Method and device for controlling hydrogen concentration of stack shell in system startup and shutdown process

Abstract

The invention discloses a method and a device for controlling the hydrogen concentration of an electric pile shell in a system startup and shutdown process. The system comprises a galvanic pile shell, a gas input branch and a gas output branch, the gas input branch comprises an air compressor, a first outlet and a second outlet, and the gas output branch comprises a first inlet and a second inlet; a diverter valve is connected between the second outlet and the first inlet; the control method comprises the following steps: controlling the diverter valve to be opened at the initial stage of starting or shutdown of the system; detecting the hydrogen concentration in the galvanic pile shell, and judging whether the hydrogen concentration of the galvanic pile shell is greater than a set threshold value or not; and when the hydrogen concentration in the galvanic pile shell is greater than a set threshold value, controlling to reduce the opening degree of the diverter valve, and controlling to increase the rotating speed of the air compressor, so that the hydrogen concentration of the galvanic pile shell is less than the set threshold value during startup or shutdown. According to the embodiment of the invention, by controlling the opening of the diverter valve, adjusting the rotating speed of the air compressor and controlling the hydrogen concentration of the stack shell in the startup and shutdown process of the system to be within the safety value range, tail exhaust hydrogen backflow is effectively prevented.

Description

Technical Field

[0001] Embodiments of the present invention relate to the technical field of fuel cell systems, and more particularly to a method and device for controlling hydrogen concentration in a fuel cell stack casing during a system startup and shutdown process. Background Art

[0002] A fuel cell is a device that converts the chemical energy of a fuel directly into electrical energy. It only undergoes an electrochemical reaction, uses fuel and oxygen as raw materials, has no noise pollution, emits very little harmful gas, and can be recycled.

[0003] When the fuel cell system is turned on and off, hydrogen leaks from the stack and accumulates in the stack shell. The increased concentration of hydrogen in the shell poses a safety risk. In the prior art, the method of controlling the hydrogen concentration in the stack shell during the startup and shutdown of the fuel cell system to prevent excessive hydrogen concentration is relatively complicated and usually requires adding new components to the system. Summary of the invention

[0004] The present invention provides a method and device for controlling the hydrogen concentration in a stack shell during a system startup and shutdown process, so as to quickly reduce the hydrogen concentration in the stack shell to a safe value range during the startup and shutdown process without adding additional components, thereby improving safety.

[0005] In the first aspect, an embodiment of the present invention provides a method for controlling the hydrogen concentration of a stack shell during a system startup and shutdown process. The system includes: a stack shell, a gas input branch and a gas output branch. The gas input branch includes an air compressor, a first outlet and a second outlet. The gas output branch includes a first inlet and a second inlet. The first outlet is connected to the purge inlet of the stack shell, a diverter valve is connected between the second outlet and the first inlet, and the second inlet is connected to the purge outlet of the stack shell. The control method includes:

[0006] In the initial stage of system startup or shutdown, the diverter valve is controlled to open;

[0007] Detecting the hydrogen concentration in the stack shell and determining whether the hydrogen concentration in the stack shell is greater than a set threshold;

[0008] When the hydrogen concentration in the stack shell is greater than a set threshold, the diverter valve opening is controlled to decrease, and the air compressor speed is controlled to increase, so that the hydrogen concentration in the stack shell is less than the set threshold when the system is started or shut down. Optionally, in the initial stage of system startup or shutdown, the diverter valve is controlled to open, including:

[0009] In the initial stage of system startup or shutdown, the opening of the diverter valve is controlled to be 100%.

[0010] Optionally, the gas input branch includes a main pipeline, a first branch pipeline and a second branch pipeline, the air compressor is arranged in the main pipeline and between the inlet of the main pipeline and the first outlet; the first outlet is connected to the purge inlet through the first branch pipeline, the second outlet is connected to the first inlet through the second branch pipeline, and the diverter valve is arranged in the second branch pipeline;

[0011] When the hydrogen concentration in the stack shell is greater than a set threshold, the diverter valve opening is controlled to be reduced, and the air compressor speed is controlled to be increased, so that the hydrogen concentration in the stack shell is less than the set threshold when starting or shutting down, including:

[0012] When the hydrogen concentration in the stack shell is greater than a set threshold, the diverter valve opening is controlled to be reduced to a set opening and maintained for a set time;

[0013] According to the pressure after the air compressor and before the first outlet in the main line corresponding to the current diverter valve opening, the speed of the air compressor is controlled to be the set speed and maintained for the set time, so that at the current diverter valve opening, the flow rate after the air compressor and before the first outlet in the main line is greater than or equal to the flow rate after the air compressor and before the first outlet in the main line when the diverter valve opening is 100%.

