A fuel cell system stack enclosure control method

Abstract

The present application relates to fuel cell system control technical field, disclose a kind of fuel cell system stack closed control method, comprising the following steps: after stack purging, the target flow into stack and target pressure into stack of the stack to be controlled are obtained;Determine valve opening control instruction according to the target flow into stack and target pressure into stack;Wherein, valve opening is used to control the air flow into stack;According to the valve opening control instruction, the closed control of the stack to be controlled is realized, the control method in the application consumes the oxygen of cathode in stack by improving the cathode pressure inside stack, so that the pressure difference of cathode and anode of stack reduces, is favorable to cathode sealing performance and prolongs the life of membrane material;And by filling more hydrogen into anode, the possibility of hydrogen-air interface is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cell system control, and more particularly to a fuel cell system stack sealing control method. BACKGROUND

[0002] There are two ways for the cathode structure of the fuel cell system stack at present: one is that the stack inlet cutoff valve and the stack bypass valve adopt a three-way valve; the other is that the electric inlet cutoff valve and the stack bypass valve each adopt an independent valve. When the system is electrically sealed, the stack inlet cutoff valve is usually closed and the stack bypass valve is opened, and there is no joint control between the two valves.

[0003] In the prior art, when the stack is sealed, oxygen consumption and hydrogen preservation are performed on the stack, specifically: by drawing the stack current, the cathode oxygen is consumed, and the anode is continuously supplied with hydrogen, so that the anode pressure remains constant. Since the cathode pressure is atmospheric pressure before the stack is sealed, after the oxygen is consumed, the cathode will present negative pressure, resulting in a large hydrogen-air pressure difference. The proton exchange membrane is subjected to a large pressure difference for a long time, reducing the service life of the proton exchange membrane. The atmospheric pressure is greater than the cathode pressure of the stack, which will result in poor sealing effect of the cathode of the stack, and oxygen is more likely to enter the cathode, thereby causing the hydrogen-oxygen interface of the stack to be reduced, reducing the service life of the stack.

[0004] However, the prior art has the following disadvantages:

[0005] 1. After the stack is sealed, the cathode of the stack presents negative pressure when oxygen consumption and hydrogen preservation are implemented, and the hydrogen-air pressure difference of the stack is large, which is not conducive to the service life of the stack;

[0006] 2. After the stack is sealed, the cathode pressure of the stack is less than the atmospheric pressure, which is not conducive to the sealing of the cathode of the stack, resulting in the entry of external air into the cathode, ultimately leading to the generation of a hydrogen-air interface, which is not conducive to the service life of the stack;

[0007] 3. After the stack is sealed, the cathode pressure of the stack can be higher than the atmospheric pressure, and the hydrogen pressure can be higher than that of the traditional method, which is more conducive to the long-term preservation of the stack and prolongs the time of the hydrogen-oxygen interface. SUMMARY

[0008] The purpose of the present application is to provide a fuel cell system stack sealing control method, which can raise the cathode pressure inside the stack, prolong the time of external oxygen entering the stack, and thus reduce the possibility of the hydrogen-oxygen interface.

[0009] To achieve the above purpose, the present application provides the following technical scheme:

[0010] A fuel cell system stack sealing control method, comprising the following steps:

[0011] After the stack purging is finished, a target stack inflow and a target stack pressure of a stack to be controlled are obtained;

[0012] A valve opening control instruction is determined according to the target stack inflow and the target stack pressure; wherein the valve opening is used to control the air inflow into the stack to be controlled;

[0013] The closed control of the stack to be controlled is realized according to the valve opening control instruction.

[0014] Further, the process of determining the valve opening control instruction according to the target stack inflow and the target stack pressure, and realizing the closed control of the stack to be controlled according to the valve opening control instruction specifically comprises:

[0015] After the stack purging is finished, the target stack inflow is first controlled to be 0, and the target stack pressure is adjusted to P off , then the stack back pressure valve is gradually closed, and under the pressure flow decoupling control algorithm of the air path, the air compressor speed, the stack outflow cutoff valve opening and the stack bypass valve opening are adjusted, so that the actual stack inflow is 0 and the actual stack pressure is P off , finally the stack inflow cutoff valve is closed, the stack closing is completed, and the oxygen consumption and hydrogen preservation are performed.

