Hydrogen concentration estimation method and system for fuel cells

Abstract

The present application relates to a method and system for estimating hydrogen concentration for a fuel cell. A method for estimating hydrogen concentration for a fuel cell includes: measuring the air flow rate supplied to a fuel cell group and comparing the measured air flow rate with a predetermined flow rate; determining a model of an air treatment system according to the comparison result; and estimating the hydrogen concentration of a fuel treatment system based on the determined model of the air treatment system.

Description

Technical Field

[0001] The present disclosure generally relates to a hydrogen concentration estimation method and system for a fuel cell, and more particularly to a hydrogen concentration estimation method and system in which the hydrogen concentration is estimated by variably setting a model according to an air supply amount of a fuel cell stack. Background Art

[0002] As is well known in the art, a fuel cell is a device that converts the chemical energy of a fuel into electrical energy through an oxidation-reduction reaction of hydrogen and oxygen supplied from a hydrogen supply device and an air supply device, respectively, and includes a fuel cell stack for generating electricity, a cooling system for cooling the fuel cell stack, etc.

[0003] In other words, hydrogen is supplied to the anode of the fuel cell stack, and an oxidation reaction of oxidizing hydrogen occurs at the anode to generate hydrogen ions (protons) and electrons. At this time, the protons and electrons generated at the anode flow to the cathode through the electrolyte membrane and the separator, respectively. At the cathode, water is generated by an electrochemical reaction involving the protons and electrons flowing out of the anode and the oxygen contained in the air, and this electron flow generates electricity.

[0004] The hydrogen supplied to the anode of the fuel cell stack must be maintained at an appropriate concentration level in order to perform appropriate hydrogen gas exchange control in the hydrogen recirculation line. Typically, hydrogen gas exchange control is performed by estimating the hydrogen concentration in real time, thereby maintaining an appropriate hydrogen concentration level.

[0005] However, when the hydrogen concentration is estimated in real time in the fuel cell stop mode, there is a problem that the error between the estimated value of the hydrogen concentration and the measured value of the hydrogen concentration in the fuel processing system is large.

[0006] Figure 1 (Related Art) is a graph showing measured values ​​of hydrogen concentration and estimated values ​​of hydrogen concentration as a function of fuel cell current according to the related art.

[0007] refer to Figure 1 , in the fuel cell stop mode (FC stop mode) where the fuel cell current (output current of the fuel cell stack) is zero, the error between the measured value of the hydrogen concentration and the estimated value of the hydrogen concentration is large.

[0008] Specifically, in the fuel cell stop mode, the hydrogen concentration measurement value increases as the fuel cell stop mode continues. However, the hydrogen concentration measurement value in the fuel cell stop mode is not reliable because the hydrogen concentration does not increase.

[0009] As the fuel cell stop mode continues, the estimated hydrogen concentration decreases, even to about 20% to 30% hydrogen concentration. However, according to experiments, the actual hydrogen concentration measurement value remains at about 60% hydrogen concentration.

[0010] In other words, since a large error occurs between the measured value of hydrogen concentration and the estimated value of hydrogen concentration in the fuel cell stop mode, the estimated value is significantly lower than the actual hydrogen concentration, which leads to the problem of excessive hydrogen ventilation when the fuel cell stop mode is released. The execution of excessive hydrogen ventilation is not conducive to improving fuel mileage and meeting emission standards.

[0011] The above content is only for helping understanding the background of the present disclosure and is not intended to mean that the present disclosure falls within the scope of the relevant technology known to those skilled in the art. Summary of the invention

[0012] The present disclosure provides a hydrogen concentration estimation method and system for a fuel cell, wherein the hydrogen concentration in a fuel processing system is accurately estimated even in a fuel cell stop mode.

[0013] In order to achieve the above-mentioned purpose, according to one aspect of the present disclosure, a method for estimating hydrogen concentration for a fuel cell is provided, the method comprising: measuring an air flow rate supplied to a fuel cell stack, and comparing the measured air flow rate with a predetermined flow rate; determining a model of an air handling system according to the comparison result; and estimating the hydrogen concentration of a fuel handling system based on the determined model of the air handling system.

