A multi-stack fuel cell cooling system with high energy utilization and a water-heat management method

Abstract

The present invention proposes a multi-stack fuel cell cooling system with high energy utilization and a hydrothermal management method. The system includes a cooling water tank, a water pump, a PTC heater and a thermostat, and a cooling water mixing tank. It also includes three cooling branches connecting the PTC heater and the cooling water mixing tank. Each cooling branch includes a switch valve, a fuel cell stack, a three-way solenoid valve and a one-way valve connected by a pipeline. The fuel cell stack is connected to a temperature sensor. The fuel cell stacks and the three-way solenoid valves of each two cooling branches are also connected by a one-way valve. After the front-end fuel cell stack of the system works normally, the waste heat generated can be used to keep the rear-end fuel cell stack warm. The rear-end fuel cell stack can be quickly started without consuming additional electricity, and the thermal energy utilization rate is high. The hydrothermal management method can improve the service life of the system, making it efficient and practical.

Description

Technical Field

[0001] The present invention belongs to the field of fuel cells, and in particular relates to a multi-stack fuel cell cooling system with high energy utilization and a water heat management method. Background Art

[0002] Currently, high-power fuel cells are too expensive, and the lifespan of a single stack is short. Once the degradation exceeds 20%, the entire system must be retired. A failure of a single fuel cell in a single stack can render the entire stack unusable. Using multiple low-power fuel cells instead of a single fuel cell can effectively increase the lifespan of the system. Since the system's power demand is constantly changing, multiple fuel cell stacks will not always be fully activated. They can be used alternately through an effective multi-stack energy distribution method, thereby extending the service life of the entire system. At the same time, the load-changing capacity of a single stack is limited. By decomposing the required power across multiple fuel cell stacks, the load-changing capacity of the entire system can also be improved. When a single fuel cell stack in a multi-stack fuel cell stack fails, the stack can be isolated, and then by rewriting the energy management strategy, the entire system can still be used normally.

[0003] Compared to a single fuel cell system, a multi-stack fuel cell system has many advantages, but the air intake system of a multi-stack fuel cell system is more complex, and its water and heat management circuit is also more complex. The design of the water and heat management circuit needs to ensure that each fuel cell stack can be maintained above its preheating temperature, otherwise the fuel cell stack will not be able to start when it is needed the next moment due to insufficient temperature. In the existing technology, electric heating is often used to maintain the temperature of the multi-stack fuel cell system, which requires additional electricity. The waste heat generated by the operation of the fuel cell stack itself cannot be effectively utilized, and the overall energy utilization rate of the system needs to be improved. Summary of the Invention

[0004] The present invention addresses the technical problem that the existing multi-stack fuel cell system uses electric heating to keep warm, and the overall energy utilization rate of the system needs to be improved. The present invention proposes a multi-stack fuel cell cooling system and a water heat management method with low system cost and high energy utilization rate.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A multi-stack fuel cell cooling system with high energy utilization efficiency includes a cooling water tank, a water pump, a PTC heater, and a thermostat. The water inlet of the water pump is connected to the cooling water tank, and the water outlet of the water pump is connected to the PTC heater. The first port of the thermostat is connected to the water pump, the second port is connected to the cooling water mixing tank, and the third port is connected to the intercooler. The water outlet of the intercooler is connected to the cooling water tank.

[0007] It also includes three cooling branches connecting the PTC heater and the cooling water mixing tank. Each cooling branch includes a switch valve, a battery stack, a three-way solenoid valve and a one-way valve connected by pipelines. A temperature sensor is connected to the battery stack. The battery stack and the three-way solenoid valve of each two cooling branches are also connected by a one-way valve.

[0008] Preferably, the system further includes a controller, which communicates and controls the switch valve, water pump, PTC heater, three-way solenoid valve and temperature sensor via a CAN network.

[0009] A multi-stack fuel cell water and heat management method with high energy utilization efficiency includes a preheating cold start phase and a multi-stack normal operation phase. During a cold start, the preheating cold start phase is executed, the FCU controls switch valves one to three to open, the three three-way solenoid valves all close the circuits leading to the other fuel cells and simultaneously open the circuit leading to the cooling water mixing tank. The water pump and PTC heater are turned on, and the cooling water is preheated for the three fuel cells. When the temperature in the cooling water mixing tank reaches the preheating temperature Tmin, the multi-stack normal operation phase is entered.

[0010] The PTC heater is turned off, and the FCU calculates the number and sequence number of the stacks that need to be worked on;

[0011] The valve opening of the three-way solenoid valve at the front end of the non-working fuel cell stack is adjusted in real time to maintain the temperature of the non-working fuel cell stack between the preheating temperature Tmin and the optimal operating temperature Tbest; the other three-way solenoid valves remain closed to the circuits leading to other fuel cells while opening the circuits leading to the cooling water mixing tank.