[0014] Optionally, based on the pressure at the point after the air compressor and before the first outlet in the main line corresponding to the current diverter valve opening, the speed of the air compressor is controlled to be a set speed and maintained for a set time, so that at the current diverter valve opening, the flow rate at the point after the air compressor and before the first outlet in the main line is greater than or equal to the flow rate at the point after the air compressor and before the first outlet in the main line when the diverter valve opening is 100%, and then the process returns to the step of detecting the hydrogen concentration in the stack shell and determining whether the hydrogen concentration in the stack shell is greater than a set threshold.

[0015] Optionally, the gas input branch further includes an intercooler, and the intercooler is connected between the air compressor and the first outlet;

[0016] According to the pressure at the main line after the air compressor and before the first outlet corresponding to the current diverter valve opening, the speed of the air compressor is controlled to be the set speed and maintained for the set time, so that under the current diverter valve opening, the flow rate at the main line after the air compressor and before the first outlet is greater than or equal to the flow rate at the main line after the air compressor and before the first outlet when the diverter valve opening is 100%, including:

[0017] Determine the pressure at the outlet of the intercooler at the current opening of the diverter valve according to the relationship table between the opening of the diverter valve and the pressure and flow at the outlet of the intercooler;

[0018] The set speed is determined according to the corresponding relationship between the pressure at the outlet of the intercooler, the target flow at the outlet of the intercooler and the speed of the air compressor;

[0019] The target flow rate is greater than or equal to the flow rate at the outlet of the intercooler when the diverter valve opening is 100%.

[0020] Optionally, before determining the set speed according to the corresponding relationship between the pressure at the outlet of the intercooler, the target flow at the outlet of the intercooler, and the speed of the air compressor, the method includes:

[0021] The corresponding relationship between the pressure at the outlet of the intercooler, the target flow at the outlet of the intercooler and the speed of the air compressor is obtained according to the air compressor operation diagram and the flow pressure loss curve of the intercooler;

[0022] The air compressor operation diagram is a relationship diagram between the air intake flow rate and the pressure ratio of the air compressor.

[0023] Optionally, the system further includes a first stop valve and a second stop valve, the first stop valve is connected between the third outlet of the main pipeline and the anode inlet of the fuel cell stack, the third outlet is located after the second outlet, and the second stop valve is connected between the first inlet and the anode outlet of the fuel cell stack;

[0024] In the initial stage of system startup or shutdown, before or while controlling the diverter valve to open, it also includes:

[0025] In the initial stage of system startup or shutdown, the first stop valve and the second stop valve are controlled to be cut off.

[0026] Optionally, when the hydrogen concentration in the stack housing is greater than a set threshold, controlling to reduce the opening of the diverter valve includes:

[0027] When the hydrogen concentration in the stack shell is greater than the set threshold, the diverter valve opening is controlled to decrease, the pressure after the air compressor and before the first outlet in the main line is increased, and the pressure after the air compressor and before the first outlet in the main line is less than the maximum pressure allowed by the purge inlet.

[0028] Optionally, after detecting the hydrogen concentration in the stack shell and determining whether the hydrogen concentration in the stack shell is greater than a set threshold, the method further includes:

[0029] When the hydrogen concentration in the stack shell is less than or equal to the set threshold, the opening of the diverter valve is controlled to 100%, and the speed of the air compressor is controlled so that the flow rate in the main line after the air compressor and before the first outlet is the same as the flow rate in the main line after the air compressor and before the first outlet in the initial stage of startup or shutdown.

[0030] In a second aspect, an embodiment of the present invention further provides a device for controlling hydrogen concentration in a stack shell during a system power-on / power-off process, wherein the system comprises: a stack shell, a gas input branch and a gas output branch, the gas input branch comprises an air compressor, a first outlet and a second outlet, and the gas output branch comprises a first inlet and a second inlet; the first outlet is connected to a purge inlet of the stack shell, a diverter valve is connected between the second outlet and the first inlet, and the second inlet is connected to the purge outlet of the stack shell;

[0031] The control device includes:

[0032] A first control module is used to control the diverter valve to open at the initial stage of system startup or shutdown;

[0033] A judgment module is used to detect the hydrogen concentration in the battery stack shell and judge whether the hydrogen concentration in the battery stack shell is greater than a set threshold;

[0034] The second control module is used to control the reduction of the diverter valve opening and the increase of the air compressor speed when the hydrogen concentration in the stack shell is greater than the set threshold, so that the hydrogen concentration in the stack shell is less than the set threshold when starting or shutting down.

