A cooling system and control method for multi-stack fuel cells

Abstract

This invention proposes a multi-stack fuel cell cooling system and control method. The cooling system includes an intercooler, a cooling water tank, a water pump, and a PTC heater. The water pump inlet is connected to the cooling water tank, and the water pump outlet is connected to the PTC heater. The outlet of the PTC heater is connected to three cooling branches, which are connected to the intercooler via a return pipe. The outlet of the intercooler is connected to the cooling water tank. Each cooling branch includes a switching valve, a check valve, a fuel cell stack, a thermostat, and a three-way solenoid valve. The branches are connected by pipelines to form a preheating circulation loop. The heat generated after one stack operates can be used to preheat a second stack or the remaining stacks, improving the system's energy utilization rate. The multi-stack fuel cell cooling system control method can achieve the alternating use of multiple fuel cell stacks, maintaining the consistency of the lifespan of each stack in the multi-stack fuel cell power system, thereby improving the system's service life.

Description

Technical Field

[0001] This invention belongs to the field of fuel cells, and particularly relates to a cooling system and control method for multi-stack fuel cells. Background Technology

[0002] With the further development of the automotive industry, traditional internal combustion engine vehicles consume large amounts of fossil fuels, emitting harmful exhaust gases, leading to air pollution, the greenhouse effect, and acid rain. The energy crisis and climate change have become urgent global issues that need to be addressed. Using hydrogen fuel cells as an energy storage solution for electric vehicles is another way to reduce charging time and increase vehicle range. Furthermore, hydrogen is considered a clean fuel with relatively wide sources, such as water electrolysis, biomass hydrogen production, and industrial by-product hydrogen. However, low durability and high cost are two major reasons hindering the commercialization of fuel cells.

[0003] A single high-power fuel cell stack has a short lifespan. Replacing a single stack with multiple low-power stacks, combined with energy management algorithms, can effectively extend the lifespan of a fuel cell system. Multi-stack fuel cell systems typically employ independent cooling circuits, meaning each stack's cooling circuit includes an independent water pump, PTC heater, radiator, and other components. While this effectively maintains the stack's operating temperature, it results in high system cost, high energy consumption, and a significant space requirement for the cooling system. Furthermore, fuel cells require a considerable amount of time for cold starts in cold environments; without preheating, a cold start can take 2-5 minutes. This means that multi-stack fuel cell systems cannot quickly meet the energy demands of real-time vehicle operation. Current technologies often use PTC heaters to preheat the stacks and insulate temporarily inactive stacks, consuming a large amount of electrical energy, while the waste heat from the stacks is not effectively utilized. Summary of the Invention

[0004] This invention addresses the technical problems of existing multi-stack fuel cells employing independent cooling circuits, resulting in high system costs and ineffective utilization of stack waste heat. It proposes a multi-stack fuel cell cooling system and control method that effectively utilizes stack waste heat for stack preheating and insulation.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A multi-stack fuel cell cooling system includes an intercooler, a cooling water tank, a water pump, and a PTC heater. The water pump inlet is connected to the cooling water tank, the water pump outlet is connected to the PTC heater, the PTC heater outlet is connected to three cooling branches, the three cooling branches are connected to the intercooler via a return water pipe, and the intercooler outlet is connected to the cooling water tank.

[0007] The first cooling branch includes a switch valve 1, a check valve 7, a fuel cell stack 1, a thermostat 1, a three-way solenoid valve 1, and a check valve 2 connected in sequence via pipelines. The second cooling branch includes a switch valve 2, a check valve 8, a fuel cell stack 2, a thermostat 2, a three-way solenoid valve 2, and a check valve 2. The third cooling branch includes a switch valve 3, a check valve 9, a fuel cell stack 3, a thermostat 3, a three-way solenoid valve 3, and a check valve 3. The third ports of thermostats 1 to 3 are all connected to return water pipe 2, which is connected to a water pump. A check valve 11 is also connected between the third port of three-way solenoid valve 1 and fuel cell stack 2. A check valve 12 is also connected between the third port of three-way solenoid valve 2 and fuel cell stack 3. A check valve 10 is also connected between the third port of three-way solenoid valve 3 and fuel cell stack 1.

[0008] Preferably, temperature sensors are connected to each of the first to third fuel cells.

[0009] Preferably, the third ports of thermostats one to three are all connected to return water pipe two via a one-way valve.

[0010] This invention also proposes a control method for a multi-stack fuel cell cooling system, including a preheating cold start phase and a multi-stack normal operation phase. During cold start, the preheating cold start phase operates, with the FCU controlling the opening of valves one through three, closing the circuit to return water pipe one while simultaneously opening the circuit to the other stacks, starting the water pump and PTC heater, and preheating the three stacks with cooling water. When the temperatures of stacks one through three all reach the preheating temperature T... min The system then enters the normal operation phase for multiple reactors.

[0011] The PTC heater is turned off, and the FCU calculates the number and sequence number of the fuel cell stacks that need to operate.

[0012] When only one fuel cell stack needs to operate, the switching valve of the cooling branch containing that stack opens, while the other two switching valves close. The FCU adjusts the opening of the two three-way solenoid valves at the front end of the two non-operating fuel cell stacks in real time, and closes the third interface of the other three-way solenoid valves, so that the temperature of the two non-operating fuel cell stacks is maintained at the preheating temperature T. min and optimal operating temperature T best between;

[0013] When two fuel cells are required to operate, the switching valves of the cooling branches containing the two operating fuel cells open. The FCU adjusts the valve opening of the three-way solenoid valve at the front end of the non-operating fuel cell in real time, while the other three-way solenoid valves close their third ports, keeping the temperature of the fuel cell at T. min ~T best between;

[0014] When all three fuel cells need to operate, the three switching valves open and the three three-way solenoid valves close the third port.