[0012] Preferably, the FCU calculates the number and sequence of the battery stacks that need to be operated by: obtaining the power battery state of charge SOC and the required power Preq, and determining the power distribution method of 1 to n battery stacks based on the power battery state of charge SOC and the required power Preq, where n is 3;

[0013] When SOC>A%, the power demand is met by the battery alone;

[0014] When battery A% ≥ SOC > B%, if Preq is less than the maximum output power value of one fuel cell stack, that is, Pstack_max > Preq, the power demand is met by the battery alone; if n*Pstack_max ≥ Preq > (n-1)*Pstack_max, then n-1 fuel cells are started, and these n-1 fuel cells all output maximum power, and the remaining power demand is met by the battery;

[0015] When battery B% ≥ SOC, if Pstack_max > Preq, then start one stack, which outputs maximum power, and uses excess energy to charge the battery until SOC > A%, then shut down the stack; if n*Pstack_max ≥ Preq > (n-1)*Pstack_max, then start n stacks, which all output maximum power, and use excess energy to charge the battery until SOC > A%, then shut down the stack;

[0016] The startup sequence of the above stack is determined by the following method:

[0017] The voltage value Ve of each fuel cell stack at rated power, which is calibrated at the factory, is obtained through bench testing. The actual output voltage value V'e of the fuel cell stack under rated operating conditions is measured during system operation. The degradation percentage of the fuel cell stack voltage is obtained as D = (Ve-V'e) / Ve. ​​The D values ​​of each fuel cell stack are compared and sorted, and the fuel cell stack with the smallest degradation percentage is prioritized.

[0018] If the D values ​​are the same, it is further preferred to operate the battery stack with a shorter operating time T.

[0019] Preferably, A is 80 and B is 20. Preferably,.

[0020] Compared with the prior art, the advantages and positive effects of the present invention are:

[0021] 1. The multi-stack fuel cell cooling system only requires one water pump, one PTC heater, one intercooler, and one thermostat, with a simple system structure and low cost.

[0022] 2. Each battery stack has its own cooling branch. During cold start, it can be quickly preheated by cooling water heated by the PTC heater to quickly reach the preheating temperature.

[0023] 3. In addition to providing a cooling branch for each stack, the three cooling branches are also connected by pipes, forming a preheating and insulation circuit in which the coolant flows from stack 1, through stack 2, through stack 3, and then back to stack 1. Therefore, the heat generated by one stack after operation can be used to insulate the second stack or the remaining stacks, reducing the additional heat required for insulation of the second stack or the remaining stacks and improving the energy utilization of the system. After the front stack is operating normally, the rear stack can be quickly started without consuming additional electricity, and when the rear stack is operating normally, its normal heat dissipation function will not be affected.

[0024] 4. The hydrothermal management method enables the alternating use of multiple fuel cell stacks, maintaining the consistency of the lifespan of each fuel cell stack in a multi-stack fuel cell power system, thereby extending the system's service life. Even if a fuel cell stack in a multi-stack fuel cell system fails, the system can still continue to supply power, providing high system stability.

[0025] 5. The preheating temperature and operating temperature of multiple fuel cell stacks are precisely controlled, avoiding heat accumulation and ensuring the stability of system operation, efficiency and practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic structural diagram of a multi-stack fuel cell cooling system according to the present invention;

[0027] Figure 2 This is a control network connection diagram of the multi-stack fuel cell cooling system of the present invention;

[0028] Figure 3 This is a schematic structural diagram of the power system involved in the multi-stack fuel cell cooling system of the present invention;

[0029] In the above figures: 1. Cooling water tank; 2. Water pump; 3. PTC heater; 4. Thermostat; a. First port; b. Second port; c. Third port; 5. Intercooler; 6. Cooling water mixing tank; 7. Switch valve one; 8. Fuel cell one; 9. Three-way solenoid valve one; 10. Check valve one; 11. Temperature sensor one; 12. Switch valve two; 13. Fuel cell two; 14. Three-way solenoid valve two; 15. Check valve two; 16. Temperature sensor two; 17. Switch valve three; 18. Fuel cell three; 19. Three-way solenoid valve three; 20. Check valve three; 21. Temperature sensor three; 22. Check valve four; 23. Check valve five; 24. Check valve six. DETAILED DESCRIPTION

[0030] In order to better understand the present invention, the following is a detailed description with reference to the accompanying drawings and embodiments.

