A control method for stabilizing and rapidly warming up a fuel cell system

Abstract

The application discloses a control method for stabilizing and quickly heating a fuel cell system. The method is that a three-way valve is arranged among a radiator, a PTC heater and an electric pile, and switching of a large circulation water path and a small circulation water path is realized by controlling the opening degree of the three-way valve. In the heating stage or the cold starting stage, the maximum power loadable at present is controlled by the maximum pressure difference of the water path and the air path, the water pump rotating speed is autonomously adjusted according to the temperature difference of the water inlet and outlet of the electric pile, the electric pile is kept in a reasonable working temperature interval, the pressure difference of the water path and the air path and the system power limit are released when the flow resistance of the PTC heater does not affect the switching of the water path into the large circulation water path, and the full power response to the demand of the whole vehicle is performed.

Description

Technical Field

[0001] This invention belongs to the field of fuel cells, and specifically relates to a control method for a stable and rapid heat engine in a fuel cell system. Background Technology

[0002] A hydrogen fuel cell system is an energy system that generates electricity through an electrochemical reaction between hydrogen and oxygen. It boasts advantages such as cleanliness, high efficiency, and environmental friendliness, and is considered one of the potential technologies to replace traditional internal combustion engines. The hydrogen fuel cell system produces electricity and water by reacting hydrogen and oxygen in an electrochemical stack. A typical reaction involves hydrogen undergoing oxidation at the anode (negative electrode), releasing electrons to form hydrogen ions; oxygen undergoes reduction at the cathode (positive electrode), combining with hydrogen ions and electrons to form water, while simultaneously releasing electrons. These electrons flow in an external circuit to form an electric current, driving an electric motor. It is a power generation device that can directly convert the chemical energy of fuel into electrical energy without combustion, offering advantages such as high conversion efficiency, environmental friendliness, low noise, and rapid start-up at low temperatures.

[0003] Currently, the startup warm-up scheme for fuel cell systems involves gradually increasing the water circuit temperature to a suitable operating temperature during the small circulation phase, then gradually expanding to the large circulation phase. Temperature limits are used to restrict the load power during warm-up, setting different load capacities based on different stack temperatures. This results in slow warm-up speeds and long cold start times, causing the system to lag behind the vehicle's power demands. Furthermore, the presence of the PTC heating system during warm-up cannot guarantee a consistent pressure difference between the air and water circuits, leading to bipolar plate damage and gas infiltration. Therefore, implementing effective control strategies to extend the lifespan of fuel cells is crucial during actual operation.

[0004] Current technologies typically employ a room-temperature start-up warm-up approach for fuel cell systems. This involves using the stack to generate heat to warm the small circulating water circuit to a suitable operating temperature, then gradually releasing the heat to the large circulating circuit, bypassing the PTC heating system before applying power. A cold-start warm-up approach involves using the PTC heating system to heat the small circulating water circuit to a suitable operating temperature, then gradually releasing the heat to the large circulating water circuit, bypassing the PTC heating system before applying power. Because of the presence of the PTC heating system, there is significant flow resistance in the small circulating water circuit. Therefore, current technology uses temperature to limit the power load, setting different maximum power capacities based on different stack temperatures. This results in low-power operation during stack warm-up, slow warm-up speed, and long cold-start times. Consequently, the system cannot keep up with the vehicle's power demand, requiring the vehicle to wait excessively for the system to respond, weakening performance. Furthermore, the pressure difference between the air and water circuits cannot be maintained during warm-up, causing damage to the bipolar plates and gas infiltration, leading to hydrogen embrittlement and breakage of water circuit components.