[0015] As a preferred method, the FCU calculates the number and sequence number of the required battery stacks by obtaining the state of charge (SOC) and power demand (P) of the power battery. req Based on the state of charge (SOC) of the power battery and the required power P req Determine the power allocation method for 1 to n fuel cells, where n is 3;

[0016] When SOC > A%, the power demand is met solely by the battery.

[0017] When battery A% ≥ SOC > B%, if P req The maximum output power value less than that of a single fuel cell stack, i.e., P stack_max >P req The power demand is met solely by the battery; if n*P stack_max ≥P req >(n-1)*P stack_max If n-1 stacks are activated, all n-1 stacks will output maximum power, and the remaining power demand will be met by the battery.

[0018] When battery B% ≥ SOC, if P stack_max >P req If n*P, then one fuel cell stack is activated, which outputs maximum power, and excess energy is used to charge the battery until SOC > A%, at which point the fuel cell stack is shut down; stack_max ≥P req >(n-1)*P stack_max If n stacks are activated, all n stacks will output maximum power, and excess energy will be used to charge the battery until the battery SOC > A%, at which point the stacks will be shut down.

[0019] The startup sequence of the above-mentioned fuel cell stacks is determined by the following method:

[0020] The voltage value V at the rated power specified at the time of manufacture for each fuel cell stack was obtained based on bench tests. e During system operation, the actual output voltage V' of the fuel cell stack under rated operating conditions is measured. e The percentage of voltage decay of the fuel cell stack is D = (V e -V' e ) / V e Compare and sort the D values ​​of each fuel cell stack, prioritizing the stacks with the smallest degradation percentage.

[0021] If the D values ​​are the same, then the fuel cell stack with the shorter operating time T is further preferred.

[0022] As preferred options, A is 80 and B is 20.

[0023] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0024] 1. This multi-stack fuel cell cooling system requires only one water pump, one PTC heater, and one intercooler. The system has a simple structure and low cost.

[0025] 2. In addition to the cooling branch for each fuel cell stack, a circulating insulation loop is also provided, which runs from fuel cell stack one, fuel cell stack two, fuel cell stack three, and back to fuel cell stack one. Therefore, the heat generated when one stack is working can be used to insulate the second stack or the remaining stacks, reducing the extra heat required for preheating the second stack or the remaining stacks and improving the energy utilization rate of the system.

[0026] 3. Once the front-end fuel cell stack is working normally, the back-end fuel cell stack can start up quickly without consuming additional power, and its normal heat dissipation function will not be affected when the back-end fuel cell stack is working normally.

[0027] 4. The multi-stack fuel cell cooling system control method can realize the alternating use of multiple stacks, maintain the consistency of the lifespan of each stack in the multi-stack fuel cell power system, and thus improve the service life of the system.

[0028] 5. Precise control of the preheating and operating temperatures of multi-stack fuel cells has been achieved, avoiding heat accumulation, ensuring system stability, and making the system highly efficient and practical. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the multi-stack fuel cell cooling system of the present invention;

[0030] Figure 2 This is a control network connection diagram of the multi-stack fuel cell cooling system of the present invention;

[0031] Figure 3 This is a schematic diagram of the power system involved in the multi-stacking fuel cell cooling system of the present invention;

[0032] In the above diagrams: 1. Cooling water tank; 2. Water pump; 3. PTC heater; 4. Switch valve one; 5. Check valve seven; 6. Fuel cell stack one; 7. Thermostat one; 8. Three-way solenoid valve one; 9. Check valve two; 10. Check valve one; 11. Switch valve two; 12. Check valve eight; 13. Fuel cell stack two; 14. Thermostat two; 15. Three-way solenoid valve two; 16. Check valve four; 17. Check valve three; 18. Switch valve three; 19. 20. Check Valve 9; 21. Fuel Cell Stack 3; 22. Thermostat 3; 23. Three-Way Solenoid Valve 3; 24. Check Valve 6; 25. Check Valve 5; 26. Intercooler 2; 27. Return Water Pipe 1; 28. Return Water Pipe 2; 29. ​​Temperature Sensor 1; 30. Temperature Sensor 2; 31. Check Valve 10; 32. Check Valve 11; 33. Check Valve 12; a. First Interface; b. Second Interface; c. Third Interface. Detailed Implementation

[0033] To better understand the present invention, the following detailed description is provided in conjunction with the accompanying drawings and embodiments.

[0034] Example 1

[0035] like Figure 1 As shown, a multi-stack fuel cell cooling system includes an intercooler 25, a cooling water tank 1, a water pump 2, and a PTC heater 3. The inlet of the water pump 2 is connected to the cooling water tank 1, and the outlet of the water pump 2 is connected to the PTC heater 3. The outlet of the PTC heater 3 is connected to three cooling branches, and the three cooling branches are connected to the intercooler 25 via a return water pipe 26. The outlet of the intercooler 25 is connected to the cooling water tank 1.