[0035] The method and device for controlling the hydrogen concentration of the stack shell during the system startup and shutdown process of the embodiment of the present invention detects whether the hydrogen concentration in the stack shell is greater than the set threshold value after the diverter valve is opened in the initial stage of system startup or shutdown. If it is greater than the set threshold value, the diverter valve opening is controlled to be reduced, so that the pressure after the air compressor and before the first outlet in the main line increases; while reducing the opening of the diverter valve, the speed of the air compressor is increased, so that the air flow output from the main line remains unchanged or increases, and because the opening of the diverter valve is reduced, the flow through the branch where the diverter valve is located is reduced, and then the air flow entering the stack shell is increased compared with before the diverter valve opening is reduced, thereby accelerating the dilution of the hydrogen concentration in the stack shell, controlling the hydrogen concentration of the stack shell in the system startup and shutdown process within the safe value range, and effectively preventing the tail exhaust hydrogen from flowing back. In addition, the technical solution of the embodiment of the present invention does not need to increase the hardware structure of the system, and the method process for reducing the hydrogen concentration is simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic structural diagram of a fuel cell system provided in Embodiment 1 of the present invention.

[0037] Figure 2 This is a flow chart of a method for controlling the hydrogen concentration in a stack shell during a system startup and shutdown process provided in Embodiment 1 of the present invention.

[0038] Figure 3 A specific flow chart of a method for controlling the hydrogen concentration in a stack shell during a system startup and shutdown process provided in Embodiment 2 of the present invention.

[0039] Figure 4 A schematic diagram of a device for controlling the hydrogen concentration in a stack shell during a system startup and shutdown process provided in a third embodiment of the present invention.

[0040] Figure 1 In the middle: 11, fuel cell stack shell; 12, gas input branch; 13, gas output branch; 14, air compressor; 15, diverter valve; 16, intercooler; 17, first stop valve; 18, second stop valve; L, main line; L1, first branch line; L2, second branch line; A1, first outlet; A2, second outlet; A3, third outlet; B1, first inlet; B2, second inlet; C1, purge inlet; C2, purge outlet; D1, anode inlet of fuel cell stack; D2, anode outlet of fuel cell stack. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0042] Embodiment 1

[0043] Figure 1 A schematic diagram of the structure of a fuel cell system provided in Embodiment 1 of the present invention, Figure 2 This is a flow chart of a method for controlling the hydrogen concentration in a stack shell during a system startup and shutdown process provided in Embodiment 1 of the present invention. This embodiment can be applied to controlling the hydrogen concentration in a stack shell during a system startup and shutdown process.

[0044] like Figure 1 As shown, the fuel cell system includes: a stack shell 11, a gas input branch 12 and a gas output branch 13, the gas input branch 12 includes an air compressor 14, a first outlet A1 and a second outlet A2, the gas output branch 13 includes a first inlet B1 and a second inlet B2; the first outlet A1 is connected to the purge inlet C1 of the stack shell 11, a diverter valve 15 is connected between the second outlet A2 and the first inlet B1, and the second inlet B2 is connected to the purge outlet C2 of the stack shell 11.

[0045] In this embodiment, the stack shell 11 is an external structure for wrapping and protecting the fuel cell stack. The air compressor 14 is a machine that compresses air to increase gas pressure or transport gas. The diverter valve 15 is a device that changes the position of the valve core relative to the valve body under a certain pressure and load to ensure that the fluid is diverted in a certain proportion within a certain period of time. The inlet of the gas input branch 12 is connected to the outside atmosphere, the first outlet A1 of the gas input branch 12 is connected to the purge inlet C1 of the stack shell 11, and the second outlet A2 is connected to the first inlet B1 of the gas output branch 13, and a diverter valve 15 is connected in the middle, and the second inlet B2 of the gas output branch 13 is connected to the purge outlet C2 of the stack shell 11. Figure 1 In the fuel cell system shown, the flow divider valve 15 is connected between the second outlet A2 of the gas input branch 12 and the first inlet B1 of the gas output branch 13 .

[0046] like Figure 2 As shown, the control method includes:

[0047] S210: In the initial stage of system startup or shutdown, the diverter valve is controlled to open.

[0048] The initial stage of power-on can be understood as the set time from the power-on moment, and the initial stage of power-off can be understood as the set time from the power-off moment. For example, the set time can be 0.5s, 1s, etc., which is not specifically limited in this embodiment.

[0049] Optionally, at the initial stage of system startup or shutdown, the diverter valve is controlled to open, including:

[0050] In the initial stage of system startup or shutdown, the opening of the diverter valve is controlled to be 100%.

[0051] The fact that the opening degree of the diverter valve 15 is 100% can be understood as the diverter valve 15 being in a fully open state.

[0052] It should be noted that in other optional embodiments of the present invention, in the initial stage of system startup or shutdown, controlling the diverter valve 15 to open can be controlling the diverter valve 15 to a larger opening other than 100%, such as 95%, which is not specifically limited in this embodiment.

[0053] S220, detecting the hydrogen concentration in the fuel cell stack shell, and determining whether the hydrogen concentration in the fuel cell stack shell is greater than a set threshold.