[0005] To address the aforementioned issues, this invention proposes a control method that, by controlling the pressure difference between the water circuit and the air circuit, during the warm-up or cold start phase, controls the maximum load-bearing power of the current system to continuously and rapidly warm up the engine using the maximum pressure difference between the water circuit and the air circuit. Simultaneously, the water pump speed is autonomously adjusted based on the temperature difference between the inlet and outlet of the fuel cell stack, ensuring the fuel cell stack operates within a reasonable temperature range. This continues until the water circuit switches to a large-circulation water circuit, and the flow resistance of the PTC heater is no longer affected. At this point, the pressure difference between the water circuit and the air circuit, as well as the system power limitations, are released, allowing for full-power response to the vehicle's demands. Summary of the Invention

[0006] Currently, hydrogen fuel cell systems primarily rely on PTC heating systems to heat the water circuit and raise the temperature of the fuel cell stack for cold start-up at low temperatures. However, due to the very high flow resistance of existing PTC heating systems, the addition of a PTC heating system creates a significant flow resistance component during the hot-start or cold-start phases when the water circuit is in a small circulation state. This prevents the fuel cell stack from carrying a large power load during the hot-start phase. If the water circuit is in a small circulation state during the hot-start or cold-start phases, the pressure in the air and hydrogen circuits within the fuel cell stack will be much higher than the pressure in the cooling water circuit. According to Darcy's law, the constitutive equation for liquid flow through porous media shows that the greater the pressure difference, the more gas will leak into the water circuit cavity. Due to the high permeability of hydrogen, the pipes, joints, and components within the water circuit may not be resistant to hydrogen embrittlement, leading to failure. Alternatively, if the pressure difference exceeds 100 kPa for an extended period, there is a risk of electrode plate rupture, resulting in fuel cell stack failure. There is also the possibility that when the flow resistance increases, the water pump pressure is insufficient, which leads to a gradual increase in temperature difference, exceeding the normal operating temperature of the membrane electrode assembly (MEA) of the fuel cell stack, accelerating the service life of the MEA, and causing fuel cell stack failure.

[0007] The technical solution of this invention is as follows.

[0008] A control method for a stable and rapid heat engine in a fuel cell system is disclosed. A three-way valve is positioned between the radiator, the PTC heater, and the fuel cell stack. By controlling the opening of the three-way valve, the switching between the large and small circulation water circuits is achieved. Temperature and pressure sensors are installed at the inlet and outlet of the fuel cell stack. Both temperature and pressure sensors are electrically connected to the controller. The controller receives signals, calculates them, and outputs analog signals to control the opening of the three-way valve, as well as the numerical logic calculations of temperature and pressure differences.

[0009] Preferably, the fuel cell water circuit subsystem consists of an expansion tank, a fuel cell water pump, a liquid flow meter, a radiator, a radiator outlet temperature sensor, a PTC heater, a three-way valve, a particulate filter, and a fuel cell stack, forming a water circuit circulation system. The fuel cell stack, fuel cell water pump, liquid flow meter, radiator, three-way valve, and particulate filter are connected in sequence. The particulate filter is also connected to the cooling water inlet of the fuel cell stack. The fuel cell water pump is also connected to the PTC heater, and the PTC heater is connected to the three-way valve. The exhaust outlet of the radiator is connected to the expansion tank, the water inlet of the expansion tank is connected to the water pump, and the exhaust outlet of the expansion tank is connected to the cooling water outlet of the fuel cell stack.

[0010] Preferably, a cooling water outlet temperature sensor is provided at the outlet of the fuel cell stack.

[0011] Preferably, the inlet of the fuel cell stack is equipped with a fuel cell inlet water temperature sensor and a fuel cell inlet water pressure sensor.

[0012] Preferably, an air pressure sensor is provided at the air inlet of the fuel cell stack.

[0013] Preferably, the small circulating water path in this invention is: from the cooling water outlet of the fuel cell stack to the fuel cell water pump to the PTC heater to the three-way valve to the particulate filter to the cooling water inlet of the fuel cell stack. Specifically, it is: from the cooling water outlet of the fuel cell stack to the outlet temperature sensor to the fuel cell water pump to the PTC heater to the three-way valve to the particulate filter to the inlet temperature sensor to the inlet water pressure sensor to the cooling water inlet of the fuel cell stack.

[0014] Preferably, the large circulating water path in this invention is as follows: from the cooling water outlet of the fuel cell stack to the fuel cell water pump to the liquid flow meter to the radiator to the three-way valve to the particulate filter to the cooling water inlet of the fuel cell stack, wherein the radiator and the expansion tank perform water replenishment and venting circulation. Specifically, from the cooling water outlet of the fuel cell stack to the outlet temperature sensor to the fuel cell water pump to the liquid flow meter to the radiator to the radiator outlet temperature sensor to the three-way valve to the particulate filter to the inlet temperature sensor to the inlet water pressure sensor to the cooling water inlet of the fuel cell stack, wherein the radiator and the expansion tank perform water replenishment and venting circulation.