[0014] When comparing the measured air flow rate with the predetermined flow rate, the predetermined flow rate may be set as the air flow rate that occurs when the air supply to the fuel cell stack is cut off.

[0015] In determining the model of the air handling system, when the measured air flow rate exceeds a predetermined flow rate, the air handling system may be determined to be an open model.

[0016] In the case where the air handling system is determined to be an open model, the hydrogen partial pressure of the air handling system can be considered to be zero when estimating the hydrogen concentration of the fuel handling system.

[0017] In the case where the air handling system is determined to be an open model, when estimating the hydrogen concentration of the fuel handling system, the nitrogen partial pressure or the oxygen partial pressure of the air handling system may be obtained based on the gas pressure and the water vapor partial pressure of the air handling system.

[0018] When determining the model of the air handling system, when the measured air flow rate is equal to or less than a predetermined flow rate, the air handling system may be determined to be a closed model.

[0019] In the case where the air handling system is determined to be a closed model, when estimating the hydrogen concentration of the fuel handling system, the hydrogen partial pressure of the air handling system is increased due to the hydrogen permeating from the fuel handling system.

[0020] When estimating hydrogen concentration, the hydrogen partial pressure in the air handling system can be obtained using the following formula:

[0021]

[0022]

[0023] The number of moles of hydrogen in the air handling system, The initial number of moles of hydrogen in the air handling system, The number of moles of hydrogen permeated per unit time, Hydrogen partial pressure in air handling system, R: gas constant, T: gas temperature, V Ca : The volume inside the air handling system.

[0024] In the case where the air handling system is determined to be a closed model, when estimating the hydrogen concentration of the fuel handling system, the oxygen partial pressure of the air handling system is reduced due to the oxygen permeating into the fuel handling system.

[0025] When estimating the hydrogen concentration, the oxygen partial pressure in the air handling system can be obtained using the following formula:

[0026]

[0027] Oxygen partial pressure in the air handling system, Initial oxygen partial pressure in the air handling system, t: Duration of the closed model in the air handling system, T 1 : Time constant (constant).

[0028] In the case where the air handling system is determined to be a closed model, when estimating the hydrogen concentration of the fuel handling system, the nitrogen partial pressure of the air handling system is reduced due to the nitrogen permeating to the fuel handling system.

[0029] When estimating hydrogen concentration, the nitrogen partial pressure in the air handling system can be obtained using the following formula:

[0030]

[0031]

[0032] Nitrogen partial pressure in the air handling system, The number of moles of nitrogen in the air handling system, VCa : volume inside the air handling system, R: gas constant, T: gas temperature, n Ca : the number of moles of gas in the air handling system, The number of moles of hydrogen in the air handling system, The number of moles of oxygen in the air handling system, P Ca : Gas pressure in the air handling system.

[0033] When estimating the hydrogen concentration in a fuel handling system, the water vapor partial pressure in the air handling system or the fuel handling system can be considered the saturated water vapor pressure.

[0034] When estimating the hydrogen concentration of the fuel handling system, the nitrogen partial pressure of the fuel handling system is increased due to nitrogen permeation from the air handling system.

[0035] When estimating the hydrogen concentration of a fuel processing system, the hydrogen partial pressure of the fuel processing system is obtained by subtracting the nitrogen partial pressure and the water vapor partial pressure from the gas pressure of the fuel processing system.

[0036] When estimating the hydrogen concentration of the fuel processing system, the hydrogen partial pressure of the fuel processing system may be estimated by dividing the hydrogen partial pressure of the fuel processing system by the sum of the nitrogen partial pressure and the hydrogen partial pressure.

[0037] After estimating the hydrogen concentration of the fuel processing system, the fuel processing system may be controlled such that the estimated hydrogen concentration of the fuel processing system follows a target hydrogen concentration.