[0054] A hydrogen concentration sensor may be provided in the stack housing 11 to detect the hydrogen concentration in the stack housing 11. The threshold value may be pre-stored. For example, the threshold value may be the maximum hydrogen concentration allowed in the stack housing 11. Exemplarily, the hydrogen concentration threshold value is set to 50% volume concentration.

[0055] S230: When the hydrogen concentration in the stack shell is greater than a set threshold, the diverter valve opening is controlled to decrease, and the air compressor speed is controlled to increase, so that the hydrogen concentration in the stack shell is less than the set threshold when starting or shutting down.

[0056] Optionally, when the hydrogen concentration in the stack shell 11 is greater than a set threshold, the opening of the diverter valve 15 is controlled to be reduced, and the speed of the air compressor 14 is controlled to be increased, so that the hydrogen concentration in the stack shell 11 is less than the set threshold when starting or shutting down, including: when the hydrogen concentration in the stack shell 11 is greater than the set threshold, the opening of the diverter valve 15 is controlled to be reduced, and the pressure after the air compressor 14 and before the first outlet A1 in the main line L is increased, and the pressure after the air compressor 14 and before the first outlet A1 in the main line L is less than the maximum pressure allowed by the purge inlet C1.

[0057] Exemplarily, the maximum pressure allowed at the purge inlet C1 is 250 kPaA. When the hydrogen concentration in the stack shell 11 is greater than the set threshold, the opening of the diverter valve 15 is controlled to decrease, and the pressure after the air compressor 14 and before the first outlet A1 in the main line L is increased, and the pressure after the air compressor 14 and before the first outlet A1 in the main line L is less than 250 kPaA.

[0058] Among them, the opening degree of the diverter valve 15 affects the pressure after the air compressor 14 and before the first outlet A1 in the main line L. The smaller the opening degree of the diverter valve 15, the greater the pressure after the air compressor 14 and before the first outlet A1 in the main line L. Therefore, by reducing the opening degree of the diverter valve 15, the pressure difference between the main line L after the air compressor 14 and before the first outlet A1 and the purge outlet C2 of the stack shell 11 can be increased. When the speed of the air compressor 14 remains unchanged, the increase in pressure after the air compressor 14 and before the first outlet A1 in the main line L will reduce the air flow output from the main line L in the gas input branch 12. Therefore, in this embodiment, the speed of the air compressor 14 is increased while reducing the opening of the diverter valve 15, so that the air flow output from the main line L remains unchanged or increases. Since the opening of the diverter valve 15 is reduced, the flow through the branch where the diverter valve 15 is located is reduced, and then the air flow entering the stack shell 11 is increased compared with before the opening of the diverter valve 15 is reduced, thereby accelerating the dilution of the hydrogen concentration in the stack shell 11.

[0059] Optionally, after step 220, the method further includes:

[0060] When the hydrogen concentration in the stack shell 11 is less than or equal to the set threshold, the opening of the diverter valve 15 is controlled to be 100%, and the speed of the air compressor 14 is controlled so that the flow rate in the main line L after the air compressor and before the first outlet A1 is the same as the flow rate in the main line L after the air compressor and before the first outlet A1 in the initial stage of startup or shutdown.

[0061] The technical solution of this embodiment is to detect whether the hydrogen concentration in the battery stack shell is greater than the set threshold value after the diverter valve is opened in the initial stage of system startup or shutdown. If it is greater than the set threshold value, the diverter valve opening is controlled to be reduced, so that the pressure after the air compressor and before the first outlet in the main line increases; while reducing the diverter valve opening, the speed of the air compressor is increased, so that the air flow output from the main line remains unchanged or increases, and because the diverter valve opening is reduced, the flow through the branch where the diverter valve is located is reduced, and then the air flow entering the battery stack shell is increased compared with before the diverter valve opening is reduced, thereby accelerating the dilution of the hydrogen concentration in the battery stack shell, controlling the hydrogen concentration of the battery stack shell in the process of system startup and shutdown within the safe value range, and effectively preventing the backflow of tail exhaust hydrogen. In addition, the technical solution of the embodiment of the present invention does not need to increase the hardware structure of the system, and the method of reducing the hydrogen concentration is simple and easy to implement.

[0062] Embodiment 2

[0063] Figure 3 1 is a specific flow chart of a method for controlling the hydrogen concentration of a stack shell during a system startup and shutdown process provided in Embodiment 2 of the present invention. The gas input branch 12 includes a main line L, a first branch line L1, and a second branch line L2. The air compressor 14 is arranged on the main line L and between the inlet of the main line L and the first outlet A1. The first outlet A1 is connected to the purge inlet C1 through the first branch line L1, and the second outlet A2 is connected to the first inlet B1 through the second branch line L2. The diverter valve 15 is arranged on the second branch line L2. Figure 3 The method for controlling the hydrogen concentration of the stack shell during the power-on and power-off process of the system includes:

[0064] S310, in the initial stage of system startup or shutdown, control the diverter valve to open; this step is the same as the S210 process in the above embodiment, and will not be repeated here.