[0015] A control method for a stable and rapid heat engine in a fuel cell system includes the following steps: (1) Under normal temperature start or cold start, start the fuel cell system. After the start is completed, the fuel cell maintains the set minimum idle power and receives the required power P´1 from the vehicle at any time and starts to respond to the demand. (2) At this time, the fuel cell system program sets the target air path stack inlet pressure (corresponding to the pressure measured by the inlet air pressure sensor 13) P1 - water path stack inlet pressure (corresponding to the pressure measured by the inlet water pressure sensor 10) P2≥(60~67)Kpa, the water path stack inlet temperature is (corresponding to the temperature measured by the inlet water temperature sensor 9) W1, the outlet temperature is (corresponding to the temperature measured by the outlet water temperature sensor 11) W2, and the water temperature difference between the outlet and inlet is set to W2-W1≤(11~14)℃; (3) The fuel cell system starts to respond to the vehicle's required power P´1, and simultaneously loads the target power P´1 at a rate of (30~50) A / s until the pressure difference between the air path stack inlet and the water path stack inlet is greater than or equal to (60~67) Kpa, that is, when P1-P2≥(60~67) Kpa, the power P´2 at which it remains is the first heat engine power; if it is loaded to the vehicle's required power P´1, and at the same time P1-P2<(60~67) Kpa, the vehicle's required power P´1 is maintained at the output. (4) If the temperature difference between the fuel cell outlet and the fuel cell inlet is less than or equal to (11~14)℃, i.e. W2-W1≤(11~14)℃, keep the current heat engine power P´2 unchanged or the vehicle demand power P´1 unchanged. (5) If the temperature difference between the fuel cell stack outlet and the fuel cell stack inlet is greater than (11~14)℃, i.e. W2-W1 > (11~14)℃, then increase the fuel cell water pump speed R1. (6) If increasing the pump speed does not satisfy the condition that the air circuit fuel cell inlet pressure P1 - water circuit fuel cell inlet pressure P2 ≥ (60~67) Kpa, then continue to respond to the vehicle power demand P´1 or maintain the current first heat engine power P´2; if P1-P2 ≥ (60~67) Kpa, the power that remains is the second heat engine power P´3. After time T1, if W2-W1 ≤ (11~14)℃ still does not satisfy the condition, then repeat step (5) until the temperature difference between the fuel cell outlet and the fuel cell inlet W2-W1 ≤ (11~14)℃ is satisfied, and maintain the current heat engine power unchanged. (7) As the temperature of the fuel cell stack rises, the opening of the three-way valve will gradually switch from the small circulation water circuit to the large circulation water circuit, which will bypass the small circulation water circuit where the PTC heating system is located. As a result, the flow resistance of the water circuit will drop sharply, and the pressure at the fuel cell stack inlet will rise. If the pressure difference between the air fuel cell stack inlet pressure and the fuel cell stack inlet pressure P1-P2 is not satisfied (60~67) Kpa, the vehicle power demand P´1 will be directly and completely responded to.

[0016] In the above method, T1 is 10 seconds.

[0017] In the above method, R1 is 500-800 rpm.

[0018] Compared with the prior art, the advantages of the present invention are: (1) The operation phase control method of the present invention will reduce the excessive pressure difference between the air path and the water path and at the same time ensure that the temperature difference between the inlet and outlet of the water path is too large, thereby avoiding the rupture of the bipolar plate of the stack and gas penetration caused by the pressure difference, and also avoiding the impact on the performance and life of the membrane electrode due to the excessive temperature difference.

[0019] (2) The present invention can identify the state of the fuel cell system during the start-up and operation phase, and determine whether it deviates from the operating environment, causing damage to the components.