[0038] According to another aspect of the present disclosure, a hydrogen concentration estimation system for a fuel cell is provided, the system comprising: an air handling system that supplies air to a fuel cell stack; a fuel handling system that supplies hydrogen to the fuel cell stack; and a hydrogen concentration estimator that measures an air flow rate supplied from the air handling system to the fuel cell stack, compares the measured air flow rate with a predetermined flow rate, determines a model of the air handling system, and estimates the hydrogen concentration of the fuel handling system based on the determined model of the air handling system.

[0039] The hydrogen concentration estimator may determine that the air handling system is an open model when the measured air flow rate exceeds a predetermined flow rate, and may determine that the air handling system is a closed model when the measured air flow rate is equal to or less than the predetermined flow rate.

[0040] The system may further include: a pressure controller that controls the pressure of hydrogen supplied from the fuel storage system to the fuel processing system; a gas exchange controller that controls opening and closing of the gas exchange valve; and a main controller that controls the pressure controller and the gas exchange controller so that the hydrogen concentration of the fuel processing system estimated by the hydrogen concentration estimator follows the target hydrogen concentration.

[0041] According to the hydrogen concentration estimation method and system according to the present disclosure, the accuracy of the hydrogen concentration estimator can be improved even in the fuel cell stop mode.

[0042] Furthermore, when the fuel cell stop mode is released, excessive hydrogen gas replacement or excessive pressure control can be prevented.

[0043] Additionally, the amount of hydrogen that is unnecessarily consumed to increase hydrogen concentration in the fuel processing system may be reduced, which is beneficial in improving fuel mileage and meeting emission standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The above and other objects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description in conjunction with the accompanying drawings, in which:

[0045] Figure 1 (Related Art) is a graph showing a measured value of hydrogen concentration and an estimated value of hydrogen concentration as a function of a fuel cell current according to the related art;

[0046] Figure 2 is a flow chart showing a hydrogen concentration estimation method for a fuel cell according to an embodiment of the present disclosure;

[0047] Figure 3 is a configuration diagram showing a hydrogen concentration estimation system for a fuel cell according to an embodiment of the present disclosure; and

[0048] Figure 4 is a graph showing a hydrogen concentration measurement value and a hydrogen concentration estimation value as a function of a fuel cell current according to a hydrogen concentration estimation method for a fuel cell according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0049] It should be understood that the term "vehicle" or "vehicular" or other similar terms used herein generally include motor vehicles, such as passenger cars including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, marine vessels including various boats and ships, aircraft, etc., and include hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle having two or more power sources, for example, gasoline-powered and electric-powered vehicles.

[0050] The term used here is only for the purpose of describing a specific embodiment, rather than for limiting the present disclosure. As used in this article, unless clearly indicated in the context, the singular form "one", "a kind of" and "said" are intended to include the plural form as well. It will be further understood that when used in this specification, the words "include" and / or "comprise" specify the existence of the features, integers, steps, operations, elements and / or components, but do not exclude the existence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups. As used herein, the word "and / or" includes any and all combinations of one or more related listed items. Throughout the specification, unless clearly described to the contrary, the word "include" and the variants of, for example, "include" or "have" will be understood to imply the inclusion of the elements, but do not exclude any other elements. In addition, the terms "unit", "-device", "-part" and "module" described in the specification refer to the unit for processing at least one function and operation, and can be implemented by hardware components or software components and combinations thereof.

[0051] In addition, the control logic of the present disclosure may be embodied as a non-transitory computer-readable medium on a computer-readable medium containing executable program instructions executed by a processor, controller, etc. Examples of computer-readable media include, but are not limited to, ROM, RAM, compact disk (CD)-ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer-readable medium may also be distributed in a network-coupled computer system so that the computer-readable medium is stored and executed in a distributed manner, for example, by a telematics server or a controller area network (CAN).

[0052] The specific structure and function description of the embodiments of the present disclosure disclosed herein are only for the illustrative purpose of the embodiments of the present disclosure. Without departing from the spirit and important features of the present disclosure, the present disclosure can be embodied in many different forms. Therefore, the embodiments of the present disclosure are disclosed only for the purpose of illustration and should not be construed as limiting the present disclosure.