[0065] S320, detecting the hydrogen concentration in the stack shell, and determining whether the hydrogen concentration in the stack shell is greater than a set threshold; this step is the same as the S220 process in the above embodiment, and will not be repeated here.

[0066] S330: When the hydrogen concentration in the stack shell is greater than a set threshold, control the diverter valve opening to be reduced to a set opening and maintain it for a set time.

[0067] The set time can be pre-stored. For example, the set threshold is set to 50% volume concentration, the set opening is set to 50%, and the set time is set to 30s. When the hydrogen concentration in the stack shell is greater than the set 50% volume concentration, the opening of the diverter valve is reduced to 50% and maintained for 30s.

[0068] S340. According to the pressure after the air compressor and before the first outlet in the main line corresponding to the current diverter valve opening, control the speed of the air compressor to a set speed and maintain it for a set time, so that at the current diverter valve opening, the flow rate after the air compressor and before the first outlet in the main line is greater than or equal to the flow rate after the air compressor and before the first outlet in the main line when the diverter valve opening is 100%.

[0069] Among them, after the opening of the diverter valve 15 is reduced to the current opening, if it is necessary to ensure that the flow rate after the air compressor 14 and before the first outlet A1 in the main line L is greater than or equal to the flow rate after the air compressor 14 and before the first outlet A1 in the main line L when the diverter valve 15 is opened 100%, it is necessary to increase the speed of the air compressor 14. The speed is set to ensure that under the current opening of the diverter valve 15, the flow rate after the air compressor 14 and before the first outlet A1 in the main line L is greater than or equal to the flow rate after the air compressor 14 and before the first outlet A1 in the main line L when the diverter valve 15 is opened 100%.

[0070] Optional, such as Figure 3 As shown, after S340, the process returns to execute S320.

[0071] Continue to refer Figure 1 Optionally, the gas input branch 12 further includes an intercooler 16, and the intercooler 16 is connected between the air compressor 14 and the first outlet A1;

[0072] The above step 340 includes:

[0073] According to the relationship table between the opening of the diverter valve 15 and the pressure-flow rate at the outlet of the intercooler 16 , the pressure at the outlet of the intercooler 16 under the current opening of the diverter valve 15 is determined;

[0074] The set speed is determined according to the corresponding relationship between the pressure at the outlet of the intercooler 16, the target flow at the outlet of the intercooler 16 and the speed of the air compressor 14;

[0075] The target flow rate is greater than or equal to the flow rate at the outlet of the intercooler 16 when the opening degree of the diverter valve 15 is 100%.

[0076] In this embodiment, the intercooler 16 is a device for reducing the temperature of high-temperature air after supercharging. The pressure-flow relationship table of the intercooler 16 is a relationship table between the opening of the diverter valve 15 and the pressure and flow at the outlet of the intercooler 16 under the condition that the speed of the air compressor 14 remains unchanged. The pressure at the outlet of the intercooler 16 under the current opening of the diverter valve 15 is determined by the pressure-flow relationship table between the opening of the diverter valve 15 and the intercooler 16. The set speed is obtained by the corresponding relationship between the pressure at the outlet of the intercooler 16, the target flow at the outlet of the intercooler 16 and the speed of the air compressor 14. When the pressure at the outlet of the intercooler 16 and the target flow at the outlet of the intercooler 16 are constant, a uniquely determined speed of the air compressor 14 can be obtained.

[0077] Optionally, before determining the set speed according to the corresponding relationship between the pressure at the outlet of the intercooler 16, the target flow at the outlet of the intercooler 16, and the speed of the air compressor 14, the method includes:

[0078] The corresponding relationship between the pressure at the outlet of the intercooler 16, the target flow at the outlet of the intercooler 16 and the speed of the air compressor 14 is obtained according to the operation diagram of the air compressor 14 and the flow pressure loss curve of the intercooler 16;

[0079] The operation diagram of the air compressor 14 is a relationship diagram between the intake air flow rate and the pressure ratio of the air compressor 14 .

[0080] In this embodiment, the flow pressure loss curve can be understood as a technical indicator curve of the flow consumption of the device. The corresponding relationship between the pressure at the outlet of the intercooler 16, the target flow at the outlet of the intercooler 16 and the speed of the air compressor 14 is obtained by calibrating the air compressor 14 operation diagram and the flow pressure loss curve of the intercooler 16.

[0081] Continue to refer Figure 1 Optionally, the system further includes a first stop valve 17 and a second stop valve 18, the first stop valve 17 is connected between the third outlet A3 of the main line L and the anode inlet D1 of the stack, the third outlet A3 is located after the second outlet A2, and the second stop valve 18 is connected between the first inlet B1 and the anode outlet D2 of the stack;

[0082] In the initial stage of system startup or shutdown, before or while controlling the diverter valve 15 to open, the following steps are also included:

[0083] In the initial stage of system startup or shutdown, the first stop valve 17 and the second stop valve 18 are controlled to be shut off.