[0020] (3) The present invention enables the system to generate maximum heat engine power under safe and reliable conditions, thereby achieving rapid heat engine operation. Attached Figure Description

[0021] Figure 1 This is a flowchart of the fuel cell stable and rapid heat engine control method of the present invention; Figure 2 This is a schematic diagram of the water circuit subsystem of a fuel cell system. Figure 3 This is a load data diagram for Example 2 of the rapid heat-up method; Figure 4 This is a load data diagram for Example 3 of the rapid heat-up method; Figure 5 This is a load data diagram for Example 4 of the rapid warm-up method. Detailed Implementation

[0022] The technical solutions described below, in conjunction with specific illustrations, are presented to provide a full understanding of this application. However, this application can be implemented in many other ways different from those described herein, and similar extended embodiments made by those skilled in the art without inventive effort are all within the scope of protection of this invention. Example 1

[0023] like Figure 2 As shown, in this embodiment, the fuel cell water circuit subsystem consists of an expansion tank 1, a fuel cell water pump 2, a liquid flow meter 3, a radiator 4, a radiator outlet temperature sensor 5, a PTC heater 6, a three-way valve 7, a particulate filter 8, and a fuel cell stack 12, forming a water circuit circulation system. The fuel cell stack 12, fuel cell water pump 2, liquid flow meter 3, radiator 4, three-way valve 7, and particulate filter 8 are connected in sequence. The particulate filter 8 is also connected to the cooling water inlet of the fuel cell stack 12. The fuel cell water pump 2 is also connected to the PTC heater 6, and the PTC heater 6 is connected to the three-way valve 7. The exhaust outlet of the radiator 4 is connected to the expansion tank 1, the water supply outlet of the expansion tank 1 is connected to the water pump, and the exhaust inlet of the expansion tank 1 is connected to the fuel cell stack 12.

[0024] In this embodiment, the reactor outlet water temperature sensor 11, reactor inlet water temperature sensor 9, reactor inlet water pressure sensor 10, and reactor inlet air pressure sensor 13 are all sensors.

[0025] A cooling water outlet temperature sensor 11 is installed at the outlet of the fuel cell stack 12.

[0026] The fuel cell stack 12 is equipped with a fuel cell temperature sensor 9 and a fuel cell pressure sensor 10 at the cooling water inlet.

[0027] An air pressure sensor 13 is installed at the air inlet of the fuel cell stack 12.

[0028] In this embodiment, the small circulation is set as follows: from the cooling water outlet of the fuel cell stack 12 to the outlet temperature sensor 11 to the fuel cell water pump 2 to the PTC heater 6 to the three-way valve 7 to the particulate filter 8 to the inlet temperature sensor 9 to the inlet water pressure sensor 10 to the cooling water inlet of the fuel cell stack 12.

[0029] The main circulation is set as follows: from the cooling water outlet of the fuel cell stack 12 to the outlet temperature sensor 11 to the fuel cell water pump 2 to the liquid flow meter 3 to the radiator 4 to the radiator outlet temperature sensor 5 to the three-way valve 7 to the particulate filter 8 to the inlet temperature sensor 9 to the inlet water pressure sensor 10 to the cooling water inlet of the fuel cell stack 12, wherein the radiator 4 and the expansion tank 1 perform water replenishment and exhaust circulation. Example 2

[0030] Introduce hydrogen and air, check system status, and wait for the vehicle's load power request; Upon receiving a vehicle power request of 50kW, and setting the load current rate to 30A / s, the fuel cell system initiates load testing. During the load-pushing process, when the fuel cell system is loaded to 40kW, it is determined that the air path stack inlet pressure P1 - water path stack inlet pressure P2 ≥ 60Kpa. According to the preset program, the load-pushing is stopped, and the current first heat engine power request of 40kW is maintained. After 10 seconds, it is still determined that the three-way valve is in the small circulation water circuit. At this time, the temperature difference between the fuel cell outlet W2 and the fuel cell inlet W1 is greater than 11℃. After the speed of the fuel cell water pump is increased by 500 revolutions, the pressure at the air path stack inlet P1 and the pressure at the water path stack inlet P2 are ≥60 kPa and the temperature difference between the stack outlet W2 and the stack inlet W1 is ≤11℃, maintaining the current first heat engine power of 40 kW. At this point, the temperature difference is continuously checked to see if it is greater than 11℃. The system continues until the three-way valve is fully opened to the main circulation water circuit, at which point it responds to the vehicle's power requirement of 50kW. Example 3