[0016] Further, the process of determining the valve opening control instruction according to the target stack inflow and the target stack pressure, and realizing the closed control of the stack to be controlled according to the valve opening control instruction specifically comprises:

[0017] After the stack purging is finished, the target stack inflow is first controlled to be 0, and the target stack pressure is adjusted to P off , then under the control of the pressure decoupling control algorithm of the air path, the air compressor speed, the stack outflow cutoff valve opening and the stack bypass valve opening are adjusted, so that the actual stack inflow is around 0 and the actual stack pressure is around P off , then the stack back pressure valve is closed, and finally the stack inflow cutoff valve is closed, the stack closing is completed, and the oxygen consumption and hydrogen preservation are performed.

[0018] Further, the system for executing the pressure flow decoupling control algorithm comprises a positive standard condition conversion module, a coordinate conversion module, a pressure flow decoupling module, an inverse standard condition conversion module and a controller module;

[0019] The positive standard condition conversion module is used to convert the parameters under non-standard working conditions into corresponding parameters under standard working conditions through the similarity theory;

[0020] The coordinate conversion module is used to convert the actual stack pressure and the actual stack inflow under standard working conditions into flow pressure ratio parameters for control;

[0021] The pressure flow decoupling module is configured to calculate the influence of the flow pressure ratio parameter on the actual stack inlet pressure and the actual stack inlet flow by a numerical method, and obtain a control strategy under a standard working condition.

[0022] The inverse standard condition conversion module is configured to convert the control strategy under the standard working condition into control parameters of the actual stack inlet flow and the actual stack inlet pressure under a non-standard working condition by similarity theory.

[0023] The controller module is configured to calculate errors between the actual stack inlet flow and the actual stack inlet pressure and target stack inlet flow and target stack inlet pressure respectively, and adjust the valve opening degree according to the errors.

[0024] Further, the parameters under the non-standard working condition include the valve opening degree, the stack inlet pressure and the stack inlet flow.

[0025] Further, the flow pressure ratio parameter includes an air compressor flow pressure ratio, an electric stack bypass valve flow pressure ratio and an electric stack back pressure valve flow pressure ratio.

[0026] Further, the calculation of the influence of the flow pressure ratio parameter on the actual stack inlet pressure and the actual stack inlet flow by the numerical method is specifically as follows:

[0027] The partial differentials of the actual stack inlet pressure and the actual stack inlet flow to the air compressor flow pressure ratio, the electric stack bypass valve flow pressure ratio and the electric stack back pressure valve flow pressure ratio are calculated by the numerical method.

[0028] Further, the calculation formula of the target stack inlet pressure is as follows:

[0029]

[0030] In the above formula, λ is the ratio of the pressure after oxygen consumption and hydrogen supplement to the atmospheric pressure; is the atmospheric pressure; α is the atmospheric oxygen volume fraction; is the air compressor surge pressure.

[0031] According to the specific embodiments of the present application, the following technical effects are provided:

[0032] In the fuel cell system stack closed control method, after the stack is closed, the pressure on the cathode side will rise. By implementing the oxygen consumption and hydrogen supplement operation, the oxygen in the cathode is completely consumed, and then the stack enters a shutdown storage state. With the passage of time, the gas in the cathode will gradually escape, so that the cathode pressure gradually decreases to balance with the atmospheric pressure. This process effectively prolongs the time interval for external oxygen to enter the inside of the stack, thereby significantly reducing the possibility of hydrogen and oxygen.

[0033] The application consumes oxygen of the cathode in the stack by increasing the pressure of the cathode inside the stack, so that the pressure difference between the anode and the cathode of the stack is reduced, and the sealing performance of the cathode is improved and the service life of the membrane material is prolonged. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only are the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on the provided drawings.

[0035] The fuel cell system stack sealing control method of the present application will be further described below in combination with the drawings.