[0084] In this embodiment, the stop valve is a tool that relies on the valve lever pressure to make the valve disc sealing surface fit tightly with the valve seat sealing surface to prevent the flow of medium. The first stop valve 17 is connected between the third outlet A3 of the main line L and the anode inlet D1 of the battery stack, and the third outlet A3 is located after the second outlet A2. The second stop valve 18 can be understood as a tool that is different from the first stop valve 17 and is used to prevent the flow of gas, and is connected between the first inlet B1 and the anode outlet D2 of the battery stack. In the initial stage of system startup or shutdown, the first stop valve 17 and the second stop valve 18 are controlled to be in the cut-off state to prevent the flow of gas.

[0085] Continue to refer Figure 1 The system also includes an air filter, a low-pressure flow sensor, a tail exhaust silencer, a back pressure valve and a humidifier. The low-pressure flow sensor is connected between the air compressor 14 and the air filter. The tail exhaust silencer is at the outlet of the gas output branch 13. The back pressure valve is connected between the humidifier and the diverter valve 15. The humidifier is connected between the first stop valve 17, the second stop valve 18 and the main line L and the back pressure valve.

[0086] An air filter is a device that removes dust and sand from the air and reduces the wear of cylinders, pistons and piston rings. A low-pressure flow sensor is a sensor used to detect pressure, flow, temperature and humidity. A tail exhaust muffler is a device used to reduce tail exhaust noise. A back pressure valve is a control valve that allows fluid to flow only along the water inlet, but the medium at the water outlet cannot flow back. A humidifier is an electronic instrument that uses various scientific methods, such as ultrasound, heating, etc., to turn water into small molecules to increase air humidity. During the startup and shutdown process of a fuel cell system, the back pressure valve and humidifier are in a closed state.

[0087] The principle of a method for controlling the hydrogen concentration in the stack shell during the system power on / off process is as follows: when the system is in the power on or power off state, the first stop valve 17 and the second stop valve 18 are controlled to be in the closed state, and the diverter valve 15 is at 100% opening. At this time, it is detected whether the hydrogen concentration in the stack shell 11 is greater than a set threshold value. If it is greater than the set threshold value, the opening of the diverter valve 15 is reduced, and the speed of the air compressor 14 is controlled and increased according to the opening of the diverter valve 15 and the pressure-flow relationship table at the outlet of the intercooler 16, so that the air flow rate remains consistent and runs for 30 seconds. At this time, it is detected again whether the hydrogen concentration in the stack shell 11 is greater than the set threshold value. If it is greater than the set threshold value, the above steps are repeated. If it is less than or equal to the set threshold value, the opening of the diverter valve 15 is set to 100%, and the speed of the air compressor 14 is reduced to keep the air flow consistent and run normally until the end.

[0088] The technical solution of this embodiment is to control the opening of the diverter valve in the initial stage of system startup or shutdown, and then detect whether the hydrogen concentration in the stack shell is greater than the set threshold value. If it is greater than the set threshold value, the diverter valve opening is controlled to be reduced, and the speed of the air compressor is controlled and increased according to the opening of the diverter valve and the pressure-flow relationship table of the intercooler outlet, so that the air flow rate remains consistent for the set operation time, so that the pressure after the air compressor and before the first outlet in the main line increases, thereby increasing the pressure difference between the main line after the air compressor and before the first outlet and the stack shell purge outlet; while reducing the opening of the diverter valve, the speed of the air compressor is increased, so that the air flow output from the main line remains unchanged or increases, and because the opening of the diverter valve is reduced, the flow through the branch where the diverter valve is located is reduced, and then the air flow entering the stack shell is increased compared with before the diverter valve opening is reduced, thereby accelerating the dilution of the hydrogen concentration in the stack shell, controlling the hydrogen concentration in the system startup and shutdown process to be within a safe value range, and effectively preventing the backflow of tail exhaust hydrogen. Furthermore, the technical solution of the embodiment of the present invention does not need to increase the hardware structure of the system, and the method process for reducing the hydrogen concentration is simple and easy to implement.