[0031] 1. Introduce hydrogen and air, check the system status, and wait for the vehicle's load power request; 2. Upon receiving a vehicle power request of 35kW, and setting the load current rate to 40A / s, the fuel cell system initiates load testing. 3. When the fuel cell system is loaded to 35kW, if the pressure at the air circuit stack inlet P1 - the pressure at the water circuit stack inlet P2 are ≤60Kpa, the current vehicle power request is maintained at 35kW. 4. After 10 seconds, the temperature difference between the fuel cell outlet W2 and the fuel cell inlet W1 is determined to be greater than 11℃. 5. After the speed of the fuel cell water pump is increased by 500 revolutions, the pressure at the air circuit stack inlet P1 - the pressure at the water circuit stack inlet P2 is ≤60 kPa, and the current vehicle power request remains at 35 kW. 6. At this point, after the three-way valve is fully opened to the main circulation water circuit, the system continuously responds to the vehicle's power demand of 35kW or even higher power requests. Example 4

[0032] 1. Introduce hydrogen and air, check the system status, and wait for the vehicle's load power request; 2. Upon receiving a vehicle power request of 80kW, and setting the load current rate to 40A / s, the fuel cell system initiates load testing. 3. During the load-bearing process, when the fuel cell system is loaded to 40kW, if the pressure at the air circuit stack inlet P1 - the pressure at the water circuit stack inlet P2 are determined to be ≥60Kpa, the load-bearing process will stop according to the preset program, and the current first heat engine power request of 40kW will be maintained. 4. If the three-way valve is still in the small circulation water circuit after 10 seconds, the temperature difference between the fuel cell outlet W2 and the fuel cell inlet W1 is greater than 11℃. 5. After the speed of the fuel cell water pump increases by 500 revolutions, the pressure at the air circuit stack inlet P1 - the pressure at the water circuit stack inlet P2 will be greater than or equal to 60 kPa, maintaining the current first heat engine power of 40 kW. 6. If the three-way valve is still in the small circulation water circuit after 10 seconds, the temperature difference between the fuel cell outlet W2 and the fuel cell inlet W1 is still greater than 11℃. 7. After the speed of the fuel cell water pump continues to increase by 500 revolutions, at this time, the pressure at the air circuit stack inlet P1 - the pressure at the water circuit stack inlet P2 ≤ 60 kPa, and it continues to respond to the vehicle power demand of 80 kW until the pressure at the air circuit stack inlet P1 - the pressure at the water circuit stack inlet P2 ≥ 60 kPa; at this time, according to the preset program, the load is stopped, and the current second heat engine power demand of 50 kW is maintained. 8. At this point, after the three-way valve is fully opened to the main circulation water circuit, the system continuously responds to the vehicle's power demand of 80kW or even higher.