[0036] The first cooling branch includes a series of interconnected pipes: a 1-way switch valve 4, a 7-way check valve 5, a 1-way fuel cell stack 6, a 1-way thermostat 7, a 1-way solenoid valve 8, and a 2-way check valve 9. The third port of the 1-way thermostat 7 is connected to the return water pipe 27 via a 1-way check valve 10, and the return water pipe 27 is connected to the water pump 1. The second cooling branch includes a 2-way switch valve 11, a 8-way check valve 12, a 2-way fuel cell stack 13, a 2-way thermostat 14, a 2-way solenoid valve 25, and a 2-way check valve 9. The third port of the 2-way thermostat 14 is connected to the return water pipe 27 via a 3-way check valve 17. The third cooling branch includes a 3-way switch valve 18, a 9-way check valve 19, a 3-way fuel cell stack 20, a 3-way thermostat 21, a 3-way solenoid valve 22, and a 3-way check valve 17. The third port of the 3-way thermostat 21 is connected to the return water pipe 27 via a 5-way check valve 24.

[0037] A one-way valve 11 32 is connected between the third port c of the three-way solenoid valve 18 and the fuel cell stack 2 13; a one-way valve 12 33 is connected between the third port c of the three-way solenoid valve 2 15 and the fuel cell stack 3 20; and a one-way valve 10 31 is connected between the third port c of the three-way solenoid valve 3 22 and the fuel cell stack 1 6, forming a preheating loop that runs from fuel cell stack 1 6, fuel cell stack 2 13, fuel cell stack 3 20, and back to fuel cell stack 1 6. Temperature sensors 1 to 3 are connected to fuel cell stacks 1 to 3 respectively to measure the temperature of the cooling water at the fuel cell stack outlet.

[0038] It also includes the fuel cell controller (FCU). The FCU communicates and is controlled via a CAN network with water pump 2, on / off valves 1-3, PTC heater 3, temperature sensors 1-3, three-way solenoid valves 1-3, and fuel cell stack 1-3. The CAN network is as follows: Figure 2 As shown.

[0039] The operation process of the multi-stack fuel cell cooling system is as described in Example 2.

[0040] This multi-stall fuel cell cooling system requires only one water pump, one PTC heater, and one intercooler, resulting in a simple structure and low cost. In addition to the cooling branch for each fuel cell stack, a circulating insulation loop is also included, connecting stack one, stack two, stack three, and back to stack one. Therefore, the heat generated by one stack can be used to insulate the second or remaining stacks, reducing the additional heat required for preheating and improving the system's energy efficiency. Once the front-end stacks are operating normally, the back-end stacks can be started up quickly without consuming additional electrical energy, and their normal heat dissipation function is not affected during operation.

[0041] Example 2

[0042] A control method for a multi-stack fuel cell cooling system includes a preheating cold start phase, a multi-stack normal operation phase, and a shutdown phase.

[0043] Preheating Cold Start Phase: When the vehicle starts cold, the fuel cell stack temperature is too low to operate normally. At this time, low-voltage electricity is applied to the vehicle, and fuel cell stacks one through three begin preheating. The FCU controls the opening of valves one through three. The FCU controls three-way solenoid valve 1 (8) to close the circuit to check valve 2 (9) and simultaneously open the circuit to check valve 11 (32). Three-way solenoid valve 2 (15) closes the circuit to check valve 4 (16) and simultaneously opens the circuit to check valve 12 (33). Three-way solenoid valve 3 (22) closes the circuit to check valve 6 (23) and simultaneously opens the circuit to check valve 10 (31). Afterward, the FCU controls water pump 2 to start and PTC heater 3 to start. Coolant, after being heated by the PTC, returns to water pump 2 through the small circulation loops of thermostats one through three in the cooling branches where each fuel cell stack is located. As preheating progresses, the coolant temperature gradually reaches the temperature value T at which the thermostat's large circulation loop opens. min T min This is also the preheating target temperature for fuel cell stacks one through three. If the thermostat 7's main circulation is opened first, part of the cooling water returns to water pump 2 through check valve 10, and most of the cooling water enters fuel cell stack 2 13 through three-way solenoid valve 8. Fuel cell stack 2 13 receives the heated cooling water flowing in from check valve 8 12 and check valve 11 32, which can accelerate the process of fuel cell stack 2 13 reaching the preheating temperature T. min If the thermostat 321 opens first for the main circulation, a portion of the cooling water returns to the water pump 2 through the one-way valve 524, while most of the cooling water enters the fuel cell stack 6 through the three-way solenoid valve 322. The fuel cell stack 6 receives the heated cooling water flowing in from the one-way valves 75 and 1031, which can accelerate the process of the fuel cell stack 6 reaching the preheating temperature T. min .

[0044] Normal operation of multiple stacks: After the preheating and cold start of stacks one to three is completed, PTC heater 3 is turned off, and the working status of three-way solenoid valves one to three is determined according to the stack number that needs to work calculated by the energy management algorithm.

[0045] Common multi-stack fuel cell power system structures include Figure 3 As shown, it mainly includes fuel cell stacks one to three, a battery, DC / DC converters one to three, voltage sensors one to three, a motor controller, and a motor. The battery and fuel cell stacks one to three are connected in parallel to the bus to supply power to the motor controller. The motor controller controls the motor speed and torque according to the vehicle's driving requirements. Voltage sensors one to three measure the voltage of fuel cell stacks one to three respectively.

[0046] The energy management algorithm is as follows:

[0047] First, obtain the state of charge (SOC) and power demand (P) of the power battery. req The number of fuel cell stacks required is calculated based on the power demand. When selecting fuel cell stacks one through three, the maximum system power demand P is satisfied. req_max The maximum output power P of less than three fuel cells stack_max The sum, i.e., 3*P stack_max >P req_max .

[0048] When the battery SOC > 80%, the battery alone meets the system power demand, and the battery output power P bat =P req .