[0089] Embodiment 3

[0090] Figure 4 A schematic diagram of a stack shell hydrogen concentration control device for a system power-on / off process provided in Embodiment 3 of the present invention, the system includes: a stack shell 11, a gas input branch 12 and a gas output branch 13, the gas input branch 12 includes an air compressor 14, a first outlet A1 and a second outlet A2, the gas output branch 13 includes a first inlet B1 and a second inlet B2; the first outlet A1 is connected to the purge inlet C1 of the stack shell 11, a diverter valve 15 is connected between the second outlet A2 and the first inlet B1, and the second inlet B2 is connected to the purge outlet C2 of the stack shell 11. Figure 4 As shown, the control device includes:

[0091] The first control module 410 is used to control the diverter valve 15 to open in the initial stage of system startup or shutdown;

[0092] The judgment module 420 is used to detect the hydrogen concentration in the stack housing 11 and judge whether the hydrogen concentration in the stack housing 11 is greater than a set threshold;

[0093] The second control module 430 is used to control the reduction of the opening of the diverter valve 15 and the increase of the speed of the air compressor 14 when the hydrogen concentration in the stack shell 11 is greater than the set threshold, so that the hydrogen concentration in the stack shell 11 is less than the set threshold when starting or shutting down.

[0094] In this embodiment, the first control module 410 can be understood as a module that controls the working state of the diverter valve 15. In a system startup and shutdown process battery stack shell hydrogen concentration control device, the first control module 410 is used to control the diverter valve 15 to open in the initial stage of the system startup and shutdown. Exemplarily, the opening of the diverter valve 15 is controlled to be 100%. The judgment module 420 can be understood as a module in the system that determines whether the hydrogen flow rate exceeds a set threshold. In a system startup and shutdown process battery stack shell hydrogen concentration control device, the judgment module 420 is used to detect the hydrogen concentration in the battery stack shell 11, and determine whether the hydrogen concentration of the battery stack shell 11 is greater than the set threshold. The second control module 430 can be understood as a module that is different from the first control module 410 and controls the speed of the air compressor 14. The second control module 430 is used to control the reduction of the opening of the diverter valve 15 and the increase of the speed of the air compressor 14 when the hydrogen concentration in the stack shell 11 is greater than the set threshold, so that the hydrogen concentration in the stack shell 11 is less than the set threshold when starting or shutting down.

[0095] The device for controlling the hydrogen concentration in the stack shell during the system power-on and power-off process of this embodiment is used to execute the method for controlling the hydrogen concentration in the stack shell during the system power-on and power-off process of any of the above embodiments of the present invention, and has the beneficial effects of the method for controlling the hydrogen concentration in the stack shell during the system power-on and power-off process of any of the above embodiments of the present invention.

[0096] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for controlling hydrogen concentration in a stack shell during system startup and shutdown, characterized in that: The system comprises: a stack housing, a gas input branch and a gas output branch, wherein the gas input branch comprises an air compressor, a first outlet and a second outlet, and the gas output branch comprises a first inlet and a second inlet; the first outlet is connected to a purge inlet of the stack housing, a diverter valve is connected between the second outlet and the first inlet, and the second inlet is connected to the purge outlet of the stack housing; The control method comprises: In the initial stage of starting up or shutting down the system, controlling the diverter valve to open; Detecting the hydrogen concentration in the fuel cell stack shell, and determining whether the hydrogen concentration in the fuel cell stack shell is greater than a set threshold; When the hydrogen concentration in the stack shell is greater than a set threshold, the diverter valve opening is controlled to decrease, and the air compressor speed is controlled to increase, so that the hydrogen concentration in the stack shell is less than the set threshold when starting or shutting down.

2. The method for controlling hydrogen concentration in the stack shell during system startup and shutdown according to claim 1 is characterized in that: In the initial stage of starting up or shutting down the system, controlling the diverter valve to open includes: In the initial stage of starting up or shutting down the system, the opening degree of the diverter valve is controlled to be 100%.

3. The method for controlling hydrogen concentration in the stack shell during system startup and shutdown according to claim 2 is characterized in that: The gas input branch includes a main pipeline, a first branch pipeline and a second branch pipeline. The air compressor is arranged on the main pipeline and between the inlet of the main pipeline and the first outlet. The first outlet is connected to the purge inlet through the first branch pipeline, and the second outlet is connected to the first inlet through the second branch pipeline. The diverter valve is arranged on the second branch pipeline. When the hydrogen concentration in the stack shell is greater than a set threshold, the diverter valve opening is controlled to be reduced, and the air compressor speed is controlled to be increased, so that the hydrogen concentration in the stack shell is less than the set threshold when the stack is turned on or off, including: When the hydrogen concentration in the fuel cell stack housing is greater than a set threshold, controlling the diverter valve opening to be reduced to a set opening and maintaining the opening for a set time; According to the pressure at the point after the air compressor and before the first outlet in the main pipeline corresponding to the current diverter valve opening, the speed of the air compressor is controlled to be a set speed and maintained for the set time, so that at the current diverter valve opening, the flow rate at the point after the air compressor and before the first outlet in the main pipeline is greater than or equal to the flow rate at the point after the air compressor and before the first outlet in the main pipeline when the diverter valve opening is 100%.