[0031] Example: Figure 1 As shown, a multi-stack fuel cell cooling system with high energy utilization efficiency includes a cooling water tank 1, a water pump 2, a PTC heater 3 and a thermostat 4. The water inlet of the water pump 2 is connected to the cooling water tank 1, and the water outlet of the water pump 2 is connected to the PTC heater 3; the first port of the thermostat 4 is connected to the water pump 2, the second port is connected to the cooling water mixing tank 6, and the third port is connected to the intercooler 5. The water outlet of the intercooler 5 is connected to the cooling water tank 1;

[0032] It also includes three cooling branches connecting the PTC heater 3 and the cooling water mixing box 6. The first cooling branch includes a switch valve 7, a battery stack 8, a three-way solenoid valve 9 and a one-way valve 10 connected via a pipeline, and the battery stack 8 is connected to a temperature sensor 11; the second cooling branch includes a switch valve 2 12, a battery stack 2 13, a three-way solenoid valve 2 14 and a one-way valve 2 15 connected via a pipeline, and the battery stack 2 13 is connected to a temperature sensor 2 16; the third cooling branch includes a switch valve 3 17, a battery stack 3 18, a three-way solenoid valve 3 19 and a one-way valve 3 20 connected via a pipeline, and the battery stack 3 18 is connected to a temperature sensor 3 21; a one-way valve 4 22 is connected between the three-way solenoid valve 19 and the battery stack 2 13, a one-way valve 5 23 is connected between the three-way solenoid valve 2 14 and the battery stack 3 18, and a one-way valve 6 24 is connected between the three-way solenoid valve 3 19 and the battery stack 1 8, forming a connecting channel between the three cooling branches.

[0033] It also includes a fuel cell controller (FCU), which communicates and controls the three switch valves, water pump 2, PTC heater 3, three-way solenoid valve and temperature sensor through the CAN network. The CAN network structure is as follows: Figure 2 shown.

[0034] The operation process of the multi-stack fuel cell cooling system refers to the second embodiment.

[0035] This multi-stack fuel cell cooling system requires only one water pump, a PTC heater, an intercooler, and a thermostat, resulting in a simple system structure and low cost. A cooling water mixing tank is installed within the system. After the cooling water from multiple channels is mixed in the cooling water mixing tank, the water temperature at the cooling water mixing tank outlet does not fluctuate significantly, and the cooling fan of the rear-end intercooler does not frequently change speed. The cooling water mixing tank itself also has a certain heat dissipation function. When there are fewer working fuel cells, it can even rely on its own natural heat dissipation, eliminating the need to start the intercooler fan. When the water circuit is in a small loop, ensure that the cooling water temperature at the water pump inlet does not fluctuate much, otherwise it will increase the difficulty of adjusting the valves at the rear end of the fuel cell stack.

[0036] The cooling system is equipped with three cooling branches, and each fuel cell stack has an independent cooling branch. During cold start, the cooling water heated by the PTC heater can be quickly preheated to quickly reach the preheating temperature. In addition to setting up the cooling branch for each fuel cell stack, the three cooling branches are also connected by pipes to form a preheating and insulation circuit in which the coolant flows from fuel cell stack one, through fuel cell stack two, through fuel cell stack three, and then back to fuel cell stack one. Therefore, the heat generated after one stack is working can be used to insulate the second stack or the remaining stacks, reducing the additional heat required to keep the second stack or the remaining stacks warm, and improving the energy utilization of the system. After the front-end fuel cell stack is working normally, the rear-end fuel cell stack can be quickly started without consuming additional electricity, and when the rear-end fuel cell stack is working normally, it will not affect its normal heat dissipation function.

[0037] Example 2

[0038] A multi-stack fuel cell water and heat management method with high energy utilization rate includes a preheating cold start link and a multi-stack normal operation link.

[0039] Warm-up cold start phase:

[0040] During a cold start, the battery stack temperature is too low to operate properly. Low-voltage power is applied to the vehicle, and battery stacks 1-3 begin preheating. The FCU controls valves 1-3 to open. The FCU controls three-way solenoid valve 1-9 to close the circuit leading to check valve 4 22 and simultaneously opens the circuit leading to check valve 1-10. Cooling water flows from valve 1-7 through three-way solenoid valve 1-9 and check valve 1-10 into cooling water mixing tank 6. The FCU controls three-way solenoid valve 2-14 to close the circuit leading to check valve 5 23 and simultaneously opens the circuit leading to check valve 2-15. Cooling water flows from valve 2-12 through three-way solenoid valve 2-14 and check valve 2-15 into cooling water mixing tank 6. The FCU controls three-way solenoid valve 3-19 to close the circuit leading to check valve 6 24 and simultaneously opens the circuit leading to check valve 3-20. Cooling water flows from valve 3-17 through three-way solenoid valve 3-19 and check valve 3-20 into cooling water mixing tank 6. The FCU controls water pump 2 to open and PTC heater 3 to turn on. After being heated by the PTC, the cooling water returns to the cooling water mixing tank 6 through its own one-way valve. It then enters the water pump 2 through the small loop of the thermostat 4 to accelerate the preheating of the stacks 1 to 3. As the preheating progresses, the cooling water temperature in the cooling water mixing tank 6 gradually reaches the temperature value T at which the large loop of the thermostat 4 is opened. min , T min This is also the preheating target temperature for stacks 1 to 3. At this point, the thermostat 4 large loop opens first, and most of the cooling water in the cooling water mixing tank 6 flows through the thermostat 4 large loop and intercooler 5 into the cooling water tank 1. A small amount of cooling water flows through the thermostat 4 small loop into the water pump 2.