[0053] Reference will now be made in detail to various embodiments of the present disclosure, specific examples of which are shown in the accompanying drawings and described below, as the embodiments of the present disclosure may be variously modified in many different forms. Although the present disclosure will be described in conjunction with the exemplary embodiments, it will be understood that this description is not intended to limit the present disclosure to those exemplary embodiments. On the contrary, the present disclosure is intended to cover not only the exemplary embodiments, but also various alternatives, variations, equivalents and other embodiments that may be included within the spirit and scope of the present disclosure as defined by the appended claims.

[0054] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Throughout the accompanying drawings, the same reference numerals will refer to the same or similar parts.

[0055] Figure 2 is a flow chart illustrating a hydrogen concentration estimation method for a fuel cell according to an embodiment of the present disclosure.

[0056] refer to Figure 2 According to an embodiment of the present disclosure, a method for estimating hydrogen concentration for a fuel cell includes: measuring an air flow rate supplied to a fuel cell group, and comparing the measured air flow rate with a predetermined flow rate (S200); determining a model of an air handling system according to the comparison result (S300 and S400); and estimating a hydrogen concentration of a fuel handling system based on the determined model of the air handling system (S500).

[0057] The air flow rate supplied to the fuel cell stack may be measured using a sensor (S100). Alternatively, the air flow rate supplied to the fuel cell stack may be estimated in consideration of the rotation speed of the air compressor, the opening of the air control valve (ACV), the air pressure and temperature, etc. However, in this case, the air flow rate supplied to the fuel cell stack may be determined by using whether the air control valve is closed, because only whether air is supplied to the fuel cell stack may be used.

[0058] The measured air flow rate can be compared with a predetermined flow rate (S200). Here, the predetermined flow rate can be set to the air flow rate that occurs when the air supply to the fuel cell stack is cut off. When the air supply to the fuel cell stack is cut off due to the closure of the air control valve, the air flow rate reaches zero, so that the predetermined flow rate can be set to zero.

[0059] Alternatively, although the predetermined flow rate is theoretically zero, if the air control valve is installed at only one of the air inlet and outlet, some degree of diffusion may occur, and thus the air flow rate may be greater than zero. Therefore, it may be considered to set the predetermined flow rate according to the diffused air flow rate.

[0060] Generally, when estimating the hydrogen concentration, the fuel handling system is assumed to be closed, and the air handling system is assumed to be open. Assuming the air handling system to be an open model is reasonable because external air is introduced and exhausted to the outside when air is supplied to the fuel cell.

[0061] However, in the fuel cell stop mode, it can be assumed that the air handling system of the fuel cell is cut off from the outside and closed. Specifically, in the fuel cell stop mode, the air supply is cut off by the air cut-off valve. Even if only one of the air supply and the air exhaust is cut off, the diffusion distance is large, and the diffusion area is very small, so it is difficult for diffusion to occur. Therefore, it is reasonable to assume that the air handling system is a closed model when the air supply is cut off.

[0062] Therefore, in determining the model of the air handling system (S300 and S400), when the measured air flow rate exceeds the predetermined flow rate, the air handling system can be determined as an open model, and when the measured air flow rate is equal to or less than the predetermined flow rate, the air handling system can be determined as a closed model. Based on the model of the air handling system determined as an open or closed model, the hydrogen concentration of the fuel processing system can be estimated.

[0063] Specifically, in the case where the air handling system is determined to be an open model (S300), when estimating the hydrogen concentration of the fuel handling system, it is assumed that the hydrogen partial pressure of the air handling system is zero. This assumes that hydrogen is discharged to the outside through the air flow or consumed by reacting with oxygen contained in the air. It can be assumed that the water vapor partial pressure is the saturated water vapor pressure that varies as a function of temperature.