4. The method for controlling hydrogen concentration in the stack casing during system startup and shutdown according to claim 3 is characterized in that: After controlling the speed of the air compressor to a set speed and maintaining it for a set time according to the pressure at the point after the air compressor and before the first outlet in the main line corresponding to the current diverter valve opening, so that under the current diverter valve opening, the flow rate at the point after the air compressor and before the first outlet in the main line is greater than or equal to the flow rate at the point after the air compressor and before the first outlet in the main line when the diverter valve opening is 100%, returning to the step of detecting the hydrogen concentration in the stack shell and determining whether the hydrogen concentration in the stack shell is greater than a set threshold.

5. The method for controlling hydrogen concentration in the stack casing during system startup and shutdown according to claim 3 is characterized in that: The gas input branch further includes an intercooler, and the intercooler is connected between the air compressor and the first outlet; According to the pressure at the main line after the air compressor and before the first outlet corresponding to the current diverter valve opening, the speed of the air compressor is controlled to be a set speed and maintained for a set time, so that under the current diverter valve opening, the flow rate at the main line after the air compressor and before the first outlet is greater than or equal to the flow rate at the main line after the air compressor and before the first outlet when the diverter valve opening is 100%, including: Determining the pressure at the outlet of the intercooler at the current opening of the diverter valve according to a relationship table between the opening of the diverter valve and the pressure-flow rate at the outlet of the intercooler; Determining the set speed according to the corresponding relationship between the pressure at the outlet of the intercooler, the target flow at the outlet of the intercooler and the speed of the air compressor; Wherein, the target flow rate is greater than or equal to the flow rate at the outlet of the intercooler when the diverter valve opening is 100%.

6. The method for controlling hydrogen concentration in the stack shell during system startup and shutdown according to claim 5 is characterized in that: Before determining the set speed according to the corresponding relationship between the pressure at the outlet of the intercooler, the target flow at the outlet of the intercooler and the speed of the air compressor, the method includes: The corresponding relationship between the pressure at the outlet of the intercooler, the target flow at the outlet of the intercooler and the speed of the air compressor is obtained according to the air compressor operation diagram and the intercooler flow pressure loss curve; The air compressor operation diagram is a relationship diagram between the air intake flow rate and the pressure ratio of the air compressor.

7. The method for controlling hydrogen concentration in the stack shell during system startup and shutdown according to claim 3 is characterized in that: The system further includes a first stop valve and a second stop valve, wherein the first stop valve is connected between a third outlet of the main line and an anode inlet of the stack, the third outlet is located after the second outlet, and the second stop valve is connected between the first inlet and the anode outlet of the stack; In the initial stage of starting up or shutting down the system, before or while controlling the diverter valve to open, the process further includes: In the initial stage of starting up or shutting down the system, the first stop valve and the second stop valve are controlled to be cut off.

8. The method for controlling hydrogen concentration in the stack casing during system startup and shutdown according to claim 3 is characterized in that: When the hydrogen concentration in the stack housing is greater than a set threshold, controlling to reduce the opening of the diverter valve includes: When the hydrogen concentration in the stack shell is greater than a set threshold, the diverter valve opening is controlled to decrease, the pressure in the main line after the air compressor and before the first outlet is increased, and the pressure in the main line after the air compressor and before the first outlet is less than the maximum pressure allowed by the purge inlet.

9. The method for controlling hydrogen concentration in the stack casing during system startup and shutdown according to claim 3 is characterized in that: After detecting the hydrogen concentration in the stack shell and determining whether the hydrogen concentration in the stack shell is greater than a set threshold, the method further includes: When the hydrogen concentration in the stack shell is less than or equal to a set threshold, the opening of the diverter valve is controlled to be 100%, and the speed of the air compressor is controlled so that the flow rate in the main line after the air compressor and before the first outlet is the same as the flow rate in the main line after the air compressor and before the first outlet in the initial stage of startup or shutdown.

10. A device for controlling hydrogen concentration in a stack shell during system startup and shutdown, characterized in that: The system comprises: a stack housing, a gas input branch and a gas output branch, wherein the gas input branch comprises an air compressor, a first outlet and a second outlet, and the gas output branch comprises a first inlet and a second inlet; the first outlet is connected to a purge inlet of the stack housing, a diverter valve is connected between the second outlet and the first inlet, and the second inlet is connected to the purge outlet of the stack housing; The control device comprises: A first control module, used for controlling the diverter valve to open at the initial stage of starting up or shutting down the system; A judgment module, used to detect the hydrogen concentration in the fuel cell stack shell and judge whether the hydrogen concentration in the fuel cell stack shell is greater than a set threshold; The second control module is used to control the reduction of the diverter valve opening and the increase of the air compressor speed when the hydrogen concentration in the stack shell is greater than a set threshold, so that the hydrogen concentration in the stack shell is less than the set threshold when starting or shutting down.

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