1-9.

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