[0064] The nitrogen partial pressure or oxygen partial pressure of the air handling system may be obtained based on the gas pressure and water vapor partial pressure of the air handling system. Specifically, the value obtained by subtracting the water vapor partial pressure from the gas pressure in the air handling system may be the sum of the nitrogen partial pressure and the oxygen partial pressure of the air handling system. Assuming that air is composed of 79% nitrogen and 21% oxygen, the nitrogen partial pressure may be calculated as 0.79*(gas pressure of the air handling system - water vapor partial pressure), and the oxygen partial pressure may be calculated as 0.21*(gas pressure of the air handling system - water vapor partial pressure).

[0065] In determining the model of the air handling system ( S200 ), when the measured air flow rate is equal to or less than a predetermined flow rate, it may be determined that the air handling system is a closed model.

[0066] In the case where the air handling system is determined to be a closed model ( S400 ), when estimating the hydrogen concentration of the fuel handling system, it may be assumed that the hydrogen partial pressure of the air handling system increases due to hydrogen permeating from the fuel handling system.

[0067] Specifically, when estimating the hydrogen concentration (S500), the hydrogen partial pressure of the air handling system can be obtained using the following formula:

[0068]

[0069]

[0070] The number of moles of hydrogen in the air handling system, The initial number of moles of hydrogen in the air handling system, The number of moles of hydrogen permeated per unit time, Hydrogen partial pressure in air handling system, R: gas constant, T: gas temperature, V Ca: The volume inside the air handling system.

[0071] Here, the initial number of moles of hydrogen in the air handling system is It can be the measured or estimated number of moles of hydrogen in the air handling system before integrating the moles of hydrogen that permeates. In the presence of air flow, assuming that no hydrogen is present in the air handling system, the initial number of moles of hydrogen in the air handling system can be assumed to be is zero.

[0072] In the case where the air handling system is determined to be a closed model ( S400 ), when estimating the hydrogen concentration of the fuel handling system, it may be assumed that the oxygen partial pressure of the air handling system is reduced due to oxygen permeating into the fuel handling system.

[0073] Specifically, when estimating the hydrogen concentration (S500), the oxygen partial pressure of the air handling system can be assumed using the following formula:

[0074]

[0075] Oxygen partial pressure in the air handling system, Initial oxygen partial pressure in the air handling system, t: Duration of the closed model in the air handling system, T 1 : Time constant (constant).

[0076] Here, the initial oxygen partial pressure in the air handling system The last value calculated in the open model before switching to the closed model can be used. Time constant T 1 It can be set experimentally to be closest to the actual situation. According to the temperature of oxygen, the time constant T 1 Can have different values.

[0077] In the case where the air handling system is determined to be a closed model (S400), when estimating the hydrogen concentration of the fuel handling system (S500), it may be assumed that the nitrogen partial pressure of the air handling system is reduced due to the nitrogen permeating into the fuel handling system.

[0078] Specifically, when estimating the hydrogen concentration (S500), the nitrogen partial pressure of the air handling system can be assumed using the following formula:

[0079]

[0080]

[0081] Nitrogen partial pressure in the air handling system, The number of moles of nitrogen in the air handling system, V Ca: volume inside the air handling system, R: gas constant, T: gas temperature, n Ca : the number of moles of gas in the air handling system, The number of moles of hydrogen in the air handling system, The number of moles of oxygen in the air handling system, P Ca : Gas pressure in the air handling system.

[0082] When estimating the hydrogen concentration of the fuel processing system (S500), the water vapor partial pressure of the air processing system or the fuel processing system may be a saturated water vapor pressure that varies as a function of temperature.

[0083] The fuel processing system may be assumed to be a closed model (S500). The fuel processing system may be assumed to include only nitrogen, hydrogen, and water vapor. This assumes that when oxygen permeates the membrane to the fuel processing system, it reacts with the hydrogen and disappears. The water vapor partial pressure may be assumed to be the saturated water vapor pressure that varies as a function of temperature.

[0084] When estimating the hydrogen concentration of the fuel processing system (S500), it can be assumed that the nitrogen partial pressure of the fuel processing system increases due to the nitrogen permeating from the air processing system. It can be assumed that the hydrogen partial pressure of the fuel processing system is obtained by subtracting the nitrogen partial pressure and the water vapor partial pressure from the gas pressure of the fuel processing system.