[0049] When the battery is 80% ≥ SOC > 20%, according to the required power P req Calculate the power distribution pattern of batteries and stacks one through three, if P req The maximum output power value less than that of a single fuel cell stack, i.e., P stack_max >P req At this time, only the battery works, and the power demand is met solely by the battery; if P req The maximum output power of one fuel cell stack is greater than or equal to the sum of the maximum output power values ​​of two fuel cell stacks, i.e., 2*P. stack_max ≥P req >P stack_max If P..., then one fuel cell stack will be activated, outputting maximum power, with the remaining power demand met by the battery; if P... req The maximum output power is greater than that of two fuel cells but less than the sum of the maximum output power of three fuel cells, i.e., 3*P. stack_max ≥P req >2*P stack_max If the battery is activated, both fuel cells will start, and both will output maximum power. The remaining power demand will be met by the battery.

[0050] When the battery is at 20% or higher SOC, the required power P is determined according to... req Calculate the power distribution pattern of batteries and stacks one through three. If P req The maximum output power value less than that of a single fuel cell stack, i.e., P stack_max >Preq If P..., then one fuel cell stack is activated. A portion of the stack's maximum output power meets the system's power requirements, and excess energy charges the battery until the battery's SOC > 80%, after which the stack is shut down; if P... req The maximum output power of one fuel cell stack is greater than or equal to the sum of the maximum output power values ​​of two fuel cell stacks, i.e., 2*P. stack_max ≥P req >P stack_max If P..., then both fuel cells will start, and both will output maximum power. A portion of the power output from the two fuel cells will meet the system's power requirements, while excess energy will charge the battery until the battery's SOC > 80%, after which the fuel cells will be shut down; if P... req The maximum output power is greater than that of two fuel cells but less than the sum of the maximum output power of three fuel cells, i.e., 3*P. stack_max ≥P req >2*P stack_max If the system is activated, all three fuel cells will start and output maximum power. Part of the power output from the three fuel cells will meet the system power requirements, and the excess energy will charge the battery until the battery SOC is greater than 80%. After that, the fuel cells will be shut down.

[0051] The startup sequence of the three fuel cell stacks was determined by the following method:

[0052] The voltage values ​​V of fuel cells one through three at the factory rated power were obtained from bench tests. e1 V e2 V e3 During system operation, the actual output voltage values ​​V' of fuel cell stacks one to three under rated operating conditions were measured. e1 ,V' e2 ,V' e3 The percentage of voltage decay from one to three of the fuel cell stack is D1 = (V e1 -V' e1 ) / V e1 D2 = (V e2 -V' e2 ) / V e2 D3 = (V e3 -V' e3 ) / V e3 Compare and sort the values ​​of D1, D2, and D3, prioritizing the stack with the smallest percentage of degradation. For example, if D3 > D1 > D2, then if two stacks need to operate, start stack 1 (6) and stack 2 (13); if only one stack needs to operate, start stack 2 (13).

[0053] If D1 = D2 = D3, the reactor stack is activated based on its historical operating time. The historical operating times of the reactor stacks are saved as T1, T2, and T3. Reactors with shorter operating times are activated first, for example, T3 > T1 > T2. If two reactor stacks need to operate, reactor stack 1 (6) and reactor stack 2 are activated; if only one reactor stack needs to operate, reactor stack 2 (13) is activated. If another reactor stack has the same D and T values, one of the two reactor stacks is randomly selected to operate.

[0054] The following explanation is based on the specific number and sequence number of the operating fuel cell stacks:

[0055] (1) If only fuel cell stack 16 needs to operate, while fuel cell stack 23 and fuel cell stack 320 do not need to operate, then it is necessary to keep the temperature of fuel cell stack 23 and fuel cell stack 320 at the preheating temperature T. min and optimal operating temperature T best This is to ensure that it can start working quickly when needed. Switch valve 14 remains open, switch valves 2 and 3 are closed, and three-way solenoid valve 32 closes the circuit to check valve 1031 and opens the circuit to check valve 623.

[0056] Cooling water flows into fuel cell stack 6 through check valve 75 and absorbs heat from fuel cell stack 6 before flowing into thermostat 7. A small portion of the cooling water flowing out of thermostat 7 flows into water pump 2 through check valve 10 in the small circulation, while most of the cooling water enters three-way solenoid valve 8. At this time, three-way solenoid valve 8 distributes the flow of cooling water into check valve 29 and check valve 1132 according to the water and heat management algorithm.

[0057] Cooling water flows into the three-way solenoid valve 18, then through check valve 29 and intercooler 25 into the water tank, and through check valve 1132 into fuel cell stack 2. After insulating fuel cell stack 23, the cooling water flows from the outlet into thermostat 24. A small portion of the cooling water flowing out of thermostat 24 flows into water pump 2 through check valve 317 in the small circulation loop, while most of the cooling water enters the three-way solenoid valve 25. At this time, the three-way solenoid valve 25 distributes the flow of cooling water into check valve 416 and check valve 1233 according to the water-thermal management algorithm.

[0058] Cooling water flows into the three-way solenoid valve 215, then through one-way valve 416 and intercooler 25 into the water tank, and through one-way valve 1233 into fuel cell stack 320. After insulating the fuel cell stack 320, the cooling water flows from the outlet into thermostat 321. A small portion of the cooling water flowing out of thermostat 321 flows into water pump 2 through one-way valve 524 in the small circulation loop, while most of the cooling water enters the three-way solenoid valve 322. The cooling water then flows through the three-way solenoid valve 322, through one-way valve 623 and intercooler 25 into the water tank.