[0041] Normal operation and insulation of multiple stacks: After the preheating cold start of stacks 1 to 3 is completed, PTC heater 3 is turned off, and the FCU calculates the sequence number of the stack that needs to work based on the energy management algorithm and determines the working status of three-way solenoid valves 1 to 3.

[0042] Common multi-stack fuel cell power system structures such as Figure 3 The main components shown are stacks 1-3, batteries, DC / DC converters 1-3, voltage sensors 1-3, a motor controller, and a motor. The batteries and stacks 1-3 are connected in parallel to the busbar to power the motor controller, which controls the motor's speed and torque based on the vehicle's driving requirements. Voltage sensors 1-3 measure the voltage of stacks 1-3, respectively.

[0043] The energy management algorithm is as follows:

[0044] First, obtain the power battery state of charge SOC and required power P req , calculate the number of battery stacks that need to work according to the required power. When selecting battery stacks one to three, the maximum power required by the system is P req_max Less than the maximum output power P of the three stacks stack_max The sum of 3*P stack_max >P req_max .

[0045] When the battery SOC>80%, the battery alone meets the system power demand, and the battery output power P bat =P req .

[0046] When the battery 80% ≥ SOC>20%, according to the required power P req Calculate the power distribution of batteries and stacks 1 to 3. If P req Less than the maximum output power value of one battery stack, that is, P stack_max >P req , at this time only the battery is working, and the power demand is met by the battery alone; if P req Greater than or equal to the maximum output power of one battery stack and less than the sum of the maximum output power values ​​of two battery stacks, that is, 2*P stack_max ≥P req >P stack_max , then start one battery stack, which outputs the maximum power, and the remaining power demand is met by the battery; if P req Greater than the maximum output power of two fuel cells and less than the sum of the maximum output power values ​​of three fuel cells, that is, 3*P stack_max ≥P req >2*P stack_max , then two fuel cells are started, both of which output maximum power, and the remaining power demand is met by the battery.

[0047] When the battery 20% ≥ SOC, according to the required power P req Calculate the power distribution of batteries and stacks 1 to 3. If P req Less than the maximum output power value of one battery stack, that is, P stack_max >P req , then start one stack, which outputs a portion of the maximum power to meet the system power demand, and the excess energy is used to charge the battery until the battery SOC>80%, after which the stack is shut down; if P req Greater than or equal to the maximum output power of one battery stack and less than the sum of the maximum output power values ​​of two battery stacks, that is, 2*P stack_max ≥P req >P stack_max, then start two stacks, both of which output maximum power. A part of the power output by the two stacks meets the system power demand, and the excess energy is used to charge the battery until the battery SOC>80%, after which the stack is shut down; if P req Greater than the maximum output power of two fuel cells and less than the sum of the maximum output power values ​​of three fuel cells, that is, 3*P stack_max ≥P req >2*P stack_max , then three fuel cells are started, and all three fuel cells output maximum power. Part of the power output by the three fuel cells meets the system power demand, and the excess energy is used to charge the battery until the battery SOC>80%, after which the fuel cell is shut down.

[0048] The startup sequence of the three stacks is determined by the following method:

[0049] The voltage value V at the rated power of stacks 1 to 3 is obtained according to the bench test. e1 , V e2 , V e3 , and measure the actual output voltage value V' of stacks 1 to 3 under rated working conditions during system operation e1 , V' e2 , V' e3 The decay percentage of the voltage of the stack from 1 to 3 is D1 = (V e1 -V' e1 ) / V e1 , D2=(V e2 -V' e2 ) / V e2 , D3=(V e3 -V' e3 ) / V e3 Compare the sizes of D1, D2, and D3 and sort them. The stack with the smaller stack degradation percentage will be activated first. For example, D3>D1>D2. If both stacks are required, then both stack 1 and stack 2 will be activated. If only one stack is required, then stack 2 will be activated.

[0050] If D1 = D2 = D3, the stack is activated based on its historical operating hours. The stack's historical operating hours are stored as T1, T2, and T3, with the stack with the shorter operating hours taking priority. For example, T3 > T1 > T2. If both stacks are required, stack 1 (8) and stack 2 (13) are activated. If only one stack is required, stack 2 (13) is activated. If another stack has the same D and T values, one of the two stacks is randomly selected for operation.

[0051] The following describes the system working status in detail based on the working conditions of the specific battery stack.

[0052] (1) If only the first stack 8 needs to work, and the second stack 13 and the third stack 18 do not need to work, then the temperature of the second stack 13 and the third stack 18 needs to be kept at the preheating temperature T min And the best working temperature T best The switch valve 1 7 is kept open, the switch valves 2 and 3 are closed, and the three-way solenoid valve 3 19 closes the circuit entering the one-way valve 6 24 and opens the circuit entering the one-way valve 3 20.