[0085] Specifically, the nitrogen partial pressure can be assumed by the following formula:

[0086]

[0087]

[0088] Nitrogen partial pressure in the fuel handling system, Number of moles of nitrogen in the fuel handling system, V An : the volume inside the fuel handling system, The initial number of moles of nitrogen in the fuel handling system, The number of moles of nitrogen that permeates per unit time. Here, the initial number of moles of nitrogen in the fuel processing system This may be the calculated or measured number of moles of nitrogen in the fuel processing system prior to integration of the moles of nitrogen that permeates.

[0089] It can be assumed that the hydrogen partial pressure is obtained by subtracting the nitrogen partial pressure and the water vapor partial pressure from the fuel processing system gas pressure.

[0090] When estimating the hydrogen concentration of the fuel processing system (S500), the hydrogen partial pressure of the fuel processing system may be estimated by dividing the hydrogen partial pressure of the fuel processing system by the sum of the nitrogen partial pressure and the hydrogen partial pressure.

[0091] Hydrogen concentration = (hydrogen partial pressure / (nitrogen partial pressure+hydrogen partial pressure)).

[0092] After estimating the hydrogen concentration of the fuel processing system (S500), the fuel processing system may be controlled so that the estimated hydrogen concentration of the fuel processing system follows a target hydrogen concentration (S600).

[0093] The target hydrogen concentration may be stored in a target hydrogen concentration map stored in a memory. The target hydrogen concentration map may be obtained by mapping the optimal hydrogen concentration according to the output current of the fuel cell stack. When the hydrogen concentration is greater than the optimal hydrogen concentration, the amount of hydrogen that permeates increases, thereby reducing fuel mileage. When the hydrogen concentration is lower than the optimal hydrogen concentration, the durability of the fuel cell stack may deteriorate due to insufficient hydrogen, resulting in a shortened fuel cell stack life. The optimal hydrogen concentration may be mapped to a specific region with an upper limit and a lower limit.

[0094] The amount of gas that permeates can be calculated using the mass transfer formula. Specifically, the amount of gas exchange can be considered when the gas permeates the membrane or the gas exchange valve is opened.

[0095] The mass transfer formula can use techniques known in the art. For example, the amount of gas transmitted can be calculated using the following mass transfer formula:

[0096]

[0097]

[0098] Here, the symbols used in the formula are as follows:

[0099] Nitrogen permeability;

[0100] Hydrogen permeability;

[0101] P: pressure, [kPa];

[0102] R: gas constant, 8.314 [J / mol / K];

[0103] T: temperature, [K];

[0104] D: diffusion coefficient;

[0105] A: catalyst area; and

[0106] δ: diffusion distance.

[0107] Based on the estimated hydrogen concentration of the fuel processing system, the fuel processing system may be controlled such that the hydrogen concentration in the fuel processing system follows the target hydrogen concentration. Closed loop control such as PI control may be used to ensure robustness with respect to disturbances such as sudden starts or fuel cell stop modes.

[0108] Specifically, when the estimated hydrogen concentration is less than the target hydrogen concentration, the hydrogen concentration may be controlled to increase. The scavenging valve may be controlled to open to thereby increase the hydrogen concentration by scavenging, or the fuel supply valve and the fuel injector may be controlled to pressurize the hydrogen supplied from the fuel storage system to the fuel processing system.

[0109] Figure 3 is a diagram showing a configuration of a hydrogen concentration estimation system for a fuel cell according to an embodiment of the present disclosure.

[0110] refer to Figure 3 According to an embodiment of the present disclosure, a hydrogen concentration estimation system for a fuel cell includes: an air processing system 30 for supplying air to a fuel cell stack A; a fuel processing system 20 for supplying hydrogen to the fuel cell stack A; and a hydrogen concentration estimator 70 for measuring the air flow rate supplied from the air processing system 30 to the fuel cell stack A, comparing the measured air flow rate with a predetermined flow rate, determining a model of the air processing system 30, and estimating the hydrogen concentration of the fuel processing system 20 based on the determined model of the air processing system 30.