[0059] The FCU controls the opening of the three-way solenoid valve 8 through a hydrothermal management algorithm, thereby controlling the flow rate into the fuel cell stack 13 and ensuring that the temperature of the fuel cell stack 13 is greater than T. min And less than the optimal operating temperature T of the fuel cell best The hydrothermal management algorithm controls the flow rate into fuel cell stack 20 via a three-way solenoid valve 215, thereby ensuring that the temperature of fuel cell stack 20 is greater than T. min And less than the optimal operating temperature T of the fuel cell best .

[0060] (2) If only fuel cell stack 2 (13) needs to operate, while fuel cell stack 1 (6) and fuel cell stack 3 (20) do not need to operate, then it is necessary to maintain the temperature of fuel cell stack 1 (6) and fuel cell stack 3 at the preheating temperature T. min and optimal operating temperature T best This arrangement ensures that the valve can be quickly put into operation when needed. Switch valve 2 11 remains open, switch valve 1 4 and switch valve 3 are closed, and three-way solenoid valve 1 8 closes the circuit to check valve 11 32 and opens the circuit to check valve 2 9.

[0061] Cooling water flows into fuel cell stack 2 13 through check valve 8 12 and absorbs heat from fuel cell stack 2 13 before flowing into thermostat 2 14. A small portion of the cooling water flowing out of thermostat 2 14 flows into water pump 2 through check valve 3 17 in the small circulation, while most of the cooling water enters three-way solenoid valve 2 15. At this time, three-way solenoid valve 2 15 distributes the flow of cooling water into check valve 4 16 and check valve 12 33 according to the water and heat management algorithm.

[0062] Cooling water flows into the three-way solenoid valve 215, then through one-way valve 416 and intercooler 25 into the water tank, and through one-way valve 1233 into fuel cell stack 320. After insulating the fuel cell stack 320, the cooling water flows from the outlet into thermostat 321. A small portion of the cooling water flowing out of thermostat 321 flows into water pump 2 through one-way valve 416 in the small circulation loop, while most of the cooling water enters the three-way solenoid valve 322. At this time, the three-way solenoid valve 322 distributes the flow of cooling water into one-way valve 623 and one-way valve 1031 according to the water and heat management algorithm.

[0063] Cooling water flows into the three-way solenoid valve 22, then through one-way valve 23 and intercooler 25 into the water tank, and through one-way valve 31 into fuel cell stack 6. After insulating fuel cell stack 6, the cooling water flows from the outlet into thermostat 7. A small portion of the cooling water flowing out of thermostat 7 flows into water pump 2 through one-way valve 10 in the small circulation loop, while most of the cooling water enters the three-way solenoid valve 8. The cooling water then flows through the three-way solenoid valve 8, through one-way valve 9, and intercooler 25 into the water tank.

[0064] The FCU controls the opening of the three-way solenoid valve 15 through a hydrothermal management algorithm, thereby controlling the flow rate into the fuel cell stack 20 and ensuring that the temperature of the fuel cell stack 20 is greater than T. min And less than the optimal operating temperature T of the fuel cell best The hydrothermal management algorithm controls the flow rate into fuel cell stack 6 via a three-way solenoid valve 322, thereby ensuring that the temperature of fuel cell stack 320 is greater than T. min And less than the optimal operating temperature T of the fuel cell best .

[0065] (3) If only fuel cell stack 3 20 needs to work, and fuel cell stack 1 6 and fuel cell stack 2 13 do not need to work, then it is necessary to keep the temperature of fuel cell stack 1 6 and fuel cell stack 2 at the preheating temperature T. min and optimal operating temperature T best The circuit is positioned such that it can be started quickly when needed. Switch valve 3 18 remains open, switch valve 1 4 and switch valve 2 are closed, and three-way solenoid valve 3 22 closes the circuit to check valve 12 33 and opens the circuit to check valve 4 16.

[0066] Cooling water flows into fuel cell stack 20 through check valve 19 and absorbs heat from fuel cell stack 20 before flowing into thermostat 21. A small portion of the cooling water flowing out of thermostat 21 flows into water pump 2 through check valve 24 in the small circulation, while most of the cooling water enters three-way solenoid valve 22. At this time, three-way solenoid valve 22 distributes the flow of cooling water into check valve 23 and check valve 31 according to the water and heat management algorithm.

[0067] Cooling water flows into the three-way solenoid valve 22, then flows through check valve 23 and intercooler 25 into the water tank, and through check valve 31 into fuel cell stack 6. After insulating fuel cell stack 6, the cooling water flows from the outlet into thermostat 7. A small portion of the cooling water flowing out of thermostat 7 flows into water pump 2 through check valve 10 in the small circulation loop, while most of the cooling water enters the three-way solenoid valve 8. At this point, the three-way solenoid valve 8 distributes the flow of cooling water into check valves 9 and 32 according to the hydrothermal management algorithm.

[0068] Cooling water flows into the three-way solenoid valve 18, then through one-way valve 29 and intercooler 25 into the water tank, and through one-way valve 1132 into fuel cell stack 23. After insulating fuel cell stack 23, the cooling water flows from the outlet into thermostat 24. A small portion of the cooling water flowing out of thermostat 24 flows into water pump 2 through one-way valve 37 in the small circulation loop, while most of the cooling water enters the three-way solenoid valve 25. The cooling water then flows through the three-way solenoid valve 25, through one-way valve 416, and intercooler 25 into the water tank.

[0069] The FCU controls the opening degree of the three-way solenoid valve 8 through a hydrothermal management algorithm, thereby ensuring that the temperature of the fuel cell stack 13 is greater than T. minAnd less than the optimal operating temperature T of the fuel cell best The FCU controls the opening degree of the three-way solenoid valve 322 through a hydrothermal management algorithm, thereby ensuring that the temperature of the fuel cell stack 320 is greater than T. min And less than the optimal operating temperature T of the fuel cell best .