[0053] The cooling water flows into the fuel cell stack 18 through the switch valve 17 and absorbs the heat of the fuel cell stack 18 before flowing into the three-way solenoid valve 19. At this time, the three-way solenoid valve 19 distributes the flow of cooling water into the one-way valve 10 and the one-way valve 4 22 according to the water thermal management algorithm.

[0054] After flowing into three-way solenoid valve 1 (9), the cooling water flows through one-way valve 1 (10) into the cooling water mixing tank 6 and then through one-way valve 4 (22) into the fuel cell stack 2 (13). The cooling water flows into the fuel cell stack 2 (13) to insulate it before flowing through the outlet into three-way solenoid valve 2 (14). Three-way solenoid valve 2 (14) then distributes the cooling water flow to one-way valve 2 (15) and one-way valve 5 (23) based on a water thermal management algorithm.

[0055] After flowing into three-way solenoid valve 2 (14), the cooling water flows through one-way valve 2 (15) into the cooling water mixing tank (6) and then through one-way valve 5 (23) into the cell stack (18). The cooling water flows into the cell stack (18) to maintain its temperature before flowing through the outlet into three-way solenoid valve 3 (19). The cooling water flows through three-way solenoid valve 3 (19) and one-way valve 3 (20) into the cooling water mixing tank (6).

[0056] The water thermal management algorithm controls the flow of the incoming stack 2 13 through the three-way solenoid valve 19 to ensure that the temperature of the stack 2 13 is greater than T min and is less than the optimal operating temperature T of the fuel cell best The water thermal management algorithm controls the flow of water into the stack 3 18 through the three-way solenoid valve 2 14 to ensure that the temperature of the stack 3 18 is greater than T min and is less than the optimal operating temperature T of the fuel cell best .

[0057] (2) If only the second stack 13 needs to work, and the first stack 8 and the third stack 18 do not need to work, then the temperature of the first and third stacks needs to be kept at the preheating temperature T min And the best working temperature T best The switch valve 2 12 remains open, the switch valve 1 7 and the switch valve 3 are closed, and the three-way solenoid valve 1 9 closes the circuit to the check valve 4 22 and opens the circuit to the check valve 1 10.

[0058] The cooling water flows into the fuel cell stack 2 13 through the switch valve 2 12 and absorbs the heat of the fuel cell stack 2 13 before flowing into the three-way solenoid valve 2 14 . At this time, the three-way solenoid valve 2 14 distributes the flow of cooling water into the one-way valve 2 15 and the one-way valve 5 23 according to the water thermal management algorithm.

[0059] After flowing into three-way solenoid valve 2 (14), the cooling water flows through one-way valve 2 (15) into the cooling water mixing tank 6 and then through one-way valve 5 (23) into the fuel cell stack 3 (18). The cooling water flows into the fuel cell stack 3 (18) to maintain its temperature before flowing out of the outlet into three-way solenoid valve 3 (19). Three-way solenoid valve 3 (19) then distributes the cooling water flow to one-way valve 3 (20) and one-way valve 6 (24) based on a water thermal management algorithm.

[0060] After flowing into three-way solenoid valve 3 (19), the cooling water flows through one-way valve 3 (20) into the cooling water mixing tank 6 and another through one-way valve 6 (24) into the fuel cell stack 1 (8). The cooling water flows into the fuel cell stack 1 (8) to maintain its temperature before flowing through the outlet into three-way solenoid valve 1 (9). The cooling water flows through three-way solenoid valve 1 (9) and through one-way valve 10 into the cooling water mixing tank 6.

[0061] The water thermal management algorithm controls the flow of the incoming stack 3 18 through the three-way solenoid valve 2 14 to ensure that the temperature of the stack 3 18 is greater than T min and is less than the optimal operating temperature T of the fuel cell best The water thermal management algorithm controls the flow into the stack 8 through the three-way solenoid valve 319 to ensure that the temperature of the stack 8 is greater than T min and is less than the optimal operating temperature T of the fuel cell best .

[0062] (3) If only the stack 3 18 needs to work, and the stack 1 8 and the stack 2 13 do not need to work, then the temperature of the stack 1 8 and the stack 2 13 needs to be kept at the preheating temperature T min And the best working temperature T best The switch valve 3 17 is kept open, the switch valve 1 7 and the switch valve 2 are closed, the three-way solenoid valve 2 14 closes the circuit entering the one-way valve 5 23, and opens the circuit entering the one-way valve 2 15.

[0063] The cooling water flows into the fuel cell stack three 18 through the switch valve three 17 and absorbs the heat of the fuel cell stack three 18 before flowing into the three-way solenoid valve three 19. At this time, the three-way solenoid valve three 19 distributes the flow of cooling water into the one-way valve three 20 and the one-way valve six 24 according to the water thermal management algorithm.