[0111] The air flow rate may be controlled by the opening degree of an air control valve 31 provided in an air supply or exhaust line of the air handling system 30. The air flow rate may be estimated by measuring the opening degree of the air control valve 31.

[0112] The hydrogen concentration estimator 70 may determine that the air handling system 30 is an open model when the measured air flow rate exceeds a predetermined flow rate, and may determine that the air handling system 30 is a closed model when the measured air flow rate is equal to or less than the predetermined flow rate.

[0113] The hydrogen concentration estimation system may further include: a pressure controller 50 for controlling the pressure of hydrogen supplied from the fuel storage system 10 to the fuel processing system 20; a ventilation controller 60 for controlling the opening and closing of the ventilation valve 61; and a main controller 40 for controlling the pressure controller 50 and the ventilation controller 60 so that the hydrogen concentration of the fuel processing system 20 estimated by the hydrogen concentration estimator 70 follows the target hydrogen concentration.

[0114] The pressure controller 50 controls the pressure of the hydrogen gas supplied from the fuel storage system 10 to the fuel processing system 20 by controlling the fuel supply valve 51 and the fuel injector 51 .

[0115] The main controller 40, the pressure controller 50, the ventilation controller 60, and the hydrogen concentration estimator 70 may all be included in a fuel cell control unit (FCU), or may be provided as separate controllers.

[0116] Figure 4 is a graph showing a hydrogen concentration measurement value and a hydrogen concentration estimation value as a function of a fuel cell current according to a hydrogen concentration estimation method for a fuel cell according to an embodiment of the present disclosure.

[0117] refer to Figure 4 , the hydrogen concentration estimation value according to the hydrogen concentration estimation method of the present disclosure corresponds closely to the hydrogen concentration measurement value, especially in the fuel cell power generation stage. In addition, the stage where the fuel cell current is zero is unreliable because the hydrogen concentration measurement value is quite large in the FC STOP stage where the fuel cell power generation is stopped. However, the hydrogen concentration estimation value is maintained at a hydrogen concentration equal to or greater than 50%. In addition, it can be seen that the hydrogen concentration estimation value converges to the hydrogen concentration measurement value shortly after the FC STOP stage is released.

[0118] Therefore, according to the embodiment of the present disclosure, according to the hydrogen concentration estimation method for a fuel cell, it can be confirmed that the accuracy of hydrogen concentration estimation is improved.

[0119] Although preferred embodiments of the present disclosure have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the disclosure as disclosed in the accompanying claims.

Claims

1. A method for estimating hydrogen concentration in a fuel cell, the method comprising: The following steps are involved: measuring an air flow rate supplied to the fuel cell stack and comparing the measured air flow rate with a predetermined flow rate, wherein the predetermined flow rate is set as the air flow rate that occurs when the air supply to the fuel cell stack is cut off; determining a model of the air handling system according to the comparison result, wherein when the measured air flow rate exceeds the predetermined flow rate, the air handling system is determined to be an open model, and when the measured air flow rate is equal to or less than the predetermined flow rate, the air handling system is determined to be a closed model; and A hydrogen concentration of the fuel processing system is estimated based on the determined model of the air processing system.

2. The method according to claim 1, in, In the case where the air handling system is determined to be the open model, the hydrogen partial pressure of the air handling system is regarded as zero when estimating the hydrogen concentration of the fuel handling system.

3. The method according to claim 1, in, In the case where the air processing system is determined to be the open model, when estimating the hydrogen concentration of the fuel processing system, the nitrogen partial pressure or the oxygen partial pressure of the air processing system is obtained based on the gas pressure and the water vapor partial pressure of the air processing system.

4. The method according to claim 1, in, In the case where the air processing system is determined to be the closed model, when estimating the hydrogen concentration of the fuel processing system, the hydrogen partial pressure of the air processing system is increased due to hydrogen permeating from the fuel processing system.