[0070] (4) If fuel cell stack 1 and fuel cell stack 2 need to operate, but fuel cell stack 3 does not need to operate, then the temperature of fuel cell stack 3 needs to be maintained at the preheating temperature T. min and optimal operating temperature T best The valves are positioned such that they can be quickly put into operation when needed. Switch valve 1 (4) and switch valve 2 remain open, while switch valve 3 (18) is closed. Three-way solenoid valve 1 (8) closes the circuit to check valve 11 (32) and opens the circuit to check valve 2 (9); three-way solenoid valve 3 (22) closes the circuit to check valve 10 (31) and opens the circuit to check valve 6 (23).

[0071] Cooling water flows into fuel cell stack 6 through check valve 75 and absorbs the heat of fuel cell stack 6 before flowing into thermostat 7. A small portion of the cooling water flowing out of thermostat 7 flows into water pump 2 through check valve 10 in the small circulation, while most of the cooling water enters three-way solenoid valve 8 and returns to the water tank through check valve 29 and intercooler 25.

[0072] Cooling water flows into fuel cell stack 2 13 through check valve 8 12 and absorbs heat from fuel cell stack 2 13 before flowing into thermostat 2 14. A small portion of the cooling water flowing out of thermostat 2 14 flows into water pump 2 through check valve 3 17 in the small circulation, while most of the cooling water enters three-way solenoid valve 2 15. At this time, three-way solenoid valve 2 15 distributes the flow of cooling water into check valve 4 16 and check valve 12 33 according to the water and heat management algorithm.

[0073] Cooling water flows into the three-way solenoid valve 215, then through one-way valve 416 and intercooler 25 into the water tank, and through one-way valve 1233 into fuel cell stack 320. After the cooling water flows into fuel cell stack 320 to insulate it, it flows from the outlet into thermostat 321. A small portion of the cooling water flowing out of thermostat 321 flows into water pump 2 through one-way valve 524 in the small circulation, while most of the cooling water enters the three-way solenoid valve 322 and flows into the water tank through one-way valve 623 and intercooler 25.

[0074] (5) If fuel cell stack 16 and fuel cell stack 3 need to operate, but fuel cell stack 213 does not need to operate, then the temperature of fuel cell stack 213 needs to be kept at the preheating temperature T. min and optimal operating temperature T bestThe valves are positioned such that they can be started quickly when needed. Switch valve 1 (4) and switch valve 3 remain open, while switch valve 2 (11) is closed. Three-way solenoid valve 2 (15) closes the circuit to check valve 12 (33) and opens the circuit to check valve 4 (16); three-way solenoid valve 3 (22) closes the circuit to check valve 10 (31) and opens the circuit to check valve 6 (23).

[0075] Cooling water flows into fuel cell stack 20 through check valve 9 19 and absorbs heat from fuel cell stack 20 before flowing into thermostat 21. A small portion of the cooling water flowing out of thermostat 21 flows into water pump 2 through check valve 5 24 in the small circulation, while most of the cooling water enters three-way solenoid valve 22 and returns to the water tank through check valve 6 23 and intercooler 25.

[0076] Cooling water flows into fuel cell stack 6 through check valve 75 and absorbs heat from fuel cell stack 6 before flowing into thermostat 7. A small portion of the cooling water flowing out of thermostat 7 flows into water pump 2 through check valve 10 in the small circulation, while most of the cooling water enters three-way solenoid valve 8. At this time, three-way solenoid valve 8 distributes the flow of cooling water into check valve 29 and check valve 1132 according to the water and heat management algorithm.

[0077] Cooling water flows into the three-way solenoid valve 8, then through one-way valve 9 and intercooler 25 into the water tank, and through one-way valve 11 32 into fuel cell stack 13. After the cooling water flows into fuel cell stack 13 to insulate it, it flows from the outlet into thermostat 14. A small portion of the cooling water flowing out of thermostat 14 flows into water pump 2 through one-way valve 3 17 in the small circulation, while most of the cooling water enters the three-way solenoid valve 15 and flows into the water tank through one-way valve 4 16 and intercooler 25.

[0078] (6) If fuel cell stack 2 and fuel cell stack 3 need to operate, while fuel cell stack 16 does not need to operate, then the temperature of fuel cell stack 2 13 needs to be maintained at the preheating temperature T. min and optimal operating temperature T best The valves are positioned such that they can be quickly put into operation when needed. Switch valve 1 (4) and switch valve 3 remain open, while switch valve 2 (11) is closed. Three-way solenoid valve 1 (8) closes the circuit to check valve 11 (32) and opens the circuit to check valve 2 (9); three-way solenoid valve 2 (15) closes the circuit to check valve 12 (33) and opens the circuit to check valve 4 (16).

[0079] Cooling water flows into fuel cell stack 2 13 through check valve 8 12 and absorbs the heat of fuel cell stack 2 13 before flowing into thermostat 2 14. A small portion of the cooling water flowing out of thermostat 2 14 flows into water pump 2 through check valve 3 17 in the small circulation, while most of the cooling water enters three-way solenoid valve 2 15 and returns to the water tank through check valve 4 16 and intercooler 25.

[0080] Cooling water flows into fuel cell stack 20 through check valve 19 and absorbs heat from fuel cell stack 20 before flowing into thermostat 21. A small portion of the cooling water flowing out of thermostat 21 flows into water pump 2 through check valve 24 in the small circulation, while most of the cooling water enters three-way solenoid valve 22. At this time, three-way solenoid valve 22 distributes the flow of cooling water into check valve 23 and check valve 31 according to the water and heat management algorithm.