[0064] After flowing into three-way solenoid valve 3 19, the cooling water flows through one-way valve 3 20 into the cooling water mixing tank 6 and another through one-way valve 6 24 into the fuel cell stack 1 8. The cooling water flows into the fuel cell stack 1 8 to maintain its temperature before flowing out of the outlet into three-way solenoid valve 1 9. At this point, three-way solenoid valve 1 9 distributes the cooling water flow to one-way valve 10 and one-way valve 4 22 according to the water thermal management algorithm.

[0065] After flowing into three-way solenoid valve 1 (9), the cooling water flows through one-way valve 1 (10) into the cooling water mixing tank 6 and then through one-way valve 4 (22) into the cell stack 2 (13). The cooling water flows into the cell stack 2 (13) to maintain its temperature before flowing through the outlet into three-way solenoid valve 2 (14). The cooling water flows through three-way solenoid valve 2 (14) and one-way valve 2 (15) into the cooling water mixing tank 6.

[0066] The water thermal management algorithm controls the flow of water into the stack 8 through the three-way solenoid valve 319 to ensure that the temperature of the stack 8 is greater than T min and is less than the optimal operating temperature T of the fuel cell best The water thermal management algorithm controls the flow of water into the stack 13 through the three-way solenoid valve 19 to ensure that the temperature of the stack 13 is greater than T min and is less than the optimal operating temperature T of the fuel cell best .

[0067] (4) If the stack 1 8 and the stack 2 13 need to work, the stack 3 18 does not need to work. At this time, the temperature of the stack 3 18 needs to be kept at the preheating temperature T min And the best working temperature T best The valves are kept in a closed position so that they can start working quickly when needed. On-off valves 1 (7) and 2 (2) remain open, while on-off valve 3 (17) is closed. Three-way solenoid valve 1 (9) closes the circuit to check valve 4 (22) and opens the circuit to check valve 1 (10). Three-way solenoid valve 3 (19) closes the circuit to check valve 6 (24) and opens the circuit to check valve 3 (20).

[0068] The cooling water flows into the fuel cell stack 8 through the switch valve 7 and absorbs the heat of the fuel cell stack 8, then flows into the three-way solenoid valve 9, and flows into the cooling water mixing tank 6 through the one-way valve 10.

[0069] The cooling water flows into the fuel cell stack 2 13 through the switch valve 2 12 and absorbs the heat of the fuel cell stack 2 13 before flowing into the three-way solenoid valve 2 14 . At this time, the three-way solenoid valve 2 14 distributes the flow of cooling water into the one-way valve 2 15 and the one-way valve 5 23 according to the water thermal management algorithm.

[0070] After flowing into three-way solenoid valve 2 14, the cooling water flows through one-way valve 2 15 into the cooling water mixing tank 6 and through one-way valve 5 23 into the cell stack 3 18. The cooling water flows into the cell stack 3 18 to keep it warm before flowing out of the water outlet, passing through three-way solenoid valve 3 19 and one-way valve 3 20 into the cooling water mixing tank 6.

[0071] (5) If the stack 1 8 and the stack 3 need to work, the stack 2 13 does not need to work. At this time, the temperature of the stack 2 13 needs to be kept at the preheating temperature T min And the best working temperature T best The valves are kept open so they can begin working quickly when needed. On-off valves 1 and 3 remain open, while on-off valve 2 12 is closed. Three-way solenoid valve 2 14 closes the circuit leading to check valve 5 23 and opens the circuit leading to check valve 1 10. Three-way solenoid valve 3 19 closes the circuit leading to check valve 6 24 and opens the circuit leading to check valve 3 20.

[0072] The cooling water flows into the fuel cell stack 3 18 through the switch valve 3 17 and absorbs the heat of the fuel cell stack 3 18 before flowing into the three-way solenoid valve 3 19 and flows into the cooling water mixing box 6 through the one-way valve 3 20.

[0073] The cooling water flows into the fuel cell stack 18 through the switch valve 17 and absorbs the heat of the fuel cell stack 18 before flowing into the three-way solenoid valve 19. At this time, the three-way solenoid valve 19 distributes the flow of cooling water into the one-way valve 10 and the one-way valve 4 22 according to the water thermal management algorithm.

[0074] After flowing into three-way solenoid valve 1 (9), the cooling water flows through one-way valve 1 (10) into the cooling water mixing tank 6 and then through one-way valve 4 (22) into the cell stack 2 (13). The cooling water flows into the cell stack 2 (13), insulates the cell stack 2, then flows out of the outlet, through three-way solenoid valve 2 (14) and one-way valve 2 (15), and into the cooling water mixing tank 6.