[0036] Figure 1 The first control method for sealing the stack in the fuel cell system stack sealing control method provided by the present application;

[0037] Figure 2 The second control method for sealing the stack in the fuel cell system stack sealing control method provided by the present application;

[0038] Figure 3 The pressure change of the anode and the cathode before and after sealing the stack in the fuel cell system stack sealing control method provided by the present application; wherein Figure 3 The (a) in the above is a schematic diagram of the change of hydrogen and oxygen in the anode and the cathode after sealing the stack; a The (b) in the above is a schematic diagram of the pressure change of the anode and the cathode after sealing the stack; Figure 3

[0039] Figure 4 The first scheme of the fuel cell system architecture in the fuel cell system stack sealing control method provided by the present application;

[0040] Figure 5 The second scheme of the fuel cell system architecture in the fuel cell system stack sealing control method provided by the present application.

[0041] In the figure: 1, air filter; 2, air compressor; 3, intercooler; 4, humidifier; 5, stack inlet three-way valve; 6, stack; 7, stack Pack shell; 8, DCDC; 9, stack outlet stop valve; 10, stack bypass valve; 11, stack inlet stop valve; 12, pressure relief valve; 13, proportional valve; 14, ejector; 15, hydrogen circulating pump; 16, water vapor separator; 17, water and nitrogen discharge valve. DETAILED DESCRIPTION

[0042] ​The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the present application, but not to limit the scope of the present application.

[0043] In order to better understand the purpose, structure and function of the present application, the present application will be further described in detail below with reference to the accompanying drawings.

[0044] Due to the existing fuel cell system stack inlet cutoff valve 11 and stack bypass valve 10, a stack inlet three-way valve 5 is usually used. When the stack inlet three-way valve 5 is closed, the stack bypass valve 10 is opened; when the stack inlet three-way valve 5 is opened, the stack bypass valve 10 is closed, as shown in Figure 4 When the closed stack is performed, the stack inlet three-way valve 5 is closed, and the stack bypass valve 10 is naturally opened, resulting in that the stack cathode pressure can only be equal to the atmospheric pressure after the stack inlet three-way valve 5 is closed.

[0045] Alternatively, the fuel cell system stack inlet cutoff valve 11 and the stack bypass valve 10 are as shown in Figure 5 When two independent cutoff valves are used, in order to make the stack cathode pressure greater than the atmospheric pressure after the electrically operated stack inlet cutoff valve 11 is closed, special control is required to achieve it.

[0046] The fuel cell system performs the closed stack, which is mainly divided into four stages, as shown in Figure 3 The closed stack is divided into stack purging, closed stack, oxygen consumption and hydrogen supplement, and shutdown storage. After the stack is completed purging, the stack needs to be closed. The conventional method is to directly close the stack cathode inlet and outlet cutoff valve, but this will cause the cathode pressure to be equal to the atmospheric pressure. The control method of the present application will make the cathode pressure rise after the closed stack. Through the oxygen consumption and hydrogen supplement function, the oxygen in the cathode is consumed, and then enters the shutdown storage. The cathode gas will gradually escape, which will cause the cathode pressure to be equal to the atmospheric pressure, and prolong the time of external oxygen entering the stack, thereby reducing the possibility of the appearance of the hydrogen-oxygen interface.

[0047] In order to solve the problem of negative pressure of the stack cathode pressure after the stack oxygen consumption and hydrogen supplement, the present application is based on the system architecture scheme as shown in Figure 5 When the closed stack is performed, the necessary coordinated control is performed on the stack back pressure valve, the stack inlet cutoff valve 11, the stack bypass valve 10, and the air compressor 2; wherein, Figure 5The pressure relief valve 12 is mainly used to control the pressure in the fuel cell system to prevent damage caused by excessive pressure; the proportional valve 13 controls the flow rate of hydrogen or air, thereby adjusting the working state of the fuel cell stack; the ejector 14 recovers hydrogen from the exhaust gas, thereby improving the utilization rate of hydrogen; the hydrogen circulation pump 15 transports hydrogen from the anode to the cathode and recovers hydrogen from the exhaust gas; the water vapor separator 16 processes the air or hydrogen to remove moisture and vapor; and the drain and nitrogen discharge valve 17 discharges moisture and nitrogen from the fuel cell stack to prevent moisture and nitrogen from corroding and damaging the fuel cell stack.