[0081] Cooling water flows into the three-way solenoid valve 22, then through one-way valve 23 and intercooler 25 into the water tank, and through one-way valve 31 into fuel cell stack 6. After the cooling water flows into fuel cell stack 6 to insulate it, it flows from the outlet into thermostat 7. A small portion of the cooling water flowing out of thermostat 7 flows into water pump 2 through one-way valve 10 in the small circulation, while most of the cooling water enters the three-way solenoid valve 8 and flows into the water tank through one-way valve 9 and intercooler 25.

[0082] (7) If all three fuel cells need to work, there is no need to consider the preheating and insulation of fuel cells one to three. Only the heat dissipation of the three fuel cells needs to be considered. Switch valves one to three are all open. Three-way solenoid valve one 8 closes the circuit to check valve eleven 32 and opens the circuit to check valve two 9. Three-way solenoid valve two 15 closes the circuit to check valve twelve 33 and opens the circuit to check valve four 16. Three-way solenoid valve three 22 closes the circuit to check valve ten 31 and opens the circuit to check valve six 23.

[0083] Shutdown procedure: Water pump 2 is turned off, and valves one through three are all closed, thus shutting down the system.

[0084] The hydrothermal management algorithm for controlling the valve openings of the three-way solenoid valves (positions one, two, and three) is as follows:

[0085] When only one of the three fuel cell stacks is not operating, the FCU, based on the hydrothermal management algorithm, only needs to adjust the valve opening of the three-way solenoid valve at the front end of the non-operating stack in real time, and maintain the temperature of that stack between Tmin and Tbest. The three-way solenoid valve at the front end of fuel cell stack 16 is three-way solenoid valve 322, the three-way solenoid valve at the front end of fuel cell stack 213 is three-way solenoid valve 18, and the three-way solenoid valve at the front end of fuel cell stack 20 is three-way solenoid valve 215.

[0086] For example, when fuel cell stack 6 is not working, it is necessary to adjust the real-time opening degree D3 of the three-way solenoid valve 22, and the temperature T1 of fuel cell stack 6 measured by temperature sensor 1. When T1 is much smaller than T... min At this time, the three-way solenoid valve 22 fully opens the circuit for cooling water to enter the circuit of check valve 31, and closes the circuit for cooling water to enter the circuit of check valve 23. At this time, D3 = 100%. As the heat preservation process continues, T1 gradually approaches T. min And exceed T minAt this point, it is necessary to reduce the opening degree D3 of the three-way solenoid valve 22, and calculate the change in valve opening D3”, D3”=k3(λ)[T1-(T best +T min [) / 2], k3(λ) is the nonlinear coefficient of valve opening, which is obtained by bench calibration. The final real-time opening of the three-way solenoid valve 322 is D3=D3'-D3”, where D3' is the opening of the previous control action of the three-way solenoid valve 322.

[0087] When only two of the three fuel cell stacks are not operating, the hydrothermal management algorithm only needs to adjust the valve openings of the two three-way solenoid valves at the front end of each of the two fuel cell stacks in real time, and maintain the temperature of that fuel cell stack at T. min ~T best between.

[0088] For example, when fuel cell stacks 2 and 3 are not working, it is necessary to adjust the real-time opening degree D1 of three-way solenoid valve 18 and the real-time opening degree D2 of three-way solenoid valve 25. Temperature sensor 2 measures the temperature T2 of fuel cell stack 213, and temperature sensor 3 measures the temperature T3 of fuel cell stack 320. When T2 is much smaller than T... min When the three-way solenoid valve 8 is fully open, the circuit for cooling water to enter the circuit of check valve 11 32 is closed, and the circuit for cooling water to enter the circuit of check valve 2 9 is closed. At this time, D1 = 100%. When T3 is much smaller than T... min At this time, the three-way solenoid valve 2 (15) fully opens the circuit for cooling water to enter the one-way valve 12 (33) and closes the circuit for entering the one-way valve 4 (16). At this time, D2 = 100%. It should be noted that only fuel cell stack 1 (6) is working at this moment; fuel cell stacks 2 and 3 are not working. However, fuel cell stack 2 (13) or fuel cell stack 3 (20) may have been working just moments before, and the temperature of fuel cell stack 2 (13) or fuel cell stack 3 (20) is relatively high. At the same time, since the heat source for the insulation of fuel cell stack 2 (13) comes from fuel cell stack 1 (6), and the heat source for the insulation of fuel cell stack 3 (20) comes from the remaining heat after fuel cell stack 2 (13) has absorbed the heat from the cooling water of fuel cell stack 1 (6), the opening degree of the three-way solenoid valve 1 (8) will affect the insulation temperature of both fuel cell stacks 2 and 3, while the opening degree of the three-way solenoid valve 2 (15) only affects the insulation temperature of fuel cell stack 3 (20). At this point, based on the temperature values ​​T2 and T3 measured by the temperature sensors for fuel cell stacks 13 and 20, when only one fuel cell is working in the system, the insulation temperature of the first non-working fuel cell needs to be fixed. That is, when fuel cell stack 6 is not working, the insulation temperature of fuel cell stack 13 is fixed at (T2 and T3). best +T min ) / 2, the change in opening degree of the three-way solenoid valve 8, D1”, D1”=k1(λ)[T2-(T best +T min) / 2],k1(λ) is the nonlinear coefficient of valve opening, obtained from bench calibration. The final real-time opening of the three-way solenoid valve 8 is D1=D1'-D1”, where D1' is the opening of the previous control action of the three-way solenoid valve 8. The change in opening of the three-way solenoid valve 15 is D2”,D2”=k2(λ){T2-[(T best +T min ) / 2+T min ] / 2}, k2(λ) is the nonlinear coefficient of valve opening, which is obtained from bench calibration. The final real-time opening of the three-way solenoid valve 215 is D2=D2'-D2”, where D2' is the opening of the previous control action of the three-way solenoid valve 215.