[0075] (6) If the stack 2 13 and the stack 3 18 need to work, the stack 1 8 does not need to work. At this time, the temperature of the stack 1 8 needs to be kept at the preheating temperature T min And the best working temperature T best The valves are kept open so they can quickly begin operation when needed. On-off valves 2 (12) and 3 (7) remain open, while on-off valve 1 (7) is closed. Three-way solenoid valve 2 (14) closes the circuit leading to check valve 5 (23) and opens the circuit leading to check valve 2 (15). Three-way solenoid valve 1 (9) closes the circuit leading to check valve 4 (22) and opens the circuit leading to check valve 1 (10).

[0076] The cooling water flows into the second fuel cell stack 13 through the second switch valve 12 and absorbs the heat of the second fuel cell stack 13 , then flows into the second three-way solenoid valve 14 , and flows into the cooling water mixing tank 6 through the second one-way valve 15 .

[0077] The cooling water flows into the fuel cell stack three 18 through the switch valve three 17 and absorbs the heat of the fuel cell stack three 18 before flowing into the three-way solenoid valve three 19. At this time, the three-way solenoid valve three 19 distributes the flow of cooling water into the one-way valve three 20 and the one-way valve six 24 according to the water thermal management algorithm.

[0078] After flowing into three-way solenoid valve 3 19, the cooling water flows through one-way valve 3 20 into the cooling water mixing tank 6 and another through one-way valve 6 24 into the cell stack 1 8. The cooling water flows into the cell stack 1 8 to keep it warm before flowing out of the outlet, passing through three-way solenoid valve 19 and one-way valve 10 into the cooling water mixing tank 6.

[0079] (7) If the stack 1 8 and the stacks 2 13 and 3 need to work, there is no need to consider the preheating and heat preservation of the stacks 1 to 3, but only the heat dissipation of the three stacks needs to be considered. The switch valves 1 to 3 are all opened, the three-way solenoid valve 1 9 closes the circuit entering the one-way valve 4 22 and opens the circuit entering the one-way valve 1 10; the three-way solenoid valve 2 14 closes the circuit entering the one-way valve 5 23 and opens the circuit entering the one-way valve 2 15; the three-way solenoid valve 3 19 closes the circuit entering the one-way valve 6 24 and opens the circuit entering the one-way valve 3 20.

[0080] Shutdown phase: Water pump 2 is shut down, switch valves 1 to 3 are all closed, and the system shuts down.

[0081] The multi-stack fuel cell power system includes stacks 1-3, batteries, DC / DC converters 1-3, voltage sensors 1-3, a motor controller, and a motor. The batteries and stacks 1-3 are connected in parallel to the busbar to power the motor controller, which controls the motor's speed and torque based on the vehicle's driving requirements. Voltage sensors 1-3 measure the voltage of stacks 1-3, respectively. The multi-stack fuel cell power system is as follows:

[0082] The valve opening control algorithm of three-way solenoid valves one to three is mainly as follows:

[0083] When only one of the three stacks is not working, the water thermal management algorithm only needs to adjust the valve opening of the three-way solenoid valve at the front end of the inoperative stack in real time and keep the temperature of the stack at T min ~T best The three-way solenoid valve at the front end of the stack 1 is the three-way solenoid valve 3, the three-way solenoid valve at the front end of the stack 2 is the three-way solenoid valve 1, and the three-way solenoid valve at the front end of the stack 3 is the three-way solenoid valve 2. For example, when the stack 1 8 is not working, it is necessary to adjust the real-time opening D3 of the three-way solenoid valve 3 19. The temperature sensor 1 measures the temperature T1 of the stack 1 8. The opening of the three-way solenoid valve 3 19 adopts a thermostat control strategy. When T best >T1, the three-way solenoid valve 3 19 is connected to the circuit of the one-way valve 6 24 and closed to the circuit of the one-way valve 3 20. bestWhen , the three-way solenoid valve 3 19 is connected to the circuit of the one-way valve 3 20 and closed to the circuit of the one-way valve 6 24.

[0084] When only two of the three stacks are not working, the water thermal management algorithm only needs to adjust the valve opening of the two three-way solenoid valves at the front end of the two stacks in real time and keep the temperature of the stack at T min ~T best For example, when the stack 2 13 and the stack 3 18 are not working, it is necessary to adjust the real-time opening D1 of the three-way solenoid valve 1 9 and the real-time opening D2 of the three-way solenoid valve 2 14. Due to the preheating process or the operation of the stack 2 13 and the stack 3 18 at the last moment, the temperature of the stack 2 13 and the stack 3 18 are both higher than T min The main function of the three-way solenoid valve 19 is to ensure that the temperature of the stack 2 13 is within T min ~T best At the same time, the cooling water coming out of the water outlet of the stack 2 13 is sufficient to keep the temperature of the stack 3 18 at T min ~T best Since the opening of the three-way solenoid valve 19 will not only affect the temperature of the battery stack 2 13 but also the temperature of the battery stack 3 18, it is necessary to control the temperature of the battery stack 2 13 to be constant, and the cooling water from the water outlet of the battery stack 2 13 can ensure that the temperature of the battery stack 3 18 is at T min ~T best The temperature of the fixed stack 13 is equal to (T min +T best ) / 2 (When the three-way solenoid valve 9 is fully opened and the cooling water enters the circuit of the one-way valve 4 22, and closes the circuit of the one-way valve 10, D1 = 100%). The current opening of the solenoid valve is D1', and the change in the opening of the three-way solenoid valve 9 is D1", D1" = k1(λ)[T2-(T best +T min ) / 2], k1(λ) is the nonlinear coefficient of valve opening, obtained by bench calibration. The final real-time valve opening of the three-way solenoid valve 19 is D1=D1'-D1". The control of the three-way solenoid valve 19 adopts the thermostat control strategy. When T best >T3, the three-way solenoid valve 3 19 is connected to the circuit of the one-way valve 6 24 and closed to the circuit of the one-way valve 3 20. best When , the three-way solenoid valve 3 19 is connected to the circuit of the one-way valve 3 20 and closed to the circuit of the one-way valve 6 24.