5. The method according to claim 4, in, When estimating the hydrogen concentration, use the following formula to obtain the hydrogen partial pressure of the air handling system: The number of moles of hydrogen in the air handling system, The initial number of moles of hydrogen in the air treatment system, The number of moles of hydrogen permeated per unit time, The hydrogen partial pressure of the air handling system, R: gas constant, T: gas temperature, V Ca : The volume inside the air handling system.

6. The method according to claim 1, in, In the case where the air handling system is determined to be the closed model, when estimating the hydrogen concentration of the fuel handling system, the oxygen partial pressure of the air handling system is reduced due to the oxygen permeating into the fuel handling system.

7. The method according to claim 6, in, When estimating the hydrogen concentration, use the following formula to obtain the oxygen partial pressure of the air handling system: The oxygen partial pressure of the air handling system, Initial oxygen partial pressure of the air handling system, t: Duration of the closed model of the air handling system, T 1 : Time constant, constant.

8. The method according to claim 1, in, In the case where the air handling system is determined to be the closed model, when estimating the hydrogen concentration of the fuel handling system, the nitrogen partial pressure of the air handling system is reduced due to the nitrogen permeating into the fuel handling system.

9. The method according to claim 6, in, When estimating the hydrogen concentration, use the following formula to obtain the nitrogen partial pressure of the air handling system: The nitrogen partial pressure of the air handling system, The number of moles of nitrogen in the air handling system, V Ca : volume inside the air handling system, R: gas constant, T: gas temperature, n Ca : the number of moles of gas in the air handling system, The number of moles of hydrogen in the air handling system, The number of moles of oxygen in the air handling system, P Ca : Gas pressure in the air handling system.

10. The method according to claim 1, in, When estimating the hydrogen concentration of the fuel processing system, the water vapor partial pressure of the air processing system or the fuel processing system is considered to be the saturated water vapor pressure.

11. The method according to claim 1, in, When estimating the hydrogen concentration of the fuel processing system, the nitrogen partial pressure of the fuel processing system is increased due to nitrogen permeating from the air processing system.

12. The method according to claim 1, in, When estimating the hydrogen concentration of the fuel processing system, the hydrogen partial pressure of the fuel processing system is obtained by subtracting the nitrogen partial pressure and the water vapor partial pressure from the gas pressure of the fuel processing system.

13. The method according to claim 1, in, When estimating the hydrogen concentration of the fuel processing system, the hydrogen partial pressure of the fuel processing system is estimated by dividing the hydrogen partial pressure of the fuel processing system by the sum of the nitrogen partial pressure and the hydrogen partial pressure.

14. The method according to claim 1, in, After estimating the hydrogen concentration of the fuel processing system, the fuel processing system is controlled so that the estimated hydrogen concentration of the fuel processing system follows a target hydrogen concentration.

15. A hydrogen concentration estimation system for a fuel cell, the system include: an air handling system to supply air to the fuel cell stack; a fuel processing system to supply hydrogen to the fuel cell stack; as well as Hydrogen concentration estimator, measuring the air flow rate supplied from the air handling system to the fuel cell stack, and comparing the measured air flow rate with a predetermined flow rate, wherein the predetermined flow rate is set as the air flow rate that occurs when the air supply to the fuel cell stack is cut off, determining a model of the air handling system, wherein the hydrogen concentration estimator determines that the air handling system is an open model when the measured air flow rate exceeds the predetermined flow rate, and determines that the air handling system is a closed model when the measured air flow rate is equal to or less than the predetermined flow rate, and A hydrogen concentration of the fuel processing system is estimated based on the determined model of the air processing system.

16. The system according to claim 15, further comprising: include: a pressure controller to control the pressure of hydrogen gas supplied from the fuel storage system to the fuel processing system; A ventilation controller controls the opening and closing of the ventilation valve; as well as A main controller controls the pressure controller and the gas exchange controller so that the hydrogen concentration of the fuel processing system estimated by the hydrogen concentration estimator follows a target hydrogen concentration.

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