[0048] This invention proposes a method for closed control of fuel cell stacks in a fuel cell system. After the stack purging is completed, the target infeed flow rate and target infeed pressure of the fuel cell stack to be controlled are obtained.

[0049] The valve opening control command is determined based on the target infeed flow rate and the target infeed pressure; wherein, the valve opening is used to control the air flow rate entering the fuel cell stack;

[0050] The controllable fuel cell stack is closed according to the valve opening control command.

[0051] This application provides two embodiments of a specific control scheme:

[0052] In one embodiment, such as Figure 1 As shown, the process of determining the valve opening control command based on the target infeed flow rate and target infeed pressure, and then controlling the closed-loop operation of the fuel cell stack to be controlled according to the valve opening control command, specifically includes:

[0053] After the fuel cell stack purging is completed, first control the target feed flow rate to 0, and adjust the target feed pressure to... Then, the back pressure valve of the fuel cell stack is gradually closed, and under the pressure-flow decoupling control algorithm of the air circuit, the speed of air compressor 2, the opening of fuel cell stack outlet shut-off valve 9, and the opening of fuel cell stack bypass valve 10 are adjusted to make the actual feed flow rate 0 and the actual feed pressure P. off Finally, close the stack entry shut-off valve 11 to complete the stack sealing.

[0054] In another embodiment, such as Figure 2 As shown, the process of determining the valve opening control command based on the target infeed flow rate and target infeed pressure, and the process of controlling the closed-loop operation of the fuel cell stack to be controlled based on the valve opening control command, specifically includes:

[0055] After the fuel cell stack purging is completed, first control the target feed flow rate to 0, and adjust the target feed pressure to... Then, under the control of the air circuit pressure decoupling control algorithm, the speed of air compressor 2, the opening of fuel cell stack outlet shut-off valve 9, and the opening of fuel cell stack bypass valve 10 are adjusted to keep the actual feed flow rate near 0 and the actual feed pressure at [value missing]. Nearby, then close the stack back pressure valve, and finally close the stack inlet stack stop valve 11, complete the stack closure.

[0056] In the above embodiment, the system for executing the pressure flow decoupling control algorithm comprises a positive standard condition conversion module, a coordinate conversion module, a pressure flow decoupling module, an inverse standard condition conversion module, and a controller module.

[0057] The positive standard condition conversion module is configured to convert parameters under non-standard working conditions to corresponding parameters under standard working conditions by similarity theory.

[0058] The coordinate conversion module is configured to convert the actual stack inlet pressure and the actual stack inlet flow under standard working conditions into flow pressure ratio parameters for control.

[0059] The pressure flow decoupling module is configured to calculate the influence of the flow pressure ratio parameters on the actual stack inlet pressure and the actual stack inlet flow by a numerical method, to obtain a control strategy under standard working conditions.

[0060] The inverse standard condition conversion module is configured to convert the control strategy under standard working conditions to control parameters for the actual stack inlet flow and the actual stack inlet pressure under non-standard working conditions by similarity theory.

[0061] The controller module is configured to calculate errors between the actual stack inlet flow and the actual stack inlet pressure and target stack inlet flow and target stack inlet pressure, and adjust the control target according to the errors.

[0062] The flow pressure ratio parameters include an air compressor 2 flow pressure ratio, an electric stack bypass valve 10 flow pressure ratio, and an electric stack back pressure valve flow pressure ratio.

[0063] The calculation of the influence of the flow pressure ratio parameters on the actual stack inlet pressure and the actual stack inlet flow by the numerical method is specifically:

[0064] The partial derivatives of the actual stack inlet pressure and the actual stack inlet flow with respect to the air compressor 2 flow pressure ratio, the electric stack bypass valve 10 flow pressure ratio, and the electric back pressure valve pressure ratio are calculated by the numerical method.