[0085] The high-energy-efficiency multi-stack fuel cell hydrothermal management method described in this embodiment can achieve the alternating use of multiple fuel cells, maintain the consistency of the life of each fuel cell in the multi-stack fuel cell power system, and thus improve the service life of the system. When a fuel cell in the multi-stack fuel cell system fails, the system can still continue to supply power, and the system stability is high. The preheating temperature and operating temperature of the multi-stack fuel cells are precisely controlled, avoiding heat accumulation, ensuring the stability of the system operation, and being efficient and practical.

[0086] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any person skilled in the art may utilize the technical contents disclosed above to change or modify them into equivalent embodiments with equivalent changes for application in other fields. However, any simple modification, equivalent change, and modification of the above embodiments made in accordance with the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A multi-stack fuel cell hydrothermal management method with high energy utilization, characterized by: The multi-stack fuel cell comprises a cooling water tank, a water pump, a PTC heater and a thermostat, wherein the water inlet of the water pump is connected to the cooling water tank, and the water outlet of the water pump is connected to the PTC heater; the first port of the thermostat is connected to the water pump, the second port is connected to the cooling water mixing tank, the third port is connected to the intercooler, and the water outlet of the intercooler is connected to the cooling water tank; the multi-stack fuel cell comprises three cooling branches connecting the PTC heater and the cooling water mixing tank, each cooling branch comprises a switch valve, a fuel cell stack, a three-way solenoid valve and a one-way valve connected by a pipeline, a temperature sensor is connected to the fuel cell stack, and the fuel cell stack and the three-way solenoid valve of each two cooling branches are also connected by a one-way valve; The hydrothermal management method includes a preheating cold start link and a normal operation link of multiple stacks. When the preheating cold start link is run during cold start, the FCU controls the three switch valves to open, the three three-way solenoid valves all close the circuits leading to other stacks and open the circuit connected to the cooling water mixing box at the same time, the water pump and the PTC heater are turned on, and the cooling water is preheated for the three stacks. When the temperature in the cooling water mixing box reaches the preheating temperature T min When running, it enters the normal working link of multiple stacks; The PTC heater is turned off, and the FCU calculates the number and sequence number of the stacks that need to be worked on; Adjust the valve opening of the three-way solenoid valve at the front end of the non-working stack in real time to maintain the temperature of the non-working stack at the preheating temperature T min and the optimal operating temperature T best The other three-way solenoid valves remain closed to the circuits leading to other fuel cells while opening the circuits connected to the cooling water mixing tank; The method for FCU to calculate the number and serial number of the battery stacks that need to be worked is as follows: obtain the power battery state of charge SOC and required power P req , based on the power battery state of charge SOC and required power P req Determine the power distribution method for 1 to n stacks, where n is 3; When SOC>A%, the power demand is met by the battery alone; When battery A%≥SOC>B%, if P req Less than the maximum output power value of one battery stack, that is, P stack_max >P req , the power demand is met by the battery alone; if n P stack_max ≥P req >(n-1) P stack_max , then n-1 stacks are started, and these n-1 stacks all output maximum power, and the remaining power demand is met by the battery; When battery B%≥SOC, if P stack_max >P req , then start one stack, which outputs maximum power and uses the excess energy to charge the battery until SOC>A%, then shut down the stack; if n P stack_max ≥P req >(n-1) P stack_max , then start n stacks, all of which output maximum power, and use the excess energy to charge the battery until the battery SOC is greater than A%, and then shut down the stack; A is 80, B is 20; The startup sequence of the above stack is determined by the following method: The voltage value V at the rated power of each battery stack calibrated at the factory is obtained based on the bench test e , and measure the actual output voltage value V' of the stack under rated working conditions during system operation e , the decay percentage of the stack voltage is obtained as D=(V e -V' e ) / V e ; Compare the D values ​​of each stack and sort them, and the stack with the smallest stack degradation percentage will work first; If the D values ​​are the same, the stack with the shorter working time T will work.

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