[0089] The multi-stall fuel cell cooling system control method described in this embodiment enables the alternating use of multiple fuel cell stacks, maintaining the consistency of the lifespan of each stack in the multi-stall fuel cell power system, thereby improving the system's service life. Even when one stack in the multi-stall fuel cell system fails, the system can still continue to supply power, demonstrating high system stability. It achieves precise control of both the preheating and operating temperatures of the multi-stall fuel cells, preventing heat accumulation and ensuring system stability, efficiency, and practicality.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A control method for a multi-stack fuel cell cooling system, characterized in that: The multi-stack fuel cell cooling system includes an intercooler, a cooling water tank, a water pump, and a PTC heater. The water pump inlet is connected to the cooling water tank, the water pump outlet is connected to the PTC heater, the PTC heater outlet is connected to three cooling branches, the three cooling branches are connected to the intercooler via a return water pipe, and the intercooler outlet is connected to the cooling water tank. The first cooling branch includes a switch valve 1, a check valve 7, a fuel cell stack 1, a thermostat 1, a three-way solenoid valve 1, and a check valve 2 connected in sequence via pipelines. The second cooling branch includes a switch valve 2, a check valve 8, a fuel cell stack 2, a thermostat 2, a three-way solenoid valve 2, and a check valve 2. The third cooling branch includes a switch valve 3, a check valve 9, a fuel cell stack 3, a thermostat 3, a three-way solenoid valve 3, and a check valve 3. The third ports of thermostats 1 to 3 are all connected to return water pipe 2, which is connected to a water pump. A check valve 11 is also connected between the third port of three-way solenoid valve 1 and fuel cell stack 2. A check valve 12 is also connected between the third port of three-way solenoid valve 2 and fuel cell stack 3. A check valve 10 is also connected between the third port of three-way solenoid valve 3 and fuel cell stack 1. The control method includes a preheating cold start phase and a multi-stacking normal operation phase. During cold start, the preheating cold start phase is activated. The FCU controls the opening of valves one to three, closes the circuit to return water pipe one, and simultaneously opens the circuit to other fuel cell stacks. The water pump and PTC heater are turned on, and cooling water preheats the three fuel cell stacks. When the temperatures of fuel cell stacks one to three all reach the preheating temperature T... min The system then enters the normal operation phase for multiple reactors. The PTC heater is turned off, and the FCU calculates the number and sequence number of the fuel cell stacks that need to operate. When only one fuel cell stack needs to operate, the switching valve of the cooling branch containing that stack opens, while the other two switching valves close. The FCU adjusts the opening of the two three-way solenoid valves at the front end of the two non-operating fuel cell stacks in real time, and closes the third interface of the other three-way solenoid valves, so that the temperature of the two non-operating fuel cell stacks is maintained at the preheating temperature T. min and optimal operating temperature T best between; When two fuel cells are required to operate, the switching valves of the cooling branches containing the two operating fuel cells are opened, while the remaining switching valves are closed. The FCU adjusts the valve opening of the three-way solenoid valve at the front end of the non-operating fuel cell in real time, and the third interface of the remaining three-way solenoid valves is closed, so that the temperature of the non-operating fuel cell is maintained at T. min To T best between; When all three fuel cells need to operate, the three switching valves open and the three three-way solenoid valves close the third port.

2. The control method for a multi-stack fuel cell cooling system according to claim 1, characterized in that, The method by which the FCU calculates the number and sequence number of the required fuel cell stacks is as follows: obtain the state of charge (SOC) and power demand (P) of the power battery. req Based on the state of charge (SOC) of the power battery and the required power P req Determine the power allocation method for 1 to n fuel cells, where n is 3; When SOC > A%, the power demand is met solely by the battery. When battery A% ≥ SOC > B%, if P req The maximum output power value P of less than one fuel cell stack stack_max That is, P stack_max >P req The power demand is met solely by the battery; if n*P stack_max ≥P req >(n-1)*P stack_max If n-1 stacks are activated, all n-1 stacks will output maximum power, and the remaining power demand will be met by the battery. When battery B% ≥ SOC, if P stack_max >P req If n*P, then one fuel cell stack is activated, which outputs maximum power, and excess energy is used to charge the battery until SOC > A%, at which point the fuel cell stack is shut down; stack_max ≥P req >(n-1)*P stack_max If n stacks are activated, all n stacks will output maximum power, and excess energy will be used to charge the battery until the battery SOC > A%, at which point the stacks will be shut down. The startup sequence of the above-mentioned fuel cell stacks is determined by the following method: The voltage value V at the rated power specified at the time of manufacture for each fuel cell stack was obtained based on bench tests. e During system operation, the actual output voltage V' of the fuel cell stack under rated operating conditions is measured. e The percentage of voltage decay of the fuel cell stack is obtained as D = (V e -V' e ) / V e Compare and sort the D values ​​of each fuel cell stack, prioritizing the stacks with the smallest degradation percentage. If the D values ​​are the same, the fuel cell stack with the shorter operating time T will operate.

3. The control method for a multi-stack fuel cell cooling system according to claim 2, characterized in that: A is 80, B is 20.

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