Claims

1. A control method for a stable and rapid heat engine in a fuel cell system, characterized in that, The three-way valve (7) is located between the radiator (4), the PTC heater (6) and the fuel cell stack (12). By controlling the opening of the three-way valve (7), the large circulation water circuit and the small circulation water circuit can be switched. Temperature sensors and pressure sensors are installed at the inlet and outlet of the fuel cell stack (12). Both temperature sensors and pressure sensors are electrically connected to the controller. The controller receives signals and calculates them, and outputs analog signals to control the opening of the three-way valve, as well as the numerical logic calculation of temperature difference and pressure difference. Includes the following steps: (1) Under normal temperature start or cold start, start the fuel cell system. After the start is completed, the fuel cell maintains the set minimum idle power and receives the required power P´1 from the vehicle at any time and starts to respond to the demand. (2) At this time, the target air path stack inlet pressure P1 - water path stack inlet pressure P2 is set to ≥ 60 kPa, the water path stack inlet temperature is W1, the outlet temperature is W2, and the temperature difference between the outlet and inlet is set to W2 - W1 ≤ 11℃. (3) The fuel cell system starts to respond to the vehicle's required power P´1, and simultaneously loads the target power P´1 at a rate of (30~50) A / s until the pressure difference between the air path stack inlet and the water path stack inlet is greater than or equal to 60 kPa, that is, when P1-P2≥60 kPa; the power P´2 at which it remains is the first heat engine power; if it is loaded to the vehicle's required power P´1, and at the same time P1-P2<60 kPa, the vehicle's required power P´1 is maintained. (4) If the temperature difference between the fuel cell outlet and the fuel cell inlet is less than or equal to 11℃, i.e. W2-W1≤11℃, keep the current heat engine power P´2 unchanged or the vehicle demand power P´1 unchanged. (5) If the temperature difference between the fuel cell stack outlet and the fuel cell stack inlet is greater than 11℃, i.e. W2-W1 > 11℃, then increase the fuel cell water pump speed R1. (6) If increasing the pump speed does not satisfy the requirement that the air circuit fuel cell inlet pressure P1 - water circuit fuel cell inlet pressure P2 ≥ 60 kPa, then continue to respond to the vehicle power demand for load loading; if P1 - P2 ≥ 60 kPa, the power that remains is the second heat engine power P´3. After time T1, if W2 - W1 ≤ 11℃ is still not satisfied, then repeat step (5) until the temperature difference between the fuel cell outlet and the fuel cell inlet W2 - W1 ≤ 11℃ is satisfied, and keep the current heat engine power unchanged. (7) As the temperature of the fuel cell stack rises, the opening of the three-way valve will gradually switch from the small circulation water circuit to the large circulation water circuit, which will bypass the small circulation water circuit where the PTC heating system is located. As a result, the flow resistance of the water circuit will drop sharply, and the pressure at the fuel cell stack inlet will rise. If the pressure difference between the air fuel cell stack inlet pressure and the fuel cell stack inlet pressure P1-P2 is not satisfied with 60 kPa, the vehicle power demand P´1 will be directly and completely responded to. The small circulating water path is as follows: from the cooling water outlet of the stack (12) to the outlet temperature sensor (11) to the fuel cell water pump (2) to the PTC heater (6) to the three-way valve (7) to the particulate filter (8) to the inlet temperature sensor (9) to the inlet water pressure sensor (10) to the cooling water inlet of the stack (12); The large circulating water circuit is as follows: the cooling water outlet of the fuel cell stack (12) to the outlet temperature sensor (11) to the fuel cell water pump (2) to the liquid flow meter (3) to the radiator (4) to the radiator outlet temperature sensor (5) to the three-way valve (7) to the particulate filter (8) to the inlet temperature sensor (9) to the inlet water pressure sensor (10) to the cooling water inlet of the fuel cell stack 12, wherein the radiator (4) and the expansion tank (1) perform water replenishment and exhaust circulation.

2. The control method for a stable and rapid heat engine of a fuel cell system according to claim 1, characterized in that, The fuel cell water circuit subsystem consists of an expansion tank (1), a fuel cell water pump (2), a liquid flow meter (3), a radiator (4), a radiator outlet temperature sensor (5), a PTC heater (6), a three-way valve (7), a particulate filter (8), and a fuel cell stack (12) forming a water circuit circulation. The fuel cell stack (12), fuel cell water pump (2), liquid flow meter (3), radiator (4), three-way valve (7), and particulate filter (8) are connected in sequence. The particulate filter (8) is also connected to the cooling water inlet of the fuel cell stack (12). The fuel cell water pump (2) is also connected to the PTC heater (6), and the PTC heater (6) is connected to the three-way valve (7). The exhaust outlet of the radiator (4) is connected to the expansion tank (1), the water inlet of the expansion tank (1) is connected to the water pump, and the exhaust outlet of the expansion tank (1) is connected to the cooling water outlet of the fuel cell stack (12).

3. The control method for a stable and rapid heat engine of a fuel cell system according to claim 2, characterized in that, An air pressure sensor (13) is installed at the air inlet of the fuel cell stack (12).

4. The control method for a stable and rapid heat engine of a fuel cell system according to claim 1, characterized in that, T1 is 10 seconds; R1 is 500-800 rpm.

5. The control method for a stable and rapid heat engine of a fuel cell system according to claim 1, characterized in that, In step (2), the target air path stack inlet pressure is measured by the inlet air pressure sensor (13); the water path stack inlet pressure is measured by the inlet water path pressure sensor (10); the water path stack inlet temperature is measured by the inlet water path temperature sensor (9); and the outlet temperature is measured by the outlet water path temperature sensor (11).

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