[0065] The calculation formula of the adjusted target stack inlet pressure is:

[0066]

[0067] In the above formula, λ is the ratio of the pressure after oxygen consumption and hydrogen supplement to the atmospheric pressure; is the atmospheric pressure; α is the atmospheric oxygen volume fraction; is the air compressor surge pressure.

[0068] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A fuel cell system stack close control method characterized by, The method comprises the following steps: After the stack purging is completed, target stack inflow and target stack pressure of a stack to be controlled are obtained; A valve opening degree control instruction is determined according to the target stack inflow and the target stack pressure, wherein the valve opening degree is used to control the air inflow into the stack to be controlled; Closed control of the stack to be controlled is realized according to the valve opening degree control instruction; The process of determining the valve opening degree control instruction according to the target stack inflow and the target stack pressure and realizing the closed control of the stack to be controlled according to the valve opening degree control instruction specifically comprises: After the stack purging is finished, first control the target stack inflow to be 0, adjust the target stack pressure to be P off Then under the control of the air path pressure decoupling control algorithm, adjust the air compressor speed, the stack outflow cutoff valve opening and the stack bypass valve opening, so that the actual stack inflow is near 0 and the actual stack pressure is near P off Then close the stack back pressure valve, and finally close the stack inflow cutoff valve, complete the stack closing and carry out the oxygen consumption and hydrogen preservation; or After the stack purging is finished, first, control the target stack inflow to be 0, adjust the target stack pressure to be P off Then, gradually close the stack back pressure valve, and under the pressure flow decoupling control algorithm of the air path, adjust the air compressor speed, the stack outflow cutoff valve opening and the stack bypass valve opening, so that the actual stack inflow is 0 and the actual stack pressure is P off Finally, close the stack inflow cutoff valve, complete the stack closing, and perform oxygen consumption and hydrogen preservation; The calculation formula for adjusting the target stack pressure is: In the above formula, λ is the ratio of the pressure after oxygen consumption and hydrogen supplement to the atmospheric pressure; p a is the atmospheric pressure; α is the atmospheric oxygen volume fraction; p surge is the air pressure machine surge pressure.

2. The fuel cell system stack close control method according to claim 1, characterized by, The system for executing the pressure flow decoupling control algorithm comprises a positive standard condition conversion module, a coordinate conversion module, a pressure flow decoupling module, an inverse standard condition conversion module and a controller module. The positive standard condition conversion module is used to convert parameters under non-standard working conditions into corresponding parameters under standard working conditions through similarity theory. The coordinate conversion module is used to convert the actual stack pressure and the actual stack inflow under standard working conditions into flow pressure ratio parameters for control. The pressure flow decoupling module is used to calculate the influence of the flow pressure ratio parameters on the actual stack pressure and the actual stack inflow through a numerical method to obtain a control strategy under standard working conditions. The inverse standard condition conversion module is used to convert the control strategy under standard working conditions into control parameters for the actual stack inflow and the actual stack pressure under non-standard working conditions through similarity theory. The controller module is used to calculate errors between the actual stack inflow and the actual stack pressure and the target stack inflow and the target stack pressure, and adjust the valve opening degree according to the errors.

3. The fuel cell system stack close control method according to claim 2, characterized by, The parameters under non-standard working conditions include the valve opening degree, the stack pressure and the stack inflow.

4. The fuel cell system stack close control method according to claim 2, characterized by, The flow pressure ratio parameters include the air compressor flow pressure ratio, the stack bypass valve flow pressure ratio and the stack back pressure valve flow pressure ratio.

5. The fuel cell system stack close control method according to claim 2, characterized by, The calculation of the influence of the flow pressure ratio parameters on the actual stack pressure and the actual stack inflow through the numerical method specifically comprises: The partial differentials of the actual stack pressure and the actual stack inflow on the air compressor flow pressure ratio, the electric bypass valve flow pressure ratio and the electric back pressure valve pressure ratio are calculated through the numerical method.

Images